JP3237596B2 - Manufacturing method of seamless metal tube by hot extrusion tube method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a seamless metal pipe by a hot extrusion pipe manufacturing method represented by the Eugene Sejournet method, and more particularly, to a hot extrusion method having excellent dimensional accuracy of an outer diameter. The present invention relates to a highly efficient method for producing a seamless metal pipe as a product as it is.

[0002]

2. Description of the Related Art The dimensions of a seamless metal pipe manufactured by a hot extrusion pipe method represented by the above-mentioned Eugene Sejournet method are determined by an outer diameter of a bearing portion of a die and an inner diameter of an outer diameter of a mandrel. Is done. Here, the die and the mandrel are usually made of hot tool steel such as SKD61.

However, the outer diameter and the inner diameter of a seamless metal pipe that is actually extruded are mainly due to uneven temperature in a hollow billet as a material or temperature variation between hollow billets and a die as a tool. In addition to the variation in the axial direction of the pipe and each pipe due to a change in diameter during extrusion of the mandrel, cracks due to shearing may frequently occur.

For this reason, various countermeasures have conventionally been taken. For example, Japanese Patent Application Laid-Open No. Sho 60-68110,
Methods such as those disclosed in JP-A-9-4916 and JP-A-1-218715 have been proposed.

That is, in the method disclosed in Japanese Patent Application Laid-Open No. 60-68110, a dimension measuring means and a rolling roll stand are arranged on the exit side of a die, and an outer diameter detected by the dimension measuring means and a target outer diameter are determined. This is a method of rolling a tube extruded by a rolling roll stand on the basis of the deviation to eliminate variations in the outer diameter in the tube axis length direction.

In the method disclosed in Japanese Patent Application Laid-Open No. 59-4916, the basic extrusion speed mode is corrected in accordance with a predetermined temperature correction pattern based on the actually measured temperature of the hollow bite before processing, and after this correction, This is a method of suppressing the occurrence of cracks by extrusion molding in an extrusion speed mode.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 1-218715, various patterns of the extrusion speed in accordance with the material conditions (dimensions and temperature) of the hollow billet and the extrusion ratio are set in advance, and these patterns are set. This is a method of performing pattern control in accordance with the ram movement distance of the pipe making press based on the above, thereby suppressing unevenness in the circumferential direction of the top of the extruded pipe, variation in the dimension in the pipe axis length direction, and generation of cracks.

However, in any of the above-mentioned methods, if the extrusion ratio R is set to 40 or more and extrusion molding is performed in order to achieve more efficient production, dimensional variations in the axial direction of the extruded pipe, especially, The variation of the outer diameter becomes large, and the allowable range of the outer diameter is required to be, for example, within ± 0.5% of the target outer diameter, that is, the difference between the maximum outer diameter and the minimum outer diameter is required to be within 1%. There is a problem that a seamless metal tube which is a product as it is extruded cannot be industrially manufactured.

In general, the above extrusion ratio R is defined as follows when the inner diameter of the container is ID _C , the outer diameter of the mandrel is OD _M , and the inner diameter of the bearing portion of the die is ID _D (the unit is “mm”). It is a value defined by an expression.

R = (ID _C ² −OD _M ² ) / (ID _D ² −OD _M ² )

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above situation, and the problem is that even when extrusion molding is performed with an extrusion ratio R defined by the above formula of 40 or more,
The outer diameter variation range in the axial direction of the pipe is ± 0.5 of the target outer diameter.
It is an object of the present invention to provide a method capable of reliably manufacturing a seamless metal pipe having a diameter of less than 1%, that is, a diameter difference between a maximum outer diameter and a minimum outer diameter of 1% or less.

[0012]

The gist of the present invention resides in a method of manufacturing a seamless metal pipe by the following hot extrusion pipe manufacturing method.

A tool made of hot tool steel represented by SKD61
When extruding a seamless metal pipe by a hot extrusion pipe making method using a chair, when the extrusion ratio R is set to 40 or more and the ram speed of the pipe making press is set to V (m m / s), A method for producing a seamless metal pipe by a hot extrusion pipe-making method, wherein extrusion is performed under conditions satisfying the following formula.

8000 ≦ R × V ≦ 10000 where R = (ID _C ² −OD _M ² ) / (ID _D ² −OD _M ² ) where ID _C : container inner diameter (mm) OD _M : Mandrel outer diameter (mm) ID _D : Die bearing inner diameter (mm)

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made based on the following findings.

The dimensions (outer diameter and inner diameter) of the as-extruded pipe vary in the longitudinal direction of the pipe because of the unevenness of the temperature in the hollow billet, which is the material, or the temperature variation between the hollow billets, and the tool. Is caused by the diameter change during the extrusion of the die and the mandrel as described above.

[0017] Then, the outside diameter variation of the dimensional variation is primarily the inner diameter ID _D of the bearing portion B of the die shown in FIG. 1, the thermal expansion and wear, more die material itself approach portion A to the bearing portion B Occurs due to changes during the extrusion process due to inflow of plastic deformation.

However, when the extrusion ratio R is set at 40 or more, the plastic deformation of the approach portion A into the bearing portion B becomes remarkably remarkable. The change in the inner diameter ID _D is too large, and the allowable range of the outer diameter is ±
0.5% or less, that is, the difference between the maximum outer diameter and the minimum outer diameter is 1
It has been found that a tube which is within% cannot be obtained.

[0019] Here, the inner diameter ID _D of the bearing portion B of the die from becoming too large, as a die, a small thermal expansion coefficient as compared with the hot work tool steel typified by SKD61, and resistance to A high-nickel alloy die having excellent abrasion, high deformation resistance, and a small amount of plastic deformation in the approach portion A may be used. A high-nickel alloy die is a hot tool represented by SKD61. It is difficult to employ steel dies because they are significantly more expensive than steel dies, increase tool costs, and increase production costs of product tubes.

Therefore, the inventor of the present invention has proposed that when the extrusion ratio R is set to 40 or more and the extrusion is performed, the ram speed V of the tube-forming press is set at the bearing portion B of the hot tool steel die represented by SKD61. and effects on the phenomenon of the change in inner diameter ID _D, the effect on the outside diameter variation of the tube change behavior is extruded the inner diameter ID _D to investigate in detail, the following experiment was performed.

That is, when SUS304 hollow bilettes of various sizes are used to extrude into tubes of various sizes while changing the extrusion ratio R, the ram speed V ( mm / s) of the tube making press is set to After the change, the ram speed V during the extrusion was controlled to be constant, and the tube was produced.

[0022] Then, while examining the diameter difference △ ID _D before and after use of the inner diameter ID _D of the bearing portion B of the SKD61 steel die subjected to extrusion molding, continuous outer diameter in the axial direction of the resulting extruded tube And the diameter difference between the maximum value and the minimum value.
Examine the OD _P and find the diameter difference △ ID _D and △ OD _P , the diameter difference △ ID _D
And whether there was a correlation between the pressure and the extrusion ratio R and the ram speed V.

[0023] As a result, the diameter difference △ there is a correlation between the ID _D and △ OD _P, the diameter difference △ ID _D becomes ± 0.2 mm than the diameter difference △ OD _P is 1% of the target outer diameter Become super, diameter difference △
Diameter difference △ OD _P only when ID _D is ± 0.2 mm or less
Was found to be within 1% of the target outer diameter.

There is also a correlation between the diameter difference ΔID _D and the extrusion ratio R and the ram speed V. In the region where the extrusion ratio R is 40 or more, the product of the extrusion ratio R and the ram speed V is 8000. less than the diameter difference △ ID _D becomes -0.2mm than when, the diameter difference when the product value of the extrusion ratio R and the ram speed V is 10000 than △
It has been found that ID _D exceeds +0.2 mm.

FIG. 2 is a diagram showing the correlation between the diameter difference ΔID _D and the extrusion ratio R and the ram speed V. The horizontal axis shows the extrusion ratio R, and the vertical axis shows the ram speed V of the tube-forming press. the diameter difference △ ID _D is at ± 0.2 mm than when the × mark diameter difference △ OD _P was ± 1% greater than the target outer diameter, the diameter difference △ ID _D is ± 0.
The case where the diameter difference ΔOD _P is within ± 1% of the target outer diameter at 2 mm or less is indicated by a circle.

As can be seen from FIG. 2, in the region where the extrusion ratio R is 40 or more, the inner diameter ID _D of the bearing portion B of the die is determined.
The diameter difference before and after use ΔID _D is ± 0.2 mm or less, and the diameter difference ΔOD _P of the extruded tube becomes ± 1% or less of the target outer diameter.
When the product value of the extrusion ratio R and the ram speed V is 8000 or more,
It can be seen that it is the case of 0 or less.

Therefore, in the present invention, the extrusion ratio R is set to 4
When set to 0 or more, the extrusion conditions are set to “8000 ≦
R × V ≦ 10000 ”.

As described above, the extrusion conditions are determined by the equation “800
0 ≦ R × V ≦ 10000 ”, and then controlling the ram speed V of the tube-forming press during the extrusion by controlling the ram speed V as described in, for example, the above-mentioned Japanese Patent Application Laid-Open No. 1-218715. When extruded while holding constant using
The inner diameter ID _D of the bearing portion B of the die is ± 0.2 mm
It is possible to obtain a tube which is maintained below and has a diameter difference ΔOD _P between the maximum outer diameter and the minimum outer diameter which is within ± 1% of the target outer diameter.

[0029]

EXAMPLES Using a tube-forming press on which a die made of SKD61 was set, pipes were formed under the conditions shown in Table 1 for SUS304 hollow billets of various dimensions.

Then, the outer diameter of the obtained extruded tube was continuously measured in the longitudinal direction of the tube, and the diameter difference ΔOD _P between the maximum outer diameter and the minimum outer diameter was obtained. Further, the inner diameter ID _D of the front and rear bearing portions B use of the die subjected to the extrusion was measured and examined before and after use diameter difference △ ID _D.

The results are shown in Table 1 together with the pipe making conditions.

[0032]

[Table 1]

As is apparent from the results shown in Table 1, the product of the extrusion ratio R and the ram speed V is 800 according to the method of the present invention.
When the extrusion was performed at a ram speed V falling within the range of 0 to 10000 (test numbers 2, 6, 10, and 14), the extrusion die R was in each case irrespective of the extrusion ratio R of 40 or more. A tube in which the diameter change before and after use of the inner diameter ID _D of the bearing portion B is kept at ± 0.2 mm or less, and the diameter difference ΔOD _P between the maximum outer diameter and the minimum outer diameter is within ± 1% of the target outer diameter. was gotten.

On the other hand, when extrusion is performed at a ram speed V in which the product value of the extrusion ratio R and the ram speed V is out of the range of 8000 to 10000, the inner diameter ID _D of the bearing portion B of the die is in each case. ± 0.2 diameter change before and after use
mm, and only pipes having a diameter difference ΔOD _P between the maximum outer diameter and the minimum outer diameter exceeding ± 1% of the target outer diameter could be obtained.

In the reference examples (test numbers 16 and 17) in which the extrusion ratio R is 23.35 and less than 40, even though the product of the extrusion ratio R and the ram speed V is less than 8000, Also in the case of the inner diameter I of the bearing part B of the die
Diameter change amount before and after the use of D _D is kept below ± 0.2 mm, a tube diameter difference △ OD _P between the maximum outer diameter and the minimum outer diameter is within ± 1% of the target outer diameter was obtained.

This is because when the extrusion ratio R is less than 40,
Unlike the case where the extrusion ratio R is 40 or more, the inner diameter ID of the bearing portion B of the die is independent of the ram speed V.
The diameter change before and after use of _D is kept at ± 0.2 mm or less,
Diameter difference between maximum outer diameter and minimum outer diameter △ OD _P is ± 1 of target outer diameter
% Of tubes is obtained.

[0037]

According to the method of the present invention, the diameter difference ΔOD _P between the maximum outer diameter and the minimum outer diameter in the extruded state is ± 1% of the target outer diameter.
By setting the extrusion ratio R to 40 or more, it is possible to produce a tube with high efficiency. As a result, it is possible to inexpensively provide a product pipe having excellent outer diameter dimensional accuracy while being extruded.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a die.

FIG. 2 is a diagram showing the effect of a diameter difference ΔID _D , an extrusion ratio R, and a ram speed V on a diameter change of a bearing portion of a die and an extruded tube in a tube axial direction.

[Explanation of symbols]

 A: Approach part B: Bearing part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-192724 (JP, A) JP-A-59-4916 (JP, A) JP-A-60-68110 (JP, A) JP-A-1- 218715 (JP, A) JP-A-7-185646 (JP, A) JP-A-9-192724 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 31/00

Claims (1)

(57) [Claims] 1. A hot work tool steel die represented by SKD61.
When extruding a seamless metal pipe by a hot extrusion pipe making method using a chair, when the extrusion ratio R is set to 40 or more and the ram speed of the pipe making press is set to V (m m / s), A method for producing a seamless metal pipe by a hot extrusion pipe-making method, wherein extrusion is performed under conditions satisfying the following formula. Where 8000 ≦ R × V ≦ 10000 ···· , R = (ID C 2 -OD M 2) / (ID D 2 -OD M 2) However, ID _C: Container internal diameter (mm) OD _M: mandrel out Diameter (mm) ID _D : Inside diameter of die bearing part (mm)