JPS6082613A - Preparation of electric welded tube for upset tubing - Google Patents

Abstract

PURPOSE:To prepare the titled steel pipe satisfying requirements for formability, weldability and standard for strength by regulating cooling condition immediately after upsetting and heat treating condition after upsetting of electric welded tube of relatively low carbon and low alloy steel with a specified compsn. CONSTITUTION:A hot-rolled coil consisting by wt% of 0.13-0.20 C, <=0.25 Si, 1.0-1.5 Mn, <=0.03 P, <=0.01 S, 0.01-0.05 Nb, 0.005-0.06 Al, and residual Fe is formed to a pipe by slitting, forming, and electric welding. The steel pipe is upset by heating at 1,100-1,250 deg.C and cooled where the cooling is executed at 1.5-5 deg.C/sec cooling rate between 800 deg.C and 500 deg.C during the cooling stage, or under the cooling condition for normalizing after upsetting is 15-30 deg.C/sec from 800 deg.C to 500 deg.C, or cooling is executed at 30-60 deg.C/sec from 800 deg.C to 300 deg.C and then tempered at 550-650 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ERW steel pipe for upset tubing, and more specifically, it corresponds to the J-55 class for upset tubing defined in the API standard (having shallow-area characteristics, and The present invention relates to a method for manufacturing ERW steel pipes that can maintain formability and weldability with a low carbon and low alloy composition.

With the recent development of deep-N oil fields and offshore oil fields, high-strength materials are required for upset tubing materials for oil well drilling and oil extraction, and according to the API-J55 Tuwing standard, its mechanical properties are 38% yield strength. .7~56.2k
g/mm2, tensile strength of 52.7 kg/mm2 or more, and elongation of 24% or more.

Conventionally, in order to meet the strength standards for this grade of upset duping, a seamless tube with a high carbon and high alloy composition has been used as the raw tube and has been upset-processed under hot conditions. However, this steel pipe has the drawback of high cost.

From this point of view, it is possible to use ERW steel pipes as an alternative to seamless W4@, but J55 class chewing materials may be used without heat treatment after upsetting or may be normalized. It is difficult to manufacture both from materials with the same composition, and for this reason,
There is a complication in that two types of materials with different compositions are required.

In other words, if a steel pipe that is intended to be used without normalizing is heat treated, the yield strength will be low and it will not be able to meet the standard value of API-J55, and conversely, if the pipe is not normalized If a material that is intended to be processed is used without heat treatment, there is a risk that the yield strength will exceed the upper limit of the specification.

Furthermore, when heat treatment is performed after upsetting, the material composition becomes high carbon and high alloy, which has a major drawback in manufacturing ERW steel pipes, such as poor cold workability and poor weldability.

In order to improve these, the present inventor believes that it is important to maintain formability and weldability with a material composition that is relatively low carbon and low alloy, and that maintaining the strength of the steel pipe requires cooling strips 1 after upsetting. Regulates heat treatment after machining or abhit processing,
In other words, we conducted research focusing on regulating the conditions for normalizing or quenching and tempering, and found that if this manufacturing method were used, it would be possible to produce J55 class apples with only one type of composition, good manufacturability, and low cost. ...It was found that ERW steel pipes for tubing can be obtained.

The present invention is based on the results of the above and repeated experiments, and specifically, C: 0.13 to 0.20%, Si
S0.25%, Mn: 1.0-1.5%, P≦0.
03%, S≦0.01%, Nb: 0.01-0.0
A hot-rolled coil consisting of 5% Al20, 005~0.06%, the balance iron and impurities is slitted, formed, and ERW welded to form a pipe into a specified size, then upset processing is performed, and immediately thereafter We propose a method for manufacturing electric resistance welded steel pipes that meet the API-J55 dungeon standard by regulating the cooling conditions and the heat treatment conditions after upset processing.

The present invention will be explained in detail below.

First, the composition of the steel pipe material is relatively low carbon and low alloy to ensure formability and weldability, which are important factors in the manufacture of ERW steel pipes, as well as properties shown in the API-J55 standard.

Therefore, the composition of the steel pipe material will be explained as follows.

C: 0.13-0.20% and Mll: 1.0-1.
The lower limits of 5%C and Mn were set to 0.13% and 1, respectively.
．． The reason why it is set at 0% is because if it is less than this, the strength of the main tube in the as-molded state without heat treatment cannot satisfy the API standard. Additionally, the upper limits of C and un are set at 0.20% and 1.5%, respectively, because if added in excess of these limits, the main tube part will break down if quenched and tempered after upset processing. Strength is A P I M
This is because the upper limit of the standard value is exceeded, and furthermore, weldability deteriorates and the incidence of penetrator defects rapidly increases.

SiS2.25% Sl is an element that is inevitably contained in steel when making steel, and if it is added in excess of 0.25%, weldability will deteriorate.
The incidence of penetrator defects increases by 0.25%.
was set as the upper limit.

P≦0.03%, S≦0.0+% P and S are impurities and elements that inhibit weldability. May cause swelling.

Nl): 001~0.05% Nb is an element necessary to ensure the strength of the main pipe in the as-formed state without heat treatment, and must be 0.01% or more to meet the API strength standards. If it exceeds 0.05%, the yield strength may exceed the standard value, so this was set as the upper limit.

All: 0.005 to 0.06% Al is a necessary element for deoxidizing steel, and if the amount of oxygen in the steel is not reduced, penetrator defects will occur in the electric resistance welding part, so it should be contained at 0.005% or more. Moreover, if it exceeds 0.06%, coarse 1203-based inclusions will be formed, creating a risk of twisting in the vicinity of the electric resistance welding part.

Next, the steel pipe material having the above composition is hot-rolled according to a normal process, and then the hot-rolled coil is slit, formed, and electric resistance welded to produce a mother pipe for upset tuning.

Subsequently, both ends of the main tube of the mouth are heated to 1100 to 1250° C. for upset processing, and then heat treatment is performed under the following heat treatment conditions.

Upset processing usually cuts the pipe end to 1100~125mm.
Processing is performed after heating to 0°C, and at the end of the processing, the upset part temperature has been cooled to approximately i ooo°C, and this temperature is cooled by air cooling etc., and during cooling of the mouth, the temperature of the upset part is reduced to 800°C
Cooling is performed at a cooling rate of 1.5 to b/sec between 500°C and 500°C.

That is, if a steel pipe having the above composition is cooled in the atmosphere immediately after upsetting, the yield strength of the upsetting portion will be lower than the API standard.

In order to meet the standard value of yield strength, the temperature must be 800 to 500℃.
It is necessary to cool the temperature at a rate of 1.5°C/sec or more, in which case the yield strength will be 38.7klJ/m1 or more, and the cooling rate in the same temperature range must be 5°C/sec or more. The yield strength is 56,2 kg/mm if it is less than 2 seconds.
2 or less. In addition, copper in the above composition range is 800 to 50
Since the transformation to ferrite, barley 1 to bainite is completed by 500°C from 1.5 to 0'C, there is no need to particularly limit the cooling conditions below 500°C.

In addition, when performing normalizing treatment after upsetting, the cooling rate between 800 and 500°C should be set at 15 to 15°C.In other words, if the cooling rate is less than 15°C/sec, the yield strength will be below the lower limit of the standard value. Moreover, if the temperature exceeds 30° C./sec, the yield strength exceeds the upper limit of the standard value. In this case as well, since the bainite transformation is completed by 500°C, there is no need to particularly limit the cooling conditions below 500°C.

Further, when performing furnace heating and tempering treatment after upsetting, cooling is performed between 800 and 30°C at a rate of 30 to 60'C/sec, and then tempered at 550 to 650°C.

In other words, if the cooling rate between 800 and 300'C during quenching is less than 30°C/sec, the yield strength of the upset part after tempering will be below the standard value, and if it exceeds 60°C/sec, the yield strength after tempering will be lower than the standard value. This is because the yield strength of the main pipe exceeds the standard value.

If the tempering temperature is less than 550°C, the yield strength when the cooling rate during quenching is increased will exceed the standard value, while if it exceeds 650°C, the yield strength when the cooling rate during quenching is decreased will exceed the standard value. 550-650 as it goes below.
°C range.

Next, examples will be explained.

The steel pipe materials having the compositions of the present invention and the conventional examples shown in Table 1 are hot-rolled, slitted, formed, and electrically welded to obtain a main pipe with J strength shown in Table 2. Defects in the welded parts were detected by ultrasonic flaw detection and were as shown in Table 3.

As is clear from Table 1, Table 2, Table 3, Tables 2 and 3, the method of the present invention has good formability and weldability, and even when the pipe is made as is, it has an A.
Meets P I J 55 standards. On the other hand, conventional steel pipe E is constructed to be subjected to normalizing treatment, but due to its composition, welding defects are likely to occur, and the yield strength of the pipe as it is produced exceeds the standard value. ing. The steel pipe E according to the conventional example is subjected to normalizing treatment (
As shown in Table 4, the strength of steel pipes when they are held at 900°C for 5 minutes and then cooled in air is below the lower limit of yield strength for steel pipes that are intended to be used as they are.

Table 4 On the other hand, when steel pipes A, B, and C are processed into fixtures 1 by the method of the present invention and then subjected to respective heat treatments as shown in Table 5, the strengths shown in Table 5 are obtained.From these points, When manufactured by the method of the present invention, the electrical resistance welded tube satisfies the strength standards in all cases.

As explained in detail above, by manufacturing pipes from low-carbon, low-alloy materials using the method of the present invention and heat-treating them, it is possible to create ERW steel pipes with contradictory properties such as strength, formability, and weldability, which were previously considered difficult. It is possible to manufacture 1 to 7 dupings of J55 class Absela pipes.

1. Applicant: Kawasaki Steel Corporation Representative Patent Attorney Yoshikatsu Matsushita Lawyer Fumi Soejima

Claims (1)

[Claims] 1) C in weight%: 0.13 to 0.20%, S1≦0.
25%, Mn: 1.0-1.5%, P≦0.03%, S
≦0.01%, Nb + 0.01-0.05%, AI
l: 0.005 to 0.06%, the balance being iron and impurities, a hot rolled coil is slit, formed, and electrically welded to a specified size. One square meter, 1100 to 1250°C.
During the cooling process, the
1. A method for manufacturing an electric resistance welded steel pipe for abhit tubing, characterized by cooling the pipe at a rate of 1.5 to 5°C/second between 00°C and 500°C. 2) Weight fN%r, C: 0.1.3-0.20%, Si
S2.25%, Mn: 1.0-1.5%, P≦0.
03%, S≦0.01%, Nb: 0.01-0.05%
,Ajl! :0.005~0.06%, balance iron and impurities after forming a hot rolled coil into a specified size by slitting, forming and electric resistance welding.
Heat to 50°C and perform processing from Abcera 1 to C80 as cooling conditions during normalizing treatment after upset processing.
A method for manufacturing an ERW steel pipe for Abhira 1 tubing characterized by cooling between 0 and 500'0 at a rate of 15 to 30"C/sec. 3) C: 0.13 to 0.20% by weight, S1≦0.2
5%, Mll: 1.0-1.5%, P≦0.03%, S
≦0.01%, Nll: 0.01-0.05%, A
[:0.005~0゜06%, balance iron and impurities] A hot-rolled coil is slitted, formed, and electric resistance welded to form a pipe into a specified size, then heated to 1100~1250℃ and subjected to upset processing. Do it and add that upset
The cooling conditions during quenching of 1.1 are 800 to 300°C at 30 to 30°C, and then tempered at 550 to 650°C.
0. A method for manufacturing an ERW steel pipe for upset tubing, characterized by: