JPS6372419A - Mandrel drawing method for tube - Google Patents

Abstract

PURPOSE:To eliminate use of a tension bar and to perform the mandrel drawing which reduces tube wall thickness deviations by drawing a tube stock so that the bearing face part of a plug stays in a range in which the bearing face part is opposite to the bearing face part of a die. CONSTITUTION:The top end of a tube stock A1 whose outer and inner surfaces are coated with a lubricant film is reduced by swaging and is inserted into a bearing face part 11 of a die 10, the projected part of the top end from the die 10 is chucked, and the stock A1 is drawn by a drawing means. A tube wall thickness of a worked tube A2 is determined by the difference between the respective bearing diameters D1 and d1 of the die 10 and a plug 20. On the other hand, the plug 20 is held at a proper position by a balance between forces acting on a bearing face part 21 of the plug 20 and a 2nd conical face part 23 due to the drawing.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to an improvement in the core drawing method for gA tubes.

(b) Conventional ti technique As shown in Fig. 2, as a conventional core drawing method,
The die 10 may be continuously drawn using a 70-ting method in which the drawing force on the tube and its reaction are balanced to the position where the plug 20 is formed, or a tension bar 30 may be placed inside the die 10 as shown in FIG. Ahead of 'I2
(There was a ball core method in which a smoothed plug 20 was inserted and the drawing process was performed.

(c) Problems that the invention attempts to resolve In the former case, the plug 20 automatically balances itself during extraction, so no tension bar is required, and R3 of the bearing surface 11 of the die can be short. Although it has the advantage of being able to be continuously drawn, the balance position of the plug changes depending on the approach angles a and β of the die 10 and the plug 20, the condition of the lubricating film attached to the inner and outer surfaces of the raw tube A1, and the drawing force. If this balance position is close to the drawing side, the tube thickness will be thin (but if it is closer to the opposite side, it will be thicker, so there was a drawback that it was difficult to determine the tube thickness.

In the latter case, the pipe thickness is constant due to the gap between the bearing surface of the die and the bearing surface of the plug, but since the tension bar will expand, the bearing surface of the die should be set to a length that can accommodate the expansion. It was necessary to do so, and continuous drawing was not possible, and the area reduction rate could not be increased with small diameter pipes.

The present invention does not require a tensioner except for the above-mentioned point m, and the plug balances at a fixed position with respect to the die. Further, it is an object of the present invention to provide a core drawing method that causes less variation in tube thickness.

(d) Means for solving problem α In order to achieve the above object, the present invention is implemented as follows. That is, in a core drawing method in which a pipe to be processed is drawn by interposing it between a die and a plug, the die has a pecking surface portion having a uniform inner diameter in the axial direction, and a pecking surface portion having a uniform inner diameter in the axial direction, and a core drawing method in which the pipe to be processed is drawn by interposing it between a die and a plug. The plug has a conical surface portion that is continuous in the opposite direction and has a larger diameter in the direction opposite to the direction in which the tube is pulled out, and the plug has a bearing surface portion that has a uniform outer diameter in the axial direction, and a conical surface portion that is continuous in the opposite direction to the direction in which the tube is pulled out. a first conical surface portion that is continuous with the die and has a small diameter in the direction opposite to the tube drawing direction; The pipe to be processed is pulled so that the bearing surface of the plug is within a range facing the bearing surface of the die.

(E) Action The force applied to the bearing surface of the plug during pipe removal and the
The force applied to the conical surface is balanced, and the plug is held in the proper position of the die, making it possible to perform high-speed drawing.

(f) Example The present invention will be described below based on embodiments shown in the drawings.

As shown in FIG. 1, the die 10 includes a bearing surface portion 11 having a uniform inner diameter in the axial direction, and a conical surface portion of the surface portion that continues in the opposite direction to the tube drawing direction and has a larger diameter in the opposite direction to the tube drawing direction. 12, and an auxiliary surface portion 13 formed of a conical surface that is continuous in the tube drawing direction and has a larger diameter in the tube drawing direction. The conical surface portion 12 has an approach angle a.

The plug 20 also includes a bearing surface portion 21 having a uniform outer diameter in the axial direction, and a first bearing surface portion 21 that is continuous in the direction opposite to the direction in which the tube is pulled out and has a smaller diameter in the direction opposite to the direction in which the tube is pulled out.
a conical surface section 22, a second conical surface section 23 which is continuous in the direction opposite to the tube drawing direction of the surface section and has a larger diameter in the direction opposite to the tube drawing direction; a first auxiliary surface portion 24 having a uniform outer diameter in the direction;
The second auxiliary surface portion 2 of the bearing surface 521 is a conical surface that is continuous in the tube drawing direction and has a smaller diameter in the tube drawing direction.
5 is formed. The second conical surface portion 23 has an approach angle β slightly smaller than the approach angle α of the die 10.
Furthermore, the maximum outer diameter d of the second conical surface portion 23 is set to satisfy the following relational expression with respect to the inner diameter (bearing diameter) D of the bearing surface portion 11 of the die 10.

cl, + 2 L≧D (where t is the thickness of the drawn pipe A2) For core drawing, use the raw pipe A with a lubricating film applied to the inner and outer surfaces in advance,
This is done by reducing the diameter of the starting end portion by swaging, inserting the starting end portion into the bearing surface portion 11 of the die, chucking the passing portion, and pulling it out using a draw means not shown. Then, depending on the difference in both bearing diameters, d, between the die 10 and the plug 20, the processed pipe A
2'l? Wt is determined. On the other hand, when the plug 20 is pulled out, the force applied to its bearing surface 1s21 and the force applied to the second conical surface portion 23 are balanced, so that
held in proper position. Further, the force applied to the second conical surface portion 23 depends on the approach angle β of the plug 20 with respect to the approach angle a of the die 10, but also changes depending on the lubrication state and the pulling force of the processed pipe A2.

In the present invention, since the constricted portion consisting of the first conical surface portion 22 and the second conical surface portion 23 is formed on the side opposite to the pulling direction of the bearing surface portion 21 of the plug, the constricted portion consisting of the first conical surface portion 22 and the second conical surface portion 23 is formed.
Appropriate balancing force is obtained by the action of the conical surface portion 23.

In order to apply a lubricating film to the inner and outer surfaces of the base pipe WA, the base pipe A is immersed in an oxalic acid solution and a stearic acid solution, and then dried.

The first In auxiliary surface portion 24 and the 12th In auxiliary surface portion 25 of the plug 20 may be omitted.

(G) Effects of the Invention As described above, the present invention provides a core drawing method in which the die has a bearing surface portion having a uniform inner diameter in the axial direction;
The plug has a conical surface part that is continuous in the direction opposite to the direction in which the pipe is pulled out and has a larger diameter in the direction opposite to the direction in which the pipe is pulled out. a first conical surface portion that continues in a direction opposite to the tube drawing direction and has a smaller diameter in the opposite direction to the tube drawing direction; and a conical surface portion of the die that continues in the opposite direction to the tube drawing direction of the surface portion and has a diameter opposite to the tube drawing direction. The plug has a second conical surface portion which has a larger diameter at a smaller approach angle, and the pipe to be processed is pulled out such that the bearing surface portion of the plug exists within a range facing the bearing surface portion of the die. Therefore,
No tension bar is required, and the plug balances at a fixed position with respect to the die, so there is no need to make the bearing surface ffW of the die long, and a large area reduction rate can be obtained even when drawing small diameter pipes, and the thickness can vary. As a result, a processed pipe with no cracks was obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a die and a plug used in the practice of the present invention, and FIGS. 2 and 3 are cross-sectional views, respectively, of the die and plug used in the practice of the conventional method. A1... Raw pipe, A2... Processed pipe, 10... Die, 11... Bearing surface part, 12... Conical surface part, 2
0...Plug, 21...Bearing surface part, 23...
・Second Cone Section Agent Patent Attorney Number of Strokes Keiichi Agent Patent Attorney Large Side New Figure 1 Figure 2

Claims (1)

[Claims] In a core drawing method in which a tube to be processed is drawn by interposing it between a die and a plug, the die 10 has a bearing surface portion 11 having a uniform inner diameter in the axial direction, and a bearing surface portion 11 having a bearing surface portion 11 having a uniform inner diameter in the axial direction, and a bearing surface portion 11 having a bearing surface portion 11 having a uniform inner diameter in the axial direction. The plug 20 has a conical surface portion 12 that continuously becomes larger in diameter in a direction opposite to the direction in which the pipe is pulled out.
A bearing surface portion 21 having a uniform outer diameter in the axial direction, a first conical surface portion 22 that continues in the direction opposite to the tube drawing direction of the surface portion and has a smaller diameter in the opposite direction to the tube drawing direction, and a It has a second conical surface section 23 which is continuous in the direction opposite to the tube drawing direction and has a larger diameter at a smaller approach angle than the conical surface section of the die, and the bearing surface section 21 of the plug 20 is connected to the die. 1. A method for core-drawing a tube, characterized in that the tube to be processed is pulled out so that the tube exists within a range facing a bearing surface portion 11 of No. 10.