Reinforced structural components

Abstract

A method for manufacturing reinforced steel structural components is described. The method comprises providing a previously formed steel structural component, selecting one or more reinforcement zones of the previously formed structural component, and locally depositing a material on the reinforcement zone to create a local reinforcement on a first side of the structural component. Locally depositing a material on the reinforcement zone comprises supplying a metal filler material to the reinforcement zone, and substantially simultaneously applying laser heat to melt the metal filler material and create the reinforcement by drawing specific geometric shapes on the first side of the structural component with the metal filler material and the laser heating. And the method further comprises providing cooling to areas on an opposite side of the structural component. The disclosure further relates to a tool for manufacturing reinforced steel structural components and to the components obtained using such methods.

Claims

1. A method for manufacturing reinforced steel structural components, the method comprising: locally depositing a material on a reinforcement zone of a previously formed structural component to create a local reinforcement on a first side of the structural component, wherein locally depositing a material on the reinforcement zone comprises: supplying a metal filler material to the reinforcement zone, and simultaneously applying laser heat to melt the metal filler material; drawing specific geometric shapes on the first side of the structural component with the metal filler material and the laser heating to create the local reinforcement; and cooling areas on a second side of the structural component that is opposite to the first side, wherein cooling the areas comprises: bringing a working surface of a tool in contact with the second side of the structural component; and aligning a channel formed in the tool and configured to circulate cold fluid therethrough with heat-affected zones abutting the reinforcement zone.

2. The method of claim 1, wherein the structural component has a thickness in the range between 0.7 mm to 5 mm.

3. The method of claim 1, wherein the metal filler material comprises metal powder provided in a powder gas flow.

4. The method of claim 1, wherein the heat-affected zones abutting the reinforcement zone comprises areas abutting the reinforcement zone in at least one of a transversal direction or a longitudinal direction in at least one of a horizontal plane or a vertical plane.

5. The method of claim 1, wherein the previously formed steel structural component is made from boron steel.

6. The method of claim 1, wherein the previously formed structural component is obtained by hot forming die quenching.

7. The method of claim 1, wherein cooling areas on the second side of the structural component further comprises directing an air stream to the areas on the second side of the structural component from one or more air injectors or blowers.

8. The method of claim 1, further comprising determining a temperature of the heat-affected zones abutting the reinforcement zone, and cooling the areas on the second side of the structural component as a function of the temperature of the heat-affected zones.

9. The method of claim 1, wherein the previously formed steel structural component is formed from a blank having a single thickness.

10. The method of claim 3, wherein the metal powder comprises a stainless steel based powder.

11. A tool for manufacturing reinforced steel structural components, the tool comprising one or more working surfaces that in use face the structural component to be reinforced, wherein the structural component comprises one or more reinforcement zones, and the tool further comprising cooling elements configured to cool down at least portions of an opposite side of the working surface, the cooling elements being arranged such that in use they are aligned with heat-affected zones abutting the reinforcement zone such that a cooling rate of the heat-affected zones can be regulated to obtain a martensite microstructure at the heat-affected zones wherein the working surface comprises one or more portions having a substantially U-shaped cross-section.

12. The tool of claim 11, wherein the cooling elements comprise channels configured for circulation of a cold fluid.

13. A reinforced steel component as obtainable by any of the methods according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Non-limiting examples of the present disclosure will be described in the following with reference to the appended drawings, in which:

(2) FIG. 1 schematically shows an example of applying powder, laser welding and cooling to a formed structural component;

(3) FIG. 2 shows an example of cooling elements;

(4) FIG. 3 shows another example of cooling elements;

(5) FIG. 4 shows a structural component and cooling elements according to an example;

(6) FIG. 5 shows another example of a structural component and cooling elements;

(7) FIGS. 6a and 6b respectively show examples of the microstructure of a reinforced structural component obtained when reinforcements are applied to substantially thin and thick structural components without cooling as provided in the present disclosure; and

(8) FIG. 7 shows an example of the microstructure of a reinforced structural component when a reinforcement is applied using tools and methods substantially as hereinbefore described.

DETAILED DESCRIPTION OF EXAMPLES

(9) FIG. 1 shows an example of applying a reinforcement 6 at a first surface 71 of a formed structural component 7, for example, a hot stamped component (made e.g. by HFDQ). In alternative examples, other ways of forming the component may also be foreseen such as cold forming, hydroforming or roll forming. A second surface 72 of the structural component 7 that is opposite to the first surface 71 may be provided on working surface of a tool 8. In the example of FIG. 1, the working surface is substantially flat. In alternative examples, the working surface may have other shapes depending on the shape of the formed structural component. See FIGS. 4 and 5.

(10) In this example, a laser welder 1 may be provided. The laser welder 1 may have a laser head 3 from which a laser beam exits. A gas powder flow 2 indicated with an interrupted line with arrow may also be provided. The gas powder flow 2 may be fed in a coaxial manner with respect to the laser beam towards the zone on which the reinforcement 6 is to be formed. The gas powder flow 2 may thus be fed to the zone on which the reinforcement 6 is to be formed while the laser beam is being applied.

(11) FIG. 1 further shows a schematic HAZ or boundary area 61 abutting the reinforcement 6. The size and shape of this area mainly depends on the power of the laser, the laser spot size, time of exposure to the laser heating, drawing patterns and/or the thickness of the formed structural component.

(12) In these examples, a gas powder head may be coaxially arranged with respect to the laser head 3 and both heads may be arranged such that the gas powder flow 2 and the laser beam may be substantially perpendicular to the first surface of the component 71, i.e. the surface on which the reinforcement 6 is to be formed.

(13) In alternative examples, the gas powder flow may be fed at an angle with respect to the component. In some of these examples, the gas powder flow may also be fed at an angle with respect to the laser beam or it may be coaxially arranged with respect to the laser beam as in the previous example.

(14) In some examples, argon may be used as a transportation gas, depending on the specific implementation. Other examples of transportation gas may also be foreseen, e.g. nitrogen or helium.

(15) As further shown in FIG. 1, optionally, a shield gas channel 4 may also be provided. In these cases, the shield gas channel 4 may be coaxially provided with respect to the laser beam to supply a shield gas flow 5 around the zone on which the reinforcement 6 is to be formed. In some examples, helium or a helium based gas may be used as a shielding gas. Alternatively an argon based gas may be used. The flow rate of the shielding gas may e.g. be varied from 1 liter/min to 15 liters/min. In further examples, no shielding gas may be required.

(16) The laser may have a power sufficient to melt at least an outer surface (or only an outer surface) of the first surface of the component and thoroughly mixed/joined the powder throughout the entire zone on which the reinforcement 6 is to be formed.

(17) In some examples, welding may comprise welding using a laser having a power of between 2 kW and 16 kW, optionally between 2 and 10 kW. The power of the laser should be enough to melt at least an outer surface of a formed component having a typical thickness i.e. in the range of 0.7-5 mm. By increasing the power of the welder the welding velocity may be increased.

(18) Optionally, a Nd-YAG (Neodymium-doped yttrium aluminium garnet) laser may be used. These lasers are commercially available, and constitute a proven technology. This type of laser may also have sufficient power to melt an outer surface of a formed component and allows varying the width of the focal point of the laser and thus of the reinforcement zone. Reducing the size of the spot increases the energy density, whereas increasing the size of the spot enables speeding up the welding process. The weld spot may be very effectively controlled and various types of welding are possible with this type of laser.

(19) In alternative examples, a CO.sub.2 laser with sufficient power may be used. In further examples, twin spot welding may also be used.

(20) In some cases, the powder fed to the reinforcement zone may be stainless steel AlSi 316L, as commercially available from e.g. Hoganas. The powder has the following composition in weight percentages: 0%-0.03% carbon, 2.0-3.0% of molybdenum, 10%-14% of nickel, 1.0-2.0% of manganese, 16-18% chromium, 0.0-1.0% of silicon, and the rest iron and impurities. Alternatively 431L HC, as commercially available from e.g. Hoganas may be used. This powder has the following composition in weight percentages: 70-80% of iron, 10-20% of chromium, 1.0-9.99% of nickel, 1-10% of silicon, 1-10% of manganese and the rest impurities.

(21) Further examples may use 3533-10, as further commercially available from e.g. Hoganas. The powder has the following composition in weight percentages: 2.1% carbon, 1.2% of silicon, 28% of chromium, 11.5% of nickel, 5.5% of molybdenum, 1% of manganese and the rest iron and impurities.

(22) It was found that the presence of nickel in these compositions led to good corrosion resistance. The addition of chromium and silicon aids in corrosion resistance, and molybdenum (AlSi 316L or 3533-10) aids in increasing the hardness. In alternative examples other stainless steels may also be used even UHSS. In more examples, the powder may incorporate any component providing higher or lower mechanical characteristics depending on circumstances.

(23) As further shown in FIG. 1, channels 10 may be provided in correspondence with portions of the tool working surface 8 that may be in correspondence with the boundary area 61 abutting the reinforcement zone. The channels 10 may be provided at a side opposite to the side on which the working surface effectively receives the second surface 72 of the structural component to be reinforced 7. And the channels 10 may be configured for circulation of a cold fluid. The circulation of a cold fluid through the channels involves extra cooling to at least those portions of the working surface that are in correspondence with the boundary area 61 (HAZ). This extra cooling speeds up the cooling rate of these portions thus enhancing mechanical properties of the final reinforced component as it ensures that a martensite microstructure is also formed at the boundary area 61.

(24) In the example of FIG. 1 two channels 10 have been depicted. However other number of channels may be foreseen or even a single channel, depending on the size of the reinforcement zone, the power of the laser, the laser spot size, time of laser exposure, drawing patterns and/or the shape and thickness of the formed structural component.

(25) In further alternatives, instead of channels, an air stream, in particular cooled air, may be provided to the second surface 72 of the structural component. See the example of FIG. 4.

(26) FIGS. 2 and 3 show different examples of channels that may be used in the example of FIG. 1. In these figures the same reference signs have been used to designate matching elements.

(27) In the examples of FIGS. 2 and 3, an elongate structural member may define the channel 10 that may extend substantially along the length of a reinforcement to be formed on a component. The channels 10 may be formed from two concave halves being joint together so as to define a hollow space (the channel) through which a cooling medium may circulate. To promote fluid circulation an inlet 10a and an outlet 10b may be provided at opposite ends of the channel. Cold water, cooled air or any other cooling fluid may circulate through the channels. Alternatively, the channels may be built in a single piece.

(28) The examples of FIGS. 2 and 3 differ in the shape of their cross-section and in some constructional features that will be pointed out later on. However, these constructional features could be combined differently in more examples.

(29) In the example of FIG. 2 the cooling channel may have a rectangular cross-section. At least one of the channels halves may be provided with an O-ring 11 or any other mechanical gasket able to be seated surrounding a groove or concavity and able of being compressed between two or more parts being put together. This guarantees sealing of the two channel's halves when the channel is being put together. The channel 10 may be fixed to a plate 12 at each end. And the plates 12 may be fixed to the working surface of the tool by e.g. screws or any other fastening means.

(30) In the example of FIG. 3 the channel may have a circular cross-section. Clamps 13 may be provided instead of plates at the channel ends. The clamps may be machined together with the channel halves or they may be separate clamps. The clamps may serve for joining together the channel halves and for fixing the channel to the working surface. In both cases the clamps may be provided with holes 14 for screws or any other fastening means. In some cases the same fasteners used for maintaining together the channel halves may be used for fixing the channel to the working surface. Other known fasteners may be foreseen.

(31) FIGS. 4 and 5 show alternative examples of cooling elements for a substantially U-shaped structural component 7. The same reference signs have been used to designate matching elements. In these figures the reinforcement, the laser unit and powder nozzle (or filler wire or rod) have been deleted in order the more clearly show examples of the cooling elements.

(32) In the example of FIG. 4, an air stream passage (arrow A) may be defined by the U-shape of the structural component 7. Through this passage a cold airflow may be circulated for example using a ventilator, a fan or a compressor (as a compressed air source).

(33) The example of FIG. 5 differs from that of FIG. 1 in that the tool working surface 8 may comprise a substantially U-shaped cross-section that follows the contour of the structural component 7 to be reinforced. As mentioned before, by providing a tool working surface substantially copying the shape of the structural component to be reinforced, additional support for the structural component may also be provided by the tool working surface thus avoiding or at least substantially reducing deformation of the component due to thermal stress. In the example of FIG. 5, four channels 10 have been depicted.

(34) However, as explained in connection with FIG. 1 other number or channels (even a single channel) may be foreseen depending on the reinforcement zone to be applied to the component. The channels depicted in the examples of FIG. 2 or 3 may also be used in the example of FIG. 5. In the example of FIG. 5, the channels are shown extending in the longitudinal direction of the structural component however, in further examples the channels may extend transversally to the structural component or combinations thereof.

(35) FIGS. 6a and 6b show examples of the microstructure of a reinforced structural component when prior art reinforcements are applied to structural components made of relatively thin (FIG. 6a) and relatively thick (FIG. 6b) material.

(36) FIG. 6a shows an example of a previously formed structural component 7 made of a substantially thin blank, e.g. having a thickness lower than approximately 1.6 mm. The reinforcement 6 may be applied depositing a metal filler when laser heating is being applied. Arrow 62 shows a portion of filler that may be mixed with the outer surface of the component 7. In this example, the final reinforced structural component may comprise the resulting following microstructure: area B having a martensite microstructure, area A having mainly a bainite microstructure (with presence of ferrite perlite and martensite) and area C having a ferrite matrix microstructure (with presence of martensite and bainite and perlite).

(37) The example of FIG. 6b differs from that of FIG. 6a in that the thickness of the previously formed structural component is higher. The same reference signs have been used to designate matching elements. The example of FIG. 6b further differs from that of FIG. 6a in the shape of the resulting microstructure obtained. However, in both examples, area C having a a ferrite matrix microstructure (with presence of martensite and bainite and perlite) is found. Notably, the HAZ in the case of the thicker component does not extend through the entire thickness of the component.

(38) The example of FIG. 7 shows a previously formed structural component in which a reinforcement has been applied using tools and methods substantially as hereinbefore described, i.e. applying cooling to HAZ areas while the reinforcement is being applied. In this example, the final reinforced structural component may have the following resulting microstructure: area B having a martensite microstructure (more than 400 Hv thus more than 1300 Mpa, preferable more than 450 Hv, i.e. more than 1450 Mpa) and area A having mainly a bainite microstructure (with presence of ferrite perlite and martensite, i.e. approximately 250-350 Hv, thus 800-1100 Mpa). This means that using the tools and methods described herein the areas of the reinforced structural component having a ferrite matrix microstructure have disappeared. In further examples, depending on circumstances, i.e. the thickness of the structural component, the laser heating or speed of laser exposure among other factors, the area A may be made smaller or it may even also disappear. This means that the final reinforced structural component has enhanced microstructure (hardness properties).

(39) In general, the channels consist of a sealed tube or pipe of a material that is compatible with the cooling fluid to be circulated therethrough. The channels may be made from any suitable material able to conduct the cooling properties of the cold fluid circulating inside the channel. In some examples, the channels may be made of any metal or metal allow, e.g. steel or steel alloy. As explained in connection with FIG. 4, the channels may further be provided in combination with a vacuum pump or a compressor for circulation of cold airflow.

(40) In an example, the formed component may be made by hot forming die quenching a boron steel blank that may be made coated or uncoated, such as e.g. Usibor.

(41) In addition, above-mentioned cooling elements are quite simple in construction, cost-effective and yet capable of efficiently achieving a desired cooling rate at the boundary areas abutting a reinforcement zone.

(42) In more examples, a control system and temperature sensors (not shown) may be provided to control the temperature at heat-affected zones abutting the reinforcement zone. The sensors may be thermocouples. The thermocouples may be associated with a control panel. When more than one channel is provided, each channel (or cooling element) may thus be activated independently from the other. Thus using a suitable software or control logic, a user will be able to set the key parameters (temperature, temperature limits) based on which the cooling rate can be regulated to obtain a martensitic structure at the boundary areas abutting the reinforcements.

(43) Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible.

(44) Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.