JP2017154150A - Method for production of electric resistance welding clad steel tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for electric resistance welding clad steel tubes having excellent characteristics of a welding part without applying additional welding treatment required in prior art.SOLUTION: A production method for electric resistance welding clad steel tubes comprises: applying beveling of both end parts of a hot-rolled steel band in a width direction to obtain a V type bevel having a bevel angle of 20 to 70° and a bevel depth of 10 to 50% of total wall thickness in such a form that a clad interface is pressed from a cladding material side into a radial thickness center side; and in electric resistance welding, blowing a shield gas 5 from the gas discharge port of a nozzle for shield gas blowing coordinating the gas discharge port 1A divided into three layers in an element tube circumferential direction, to a position of 5 to 300 mm upward from the upper end of a welded part 11 facing that part by controlling the flow rate B of gas discharge from the gas discharge port of the central layer among three layers to 0.5 to 50 m/s, and that rate A (m/s) of gas discharge from the discharge ports of the remaining both end layers to satisfy the expression of 0.01≤B/A≤10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an ERW welded clad steel pipe, and more particularly, to a method for manufacturing an ERW welded clad steel pipe having excellent weld characteristics as it is as an ERW weld.

  Usually, an electric resistance welded steel pipe is manufactured by forming a steel plate (also called a steel strip) into a tubular shape and welding the opposite ends of the steel strip heated and melted by high-frequency current by butt-pressing them with a squeeze roll. . In the case of ERW steel pipe, it is generally said that the characteristics of the welded part are inferior to that of the base metal, and in application of the steel pipe, guarantees such as toughness, strength and elongation of the welded part have always been discussed for each application.

  The cause of the deterioration of the characteristics of ERW welds is that an oxide-based welding defect called penetrator is caused by welded parts during ERW welding (specifically, the circumferential direction of the open pipe formed by rolling the strip) In many cases, the toughness is reduced or the strength is insufficient due to the remaining penetrator.

  Therefore, as a conventional technique, in order to remove the penetrator, which is the main cause of ERW welding failure, from the welded part, there is a measure to make the upset amount by the squeeze roll larger than the plate thickness and discharge the oxidized melt generated during welding to the pipe outer surface. Has been taken.

  However, when manufacturing an ERW welded clad steel pipe using a clad steel plate as a raw material, if the upset amount by the squeeze roll is larger than the wall thickness (plate thickness), as shown in FIG. When the molten steel and heat-affected zone are mixed into the metal seam of the laminated material on the inner surface, outer surface, or both sides, and if the amount of upset is excessive, the base metal is exposed to the inner surface of the steel pipe after welding bead cutting. As a result, the performance as a clad steel pipe that makes use of the superior properties of the laminated material is lost. For example, a stainless clad steel plate made of stainless steel for the inner surface of the tube and a low alloy steel for the outer surface of the tube is made of a material, and the amount of upset is larger than the wall thickness as described above. When a sewn welded stainless steel clad steel pipe is used in an environment where corrosion resistance is required on the inner surface of the pipe, the low alloy steel of the base material is mixed into the stainless steel side of the mating material or exposed to the inner surface of the stainless steel seam. Therefore, the corrosion resistance is remarkably lowered, and there is a problem that the required performance cannot be exhibited.

  In order to solve such a problem, Patent Document 1 discloses that at least a laminated material side bead in a welded bead obtained by butt-welding opposite clad steel plates or steel strips which are bent in a tubular shape is cut to a depth reaching the base material. A method for manufacturing a clad pipe that is removed and is subjected to overlay welding having the same properties as the laminated material at the cut-off portion is disclosed.

  Further, in Patent Document 2, after forming a clad steel strip into a blank tube and performing seam welding on the seam edge portion, it is melted and solidified to the depth of the clad interface portion along the weld seam into which a dissimilar metal has infiltrated. Clad steel pipe manufacturing method for diluting the dissimilar metal, or overlay welding a seam portion into which the dissimilar metal has infiltrated with the same type of metal as the laminated material, and rolling the build-up weld to dilute the dissimilar metal Is disclosed.

  Further, in Patent Document 3, in a method for manufacturing a clad steel welded steel pipe having an inner surface as a laminated material, at least a part of a laminated material butt of a tubular body having an inner surface as a laminated material by forming a clad steel original plate or an original coil is provided. A method for manufacturing a clad steel welded steel pipe is disclosed in which electric seam welding is performed and then the butt-unwelded portion is overlay welded.

JP 60-221173 A JP-A-62-156087 JP-A-5-154545

  However, all of the techniques described in Patent Documents 1 to 3 described above include cutting and removing the bead portion of the mating material and performing overlay welding after electro-welding (Patent Document 1), a TIG arc heat source along the welding seam, and the like. Since additional welding processes such as fusion / solidification or overlay welding (Patent Document 2) and overlay welding of the butt-unwelded part (Patent Document 3) are required, productivity is reduced and manufacturing costs are reduced. In addition to the increase, there is a problem that an additional build-up welding has an adverse environmental impact.

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

  The inventors have intensively studied to solve the above-mentioned problems, and as a result, the pipe tube range from the edge heating start point to the weld point of the pipe tube is not covered with a shield box, and the raw tube is within the pipe tube range. When the shield gas is blown from the top of the welded part to the welded part, the nozzle height, which is the height from the upper end of the welded part to the shield gas blowing nozzle, and the shielding gas to be blown In addition to appropriately controlling the flow rate, the shield gas blowing nozzle structure is divided into three or more layers in the circumferential direction of the raw tube, and the blowing gas flow rate from the gas discharge ports at both ends and the remaining It has been found that the oxygen concentration in the welded part can be significantly reduced by appropriately controlling the ratio of the flow velocity of the gas blown from the gas outlet of the layer.

  Further, as shown in FIG. 7, in the process preceding ERW welding, an opening is formed as a V-shaped groove having a shape in which the mating material side is pushed into the thickness center side at the end of the clad steel strip width which is a butt weld. By applying the pre-processing, the clad interface can be moved to the center of the wall thickness, thereby controlling the flow of the molten steel in the welded part of the clad steel during ERW welding, and the molten steel and heat-affected zone of the base metal However, it discovered that it could suppress that it mixes in the metal seam part of the laminated material located in the steel pipe inner surface side, and is exposed to an inner surface. Moreover, since the sufficient upset amount can be added by providing the V-shaped groove, the discharge of oxide is promoted. Further, 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, the ERW weld It has been discovered that a reduction in toughness and strength can also be prevented. Here, as the groove working method, it is necessary to push the clad interface toward the center of the wall thickness, and methods such as press working, rolling and roll forming can be applied.

Also, the ERW welded pipe with excellent weld properties means that the ratio H / D between the flat height H obtained by a flattening test in accordance with JIS G 3445 and the outer diameter D of the pipe is less than 0.3. It has been clarified by a number of evaluation tests so far that it has a weld with excellent fracture characteristics when this condition is satisfied. That is, the present invention is as follows.
(1) A hot-rolled steel strip made of clad steel consisting of a carbon steel base material and a stainless steel or nickel-base alloy laminated material is formed into a tubular shape, and both ends in the width direction of the hot-rolled steel strip are butt-welded and electro-welded. A method for producing an ERW welded clad steel pipe, wherein both ends in the width direction of the hot-rolled steel strip are pushed in advance from the laminated material side to the wall thickness center side before the ERW welding. The groove is formed into a V-shaped groove having a bevel angle of 20 to 70 ° and a groove depth of 10 to 50% of the total thickness, and the welded part is inactive during the electric resistance welding. By using the shielding method of the welded part of the ERW steel pipe which is gas shielded with the shielding gas composed of gas, the welded part is positioned at a position 5 to 300 mm above the welded part upper end with respect to the welded part with respect to the circumferential direction of the pipe. Shield gas spraying nozzle with gas outlets divided into three layers The shield gas is discharged from the gas discharge port of the gas, the gas discharge flow velocity B from the gas discharge port of the central layer of the three layers is 0.5 to 50 m / s, and the gas discharge ports of the remaining two end layers are used. The gas discharge flow rate A (m / s) is sprayed as a flow rate satisfying the formula, 0.01 ≦ B / A ≦ 10.
(2) In addition to the V-shaped groove, the base metal side of the both ends in the width direction is grooved to form an X-shaped groove. Production method.
(3) The shape of the gas discharge port is characterized by a rectangular shape having a length of 30 mm or more as a component in the direction of pipe passage and a width of 5 mm or more as a component in the element tube edge butting direction as a dimension ( The manufacturing method of the electric-resistance-welded clad steel pipe as described in 1) or (2).
(4) The width R, which is a component of the tube edge butting direction of the combined dimensions of all layers of the gas discharge port, is R / W> with respect to the maximum interval W between the end faces of the welded portion immediately below the gas discharge port. 1.0. The method for producing an electric resistance welded clad steel pipe according to any one of (1) to (3), wherein the relationship of 1.0 is satisfied.
(5) The electric resistance welded clad steel pipe according to any one of (1) to (4), wherein the gas contains 0.1% by mass or more of a reducing gas instead of the inert gas. Production method.

  ADVANTAGE OF THE INVENTION According to this invention, the electric resistance welded clad steel pipe which has the inner surface coat | covered with the laminated material over the whole surface including the electric resistance welding part, and was excellent in the fracture | rupture characteristic of a welding part can be manufactured.

It is the schematic which shows embodiment of this 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 the gas discharge | emission flow rate B and gas flow rate ratio B / A of shield gas. It is a diagram which shows the relationship between the gas flow rate ratio B / A of shielding gas, and the oxygen concentration of a to-be-welded part (element | tube pipe | tube edge butt | matching part). It is a diagram which shows the relationship between flat value H / D in the 90 degree flat test of an electric-welding stainless steel clad steel pipe, and the oxygen concentration of a to-be-welded part (element pipe edge butting | matching part). This is a schematic diagram showing the cross section of the weld when the upset amount is changed during ERW welding of ESR welded stainless steel clad steel pipe where the inner surface of the pipe is stainless steel and 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 ERW welding part before and behind ERW welding. It is a figure which shows an example of the groove processing by the fin pass roll of a groove processing machine, ie, a fin pass roll forming machine.

  The present inventors investigated in detail about the influence which the groove shape of the clad steel strip width direction end part used as a butt-welding part has on the flow of the molten steel and the plastic flow of the heat affected zone in the pressure welding process. The molten steel in the pressure welding process flows along the unmelted surface to the inner surface or the outer surface, and the outflow amount is proportional to the volume of the molten part of the welded part. When the volume is reduced, the outflow amount of the molten steel to the side having the groove is reduced. Therefore, a V-shaped groove is provided on the side of the clad steel strip in the width direction to reduce the amount of molten steel flowing out to the side of the laminated material, and the V-shaped groove is formed by pressing, rolling, roll forming, etc. 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 portion on the side of the mating material by forming the shape in which the laminating material side is pushed into the thickness center side by this method.

  Therefore, in the present invention, after cutting the inner surface bead of the ERW welded portion, the ERW welded clad steel pipe having the inner surface covered with the laminated material over the entire surface including the ERW welded portion is formed. In the form in which 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. A groove is formed on a V-shaped groove that is 10 to 50% of the groove. By performing butt electrowelding as the V-shaped groove, it is possible to prevent the base material from being exposed to the surface of the welded portion on the side of the mating material 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 cannot be maintained, and as a result, the discharge of oxide (penetrator) tends to be insufficient. On the other hand, if the bevel angle exceeds 70 °, the effect of suppressing the flow of the base metal to the molten steel and the heat-affected zone on the side of the joining material becomes insufficient, and the base metal is formed on the inner surface of the steel pipe after bead cutting of the inner surface of the ERW weld. Increased tendency to be exposed. In addition, it was confirmed that the bevel angle is particularly preferably 20 ° to 45 ° from the viewpoint of obtaining a sufficient amount of upset at the time of ERW welding.

  Also, if the groove depth is less than 10% of the total wall thickness, the effect of suppressing the mixing of the base metal into the welded portion of the molten steel and the welded material on the inner surface of the steel pipe in the heat-affected zone becomes insufficient, and the oxide (penetrator) If the amount of upset necessary for discharging is secured, the base material is mixed into the welded portion of the steel tube inner surface, and the base material is exposed on the inner surface of the steel pipe after bead cutting of the inner surface of the ERW weld. On the other hand, if the groove depth d exceeds 50% of the total wall thickness, the composition of the weld joint becomes a high alloy composition close to the composition of the laminated material, so that the fracture characteristics of the ERW weld are deteriorated.

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

  Note that line pipes used in highly corrosive environments require high corrosion resistance on the inner surface of the steel pipe through which the production fluid flows, and in such environments, stainless steel and nickel-based alloys, which are corrosion resistant alloys, meet the requirements, so the cladding The steel laminate was stainless steel or nickel-base alloy. In particular, SUS316L is preferable for stainless steel and Alloy625 and Alloy825 are preferable for a nickel-based alloy because of high corrosion resistance.

  FIG. 1 is a schematic view showing an embodiment of the present invention. A strip made of steel strip is continuously paid out with an uncoiler (not shown), corrected with a leveler (not shown), and sent in the pipe passing direction 20, while the width of the strip is rounded with a roll forming machine (not shown) to open a raw pipe (open pipe) The welded portion 11 which is a base tube edge butting portion formed by butting both end faces of the rounded width is composed of an electric resistance welding machine (a power supply means for heating an edge portion (not shown) and a squeeze squeeze roll (not shown). Thus, the electric resistance welding steel pipe 15 is obtained by electric resistance welding. Reference numeral 12 denotes an element pipe edge heating start point, and reference numeral 13 denotes a welding point indicating a pipe passing direction position where the welded part 11 is joined by the pressure welding. In some cases, an impeder (not shown) may be disposed on the inner surface side of the base pipe 10 to the ERW steel pipe 15. The outer diameter of the ERW steel pipe 15 exiting the ERW welder is adjusted by a sizer (not shown).

In the present invention, the entire range of the pipe passage direction from the raw tube edge heating starting point 12 to the welding point 13, or an area within the range where oxides are likely to be generated in the welded part (this area can be specified by preliminary investigation). ) As a shield range, and in this shield range, a shield gas spray nozzle (nozzle for short) 1 is arranged at a position immediately above the welded portion 11.
The nozzle 1 is disposed with its gas discharge port 1 </ b> A positioned so as to face the upper end of the welded part 11.
In this invention, the nozzle 1 shall be divided | segmented into 3 layers with respect to the raw-tube peripheral direction 30, as shown in FIG.1 (b) and FIG.2 (a), (d). These layers form gas passages independent of each other. Still further, the central layer 1C of the three layers may be divided into two or more layers with respect to the raw tube circumferential direction 30, as shown in FIGS. 2 (b) and 2 (c). The two end layers 1E are one layer each.

  In the present invention, the shield box that covers the entire circumference of the element tube 10 within the shield range as described in the background art may not be provided. Rather, it is not provided in this embodiment because it is preferable not to provide it from the viewpoint of pipe making efficiency and manufacturing cost of the ERW steel pipe.

  The inventors have observed in detail the flow of the shielding gas. Furthermore, various shield gas spraying 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 center layer 1C and the both end layers 1E are affected by the coverage during the electric resistance welding. The influence on the oxygen concentration of the welded part 11 and the area ratio of the oxide in the welded part formed by electro-welding the welded part was investigated in detail.

  As a result, it was discovered that by optimizing the spraying conditions of the shielding gas, the oxygen concentration of the welded part becomes 0.01% by mass or less, and the oxide area ratio of the welded part becomes less than 0.1%. did. Here, the oxide area ratio of the weld is defined as follows. That is, a fracture surface obtained by conducting a Charpy impact test of an electric resistance welded portion is observed with an electron microscope at a magnification of 500 times or more and at least 10 visual fields, and a dimple fracture surface containing oxide observed in the fracture surface A portion was selected and its total area was measured, and the ratio of the total area of the visual field was defined as the oxide area ratio.

  The optimum condition found above 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 is performed. The flow rate B of the shield gas 5 at the outlet 1A is B = 0.5 to 50 m / s or less, and the flow rate A of the shield gas 5 at the gas discharge ports 1A of the both end layers 1E is 0.01 ≦ B This is a condition that the flow rate satisfies / A ≦ 10 (see FIG. 3).

  When the nozzle height exceeds 300 mm, the shield gas does not reach the welded part 11 sufficiently, and the oxygen concentration of the welded part 11 does not become 100 mass ppm or less. It is desirable that the nozzle height is small. However, if the nozzle height is less than 5 mm, the gas discharge port 1A is easily damaged by the radiant heat from the heated welded part 11, and the spatter generated in the welded part 11 collides. As a result, the durability of the nozzle 1 deteriorates.

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

  When the flow velocity B is too small, the shield gas diffuses to the surroundings, and the gas shield of the welded part 11 becomes insufficient. If the flow velocity B is too large, the momentum of the shielding gas becomes too strong, and the air is caught between the end faces of the welded part 11. Therefore, 0.5-50 m / s is an appropriate range for the flow velocity B. When the central layer 1C is further divided into a plurality of layers (for example, FIGS. 2B and 2C), the flow velocity B for the plurality of layers does not necessarily have the same value, and the appropriate range As long as it is within the range, the value may be different for each layer.

However, even if the flow rate B is kept in the proper range, if the gas flow rate ratio B / A, which is the ratio of the flow rate B and the flow rate A, is inappropriate, the air entrainment 6 is prevented as shown in FIG. It is difficult.
That is, when B / A <0.01, the gas flow from the both end layers 1E (the 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 element tube 10 and deflected upward, and the gas flow velocity in the reflection region becomes close to zero, and the air entrainment 6 along the outer surface of the element tube 10 cannot be prevented (see FIG. 3A). ), The oxygen concentration of the welded part 11 cannot 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 both end layers 1E is too weak. It is dragged between the end faces, and air entrainment 6 is likely to occur (see FIG. 3C), and the oxygen concentration of the welded portion 11 cannot be sufficiently reduced.

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

  4 shows an example in which the nozzle height is 50 mm, and the gas flow rate ratio B / A is variously changed under an appropriate range of the flow velocity B = 0.5 to 50 m / s, and the shield gas 5 is sprayed on the welded portion 11. It is a diagram which shows the result of having measured oxygen concentration in the intermediate position between the end surfaces of the to-be-welded part 11. FIG.

From FIG. 4, the oxygen flow rate ratio B / A is set to B / A = 0.01-10 under an appropriate range of flow velocity B = 0.5-50 m / s, whereby the oxygen concentration is 0.01 mass% or less. Can be cleared with a large margin (ie, surely).
From FIG. 4, it is preferable that B / A = 0.03 to 5 because an even lower oxygen concentration level of 0.001 to 0.0001 mass% can be achieved.

  By the way, about the shape which merged all the layers of gas discharge port 1A, if the length which is 20 components of the dimension through-tube direction is 30 mm or more, and the width which is the dimension of the element tube edge butting direction component is 5 mm or more, This is preferable because the gas spraying to the welded portion 11 can be made more uniform.

  Further, as shown in FIG. 1 (c), the width that is the component of the tube edge butting direction of the combined dimensions of all layers of the gas discharge port 1A is denoted by R, and the end surface of the welded portion 11 directly below the gas discharge port 1A It is preferable to satisfy R / W> 1.0, where W is the maximum interval between the two because the oxygen concentration of the welded part 11 can be reduced more quickly.

  An inert gas is used as the shielding 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 formed by mixing two or more of these.

  Further, as the shielding gas, a gas containing 0.1% by mass or more of a reducing gas may be used instead of the inert gas. However, this rather suppresses the generation of oxides that cause the penetrator. This is preferable because the effect becomes stronger and the toughness or strength of the welded portion can be greatly improved. Here, the reducing gas means hydrogen gas, carbon monoxide gas, methane gas, propane gas, or a mixed gas obtained by mixing two or more of these. In addition, as the gas containing 0.1% by mass or more of the reducing gas, the composition consisting of only the reducing gas or the composition containing the reducing gas: 0.1% by mass or more and the balance of the inert gas. Those are preferred.

From the viewpoint of availability and low cost, it is preferable to use the following gas as the shielding gas.
(B) When inert gas is used alone: (G1) Any one of nitrogen gas, helium gas and argon gas, or a mixed gas of two or more of these (b) When reducing gas is used alone: (G2) Hydrogen Gas, carbon monoxide gas, or a mixed gas of these two types (c) In the case of using a mixed gas of inert gas and reducing gas: mixed gas of (G1) and (G2) In particular, Needless to say, safety measures should be taken when using gas containing hydrogen gas and / or carbon monoxide gas.

  The uncoiler is made of stainless steel clad steel (SUS316L) with a 2 mm thick stainless steel (SUS316L) for the inner surface of the tube and a low carbon low alloy steel with a 5 mm thick base material for the outer surface of the tube. , Leveler, roll forming machine, groove processing machine, that is, fin pass roll forming machine, electric seam welding machine, sizer through this pipe making equipment arranged in this order, 300mm outer diameter welded stainless clad steel pipe In the process of manufacturing the gas shield, the gas spraying condition level and the upset amount are changed within and outside the scope of the present invention of the above-described embodiment when performing the gas shield to the welded part during the electric resistance welding. Prior to sewing welding, the groove condition is changed by performing groove processing by rolling using a fin pass roll with a device as shown in FIG. 8 at the end in the width direction of the clad steel strip. 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. Corrosion test results were evaluated as ◯ when no intergranular corrosion was observed, and x when intergranular corrosion was observed. The amount of upset by the squeeze roll is determined by measuring the outer peripheral length of the pipe before the squeeze roll, and then measuring the outer peripheral length of the pipe after welding with the squeeze roll and cutting the outer weld bead. It was obtained by calculating the difference of.

  As shown in Table 1, the present invention example has a welded portion in which the flatness value H / D of the welded portion is reduced by orders of magnitude compared to the comparative example, the fracture property is excellent, and the corrosion resistance as stainless steel is maintained. It was confirmed.

1 Nozzle (Shield gas spray nozzle)
1A Gas outlet 1C Center layer 1E Both end layers 2 Gas piping 3 Gas flow regulator 5 Shield gas 6 Atmospheric entrainment 10 Elementary tube (open tube)
11 Welded part (element tube edge butt part)
12 Element pipe edge heating start point 13 Welding point 15 ERW steel pipe 20 Through direction 30 Elemental pipe circumferential direction

Claims (5)

A hot-rolled steel strip of clad steel made of a carbon steel base material and a stainless steel or nickel-base alloy laminated material is formed into a tubular shape, and both ends in the width direction of the hot-rolled steel strip are butt-welded and electro-welded. A method of manufacturing a welded clad steel pipe,
Prior to the electric-welding welding, both ends in the width direction of the hot-rolled steel strip are in a form in which the clad interface is pushed from the laminated material side to the wall thickness center side, the bevel angle is 20 to 70 °, and the groove depth is Is subjected to groove processing with a V-shaped groove that is 10 to 50% of the total wall thickness,
At the time of the electric resistance welding, the welded part is gas shielded with a shielding gas made of an inert gas. The shield gas from the gas discharge port of the shield gas blowing nozzle in which the gas discharge ports divided into three layers with respect to the circumferential direction of the raw tube are arranged at a position 300 mm above the central layer of the three layers The gas discharge flow rate B from the gas discharge port is set to 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 expressed by the formula: 0.01 ≦ B / A A method of manufacturing an electric resistance welded clad steel pipe, characterized by spraying at a flow rate satisfying ≦ 10.   2. The method for producing an ERW-welded clad steel pipe according to claim 1, wherein in addition to the V-shaped groove, the base material side at both ends in the width direction is grooved to form an X-shaped groove.   2. The shape of the gas discharge port is a rectangular shape having a length of 30 mm or more as a component of a dimension in a pipe direction and a width of 5 mm or more as a component of a dimension of a raw pipe edge as a butt direction. 2. A method for producing an ERW welded clad steel pipe according to 2.   The width R, which is a component of the tube edge butting direction of the combined dimensions of all the layers of the gas discharge port, is R / W> 1.0 with respect to the maximum interval W between the end faces of the welded portion immediately below the gas discharge port. The method of manufacturing an electric resistance welded clad steel pipe according to any one of claims 1 to 3, wherein the following relationship is satisfied.   The method for producing an electric resistance welded clad steel pipe according to any one of claims 1 to 4, wherein a gas containing 0.1% by mass or more of a reducing gas is used instead of the inert gas.

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