JP6036773B2 - Shielding device for welded part of bare pipe of ERW steel pipe and method for shielding welded part of bare pipe - Google Patents

Description

The present invention relates to a base pipe welded shield apparatus and base pipe welded shield how ERW steel pipe, in particular, for parts for oil well line pipe for and automobiles has high mechanical properties in the weld requirements is the can be preferably used in the production of electric resistance welded steel pipe, about the base pipe welded shield apparatus and base pipe welded shield how the electric resistance welded steel pipe.

  Usually, steel pipes are roughly divided into welded steel pipes and seamless steel pipes. Welded steel pipes are manufactured by rounding a plate (meaning of a strip, the same shall apply hereinafter) and welding the end parts, as in the case of ERW steel pipes. Seamless steel pipes are used to drill a lump of material at a high temperature. And it is manufactured by rolling with a mandrel mill or the like. In the case of a welded 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, guarantees such as toughness, strength and elongation of the welded part have always been discussed for each application.

  For example, line pipes that transport crude oil, natural gas, and the like often require low-temperature toughness because the pipes are often laid in cold regions, and the strength of the pipes is important.

  In general, a hot-rolled steel sheet that is a base material of a steel pipe is designed in consideration of the base material characteristics after manufacturing the steel pipe, and characteristics such as strength are ensured.

  However, since the characteristics of the welded part are greatly influenced by the electric resistance welding method rather than by the base material component design, heat treatment, etc., it was important to develop a welding technique. The cause of poor ERW welding is that an oxide-based welding defect called a penetrator butts the welded parts during ERW welding (specifically, the circumferential ends of the element pipe, which is an open pipe made by rolling a band material) In many cases, the toughness is reduced or the strength is insufficient due to the residual penetrator.

  Therefore, in order to remove the penetrator, which is the main cause of ERW welding failure, from the welded part as a conventional technique, the technique of preventing oxidation of the welded part by gas blowing to the welded part or the shape of the end face of the strip material immediately before ERW welding There has been proposed a technique for removing the penetrator from the welded portion by making the shape into an appropriate shape.

  For example, in Patent Document 1, in a welded part shielding device for an electric resistance welded tube, welding is performed on a roll stand of a squeeze roll in order to reduce the oxygen concentration around the welded part in a short time with the sealed space around the welded part as the minimum volume. It is described that a shield cover that covers only the welding device around the part and the local part of the raw pipe is attached.

  Further, in Patent Document 2, an impure gas liquefied gas pipe is provided in an impeder case inserted in a raw pipe, and the impeder core is cooled with the supplied liquefied gas, and then the liquefied gas is ejected toward the welding point. And gas shielding is described.

  Patent Document 3 discloses that a welded part is gas shielded during welding (pressure welding) to reduce the oxygen concentration and reduce the amount of oxide generated, and a laser beam or plasma arc is applied to the welded part during high-frequency heating. It is stated that the occurrence of welding defects is prevented by irradiation.

  In Patent Document 4, the entire pipe passage route from the edge heating starting point to the welding point of the raw pipe is covered with the edge heating coil and squeeze roll together with a shield box, and gas is supplied into the shield box. It is described that gas is supplied at a predetermined flow rate through a pipe.

Japanese Patent Laid-Open No. 08-300164 Japanese Patent Laid-Open No. 10-249547 JP-A-5-23867 JP 2011-206913 A

  However, the method of gas shielding only by welding the vicinity of the welding point from the outer surface side (Patent Document 1) or from the inner surface side (Patent Document 2) is poor in reproducibility and cannot be shielded sufficiently, and the welded portion is oxidized. Things may remain.

  Moreover, the method of irradiating a plasma arc or the like to a welding point (Patent Document 3) requires an irradiation device such as a plasma arc in addition to the gas shield device, which causes a disadvantage in terms of pipe making cost.

  In addition, the method of covering the entire pipe path from the edge heating start point of the raw pipe to the welding point with a shield box (Patent Document 4) has a complicated device structure and requires a lot of time for assembly, Each time the dimensions of the pipe change, it is necessary to replace or adjust the shield box, and there is a problem that the disadvantage in terms of efficiency and pipe making cost is great.

  As described above, in the conventional technology, the welded part at the time of ERW welding can be surely gas shielded and the oxygen concentration can be sufficiently reduced without sacrificing the pipe making cost and the efficiency. There was a problem that the generation of the penetrator could not be prevented.

Therefore, in view of the above-mentioned problems of the prior art, the present invention reliably gas shields the welded part at the time of ERW welding without sacrificing the pipe making cost and the efficiency, so that the oxygen concentration thereof is sufficient. providing a base pipe welded shield apparatus and base pipe welded shield how ERW steel pipe which can prevent the formation of penetrators is lowered to, and an object of the present invention is to solve.

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 spraying shield gas from directly above 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 discharge nozzle in 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 The present inventors have found that the oxygen concentration in the welded portion can be significantly reduced by appropriately controlling the ratio of the flow velocity of the blowing gas from the gas discharge port of the layer. That is, the present invention is as follows.
(1) A shielded device for welded part of an ERW steel pipe that gas shields a welded part at the time of ERW welding with a shielding gas made of an inert gas, from the upper end of the welded part to the welded part A shield gas blowing nozzle in which a gas discharge port divided into three layers with respect to the circumferential direction of the raw tube is arranged at a position above 5 to 300 mm, and a flow rate of the shield gas discharged from the gas discharge port, The gas discharge flow rate B from the gas discharge port of the central layer of the three layers 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 is an equation: And a gas flow regulator for controlling the flow rate to satisfy 0.01 ≦ B / A ≦ 10.
(2) The core welded part shielding device for an electric resistance welded steel pipe according to (1), wherein the central layer is further divided into two or more layers in the circumferential direction of the core.
(3) The combined shape of all the layers of the gas discharge port is a rectangular shape having a length of 30 mm or more as a component in the pipe passage direction of the dimension and a width of 5 mm or more as a component of the element tube edge butting direction as a dimension. (1) or (2) characterized in that the welded part shielding device for the welded part of the ERW steel pipe.
(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 raw material welded part shielding device for an electric resistance welded steel pipe according to any one of (1) to (3), wherein the relationship is satisfied.
(5) The ERW 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. Welded part shield device.
(6) A method for shielding a welded portion of an ERW steel pipe which is gas shielded with a shielding gas composed of an inert gas during ERW welding, wherein the welded portion is shielded from the upper end of the welded portion with respect to the welded portion. The shield gas from the gas discharge port of the nozzle for spraying a shield gas in which gas discharge ports divided into three layers with respect to the circumferential direction of the raw tube are arranged at a position 5 to 300 mm above, of the three layers The gas discharge flow rate B from the gas discharge port of the central layer is set 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 is an equation, 0.01 ≦ B / A ≦ 10. A method for shielding a welded portion of a base pipe weld of an electric resistance welded steel pipe, characterized by spraying at a flow rate satisfying 10.
(7) The method for shielding a welded portion of an ERW steel pipe according to (6), wherein the central layer is further divided into two or more layers in the circumferential direction of the pipe.
(8) The combined shape of all the layers of the gas discharge port is a rectangular shape having a length of 30 mm or more as a component in the pipe passage direction of a dimension and a width of 5 mm or more as a component of a dimension of a raw pipe edge. (6) or (7) characterized in that the welded portion shielding method for the welded portion of the ERW steel pipe.
(9) 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 shielding a welded portion of an unsealed steel pipe according to any one of (6) to (8), wherein the relationship is 1.0.
(10) The ERW steel pipe according to any one of (6) to (9), wherein the gas contains 0.1% by mass or more of a reducing gas instead of the inert gas. Welding part shielding method.
(11) In the method of manufacturing an electric resistance welded steel pipe which is welded by electric resistance welding while gas shielding the welded portion, the gas shield is a base pipe cover of the electric resistance welded steel pipe according to any one of (6) to (10). A method for producing an ERW steel pipe, characterized in that the method is performed by a welding part shielding method.
(12) An ERW steel pipe manufactured by the manufacturing method of (11).
(13) An electric resistance welded steel pipe having a welded portion by electric resistance welding, wherein an oxide area ratio of the welded portion is less than 0.1%.

  According to the present invention, the oxygen concentration of the welded part during ERW welding can be maintained at a sufficiently low level, and the welded part characteristics of the ERW steel pipe can be reliably improved from the conventional level.

It is the schematic which shows the example of embodiment of this invention. It is a three-dimensional 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 of shield gas, and gas flow rate ratio B / A. It is a diagram which shows the example of 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 edge butt | matching part).

  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 tube 10 to the ERW steel tube 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 arranged by arranging its gas discharge port 1 </ b> A 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. Furthermore, the center 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. 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 resistance of the electric 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, 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 / It 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 sufficiently reach the welded part 11 and the oxygen concentration of the welded part 11 does not become 100 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 provided.

  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 velocities B for the plurality of layers are not necessarily the same value, and are within the appropriate range. As long as it is, 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 in 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, and a sufficient gas shield can be achieved (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 the diagram which put together 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. 1C, the width of the raw material edge butt direction component of the combined size of the gas discharge ports 1A is denoted as R, and the end surface of the welded portion 11 immediately 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 a gas containing 0.1 mass% or more of reducing gas, the composition which consists only of reducing gas, or the composition which contains reducing gas: 0.1 mass% or more and the remainder consists of an inert gas. Those are preferred.

Further, from the viewpoint of easy availability and low cost, it is preferable to use the following gas as the shielding gas.
(B) When using inert gas alone: (G1) Any one of nitrogen gas, helium gas and argon gas, or a mixture of two or more of these
(B) When using reducing gas alone: (G2) One of hydrogen gas and carbon monoxide gas or a mixture of these two
(C) When using a mixed gas of inert gas and reducing gas: Mixed gas of the above (G1) and (G2) In particular, if a gas containing hydrogen gas and / or carbon monoxide gas is used, it is left out Needless to say, safety measures should be taken.

  The steel strip is passed through a pipe making facility composed of an uncoiler, leveler, roll forming machine, electric seam welder, and sizer in this order, and a low carbon with an outer diameter of 600 mm and a wall thickness of 20.6 mm. In the process of manufacturing the low-alloy steel electric resistance welded pipe, the gas spraying condition level is expressed within or 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. As shown in FIG. 1, the measurement was performed with various changes, and the oxygen concentration of the welded part and the oxide area ratio of the welded part were measured. Here, the nozzle 1 having the form shown in FIG. 1B was used. The groove shape was an I-shaped groove shape. The results are shown in Table 1.

  As shown in Tables 1 and 2, in the examples of the present invention, the oxygen concentration in the welded portion was remarkably reduced as compared with the comparative example, and the oxide area ratio in the welded portion was significantly reduced.

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 (11)

  An apparatus for shielding welded parts of an electric resistance welded steel pipe which shields a welded part at the time of ERW welding with a shielding gas made of an inert gas, and is 5 to 300 mm from the upper end of the welded part with respect to the welded part. A shield gas spray nozzle in which gas discharge ports divided into three layers with respect to the circumferential direction of the raw tube are arranged at an upper position, and the flow rate of the shield gas discharged from the gas discharge port are set to the three layers. The gas discharge flow rate B from the gas discharge port of the central layer 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 is 0.01. A gas flow regulator that controls the flow rate to satisfy ≦ B / A ≦ 10.   The base welded portion shielding device for an electric resistance welded steel pipe according to claim 1, wherein the central layer is further divided into two or more layers in the circumferential direction of the base pipe.   The combined shape of all the layers of the gas discharge port is a rectangular shape having a length of 30 mm or more as a component in the direction of passing through the dimension and a width of 5 mm or more as a component in the element tube edge butting direction as a dimension. The device for shielding a welded portion of an unsealed steel pipe according to claim 1 or 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 raw material welded portion shielding device for an electric resistance welded steel pipe according to any one of claims 1 to 3, wherein the following relationship is satisfied.   The welded portion shielding device for an ERW steel pipe according to any one of claims 1 to 4, wherein the gas contains 0.1% by mass or more of a reducing gas instead of the inert gas. .   A method for shielding a welded portion of an ERW steel pipe by gas shielding the welded portion at the time of ERW welding with a shielding gas composed of an inert gas, wherein the welded portion is 5 to 300 mm from the upper end of the welded portion with respect to the welded portion. 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 the upper position, and the central layer of the three layers. The gas discharge flow rate B from the gas discharge port is set 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 is expressed by the formula: 0.01 ≦ B / A ≦ 10. A method for shielding a welded portion of a welded part of an ERW steel pipe, characterized by spraying as a flow rate to satisfy.   The said center layer is further divided | segmented into two or more layers with respect to the pipe | tube peripheral direction, The pipe | tube weld part shielding method of the electric-resistance-welded steel pipe of Claim 6 characterized by the above-mentioned.   The combined shape of all the layers of the gas discharge port is a rectangular shape having a length of 30 mm or more as a component in the direction of passing through the dimension and a width of 5 mm or more as a component in the element tube edge butting direction as a dimension. The method for shielding a welded portion of an unsealed steel pipe according to claim 6 or 7.   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 for shielding a welded portion of an unsealed steel pipe according to any one of claims 6 to 8, wherein the following relationship is satisfied.   10. The method for shielding a welded portion of an ERW steel pipe according to claim 6, wherein the gas contains 0.1% by mass or more of a reducing gas instead of the inert gas. . In the manufacturing method of the electric resistance welded pipe which carries out electric resistance welding while gas-shielding a to-be-welded part, the above-mentioned gas shield is carried out by the shielded part to-be-welded part of an electric resistance welded steel pipe according to any one of claims 6 to 10. method of manufacturing an electric resistance welded steel pipe, which comprises carrying out.

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