JPH0713259B2 - High-strength ERW pipe manufacturing method - Google Patents

Description

The present invention relates to a method for producing a high-strength electric resistance welded steel pipe.

[Conventional technology]

In order to improve fuel efficiency, steel pipes for machine structures used as structural members and drive transmission members of automobiles, etc. are being considered for weight reduction, and one of the measures is to increase the tension.

There are conventionally two types of manufacturing methods for high-strength electric resistance welded steel pipes, one of which is to increase the tensile strength of the steel plate itself by the method described in Japanese Patent Laid-Open No. 52-114519, and then to perform electric resistance welded pipes. The second is the method of manufacturing, and the second is after the electric sewing pipe, the tempering,
That is, it is a method of manufacturing by quenching or quenching and tempering.

[Problems to be Solved by the Invention]

As described above, there are two types of methods described in the section of the related art. FIG. 3 shows a manufacturing process of a general electric resistance welded steel pipe.
Generally, it is formed, welded, and left as it is, or heat-treated after that. The purpose of this heat treatment is to homogenize or secure ductility of the electric resistance welded portion. However, if a high-strength steel pipe is to be manufactured in the above process, the steel plate itself will be made to have a higher tensile strength, and then it will be manufactured by electric-welding pipes. Roll forming is difficult, and therefore the shape at the time of electric resistance welding becomes poor, resulting in poor electric resistance welding. After the second ERW pipe, tempering,
That is, the method of manufacturing by quenching or quenching and tempering is very high in tempering cost, and is not general except when it is unavoidable that the former method cannot be adopted.

An object of the present invention is to solve the problems in the method for manufacturing such a high tensile electric resistance welded steel pipe.

[Means for Solving the Problems]

 The gist of the present invention is as follows.

(1) Component composition is C: 0.10 ~ 0.65% by weight, Si: 0.05 ~ 0.6
0%, Mn: 0.25 to 2.0%, Ti: 0.020 to 0.150%, Cr: 0.1 to 1.
In the production of electric resistance welded steel pipe consisting of 0% as a basic component and the balance Fe and unavoidable elements, 40% during hot plate rolling of steel for pipes
Wind up at 0-600 ℃ or 700-750 ℃, 600-700 ℃ after pipe making
A method for producing a high-strength electric resistance welded steel pipe, which is characterized by performing heat treatment at.

(2) In the method for producing an electric resistance welded steel pipe according to the above 1, the production of a high-strength electric resistance welded steel pipe characterized by adding cold plate thickness rolling or pipe making online cold tube plate thickness rolling after hot plate thickness rolling. Method.

The present invention will be described in detail below. FIG. 1 shows a manufacturing process according to the invention of claim 1.

In the conventional process, if it is attempted to manufacture a high-strength steel pipe as described above, the steel plate itself is made to have a high tension, and then electric resistance welding is performed. It is difficult, and therefore the shape at the time of electric resistance welding becomes poor, resulting in poor electric resistance welding. Therefore, in the present invention, the steel plate itself is made of a soft material that can be formed, and the high temperature steel pipe is manufactured by controlling the heat treatment temperature after the pipe making.

First, the reasons for limiting the components of the steel sheet used in the present invention will be described.

If the C content is small, the ductility is good and the workability is excellent, but the required strength cannot be obtained, so the lower limit was made 0.10%. Further, if it exceeds 0.65%, the cold workability such as formability at the time of pipe making and the toughness tend to be deteriorated, and the heat-affected zone is hardened during the pipe making welding of the electric resistance welded steel pipe, and the workability is lowered. Therefore, the upper limit was set to 0.65%.

In the case of killed steel, it is difficult to control Si to less than 0.05% in terms of steelmaking technology, and if it exceeds 0.60%, the ductility and toughness will be adversely affected. did.

Regarding Mn, if it is less than 0.25% from the viewpoint of strength, the strength will be insufficient, and if it exceeds 2.0%, cracks may occur due to insufficient ductility during processing such as molding during pipe making,
The lower limit was 0.25% and the upper limit was 2.0%.

Ti is an important element for strengthening, but if it is less than 0.020%, the strength is insufficient, and if it is added over 0.150%, the effect is not improved, so the lower limit is 0.020% and the upper limit is 0.150.
%.

Cr is an important element for preventing softening during joint welding of pipes, but if it is less than 0.1%, it has no effect on the softening resistance and it is not necessary to add it in excess of 1.0%, so the lower limit is 0.1%, The upper limit was 1.0%.

Next, the manufacturing process will be described.

In accordance with the present invention, the steel of the above components 400 ~ 6 during hot strip rolling
Wind at 00 ℃ or 700-750 ℃. This is to prevent the precipitation effect of Ti and make it as soft as possible.
If the temperature is lower than 0 ° C, the precipitation effect of Ti is small, but on the contrary, the cooling rate is fast and the strength increases, and the toughness also decreases. The precipitation effect of Ti is most present above 600 ° C and below 700 ° C. 750 ° C
The super is impossible to manufacture. Therefore, by rolling the steel having the above components at 400 to 600 ° C. or 700 to 750 ° C. during hot plate thickness rolling, a relatively soft material with little Ti precipitation effect can be obtained.

Although the pipe is made after this winding step, since it is made of a relatively soft material, there is no problem in forming and welding which has been a problem in the past, and a high quality electric resistance welded steel pipe can be made.

Next, it is a heat treatment after pipe forming, and this heat treatment produces a Ti precipitation effect. That is, heat treatment is performed at 600 to 700 ° C. If it is less than 600 ° C, the precipitation effect of Ti is small, and even if it exceeds 700 ° C, Ti is not sufficiently precipitated, and in either case, a sufficient precipitation effect cannot be obtained.

Although the present invention has been described above, the method according to claim 2 may be used. FIG. 2 shows the steps according to the method of claim 2. By adding the pipe forming online cold plate thickness rolling in this manner, a steel pipe having a higher tensile strength can be manufactured. .

〔Example〕

Table 1 shows the results of pipe making of ERW steel pipe of size φ101.6 × t4.4 by the method of the present invention and the conventional method.

As shown in Table 1, according to the present invention, it is possible to obtain a high strength electric resistance welded steel pipe by adjusting the coiling temperature so that the steel plate has a strength capable of forming a pipe and further heat-treating after the pipe is formed.

〔The invention's effect〕

If a high-strength steel pipe is to be manufactured in the conventional process, the steel plate itself is made to have a high tension, and then it is manufactured by electric-welding pipes. Although it was difficult to form, the shape at the time of electric resistance welding became defective, resulting in poor electric resistance welding. However, according to the present invention, a high-strength electric resistance welded steel pipe can be economically formed without problems in forming and welding. Since it is possible to manufacture the product, it greatly contributes to the industry.

[Brief description of drawings]

FIG. 1 is a manufacturing process of the method according to claim 1, FIG. 2 is a manufacturing process of the method according to claim 2, and FIG. 3 is a conventional manufacturing process.

Claims (2)

[Claims] 1. The composition of ingredients is C: 0.10 to 0.65% by weight, Si: 0.0
5 to 0.60%, Mn: 0.25 to 2.0%, Ti: 0.020 to 0.150%, Cr:
When manufacturing electric resistance welded steel pipe consisting of 0.1 to 1.0% as a basic component and the balance Fe and unavoidable elements, at the time of hot plate thickness rolling of steel for pipes, winding at 400 to 600 ℃ or 700 to 750 ℃, pipe forming After 600
A method for producing a high-strength electric resistance welded steel pipe, characterized by performing heat treatment at a temperature of up to 700 ° C. 2. The method for manufacturing an electric resistance welded steel pipe according to claim 1, wherein cold plate thickness rolling or pipe making online cold plate thickness rolling is added after hot plate thickness rolling. Steel pipe manufacturing method.