JPH08141691A - Method for upsetting pipe - Google Patents

Abstract

PURPOSE: To obtain the prescribed length of an increased thickness part without developing the defect such as buckling and flaw on the outer surface of a pipe. CONSTITUTION: In an upsetting method of the pipe by heating the pipe end part, holding the outer surface of the part to be heated of the pipe end with dies 1 and pushing a mandrel 2 into the inner surface to increase the thickness of the pipe end, at the time of working, after heating the die surface parts in the range contacting with the part to be worked of the pipe end just before working, the working is executed. By this method, the stable upsetting for increasing the thickness in the prescribed length can be executed without developing the defect such as the buckling and the flaw of the outer surface of the pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of upsetting a pipe.

[0002]

2. Description of the Related Art Usually, a plurality of pipes are connected by a joint and used in a long state, so that it is necessary to thread a pipe end. However, if the raw pipe is threaded as it is, the thread portion becomes brittle due to stress concentration. Therefore, in general, after heating the pipe end of the raw pipe to a uniform temperature of about 1200 ° C., as shown in FIG. The hot forging process (hereinafter referred to as upset process) for increasing the wall thickness of the pipe end as shown in (3) is performed to secure the strength of the threaded portion.

There are three methods for this upset processing shown in FIG. I / EUE (Internal &
In the case of the External Upset End) type, the outer diameter shape of the pipe is determined by the shape of the die 1 and the pushing amount of the mandrel 2 as shown in FIG.
In the case of the (Internal Upset End) type, the outer diameter shape of the pipe is determined by the shape of the die that restrains the outer diameter, but both processing methods are as shown in FIG. Since the inner surface tapered portion 3a of the pipe 3 is a free surface, the shape of the tool (the die 1 and the mandrel 2) and the pushing amount of the mandrel 2 cannot control the material flow of the pipe. The temperature conditions of are very important.

However, in the upset process, since a hollow product having a small heat capacity is processed, the inner and outer surfaces of the raw pipe are removed by contact with the tool during the process. In particular, in the conventional upset processing method, in order to prevent the die from being softened and deformed or worn by the heat received from the raw pipe, it becomes impossible to perform sufficient forming processing. Immediately after that, the cooling water is sprayed from multiple cooling nozzles to cool the die.Therefore, the heat removal due to the contact with the die on the outer surface of the blank pipe during upset processing is large, and the blank pipe is locally cooled. As a result of non-uniform deformation resistance, the length of the thickened portion that must be finished to a predetermined length for thread cutting is insufficient, and also defects such as buckling and flaws on the outer surface of the pipe Will occur.

The EUE (External Upset) shown in FIG.
In the case of the (End) type, there is no change in the inner diameter and the outer diameter is restricted by the die, so there is no variation in the length of the thickened part, but heat removal due to contact between the inner and outer surfaces of the blank pipe and the tool during processing As a result of the element tube being locally cooled and the deformation resistance being nonuniform, buckling and flaws occur at the outer taper portion.

[0006] As described above, the conventional method of heating only the end portion of the raw pipe and cooling the die by spraying the cooling water from the plurality of cooling nozzles immediately after each upset process is completed. Then, there were many problems during upset processing.

On the other hand, for example, Japanese Patent Laid-Open No. 61-2767
Japanese Patent Laid-Open No. 32-32 proposes a method in which the heating temperature distribution in the middle portion of the pipe end is gradually reduced from the thick side of the pipe end toward the steady part of the pipe to perform upset processing. Even if the slope and length of the taper part can be controlled, it is possible to eliminate the defects such as insufficient length of the thickened part due to nonuniform deformation resistance due to tool contact, buckling, and defects on the outer surface of the pipe. Has not arrived.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of upsetting a pipe capable of obtaining a predetermined length of the thickened portion without causing defects such as buckling or flaws on the outer surface of the pipe. It is in.

[0009]

In order to solve the above problems, the present inventor immediately sprays cooling water from a plurality of cooling nozzles to cool a die every time one upset process is completed, The following findings were obtained as a result of detailed investigation by analysis and experiment on the tool contact situation during the thickness increase deformation by the conventional method in which the tool is not heated and the upset processing is performed even after the end is uniformly heated.

In the I & EUE type upset process, as shown in FIGS. 2 (a) to 2 (f), the raw tube 3 first starts contact with the die taper portion 1a of the die 1. That is, the raw material pipe 3 first comes into contact with the die 1 at the portion that forms the outer surface tapered portion of the pipe, and then the raw material pipe 3 bulges outwardly so as to come into contact with the die parallel portion 1b as well, and further comes into full contact with the die 1. After this, the thickness of the raw pipe 3 should be gradually increased from the pipe end, and should be in contact with the mandrel 2 one after another.

In the IUE type upset process, since the raw pipe 3 and the die 1 are in contact with each other over the entire surface from the initial stage of the process, there is no intermediate step described above, and the raw pipe 3 is thickened in order from the pipe end immediately after the start of the process. Make contact with mandrel 2.

Even in the EUE type upset process, the material swells to the die side at the initial stage of deformation and there is almost no contact with the mandrel. Therefore, this can be regarded as one of the I & EUE type upset processes.

From the above, in any of the upset processing methods, the shell 3 is first cooled from the outer surface thereof, and buckling or buckling may occur in the deformation resistance of the outer surface during the cooling process. This may result in defects on the outer surface of the pipe and insufficient length of the thickened part.

In order to finish the thickened portion to a desired length, not only the pipe ends but also the entire parallel portion to the tapered portion must be deformed uniformly. Considering that occurs at the end of processing, it is important to suppress cooling of the raw pipe 3 due to contact with the die 1.

The gist of the present invention based on the above findings is the following method of upsetting a pipe.

A method of upsetting a pipe in which the pipe end portion is heated, the outer surface of the heated portion of the pipe end is held by a die, and the mandrel is pushed into the inner surface to increase the wall thickness of the pipe end. A method for upsetting a pipe, characterized in that a die surface portion in a range in contact with an end processed portion is heated immediately before processing and then processed.

[0017]

The present invention will be described below together with its function and effect.

Also in the upset processing method of the present invention, the entire length of the material pipe end processed portion before processing is heated so as to have a uniform temperature, and cooling water is immediately discharged from a plurality of cooling nozzles every time one upset processing is completed. Although the method of spraying and cooling the die is the same as in the conventional method, before performing the upset processing, the surface of the die surface in the range in contact with the raw pipe during the processing is heated, and then the upset processing is performed immediately. That is, at the same time when the heating of the surface portion of the die is completed, the raw tube whose tube end portion has been heated is inserted into the upset processing apparatus, and immediately upset processing is performed. By doing this, the cooling of the outer surface of the blank pipe during processing is suppressed and the material flow is improved, so the length of the thickened part is improved, and in addition, there is buckling and defects such as those that have been conventionally seen on the outer surface. Upset processing can be performed without causing defects.

By the way, in the method of the present invention, as in the conventional method, the cooling water is sprayed from a plurality of cooling nozzles immediately after each upset process is finished to cool the die. In addition to the general purpose of blowing away it when it adheres to the die and cleaning the surface, when heating the die surface immediately before upset processing,
This is because the temperature is always controlled to an appropriate temperature described later, and defects such as insufficient length of the thickened portion, buckling, and flaws on the outer surface of the pipe due to uneven deformation resistance are eliminated.

The method of the present invention has been described above, but the following is a more detailed example of the method.

First, the entire length of the pipe end to-be-processed portion is heated to a uniform temperature (for example, 1200 ° C.).

In parallel with the heating of the raw pipe, the surface of the die which is considered to come into contact with the raw pipe during processing is
For example, by heating means such as a gas burner,
Heat to 00 ° C.

Simultaneously with the completion of the heating of the die surface to a desired temperature, the blank tube from which the scale generated by the heating has been removed is inserted into the upset processing apparatus and immediately upset processing is performed.

According to this method, when the raw pipe swells outward and comes into contact with the die, the cooling from the surface layer of the raw pipe is suppressed and the material flow is improved, so that defects such as flaws and buckling can be prevented. A desired thickness increase portion length can be obtained without causing defects.

Regarding the heating of the surface of the die, it is sufficient to heat the area in contact with the portion to be processed at the pipe end during processing, but the entire inner surface of the die may be heated. In addition, this heating temperature suppresses cooling due to contact with the die on the outer surface of the raw tube, and on the other hand, to prevent the die from being softened and deformed or worn due to heating, which makes it impossible to perform sufficient molding. The temperature may be 500 ° C. Note that 300 to 400 ° C. is a particularly preferable temperature range.

[0026]

【Example】

[I & EUE type upset processing] Outer diameter φ73m
m, wall thickness 5.51 mm, using a medium carbon steel pipe, thickness increase ratio 1.5, thickness increase ratio (upset amount / outer pipe outer diameter)
2.0 I & EUE type upset processing (Fig. 3
(See (a)).

That is, (a) while uniformly heating the portion of the pipe end of 500 mm at 1200 ° C., the surface portion of the die from the pipe end side to the taper portion is heated to 400 ° C. by using a gas burner. Then, at the same time when the heating of the die surface portion is completed, the raw pipe from which the heating scale has been removed is inserted into an upset processing device, and immediately upset processing is performed.

(B) 120 mm portion of the tube end 500 mm
A method according to the conventional method in which after uniformly heating to 0 ° C., upset processing is performed immediately without heating the die.

The thickness increase portion length 28 set by the above two methods
Upset processing of 0 mm was performed.

The number of pieces processed by the methods (a) and (b) is 50 each.

As a result of the upset processing, when processed by the conventional method, the variation in the length of the thickened portion was 40%, and defects such as buckling and flaws on the outer surface of the pipe were observed. However, when processed by the method of the present invention, defects such as buckling and flaws on the outer surface of the pipe do not occur at all, and the length of the thickened portion is 1 on average as compared with the conventional method.
It could be improved by 8%, and the variation in the length of the thickened portion was within 30%, which was in a very good state.

[IUE type upset processing] Outer diameter φ
73mm, thickness 5.51mm medium carbon steel tube, thickness increase ratio 1.5, thickness increase ratio (upset amount / outer tube outer diameter) 2.0 outside diameter constant IUE type upset processing (see FIG. 3B) was performed.

That is, as in the case of the above I & EUE type upset processing, (a) the raw pipe end 500 mm
At the same time as heating the part to 1200 ° C., the surface of the die from the pipe end side to the taper part is heated to 400 ° C. by using a gas burner, and at the same time the heating of the die surface is completed. The method according to the present invention, in which the blank tube from which the heating scale has been removed is inserted into an upset processing device and immediately upset processing is performed.

(B) 120 mm portion of the tube end 500 mm
A method according to the conventional method in which after uniformly heating to 0 ° C., upset processing is performed immediately without heating the die.

The thickness increase portion length set by the above two methods is 28
Upset processing of 0 mm was performed.

The number of pieces processed by the methods (a) and (b) is 50 each.

As with the case of [I & EUE type upset processing], the result of upset processing is that the variation in the length of the thickened portion is 40% when processed by the conventional method, and there is buckling or a flaw on the outer surface of the pipe. Such defects were seen. However, when processed by the method of the present invention, defects such as buckling and flaws on the outer surface of the pipe do not occur at all, and the length of the thickened portion can be improved by an average of 18% as compared with the conventional method. The variation in part length was within 30% and was in a very good state.

[EUE type upset processing] Outer diameter φ
EUE with a constant inner diameter of 73 mm, 5.51 mm thick medium carbon steel tube, with a wall thickness increase ratio of 1.5 and a wall thickness increase ratio (upset amount / outer tube outer diameter) of 2.0 Type upset processing (see FIG. 3C) was performed.

That is, the above I & EUE type and IU
As in the case of E type upset processing, (a) the 500 mm portion of the raw pipe end is uniformly heated to 1200 ° C, and the surface of the die is tapered with a gas burner from the pipe end side to the taper part. A method according to the present invention, in which the raw pipe from which the heating scale has been removed is inserted into an upset processing device and immediately heated up to 300 ° C. to complete the heating of the die surface portion, and immediately upset processing is performed.

(B) 120 mm portion of the tube end 500 mm
A method according to the conventional method in which after uniformly heating to 0 ° C., upset processing is performed immediately without heating the die.

The thickness increase portion length set by the above two methods is 28
Upset processing of 0 mm was performed.

The number of pieces processed by the methods (a) and (b) is 50 each.

As a result of the upset processing, when processed by the conventional method, defects such as buckling and flaws in the outer taper portion were observed. However, when processed by the method of the present invention, defects such as buckling and flaws on the outer surface of the tube did not occur at all and were in a very good condition.

[0044]

As described above, according to the method of the present invention, it is possible to perform a stable upset process for increasing the thickness of a predetermined length without causing defects such as buckling and flaws on the outer surface of the pipe. Therefore, the industrial effect is extremely large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of I & EUE type upset processing. (A) shows a state immediately before processing, and (b) shows a state immediately after processing.

FIG. 2 is a cross-sectional view schematically showing a thickness increasing process in a conventional method of I & EUE type upsetting. (A) ~
Processing proceeds in the order of (f).

FIG. 3 is a cross-sectional view showing various upset processing types. (A) is an I & EUE type, (b) is an IUE type, and (c) is an EUE type.

[Explanation of symbols]

1: Die, 1a: Die taper part, 1b: Die parallel part, 2: Mandrel, 3: Element pipe, 3a: Element pipe inner surface taper part

Claims (1)

[Claims] 1. A method of upsetting a pipe, comprising heating a pipe end portion, sandwiching an outer surface of a heated portion of the pipe end with a die, and pushing a mandrel into the inner surface to increase the wall thickness of the pipe end. An upset processing method for a pipe, characterized in that the surface of the die, which is in contact with the processed portion at the end of the pipe, is heated immediately before the processing and then processed.