JP2021010913A - Pipe expander and method for manufacturing steel pipe - Google Patents

Abstract

To provide a pipe expander and a method for manufacturing a steel pipe, capable of preventing seizure on the contact surface between the cone and the outer peripheral member of the pipe expanding head, reducing wear of the cone so as to reduce a frequency of replacement, and manufacturing a steel pipe at low cost.SOLUTION: A pipe expander for expanding a steel pipe comprises: a cone with size of an outer periphery gradually changing in an axial direction; and a pipe expanding head outer peripheral member contacting the outer periphery of the cone. In the pipe expander, micro dimples are formed in a contacting surface between the pipe expanding head outer peripheral member and the cone.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pipe expander used for manufacturing a welded pipe such as a UOE steel pipe, and a method for manufacturing a steel pipe using the pipe expander.

Generally, in the manufacture of a welded pipe typified by a UOE steel pipe, after welding the inner and outer surfaces of the pipe, the roundness and straightness deteriorate due to the residual stress due to the heat effect of the welding. Therefore, in order to remove the residual stress and correct the roundness and straightness, the pipe is expanded.

This tube expansion is described in, for example, Non-Patent Document 1. 1 (a) and 1 (b) are transcriptions of the figures disclosed in Non-Patent Document 1. FIG. 1A is a diagram showing a configuration of a tube expander, and FIG. 1B is a diagram showing a configuration of a tube expansion head.

As shown in FIG. 1A, the pipe expander 100 has a pipe expander main body 14 including a cylinder 11, a horn 12, and a pipe expansion head 13, an axial in-feed 15, and a cross-feed 16. ..

The cylinder 11 is a power source for expanding the outer circumference of the tube expansion head 13, and the horn 12 holds the tube expansion head 13. The pipe expansion head 13 plays a role of expanding the diameter of the steel pipe 1 from the inside by expanding the outer circumference in the radial direction.

As shown in FIG. 1B, the tube expansion head 13 is composed of a cone 17 and a tube expansion head outer peripheral member 18. The tube expansion head outer peripheral member 18 is composed of a jaw 19 and a die 20. The jaw 19 is a member that comes into contact with the cone 17, and the die 20 is a member that comes into contact with the steel pipe 1 and expands the diameter of the steel pipe 1 from the inside. However, the jaw 19 and the die 20 may be configured as an integral member. The cone 17 is connected to the cylinder 11 and fitted to the tip of the draw bar 21 passed through the inside of the horn 12. The cone 17 has a shape in which the size of the outer circumference gradually changes in the axial direction. “The size of the outer circumference gradually changes” means that the shape seen from the cross section is tapered. For example, the cone 17 can have a pyramidal trapezoidal shape.

The jaw 19 is arranged on the outside of the cone 17 in a shape along the outer circumference of the cone 17. The jaw 19 is composed of a plurality of segments so that the outer circumference of the cone 17 can be expanded or contracted along the outer circumference thereof. The number of segments is arbitrary, but the larger the number of segments, the closer the outer circumference approaches the shape of a circle.

Further, a lubricating oil supply pipe 22 passes through the inside of the pipe expansion head 13, and supplies lubricating oil to the contact surface in order to prevent seizure of the contact surface between the cone 17 and the pipe expansion head outer peripheral member 18. ing.

In the pipe expander 100 configured in this way, the steel pipe 1 subjected to submerged arc welding from the inner and outer surfaces is conveyed to a position where the axis of the pipe expander main body 14 and the axis of the steel pipe 1 coincide with each other by the cross feed 16. .. The axial in-feed 15 conveys the steel pipe 1 conveyed by the cross-feed 16 in the axial direction and pushes it toward the tube expander main body 14. In the tube expander main body 14, the cone 17 moves in the axial direction so that the cone 17 and the tube expanding head outer peripheral member 18 ride on each other on the contact surface (wedge action). At this time, since the outer peripheral member 18 of the tube expansion head is restrained from moving in the axial direction by the horn 12, they are displaced in the radial direction. As a result, the outer peripheral member 18 of the pipe expanding head expands radially toward the radial direction of the shaft, the steel pipe 1 is expanded from the inside, and the diameter of the steel pipe 1 is expanded. In FIG. 1, the arrow indicates the direction of displacement.

In such a pipe expanding process, there is a problem of slidability at the contact surface between the cone and the pipe expanding head outer peripheral member when they ride on each other due to the wedge action. In recent years, the strength of steel pipes has increased, an excessive force is applied when the cone is pulled in the axial direction, and the surface pressure generated on the contact surface between the cone and the outer peripheral member of the pipe expansion head has also increased. At this time, seizure occurs on the contact surface of the cone and the outer peripheral member of the tube expansion head, which often causes a problem that the tube cannot be expanded, and maintenance of the contact surface of the cone and the outer peripheral member of the tube expansion head is required.

On the other hand, Patent Document 1 proposes that the surface layer of the cone is subjected to nitriding treatment to form a cured layer having a depth of 0.05 to 1.5 mm. Further, Patent Document 2 proposes that the hardness of the segment (corresponding to the above-mentioned jaw) is HRC45 to 52, and the surface is subjected to sulfurizing and nitriding treatment. Patent Document 3 proposes supplying lubricating oil containing silica particles to the contact surfaces of the cone 17 and the tube expansion head outer peripheral member 18 in order to prevent seizure on the contact surfaces of the cone 17 and the tube expansion head outer peripheral member 18. ing. Patent Document 4 proposes having a removable liner on the surface of the cone 17 and using a copper alloy for the liner component.

Japanese Unexamined Patent Publication No. 01-299723 Japanese Unexamined Patent Publication No. 05-195158 Japanese Unexamined Patent Publication No. 2007-284519 Japanese Patent No. 6288273

Steel Handbook Volume 3 (2), 4th Edition, Sections 12.4.6

Patent Document 1 and Patent Document 2 indicate that the surface of the cone or the outer peripheral member of the tube expansion head is hardened. However, the effect of preventing seizure on the contact surface due to hardening is not clear, and seizure on the contact surface cannot be sufficiently prevented. Further, it may be difficult to prevent the occurrence of seizure because the silica particles adhere unevenly on the contact surface only by supplying the lubricating oil containing the silica particles as in Patent Document 3. Further, when seizure occurs on the contact surface, the cone and the outer peripheral member of the pipe expansion head must be replaced, and since the cone is particularly expensive, the replacement of the cone increases the manufacturing cost of the steel pipe.

As in Patent Document 4, attaching a liner to the surface of the cone is effective in preventing seizure, but since the copper alloy of the liner member is worn, it becomes necessary to frequently replace the liner member. The production efficiency of steel pipes will decrease.

The present invention has been made in response to such a problem, and by preventing seizure on the contact surface between the cone and the outer peripheral member of the pipe expansion head and reducing the wear of the cone, the frequency of replacement thereof can be reduced. An object of the present invention is to provide a pipe expander capable of manufacturing steel pipes at low cost and a method for manufacturing steel pipes.

The inventors have conducted extensive research to achieve the above-mentioned problems. As a result, they have found that the above problems can be solved by applying micro dimples to the contact surface between the cone and the outer peripheral member of the tube expansion head, and have completed the present invention. More specifically, the present invention provides the following.
[1] A cone whose outer circumference gradually changes in the axial direction,
A pipe expander for expanding a steel pipe having a pipe expansion head outer peripheral member that contacts the outer circumference of the cone.
A pipe expander characterized in that micro dimples are formed on a contact surface between the outer peripheral member of the pipe expansion head and the cone.
[2] The tube expander according to [1], wherein the micro dimples are micro dimples produced by shot blasting.
[3] The tube expander according to [1] or [2], wherein the arithmetic average roughness Ra on the contact surface between the tube expanding head outer peripheral member and the cone is 0.3 to 1 μm.
[4] A method for manufacturing a steel pipe, which comprises expanding the steel pipe by using the pipe expander according to any one of [1] to [3].

According to the present invention, it is possible to reduce the sliding resistance of the contact surface between the cone and the outer peripheral member of the tube expansion head, prevent seizure, and suppress wear on the contact surface. As a result, the frequency of replacement of the cone and the outer peripheral member of the pipe expansion head can be significantly reduced, and the manufacturing cost of the steel pipe can be reduced.

FIG. 1A is a schematic view showing the configuration of a conventional tube expander, and FIG. 1B is a schematic view showing the configuration of a tube expansion head outer peripheral member. FIG. 2 is a schematic view showing a tube expanding head outer peripheral member of the tube expanding machine of the present invention. FIG. 3 is a scanning electron microscope image showing the shape of the surface (ground surface) of the conventional tube expansion head outer peripheral member. FIG. 4 is a scanning electron microscope image showing the shape of the surface (shot blast surface) of the outer peripheral member of the tube expansion head of the present invention. FIG. 5 is a diagram comparing the prior art and the present invention with respect to the sliding resistance coefficient of the tube expander.

Hereinafter, embodiments of the present invention will be described with reference to FIG. FIG. 2 is a schematic view showing an example of a tube expanding head outer peripheral member of the tube expanding machine of the present invention. The present invention is not limited to the following embodiments.

The present invention is characterized in that micro dimples are formed on the contact surface between the outer peripheral member of the tube expansion head and the cone. Specifically, micro dimples are formed on the contact surface between the cone 17 of the present invention and the tube expansion head outer peripheral member 18, that is, the contact surface between the cone 17 and the jaw 19.

Microdimples are a collection of crater-like dents formed on the solid surface by the action of local impact force such as particles colliding with the solid surface. The surface of such microdimples has a high ability to retain lubricating oil. Therefore, in the present invention, the effect of preventing seizure can be obtained by reducing the sliding resistance on the contact surface between the cone 17 and the tube expansion head outer peripheral member 18 and preventing metal contact.

FIG. 3 is a scanning electron microscope image showing the surface of a conventional jaw (grinding finish), and FIG. 4 is a scanning electron microscope image showing the surface of the jaw of the present invention (shot blasting). The surface of the conventional jaw of FIG. 3 is a surface processed by a grinding finish (referred to as a "ground surface"). As can be seen from FIG. 3, the surface of the conventional jaw has a linear uneven shape, and the lubricating oil cannot be held by the pocket-shaped depression. For this reason, metal contact is likely to occur on the contact surface, and seizure has occurred. On the other hand, the surface of the jaw of the present invention in FIG. 4 is in the state of microdimples having a large number of recessed recesses as compared with the ground surface. In this case, a large amount of lubricating oil is held by the micro dimples as compared with the ground surface. Therefore, metal-to-metal contact does not occur at the interface between the jaw and the cone, and the oil film is sufficiently retained, so that seizure does not occur.

Here, in the present invention, the depth of the hollow of the micro dimples is preferably 5 to 10 μm, and the outer diameter when viewed from the surface is preferably 5 to 100 μm. If the depth of the dent is less than 5 μm or the outer diameter when viewed from the surface is less than 5 μm, it is not possible to secure the oil retention property required to prevent seizure on the contact surface between the cone 17 and the outer peripheral member 18 of the pipe expansion head. .. On the other hand, if the depth of the dent exceeds 10 μm or the outer diameter when viewed from the surface exceeds 100 μm, the dent portion is not filled with lubricating oil, so that the contact surface between the cone 17 and the outer peripheral member 18 of the tube expansion head Sliding resistance will increase. However, the shape of each indentation does not necessarily have to be circular when viewed from the solid surface, and includes those having a polygonal edge and those having an elliptical shape. Any shape may be used as long as it can hold the lubricating oil in the recessed portion under the condition that a high surface pressure is generated on the contact surface. On the other hand, it does not include irregularities formed linearly when viewed from the solid surface. This is because the effect of retaining the lubricating oil in the recessed portion is low.

Further, it is desirable that the area ratio of the recess to the entire contact surface is 80% or more. This is because if the area ratio of the recessed portion is low, the oil-retaining property of the lubricating oil on the contact surface is not sufficient.

The micro dimples can be applied by various processing methods such as shot blasting, electric discharge machining, electron beam machining, and laser machining, and any processing means capable of imparting crater-shaped dents may be used.

In the present invention, the microdimples on the contact surface between the outer peripheral member of the tube expansion head and the cone are preferably formed by shot blasting (hereinafter, the surface by shot blasting is referred to as "shot blasting surface"). This is because shot blasting is a processing method for forming a large number of dents on the surface of the material to be processed by projecting minute particles, which is more economical than other means. Further, it is easy to adjust the depth and size of the dents of the micro dimples by changing the shape and size of the particles projected on the surface on which the micro dimples are formed.

Further, in the present invention, it is preferable that the arithmetic average roughness Ra on the contact surface between the tube expansion head outer peripheral member and the cone is 0.3 to 1 μm. This is because if the arithmetic average roughness Ra is less than 0.3 μm, the oil retention capacity of the contact surface is lowered and the seizure prevention effect is not sufficient. On the other hand, when the arithmetic average roughness Ra exceeds 1 μm, the convex portion of the micro dimples becomes large, and metal contact is likely to occur on the contact surface between the outer peripheral member of the tube expansion head and the cone, and seizure may not be prevented. In addition, contact with the micro-convex portion tends to increase wear, which causes a problem that the frequency of cone replacement due to wear increases. When expanding a high-strength steel pipe, the surface pressure on the contact surface between the cone and the outer peripheral member of the pipe expansion head increases. Therefore, in order to further improve the oil retention property of the lubricating oil on the contact surface, the arithmetic mean roughness Ra is set. , 0.7 to 1 μm is more desirable.

If micro dimples are formed on the contact surface between the outer peripheral member of the pipe expansion head and the cone, the effect of retaining the lubricating oil can be obtained. Therefore, it is sufficient that the micro dimples are formed on one of the contact surfaces between the outer peripheral member of the tube expansion head and the cone. That is, micro dimples may be formed on the surface of the tube expansion head outer peripheral member, or micro dimples may be formed on the surface of the cone. However, it is often easier to replace the outer peripheral member of the tube expansion head than to replace the cone. Therefore, it is desirable that micro dimples are formed on the surface of the tube expansion head outer peripheral member in consideration of reworking the surface.

FIG. 5 shows the results of comparing the sliding resistance coefficients of the pipe expander with respect to the ground surface which is the surface of the conventional pipe expansion head outer peripheral member and the shot blast surface which is the surface of the pipe expansion head outer peripheral member of the present invention. The sliding resistance coefficient μ is a numerical value obtained from the attractive force when the tube expander operates, and is defined by μ = F / N. Here, F is an attractive force during operation of the tube expander, and was measured using a load cell as an axial force applied to the draw bar 21. N is a force in the vertical direction and is a force in the outer diameter direction applied to the steel pipe 1.

From FIG. 5, the sliding resistance coefficient in the case of the surface (ground surface) of the conventional tube expansion head outer peripheral member was 0.13, whereas the surface (shot blast surface) of the tube expansion head outer peripheral member of the present invention was 0. It can be seen that it is .005. Such a difference in the sliding resistance coefficient is a result of forming an abundant lubricating oil film on the contact surface between the cone and the outer peripheral member of the expanding head on the surface (shot blast surface) of the outer peripheral member of the expanding head of the present invention. This is because micro metal contact on the contact surface is suppressed.

The steel pipe targeted by the pipe expander of the present invention is a welded pipe, and after welding the inner and outer surfaces of the pipe, the pipe is expanded in order to correct the deteriorated roundness and straightness. By expanding the pipe using the pipe expander of the present invention to manufacture the steel pipe, it is possible to suppress a decrease in yield due to equipment trouble and maintain a high roundness of the steel pipe for a long period of time. For example, in a normal UOE steel pipe, an end face is welded using a thick steel plate as a material, and then formed into a U shape or an O shape by a pressing device, and then a mating surface is temporarily attached to the inner and outer surfaces. Seam welded from the submerged arc welding method. After that, after finishing to a predetermined diameter with a tube expander, inspections such as appearance and dimensions are performed, and the product is shipped as a product. However, the embodiment of the present invention can be applied not only to the welding pipe by the UOE method but also to the manufacturing method of the welding pipe by the press bend method.

In the present invention, the target steel pipe has a wall thickness of 19 to 45 mm, an outer diameter of 450 to 1500 mm, and is preferably a high-strength steel pipe having an API standard of X65 or more.

Taking the case where the contact surface between the cone 17 and the jaw 19 (which is the outer peripheral member 18 of the pipe expansion head) in FIG. 2 is a microdimple as an example of the present invention, the welded pipe is expanded and the contact surface between the cone 17 and the jaw 19 is formed. , The presence or absence of seizure and the amount of wear were investigated.

Tool steel was used for the jaw 19. Further, a mineral oil having a kinematic viscosity at 40 ° C. of 20 mm / s was supplied as a lubricant to the contact surface between the cone 17 and the jaw 19. Further, as the cone 17, tool steel finished to an arithmetic average roughness Ra of 0.5 μm by grinding was used.

Regarding the presence or absence of seizure on the contact surface, the surfaces of the cone 17 and the jaw 19 were visually observed to determine the presence or absence of flaws due to seizure. On the other hand, regarding the presence or absence of wear, the thickness of the cone 17 was measured, and the amount of wear was determined from the difference from the initial thickness at the time of cone replacement. If the amount of wear is 1 mm or less, there is no practical problem.

The results are shown in Table 1.

From the results in Table 1, in all of the examples of the present invention in which microdimples were formed on the contact surface between the outer peripheral member of the tube expansion head and the cone, seizure did not occur and the amount of wear was small. On the other hand, in the case of the prior art, which is a comparative example, seizure occurred because microdimples were not formed on the contact surface between the outer peripheral member of the tube expansion head and the cone. In addition, the number of pipe expansions to the cone steel pipe was higher than that in the comparative example.

From the above, by forming micro dimples on the contact surface between the outer peripheral member of the tube expansion head and the cone, seizure is less likely to occur, the life of the cone is extended, and the cost of tube expansion can be suppressed. Therefore, the frequency of replacement of the cone and the outer peripheral member of the pipe expansion head can be reduced, and the steel pipe can be manufactured at low cost.

1 Steel pipe 11 Cylinder 12 Horn 13 Pipe expansion head 14 Pipe expansion machine body 15 Axial infeed 16 Cross feed 17 Cone 18 Pipe expansion head outer peripheral member 19 Joe 20 Die 21 Drawbar 22 Lubricating oil supply pipe 100 Pipe expansion machine

Claims (4)

A cone whose outer circumference gradually changes in the axial direction,
A pipe expander for expanding a steel pipe having a pipe expansion head outer peripheral member that contacts the outer circumference of the cone.
A pipe expander characterized in that micro dimples are formed on a contact surface between the outer peripheral member of the pipe expansion head and the cone. The tube expander according to claim 1, wherein the micro dimples are micro dimples produced by shot blasting. The tube expander according to claim 1 or 2, wherein the arithmetic average roughness Ra on the contact surface between the tube expanding head outer peripheral member and the cone is 0.3 to 1 μm. A method for manufacturing a steel pipe, which comprises expanding a steel pipe by using the pipe expander according to any one of claims 1 to 3.