Method and device for Overall Temperature Control Close to the Mould Cavity of Temperature-Controlled Shell-Type Moulds, Using Intercommunicating Media in Polyhedral Spaces

Abstract

Method for near-contour surface temperature control of shell-shaped molds (14) with mold rim zones (1), wherein the temperature control of the mold (14) on a near-contour temperature control surface (4) with adjacent, web-like or wall-like separated subareas (4.i) is effected from the respective rear space (3) of the mold rim zones (1) of the mold (14) and/or the respective mold rim zone (1) of the mold (14). The shell-shaped molds (14) are designed in two or more parts with the respective mold rim zones (1). Specifically, the temperature control as cooling in the form of temperature control on the temperature control surface (4) is locally different in subareas (4.i). The temperature control surface (4) is effected in accordance with the temperature ranges of convection, bubble evaporation, partial and/or stable film evaporation of the liquid cooling fluid water.

Claims

1. A method for temperature control of the back of shell-shaped moulds, comprising the steps: a) locally controlling the temperature of a temperature control surface in delimited subareas of said temperature control surface, b) individually controlling the temperature of the delimited subareas of the temperature control surface in terms of time, c) independently controlling the temperature of the delimited subareas of the temperature control surface in process cycles, d) controlling the temperature of the delimited subareas of the temperature control surface via individual activation of a sprinkling volume flow of cooling water, and e) completely covering the delimited subareas with a film via the sprinkling volume flow, wherein the film is continuously renewed.

2. The method according to claim 1, wherein the temperature of the delimited subareas of the temperature control surface is continuously controlled or discontinuously controlled in the form of the sprinkling volume flow of the cooling water.

3. The method according to claim 1, wherein the temperature of the delimited subareas of the temperature control surface is controlled by individual heat transfer in the delimited subareas, wherein the heat transfer is controlled according to heat transfer mechanisms of convection, bubble evaporation, partial film evaporation and stable film evaporation on the temperature control surface, wherein the quantity of cooling medium water is adapted according to said heat transfer mechanisms.

4. The method according to claim 2, wherein temperatures of said heat transfer mechanisms of convection, bubble evaporation, partial film evaporation and stable film evaporation are shifted by adding soluble additives to said cooling water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Several drawings, in which essential features of the invention are presented, are described in more detail below. They display the following:

[0071] FIG. 1 shows a schematic sketch for designing a flat-type near-contour, shell-shaped mould for media communicating with each other in polyhedron-like spaces as a sectional view of a closed mould with two halves of the mould, each with the rim zones of the mould,

[0072] FIG. 2 shows a schematic sketch for the design of a flat-type, near-contour, shell-shaped mould for media communicating with each other in polyhedron-like spaces as a sectional view of a closed mould with two halves of the mould, each with partial areas of the temperature control surfaces on the mould rim zones,

[0073] FIG. 3 shows a top view of the temperature control surface of a mould rim zone with partial areas and separating-passing elements,

[0074] FIG. 4 shows a schematic of a possible control of the temperature of a subarea of the temperature control surface,

[0075] FIG. 5 shows a diagram of a discontinuous activation of the sprinkling volume flow in bar graph,

[0076] FIG. 6 shows a diagram of the continuous heating of a part of the temperature control surface in bar graph,

[0077] FIG. 7A shows a basic curve of the heat transfer coefficient as a function of the wall temperature .sub.o of the temperature control surface when sprinkling with water,

[0078] FIG. 7B shows two selected setpoint temperatures to be controlled on the temperature control surface with the corresponding heat or cooling intensity to be transferred,

[0079] FIG. 8A shows a displacement of the areas of heat transfer when the surface material of the temperature control surface changes due to a desired chemical change or physical coating,

[0080] FIG. 8B shows a displacement of the areas of heat transfer when the surface material of the temperature control surface changes due to an unwanted chemical and/or micro-mechanical change in the surface of the wall material,

[0081] FIG. 9A shows a sectional view of a separating-passing element, incorporated in a mould shell,

[0082] FIG. 9B shows a side view of FIG. 9A of a separating-passing element, incorporated in a mould shell,

[0083] FIG. 10 shows a cross-section through the mould shell with separating-passing elements and sprinkling nozzles applied to the mould shell,

[0084] FIG. 11A shows the sprinkling by means of a sprinkling nozzle of an area that is difficult to overflow on a part of the temperature control surface,

[0085] FIG. 11B shows the side view of FIG. 11A,

[0086] FIG. 12 shows the representation of the change in the heat transfer of the temperature control surface due to its ageing and the associated change in the control of the setpoint temperature of the temperature control surface and

[0087] FIG. 13 shows an orientation option for a controller in the areas of heat transfer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] According to the invention, the new process is used to temperature-control the back surfaces of shell-shaped moulds 14 with mould rim zones 1. These rear surfaces are called temperature control surfaces 4. The temperature control surface 4 is divided into different subareas 4.i. The mould 14 can be two-part or multi-part and thus have several mould rim zones 1, which are temperature-controlled according to this present process. The respective temperature control surface 4 of the mould rim zone 1 can be designed so that it follows the engraving 5 of cavity 2 of mould 14.

[0089] The temperature control surface 4 can be cooled or heated. In principle, the temperature can be controlled by various media in subareas 4.i and their polyhedron-like spaces in the rear chamber 3 of the mould. In FIGS. 1 and 2 this is shown schematically in a sectional view through form tool 14. The temperature control media in the polyhedron-like spaces can communicate with each other via separation-passing elements 10. Depending on the requirements of temperature control and flow control, the individual separating-passing elements 10 are worked into or applied to the temperature control surface 4. This makes it possible to achieve optimum temperature control of the entire temperature control surface. FIGS. 9, 10 and 11 show examples of such separating-passing elements. They are wall-like structures that are flat or wavy, depending on the requirements. For example, they are also dome-shaped in one part or have break-outs 15. They are then adapted in their shape to meet the requirements of the interaction of the temperature control media in neighbouring polyhedron-like spaces. In addition, the separating-passing elements 10 have a discontinuous cross-section, so that on the one hand the distribution and drainage of the water is more reliable and on the other hand the stability is improved. Schematic illustrations are shown in FIGS. 1, 2, 9, 10 and 11A as examples. If, for example, a subarea 4.i of the temperature control surface 4 is overflowed with liquid water, it must be ensured that the entire subarea 4.i is wetted by a water film which is constantly renewed by sprinkling with the cooling medium water in order to make the heat transfer always reproducible in this subarea 4.i. For this purpose, the water must also reach corners and edges on the temperature control surface 4 of the respective subarea. Due to the strongly changing topography of a surface close to the contour, this is often difficult to achieve with walls that resemble a plane. Therefore, the shape of the respective wall-like separating-passing elements 10 must be adapted in such a way that a suitable overflow of water can take place over the entire subarea 4.i. Without water film, this process cannot be carried out according to the mechanisms of heat transfer of liquid water to a hot wall, convection, bubble evaporation, stable and partial film evaporation. Furthermore, the separating-passing elements 10 are of different heights. They are also sprinkled with liquid water or generally by the temperature control fluid during sprinkling, provided this is favourable for overflowing the respective subarea 4.i of the temperature control surface 4. FIG. 10 shows the separating-passing elements 10 applied to the temperature control surface 4 by welding. The separating-passing elements 10 are also provided with openings 15 to ensure an interaction of the media in adjacent polyhedron-like spaces. This is exemplified in FIGS. 9A, 9B and 11A, 11B. In addition to ensuring a good overflow of the temperature control fluid, the separating-passing elements 10 also ensure the stability of the mould rim zone 1. They have a suitable shape and are arranged in a suitable shape on the temperature control surface 4. Accordingly, the separating-passing elements 10 are wall-like structures whose shape and number are specially adapted to their tasks on the temperature control surface 4.

[0090] If the incorporated or applied separating-passing elements 10 are only used for the mechanical stabilization of the mould shell 1 and/or the conduction of fluids on the mould shell 1, these do not necessarily extend directly to the temperature control surface 4 of the mould shell 1. Depending on the requirements, the separating-passing elements 10 have different heights in order to ensure optimum mechanical stability and/or flow channeling.

[0091] As shown in FIG. 2, the rear chamber or temperature chamber 3 can be closed with a housing part, such as an end plate 9, depending on requirements. Devices for temperature control and delimitation of the temperature control surface 4 can be advantageously integrated into the end plate 9, insofar as this is technologically or geometrically advantageous. The end plate 9 can be used to guide and secure supply and return lines for operating the temperature control devices for the temperature control surface 4, as well as supply lines for the sensors. The end plate 9 is made of the same mould material, but can also be made of a different material. It can be made of metal. Depending on the design of the mould 14, the end plate 9 can have a load-bearing or non-load-bearing function. Accordingly, it absorbs forces of the working or forming process. The end plate 9 of the temperature control space 3 can also have the form of an end box. The advantage here is that, in addition to fixing the supply lines and devices for temperature control, the cooling water that accumulates can be well collected and passed on. This end box does not necessarily have to be fixed rigidly in the rear of the mould. However, the end plate 9 must not be in the way of opening the temperature control space 3 to the atmosphere. In the present process there is always a pressure equalisation of the polyhedron-like spaces with the atmosphere. Separating-passing elements 10 can also be arranged on the end plate 9, from where they extend to the temperature control surface 4. According to a specific requirement, the separating-passing elements 10 have direct contact with the temperature control surface 4.

[0092] The additional part of mould 14, next to mould rim zone 1 and temperature chamber 3, is the solid area 8 of mould 14. Forces of the working or forming process are transferred to the solid area 8 via the mould rim zones 1 and the polyhedron-like spaces with their separating-passing elements 10 located on them.

[0093] Various temperature control media can be used for cooling or temperature control of the shell-shaped moulds 14. It is known that for the intensity of cooling of a hot wall with liquid water the heat transfer coefficient depends on the surface temperature .sub.o of the wall. When cooling a mould 14 with liquid water, the heat transfer in this case is strongly dependent on the temperature .sub.o of the temperature control surface 4 or subareas 4.i of the temperature control surface 4. Therefore, the transfer of heat or the cooling intensity can be varied or specifically controlled according to the temperature of the temperature control surface 4 by means of devices for temperature control of the temperature control surface 4.

[0094] When sprinkling a hot wall with water above the burnout temperature .sub.Bo there are basically two mechanisms of heat transfer to the wall. The Leidenfrost temperature or Leidenfrost point of the wall surface plays an important role here, something that has been known for a long time.

[0095] FIG. 7A shows the principle curve of the heat transfer coefficient from the wall temperature .sub.o. The burnout temperature .sub.Bo and the Leidenfrost temperature .sub.Le are shown. From the burnout temperature .sub.Bo to the Leidenfrost temperature .sub.Le the area of partial film evaporation is limited. The heat transfer coefficient rises sharply from the Leidenfrost temperature .sub.Le with falling wall temperature and is at a maximum at the burnout temperature .sub.Bo. With the heat transfer coefficient .sub.max above the Leidenfrost temperature .sub.Le the area of stable film evaporation begins. Above the Leidenfrost temperature .sub.Le the heat transfer coefficient increases only slightly with the temperature, it is almost constant. With the heat transfer coefficient . below the burnout temperature .sub.Bo the area of bubble evaporation of the water on the hot wall begins. If bubble formation on the wall ends at point K, the area of convection of the water on the wall begins.

[0096] In the present invention, all phenomena of heat transfer of water on the hot wall can be used for temperature control of sub-areas 4.i of the temperature control surface 4 with liquid cooling fluid water, namely the areas of stable film evaporation and partial film evaporation at high wall temperature .sub.o up to burnout temperature .sub.Bo. At temperatures lower than the burnout temperature .sub.Bo, the areas of bubble evaporation and convection are used. For example, in section 4.1 of the temperature control surface 4 at temperature , in section 4.2 at temperature and in section 4.3 temperature control can be done at a further temperature . In these cases other heat can be transferred per unit of time or heat intensity, which can be read, for example, from the associated heat transfer coefficients .sub.1 and .sub.2 in FIG. 7B. In principle, it is therefore possible to transfer different types of heat in different subareas 4.i and at different times using the various mechanisms of heat transfer.

[0097] The variables or dependencies of the Leidenfrost point on these variables can be used for cooling or temperature control with the liquid cooling fluid water in a targeted manner. For this purpose, the areas of heat transfer on the temperature control surface 4 and thus the intensity of heat transfer or the heat transfer coefficient can be shifted into a temperature range that is favourable for the process in a targeted manner. For example, the surface of the material of the temperature control surface 4, which can be specifically modified, plays a special role for the Leidenfrost point. The surface can be changed chemically, for example by surface oxidation or similar and physically, for example by evaporation with a substance. As the surface material changes, the interaction of the water with the hot surface and thus the Leidenfrost point and the areas of heat transfer change. This is shown in principle in FIG. 8A. A surface treatment of the temperature control surface 4 or parts of 4.i shifts the heat transfer from the dotted line type to the type with a continuous line with the respective changing heat transfer coefficients and the corresponding wall temperatures .sub.o.

[0098] However, there may also be unwanted changes, e.g. chemical changes and changes in the topography of the wall surface. These can be summarized under the term ageing of the material and in some cases are difficult to calculate. They occur with increasing service life of the tools. These include, for example, corrosion and associated fracturing and washing out in the microscopic range. They occur as a result of the continuous sprinkling cycles of the hot temperature control surface 4 with cold water. Due to ageing, the interaction of the cooling fluid water with the wall or the temperature control surface 4 also changes. This changes the Leidenfrost point and with it the areas of heat transfer. In FIG. 8B, the consequences of the ageing of the surface have been made visible in principle by way of example. The initial surface with .sub.Bo, 1 and .sub.Le, 1 and associated heat transfer coefficients .sub.k,1 and .sub.max,1 changes into the surface with the .sub.Bo, 2 and .sub.Le, 2 and associated heat transfer coefficients .sub.k,2 and .sub.max,2 under ageing.

[0099] The interaction of the water with the hot temperature control surface 4 can also be mechanically influenced, for example by structuring the surface with different cutters. This changes the conditions of the surface's wetting with water. As a result, the Leidenfrost point and the associated areas of heat transfer change.

[0100] In the temperature range of partial film evaporation, more intensive and also variable cooling is possible compared to that of stable film evaporation, depending on the temperature of the wall. In contrast to the area of stable film evaporation, where the transferable heat changes only slightly with the temperature of the wall surface, different heat can be transferred in the temperature range of partial film evaporation depending on the temperature of the surface of the subarea of the temperature control surface 4.i. In the area of stable film evaporation, the transferred heat is usually almost constant and independent of the surface temperature , because the steam film formed prevents this. This can also be used in a targeted manner. The control mechanism can be somewhat slower here due to the low temperature dependence.

[0101] There are various temperature control options. If the temperature control surface 4 is cooled with liquid cooling fluid water, sprinkling nozzles 6 are used for its area distribution in accordance with the invention. This invention is a sprinkling cooling system. The sprinkling nozzle 6 is a two-dimensional sprinkling device for liquid cooling fluid water, without using a carrier gas for the cooling fluid. It is characteristic that through the sprinkling nozzle 6 liquid cooling fluid splits water into drops and distributes it in the surrounding gas, which is generally air. The drop size generated via sprinkling nozzle 6 depends on the operating parameters water pressure and water temperature and on the geometry of the sprinkling nozzle 6. The way the nozzle is operated also affects the areas of heat transfer. The basic geometric shape of the drop collective created by the sprinkling nozzle 6 is a drop, sprinkling or spray cone. It is important that the droplets of the spray cone are distributed over the area of the incident geometry of the temperature control surface 4 so that they form a uniform continuous liquid film on it, independent of the respective mechanism of heat transfer. Due to the geometric design of the sprinkling nozzle 6, the distribution can be varied from the geometric shape of a sprinkling cone. On a flat temperature control surface 4 the drops of the sprinkling cone would be scattered, e.g. in the form of a circular disc or an ellipse. Depending on the design of the sprinkling nozzle 6, other geometric forms of sprinkling are also possible. In any case, the temperature control surface 4 of the mould rim zone 1 is wetted over the entire surface with the drop collective of the sprinkling nozzle 6. By selecting the operating parameters of the sprinkling nozzle 6 or by its geometric shape, the sprinkling density or water impact density can be set on the temperature control surface 4 of the mould rim zone 1. Sprinkling density is the amount of water applied to the surface per unit area and time. The density of water impact can influence the Leidenfrost point and the associated areas of heat transfer. The design of sprinkling with the liquid cooling fluid water depends on the conditions and requirements of the sprinkling of the temperature control surface 4 or subarea 4.i of the temperature control surface 4. For example, several sprinkling nozzles 6 can be integrated in an end plate 9 or another mounting device and used for sprinkling.

[0102] If, for example, water and sprinkling of the temperature control surface 4 are to be controlled by this water in order to use the mentioned mechanisms of heat transfer, the vertical alignment of the temperature control surface 4, and thus of the tool itself, is required. The water must be able to drain off after sprinkling of the hot temperature control surface 4 or section 4.i in order to interrupt the heat transfer. For this purpose, the separating-passing elements 10 are designed accordingly, so that the cooling fluid water can flow off without any problems.

[0103] However, modifications may also occur if the vertical alignment of subarea 4.i is not possible, for example the rapid extraction of water accumulations in cavities of horizontally aligned cores of the tool is also possible and, if applicable, necessary. Important for the present process is the wetting of the temperature control surface 4 with a water film, which must be continuously renewed in order to make the intended optimal heat transfer reproducible according to the mentioned heat transfer mechanisms, such as partial film evaporation and the other mentioned heat transfer mechanisms.

[0104] By controlling the temperature of the temperature control surface 4, the local cooling intensity or the local transfer of heat to the mould rim zone 1 is influenced. The temperature of the temperature control surface 4 has the largest influence on the transmission of cooling capacity. This means that the heat transfer coefficient and thus the intensity and time of the heat transfer are specifically influenced by the control to the target temperature of the surface of the subarea 4.i. If the surface is adjusted to the target temperature .sub.1 in a subarea 4.i+1, more heat can be transferred in the same time than if .sub.2 is adjusted to the surface temperature in a subarea 4.i+1, see FIG. 7B. This means that the cooling of the workpiece can be controlled specifically via the temperature control of the subarea surfaces 4.i of the temperature control surface 4. In other words, the heat flow from the workpiece to the engraving can be controlled specifically via the temperature control of the subarea surfaces 4.i of the temperature control surface 4. Due to the required contour proximity of the present method, the time required for the effect of the heat flows in the individual subareas 4.i is short compared to conventional methods. In conventional moulds, large material thicknesses of the tool would have to be overcome and thus long times for the effect of the control described would have to be taken into account. These long times are generally not available in the production of castings. In addition, considerable transverse conduction of the heat in the tool would have to be expected, which would call into question or make impossible the locally limited transfer of heat. In addition, the heat transfer via the effect on the heat transfer coefficient of the subarea has a large scope in the present procedure. If, for example, the material properties in a certain subarea 4.i do not meet the technological requirements, the heat transfer in that subarea can be adapted. This ensures that a tool can be run with different parameters, even after production, and can be adjusted to different requirements for the part or workpiece. The new production of the mould itself is not necessary.

[0105] This concerns, among other things, the difficult filling of thin walls on large workpieces, such as structural components, which can often be difficult to influence from the design aspect in advance. The change in the grain size of some areas of the workpiece can also be influenced by changing the heat flow.

[0106] The separating-passing elements 10 of the polyhedron-like spaces also enable an almost continuous transfer of heat between the polyhedron-like spaces at the desired points on the temperature control surface, thus avoiding abrupt transition behaviour of the temperature control at the separating-passing elements 10. This is possible by designing the interaction of the temperature control medium water between the adjacent polyhedron-like spaces or via their separating-passing elements 10. The interaction of the media between the polyhedron-like spaces can be designed within wide limits by means of openings 15 or heights of the individual separating-passing elements 10 or intentional overflow of separating-passing elements.

[0107] The interaction of the temperature control medium with the subarea surface 4.i can be stopped at any time. If this is desired, the heat transfer can be interrupted almost instantly. By switching the temperature control medium on or off, the thermal interaction with the temperature control surface 4 is started or interrupted in a targeted manner. For example, the water is shut off from the nozzle and runs off immediately from the temperature control surface 4, or a subarea 4.i, and the correspondingly designed separating-passing elements 10.

[0108] The possibility of different temperature controls in each subarea 4.i also means that different types of media can be used. The prerequisite is the setting of the corresponding interaction of the media in adjacent polyhedral rooms. If, for example, air is used in a partial area for temperature control and liquid water in an adjacent area, the interaction of the media in adjacent polyhedron-like spaces should be reduced. This is possible by designing the corresponding separating-passing elements 10. Important is the good wetting of the temperature control surface 4 in the case of the medium water and the good flow control in both cases.

[0109] Good flow control in the respective subarea 4.i is often only possible via suitable opening of the separating-passing elements 10. Because of the very changeable topography and geometry of the temperature control surface 4, a general solution for flow control of the temperature control fluids is not possible. Furthermore, the separating-passing elements 10 are variable in a wide range, but edges and corners in the area of the seating of the front side of the separating-passing elements 10 on the temperature control surface 4 are sometimes unavoidable. In order to form an even water film or to achieve an even wetting of the surface with water, the partial opening of the separating-passing elements 10 is necessary. FIG. 11 shows an example of the necessity of opening the separating-passing element at its end face to the temperature control surface 4 in an area a which is difficult to overflow. Due to the strongly changing topography, i.e. the geometrically strong change in the height of the surface in the narrowly limited area a of the temperature control surface, overflow in this area a or flow control on the temperature control surface in area a by means of sprinkling cooling is very difficult. For this reason, a small limited gap is worked into the front side of the separating-passing element, thus ensuring good overflow in area a. Wetting with a water film is now also possible in this area a. This is necessary because in the case of temperature control of subarea 4.i with water, all areas of the surface of subarea 4.i must be overflowed with a water film, as this is the only way to ensure the controlled heat transfer of water to the hot wall. The design of the temperature control surface 4 with suitable separating-passing elements 10 is therefore very important for this process. It is not absolutely necessary to provide the separating-passing element 10 in an area with a breakthrough, for example. A streamlined design of the separating-passing element 10, for example the spherical bulging in the area of the end faces facing the temperature control surface 4, can also lead to the same goal as shown as an example in FIG. 10 with the second separating-passing element 10 shown from the right. In the case of temperature control or cooling with water, it is a prerequisite for the transfer of heat in accordance with the various mechanisms of heat transfer.

[0110] The purpose of the flow control is to ensure uniform wetting of the respective subarea of the temperature control surface 4.i, whereby the resulting liquid film must be continuously replaced by the sprinkling in order to make the heat transfer reproducible. If not wetted everywhere, or if the water film cannot renew itself continuously, this heat transfer by means of water cannot take place in the non-wetted area. The heat transfer would not be reproducible or not possible or insufficiently possible in areas which are difficult to access or not accessible to the flow.

[0111] Changing temperature control with different temperature control media on one and the same subarea 4.i is also possible: Thus, it can be tempered or cooled first with a gaseous medium and then with liquid water. This is made possible by the option of shutting down the respective temperature control medium: After shut-down, it no longer interacts with the temperature control surface of the respective sub-area, because it is no longer there due to shut-down. Water flows off the vertical temperature control surface 4 or subarea 4.i instantly. If a device for the supply of another medium is installed, e.g. for gaseous media, then this can subsequently be used for the same subarea.

[0112] In principle, solid media such as ice and mixtures of solid and liquid media such as ice water or solid and gaseous media such as dry ice air are also suitable for cooling and are used for this purpose. However, care must be taken to ensure that the temperature control surface 4 is not inadvertently chemically modified, coated or added and stable temperature control is thus prevented. Furthermore, it is possible with solid temperature control media that these also remain on the temperature control surface after the medium has been switched off, thus allowing a further interaction with it for a limited period of time.

[0113] Heat pipes or two-phase thermal siphons, can also be used for the temperature control of sections 4.i of the temperature control surface 4. They must be arranged in such a way that they can interact thermally with sub-area 4.i of the temperature control surface 4 in their characteristic manner. Cooling by means of the aforementioned heat pipes isdue to the connection based on the designregarded as contact temperature control, whereby with an appropriate arrangement the contact temperature control also has the function of fluid cooling. In principle, electrical devices such as Peltier elements or others can also be used for contact cooling of the temperature control surface 4 or parts of 4.i. They are brought into solid contact with the respective area of the temperature control surface 4.

[0114] External heating via the temperature control surface 4 of the mould rim zone 1 or of subareas 4.i of the mould rim zone 1 is achieved by introducing external thermal energy via external heating media 13. Heating can be realised via radiation, flow or contact with external heating media. By the suitable arrangement of heating media 13, such as burners, blowers, radiators or electric heating elements on, in, and below the temperature control surface 4, parts of the temperature control surfaces 4 of the mould rim zones 1 are heated externally from the rear chamber 3 of the mould 14. For example, burners with suitable output and at a suitable distance behind the temperature control surface 4 are positioned. Electrical heating elements can be arranged directly under, on and in front of the temperature control surface 4 of a corresponding section 4.i of the temperature control surface 4. External heating of subareas 4.i is advantageous, for example, in the case of processing thermoplastic materials in injection moulding, in order to be able to machine the workpiece. The external heating from the rear space 3 of the mould rim zone 1 represents a uniform heating of the temperature control surface 4 or of partial areas 4.i of the temperature control surface 4. In addition, there is another advantage of the present procedure: It can be tempered independently of the process cycle of the forming of the workpiece, i.e. also during the opening times of the mould and during the removal of the workpiece. Even before, during or after filling cavity 2, it is possible that a separate temperature control regime runs in various subareas 4.i of the temperature control surface 4 in order to influence the required target conditions. The temperature control regime is understood in such a way that thermal energy can be transferred to the temperature control surface 4 in different intensities depending on the time: This allows external heating or cooling with the technologically required intensity. The sequence of the thermal treatment steps of the mould rim zone 1 is adjustable according to technological requirements. The necessary devices for heat transfer shall be arranged for this purpose.

[0115] Depending on technological requirements, for example to adjust certain material properties of the casting, different temperature control regimes of cooling and heating according to the invention can be carried out in the subareas 4.i of the temperature control surface 4. For this purpose, the criteria for the necessity of controlling the temperature control devices can already be clearly defined at the design stage. This significantly increases the ability to plan the process, as it enables simulations, for example, to be carried out in advance.

[0116] The temperature control regime or the control to certain temperatures of the subareas of the temperature control surface 4 can in principle be changed from process cycle to process cycle. The different temperature control options in subareas 4.i therefore also make it possible to optimize the temperature control of the entire mould rim zone 1 to different desired thermal target states of the mould rime zone 1 or to control the transfer of the cooling intensity or heat from the workpiece via the engraving to the temperature control surface 4 of the mould rim zone 1. Due to the possibility of realizing different temperature controls or temperature control regimes, the way to optimal cast parts can be found cost-effectively by means of previous simulations, while protecting the mould 14, at minimum process time.

[0117] Finally, the temperature control conditions can still be further adjusted in the practical running-in of the new mould 14 so that optimum casting and solidification conditions for the casting can be achieved. For example, the setpoint temperature can be changed in a subarea 4.i of the temperature control surface 4. When cooling with liquid water and, e.g. in the area of partial film evaporation, the intensity or the heat transfer coefficient also changes due to the change in the target temperature for the subarea. Due to the intensity or the transferred heat per time, the time for setting the setpoint temperature changes in subarea 4.i. With the process according to the invention, it is therefore possible to exert variable influence on the mould tool 14 and the workpiece or the moulding while the practical casting operation is still in progress.

[0118] This is of special importance: In the case of the tool steels currently used for casting moulds, constant contact of the temperature control surface 4 with cold water caused by the process is to be expected in the course of operation, if no precautions have been taken against ageing, such as a coating or similar. It is therefore possible to counteract the ageing of this surface by changing the selection of the desired surface temperature of the subarea 4.i. Thus, only the time dependence for the heat transfer (intensity) of the changed surface is to be known and the temperature control of the temperature control surface in subarea 4.i or several subareas 4.i is to be adjusted accordingly. This is shown symbolically in FIG. 12: The dashed curve symbolizes the initial surface of section 4.i of the temperature control surface 4. It is moved to the right due to ageing. This means that the Leidenfrost point and the areas of heat transfer shift to higher wall temperatures. If the temperature controller would continue to operate at the same setpoint temperature .sub.Wall condition 1 of the subarea, the different heat transfer coefficients would extract much more heat from the wall per unit of time. This means that the aged wall would cool down faster because at the same set temperature .sub.Wall condition 1 there is a higher heat transfer coefficient . The temperature control mechanism would have to operate at a higher cooling intensity. In fast-moving cooling processes, as in the present process, a higher cooling intensity can mean that this doubles due to the strong temperature dependence of the heat transfer coefficient . This is easily possible when in the area of partial heat transfer and there is a strong dependence of the heat transfer coefficient on the temperature of the wall surface. This can be a source of instability for the temperature controller. It is therefore more advantageous to lower the target temperature of the surface from the temperature .sub.Wall condition 1 to the temperature .sub.Wall condition 2. This means that now, in the case of the aged surface, the temperature control surface 4 is operated at a lower wall temperature .sub.o, but the same heat is extracted as before in the non-aged case. The stability of the production process can thus be maintained. One would also find oneself in a stable area of the process because with increasing wall temperature .sub.o in the area of bubble evaporation the intensity of heat transfer increases with the wall temperature .sub.o. The heat transfer mechanism of bubble evaporation counteracts the rise in wall temperature by increasing the cooling intensity of the water against the wall.

[0119] These ageing constraints can already be influenced during the design of the casting tools by including the ageing of the wall material in the control mechanism. Such material changes can, for example, be determined in advance of the design and the associated heat transfer coefficient values a determined. If the surface material of the temperature control surface 4 of section 4.i ages gradually during the production process, the control behaviour of the temperature controller is adjusted step by step.

[0120] For example, it is possible to sprinkle or cool the respective subarea 4.i of the temperature control surface 4 with an almost constant intensity when setting the desired temperature. One temperature control task, for example, is to cool a certain section 4.i of the mould rim zone 1 with an almost constant heat transfer coefficient .sub.i because a certain material property of the workpiece is required. Since the heat transfer coefficient .sub.i depends on the surface temperature of the wall material, the corresponding subarea 4.i of the temperature control surface 4 must be cooled at a certain set temperature or within a narrow temperature range of the set temperature. This can be achieved by selectively controlling the water supply to sprinkling nozzle 6 of this section 4.i of the temperature control surface 4 via a valve 11, for example via a solenoid valve 11 as shown in FIG. 4.

[0121] For this purpose it is possible to record the temperatures at one or more suitable measuring points in subarea 4.i of the temperature control surface 4 using sensors 12 such as temperature sensors 12. In FIG. 4 only one temperature sensor 12 is shown as an example. The behaviour to be derived for the control or controlled system can, for example, be based on several temperature measuring points with continuous calculation of a different variable. The control behaviour of the temperature controller or the controlled system can be designed to be stable on the basis of the calculated course of this variable. These sensors 12 can be suitably mounted on and below the surface to measure good and representative values for the temperature or the temperature distribution of subarea 4.i of the temperature control surface 4. Via a temperature controller 7, the opening time t.sub.i of valve 11 or the degree of opening of valve 11 is derived and controlled according to the signal strength of sensor(s) 12 and its deviation from one or more temperature setpoints T.sub.S of the temperature of the measuring points. FIG. 5 shows schematically and by way of example a discontinuous control of the water volume flow V through the temporary opening and closing of valve 11, for example, using a solenoid valve 11 with only one opening position. The times t.sub.0 and t.sub.End mark the start and end of the temperature control in the process cycle. Depending on the desired cooling intensity, the temperature is controlled to a certain target surface temperature of this subarea 4.i of the temperature control surface 4 of the mould rim zone 1.

[0122] The heat transfer processes in the corresponding areas of heat transfer, such as partial film evaporation and others, are associated with a rapid reduction in the surface temperature of the wall. The subsequent heat conduction inside the tool rim zone 1 depends on the tool material. With the tool steels currently used for casting moulds, the heat conduction of the tool material is usually lower than the very rapid reduction of the surface temperature due to sprinkling with water. Therefore, the processes of heat transfer of water to the hot wall and that of heat conduction inside the wall must be taken into account and coordinated.

[0123] Temperature sensors 12 with low inertia or fast response time are therefore required. This is important, because due to the mechanisms of heat transfer .sub.o heat is transferred to the wall in different ways depending on the surface temperature. The entire controlled system consisting of measuring elements and final control elements must be able to react in its control behaviour according to the areas of heat transfer and be programmable accordingly. A stable control behaviour must be ensured in order to be able to use the advantages of the heat transfer of liquid water to the hot temperature control surface 4 in the individual subareas 4.i. This means that the regulation of the temperature in the individual areas of heat transfer with their different intensities of heat transfer must be able to be made stable by one or more controllers in order to adjust to the required target temperatures of the subareas 4.i.

[0124] The results of thermal simulations can be used to select suitable components for the controlled system. They provide information on the speed of the heat transfer processes taking place under the given flow conditions of water or the respective temperature control fluids used and the resulting requirements on the controlled system.

[0125] Furthermore, the opposite process of heating the wall from the side of the moulded part or workpiece via the engraving must be taken into account. This process can hardly be measured directly on the surface of the tool to the melt used via sensors 12. In addition, the melt solidifies, changing the heat transfer of the moulded part to the mould from the engraving side. Due to the low wall thickness of the workpieces, the solidification processes are also fast. Again, the heat transfer coefficients of the moulding depend on the aggregate state and its temperature . In addition, the heat transfer coefficients of the melt to the steel surface in die-casting depend on the pressure. The solidification process can often only be determined by simulations in which the heat transfer coefficients can be varied within plausible limits. The data obtained can thus be evaluated or used to select a controlled system for the temperature control surface 4.

[0126] Furthermore, control scenarios for an ageing of the temperature control surface 4 or for an intentional change of the temperature control surface 4 must be stored in different subareas 4.i for the control behaviour of the controlled system. All desired variable changes that are relevant for a shift of the Leidenfrost point and the areas of heat transfer must also be available as scenarios for the controlled system and be controllable by it. It must be possible to fall back on it.

[0127] Furthermore, the control must also be able to counteract unknown, acting disturbances which influence their stability. These disturbances are, for example, unforeseeable influences during continuous casting operation, such as different casting breaks, different water temperatures of the cooling, cooling water qualities, temperature influences in the foundry, different types of release agent application to the engraving before the casting cycle, varying melt temperature, blowing out the engraving to remove casting residues, occupancy of the temperature control surface 4. Some of these disturbances affect the Leidenfrost temperature .sub.Le, others affect the controlled system in other ways. Therefore, the stability of the temperature control of the temperature control surface 4 or the subareas 4.i and the control to the specified and changing target temperatures is important for optimum heat transfer during the casting process.

[0128] If other temperature control media than water are used, their effectiveness can also be influenced by disturbances. Here, too, the controlled system must be able to counteract the disturbances in a stable manner.

[0129] Then suitable components of the controlled system can be assembled and the control behaviour of the entire controlled system on the side of the temperature control surface 4 or its subareas 4.i can be determined and optimized by simulating the known influences and random influence of disturbances.

[0130] An important question is the orientation of the controlled system. This means the question of the range of heat transfer of the water to the temperature control surface 4, in which the subarea 4.i of the temperature control surface 4 is currently located, if the control has come out of the stable range. This can happen if the controlled system reacts too slowly to an external influence or is too slow to control. This can happen due to ageing of the surface or due to environmental influences on the temperature control surface 4. The areas of heat transfer are shifted. It concerns the measures of regulation for finding back into the stable area of temperature control, from an unwanted area into the intended heat transfer of water to the hot surface. What does an optimal control in order to return to the set temperature look like? An orientation routine or a variable for orientation of the controlled system must be carried along which allows it to return to the desired area of heat transfer. A constant adjustment must be made for orientation of the controlled system.

[0131] Furthermore, a delay of the measured values for the actual change of the measured variable must be expected and these must be included in the routines for the controlled system. For the temperature control process on the temperature control surface 4, a rapid change in the measured variable must be measured and evaluated using sensors with low inertia. Likewise, measured values are to be made continuously directly below the measuring point of the surface, i.e. in the mould rim zone 1. The appropriate control routine must always be derived from this.

[0132] If the temperature is measured with a sensor 12, its change directly at the temperature control surface 4 is faster than within the mould rim zone 1, which results from the heat conduction of the material or the physical material values of the mould rim zone 1. In addition, they are delayed inside the mould rim zone 1. From the temperature curves, the heat flux densities can be calculated as a function of the temperatures. The possible orientation for determining the orientation of the controlled system according to the areas of heat transfer is shown in FIG. 13 as an example for the case of surface sprinkling. The heat flux density q in watts/m.sup.2 calculated from the temperature curve of at least 2 temperature measuring points .sub.O on the surface and below in their principal dependence on the surface temperature .sub.O is shown. If the temperature is .sub.1, the rise to the curve is negative. The increase is to be understood as a change in the heat flux density q after the temperature at a given point on the surface. To the left of the Leidenfrost temperature .sub.Le the temperature decreases with rising heat flux density q. This is principally the same with temperature .sub.2 but the amount of the rise is different. The sign of the increase principally does not change up to the burnout point. When being to the left of the burnout point, i.e. in the area of bubble evaporation, the rises are positive depending on the surface temperature .sub.o, but their amounts also differ, the conditions at temperature .sub.3 and .sub.4 must be compared. At the curve, a rise is drawing symbolically for the point .sub.4, q.sub.4. By continuously determining the temperatures at and directly below the surface, orientation within the areas of heat transfer can be carried out, for example, with the rises to the q- curve. The routines for the individual areas of heat transfer will be different. If, for example, one is to the right of the Leidenfrost point in the area of stable film evaporation, the increases in heat flux density after the temperature are much lower to constant. The control behaviour for the individual areas of heat transfer will therefore be different and must be adapted accordingly. Stable operation of the control system must be able to be achieved again and again in the event of disturbances. The constant orientation of the controlled system therefore serves to take measures to remain within the stable range of control of the setpoint value or to return to it.

[0133] Furthermore, the control behaviour to be adjusted depends on the surfaces used or their materials and their ageing. This is also important for the controlled system and the stable control for dissipating heat from the workpiece. For example, the temperature curves on and below the surface differ if the areas of heat transfer shift with the ageing of the temperature control surface 4.

[0134] In principle, orientation in the areas of heat transfer is also possible with other sensors 12 than temperature sensors 12. A sensor system that can be assigned to the individual areas must be selected. The change in measured value in the respective range should also be large enough for an evaluation.

[0135] In addition, process-accompanying thermal, etc. simulations are carried out to ensure the plausibility of the control behaviour to be derived and the stability of the control.

[0136] The duration and intensity of cooling of the mould rim zone 1 influence the conditions of the workpiece. Material accumulations of the workpiece, such as thick workpiece walls, can be cooled with particularly high intensity, for example. These include, for example, areas of overflows, which generally have thick walls. At thin workpiece areas, the temperature control surface 4 is cooled with lower intensity. It may be technologically necessary to also slightly heat subareas with low intensity externally. A temperature control task can be to temperature-control a subarea 4.i of the temperature control surface 4 for a certain period of time at a constant thermal heating rate h/t of an external heater (FIG. 6). The sub-area 4.i must therefore be heated during the period t.sub.i. The times t.sub.0 and t.sub.End mark the start and end of the heating process. The temperature of section 4.i of the temperature control surface 4 changes constantly and the temperature of the engraving changes accordingly. After the casting has been removed, the result of the temperature control regime can be viewed and evaluated advantageously on the engraving 5 using an infrared camera. However, other sensors 12 can also be inserted into the mould 14 (not shown), which allow a continuous evaluation during the closed mould 14. According to the measurement results, the temperature control regime is changed or optimized in certain subareas 4.i. FIG. 7 (below) shows two setpoint temperatures in two subareas of the temperature control surface 4 for illustration purposes. With the control to these wall temperatures .sub.1 and .sub.2 in the subareas 4.i of the temperature control surface 4, corresponding heating and cooling intensities, for example, according to .sub.1 and .sub.2, are transferred to these subareas 4.i of the temperature control surface 4. A different heat transfer can take place in each subarea 4.i of the temperature control surface 4. This means that a different heat transfer coefficient can be assigned to each sub-area 4.i of the temperature control surface 4 according to FIG. 3.

[0137] For example, it is necessary to meet certain temperature specifications for cooling in certain subareas 4.i. It may be necessary to cool certain areas 4.i of the temperature control surface 4 to a greater extent in order to set material properties such as a certain mean dendrite arm distance in the workpiece in order to achieve a special strength of the workpiece. Furthermore, if applicable, it is necessary to set a high cooling intensity locally or to cool with a high heat transfer coefficient in order to push back the porosity from the area near the wall of the workpiece and to enable subsequent workpiece treatment such as welding or surface finishing.

[0138] External heating may be required for sensitive areas of the mould rim zones 1 in which, for example, cold running or streaking of the workpiece must be expected during casting. For this purpose, for example, it is necessary to slightly heat or cool the mould wall at some points in order to eliminate the defect pattern. Influencing such changes is possible with the method according to the invention. A temperature control regime with different types of temperature control in a specific subarea 4.i can also be used. First, for example, the mould is slightly heated to improve filling and then cooled to improve solidification. For this purpose, both external heating and cooling elements are provided for the corresponding subareas 4.i of the temperature control surface 4. For example, an external heating treatment in a subarea 4.i of the temperature control surface 4 and subsequently a cooling treatment with the cooling medium water in subarea 4.i will take place for a limited time. In another subarea 4.i+n adjacent to subarea 4.i, for example, cold compressed air is used for cooling. This ensures that a uniform final cooling temperature is achieved based on different high range temperatures . The cooling processes can be applied simultaneously in adjacent subareas 4.i of the temperature control surface 4, without mutual interference. Therefore, different temperature control regimes can be applied to the temperature control surface 4.

[0139] If, for example, a temperature dependence or a temperature gradient is to be produced on the engraving 5, it may be advantageous to thermally treat certain tool areas separately from the rear space 3 by means of additional external thermal energy, while cooling other subareas 4.i temperature control surface 4. Extensive structural castings often have thin-walled areas in which rapid solidification and inadequate mould filling can be expected. An additional introduction of external thermal energy can be useful for the mould filling process or may be the only way to achieve complete mould filling. After filling the mould, the melt should solidify in a direction so that there is not enough shrinkage porosity in the casting.

[0140] The build-up of lateral thermal-mechanical stresses on the engraving 5, which often occur due to unfavourable temperature distribution, is countered by setting a suitable temperature distribution. For example, tensile stresses would result from notches in engraving 5 which are geometrically unfavourably located but required on the workpiece side. These notches often represent a centre of elevated temperature, also called hot spot. They cool down more slowly than the surrounding areas. This uneven cooling causes tensile stresses which are often reduced by cracks in the notch base. The temperature behaviour in these areas can be effectively controlled by local temperature control according to the invention. This means that areas in the wider vicinity of the notch can be cooled less than the potential crack area in the notch. This directly influences the extension of the service life of the moulds 14.

[0141] Another common defect on the engraving 5 of die-casting tools is the occurrence of fire crack networks. They are formed with increasing age of the mould 14 as a result of the classic atomisation of a release agent/water mixture onto the hot engraving 5 after casting removal. The subsequent casting of the hot melt requires the shock-like heating of the engraving 5. In the casting cycles, therefore, strong tensile and compressive stresses alternate continuously due to the thermal alternating shock stress on the engraving 5. Through the process according to the invention, cooling takes place in a mild form from the rear space 3 of the mould via the temperature control surface 4 there. It is not necessary to apply a mixture of release agent and water to the engraving 5, but only a release agent concentrate in the form of a short aerosol spray dosage, powder or similar. Through the process according to the invention this error pattern can be countered by saving the classic process step of shock cooling of engraving 5. This is why the process according to the invention extends the service life of the moulds.

[0142] In addition to temperature control according to the invention, mould filling can be additionally supported before casting by evacuation of the mould or prior removal of oxygen if increased oxide formation must be expected. It is known that partial oxidation of the melt changes the viscosity in areas where oxides occur.

[0143] The temperature control regime of mould 14 runs according to the inventive process independent of the casting and opening times of mould 14 and the removal of the workpiece. It can be optimally influenced at any time on technological requirements of the process regarding intensity and duration of the temperature control. Therefore, all areas of the temperature control surface 4 can be controlled to their optimum temperature control regime or target temperature . If it is appropriate, the temperature control regime can be changed. In the case of cooling via sprinkling cooling of certain areas, an optimum amount of water can therefore be sprinkled. Greater cooling would impair the mould temperature control for a desired design of the mould filling and the properties of the casting. The amount of water can thus be optimally maintained. If possible, with a high heat transfer coefficient .sub.i of the respective subarea 4.i, sprinkling is possible, whereby the control of the surface temperature of the respective subarea 4.i of the temperature control surface 4 towards the corresponding target temperature takes place. For these reasons, considerable cost and time savings continue to be achieved compared to conventional cooling. On the other hand, a gentle heat transfer can also be selected by controlling a corresponding temperature of the temperature control surface 4, which corresponds to a lower heat transfer coefficient .sub.i or a low transferable heat quantity, for example for sensitive areas of the workpiece. Here, for example, temperature control can be carried out gently with cold compressed air. The temperature control regime can be optimally adapted to the technological objectives with the process according to the invention. Target values include, for example, minimum process cycle times, mechanical properties of the workpiece and protection of the mould 14.

[0144] The type of temperature control according to the invention does not take place in channels, but represents a flat-type open temperature control of the rear space 3 of the mould 14. This is the only way to react to the usual sudden temperature increases or heat flows from the forming process into the mould rim zone 1 with stable temperature control of subareas 4.i of the temperature control surface. In the case of classic open channel cooling with water, the sudden increase in heat flow from the mould cavity during the moulding process can cause the temperature of the channel wall to rise sharply. Depending on the temperature of the channel wall, the corresponding mechanism of heat transfer will adjust to the coolant water. There is only a small optimization potential for an optimal use of coolant, because it flows or it is stopped. Sudden removal of the current temperature control medium or replacement by others is generally not possible. A quick reaction of the temperature control to sudden heat flows is therefore not possible. In the case of the classic closed channel cooling with water, a sudden high heat input would lead to a pressure-superimposed temperature increase, and the system pressure of the cooling would increase strongly locally. This means the opening of safety valves when a critical pressure is reached in the cooling system. Here, too, the stable control of cooling is excluded. Since the process according to the invention is an open-pressure cooling system, there is no increase in pressure in the cooling water system: The pressure compensation to the ambient conditions always takes place.

[0145] Open cooling is fundamental for the process, otherwise it cannot run in a controlled manner. Under pressure, a closed system would shift the Leidenfrost point. Consequently, the areas of heat transfer would change. The Leidenfrost point depends on the pressure presently in the system. In a closed system it would change rapidly with a sudden strong flow of heat from the hot workpiece. The pressure increase would be caused by a temperature overlay with the water, resulting in poor to impossible control.

[0146] In the present process, the pressure in the rear space 3 of the shell-shaped mould can assume at most that of the environment. By suitable temperature control of the respective subarea 4.i to a setpoint temperature or a temperature distribution in subarea 4.i, rapid cooling of the temperature control surface 4 will take place as long as it is sprinkled or cooled in accordance with the invention. The selected temperature control regime allows an early or suitable reaction to increased heat flows.

[0147] For the production of a mould 14, a semi-finished product can be processed, which was produced, for example, in a preceding manufacturing process by means of forming and heat treatment etc. The classic forged steels used for die-casting die construction can also be used in the case of the process according to the invention. The machining operations for the production of the temperature control surfaces 4 of the mould rim zone 1 from rear space 3 are similar to those required for the machining of engraving 5. Therefore, the classical machining tools for mould construction can also be used for machining the temperature control surfaces 4 of the process according to the invention.

[0148] However, the moulds 14 according to the invention with mould rim zones 1 can also be produced in an original mould casting process. Production via the original mould process with possible subsequent heat treatment may be possible, provided that the mechanical properties of the mould material, such as hardness, tensile strength and grain size, are sufficient for the intended mould process. If generative processes or 3D processes can be used to produce the entire tool on a larger scale, it is conceivable to produce the entire tool with these processes.

[0149] Depending on the technological requirements and the type of temperature control media used, it is necessary to condition the temperature control surface 4 in order to achieve optimum temperature control surfaces 4. Conditioning may be necessary due to the intended use of the mould 14, material properties of the produced workpiece or similar. If, for example, sprinkling cooling is used for cooling, the Leidenfrost point of the temperature control surface 4 of mould 14 must be observed. It depends on the chemical composition of the temperature control surface 4. According to the invention, the Leidenfrost point can be influenced by coating the temperature control surface 4 of mould 14. With it, the other areas of heat transfer change. This can be done by chemical coating, e.g. chemical copper plating or physical coating, e.g. by precipitation of a vapour. Coating is applied directly to the temperature control surface 4. Coating can also be worked into the temperature control surface 4. Depending on the choice of coating of the temperature control surface 4, the Leidenfrost point and the areas of heat transfer are shifted to higher or lower temperatures. This is advantageous, for example, if a high cooling capacity is to be transferred to the mould rim zone 1 at a high temperature level. It can also be advantageous to extend the service life of mould 14 if the cooling temperature of mould rim zone 1 is not to be lowered too much after the respective mould cycle. In different subareas 4.i of the temperature control surface 4 the coating can be different.

[0150] Furthermore, the Leidenfrost point of pure liquid cooling fluid water can be changed by soluble additives to the cooling fluid for the given temperature control surface 4 of the mould rim zones 1. Similar to the case of the surface coating, the Leidenfrost point can be shifted to a different temperature . The interaction of the water with the surface is changed and the Leidenfrost point and the areas of heat transfer shift. In different subareas 4.i of the temperature control surface 4, cooling can be carried out with water containing various chemical additives. For example, water-soluble polymers are added to the water. The advantage of using water with the dissolved polymers is that adaptable contact of the water with the temperature control surface 4 and thus a changed heat dissipation or a displacement of the areas of heat transfer is made possible.

[0151] Preferably demineralized water is used for sprinkling of the temperature control surface. Normal tap water always contains minerals in dissolved form, which can be deposited on the temperature control surface 4 when the cooling water is heated, as the water is heated up to 100 C. when cooling. If these minerals are deposited, this leads to a layer on the temperature control surface 4, which influences the heat transfer and the Leidenfrost temperature .sub.Le. This leads to a gradual change in the areas of heat transfer. However, the use of tap water is also possible. This requires additives that bind the minerals. In addition, additives can be used in both variants to prevent corrosion of the temperature control surface 4.

[0152] According to the invention, moulds already in use which have a cooling system of a different type than the cooling system according to the invention can be equipped with the process according to the invention or in part. This is possible if reworking of the rear space 3 of the classic mould 14 allows it. For example, parts of a classically cooled mould 14 can be equipped with the process according to the invention if, for example, streaking and cold running of a workpiece is to be prevented.

LIST OF REFERENCE NUMERALS

[0153] 1Mould rim zone [0154] 2Cavity [0155] 3Rear space, temperature control space [0156] 4Temperature control surface [0157] 4.i, 4.1, 4.2, 4.3Subarea, subarea surface [0158] 5Contour, engraving [0159] 6Sprinkling nozzle [0160] 7Temperature regulator [0161] 8Solid area of the mould [0162] 9End plate [0163] 10Separating-passing element [0164] 11Valve, solenoid valve [0165] 12Sensor, temperature sensor [0166] 13External heating medium [0167] 14Mould [0168] 15Breakthrough [0169] 16Weld [0170] t.sub.iTime [0171] , .sub.iHeat transfer coefficient [0172] , .sub.iTemperature [0173] aArea, breakthrough [0174] ARise at point .sub.4,q.sub.4 [0175] KBeginning of area of convection of the water at the wall, with dropping wall temperature [0176] VVolume flow