Method and tools for manufacturing of seamless tubular shapes, especially tubes

Abstract

The present invention relates to a method and tools for manufacturing of seamless tubular shapes, especially tubes and canisters. In the method of the invention the tubular shape is extracted from the flash continuously produced during the plunging of a consumable rod against a rigid anvil. The tools of the invention include a consumable rod; a non-consumable or consumable rigid anvil; first means for rotating the consumable rod and the non-consumable or consumable rigid anvil relatively with respect of each other; second means for plunging the consumable rod and the non-consumable or consumable rigid anvil relatively against each other; open die condition configuration for continuous production of flash during said plunging.

Claims

1. A method for manufacturing a seamless tubular shape formed by continuously-produced flash, comprising the step of plunging a consumable rod against a rigid anvil, wherein the consumable rod has a longitudinal axis and there is a relative rotational speed between the consumable rod and the anvil about an axis of rotation that is coincident with the axis of the consumable rod, and where said continuously-produced flash is obtained by viscoplastic deformation of the consumable rod against the rigid anvil in full open die condition, and where the rigid anvil is a plate unit with no through holes in the zone in contact with the consumable rod.

2. A method according to claim 1, where the consumable rod has a longitudinal axis and there is a relative rotational speed (Vz) between the consumable rod and the anvil about an axis of rotation that is coincident with the axis of the consumable rod.

3. A method according to claim 1, where the consumable rod has a longitudinal axis coincident with an axis of symmetry of the flash.

4. A method according to claim 1 where the consumable rod is cylindrical with a diameter along a longitudinal axis thereof.

5. A method according to claim 4 where the consumable rod is cylindrical with a constant-diameter along the longitudinal axis thereof.

6. A method according to claim 4 where the consumable rod is cylindrical with a variable-diameter along the longitudinal axis thereof.

7. A method according to claim 1 where plunging of the rotating consumable rod or anvil is performed using an alternative selected one of a force control mode and a speed control mode, and where it is possible to change the selected one during plunging.

8. A method according to claim 1 where the outer diameter and thickness of the flash is set by controlling of at least one of the following parameters: plunge force or plunge speed; relative rotational speed between the consumable rod and the rigid anvil; diameter of the consumable rod; thermo-physical properties of the consumable rod material; thermo-physical properties of the optionally consumable anvil material; boundary conditions (e.g. geometrical, mechanical and thermal conditions) applied to the flash.

9. A method according to claim 1 including the following steps: starting the relative rotation between the consumable rod and the rigid anvil; bringing the consumable rod into contact with rigid anvil under speed control; starting the plunging period under an alternative one of force control and speed control; adjusting the relative rotation, control mode and its value towards the final desired tubular shape; and thereafter selectively obtaining a tube or a cannister, where obtaining a tube comprises extracting both an open end and a closed end from the tubular shape remaining at the completion of the plunging phase; and obtaining a canister comprises extracting only the open end from the tubular shape remaining at the completion of the plunging phase.

10. A method according to claim 1 where the consumable rod and flash independently of each other are free or guided, to prevent loss of stability, during the plunging phase.

11. A method according to claim 1 where the consumable rod is plunged with the support of a rigid non-consumable rod, clamped to the consumable rod, and used as a plunger of the consumable rod, during the plunging phase.

12. A method according to claim 1 where the rigid anvil is a non-consumable plate unit.

13. A method according to claim 1 where the rigid anvil is a consumable plate unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention is in the following described in more detail in the form of examples of preferred embodiments by referring to the attached drawings, wherein

(2) FIG. 1 is a schematic drawing of two alternative embodiments of the present invention,

(3) FIG. 2 is a schematic drawing of the sequence of the main plunge periods in one embodiment of the present invention,

(4) FIG. 3 is a schematic representation of alternative clamping of the consumable rod in the present invention,

(5) FIG. 4 is a schematic representation of the range of possible geometries for the tip of the consumable rod 2 at the start position such as that one presented in FIG. 2,

(6) FIG. 5 is a schematic representation of alternative shapes, for the contacting surface with the rod 2, of the non-consumable insert according to the invention,

(7) FIG. 6 is a schematic representation of a sample of possible boundary conditions (e.g. geometrical, mechanical and thermal conditions) applied to the flash,

(8) FIG. 7 shows the different tube formation periods for producing a tubular shape having three different main outer diameters in accordance with the present invention,

(9) FIG. 8 depicts two tailor made tubes with continuous varying outer diameter and/or thickness,

(10) FIG. 9 illustrates a particular embodiment for manufacturing long tubes according to the invention, but with additional use of support guides for the consumable rod and the tube under formation, and

(11) FIG. 10 is schematic illustration of a canister made according to the invention.

(12) In FIG. 1 is presented the process fundaments during stationary state of plunge period (i.e. tube formation, cf. FIG. 2) of the present invention, with representation of the alternative control of the plunge force (Fz) or plunge speed (Vz). In alternative (a) the rod 2 rotates at a rotational speed Ω with plunge force Fz or plunge speed Vz against the anvil 3 that is stationary. In alternative (b) the rod 2 is stationary while the anvil 3 is rotating against the rod 2 at a rotational speed Ω with plunge force Fz or plunge speed Vz.

(13) The method of the invention is a process to produce seamless tubes, extracted from the flash 1 continuously produced during the plunging of a consumable rod 2 against a non-consumable rigid anvil 3 as in alternative (a) in FIG. 1 or a non-consumable rigid anvil 3 is plunged against consumable rod 2 as in alternative (b) in FIG. 1. Between the rod 2 and the anvil 3 there is a relative rotational speed Ω. The flash 1 forms a net-tube that is cylindrical with stable and controllable geometry. The axis of symmetry of the flash 1 is coincident with the axis of the consumable rod 2 and the axis of rotation during the plunging period. The geometry of the flash 1 has an outer diameter and thickness that are set via controlling of the following parameters: Plunge parameters: plunge force Fz or plunge speed Vz; Relative rotational speed Ω between the consumable rod 2 and the non-consumable rigid anvil 3; Diameter of the consumable rod 2; Thermo-physical properties of the consumable rod 2 material; Boundary conditions (e.g. geometrical, mechanical and thermal conditions) applied to the flash 1.

(14) The consumable rod 2 consists of a base material while the nonconsumable rigid anvil insert 3 is made of a material that has a mechanically rigid behaviour, with enough toughness, at the peak processing temperature, e.g. a refractory material. The anvil insert 3 may be mounted in a rigid backing plate 4 or anvil insert support (water cooled option). The consumable rod 2 may with respect of state of the base material be divided into three zones or domains: a cool domain 5 of the consumable rod wherein the base material of the rod is elastic; a pre-heat zone domain 6 of the consumable rod wherein the base material of the rod is elastic-plastic; and a hot solid-state domain 7 of the consumable rod wherein the base material of the rod is viscoplastic. This division into three zones or domains is the same in both alternatives (a) and (b) in FIG. 1.

(15) The “Speed profile” indicated in FIG. 1 represents the intensity of the rotational speed as a profile for the different sub-zones of the consumable rod 2. A significant part of the heat is generated in the discontinuity of the speed profile between the pre-heat zone of consumable rod domain 6 and the hot solid-state consumable rod domain 7. In the “Stick-friction” condition indicated in FIG. 1 the hot solid-state consumable rod domain 7 sticks to the non-consumable rigid anvil insert 3, and thus the speed profile has zero value at this interface. In the “Sliding” friction condition also indicated in FIG. 1 the hot solid-state consumable rod domain 7 slides over the non-consumable rigid anvil insert 3, and thus the speed profile has a value higher than zero, at this interface.

(16) FIG. 2 depicts the sequence of the main periods of the method of invention for tube formation: (a) Start position; (b) Dwell plunge period; (c) Transient plunge period; (d) Stationary plunge period.

(17) At the start position (a) the consumable rod 2 rotates with a rotational speed Ω but it is not yet in contact with the anvil 3 and the plunge force Fz.sub.0 of the rod 2 is 0 (zero). At this point there is thus no flash formation yet.

(18) During the dwell plunge period (b) the consumable rod 2 is plunged against the rigid anvil 3 rotating at a rotational speed Ω with an initial plunge force Fz.sub.0 and initial plunge speed Vz.sub.0 of the rod 2. In this period the flash 1 is starting to form but it is not yet fully developed for the formation of e.g. tubes.

(19) At the end of the initial transient plunge period (c) the consumable rod 2 is plunged against the rigid anvil 3 rotating at a rotational speed Ω with an plunge force Fz and plunge speed Vz of the rod 2, wherein Fz>Fz.sub.0 and Vz>Vz.sub.0. During this period the flash 1 has had time to fully develop its geometry towards the desired geometry.

(20) During the stationary plunge period (d) the consumable rod 2 is plunged against the rigid anvil 3 still rotating at a rotational speed Ω with the same plunge force Fz and plunge speed Vz of the rod 2 as during the transient plunge period (d), but now the flash 1 has had time to fully develop the desired geometry for the formation of tubes or other tubular shapes.

(21) The dimensions of the flash are possible to keep constant or to be modified during the processing method of the invention. A continuous modification of outer diameter and/or thickness of the flash is possible through control of the process parameters, e.g. boundary conditions, within the domain of stable operative window of parameters.

(22) FIG. 3 depicts that for being able to plunge the consumable rod 2 against the anvil 3 (or the other way around) with a relative rotational speed Ω, a plunge force Fz and a plunge speed Vz, the rod 2 needs to be clamped in some way to a device that rotates and plunges the rod 2 against the rigid anvil 3 that needs to be held in place by a rigid backing plate 4 or the like. In the magnified window of the upper end part of the consumable rod 2 is shown two alternatives for clamping; internal clamping 13 and external clamping 14 of the rod 2.

(23) The internal clamping 13 solution of the rod 2 represented in FIG. 3 enables a quasi-complete plunging of the consumable rod 2, i.e. a plunging to the level of the hot solid-state consumable rod domain 7, transforming most of the initial consumable rod 2 into a tubular shape from flash 1, such as a tube or a canister 11 (cf. FIG. 10).

(24) FIG. 3 also shows a zone of “shielding gas” surrounding and shielding at least a part of the flash in that end of the rod that is transformed into flash. The “shielding gas” represents a volume containing the processed zone where a non-chemically reactive gas replaces the atmospheric gas and shields the processed zone while this zone is at temperatures higher than the room temperature.

(25) FIG. 4 depicts a range of possible geometries for the tip of the consumable rod 2 at the start position. In all geometries shown in FIG. 4 the rod consists of a cylindrical part with the diameter D.sub.rod and a tip part having the diameter D.sub.tip in the range of [0, D.sub.rod]. The shape of the tip may thus be in the form of a cone (D.sub.tip=0), a truncated cone (D.sub.tip=]0, D.sub.rod[) or a cylinder (D.sub.tip=D.sub.rod). The tip part has a length l.sub.0=[0, l.sub.max].

(26) FIG. 5 shows three alternative shapes for the non-consumable anvil insert 3 namely a cone; a semi-spherical concavity, and a wavelike concavity. The respective functions of these alternative shapes are to provide a stable and preferential direction for the viscoplastic material flow of consumable rod 2, enabling the flash 1 to reach the desired final diameter. The anvil is made of a material that has a mechanically rigid behaviour, with enough toughness, at the peak processing temperature, e.g. a refractory material.

(27) In FIG. 6 is presented two embodiments, (a) on the left and (b) on the right, of a sample of possible boundary conditions, e.g. geometrical, mechanical and thermal conditions, applied to the flash.

(28) In embodiment (a) of FIG. 6 is depicted a method for outer surface finishing and dimensional control of the flash 1 that is formed during the method of invention. Embodiment (a) involves the use of one or more cutting tool devices 8 that may be stopped or moving (axially or radially in relation to the axis of the consumable rod 2) for finishing the rotating flash 1 into a tubular shape with desired outer diameters, thicknesses and/or lengths. The cutting tool device 8 may be used for cutting either during the formation of the flash 1, i.e. during the plunging phases (transient or stationary), or after the plunging is completed and the flash 1 is still rotating.

(29) In embodiment (b) of FIG. 6 is illustrated a method for producing variable tube dimensions along the length of the tube formed from the flash 1. The variable tube dimension along the length of the tube to be formed is achieved by using one or more mould devices 9 to shape the tubular shape (also called net-tube formation) formed from the flash 1. The mould device 9 illustrated in the embodiment (b) of FIG. 6 has the shape of a truncated cone with a central cylindrical through-bore having the same inner diameter as the outer diameter of consumable rod 2. The central lengthwise axis of the cylindrical through-bore is coincident with the central lengthwise axis of the mould device 9. The mould device 9 is inserted around the consumable rod 2 before starting the tube formation. The flash 1 formed this way will have precise outer and inner dimensions. The consumable rod 2 surrounded by the mould device 9 is plunged against the anvil 3 at a rotational speed Q with a plunge force Fz and plunge speed Vz. During the movement of the rod 2 against the anvil 3, the mould device 9 is kept at the same distance from the anvil 3.

(30) In FIG. 7 is depicted, from left to right, (a) the start position, (b) the stationary plunge period with a first stable dimension of the flash 1, (c) the stationary plunge state of tube formation, with different parameters from the previous one (b) resulting in a different but stable flash 1 dimension, and (d) the stationary plunge state of tube formation with different parameters from the previous periods (b) and (c), resulting in a situation where a rotative consumable rod 2 is plunged against a non-rotative 3 non-consumable rigid anvil 3 to form a tube having three different main outer diameters. The shape of the tube or canister is formed from the continuous flash 1 resulting from the continuous plunging process is achieved in an open die condition, i.e. without any closed dies, only by varying the plunging parameters, plunging force F.sub.z, plunging speed V.sub.z, and rotational speed Ω during the plunging phase.

(31) The capacities for tailor made tubes in a wide range of dimensions, include the possibility to innovate tube design based on continuously varying section configurations, similarly to the capacity of shaping a pot from a piece of clay. FIG. 8 shows an example of this kind of tube formation when a consumable rod 2 is plunged against a rigid anvil 3. In the right-hand side tube formation example (b) is depicted a stationary state of a flash 1 with constant outer diameter and continuous varying thickness. In the left-hand side flash 1 formation example (a) is depicted a stationary state of a flash 1 formed from processing parameters plunging force F plunging speed V and rotational speed Ω being continuously varied over time, resulting in different outer diameters and thicknesses of the tube in its longitudinal direction, Among each possible outer diameters (D) and thicknesses (t) of the tube the following are depicted in the figure as examples: thicknesses t.sub.1, t.sub.2, t.sub.3, t.sub.4, t.sub.5 and corresponding diameters D.sub.1, D.sub.2, D.sub.3, D.sub.4, D.sub.5.

(32) In FIG. 9 is depicted an embodiment particularly meant for producing long cylindrical tubes where both the consumable rod 2 and the flash 1 are supported to prevent any loss of stability of the rotating axis of the consumable rod 2 (e.g. via buckling) at a certain phase of a plunging process, having the steps, from left to right, (a) the start position, (b) the dwell plunge period, (c) the transient state of tube formation, and (d) the stationary state of tube formation. In this particular embodiment a rotative consumable rod 2 is plunged against a non-rotative non-consumable rigid anvil 3 to form a tube from a flash continuously produced at the working zone in an open die condition (i.e. no die is used for shaping the tube from the flash).

(33) In order to prevent buckling of the consumable rod 2 a guiding ring 10 with gliding contact with the rod 2 is used. In the start position (a) of the plunging process the tip, shaped as a truncated cone, of the consumable rod 2 is inside the guiding ring 10 but the rod is not yet in gliding contact with the guiding ring 10. At this start position (a) the consumable rod 2 has a rotational speed Ω and a plunging force F.sub.z0=0. In the dwell plunge period (b) the consumable rod 2 has moved through the guiding ring 10 in gliding contact therewith and supported thereby. In this period the consumable rod 2 has a rotational speed of is Ω, a plunging force F.sub.z0, a plunging speed V.sub.z0 and the flash formation, and the tube formation therefrom is yet in its initial state. When the plunging process reaches the transient state (c) of tube formation, the support, that is, the guiding ring 10 is released by pulling apart, in opposite directions, the two or more components that the guiding ring 10 is comprised of, before the flash 1 (tubular shape under formation) reaches guiding ring 10. The structure behind the mechanism allowing the pulling apart is not shown in the figure. In the transient state (c) of the tube formation the consumable rod 2 has a rotational speed of Ω, a plunging force F.sub.z, a plunging speed V.sub.z. In the stationary state (d) of the tube forming two or more components of another guiding ring 10 is closed around a section of the flash 1 being formed in order to support and stabilize said flash 1 (i.e. not to shape the flash) along its circumference. In this state the consumable rod 2 has a rotational speed of is Ω, a plunging force F.sub.z, a plunging speed V.sub.z.

(34) Long tubes can be obtained from several engineering design solutions, namely: Continuous feeding of a non-rotative rod 2 using a rotative non-consumable rigid anvil 3; Using long rods with support guides 10, applied initially to the rod, and passing progressively to the flash 1. This prevents buckling of the consumable rod during the dwell, transient and stationary plunging periods; Using clamping systems with smaller or equal diameter to the rod diameter, to enable the plunging of the full length of the consumable rod, as represented in FIG. 3.

(35) The method of the invention solves the following customer demands: i) small series of ii) tailored made tubes in a iii) wide range of dimensions and iv materials.

(36) Considering that the physical fundamentals (solid-state viscoplastic material flow) supporting the method of the invention enables to process thermomechanically almost all the engineering materials, this invention is able to solve the perceived market need for tubes made of materials not yet available in the market, besides the production of tubes made of materials already available in the market. The engineering materials suitable for a consumable rod used in the method and the tools of the invention include metals and alloys thereof. These metals may be ferrous or non-ferrous. Examples of ferrous metals include Cast Iron, Wrought Iron, Stainless steels and Steels, such as, Structural Mild Steel, High Strength Steel, Silicon Steel, Tool Steel, Spring Steel, but are not limited thereto. Examples of non-ferrous metals are Aluminium, Nickel and Titanium, and alloys thereof, but the non-ferrous metals are not limited thereto.

(37) Tubes and pipes are hollow shaped components with circular cross section and are one of the most common and thus significant components used in engineering solutions. The difference between tubes and pipes is the envisioned application, where pipes are used for fluid flowing and thus internal diameter is the most important dimension in design, and tubes are supposed to be used for remaining applications, with external diameter and wall thickness as the most important dimensions.

(38) Applications of tubes are found in structural and non-structural applications, in a wide range of quality and precision specifications. Examples of relevant fields of application are structural space frames, oil and gas distribution, heat exchangers, boilers, and, air conditioning and domestic water distribution. Emphasis also to the increasing number of applications in precision mechanics namely via capillary tubes for medical applications, measurement devices and control systems. The chemical industry field, e.g. cosmetics & oral care, food & beverages and pharmaceuticals, is one other intensive user of tubes.

(39) In particular, the metallic tubular components are broadly categorized, according to the manufacturing method as: i) seamless tubes; and ii) welded tubes.

(40) The welded tubes are optionally welded in line with continuous forming for thinner sheets or welded after bending and forming for thicker plates. Welded tubes have asymmetric properties, including a fusion zone with local modification of original dimension features, and a heat affected zone with sub-zones of toughness and hardness mismatching the ones from the base material. In fact, this general classification of tubular structures encloses and emphasizes how to distinguish the applications of seamless tubes from welded tubes.

(41) The seamless tubes have outstanding homogeneity in the circumferential direction and thus better mechanical resistance and more reliable structural and dimensional properties. Seamless tubes are the favourites for application involving extreme loading conditions, such as, static and cyclic internal pressure (e.g. tube hydroforming), torsion and impact under a wide range of service temperatures (e.g. drilling and pumping petroleum and natural gas). Seamless tubes are also the choice for applications demanding high quality and geometric precision and stability, from macro to micro-applications.

(42) In FIG. 10 is depicted a canister 11 that has been made by the method of invention, e.g. by plunging a rotative consumable rod against a non-rotative rigid anvil. A canister is achieved by the method of the invention simply by not cutting away the bottom of the flash 1 that is formed in the contact zone between a consumable rod 2 and a rigid anvil 3.

(43) Example of Application Sample Conditions, Parameters and Results Consumable rod material: cold roiled structural steel of grade S355; diameter [mm]=15 Spindle: Consumable rod rotation [Ω, rpm]=2888; Tool rotation direction=CW Transient plunging period: Control Method=Speed control; Plunging Speed [cm/min] (consumable rod)=0.15; Initial Plunge depth [mm]=3.9 Stationary plunging period: Control Method=Force control; Fz [kN]=26.60 Non-consumable rigid anvil insert 3, mounted in a support with water cooling in closed circuit, with inlet temperature of about 10° C.

(44) The tubular (cylindrical) product formed from the flash obtained in the plunging process had an outer diameter of 27 mm and a thickness of 2.8 mm.