JP5357112B2 - Steel pipe drawing device and steel pipe drawing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel pipe drawing device and a steel pipe drawing method in which excessive tensile stress is not applied to a core hanging bolt connected to a plug when a steel pipe is drawn out, and the core hanging bolt is not cut. <P>SOLUTION: In a steel pipe drawing step, a workpiece 43 is abutted against a floating die 41 to limit its contour, and simultaneously, it is abutted against the floating part 42a of the plug 42 to limit its thickness. Then, reaction force PN received by the floating part 42a of the plug 42 from the workpiece 43 is decomposed into vertical vector component reaction force PS and horizontal vector component reaction force PH, and only the horizontal vector component reaction force PH is made into the component of the force contributing to the drawing direction of the plug 42; where the plug 42 is stopped at a point in which the horizontal vector component reaction force PH and the force PZ at which the core hanging bolt (not shown in the figure) at the tip part in the right direction of the plug 42 is drawn to the drawing direction are balanced. Thus, the tensile force applied to the core hanging bolt is made into PH-PZ and almost zero, and there is no risk that the core hanging bolt is cut. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a steel pipe drawing apparatus and a steel pipe drawing method, and in particular, a steel pipe drawing apparatus and a steel pipe drawing method for producing a drawn steel pipe by relatively moving a die and a plug in the forward and reverse directions with respect to the steel pipe drawing direction. It is about.

  Conventionally, a hollow shaft having a desired thickness is preferably used as a boring rod for resource development, a shaft of an automobile, and the like from the viewpoint of reducing weight and reducing material costs. The hollow shaft used for these applications is formed of a stepped drawn steel pipe having a plurality of outer diameters and a plurality of inner diameters in the longitudinal direction. Such a drawn steel pipe is generally manufactured by cold drawing a raw steel pipe using a die and a plug (see, for example, Patent Document 1 and Patent Document 2). Moreover, the technique of manufacturing the drawing steel pipe in which the profile slit was formed from the raw steel pipe using the die | dye which has a protrusion in an axial direction, and a plug is also disclosed (for example, refer patent document 3 and patent document 4). According to this technology, since the profile slit is automatically formed in the drawing process of the material steel pipe without cutting the material steel pipe, the processing cost of the drawn steel pipe can be further reduced by reducing the number of processes. it can.

  According to such a method of manufacturing a drawn steel pipe, a drawn steel pipe having a desired size is manufactured by pulling out the raw steel pipe using a steel pipe drawing device while being narrowly pressed between the die and the plug. At this time, a stepped drawn steel pipe having a plurality of outer diameters and a plurality of inner diameters in the longitudinal direction is manufactured by appropriately changing the bearing diameter of the die and the bearing diameter of the tap according to the drawing position of the raw steel pipe. Can do.

JP 59-73113 A JP 59-73115 A Japanese Patent Laid-Open No. 10-249431 Japanese Patent Laid-Open No. 11-221612

  However, in the conventional steel pipe drawing device, when the steel pipe is drawn, there is a risk that excessive stress (tensile stress) is applied to the core hanging bolt connected to the plug in order to draw the material steel pipe, and the core hanging bolt is cut. is there. That is, when the material steel pipe is pulled out by the steel pipe drawing device, an excessive tensile stress is applied in the process of shifting from the thick part to the thin part of the steel pipe, so that the core suspension bolt may be cut from the plug. In particular, when a drawn steel pipe having a small diameter is manufactured, the diameters of the plug and the core suspension bolt are inevitably reduced, so that the core suspension bolt is easily cut.

  Therefore, there is a technical problem to be solved in order to prevent excessive tension stress from being applied to the core suspension bolt connected to the plug when the material steel pipe is pulled out and to prevent the core suspension bolt from being cut. The present invention aims to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 is characterized in that a floating die and a floating region having a floating angle corresponding to the floating die are divided into a small diameter region and a large diameter region. A steel pipe drawing apparatus comprising: a plug formed between the two, and producing a stepped drawn steel pipe by moving the floating die and the plug relative to each other in a forward and reverse direction with respect to a drawing direction of the material steel pipe. provide.

  According to this configuration, the plug receives from the material steel pipe in the floating region in the process of transition from the thick portion of the drawn steel pipe formed by the small diameter region of the plug to the thin portion of the drawn steel tube formed by the large diameter region of the plug. The plug stops at a point where the horizontal vector of the reaction force and the pulling force of the plug are balanced. Therefore, the pulling force of the core suspension bolt that pulls the plug when the steel pipe is pulled out can be made almost zero. As a result, there is no possibility that the core suspension bolt is cut from the plug by the pulling force applied to the core suspension bolt when the steel pipe is pulled out.

  The invention according to claim 2 provides the steel pipe drawing apparatus according to claim 1, wherein the floating angle is determined by a difference between a radius of a large diameter region and a radius of a small diameter region in the plug.

  According to this configuration, the floating angle formed in the floating region of the plug is such that the thick-walled portion of the drawn steel pipe formed in the small-diameter region of the plug and the thin-walled portion of the drawn steel tube formed in the large-diameter region of the plug. It is optimally determined by the difference in wall thickness. Therefore, even if the drawn steel pipe has a large thickness difference between the thick and thin parts, the tensile force applied to the core suspension bolt can be reduced to almost zero, so the core suspension bolt is cut from the plug when the steel pipe is withdrawn. The risk of being lost is eliminated. Further, even when a small diameter drawn steel pipe is formed, the pulling force applied to the thin core suspension bolt can be made substantially zero, so there is no possibility that the thin core suspension bolt is cut from the plug.

  The invention according to claim 3 is a steel pipe drawing method by a steel pipe drawing apparatus comprising a floating die and a plug in which a floating area having a floating angle corresponding to the floating die is formed between a small diameter area and a large diameter area. When the floating die and the plug are moved relative to each other in the forward and reverse directions with respect to the drawing direction of the material steel pipe to produce a stepped drawn steel pipe, the relative movement of the small diameter region of the plug The first step of forming the thick portion of the drawn steel pipe, and the relative movement of the floating area of the plug, the horizontal vector component of the reaction force that the floating area receives from the material steel pipe and the direction of the drawing of the plug The second step of balancing the pulling force and the relative movement of the large diameter region of the plug It provides a steel pipe drawing method characterized by performing a third step of forming a thin portion of the steel pipe.

  According to this method, when pulling out the material steel pipe, the pulling force of the core suspension bolt that pulls the plug is made substantially zero by the interaction between the floating die and the floating region of the plug in the process of transition from the thick part to the thin part. be able to. As a result, there is no possibility that the core suspension bolt is cut from the plug when the steel pipe is pulled out.

  According to a fourth aspect of the present invention, there is provided the steel pipe drawing method according to the third aspect, wherein the floating angle is determined by a thickness difference between the thick portion and the thin portion.

  According to this method, the floating angle of the floating region of the plug is optimally determined by the thickness difference between the thick and thin portions of the drawn steel pipe. Therefore, there is no possibility that the core suspension bolt will be cut from the plug, even if the drawn steel pipe has a large difference in thickness between the thick wall portion and the thin wall portion or is a very thin drawn steel tube.

  In the invention according to claim 1, since the drawn steel pipe is formed by making the floating die and the plug having the floating region face each other and relatively moving both, the pulling force of the core suspension bolt that pulls the plug when the steel pipe is pulled out Can be made almost zero. Therefore, there is no possibility that the core suspension bolt is cut from the plug by the pulling force of the plug when the steel pipe is pulled out.

  In the invention described in claim 2, since the floating angle of the plug is optimally determined by the thickness difference between the thick part and the thin part of the drawn steel pipe, in addition to the effect of the invention described in claim 1, Even when forming a drawn steel pipe having a large thickness difference between the portion and the thin-walled portion, or forming a small diameter drawn steel tube, there is no possibility that the core suspension bolt is cut from the plug.

  According to the third aspect of the present invention, when the material steel pipe is pulled out, the pulling force of the core suspension bolt that pulls the plug can be made substantially zero by the interaction between the floating die and the floating region of the plug. As a result, there is no possibility that the core suspension bolt is cut from the plug when the steel pipe is pulled out.

  In the invention described in claim 4, since the floating angle of the plug is optimally determined by the thickness difference between the thick part and the thin part of the drawn steel pipe, in addition to the effect of the invention of claim 3, any wall thickness Even when a drawn steel pipe having a shape is formed, there is no possibility that the core suspension bolt is cut from the plug.

A side view of a general steel pipe drawing device. The longitudinal cross-sectional view which shows the detail of the A section of FIG. The side view of the die support stand applied to the steel pipe drawing apparatus of this invention. FIG. 3B is a longitudinal sectional view showing details of the part of FIG. 3B. The cross-sectional view of the plug support stand applied to the steel pipe drawing apparatus of the present invention. (A), (b), (c) is a longitudinal cross-sectional view which shows the drawing state by the die | dye and plug which are applied to the steel pipe drawing apparatus of this invention. (A), (b), (c) is a longitudinal cross-sectional view which illustrates the drawing steel pipe manufactured with the steel pipe drawing apparatus of this invention. The principal part sectional drawing which shows the state which draws out a raw material steel pipe (work) with a die and a plug using a general steel pipe drawing device. The principal part sectional drawing which shows the state which draws out a workpiece | work using a floating die in the steel pipe drawing apparatus of this invention. Sectional drawing which shows the longitudinal direction of the plug used with the floating die applied to the steel pipe drawing apparatus of this invention.

  In order to achieve the purpose of preventing excessive tension stress from being applied to the core suspension bolt connected to the plug when the material steel pipe is pulled out, and preventing the core suspension bolt from being cut, A floating region having a floating angle corresponding to the floating die is formed between the small-diameter region and the large-diameter region, and the floating die and the plug are arranged in forward and reverse directions with respect to the drawing direction of the material steel pipe. This was realized by constructing a steel pipe drawing device that produced a stepped drawn steel pipe by relative movement.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. In addition, about each drawing used for the Example demonstrated below, the same component attaches | subjects the same code | symbol in principle, and the overlapping description is abbreviate | omitted.

  First, a general configuration of a steel pipe drawing apparatus for producing a hollow drawn steel pipe will be described. FIG. 1 is a side view of a general steel pipe drawing apparatus, and FIG. 2 is a longitudinal sectional view showing details of a part A in FIG. As shown in FIGS. 1 and 2, a die support base 3 for fixing the die 2 is provided at a substantially central portion of the frame 1 fixed to the floor. Further, a plug 4 and a plug support bar 5 that supports the plug 4 are provided, and the plug support bar 5 is fixed to the plug support base 6 via a hydraulic cylinder (not shown). Further, the material steel pipe 7 is fitted on the outer diameter side of the plug 4 and the plug support bar 5, and the tip end portion of the material steel pipe 7 is held between scissors 8 provided in the pulling wheel 9. Further, the claw 10 of the pulling wheel 9 is strongly pulled by a chain 11 driven by a powerful driving source (not shown), so that the material steel pipe 7 is narrowed between the die 2 and the plug 4 and pulled. The drawn steel pipe 7b is manufactured by drawing.

  In the steel pipe drawing apparatus of the present invention, when manufacturing a stepped drawn steel pipe 7b having a plurality of inner and outer diameters, a die 2 having a plurality of bearing surfaces and a plug 4 having a plurality of bearing surfaces are combined. The die 2 and the plug 4 can be moved in the forward and reverse directions relative to the drawing direction. As a result, even if the drawn steel pipe 7b is a small inner diameter pipe, no flaws are generated inside, and a tough drawn steel pipe with high dimensional accuracy can be manufactured.

  In order to realize such a steel pipe drawing apparatus, since the way of holding the die 2 and the plug 4 in relation to each other is different from the conventional one, these configurations will be described first. FIG. 3 is a side view of a die support base applied to the steel pipe drawing apparatus of the present invention, and FIG. 4 is a longitudinal sectional view showing details of the portion shown in FIG. 3B.

  As shown in FIG. 3, a stopper 16 is firmly fixed to the frame 1 and is reinforced by a reinforcing member 17. On the other hand, the die support base 30 equipped with the first hydraulic cylinder 20 for driving the die 2 is movably mounted on the carriage 12, and the carriage 12 moves on the rail 12a. One end of the die support base fixing ram 15 is fixed to the stopper 16. Specifically, as shown in FIG. 4, the surface 15a of the large-diameter flange portion 15b at one end of the die support base fixing ram 15 is connected to the bottom portion 30a of the cylindrical recess 30c of the die support base 30 with the piston rod 23 and the bin. The pressure is applied by the pressure of the first hydraulic cylinder 20 through the ear metal 24 protruding from the die support base fixing ram 15 coupled to the die 25.

  At this time, the pressing force (pressing force) generated in the first hydraulic cylinder 20 is a force that opposes the tube pulling force, and the pressing force of the first hydraulic cylinder 20 is stronger than the tube pulling force (for example, 150 to 200 t). There must be. In order to fix to a point existing in space with such a strong force, the method of pressing and fixing to the stopper 16 is the simplest method.

  Further, the die 2 is attached to the die support base 30. Therefore, the fixed position of the die 2 is a position where the fixed position on the right side of the die support base 30 and the surface 30b of the die support base 30 abut on the 16d surface of the stocker 16 correspond to the fixed position on the left side. .

  FIG. 5 is a cross-sectional view of a plug support base applied to the steel pipe drawing apparatus of the present invention. As shown in FIG. 5, the stopper 16a is firmly fixed to the frame 1, and the stopper 16a is further reinforced by a reinforcing member 17a. The hollow adjustment screw shaft 18 is fitted with the plug support rod 5, and the hollow adjustment screw shaft 18 that locks and supports the flange portion 5 a at the end of the plug support rod 5 is threaded on the outer periphery and is nut-type. The stopper 19 is screwed. The nut type stopper 19 can be screw-adjusted to match the required dimensions of the drawn steel pipe.

  The position where the left nut type stopper 19 contacts the surface 16b of the stopper 16a is the right fixed position, and the position where the right nut type stopper 19 contacts the surface 16c of the stopper 16a is the left fixed position. The pushing or pulling pressure of the second hydraulic cylinder 20a for driving the plug fixed to the frame 1 naturally generates a pressure stronger than the tube pulling pressure. The ram 21 is fitted into the end of the hollow adjusting screw shaft 18, and a ram fixing nut 22 is screwed into the male screw at the tip of the ram 21 and fixed to the hollow adjusting screw shaft 18.

  In addition, regarding the movement of the die 2 or the plug 4 during fixing or pipe drawing, as shown in FIG. 3, the hydraulic pressure from the first hydraulic unit 13 is supplied to the first hydraulic cylinder 20 through the pipe 14, and the first hydraulic pressure is supplied. The die 2 is driven by the cylinder 20. Further, as shown in FIG. 5, the hydraulic pressure from the second hydraulic unit 13a is supplied to the second hydraulic cylinder 20a through the pipe 14a, and the plug 4 is driven by the second hydraulic cylinder 20a. That is, the first hydraulic cylinder 20 in FIG. 3 is a hydraulic cylinder for driving a die, and the second hydraulic cylinder 20a in FIG. 5 is a hydraulic cylinder for driving a plug. The plug 4 is not shown in FIG. 5 because it is attached to the tip of the plug support bar 5.

  Here, the feature of the steel pipe drawing apparatus in the present embodiment is that, as shown in FIG. 5, a position detection sensor 20b is attached to the second hydraulic cylinder 20a for driving the plug. Specifically, the position detection sensor 20 b can be attached between the second hydraulic cylinder 20 a and the ram 21. The position detection sensor 20b constitutes a feedback loop of the control system, detects the stroke position of the second hydraulic cylinder 20a, feeds back a position detection signal to the computer, and corresponds to the stroke position of the second hydraulic cylinder 20a. Thus, the moving speed is controlled.

  At this time, since the drawing speed of the drawn steel pipe and the moving speed of the second hydraulic cylinder 20a are compatible (that is, a one-to-one correspondence), the stroke of the second hydraulic cylinder 20a is consequently obtained. The drawing speed of the drawn steel pipe is controlled according to the position. The position detection sensor 20b can be easily realized by, for example, an encoder.

  6 (a), 6 (b), and 6 (c) are longitudinal sectional views showing a drawing state by a die and a plug applied to the steel pipe drawing apparatus of the present invention, and FIGS. 7 (a), (b), ( c) is a longitudinal cross-sectional view illustrating a drawn steel pipe manufactured by the steel pipe drawing apparatus of the present invention. As shown in FIGS. 6A, 6B, and 6C, the plug 4 and the die 2 according to the present invention each have two-stage diameters. The tip of the flag 4 has a small bearing diameter d3 and a large bearing diameter d4 on the root side, and the die 2 constricts the material steel pipe 7 so as to face the bearing diameters d3 and d4 of the plug 4. A small bearing diameter d2 is formed on the side of the plug 4 in the root direction, and a large bearing diameter d1 for constricting the material steel pipe 7 is opposed to the large diameter bearing diameter d4 of the plug 4 on the distal end side of the plug 4. Forming.

  Accordingly, the inner and outer diameters of the drawn steel pipe 7b are determined by the bearing diameter d3 (small diameter) of the plug 4 and the bearing diameter d2 (small diameter) of the die 2, and the bearing diameter d4 ( 6B determined by the large diameter) and the bearing diameter d2 (small diameter) of the die 2, and the bearing diameter d4 (large diameter) of the plug 4 and the bearing diameter d1 (large diameter) of the die 2. The state shown in FIG. 6C to be determined can be formed.

  Next, a steel pipe drawing operation performed using the die 2 and the plug 4 using the above-described steel pipe drawing apparatus will be described. FIG. 7 is a longitudinal sectional view showing a state where the steel pipe is pulled out. FIG. 7A shows the die support base 30 on the left side fixed position explained in FIG. 3, and the support of the plug 4 on the right side fixed position explained in FIG. The material steel pipe 7 is dimensionally regulated by the bearing diameter d2 (small diameter) of the die 2 and the bearing diameter d3 (small diameter) of the plug 4 and formed.

  FIG. 6B shows a state in which the die support base 30 is fixed to the left side fixing position described in FIG. 3 and the support of the plug 4 is fixedly pulled out to the left side fixed abutting described in FIG. The material steel pipe 7 is dimensionally regulated by the bearing diameter d2 (small diameter) and the bearing diameter d4 (large diameter) of the plug 4 and formed.

  FIG. 6C shows a state in which the die support base 30 is pulled out while being fixed at the right fixed position described in FIG. 3 and the support of the plug 4 is fixed at the left fixed position described in FIG. The material steel pipe 7 is shown in a state of being dimensionally sized and formed by the diameter d1 (large diameter) and the bearing diameter d4 (large diameter) of the plug 4.

  That is, when the operations of FIGS. 6A, 6B, and 6C are continued in this order, a drawn steel pipe 7b shown in FIG. 7B is manufactured, and FIGS. 6A, 6B, and 6A are produced. ), The drawn steel pipe shown in FIG. 7 (a) is produced. If the work is continued in the order of FIGS. 6 (c), (b), (c), the drawn steel pipe shown in FIG. 7 (c) is produced. Is done. In order to move the support position of the die support 30 or the plug 4 during the drawing operation, the first hydraulic pressure incorporated in the interior is taken into consideration in relation to the drawing speed of the steel pipe and the moving speed of the die 2 or the plug 4. This is performed by the first hydraulic cylinder 20 driven by the unit 13 and the second hydraulic cylinder 20a driven by the second hydraulic unit 13a.

  By the way, when pulling out the material steel pipe, an excessive pulling force is applied to the core suspension bolt connected to the plug, and the core suspension bolt may be disconnected from the plug. That is, when a steel pipe is drawn out by a steel pipe drawing device, an excessive tensile force is applied in the process of moving from a thick part to a thin part of the steel pipe, so that the core suspension bolt (plug support bar 5 shown in FIG. 1) is cut from the plug. There is a risk of it. Hereinafter, the cutting phenomenon of the core suspension bolt will be described in detail with reference to the drawings.

  FIG. 8 is a cross-sectional view of an essential part showing a state in which a material steel pipe (work) is pulled out by a die and a plug using a general steel pipe drawing apparatus. As shown in FIG. 8, when the plug 4 is pulled in the right direction (the direction of arrow F) with respect to the raw steel pipe (workpiece) 31 constricted by the die 2 and the plug 4, the left side of the figure is fixed. A pulling force of F (for example, 100 tons) is applied to the core suspension bolt (plug support rod) 5 fixed by a member (not shown). At this time, the tensile force F applied to the core suspension bolt 5 increases as the thickness difference between the thick and thin portions of the steel pipe increases (that is, as the difference between d3 and d4 in FIG. 7A increases). In particular, since the core suspension bolt 5 becomes thinner as the material steel pipe having a smaller diameter is pulled out, the core suspension bolt 5 is easily cut when the steel pipe is pulled out.

  More specifically with reference to FIG. 8, when the workpiece 31 is drawn at a predetermined speed in order to generate a drawn steel pipe, a gap 32 is formed between the workpiece 31 and the plug 4 in the process of transition from the thick portion to the thin portion. As a result, a large tensile force F is applied to the core suspension bolt 5. As a result, the core suspension bolt 5 may be cut from the plug 4.

  Therefore, in the present invention, by using a floating die, the pulling force applied to the core suspension bolt when the workpiece is pulled out is reduced. The floating die is provided with a spring mechanism inside the die, and when a pressing force exceeding a predetermined value is applied to the die, the spring mechanism is pressed by the reaction force so that the pressing force of the die is reduced. It is composed of. Such a floating die is also called a double pressing die.

  FIG. 9 is a cross-sectional view showing a state in which a workpiece is pulled out using a floating die in the steel pipe drawing apparatus of the present invention. That is, FIG. 9 is a cross-sectional view of the main part showing a state in which the work 43 is pulled out by the floating die 41 and the multistage plug 42. As shown in FIG. 9, in the steel pipe drawing process, the work 43 abuts on the floating die 41 to limit the outer shape. At this time, the work 43 abuts on the floating portion 42 a of the plug 42 and the wall thickness increases. Limited. Finally, the work 43 is strongly bent to complete the forming of the drawn steel pipe.

  In such a steel pipe drawing apparatus using the floating die 41, the reaction force PN that the floating portion 42a of the plug 42 receives from the workpiece 43 is decomposed into a vertical vector component reaction force PS and a horizontal vector component reaction force PH. Can do. That is, the reaction force PN that the floating portion 42 a receives from the work 43 is a component of the force that only the horizontal vector component reaction force PH contributes to the pulling direction of the plug 42. In other words, the plug 42 is balanced in that the horizontal vector component reaction force PH received by the floating portion 42a from the work 43 and the force PZ in which the core suspension bolt (not shown) at the right end of the plug 42 is pulled in the pulling direction are balanced. Can be stopped. As a result, the pulling force applied to the core suspension bolt at the tip of the plug 42 is PH-PZ and is substantially zero. Therefore, in the steel pipe drawing process, there is no possibility that the core suspension bolt is cut from the plug in the process of moving from the thick part to the thin part of the steel pipe.

  Further, in such a steel pipe drawing apparatus using the floating die 41 and the plug 42, the outer diameter and the wall thickness of the work 43 are simultaneously limited (that is, the outer diameter and the wall thickness are determined by the floating die 41 and the plug 42). At the same time), the cross-section reduction rate (reduction) from the thick part to the thin part of the steel pipe can be increased. Furthermore, since the core suspension bolt is used only when the plug 42 is inserted when the steel pipe is pulled out, there is no possibility that a large tensile force is applied to the core suspension bolt during the steel pipe extraction. As a result, the diameter of the core suspension bolt can be reduced, so that a small diameter drawn steel pipe can be formed. In addition, since the thickness difference (for example, the difference between d3 and d4 in FIG. 7A) between the thick wall portion and the thin wall portion of the drawn steel pipe can be greatly increased, a stepped drawing with a large thickness change range. Steel pipes can also be formed. In other words, it is possible to easily form a drawn steel pipe in which the thickness of both end portions of the steel pipe is increased and the thickness of the intermediate portion is reduced as much as possible without cutting the core suspension bolt at the time of drawing the steel pipe.

  FIG. 10 is a cross-sectional view showing the longitudinal direction of a plug used with a floating die applied to the steel pipe drawing apparatus of the present invention. As shown in FIG. 10, this plug has a predetermined thickness portion D1 and a thickness A where the thickness of the drawn steel pipe is 8.5 mm, for example, and a taper having a predetermined taper angle θ1. Formed by a portion B, a thin portion C having a predetermined thin portion inner diameter D2 and a thickness of, for example, 6 mm, and a floating portion D having a predetermined floating angle θ2, and having a predetermined effective length at the tip portion A core suspension bolt portion E in which a screw 50 having L1 is formed is provided. That is, in the plug portion, the floating type portion H is formed by the thin portion C, the floating portion D, and the material tube inner diameter portion G.

  In the normal plug shape, the tensile force applied to the core suspension bolt E at the thin wall portion C is maximized. Therefore, as shown in FIG. 10, a floating portion D having a predetermined floating angle θ2 is formed from the end portion of the thin portion C. At this time, the steel pipe is drawn from the thick part A to the thin part C by providing the floating part D that has the optimum floating angle θ2 calculated according to the thickness difference between the thick part A and the thin part C. In some cases, the tensile force applied to the core suspension bolt portion E can be made substantially zero. This eliminates the possibility that the core suspension bolt E will be cut at the connection portion of the screw 50 when the steel pipe is pulled out.

  Here, the drawn steel pipe having a two-stage wall thickness has been described. However, the present invention is not limited to this, and it goes without saying that the present invention is applied to a drawn steel pipe having a plurality of wall thicknesses. Furthermore, the present invention has been described with reference to the above embodiment as a specific example. However, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention has been modified. It goes without saying.

  In the steel pipe drawing apparatus of the present invention, there is no possibility that the core suspension bolt will be disconnected from the plug when the steel pipe is drawn. Since it can be produced at low cost, it can be effectively used in the automobile industry, the construction machinery industry, and the like.

1 Frame 2 Die 3 Die Support 4 Plug 5 Plug Support Bar (Core Suspension Bolt)
5a collar part 6 plug support base 7 material steel pipe 7a tip part 7b drawn steel pipe 8 scissors 9 drawn car 10 claw 11 chain 12 truck 12a rail 13 first hydraulic unit 13a second hydraulic unit 14, 14a piping 15 die support base fixing ram 15b Large-diameter flange portion 16, 16a Stopper 17 Reinforcing material 17a Reinforcing member 18 Hollow adjusting screw shaft 19 Nut-type stopper 20 First hydraulic cylinder 20a Second hydraulic cylinder 20b Position detection sensor 21 Ram 22 Ram fixing nut 23 Pston rod 24 Ear metal 25 Pin 30 Die support base 32 Gap 41 Floating die 42 Plug 42a Floating part 43 Work 50 Screw d1 Large diameter bearing of the die d2 Small diameter bearing of the die d3 Small diameter bearing of the plug d4 Large diameter bear of the plug Ring A Thick part B Taper part C Thin part D Floating part E Core suspension bolt part G Material pipe inner diameter part H Floating type part L Total length L1 Effective length D1 Thick part inner diameter D2 Thin part inner diameter θ1 Taper angle θ2 Floating angle

Claims (4)

A floating die and a plug in which a floating region having a floating angle corresponding to the floating die is formed between the small diameter region and the large diameter region;
A steel pipe drawing apparatus characterized in that a stepped drawn steel pipe is manufactured by moving the floating die and the plug relative to each other in the forward and reverse directions with respect to the drawing direction of the material steel pipe.   The steel pipe drawing apparatus according to claim 1, wherein the floating angle is determined by a difference between a radius of the large diameter region and a radius of the small diameter region of the plug. A steel pipe drawing method by a steel pipe drawing device comprising a floating die and a plug in which a floating region of a floating angle corresponding to the floating die is formed between a small diameter region and a large diameter region,
When the floating die and the plug are moved relative to each other in the forward and reverse directions with respect to the drawing direction of the material steel pipe to produce a stepped drawn steel pipe from the material steel pipe,
A first step of forming a thick portion of the drawn steel pipe by relative movement of a small diameter region of the plug;
A second step of balancing a horizontal vector component of a reaction force received from the material steel pipe by the relative movement of the floating region of the plug and a pulling force in the pulling direction of the plug;
And a third step of forming a thinned portion of the drawn steel pipe by relative movement of the large-diameter region of the plug.   4. The steel pipe drawing method according to claim 3, wherein the floating angle is determined by a thickness difference between the thick part and the thin part.

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