JP2003311321A - Method for manufacturing high-strength uoe steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing transverse cracks caused in the weld metal of a seam-welded part when manufacturing a UOE steel tube of high strength of ≥800 N/mm<SP>2</SP>. <P>SOLUTION: In a method for manufacturing the high-strength UOE steel tube having a tensile strength of a base material of ≥800 MPa, an outer diameter of ≥406 mm, and a thickness of ≥10 mm, a steel plate is formed into a tube, and butt parts of the tubes are temporarily welded. A seam welding by a submerged arc welding is performed on an inner surface and an outer surface of the steel tube by using a welding flux of diffusible hydrogen of ≤20 ml/100 g under a condition that the tensile strength of a seam weld metal is ≤1,400 MPa, and 0.8 to 1.4 times the tensile strength of the base metal. After the lapse of 30 minutes from the completion of the welding, the steel tube is expanded under a condition that the expansion ratio is ≤5%. <P>COPYRIGHT: (C)2004,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steel pipe.
Specifically, long-distance transportation of natural gas, crude oil, etc.
The tensile strength used for line pipe etc. is 80
Regarding the manufacturing method of high-strength UOE steel pipes of 0MPa or more and large diameter
To do. [0002] For transporting natural gas, crude oil, etc. over long distances
UOE or UO steel pipe that is often used for line pipes
A large-diameter seam welded steel pipe, generally referred to as FIG.
As shown in (a) to (i), (a) a flat steel plate of a predetermined size
1 (b) adjusting the plate width, groove processing of both width end portions
2) (c) Bending process 3 at both width ends,
(D) U-shaped molding 4 and (e) O-shaped molding 5
(F) Gas seal the butt part
Tack welding 6 by de-arc welding, laser welding, etc.
(G) Internal seam welding by submerged arc welding
7 and (h) external seam welding 8 is performed, and then
(I) Expanders to increase the roundness of steel pipes
Is manufactured in the process of performing the tube expansion molding 9. Recent UO
In order to ensure high productivity, E steel pipe manufacturing plant
Each process is arranged on one line and can be processed continuously
It has been devised. In recent years, the use of gas and oil has increased, transportation costs have increased.
High-pressure transportation due to reduction of strikes and expansion of transportation efficiency
For this reason, line pipes are becoming larger, thinner and stronger.
It is out. With this background, we are currently using line pipe materials.
A prototype of high strength UOE steel pipe with a tensile strength of 700 MPa
Started, 800MPa or 1000MPa class high strength
Development of UOE steel pipe is also underway. In general, in a seam welded steel pipe, a welded HAZ is used.
And the tensile strength of the weld metal
When the tensile test of seam welded steel pipe
It is required to break in minutes. However, tensile strength
For high-strength UOE steel pipes with a degree of 700 MPa or higher,
Tensile test with strain concentrated on welded HAZ due to higher strength of genus
In this case, there is an increased risk of fracture at the position of the weld HAZ. Furthermore, high strength with a tensile strength of 800 MPa or more
In UOE steel pipe, transverse cracks occur in the seam weld during the manufacturing process.
A new problem has arisen. This transverse crack has been caused by the diffusion of weld metal.
Hydrogen embrittlement due to hydrogen, increased cracking susceptibility, tensile stress
It is said that this is a hydrogen crack caused by three additional factors.
(For example, welding joint handbook: Maruzen Co., Ltd. September, 1990)
Moon, P885). HT80 (tensile strength of 780 MPa or less
The above) occurs in weld metal with respect to cold cracking of high strength steel
It has been reported that prevention of lateral cracking is the most difficult
(Journal of the Japan Welding Society, Vol. 46 (1977) No. 12, 87
5 to 880), from the amount of diffusible hydrogen and the composition of the welding wire
Attempts have been made to predict the lateral cracking limit (“welding
Academic Journal, Vol. 46 (1977), No. 8, 561-566
page). However, in these reports, specific hydrogen content
If cracks occur in large quantities, preheating temperature during seam welding
Or cracking can be prevented by raising the interlayer temperature.
He only expressed his view that he can. As a countermeasure against transverse cracks in weld metal,
Pre-heat treatment or post-heat treatment during seam welding and welding materials
Reduction of the amount of diffusible hydrogen in the material. However, pre-heat treatment or post-heat treatment during welding
Has complicated the manufacturing process of UOE steel pipes,
This increases the manufacturing cost and is not preferable. Also, a high strength steel pipe of 800 MPa or more
Is a weld metal that can break the base metal during a steel pipe tensile test.
In order to ensure toughness, high basicity is required for submerged welding.
Need to reduce the amount of oxygen in the weld metal using flux
Generally, high basicity flux has a high amount of diffusible hydrogen.
Therefore, reducing the amount of diffusible hydrogen in the welding material
There is a limit in terms of securing toughness. Further, in Japanese Patent Laid-Open No. 2001-71176
Provides post-weld cooling by prescribing the chemical composition of the weld metal.
The welding residual stress by adjusting the martensitic transformation temperature during
Proposed method to prevent transverse cracking of weld metal by mitigating
Has been. However, the martensitic transformation point of the weld metal
Increase in alloying elements due to decrease in toughness reduces toughness and welding temperature
In order to promote cracking and realize base metal fracture during steel pipe tensile test
Balance of strength and toughness of weld metal for welding and ensuring weldability
From the standpoint of maintenance, control the component design of steel pipe base metal and weld metal.
About large is not preferable. Accordingly, a high strength with a tensile strength of 800 MPa or more.
Transverse cracking of weld metal that occurs when manufacturing UOE steel pipes
Reduced productivity, increased manufacturing costs, and
And there are few restrictions on the component design of weld metal, and seams
A method that can maintain the mechanical properties of steel pipes, such as the toughness of welds.
It is desired. [0015] The problems of the prior art described above
In view of the above, the present invention provides a high strength UOE of 800 MPa or more.
When manufacturing steel pipes, productivity decreases and manufacturing costs increase.
In addition, there are few restrictions on the component design of the base metal and weld metal.
And mechanical properties of steel pipe such as seam weld toughness
While maintaining the strength of the weld metal during the manufacture of high-strength UOE steel pipes
Prevents horizontal cracking, and also prevents cracking during pipe expansion molding
Aiming to provide a method for manufacturing high strength UOE steel pipe
Target. [0016] The present invention provides a method for producing a weld metal laterally.
From the analysis results of crack behavior, the occurrence of transverse cracks
Time from completion of welding to the start of tube expansion molding, diffusible hydrogen content,
Organize according to the expansion ratio during pipe forming and the strength of the weld metal.
Can be suppressed by prescribing these relationships
It was made based on the knowledge that it can. That is, the gist of the present invention is that the mother
The tensile strength of the material is 800 MPa or more and the outer diameter is 406 mm or more.
Manufacturing of high-strength UOE steel pipe with a wall thickness of 10mm or more
In the method, after the steel plate is formed into a tubular shape, the butt portion is temporarily attached.
After melt welding, the amount of diffusible hydrogen is 20 ml / 100 g or less.
Using welded flux, the seam weld metal has a tensile strength of 14
00 MPa or less and 0.8 times the tensile strength of the base material to 1.
Submerged arc on inner and outer surface of steel pipe under 4 times condition
Seam welding is performed by welding, and 30 minutes from the end of this welding.
After more than a minute has passed, the tube expansion rate is 5% or less.
A method of manufacturing a high-strength UOE steel pipe characterized in that it is shaped;
It is. DETAILED DESCRIPTION OF THE INVENTION The present inventors first made 800 MP.
When manufacturing high-strength UOE steel pipes of a or higher,
Investigate the size and strength of UOE steel pipes where transverse cracks occur
As a result, the following was found. (1) About the size of high-strength UOE steel pipe
If the wall thickness is 10 mm or more,
This happens a lot. Moreover, the outer diameter is 406 mm or more
In some cases, the weld thickness is usually 10 mm or more.
Many transverse cracks of the genus occur. [0020] High strength UOE steel of 800 MPa or more
For pipes, U-shaped and O-shaped press molding is possible depending on the equipment capacity.
The thickness of steel pipes that can be expanded or expanded is regulated and is currently
In terms of capacity, the upper limit of the thickness of steel pipe that can be manufactured is about 40 mm.
is there. (2) Regarding the strength of UOE steel pipe,
The transverse strength of the weld metal when the tensile strength of the pipe base material is 800 MPa or more
This happens a lot. The tensile strength of the steel pipe base material is 1200MP.
Ultra-high-strength steel pipes exceeding a are manufactured in the current manufacturing process.
When making, degradation of formability, welding HA of seam welds
Z and weld metal toughness reduction and pipe cracking
Of the tensile strength of steel pipes that can be manufactured at present.
The upper limit is about 1200 MPa. Based on the above, in the present invention, the weld metal
The tensile strength of the base metal of the weld metal that generates a lot of transverse cracks is 80
0 MPa or more, outer diameter 406 mm or more, and wall thickness 10
A method for manufacturing a high-strength UOE steel pipe of mm or more was used. The following is a method for manufacturing the high strength UOE steel pipe of the present invention.
The reason for limiting the manufacturing conditions in the law will be described. The inventors have a tensile strength of 950 MP.
After the steel sheet a is pressed into a tubular shape, the butt portion is pulled strong
Various fluxes and wires with different degrees of diffusive hydrogen content
Perform seam welding by submerged arc welding using
After that, the time from seam welding to the start of tube expansion
10m in length by changing the tube expansion rate and performing tube expansion molding
Manufactured UOE steel pipe and adjusted the occurrence of transverse cracks in weld metal
I investigated. The amount of diffusible hydrogen in the flux is JIS Z3
In accordance with the method for measuring the amount of hydrogen in 118 steel welds, No. 2 test piece
Submerged arc welding using the flux
Measures the amount of diffusible hydrogen in the weld metal immediately after contact.
Yes, the amount of diffusible hydrogen in 100 g of the weld metal
The same shall apply below). In addition, the presence or absence of transverse cracks in the weld metal,
Ultrasound weld bead surface 72 hours after seam welding
Inspected over the entire length by flaw detection test
If it occurred, it was judged that there was a lateral crack (hereinafter the same
) Based on experiments by the inventors, the present invention
The manufacturing conditions for UOE steel pipes with a wall thickness of about 40 mm or less
Is about 20 minutes after seam welding.
It is confirmed that it is cooled from 0 ° C to around 100 ° C.
It was. Also, diffusible hydrogen in the weld metal exceeds 100 ° C.
Diffuses and is released outside the base material or tube
However, the diffusion rate of diffusible hydrogen rapidly increases around 100 ° C.
Therefore, at temperatures below 100 ° C, the expansion in the weld metal
It was found that the diffuse hydrogen becomes difficult to move. On the other hand, in the steel pipe expansion forming process, the inside of the steel pipe
The base metal and seam weld are to be spread out from
Stretched in the circumferential direction of the pipe and conversely tries to shrink in the weld line direction
The At this time, the deformability of the weld metal in the seam welded part is the base material.
Compared to the large deformability, the weld metal has excessive plastic deformation.
As a result of being restrained by the base metal when shrinking due to
It has been confirmed that tensile stress occurs in the weld line direction. When the tensile strength of the weld metal is high,
The weld metal is more susceptible to cracking and is
It was also confirmed that many cracks tend to occur. From these findings, the present inventors have found that
After pipe forming, across the seam weld line in the circumferential direction of the steel pipe
In particular, the occurrence of horizontal splitting of the weld metal
The amount of diffusible hydrogen in the weld metal after the pipe expansion after seam welding
The diffusion rate of diffusible hydrogen depending on the time to start molding,
Tube expansion ratio during tube expansion forming, and tensile strength of weld metal
It depends on the conditions of the
A detailed study was conducted. (Amount of diffusible hydrogen in the flux)
Time from seam welding to the start of pipe expansion and seam welding
Of diffusible hydrogen in diffusible hydrogen in flux
And the relationship with the occurrence of transverse cracks in the weld metal. Na
The tensile strength of the weld metal obtained by seam welding is 10
The expansion rate at the time of 00 MPa and expansion was 3%. From FIG. 2, tube expansion molding starts after seam welding.
It takes 30 minutes or more to be used for seam welding.
The amount of diffusible hydrogen in the amount of diffusible hydrogen in the flux is 20 m.
Under the condition of 1 / 100g or less, transverse cracking of the weld metal occurs.
Absent. Diffusion in the flux used during seam welding
The amount of diffusible hydrogen in the amount of volatile hydrogen is 20 ml / 100 g or less
In some cases, the time from seam welding to the start of tube expansion forming
In 30 minutes, diffusible hydrogen in the weld metal is sufficiently diffused and
Because it is released to the outside of the material or pipe, the time is 30 minutes or less.
Amount of diffusible hydrogen remaining in weld metal during tube expansion
There is little, and it is tensioned in the welding direction of the weld metal by pipe expansion forming.
Even when force is applied, transverse cracking due to hydrogen embrittlement hardly occurs
Become. On the other hand, in the flux used during seam welding
The amount of diffusible hydrogen in the amount of diffusible hydrogen is 20 ml / 100 g
If exceeding, from seam welding to pipe expansion start
If the time is 30 minutes, the diffusible hydrogen in the weld metal is still sufficient.
If it is not diffused and remains for 30 minutes or longer
The diffusion rate of diffusible hydrogen in the weld metal becomes extremely slow and widens.
Weld metal welded by pipe expansion molding because it is difficult to be scattered
Transversely due to hydrogen embrittlement when tensile stress is applied in the direction
This is likely to occur. For this reason, expansion after seam welding is performed.
Even if the time to start tube forming is 120 minutes, tube expansion forming
Later, a lateral crack occurred. Therefore, in the present invention, the submerged arc solution is used.
Diffusible water in fluxes used during seam welding by welding
The elementary amount is defined as 20 ml / 100 g or less. Hula
The amount of diffusible hydrogen in the box is JIS Z3118 steel welded
In accordance with the method for measuring the amount of hydrogen in the
Welding immediately after submerged arc welding using the flux
Measures the amount of diffusible hydrogen in a metal and welds gold
It is the amount of diffusible hydrogen in 100 g of the genus. (Tube expansion ratio during pipe expansion molding) FIG. 3 shows seam welding.
The time until the start of tube expansion and the tube expansion rate during tube expansion
And the relationship with the occurrence of transverse cracks in the weld metal. In addition,
The tensile strength of weld metal obtained by seam welding is 100
0 MPa, diffusible water in flux used for seam welding
The elementary amount was 10 ml / 100 g. From FIG. 2, pipe expansion molding starts after seam welding.
The tube expansion rate is 30 minutes or more and the tube expansion rate during tube expansion molding
Under the condition of 5% or less, transverse cracking of the weld metal does not occur. one
On the other hand, if the tube expansion rate during tube expansion exceeds 5%,
Excessive regardless of the time from pipe welding to the start of pipe expansion forming
Transverse cracks due to excessive stress concentration, and seam welds
Depending on the bead shape, welding HAZ (melt
Breakage (expansion cracking) occurs at the contact end) position. When the tube expansion rate during tube expansion is 5% or less
Is a pipe that is loaded in the welding direction of the weld metal by tube forming.
Since the tensile stress is small, lateral cracking due to hydrogen embrittlement occurs.
The time from seam welding to the start of tube expansion forming
Sufficient diffusion of diffusible hydrogen in weld metal over 30 minutes
If the amount of remaining diffusible hydrogen is small, hydrogen embrittlement
Due to the synergistic effect with the suppression of cracks, transverse cracks do not occur. On the other hand, the tube expansion rate during tube expansion molding exceeds 5%.
In some cases, the weld metal is loaded in the welding direction by tube expansion.
Lateral cracking due to hydrogen embrittlement occurs due to large tensile stress.
From seam welding to the start of tube expansion molding
Sufficient diffusion of diffusible hydrogen in weld metal with a time of 30 minutes or more
Even if the amount of diffused hydrogen remaining is small, welding
Lateral cracking of metal is likely to occur, and plastic deformation is large.
If it is too large, pipe expansion cracks (breaks at the weld HAZ position) will occur.
There is a risk of life. Accordingly, in the present invention, the tube expansion rate at the time of tube expansion molding.
Is defined as 5% or less. The lower limit of the tube expansion rate during tube expansion molding is particularly
Although it is not necessary to specify, the tensile strength of the base material is 800 MPa
With the above high strength UOE steel pipe, the expansion rate is too small
Then, since the roundness of the steel pipe deteriorates and it is not preferable in quality,
The lower limit is preferably 0.3% from the viewpoint of steel pipe quality.
Good. (Tensile strength of weld metal) FIG.
The time from welding to the start of tube expansion and the seam weld zone
Tensile strength of weld metal and occurrence of transverse cracks in weld metal
Shows the relationship. The flux used for seam welding
The amount of diffusible hydrogen inside is 10ml / 100g.
The expansion rate was 3%. From FIG. 2, tube expansion molding starts after seam welding.
It takes 30 minutes or more and the tensile strength of the weld metal
When the degree is 1400 MPa or less, the transverse crack of the weld metal is
Does not occur. On the other hand, the tensile strength of the weld metal is 1400.
If the pressure exceeds MPa, pipe expansion is started after seam welding.
A lateral crack occurs regardless of the time to start. The tensile strength of the weld metal is 1400 MPa.
In the following cases, welding metal
Less affected by increased sensitivity to hydrogen embrittlement
Therefore, the time from seam welding to the start of tube expansion forming
Sufficient diffusion of diffusible hydrogen in weld metal over 30 minutes
If the amount of remaining diffusible hydrogen is small, hydrogen embrittlement
Due to the synergistic effect with the suppression of cracks, transverse cracks do not occur. On the other hand, the tensile strength of the weld metal is 1400.
If it exceeds MPa, the weld metal will increase due to the increase in strengthening elements.
Increases susceptibility to hydrogen embrittlement of the genus, seam welding
Weld metal with a time of 30 minutes or more from the beginning until the start of tube expansion forming
The remaining diffusible hydrogen is fully diffused and remains
Even when the amount is small, lateral cracking is likely to occur. Follow
In the present invention, the tensile strength of the weld metal of seam welding
Is defined as 1400 MPa or less. (Tensile strength of weld metal to base metal
Ratio) In the present invention, a high strength U having a tensile strength of 800 MPa or more.
Targeting OE steel pipe, such high-strength UOE steel pipe
In the case of transverse cracking in the weld metal,
The occurrence of expanded cracks that break at the position of HAZ or weld metal
Life becomes a problem. In the present invention, the occurrence of transverse cracks in the weld metal is suppressed.
In order to prevent the occurrence of expansion cracks,
The upper limit of the tensile strength of the weld metal is 1400 MPa or more
As specified below, the tensile strength of the base metal
It is defined as 0.8 to 1.4 times the degree. The tensile strength of the weld metal is the tensile strength of the base metal.
If the strength exceeds 1.4 times, the seam weld will melt during pipe expansion.
If the plastic strain is excessively concentrated in the HAZ part,
I'm going to be. On the other hand, the tensile strength of the weld metal
If it is less than 0.8 times the shear strength, the seam weld
Since the tensile strength is too low compared to the base material,
It tends to break at the weld metal position of the seam weld. Follow
The tensile strength of the weld metal is 0.8% of the tensile strength of the base metal.
It is specified to be double to 1.4 times. In the present invention, the above-described manufacturing conditions are satisfied.
The tensile strength of the base material is 800 MPa or more,
High strength with diameter of 406mm or more and wall thickness of 10mm or more
In the manufacturing method of UOE steel pipe,
In addition, it prevents the occurrence of expansion cracks and has excellent quality and high strength U
OE steel pipe can be manufactured. The high-strength UO steel pipe of the present invention is an ordinary UO steel.
It can be manufactured using a tube manufacturing process. After pressing the steel sheet into a tubular shape, the butt section
Tack welding that is performed prior to seam welding
Even gas shielded arc welding, which has been used recently
Beam welding such as a laser may be used. Seam welding is a butt section machined into an X groove.
One layer of welding from the inner and outer surfaces of the steel pipe
It is done by doing. This seam welding has welding efficiency
High, wide tolerance range for groove shape, and tack weld metal
Submerged arc welding is preferred because it can remelt the genus.
From the viewpoint of improving welding efficiency, the first electrode
Is preferred for wire + pole DC electrode due to stability of penetration
Yes. For current and voltage conditions, internal welding penetrates tack welding
In other conditions, external welding completely remelts the tack weld.
These conditions are preferred. Also, the welding speed depends on the plate thickness,
It is about 1.5m / min at a plate thickness of 20mm, naturally fast.
The more preferable. A flat used for submerged arc welding.
Reduces the oxygen concentration in the weld metal and reduces the toughness of the weld metal
A medium or high basicity flag.
Is preferred. Further, the tensile strength which is the object of the present invention is 80.
The base material component of the steel pipe of 0 MPa or more needs to be specified in particular.
For example, C shown below: 0.02 to 0.12%,
Si: 0.35% or less, Mn: 0.5 to 2.0%, N
i: 0.02 to 4%, any one of Cr and Mo
May be steel containing two total amounts: 0.1 to 4%. Na
Here,% indicates mass% (the same applies hereinafter). C is low in cost when added to steel.
Can increase the strength, and the more you can, the lower the cost.
However, if it is too much, it will be in the welded HAZ part when seam welding is performed.
Hard structure called island martensite is generated and toughness
On the other hand, if too little, quenching
It is difficult to secure strength and toughness due to insufficient properties. Therefore, including C
The content is preferably 0.02 to 0.12%. Si is an island martensite in the welded HAZ.
It is a component that tends to form, and welding with too much added amount
In order to cause a reduction in the toughness of the HAZ part, its content is
It is preferable to set it to 0.35% or less. Mn increases hardenability and secures strength and toughness.
It is difficult to ensure strength and toughness
That's right. However, if the content exceeds 2.0%, ingot cracking
Cause. Therefore, the Mn content is 0.5 to 2.0%.
Is preferable. Ni, like Mn, has strength, toughness, especially toughness.
It is a component to ensure the property, addition of 0.02% or more
Is preferred. However, because it is too expensive and expensive,
It is not economical. Therefore, Ni content is 0.02-
It is preferable to make it 4%. Cr and Mo are both elements for ensuring strength.
If the amount is too small, the strength cannot be secured. And if it ’s too high,
The heat-affected zone becomes too hard.
It is not possible to prevent weld cracking by just adjusting. for that reason,
The total amount of either one or two of Cr and Mo is 0.00.
It is preferably 1 to 4%. P and S are components inevitably mixed,
To ensure toughness, P is 0.04% or less, S is 0.03%
It is preferable to limit to the following. In order to further improve the strength and toughness, Al,
Any one of Ti, Nb, V, B, Ca and Mg
You may add 1% or less of seed | species or 2 or more types by total amount. In addition, the formation of weld metal in the seam welds of steel pipes.
There is no particular restriction on the amount of wire, but the metal wire and flack
The weld metal material makes the weld metal component almost the same as the base metal component.
The same component system is preferred. But the line pipe
Many are used as welded and are assembled by rolling like the base material.
Operation such as securing strength and toughness cannot be performed by weaving control.
Therefore, considering the balance with the mechanical properties of the base material,
It is preferable to adjust the content of. Next, the present invention will be more specifically described based on examples.
explain. Table 1 shows the plate thickness and strength of the steel plate used in manufacturing the steel pipe.
Table 2 shows the degree and chemical composition of the flat used for seam welding.
Table 3 shows the welding conditions used for seam welding.
The chemical components of the wire are shown respectively. Table 4 shows steels in Tables 1 to 3.
Any combination of plate and seam welding conditions
Welding and pipe expansion conditions are within the scope of the present invention (example of the present invention).
And after manufacturing UOE steel pipe outside the range (comparative example), weld metal
The occurrence of lateral cracks and pipe cracks is shown. Table 2
The high basicity-melting flux shown in FIG. ₂ : 1
0%, Al ₂ O _Three : 25%, CaO: 15%, CaF ₂ :
35%, other components: 15%, particle size: 80 or less
The one from Mesh was used. Also, high basicity-fired type
The basic component system is the same as the melt type flux.
The total amount of Fe, Si, Mn, and Ni as alloy materials
Add about 5% and granulate with water glass at 480 ° C.
What was baked was used. Also, the diffusivity in the flux in Table 4
The amount of hydrogen is adjusted for each flack stored in a sealed state as shown in Table 2.
Each flux is stored in a sealed manner.
Left open for about 4 days to increase the amount of diffusible hydrogen
It was done by using. It should be noted that the diffusivity in the flux in Table 4
How to measure the amount of hydrogen in JIS Z3118 steel weld
In accordance with the law, use No. 2 test piece, AC 625A, voltage 3
0V, welding speed 60cm / min, wire attached 30m
After welding at m, the diffusible hydrogen content is measured by gas chromatography.
It was. At this time, the wire is shown in Table 3 as WC: diameter 4.8 mm
And the flux is the same conditions used for the welding test
I used one. The welding wires are WA, WB, WC shown in Table 3.
These three types are used in different combinations depending on the strength of the base material.
It was. Observation of transverse cracks in the weld metal is performed by visual inspection, PT and
And RT (Radiation transmission test of JIS Z3104 high weld zone)
7 after seam welding with the method and grade classification of transmission photographs)
After 2 hours. For the manufacture of the pipe, a steel plate with a length of 8 to 10 m is used.
After cutting to the required width for the tube size, the end is welded to the seam
Beveled so that becomes X groove, then U press,
O-press was performed and processed into a cylindrical shape. Then tack welding
As a heat input 6.5k using 570MPa class wire
Full wire welding from outside of steel pipe by J / cm carbon dioxide welding
did. After this, use the wires shown in Table 3 and
The same condition from the inner surface of the steel pipe and then the outer surface.
Seam welding by 1-pass submerged arc welding
went. Tube expansion after seam welding is performed by hydraulic pressure from the inner surface.
Pipe outer circumference before and after pipe expansion
Measure the thickness using a tape measure, and the tube expansion rate from the following formula (1)
Asked. (Expansion rate) (%) = ((peripheral length after tube expansion) − (peripheral length before tube expansion)) / (peripheral length before tube expansion) × 100 (1) execution number 1 Example of the invention is a plate thickness of 16mm, strong
A steel pipe having an outer diameter of 930 mm at a degree of 1050 MPa is used as diffusible water.
A melt flux with a high basicity of 4ml / 100g
3 electrode sub-arc welding, and after 40 minutes expansion of 2%
Tube forming. The weld metal strength at this time is 1077 MP.
a, weld metal strength / base material strength is 1.03. This place
If the condition of the present invention is satisfied,
Can produce sound UOE steel pipes without cracks
It was. The invention example of execution number 2 is the invention of execution number 1.
The same components as in the example, plate thickness 25 mm, strength 1010 MPa, outside
A steel pipe with a diameter of 457 mm is used as a diffusible hydrogen amount of 18 ml / 100.
3 electrode submerged arc using high basic melt flux
Welding was performed, and after 40 minutes, the tube was formed at a tube expansion rate of 5%. This
The weld metal strength of mushroom is 1145 MPa, weld metal strength / mother
The material strength is 1.35 and the strength of the weld metal is high. However, the expansion
After 30 minutes, the amount of diffusible hydrogen, the expansion rate, and dissolution
Lateral cracking of weld metal because the strength of metal contact is also within the scope of the present invention.
And a sound UOE steel pipe without cracks
The The invention number of run number 3 is 14 mm thick, strong
A steel pipe having a degree of 1190 MPa and an outer diameter of 762 mm is made of diffusible water.
High basicity molten flux with a basic volume of 10ml / 100g
3 electrode submerged arc welding, and after 35 minutes tube expansion rate of 1%
Tube expansion was performed. The weld metal strength at this time is 1030MP.
a, weld metal strength / base material strength 0.87. in this case
However, because it is within the condition range of the present invention,
In addition, a sound UOE steel pipe free from cracks is obtained. The embodiment number 4 of the present invention has a plate thickness of 32 mm,
A steel pipe having a strength of 830 MPa and an outer diameter of 930 mm is made of diffusible water.
Sintered flux with high basicity of 5ml / 100g
4 electrode sub-arc welding is used, and after 35 minutes, the expansion rate is 3%.
Tube forming. The weld metal strength at this time is 805 MPa,
In this case, the weld metal strength / base material strength was 0.95.
Satisfying the conditions of the present invention,
A sound UOE steel pipe without expanded cracks is obtained. The comparative example of run number 5 is the invention of run number 1.
Steel pipe of the same material and dimensions as the example under the same welding conditions
Welded, but expanded 20 minutes after seam welding.
A transverse crack occurred in the weld metal. The comparative example of execution number 6 is the invention example of embodiment 2.
Steel pipes of the same material and dimensions as those under the same welding conditions
However, since it was expanded 25 minutes after seam welding,
Lateral cracks occurred in the metal contact. The comparative example of execution number 7 is the invention example of embodiment 2.
A steel pipe with the same components and a thickness of 25m, and a high basicity melt type
Three-electrode subarc welding was performed with flux. Expansion in weld metal
The amount of diffuse hydrogen is 15 ml / 100 g. The seam
20 minutes after welding, the tube was formed with a tube expansion ratio of 5%. This is dissolved
Cracks were not observed due to the low strength of the metal, but
The strength of metal contact is low, and pipe expansion cracks occur at the weld metal position.
It was. The comparative example of execution number 8 has a plate thickness of 14 mm,
A steel pipe with a strength of 1190 MPa and an outer diameter of 762 mm
Highly basic molten flack with a hydrogen content of 22ml / 100g
The strength of the weld metal is 1340 MPa with 3 electrodes
Submerged arc welding was performed under the conditions of Expansion time is 40 minutes
Later, the tube expansion rate is within the scope of the present invention.
The flux left unopened for about 4 days.
A transverse crack has occurred in the weld metal due to the excessive amount. The comparative example of run number 9 is the invention of run number 4.
The same material as the example, plate thickness 32mm, strength 930MPa, outer diameter
Using a 930mm steel tube with a high basicity sintered flux
4 electrode sub-arc welding, weld metal strength is 890 MPa
Then, after 40 minutes, the tube was expanded at a tube expansion rate of 2%. Expansion period,
The weld metal strength and tube expansion rate satisfy the conditions of the present invention.
Yes. In addition, the strength of the weld metal is low and it is effective against transverse cracks.
The flux used at this time is open for about 4 days.
Sealed and diffusible hydrogen content 24ml / 100g
Therefore, transverse cracks were observed in the weld metal. The comparative example of execution number 10 has a plate thickness of 16 mm,
A steel pipe with a strength of 1050 MPa and an outer diameter of 930 mm is diffused.
High basicity melt flux with 5ml / 100g hydrogen
With 3 electrodes, weld metal strength 1500 MPa
Submerged arc welding with metal contact strength / base material strength of 1.42 and 3
After 5 minutes, the tube was expanded at a tube expansion rate of 5%. Expansion time and diffusivity
Although the amount of hydrogen is within the range of the present invention, the weld metal
Strength is excessive and weld metal strength / base metal strength is as high as 1.42.
In addition to the occurrence of transverse cracks in the weld metal, welding HA during pipe expansion forming
Tube expansion cracks occurred at the Z position. The comparative example with run number 11 is
The plate thickness is 16 mm and the strength is 1050 MPa under the same conditions as the light example.
A steel pipe with an outer diameter of 930 mm is used as a diffusible hydrogen amount of 4 ml / 100.
3 g using high basic melt flux,
The weld metal strength is submerged arc welding under the condition of 1079 MPa, 45
After a minute, the tube was formed with a tube expansion ratio of 7%. The expansion rate is excessive
In addition, minute transverse cracks were confirmed in the weld metal, and tube expansion molding
Sometimes pipe cracking occurred at the weld HAZ position. [Table 1] [Table 2] [Table 3] [Table 4] According to the present invention, natural gas or crude oil can be used for a long time.
Pull used in line pipes for distance transportation
Of high-strength UOE steel pipe with a large diameter of 800 MPa or more
In the manufacturing method, productivity decreases and manufacturing costs increase,
Furthermore, there are few restrictions on the component design of the base metal and weld metal.
And mechanical properties of steel pipes such as the toughness of seam welds
While maintaining, transverse cracks in the weld metal in the seam, and further expansion
It is possible to prevent pipe expansion cracks during pipe forming. As a result, the use of gas and oil is increased,
High-pressure transportation and transportation effectiveness for reasons such as transportation cost reduction
Increasing line pipe size, thickness and strength to increase rate
The tensile strength that can meet the needs of 800N / mm ² Less than
Manufacture the above high strength UOE steel pipe with high quality and high production
I can expect that.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows general UOE steel pipe manufacturing steps (a) to (i).
FIG. FIG. 2 is a diagram showing the relationship between the time from seam welding to the start of tube expansion forming, the amount of diffusible hydrogen in the flux used during seam welding, and the occurrence of transverse cracks in the weld metal. FIG. 3 is a diagram showing the relationship between the time from seam welding to the start of tube expansion forming, the tube expansion rate during tube expansion forming, and the occurrence of transverse cracks in the weld metal. FIG. 4 is a diagram showing the relationship between the time from seam welding to the start of tube expansion forming, the tensile strength of the weld metal in the seam weld, and the occurrence of transverse cracks in the weld metal. [Explanation of Symbols] 1 Steel plate 2 Plate width adjustment, groove processing 3 End bending 4 U forming 5 O forming 6 Tack welding 7 Inner seam welding 8 Outer seam welding 9 Tube expansion forming

──────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme code (reference) B23K 35/362 310 B23K 35/362 310A // C22C 38/00 301 C22C 38/00 301A 38/58 38 / 58 B23K 101: 06 B23K 101: 06 (72) Inventor Hideki Miyazaki No. 1 Kimitsu, Kimitsu Shin Nippon Steel Co., Ltd. (72) Inventor Tatsuya Yoshida No. 1 Kimitsu, Kimitsu Nippon Steel Corporation Kimitsu Steel Works (72) Inventor Kunio Koyama 20-1 Shintomi, Futtsu Shin Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Koichi Shinada 20-1 Shintomi, Futtsu Shin Nippon Steel Co., Ltd. F-term (Reference) 4E001 AA03 BB05 CA02 DC05 DG02 EA02 EA07 4E028 CB04 CB06 CB08 4E063 AA01 BA09 4E084 AA03 AA07 AA12 AA20 BA02 BA03 BA04 BA06 BA25 BA27 CA03 CA1 2 CA14 DA16 EA02 GA03

Claims (1)

What is claimed is: 1. In a method for producing a high-strength UOE steel pipe having a tensile strength of a base metal of 800 MPa or more, an outer diameter of 406 mm or more, and a wall thickness of 10 mm or more;
After tack welding the butt joint, the amount of diffusible hydrogen is 20 ml /
A seam by submerged arc welding of the inner and outer surfaces of a steel pipe using a welding flux of 100 g or less, under conditions where the tensile strength of the seam weld metal is 1400 MPa or less and the tensile strength of the base metal is 0.8 to 1.4 times. High strength UOE characterized in that welding is performed, and after 30 minutes or more have elapsed from the end of the welding, the tube expansion rate is 5% or less.
Steel pipe manufacturing method.