JPH06269844A - Billet for hot extruding tube making - Google Patents

Abstract

PURPOSE:To restrain generation of uneven thickness without reduction of manufacturing efficiency not using a centering die by providing a specific large diameter part/parts on the front and/or rear end surface of a billet with which a seamless metallic tube is manufactured. CONSTITUTION:The outside surface of the billet 10 is constituted of a radius part 11, front end large diameter part 12, intermediate part 13, normal outside diameter part 14, intermediate part 15 and rear end large diameter part 16 from the front end side in the extruding direction. The constant outside diameter of both large diameter parts 12 and 16 is d1, that of normal diameter part 14 is d2 and the equations I and II are satisfied by values d1 and d2 corresponding to the inside diameter Dc of a container used for extruding. In the extruding method, axial deflection of the billet 10 from axial direction in the inside surface of container is restrained because of special shape of the outside surface of billet and, as the results, uneven thickness is restrained. Further, burning on the outside surface of the extruded tube is not generated when an enough glass lubricant is secured on the outside surface of billet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a billet as a raw material for producing a seamless metal tube by a glass lubrication extrusion method.

[0002]

2. Description of the Related Art The glass lubrication extrusion method, so-called Ugene
The Sejournet method is widely adopted as one of the methods for producing seamless metal pipes. The procedure for producing a seamless metal tube by the glass lubrication extrusion method will be described with reference to FIG.

First, a heated cylindrical billet 1 is loaded into a container 2 having a die 6 arranged on one end side by using a die holder 7 and a die backer 8. Then, the mandrel 3 is inserted into the billet 1 from the other end of the container 2 and the tip end thereof is concentrically inserted into the die 6,
The stem 5 is brought into contact with the rear end surface of the billet 3 via the dummy block 4, and the mandrel 3 and the stem 5 are advanced as they are. Since an annular gap is formed between the mandrel 3 and the die 6, the billet 1 is fully deformed (upset deformed) in the container 2 due to the pressing force from the stem 5, and then extruded forward from the annular gap. As a result, a seamless extruded pipe P is obtained. Glass powder is previously applied as a lubricant to the inner and outer surfaces of the billet 1, and a disk glass 9 obtained by pressing and compacting the glass powder is arranged on the front end surface of the billet 1 in the extrusion direction.

Since the cross-sectional dimensions (outer diameter, wall thickness) of the extruded pipe are determined by the inner diameter of the die 6 and the outer diameter of the mandrel 3, any size (outer diameter, wall thickness) can be obtained by exchanging the die 6 and the mandrel 3. This means that extruded tubes of (thickness) can also be manufactured.

As a problem in producing a seamless metal pipe by the glass lubrication extrusion method, there is a variation in wall thickness in the circumferential direction in each cross section of the extruded pipe, that is, so-called uneven thickness is generated. The causes of uneven thickness are considered to be non-uniform temperature distribution of the billet supplied to the extrusion process, or the tip of the mandrel being cantilevered to cause misalignment of the tip with respect to the container. .

As measures against uneven thickness, from the viewpoint of eliminating the non-uniform temperature distribution of the billet, various methods for uniform heating of the billet prior to extrusion, and the portion excluding the leading end and the trailing end of the billet There is proposed a method (Japanese Unexamined Patent Publication (Kokai) No. 55-128314) in which the outer diameter of the billet is made smaller than the outer diameters of the front end portion and the rear end portion to prevent the container from being uncooled in the circumferential direction.

From the viewpoint of preventing misalignment of the mandrel, the tip of the mandrel is inserted into a centering die, and the billet is upset-deformed in a sealed state, and then the centering die is replaced with an extrusion die. A method has been proposed in which the deformation of the billet during the extrusion is approximated to the axially symmetric deformation by performing the extrusion (Japanese Patent Publication No. 59-4206).

[0008]

However, as a practical matter, it is impossible to completely uniformly heat the billet, and it is difficult to avoid nonuniform cooling in the process of transporting the heated billet to the extrusion process. Therefore, it is not possible to expect significant results from the measures against uneven thickness from the viewpoint of eliminating the uneven temperature distribution of the billet.

On the other hand, the countermeasure for preventing the misalignment of the mandrel is effective even for the billet having some nonuniform temperature distribution. However, it is necessary to newly prepare a centering die, and the stem must be moved forward twice in one extrusion, so that a large reduction in production efficiency cannot be avoided.

An object of the present invention is to provide a billet for hot-extrusion pipe making, which does not use a new-type tool such as a centering die and can suppress the occurrence of uneven thickness without lowering the production efficiency.

[0011]

The billet for hot-extrusion pipe making of the present invention was developed by focusing on the following items.

The occurrence of uneven thickness is an indication that the billet deformation during extrusion is not axisymmetric.

In order to insert the heated billet into the container, an appropriate amount of difference (gap) is required between the inner diameter of the container and the outer diameter of the billet, and the axial center of the billet after being inserted into the container is due to this gap. It will be in a state of being displaced from the axis. When the upset is done with the axis misaligned, the billet is forced to deform unevenly inside the container, so during extrusion following upset, the mandrel cannot maintain its position concentrically with the container and uneven thickness occurs. To do.

When the gap between the billet and the container is reduced within the range where the billet can be inserted into the container, the deviation of the axial center of the billet and the container is geometrically suppressed, so that the uneven thickness is obviously improved. However, it has become clear that seizure occurs on the outer surface of the pipe during extrusion at a very high frequency above a certain limit. As a result of repeated studies, it has been found that this seizure is caused by the fact that when the billet is inserted into the container, the glass lubricant previously applied to the billet outer surface is scraped off by the inner peripheral end surface on the container entry side.

Further, as the difference between the billet inner diameter and the mandrel outer diameter is made smaller, the occurrence of axial misalignment between the billet and the mandrel is geometrically suppressed, so that the same effect of suppressing the uneven thickness can be obtained. It was found that when the gap between the billet and the container is sufficiently small, the effect of suppressing the uneven thickness can be further obtained, but it is clear that seizure occurs on the inner surface of the extruded tube at a very high frequency when the gap exceeds a certain limit. Became. It has been found that this inner surface baking also results from the fact that when the mandrel is inserted into the billet inner surface, the glass lubricant previously applied to the billet inner surface is scraped off by the mandrel.

From the above examination results, in order to suppress the uneven thickness, the gap between the billet and the container should be made as small as possible, and at the same time, the glass lubricant on the outer surface of the billet should not fall off, or the gap between the billet and the mandrel should be reduced. It is effective to make the glass lubricant as small as possible and prevent the glass lubricant on the inner surface of the billet from falling off. In order to further enhance the effect, both may be satisfied.

Therefore, the billet for hot-extrusion pipe manufacturing of the present invention is provided on the outer surface of the front end portion and / or the outer surface of the rear end portion of the billet, which is a material for producing a seamless metal tube by the glass lubrication extrusion method, as compared with other portions. diameter has a larger diameter portion, the outer diameter of該径most is _{0.5mm ≦ D c -d 1 ≦ 0.025D} c d 1 -d 2> 0.5mm D c: container internal diameter d _1: diameter Outer diameter when heated to most extrusion temperature d ₂ : Satisfies outer diameter when heated to extrusion temperature of the part excluding large diameter, or inside and / or after the billet tip The inner surface of the end portion has a small diameter portion having an inner diameter smaller than that of the other portion, and the inner diameter of the small diameter portion is 0.5 mm ≦ d ₁₀ −D _M ≦ 0.025D _C d ₂₀ −d ₁₀ > 0.5 mm D _c : container internal diameter D _M: mandrel OD d _10: small-diameter portion an inside diameter d ₂₀ in the state of being heated to the extrusion temperature: dividing the small diameter portion Or satisfies the internal diameter in a state of being heated to the extrusion temperature of the section, or assume having both these large-diameter portion and the small diameter portion.

[0018]

FIG. 2 shows an example of the billet for hot-extrusion pipe manufacturing of the present invention, and FIG. 3 shows the billet set in an extrusion apparatus. However, all the dimensions shown below are values at the time of extrusion.

The outer surface of the billet 10 is composed of an R portion 11, a large tip diameter portion 12, a connecting portion 13, a steady outer diameter portion 14, a connecting portion 15, and a large rear end diameter portion 16 from the front end side in the extrusion direction. .

The R portion 11 is a rounded portion having a radius of 10 to 20 mm, and is for preventing the joint between the billet front end face and the outer face from becoming a flaw during extrusion. Both the large front end diameter portion 12 and the large rear end diameter portion 16 have a constant outer diameter d.
₁ , the steady outer diameter portion 14 has a constant outer diameter d ₂ ,
The rear end large diameter portions 12 and 16 and the steady outer diameter portion 14 are connected to each other by the connecting portion 1.
It is connected smoothly by 3, 15. And
The outer diameters d ₁ and d ₂ satisfy the following condition with respect to the inner diameter D _{c of} the container used for extrusion.

[0021] _{0.5mm ≦ D c -d 1 ≦ 0.025D} c ────── (1) d 1 -d 2> 0.5mm ────── (2)

The reason for the D _c -d ₁ or less 0.025D _c is greater than 0.025D _c the billet 10 and the container 2
This is because the axis deviation of 0 becomes large and a sufficient uneven thickness suppressing effect cannot be obtained. Therefore, D _c −d _{1 is set} to 0.5 mm or more when the tip end and the rear end are smaller than 0.5 mm. Large diameter part 12,
This is because seizure frequently occurs in No. 16. Further, it is necessary to make d ₁ -d ₂ larger than 0.5 mm by allowing sufficient glass lubricant to exist between the steady outer diameter portion 14 and the container 20 and between the connecting portions 13 and 15 and the container 20 and extruding. This is to prevent seizure of the outer surface of the pipe.

The length L ₁ of the large-diameter portion 12 and the length L ₂ of the large-diameter portion 16 of the rear end are as long as the lower limit is long enough to geometrically support the billet 10 with respect to the container 20. However, the value is not particularly limited. However, for the upper limit value, suppose that the billet total length is calculated by the formula (1).
If a constant outer diameter d ₁ that satisfies the above condition is satisfied, the glass lubricant previously applied to the billet outer surface will be easily scraped off when the billet is inserted into the container, and seizure of the extruded tube outer surface will occur very frequently. , L ₁ and L ₂ are all preferably about 100 mm or less.

On the other hand, the inner surface of the billet 10 is composed of a small tip end diameter portion 17, a connecting portion 18, and a steady inner diameter portion 19.

The tip small diameter portion 17 has a constant inner diameter d ₁₀ and the steady inner diameter portion 19 has a constant inner diameter d _20.
8 are connected smoothly. The inner diameters d ₁₀ and d ₂₀ satisfy the following formulas with respect to the inner diameter dimension D _{c of the} container used for extrusion and the outer diameter D _{M of the} mandrel.

0.5 mm ≦ d ₁₀ −D _M ≦ 0.025 D _c ─────── (3) d ₂₀ −d ₁₀ > 0.5 mm ────── (4)

The reason for setting d ₁₀ -D _M to 0.025 D _c or less is that when it exceeds 0.025 D _c , the axis misalignment between the billet 10 and the mandrel 30 becomes large, and a sufficient effect of suppressing uneven thickness cannot be obtained. The reason why d ₁₀ −D _{M is set} to 0.5 mm or more is that if it is smaller than 0.5 mm, seizure occurs frequently in the small tip diameter portion 17. Also d ₂₀ -d
₂₀ is made larger than 0.5 mm in order to prevent the seizure of the inner surface of the extruded tube by allowing sufficient glass lubricant to exist between the steady inner diameter portion 19 and the mandrel 30 and between the joint portion 18 and the mandrel 30. Is.

The lower limit of the length L ₃ of the small tip end diameter portion 17 is not particularly limited as long as it is long enough to geometrically support the mandrel 30. However, for the upper limit value, suppose that the billet total length is calculated by the formula (3).
If a constant inner diameter d ₁₀ is satisfied, the glass lubricant pre-applied to the inner surface of the billet is easily scraped off when the mandrel is inserted into the billet, and seizure of the inner surface of the extruded pipe occurs at an extremely high frequency. ₃ and the rear end small diameter portion, the small diameter portion length is preferably about 100 mm or less.

The outer diameter d ₂ of the steady outer diameter portion 14 and the inner diameter d ₂₀ of the steady inner diameter portion 19 correspond to the outer diameter and inner diameter of the conventional billet, and the outer diameter d ₂ is D _c -d.
₂ is to be equal to or less than 0.05 D _c, and may be appropriately selected so as d ₂₀ -D _M is 15mm or less for the inner diameter d _20.

The billet 10 constructed as described above is
As shown in FIG. 3, after being inserted into the container 20, a pressing force by the stem 50 is applied from the rear end side through the dummy block 40, and is extruded forward from the gap formed by the mandrel 30 and the die 60 to form a joint. No extruded tube. In addition, 70 is a die holder, 80 is a die backer, and 90 is a disk glass.

In extrusion, due to the special outer surface shape of the billet 10, deviation of the axial center of the billet 10 from the axial center of the inner surface of the container 20 is suppressed, and uneven thickness is suppressed. Moreover, since sufficient glass lubricant is secured on the outer surface of the billet, seizure on the outer surface of the extruded pipe does not occur.

Moreover, the special inner surface shape of the billet 10 suppresses the deviation of the axial center of the billet 10 from the axial center of the mandrel 30, and as a result, the uneven thickness is further suppressed. Moreover, since sufficient glass lubricant is secured on the inner surface of the billet, seizure on the inner surface of the extruded tube does not occur.

Generally, the billet used for the glass lubrication extrusion is manufactured by machining the entire surface of the billet, and the billet of the present invention can be easily manufactured by machining. There is no significant increase in comparison, and since the extrusion operation is exactly the same as the conventional one, there is no reduction in production efficiency.

Table 1 shows variations of the billet of the present invention. ◯ means yes, x means no. As can be seen from Table 1, the billet of the present invention has 15 types of basic shapes.
The billet of No. 2 corresponds to No. 2.

The uneven thickness of the extruded tube often occurs remarkably on the front end side or the rear end side of the extruded tube, and it may be necessary to improve only one of them from the conventional one due to various needs during manufacturing. From this viewpoint, the billet 10 has large-diameter portions on the front end side and the rear-end side, but the large-diameter portion may be provided on only one of the front-end side and the rear-end side. Since the axis of the billet on the side where the large-diameter portion is provided is suppressed from being displaced from the axis of the inner surface of the container, the uneven thickness on this side is improved at least as compared with the case of using the conventional billet.

Further, the billet 10 has a small diameter portion 17 only on the front end side from the standpoint of suppressing uneven thickness on the front end side of the extruded pipe, but a similar small diameter portion is also provided on the rear end side for extrusion. The uneven thickness on the rear end side of the pipe may be further improved, or conversely, the small diameter portion may be provided only on the rear end side with an emphasis on suppressing the uneven thickness on the rear end side of the extruded pipe.

In any case, the large-diameter portion of the billet outer surface or the small-diameter portion of the inner surface geometrically restrains the misalignment of the axial center between the billet and the container or mandrel, so that uneven thickness is suppressed and the billet outer surface is kept steady. Since the outer diameter portion or the steady inner diameter portion of the inner surface secures sufficient glass lubricant to prevent seizure, an extruded tube in which uneven thickness is suppressed and seizure does not occur can be obtained.

[0038]

[Table 1]

Generally, the clearance between the container and the billet is 2.5% to 5.5% of the diameter of the container. At the extrusion heating temperature, this clearance may be 2.5% or less, for example, about 2%, but in this case, the outer surface of the billet is likely to be seized during extrusion, and a glass lubricant is applied to the steady outer diameter portion. There is a clear difference from the case of the secured billet of the present invention. In the billet of the present invention, 0.5 mm ≦ D _c −d
By satisfying ₁ and d ₁ -d ₂ > 0.5 mm, seizure does not occur even at 2.5% or less.

The clearance between the mandrel and the billet is generally set to 3 to 10 mm, which is about 2% to 4% when converted into a ratio to the container diameter.
However, if it is less than 2.5%, seizure is likely to occur,
Like the billet of the present invention, 0.5 mm ≦ d ₁₀ −D _M , d ₂₀ −
d ₁₀ > 0.5 mm is required.

On the other hand, the billet disclosed in the above-mentioned Japanese Patent Laid-Open No. 55-128314 has large diameter parts on the outer surfaces of both ends. However, the large diameter part was obtained by reducing the diameter of the part excluding both ends, and the outer diameter of the large diameter part at both ends is
It corresponds to the outer diameter of the steady outer diameter portion of the billet of the present invention. Therefore, any misalignment between the billet and the container cannot be eliminated.

On the other hand, a technique for separately providing large-diameter dummy portions on both end faces of the billet is disclosed in Japanese Patent Laid-Open No. 52-52855. However, its purpose is to prevent sideways flaws by preventing contact between the billet and the container, and no dimensional consideration is given to prevent misalignment between the billet and the container. The configuration is fundamentally different from that of the billet of the present invention in that a dummy material is used.

[0043]

EXAMPLES Examples and comparative examples of the present invention will be described below.

As an example of the present invention, ten billets A1 to A15 shown in FIGS. 4 and 5 were produced and subjected to hot extrusion. A1 to A15 are No. 1 to N in Table 1
Corresponds to o.15. Billet material is JIS-SU
S304, the billet temperature at the time of extrusion is 1200 ° C.
The outer diameter d ₁ of the large diameter portion at the front and rear ends is 180 mm, the outer diameter d ₂ of the steady outer diameter portion is 176.8 mm, the inner diameter d _{10 of the} small diameter portion at the front and rear ends is 39.86 mm, and the steady inner diameter portion is Inner diameter d ₂₀ is 4
It was 1.9 mm. Also, the billet length is 613 mm,
The length of the large diameter portion of the outer surface and the small diameter portion of the inner surface was 40.9 mm. The above dimensions are values at 1200 ° C.

On the other hand, the container inner diameter D _c is 181 mm, the mandrel outer diameter D _M is 38 mm, the die diameter is 46.6 mm, and d ₁ , d ₂ , d ₁₀ and d _{20 with} respect to D _c and D _M.
Satisfies the expressions (1) to (4).

Further, B1 to B3 shown in FIG. 6 for comparison.
D _1, the billet and A1 d _2, d _20, respectively 175.
The billets A1 'and A15 changed to 5 mm, 172.5 mm, and 41.9 mm have d ₂ , d ₁₀ , and d ₂₀ of 176.8 m, respectively.
Billet A1 changed to m, 43.4 mm, 44.4 mm
Tens of each 5'was produced and subjected to hot extrusion. A
In 1 ', D _cd becomes 5.5 mm, and 0.025 D _c (4.5
25 mm). The A15 'd ₁₀ -D _M 5.
4, which is still over 0.025D _c .

Table 2 shows the results of an examination of the occurrence of uneven thickness and seizure of the obtained extruded pipe.

As a method for investigating the uneven thickness, the thickness of the entire length is measured by an ultrasonic wall thickness measuring machine after cutting the leading end and the rear end of the obtained extruded pipe by 15 mm, and the maximum thickness at each axial position relative to the average thickness is measured. The ratio of the difference between the wall thickness and the maximum wall thickness was determined as the uneven thickness ratio (%) at each axial position. Referring to the obtained axial distribution of the wall thickness deviation, the maximum value of the wall thickness deviation for each half length on the tip side and the rear end side of the extruded tube is taken as the tip side / rear end side thickness deviation of the extruded tube. Take the average value of 10 bills for each billet No.
% Or less was marked with ⊚, 10 to 15% was marked with ◯, and more than 15% was marked with x.

The seizures were visually inspected, and the number of seizures for each billet number was shown in Table 2 as the seizure occurrence rate.

[0050]

[Table 2]

According to Table 2, A1 which is an embodiment of the present invention
All of A15 to A15 are good in both the uneven thickness rate performance and the seizure occurrence rate. Billets A5, A6, A9, A11, A1 in which large and small diameter parts are provided only on the front end side or the rear end side of the billet.
Also in A3 and A14, the uneven thickness ratio was improved on the side where the large and small diameter portions were provided.

In billets B1 and B2, the uneven thickness was good, but significant seizure was observed on the outer surface and the inner surface, respectively.
It was confirmed that the effect of retaining the glass lubricant on the inner and outer surface constant diameter portions of the present invention was obtained.

The billet B3 is a billet that has been used conventionally, and the uneven thickness which is a problem as a product was not recognized in the extrusion this time, but when judged comprehensively, it is more biased than the billets A1 to A15 according to the present invention. The result was inferior meat rate.

The billets A1 'and A15' have large-diameter and small-diameter portions, but because the dimensional consideration for preventing misalignment is not taken, the results are equal to or lower than those of the billet B3.

[0055]

INDUSTRIAL APPLICABILITY As described above, the hot-extrusion pipe billet of the present invention reduces the misalignment of the billet inside the container by the large diameter portion and the small diameter portion provided on the outer surface and the inner surface of the end portion. Therefore, a new type tool such as a centering die is not used, and it is possible to effectively suppress the occurrence of uneven thickness without lowering the production efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a seamless pipe by a gas la lubrication extrusion method.

FIG. 2 is a partially cutaway side view showing an example of a billet for hot extrusion pipe manufacturing of the present invention.

FIG. 3 is a cross-sectional view showing a state where the billet of FIG. 2 is set in an extrusion device.

FIG. 4 is a cross-sectional view showing the shape of the billet of the present invention used to demonstrate the effectiveness of the present invention.

FIG. 5 is a sectional view showing the shape of the billet of the present invention used for demonstrating the effectiveness of the present invention.

FIG. 6 is a cross-sectional view showing the shape of a comparative billet.

[Explanation of symbols]

 10 Billet 12 Large tip diameter portion 14 Steady outer diameter portion 16 Large rear end diameter portion 17 Small tip end diameter portion 19 Steady inner diameter portion 20 Container 30 Mandrel

Claims (3)

[Claims] 1. An outer surface of a tip portion of a billet, which is a material for producing a seamless metal tube by a glass lubrication extrusion method, and / or
Alternatively, the outer surface of the rear end portion has a large diameter portion having a larger outer diameter than other portions, and the outer diameter of the large diameter portion is 0.5 mm ≦ D _c −d ₁ ≦ 0.025 D _c d ₁ −d ₂ > 0. .5 mm D _c : Container inner diameter d ₁ : Outer diameter when heated to extrusion temperature of large diameter portion d ₂ : Satisfaction of outer diameter when heated to extrusion temperature of portions other than large diameter portion A billet for hot-extrusion pipe making. 2. An inner surface of a tip portion of a billet, which is a raw material for producing a seamless metal tube by a glass lubrication extrusion method, and / or
Alternatively, the inner surface of the rear end portion has a small diameter portion having an inner diameter smaller than that of the other portion, and the inner diameter of the small diameter portion is 0.5 mm ≦ d ₁₀ −D _M ≦ 0.025D _C d ₂₀ −d ₁₀ > 0.5 mm. D _c : Container inner diameter D _M : Mandrel outer diameter d ₁₀ : Inner diameter when heated to extrusion temperature of small diameter portion d ₂₀ : Satisfaction of inner diameter when heated to extrusion temperature of portion excluding small diameter portion A billet for hot-extrusion pipe manufacturing, which is characterized by: 3. The outer surface of the tip portion of a billet, which is a raw material for producing a seamless metal tube by a glass lubrication extrusion method, and / or
Alternatively, the outer surface of the rear end portion has a large diameter portion having a larger outer diameter than other portions, and the outer diameter of the large diameter portion is 0.5 mm ≦ D _c −d ₁ ≦ 0.025 D _c d ₁ −d ₂ > 0. .5 mm D _c : Container inner diameter d ₁ : Outer diameter when heated to extrusion temperature of large diameter portion d ₂ : Satisfaction of outside diameter when heated to extrusion temperature of portions excluding large diameter portion , The inner surface of the tip of the billet and /
Alternatively, the inner surface of the rear end portion has a small diameter portion having an inner diameter smaller than that of the other portion, and the inner diameter of the small diameter portion is 0.5 mm ≦ d ₁₀ −D _M ≦ 0.025D _C d ₂₀ −d ₁₀ > 0.5 mm. D _c : Container inner diameter D _M : Mandrel outer diameter d ₁₀ : Inner diameter when heated to extrusion temperature of small diameter portion d ₂₀ : Satisfaction of inner diameter when heated to extrusion temperature of portion excluding small diameter portion A billet for hot-extrusion pipe manufacturing, which is characterized by: