JPS63235020A - Manufacture of hot extruded tube - Google Patents

Abstract

PURPOSE:To reduce the expansive tendency at the tube bottom part by detecting a diameter expansion amount at the tube bottom part generated by a mandrel remained in the bottom part after tube manufacture finishing and using a mandrel provided with a expanded head by a size corresponding to a diameter expansion amount. CONSTITUTION:A diameter expansion amount of the bottom part generated by temporarily remained mandrel in the bottom part of a tube P is detected by comparing the amount with a diameter of the top and intermediate parts of the tube P. A mandrel 4, provided with a head 4b having a diameter corresponding to the expansion amount or a larger diameter than the corresponded diameter at the top end of the mandrel 4, is used to hot extrude the tube P. Therefore, a part facing the head 4b is cooled with the inside diameter of the facing part restrained from contraction and other parts contract to a position being in contact with the peripheral surface of a body part 4a without restraint. An extent of expansion is reduced by contraction after temporary expansion when the mandrel 4 is later pulled out because an endothermic amount is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hot extrusion pipe manufacturing method for manufacturing seamless pipes by hot extrusion molding a hollow billet.

[Prior art]

FIG. 5 is a schematic diagram showing the implementation state of the hot extrusion pipe manufacturing method according to the conventional method, in which the die 22 is arranged using the die holder 26 so as to face the opening on one end side of the accommodating part 21c in the center of the container 21. At the same time, the glass disk 27, the heated hollow billet 23, and a dummy block (not shown) are charged in this order into the housing part 21c from the opening on the other end side of the housing part 21c, and the dummy block, hollow billet 23, Glass disk 27 and the die 22
The mandrel 24 is placed with its tip protruding further forward of the die 22, and the hollow billet 23 is pressurized from the other end side via a dummy block by a stem (not shown) to create a gap between the die 22 and the mandrel 24. The hollow billet 23 is extruded through the annular space to produce a seamless pipe P.

[Problem that the invention seeks to solve]

By the way, in such a method, a part of the hollow billet 23 charged into the container 21 is stored as lees in the storage section 21c.
Most of what remains inside is extruded and formed into a tube, but when extrusion is finished, the mandrel 24 is temporarily left behind in the bottom of the manufactured tube P. Therefore, while other parts of the pipe P, such as the top and middle parts, contract as they cool, the bottom part of the pipe P is cooled with its inner diameter restrained by the mandrel 24. There was a problem that both the inner and outer diameters were larger than the top and middle parts, resulting in variations in dimensional accuracy.

The inventors of the present invention found that the above-mentioned problem occurs at the bottom of the tube.

As a result of experiments and research to eliminate the phenomenon of outer diameter expansion,
The head part has a larger diameter than other parts by a dimension corresponding to the increase in the inner diameter or outer diameter of the bottom part caused by the mandrel 24 being temporarily left behind at the bottom part of the pipe P. It was found that using a mandrel prepared for this is effective in suppressing the diameter expansion phenomenon.

Note that a technique for attaching a portion having a larger diameter, for example, a plug to the tip of the mandrel has been proposed in the past (Japanese Patent Laid-Open No. 14436/1983). However, this conventional technology is only aimed at expanding the diameter of the pipe, and is different from the technology of the present invention, which aims to eliminate local diameter variations that occur at the bottom of the pipe. Needless to say.

The present invention was made based on this knowledge, and its purpose is to reduce the phenomenon of expansion of the inner and outer diameters that occurs at the bottom of the tube, and to improve dimensional accuracy.

An object of the present invention is to provide a hot extrusion pipe manufacturing method that can improve yield.

[Means for solving problems]

In the method of the present invention, the amount by which the bottom portion is expanded due to the mandrel being left behind in the bottom portion of the tube at the end of tube manufacturing is detected in advance by comparing it with the diameters of the top and middle portions of the tube. However, a mandrel is used which has a head portion at its front end whose diameter is expanded by a size corresponding to or larger than this amount of diameter expansion.

[Effect]

According to the method of the present invention, when the mandrel is pulled out from the bottom part of the tube, it is formed to the target dimension by the middle expansion action of the head part of the mandrel, and the diameter expansion of the bottom part can be reduced.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a schematic diagram showing the implementation state of the present invention, and FIG. 2 is a partially enlarged view showing the head portion of the tip of the mandrel used in the method of the present invention. In the figure, 1 is a container, 2 is a die, and 3 is a hollow. 4 indicates a billet, 4 indicates a mandrel, and 5 indicates a stem. The container 1 is equipped with a container IC surrounded by a liner 1a fixed by a liner holder 1b at its center, and the die 2 is placed in the container by using a die holder 6 and a diver socket 6a, facing the opening at one end of the container IC. A mandrel 4 and a stem 5 held by a mandrel holder 7 are arranged concentrically on the other end opening side of the housing part 1c, and each is supported by a water pressure or hydraulic cylinder so as to be movable back and forth individually. has been done.

The mandrel 4 consists of a cylindrical main body part 4a and a short cylindrical head part 4b integrally formed at the tip thereof, and the head part 4b is formed to have a slightly larger diameter than the main body part 4a. There is. The diameter of the head portion 4b is at least larger than the diameter of the main body portion 4a when manufacturing tubes with the same inner diameter, as shown in FIG. It is set to a dimension corresponding to ΔD or a dimension larger than this. Of course, the upper limit does not exceed the hole diameter of the die 2.

Front end surface of head portion 4b, peripheral edge of rear end surface, and main body portion 4a
All joints are chamfered to create smooth curved surfaces.

Note that although the case where the head portion 4b is constructed integrally with the main body portion 4a is shown, the present invention is not limited to this. For example, as shown in FIG. 3, the head portion 4b may be formed separately from the main body portion 4a, and the head portion 4b A screw rod may be provided on the rear end surface, and a screw hole may be provided on the distal end surface of the main body portion 4a, so that the head portion 4b is screwed and fixed to the main body portion 4a.

The hollow billet 3 is formed by drilling a core hole 3a in advance by mechanical processing or press processing, and after being heated to a predetermined temperature, the glass disk 8, the hollow billet 3, and the dummy block 9 are individually formed in this order. Alternatively, the hollow billet 3 is simultaneously inserted into the housing part lc of the container 1 while being inserted through the mandrel 4, and the hollow billet 3 is first pressurized by the stem 5, and then the hollow billet 3 is inserted into the annular shape between the die 2 and the mandrel 4. The hollow billet 3 is extruded through the space and formed into a pipe P.

At the end of pipe manufacturing, the tip of the mandrel 4 including the head 4b is temporarily left in the bottom of the pipe P as in the past, and the part facing the head 4b is cooled with its inner diameter constrained. However, other parts can contract without being restrained until they touch the circumferential surface of the main body part 4a, and the amount of heat removed is small. The extent of the expanded diameter state is reduced by the contraction of the diameter.

Next, the results of a comparative test between the method of the present invention and the conventional method will be explained.

[Comparative test 1] The test used a hollow billet with an outer diameter of 2851 m as a test material.
By using the method of the present invention and the conventional method, the outer diameter is 167 mm and the inner diameter is 1 mm.
55B with a wall thickness of 6.5mm, and the inner diameters of the seamless pipes manufactured by the method of the present invention and the conventional method were measured at each part in the axial direction from the top and bottom to the center.

Results ■As shown in Table 1. In addition, X in Table 1
The value of indicates the increase/decrease value with respect to the target inner diameter, and λ indicates the deviation. Further, FIG. 4 is a graph of Table 1. In addition, in the method of the present invention, the length of the mandrel is 140 mm.
0 dragon, head diameter 154.5 *■, body diameter 1
53mm, and the conventional method has a length of 1400m,
A straight piece with a diameter of 154.5 mm was used.

In the graph shown in Figure 4, the horizontal axis represents the axial dimension (tm) from the top and bottom of the tube to the center, and the vertical axis represents the average inner diameter (average of the values at 6 points in the circumferential direction). This is a great indication. The solid line in the graph shows the results of the method of the present invention, and the broken line shows the results of the conventional method.

As is clear from this graph, when the method of the present invention is used, the increase in the outer diameter dimension at the bottom portion of the tube is significantly reduced.

[Comparative test 2] The test used a hollow billet with an outer diameter of 240 m as the test material.
Target dimension outer diameter 65ui± by the method of the present invention and the conventional method
1%, inner diameter 291 m": 0.6%, and wall thickness 18 mm. A seamless pipe was manufactured with a wall thickness of 18 mm. Inside and outside of each of the middle and bottom parts of the seamless pipe were separated from each other in the axial direction. The diameter was determined in two mutually orthogonal directions (cross directions).

In addition, in the method of the present invention, the head diameter of the mandrel is 29w.
m, body part 27.5n+, die hole diameter 65.1 vns
In addition, in the conventional method, the mandrel diameter is 29mm and the die hole diameter is 6mm.
6.3 Tsuru products were used.

The results are shown in Table 2. In the table, Y indicates the average value and λ indicates the deviation. As is clear from Table 2, when using the conventional method, the difference in inner diameter between the middle part and the bottom part is large;
In addition, the outer diameter shows a value close to the upper limit of the allowable range, but when the method of the present invention is used, the inner diameter of the middle part and the bottom part is small, and the outer diameter has a sufficient margin within the allowable range. I understand that there is.

(Margins below) [Effects] As described above, in the method of the present invention, the head portion is expanded in diameter at least by an amount corresponding to the diameter expansion amount of the bottom portion of the tube determined in advance, or larger than this amount. Since pipe manufacturing is carried out using a mandrel with The present invention has excellent effects such as:

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the implementation state of the method of the present invention, Fig. 2 is the same (enlarged view of the tip of the mandrel, Fig. 3 is an enlarged view showing another aspect of the mandrel used in the method of the present invention, Fig. 4) is a graph showing the comparative test results between the method of the present invention and the conventional method, and FIG. 5 is a schematic diagram showing the implementation state of the conventional method. 1...Container 1c...Accommodating part 2...Die 3
...Hollow billet 4...Mandrel 4a...
Main body part 4b...Head part 5...Stem agent Patent attorney Noboru Kono

Claims (1)

[Claims] 1. Load the heated hollow billet into the storage part of a container with a die arranged in the opening at one end, and insert the mandrel through the hollow billet and the die from the other end of the storage part with the tip protruding forward. In the method of extruding the hollow billet between a die and a mandrel to form a pipe, the amount by which the diameter of the bottom part is enlarged due to the mandrel being left behind in the bottom part of the pipe at the end of pipe production is It is characterized by using a mandrel equipped with a head part at the front end whose diameter is enlarged by a dimension corresponding to or larger than the diameter of the top part and middle part of the mandrel, which is detected in advance by comparing with the diameter of the top part and middle part of the mandrel. A hot tube extrusion manufacturing method.