JP6500810B2 - Manufacturing method of ERW welded clad steel pipe - Google Patents

Description

  The present invention relates to a method of manufacturing an ERW welded clad steel pipe, and more particularly, to a method of manufacturing an ERW welded clad steel pipe excellent in the characteristics of a welded portion as it is.

  Normally, ERW steel pipe is manufactured by forming a steel plate (also called steel strip) into a tubular shape, welding the opposite steel strip width ends heated and melted by a high frequency current with butting pressure with a squeeze roll and welding . In the case of ERW steel pipe, it is generally said that the properties of the welded part are inferior to the base metal, and in the application of the steel pipe, the guarantee of toughness, strength and elongation of the welded part has always been discussed for each application.

  The cause of the deterioration of the properties of the ERW welds is the oxide-based weld defect called penetrator, which is the welded portion at the time of ERW welding (specifically, the circumferential direction of the base pipe which is an open pipe formed by rounding a band material) In many cases, it was generated and remained on the raw pipe edge butt portion which is a portion where the both end faces are butted, and the toughness was lowered or the strength was insufficient due to the remaining penetrator.

  Therefore, in order to remove the penetrator, which is the main cause of welding resistance defects, from the welded area as prior art, the upset amount by the squeeze roll is made larger than the plate thickness, and measures are taken to discharge the oxide melt generated during welding to the pipe outer surface. It has been taken.

  However, when producing electric resistance welded welded steel pipe using clad steel sheet as a raw material, if the amount of upset by the squeeze roll is made larger than the thickness (plate thickness), as shown in FIG. In the case of excessive upset, the base steel is exposed to the inner surface of the steel pipe after weld bead cutting if molten steel and the heat affected zone are mixed in the metal seam of the joint material on the inner surface side or outer surface side or both sides As a result, the performance as a clad steel pipe which makes use of the superior properties of the joint material is lost. For example, a stainless steel-clad steel plate in which the joining material on the inner surface side is stainless steel and the base material on the outer surface of the pipe is a low alloy steel is used. When a welded stainless steel clad steel pipe is used in an environment where corrosion resistance is required for the inner surface of the pipe, the low alloy steel of the base material is mixed into the stainless steel side of the joining material or exposed on the inner surface. As a result, the corrosion resistance is significantly reduced and there is a problem that the required performance can not be exhibited.

  To address such problems, Patent Document 1 cuts at least the joint material side bead in a weld bead obtained by butt welding opposite edges of clad steel plates or steel strips bent into a tubular shape to a depth reaching the base material There is disclosed a method of manufacturing a clad tube which is removed and subjected to build-up welding having the same property as that of a joining material in a cutting removal portion.

  Further, according to Patent Document 2, after forming a clad steel strip into an element tube and performing seam welding at seam edges, melt and solidify to the depth of the clad interface along a weld seam in which dissimilar metals infiltrate, A method of producing a steel pipe of clad steel in which the dissimilar metal is diluted, or the seam portion in which the dissimilar metal infiltrated is welded by overlay welding with the same kind of metal as the joining material, and the weld overlay is rolled to dilute the dissimilar metal Is disclosed.

  Furthermore, in Patent Document 3, in the method of manufacturing a clad steel welded steel pipe using the inner surface as a joining material, at least a part of butt joint joining of a tubular body having an inner surface as an inner surface by forming an original clad steel plate or an original coil. A method of making clad steel welded steel pipe is disclosed which is welded by electric resistance welding and then weld butt welds.

Japanese Patent Application Laid-Open No. 60-221173 Japanese Patent Application Laid-Open No. 62-156087 JP-A-5-154545

  However, the techniques described in the above-mentioned Patent Documents 1 to 3 cut and remove the joint material bead portion and weld them after electric resistance welding (Patent Document 1), TIG arc heat source along the welding seam, etc. Because additional welding processes such as melting / solidifying or welding in place (Patent Document 2), welding butt welds in place (Patent Document 3), etc. are required, productivity is reduced, and manufacturing costs are increased. Along with the increase, there has been a problem that additional overlay welding causes adverse environmental effects.

  It is an object of the present invention to provide a method of making an ERW welded clad steel pipe having excellent weld properties without the additional welding process required in the prior art.

  The present inventors diligently studied to solve the above-mentioned problems, and as a result, without covering the through-tube range from the heating start of the edge portion of the blank tube to the welding point with the shield box, When the shield gas is sprayed from directly above the weld zone to the weld zone, the nozzle height which is the height from the upper end of the weld zone to the shield gas discharge port in the shield gas spray nozzle, and the shield gas to be sprayed In addition to appropriately controlling the flow velocity, the structure of the shield gas spray nozzle is divided into three or more layers in the circumferential direction of the base pipe, and the spray gas flow velocity from the gas discharge ports of both end layers and the remainder It has been found that the oxygen concentration in the weld zone can be significantly reduced by appropriately controlling the ratio of the flow velocity of the blowing gas from the gas outlet of the layer.

  Furthermore, as shown in FIG. 7, in the pre-process of ERW welding, the V-shaped groove is formed by pressing the laminated material side to the thick center side at the clad steel band width end to be a butt weld By pre-processing, the clad interface can be moved to the thick center side, thereby controlling the flow of molten steel in the weld zone of clad steel during electric resistance welding, and the molten steel and heat affected zone of the base material However, it has been found that it is possible to suppress the mixing into the metal seam portion of the laminated material located on the inner surface side of the steel pipe and the exposure to the inner surface. Further, by providing the V-shaped groove, a sufficient amount of upset can be added, thereby promoting the discharge of oxides. Furthermore, by providing the V-shaped groove, the temperature distribution of the entire surface of the joined portion is made uniform, so that the discharge of oxide from the ERW weld is promoted, and as a result, It has been found that a decrease in toughness and strength can also be prevented. Here, it is necessary to press the cladding interface to the thick center side as the groove processing method, and methods such as pressing, rolling, and roll forming can be applied.

In addition, with the ERW welded pipe excellent in the characteristics of the welded portion, the ratio H / D of the flat height H to the outer diameter D of the pipe obtained by the flat test in accordance with JIS G 3445 is less than 0.3 It has become apparent from the numerous evaluation tests so far that the weld portion has excellent weld fracture characteristics by satisfying this condition. That is, the present invention is as follows.
(1) A hot-rolled steel band of clad steel consisting of a base material of carbon steel and a joining material of stainless steel or nickel base alloy is formed into a tubular shape, and both ends in the width direction of the hot-rolled steel band are butt welded A method of manufacturing a welded seam welded clad steel pipe, in which both ends in the width direction of the hot-rolled steel strip are pressed in advance from the laminated material side to the thick center side before the welded seam welding. , Bevel angle 20 to 70 °, and groove depth is 10 to 50% of the total thickness V-shaped groove processing is performed to make the groove, and the welded portion is inactive at the time of the ERW welding Using the method of shielding the welded joint of a welded seamed steel pipe with a shielding gas consisting of gas, using a method of shielding the welded pipe at a position 5 to 300 mm above the upper end of the welded part with respect to the welded pipe circumferential direction Shield gas spraying nozzle with gas outlet separated into three layers Flow rate B from 0.5 to 50 m / s from the gas discharge port of the middle layer of the three layers, and the gas discharge ports of the other end layers The gas discharge flow rate A (m / s) of the formula, 0.01 ≦ B / A ≦ 10, and a method of manufacturing a seam welded welded steel pipe characterized in that the flow rate is satisfied.
(2) In addition to the V-shaped groove, the base material sides of the both widthwise end portions are grooved to form an X-shaped groove; Production method.
(3) The shape of the gas discharge port is a rectangular shape having a length of 30 mm or more, which is a passage direction component of the dimension, and a width of 5 mm or more, which is a raw tube edge abutting direction component of the dimension ((3) The manufacturing method of the electric resistance welding welded clad steel pipe as described in 1) or (2).
(4) The width R which is an element pipe edge abutting direction component having a dimension in which all layers of the gas discharge port are merged is R / W> with respect to the maximum distance W between the end faces of the welded portion immediately below the gas discharge port The method according to any one of (1) to (3), which satisfies the following relationship: 1.0.
(5) Instead of the inert gas, a gas containing 0.1 mass% or more of reducing gas is used. (1) to (4) Production method.

  According to the present invention, it is possible to manufacture an electric-resistance-welded clad steel pipe having an inner surface covered with a bonding material over the entire surface including the electric-resistance-welded portion and having excellent fracture characteristics of the welded portion.

1 is a schematic view illustrating an embodiment of the present invention. It is a schematic diagram which shows the example of the nozzle structure divided | segmented into the several layer. It is explanatory drawing which shows the appropriate range of gas discharge flow rate B of shield gas, and gas flow-rate ratio B / A. It is a graph which shows gas flow rate ratio B / A of shield gas, and the relationship of the oxygen concentration of a to-be-welded part (element pipe edge abutting part). It is a diagram which shows the relationship between the flat value H / D in the 90 degree flat test of a resistance welded stainless steel clad steel pipe, and the oxygen concentration of a to-be-welded part (element pipe edge abutting part). This is a schematic diagram showing the cross section of the weld when the upset amount at the time of ERW welding of ERW welded stainless steel pipe whose joint material on the inner surface side is stainless steel and the base material on the outer surface of the pipe is low alloy steel. is there. It is a schematic diagram explaining the shape of the cross section of the electric resistance welding part before and behind electric resistance welding. It is a figure which shows an example of the beveling process by the fin path roll of a bevel processing machine, ie, a fin pass roll forming machine.

  The present inventors investigated in detail the influence of the groove shape of the clad steel band width direction end portion which becomes a butt weld portion on the flow of molten steel in the pressure welding process and the plastic flow of the heat affected zone. The molten steel in the pressure welding process flows out to the inner or outer surface along the unmelted surface, and the amount of outflow is proportional to the volume of the melted portion of the welded portion, so groove processing is applied to the melted portion When the volume is reduced, the outflow of the molten steel to the side having the groove is reduced. Therefore, a V-shaped groove is provided on the joint material side of the clad steel strip width direction end to reduce the amount of molten steel flowing to the joint material side, and the V-shaped groove is pressed, rolled or roll formed It was found that the molten steel of the base material can be prevented from being exposed to the inner surface of the weld seam on the side of the joint material by forming the joint material side into the shape of the thick center side by the method described above.

  Therefore, in the present invention, after cutting the inner surface bead of the electric resistance welded portion, the electric resistance welded welded steel pipe having the inner surface covered with the bonding material over the entire surface including the electric resistance welded portion before electric resistance welding In the width direction both ends of the clad steel strip, the clad interface is pushed from the laminated material side to the thickness center side, the bevel angle θ is 20 to 70 °, and the groove depth d is the total thickness The beveling process is applied to the V-shaped groove which is 10 to 50% of the above. By performing butt welding as the V-shaped groove, it is possible to prevent the base material from being exposed on the surface of the weld on the side of the joint after bead cutting.

  If the bevel angle is less than 20 °, the uniformity of the temperature distribution at the weld joint interface from the center of the plate thickness can not be maintained, and as a result, the oxide (penetrator) tends to be discharged insufficiently. On the other hand, if the bevel angle exceeds 70 °, the flow control effect of the base material to the molten steel and heat-affected zone side becomes insufficient, and the base material is on the inner surface of the steel pipe after internal bead cutting of the electric resistance welded portion. There is a tendency to be exposed. In addition, it was confirmed that it is particularly preferable to set the bevel angle to 20 ° to 45 ° from the viewpoint of obtaining a sufficient upset amount at the time of electric resistance welding.

  In addition, if the groove depth is less than 10% of the total thickness, the effect of suppressing the mixing of the molten steel of the base material and the weld metal of the heat-affected zone inner surface of the steel pipe is insufficient. When the amount of upset necessary for discharge is secured, the base material mixes in the joint material weld portion on the inner surface side of the steel pipe, and the base material is exposed on the inner surface of the steel pipe after inner surface bead cutting of the electric resistance welded portion. On the other hand, if the groove depth d exceeds 50% of the total thickness, the composition of the weld joint has a high alloy composition close to the composition of the joint material, and the fracture characteristics of the electric resistance welded portion are degraded.

  Further, in addition to the V-shaped groove on the mating material side, it is preferable that the base material side is also grooved to form an X-shaped groove. By making the X-shaped groove, discharge of the penetrator at the time of ERW welding is promoted, and the fracture characteristics of the welded portion are improved.

  In addition, line pipes used in highly corrosive environments are required to have high corrosion resistance on the inner surface of the steel pipe through which the production fluid flows, and in such environments, the corrosion resistant alloys such as stainless steel and nickel base alloy satisfy the requirements. The joining material of steel was a stainless steel or a nickel base alloy. In particular, from the viewpoint of having high corrosion resistance, SUS316L is preferable for stainless steel and Alloy625 and Alloy825 for nickel-based alloys.

  FIG. 1 is a schematic view showing an embodiment of the present invention. Strip material consisting of steel strip is continuously dispensed by uncoiler (not shown), corrected by leveler (not shown), and fed in pipe direction 20, while width of strip material is rounded by roll forming machine (not shown) and raw tube (open tube) No. 10, welded portion 11 which is a raw tube edge butt portion formed by buttling the both end faces of the rounded width is composed of a ERW welder (consists of a feeding means for heating the edge portion not shown and a squeeze roll for pressure welding not shown) And the electric resistance welded steel pipe 15 is obtained. The reference numeral 12 denotes a base pipe edge heating point, and 13 denotes a welding point that indicates the through-direction position where the welded portion 11 is joined by the pressure contact. Note that an impeder (not shown) may be disposed on the inner surface side of the base pipe 10 to the ERW pipe 15. The electric resistance welded steel pipe 15 which has exited the electric resistance welder is adjusted in outer diameter by a sizer (not shown).

In the present invention, an area in which the oxide is likely to be easily formed on the weld area in the entire area of the pipe passage direction from the raw pipe edge heating point 12 to the welding point 13 or in the area (this area can be identified by preliminary investigation ) Is a shield range, and in the shield range, a shield gas spraying nozzle (abbreviated as a nozzle) 1 is disposed at a position immediately above the portion to be welded 11.
The nozzle 1 is disposed with the gas outlet 1A of the crucible aligned with the upper end of the portion 11 to be welded.
In the present invention, as shown in FIG. 1 (b) and FIGS. 2 (a) and 2 (d), the nozzle 1 is divided into three layers in the circumferential direction 30 of the base pipe. These layers form gas flow paths independent of one another. Furthermore, the central layer 1C of the three layers may be divided into two or more layers with respect to the base tube circumferential direction 30, as shown in FIGS. The two end layers 1E are one each.

  In the present invention, it is not necessary to provide a shield box covering the entire circumference of the raw pipe 10 in the shield range as mentioned in the background art. Rather, it is not provided in this embodiment because it is preferable from the viewpoint of the production efficiency of the ERW steel pipe and the manufacturing cost.

  The inventors observed in detail the flow of the shielding gas. Furthermore, various shield gas spray conditions such as the position and size of the gas discharge port 1A and the flow velocity of the shield gas at the gas discharge port 1A of each of the central layer 1C and the both end layers 1E The influence on the oxygen concentration of the welded portion 11 and the area ratio of the oxide in the welded portion formed by electric resistance welding of the welded portion was investigated in detail.

  As a result, by optimizing the spray conditions of the shield gas, it was discovered that the oxygen concentration in the weld zone was 0.01 mass% or less, and the oxide area ratio in the weld zone was less than 0.1%. did. Here, the oxide area ratio of the weld is defined as follows. That is, the fractured surface obtained by conducting the Charpy impact test of the electric resistance welded portion is observed by at least 10 fields of view at a magnification of 500 or more with an electron microscope, and the dimpled fractured surface including the oxide observed in the fractured surface The parts were selected, their total area was measured, and the ratio of this to the total area of the field of view was taken as the oxide area ratio.

  The optimum condition found is that the nozzle height, which is the height from the upper end of the welded portion 11 to the gas discharge port 1A, is 5 mm or more and 300 mm or less (see FIG. 1C), and the gas release of the central layer 1C The flow velocity B of the shield gas 5 at the outlet 1A is B = 0.5 to 50 m / s or less, and the flow velocity A of the shield gas 5 at the gas outlet 1A of the both end layers 1E is 0.01 ≦ B. It is a condition that it is a flow velocity that satisfies / A ≦ 10 (see FIG. 3).

  When the nozzle height exceeds 300 mm, the shield gas does not sufficiently reach the welded portion 11, and the oxygen concentration of the welded portion 11 does not become 100 mass ppm or less. The nozzle height is preferably small, but if it is less than 5 mm, the radiant heat from the heated welding portion 11 tends to damage the gas discharge port 1A, and further, the spatter generated at the welding portion 11 collides. As a result, the durability of the nozzle 1 is degraded.

  In order to control the flow rate within the above-mentioned optimum condition range, in the present invention, the flow rate of the shield gas released from the gas discharge port is equal to the gas release flow rate from the gas release port of the central layer 1C of the three layers. B is controlled to B = 0.5 to 50 m / s, and the gas release flow rate A from the gas discharge ports of the remaining both end layers 1E is controlled to the flow rate satisfying the formula 0.01 ≦ B / A ≦ 10. The gas flow regulator 3 (see FIGS. 1A and 1B) is included.

  If the flow velocity B is too small, the shield gas diffuses to the surroundings, and the gas shield of the portion to be welded 11 becomes insufficient. If the flow velocity B is too high, the force of the shield gas becomes too strong, and the air may be trapped between the end faces of the portion to be welded 11. Therefore, 0.5 to 50 m / s is an appropriate range of the flow velocity B. In the case where the central layer 1C is further divided into a plurality of layers (for example, FIG. 2 (b), (c), etc.), the flow velocity B for the plurality of layers does not necessarily have to be the same value. As long as it is inside, it may be different from layer to layer.

However, even if the flow velocity B is kept in the appropriate range, if the gas flow velocity ratio B / A, which is the ratio between the flow velocity B and the flow velocity A, is inappropriate, as shown in FIG. It is difficult.
That is, in the case of B / A <0.01, the gas flow from the both end layers 1E (flow of the shield gas 5) is too strong, and the gas flow from the central layer 1C is too weak. The flow is reflected on the outer surface of the raw tube 10 and deflected upward, and the gas flow velocity in the reflection region becomes close to zero, so that the atmospheric entrainment 6 along the outer surface of the raw tube 10 can not be prevented (see FIG. 3A) And the oxygen concentration of the welded portion 11 can not be sufficiently reduced.

  On the other hand, in the case of B / A> 10, the gas flow from the central layer 1C is too strong, and the gas flow from the both end layers 1E is too weak. It is dragged between the end faces, and the air entrainment 6 is easily caused (see FIG. 3C), and the oxygen concentration of the portion to be welded 11 can not be sufficiently reduced.

  On the other hand, by setting B / A = 0.01 to 10, the shielding gas 5 fills the end face of the portion to be welded 11 without excess or deficiency, and there is no air entrainment, and a sufficient gas shield can be achieved (see FIG. 3 (b)). In the flow velocity B at the gas flow velocity ratio B / A, when the central layer 1C is divided into a plurality of layers and the gas flow velocity from at least one layer of the plurality of layers is different from that of the other layers, the different gas Use the maximum flow velocity among the flow velocities.

  Incidentally, FIG. 4 sprays shielding gas 5 to the welding part 11 by changing the gas flow velocity ratio B / A variously under an appropriate range of the flow velocity B = 0.5 to 50 m / s with the nozzle height = 50 mm as an example. It is a graph which shows the result of having measured the oxygen concentration in the middle position between the end faces of welding part 11.

According to FIG. 4, the oxygen concentration is 0.01 mass% or less by setting the gas flow velocity ratio B / A to B / A = 0.01 to 10 under an appropriate range of the flow velocity B = 0.5 to 50 m / s. Can be cleared with a large margin (that is, surely).
Further, as shown in FIG. 4, when B / A = 0.03-5, 0.001 to 0.0001 mass% which is a still lower oxygen concentration level can be achieved, which is preferable.

  By the way, about the shape where all layers of the gas discharge port 1A are merged, if the length is 30 mm or more, which is the component of 20 in the through direction of the dimension, and the width is 5 mm or more. Gas spraying to the welding part 11 can be made more uniform, which is preferable.

  Further, as shown in FIG. 1 (c), the width which is the raw pipe edge butting direction component of the combined size of all the layers of the gas discharge port 1A is written as R, and the end face of the welded portion 11 directly below the gas discharge port 1A. It is preferable to satisfy the condition R / W> 1.0, where W is the maximum distance between the two, since the oxygen concentration in the portion to be welded 11 can be reduced more rapidly.

  An inert gas is used as the shield gas. The inert gas referred to here means nitrogen gas, helium gas, argon gas, neon gas, xenon gas or the like, or a mixed gas of two or more of these or the like.

  Furthermore, as the shielding gas, instead of the above-mentioned inert gas, a gas containing 0.1 mass% or more of a reducing gas may be used, but rather, this one rather suppresses the formation of an oxide causing a penetrator. The effect is stronger, and the toughness or strength of the welded portion can be greatly improved, which is preferable. The reducing gas referred to here means hydrogen gas, carbon monoxide gas, methane gas, propane gas or the like, or a mixed gas obtained by mixing two or more of these. In addition, as a gas containing 0.1 mass% or more of reducing gas, a composition consisting only of reducing gas, or a composition containing reducing gas: 0.1 mass% or more and the balance being an inert gas Is preferred.

Further, in terms of availability and cost, it is preferable to use the following gas as a shielding gas.
(A) In the case of using an inert gas alone: (G1) Any one or a mixture of two or more of nitrogen gas, helium gas and argon gas (b) In the case of using a reducing gas alone: (G2) hydrogen Gas, carbon monoxide gas any one or mixed gas of these two kinds (3) In the case of using mixed gas of inert gas and reducing gas: mixed gas of the above (G1) and (G2) In particular, When using a gas containing hydrogen gas and / or carbon monoxide gas, it goes without saying that safety measures should be taken without leakage.

  The uncoiler is made of stainless steel clad steel strip which is stainless steel (SUS316L) with a thickness of 2 mm and the base material of the surface with a thickness of 5 mm is a low carbon low alloy steel. Electric seam welded stainless steel clad steel pipe with an outer diameter of 300 mm through a pipe forming equipment configured by arranging a leveler, roll forming machine, beveling machine ie fin pass roll forming machine, ERW welder, and sizer in this order In the process of manufacturing a gas shield, the level of the gas spray condition and the amount of upset are changed within or outside the range of the present invention of the embodiment described above when performing the gas shield to the welding portion at the time of Before seam welding, groove end processing by rolling is performed in advance using a fin pass roll with an apparatus as shown in FIG. And forming tube under the conditions as shown in Table 1, the measurement of the oxygen concentration in the welded portion, 90 ° flattening test of the weld, and the inner surface side was subjected to corrosion test by oxalic acid etching. The corrosion test results were evaluated as ○ when no intergranular corrosion was observed and as × when intergranular corrosion was observed. The upset amount by the squeeze roll is measured by measuring the outer peripheral length of the pipe after the welding bead portion of the outer surface is cut by welding with the squeeze roll after measuring the outer peripheral length of the pipe in front of the squeeze roll. It calculated by calculating the difference of.

  As shown in Table 1, in the present invention example, the flat portion H / D of the welded portion is reduced by an order of magnitude compared to the comparative example, and the welded portion has excellent fracture characteristics and maintains corrosion resistance as stainless steel. That was confirmed.

1 nozzle (shield gas spray nozzle)
1A Gas Release Port 1C Central Layer 1E Both End Layers 2 Gas Piping 3 Gas Flow Regulator 5 Shield Gas 6 Atmospheric Inclusion 10 Element Tube (Open Tube)
11 Welded part (raw pipe edge butted part)
12 base pipe edge portion heating start point 13 welding point 15 ERW pipe 20 passage direction 30 core pipe circumferential direction

Claims (5)

A hot-rolled steel band of clad steel consisting of a base material of carbon steel and a joint material of stainless steel or nickel base alloy is formed into a tubular shape, and both ends in the width direction of the hot-rolled steel band are butt welded A method of manufacturing a seam welded clad steel pipe,
Before the ERW welding, both end portions in the width direction of the hot-rolled steel strip are arc-shaped such that the outer surface side of the base material becomes the outer bending side with respect to the thickness center side by rolling using fin pass rolls. Opening with a V-shaped groove with a bevel angle of 20 to 70 ° and a groove depth of 10 to 50% of the total thickness, with the interface pressed into the thickness center side from the laminated material side Pre-processing,
At the time of the electric resistance welding, using the base tube to-be-welded part shielding method of the electric welded steel pipe in which the to-be-welded part is gas-shielded with a shielding gas consisting of inert gas, 5 to 5 from the upper end of the to-be-welded part The shield gas is supplied from the gas discharge port of the shield gas spraying nozzle in which the gas discharge port is divided into three layers with respect to the circumferential direction of the raw pipe at a position 300 mm above, and the central layer of the three layers. The gas discharge flow rate B from the gas discharge port of 0.5 to 50 m / s, and the gas discharge flow rate A (m / s) from the gas discharge ports of the remaining both end layers is a formula, 0.01 ≦ B / A A method of manufacturing an ERW welded clad steel pipe characterized by spraying as a flow velocity satisfying ≦ 10.   The method of manufacturing an ERW welded clad steel pipe according to claim 1, wherein the base material sides of both widthwise end portions are grooved in addition to the V-shaped groove to form an X-shaped groove.   The shape of the gas discharge port is a rectangular shape having a length of 30 mm or more, which is a passage direction component of a dimension, and a width of 5 mm or more, which is a raw tube edge abutting direction component of a dimension. The manufacturing method of the electric resistance welding welded clad steel pipe as described in 2.   The width R which is an element pipe edge abutting direction component having a size in which all layers of the gas discharge port are merged is R / W> 1.0 with respect to the maximum distance W between the end faces of the welded portion directly below the gas discharge port. The method according to any one of claims 1 to 3, wherein the following relationship is satisfied.   The method for producing an ERW welded clad steel pipe according to any one of claims 1 to 4, wherein the inert gas is replaced with a gas containing 0.1 mass% or more of a reducing gas.

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