JPS62156087A - Production of steel pipe of clad steel - Google Patents

Abstract

PURPOSE:To prevent the reduction in toughness of a weld zone by resistance welding by forming a dissimilar two layer strip plate in a cylindrical clad blank pipe and by diluting the dissimilar metal by performing a welding and solidification along the welding seam in which the dissimilar metal is immersed. CONSTITUTION:The clad blank pipe of cylindrical shape is formed by continuously feeding the two layer strip plate of a base metal (low alloy part) 4 and cladding metal (high alloy part) 5 and the seam edge part thereof is subjected to a resistance welding. In this case the welding seam 8 that the base metal 4 is immersed in the cladding metal 5 is formed on the weld zone. The dissimilar metal is therefore diluted by performing welding and solidification treatment 9 upto the depth of a clad interface part 14 by a TIG electrode 10, etc. along the welding seam 8. In this way the metallic property of the weld zone is improved and the clad steel pipe having the function of a clad steel and having the sound seam part 8 causing no welding defect is obtd.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a method for manufacturing a clad steel pipe.

"Conventional technology" ERW steel pipes are made by forming strips into a tubular shape as is well known.

The opposing end faces are heated and melted using high-frequency current, and then welded and welded using squeeze rolls to form a tube.

In the manufacturing of ERW steel pipes, in order to prevent the occurrence of penetrator defects, which are unique weld defects, and to stably obtain high toughness at the /8 joint, the amount of upset by the squeeze roll should be increased to prevent oxidation melting. Measures have been taken to discharge the material to the outside surface of the tube 11 to make the joint melting width as small as possible (about 0.1 mm). FIG. 2 shows a cross section of a welded part of a normal electric resistance welded steel pipe.Since the heated opposing end surfaces are pressed together by a high upcent, the hot form 2 part 1 is plastically deformed.

The metal on the outer surface of the tube rises toward the outer surface, and the metal on the inner surface of the tube rises toward the inner surface, with the center of the thickness of the steel tube as the boundary.

In the figure, 2 indicates a seam portion, and 3 indicates a metal flow.

"Problems to be Solved by the Invention" By the way, when clad steel plates are electrically welded, the welded part is
As shown in FIGS. 3a, b, and c, the molten steel and heat-affected zone of the base material 4 penetrate into the metal seam of the inner or outer surface or both sides of the laminate 6a due to the high upset.
, 6b was discovered through experiments by the present inventors. 7a in the figure.

7b, 7c show ERW seams. When a cratted steel pipe that caused the above phenomenon was actually used as a pipe.

For example, a clad ERW steel pipe with a welded part as shown in Figure 3a, in which the outside metal (laminated material) is stainless steel and the outside metal (base material) is low-alloy steel, is made with a corrosion-resistant material on the inside. When used in an environment where stainless steel is required, the corrosion resistance of the stainless steel seam deteriorates significantly due to the infiltration of low-alloy steel, making it ineffective as a corrosion-resistant steel pipe.

Furthermore, if a type (b) in which the metals on the inner and outer surfaces of the tube are reversed is used in an environment where corrosion resistance is required on the outer surface of the tube, the corrosion resistance on the outer surface of the tube will be significantly degraded. That is, clad steel pipes having the welded portions shown in FIG. 3a, FIG. 3S, or FIG. 3C often do not exhibit the effect of cladding.

If the amount of upset is made smaller, the deformation of the heat-affected zone will be smaller, and the amount of intrusion of dissimilar metals can be reduced.

As mentioned above, not only is the toughness of the welded part reduced, but penetrator defects tend to occur frequently, which can easily become a starting point for brittle fracture, resulting in a loss of reliability in terms of safety.

``Means for solving problems'' and ``effects'' The present invention was made in view of the current situation, and its gist is that low alloy steel and high alloy steel are continuously fed. After forming a two-layer strip plate consisting of a cylindrical clad pipe into a cylindrical clad pipe and performing electric resistance welding on the seam edges, melting and solidification treatment is performed along the weld seam where dissimilar metals have penetrated. By diluting the material, the metal properties of the relevant part are improved, and it is possible to manufacture a clad steel pipe that has the functions of clad steel and has a sound seam part without welding defects.

That is, the first invention is as shown in FIG. 1a.

A melting/solidification treatment 9 is applied to the depth of the cladding interface along the weld seam 8 where dissimilar metals on the inner or outer side of the steel pipe have penetrated.

Any heat source capable of melting and solidifying may be used as the melting/solidifying method, such as a TIG arc heat source, plasma arc heat source, or laser heat source. In the figure, 10 indicates a TIG electrode.

As a result, the intruding dissimilar metal is diluted in the molten/solidified metal base material, but the molten/solidified metal and the molten/solidified metal base material show almost the same composition, resulting in an improvement in the circumference of the molten/solidified metal. It functions as clad steel at any position in the direction.

In addition, the second invention is to further increase the above-mentioned dilution degree, and as shown in FIG. After welding ILL and L with the same kind of metal,
The overlay welded portion is rolled using internal and external rolling rolls 12 and 13 to the guaranteed thickness of the steel pipe.

Is TIG the overlay welding method? 'g contact, MIG
welding.

Any welding method that allows overlaying, such as plasma welding or laser welding, can be used as filler wire.

If the same type of metal as the metal on the overlay welding side or a dissimilar metal is diluted by welding, it is desirable to design the composition of the filler wire so that the composition and performance of the deposited metal fall within the specified range, taking into consideration the amount of dilution of the dissimilar metal. Yes.

As for the method of rolling the overlay metal, it is desirable to roll it from the inner and outer surfaces using rolling rolls as shown in Figure 1.

Note that 14 in Figure 1 indicates the cladding interface.

"Example" Hereinafter, nine aspects of the present invention will be described in detail.

First, the first invention will be described.

The present inventors used a clad steel plate with a thickness of 8 fins and a width of 229 fins, consisting of 6 base materials (low alloy part), 1 interlocking material (SOS 304 parts), and 2 dragons, as shown in the diagram in FIG. After electrical resistance welding was performed so that the mating material (SOS 304 side) became the outer surface of the steel pipe on the production line, a TIG arc heat source was used to melt and solidify the outer surface seam of the steel pipe to the depth of the cladding interface to produce a clad steel pipe. The mechanical properties of the clad steel pipe manufactured by the method of the present invention and the corrosion resistance performance of the outer surface of the steel pipe were investigated.

The diagram in FIG. 5 shows the results of the flattening test, the spreading test, and the Charpy impact test. Henpei test (n number 100) is
Adhesion was good in both 0° flat and 90° flat. The spreading rate in the spreading test (n number 100) was 1.7
1 to 1.78X original outer diameter, which was good. ・Welded part by 2 crane V notch test pieces (■I impact test (N number 1
00), the absorbed energy at -40°C is 10
．． 8 to 17.3 kg-m/cm, indicating sufficient impact performance.

Degassing 3.5% based on JISGO577 on the outer surface of steel pipes.

The pitting potential (Vc'+oo) in NaCl was measured, but
It showed +〇, 3V vs SCE, and the corrosion resistance of the tube outer surface was good.

Next, the second invention will be described.

The present inventors electrically welded a clad steel plate with a thickness of 8 Tsuru and a width of 229 Dragon, consisting of 6 pieces of base material (low alloy part), 1 piece of laminated material (SO3304 parts): l'n, as shown in the diagram of Fig. 4. After welding and bead cutting on the steel pipe manufacturing line so that the mating material (SO5304 side) becomes the outer surface of the steel pipe.

Filler wire 2.4 consisting of the components shown in the diagram of FIG.
+n+φ was used to perform TIG overlay welding on the outer surface seam of the steel pipe, and the overlay welded portion was rolled using a rolling roller to produce a clad steel pipe. The mechanical properties of the clad steel pipe manufactured by the method of the present invention and the corrosion resistance performance of the outer surface of the steel pipe were investigated.

The diagram in FIG. 5 shows the results of the flattening test, the spreading test, and the Charpy impact test. Henpei test (n number 100) is
Adhesion was good in both 0° flat and 90° flat. The spreading rate in the spreading test (n number 100) was 1.7
The outer diameter was 5 to 1.79X, which was good.

Welded part 211■Impact test using notch test piece (n number 10
0), the absorbed energy at -40℃ is 10.4
~19.3 kg-m/am, indicating sufficient impact performance.

Degassing 3.5% based on JISGO577 on the outer surface of steel pipes.

The pitting corrosion potential (VC'+oo) in NaC12 was measured and showed +0.3V vs SCE, indicating that the corrosion resistance of the tube outer surface was good.

"Effects of the Invention" As described above, according to the method of the present invention, a continuously fed strip of clad steel is formed into a cylindrical blank tube, and the joint edges are electrically welded. Stay.

It has become possible to manufacture a clad steel pipe with a sound seam, which has no welding defects in the seam, and the cladding ratio in two circumferential directions is almost constant, and which functions as a clad steel without the intrusion of dissimilar metals.

[Brief explanation of drawings]

Figures 1a and b are explanatory diagrams showing the melting and solidification treatment of the electric resistance welded part of clad steel in the present invention, Figure 2 is an explanatory diagram of the C cross-section metal flow shape of the electric resistance welded part of a bare steel plate, and Figure 3a,
b, c are cross-sectional views of the electric resistance welded parts of clad steel, Fig. 4 is a diagram showing the chemical composition of the clad steel plate used in the embodiment of the method of the present invention, and Fig. 5 shows the mechanical properties as a result of implementing the present invention. The chart shown in FIG. 6 is a chart showing the chemical composition of the filler wire used in the embodiment of the method of the present invention. 1... 8 parts of hot form, 2... Seam part, 3... Metal flow, 4... Base material, 5... Laminating material + 6a
+ 6b...Intruding foreign metal, 7a, 7b, 7c
...ERW seam, 8... Welding seam, 9... Melting/solidification treatment, 10... TIG electrode, 11... Overlay welding, 12.13... Inner and outer rolling rolls, 14・
...Clad interface. j rofuri

Claims (2)

[Claims] (1) A two-layer strip made of continuously fed low-alloy steel and high-alloy steel is formed into a cylindrical clad pipe, and the joint edges are electrically welded, and then the inner surface of the steel pipe is Alternatively, clad steel is produced by melting and solidifying the dissimilar metal of the outer surface metal along the weld seam where it has penetrated to the depth of the cladding interface, and diluting the dissimilar metal into the melting and solidifying base metal. Steel pipe manufacturing method. (2) A two-layer strip made of continuously fed low-alloy steel and high-alloy steel is formed into a cylindrical clad pipe, the seam edges are ERW welded and bead cut, and then different Overlay welding the surface seam of a steel pipe on the metal side that has a seam where metal has penetrated with the same type of metal, rolling the overlay metal part to the guaranteed thickness of the steel pipe, and adding the dissimilar metal to the overlay weld side metal. A method for manufacturing a clad steel pipe, which is characterized by dilution.