Design method of straight seam pre-welding process for JCO forming

Abstract

The invention relates to a straight seam pre-welding process design method for JCO forming. The straight seam pre-welding process design method comprises the steps that pre-welding specification preliminary parameters are set, and a pre-welding penetration theoretical value and a welding wire melting amount theoretical value are calculated; calculating the size of a pre-welding seam according to the pre-welding standard preliminary parameters, the pre-welding penetration theoretical value and the welding wire melting amount theoretical value, wherein the size at least comprises the penetration actual value, the pre-welding excess weld metal and the width of the seam; and performing strength verification on the pre-welding seam, and determining pre-welding standard parameters under the safety condition that the maximum bending moment stress of the pre-welding seam does not exceed the real tensile strength. The invention provides a straight seam pre-welding process design method for JCO forming, which comprises the following steps of: firstly, setting preliminary parameters of pre-welding specifications, and calculating a theoretical value of pre-welding penetration depth and a theoretical value of welding wire melting quantity; calculating the size of a pre-welding seam; and finally, reasonable pre-welding standard parameters meeting safety conditions are determined through strength verification, normal straight seam pipe blank production is met, systematicness and safety are both considered, and the pre-welding quality is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of steel pipe welding and gas shielded welding, and particularly relates to a method for designing a straight seam pre-welding process for JCO forming. Background Art

[0002] The JCO forming process is a forming process for manufacturing large-diameter straight seam submerged arc welded pipes. Among them, the pre-welding process is an important step in the JCO forming process. The previous process is the forming process, that is, the pre-bent steel plate is pressed into a "J" shape and a "C" shape through multiple step-by-step stamping to form an "O" shape pipe blank with a certain opening amount. The pre-welding process uses a large current gas shielded welding to weld the "O" shape pipe blank at the seam to make it a seam pipe blank that meets the specified quality requirements. In the subsequent pre-welding finishing process, the pre-weld seam and the pipe shape are inspected and trimmed to meet the requirements of subsequent internal welding and external welding.

[0003] In the related art, the pre-welding process and specifications are limited to specific steel pipe types or specifications, lack systematicness, and cannot be naturally deduced from one specification to another, making it difficult to ensure the quality and safety of pre-welding. Summary of the Invention

[0004] The technical problem to be solved by this application is that in the related art, the pre-welding process and specifications are limited to specific steel pipe types or specifications, resulting in difficulty in ensuring the quality and safety of pre-welding.

[0005] The embodiments of this application provide a method for designing a straight seam pre-welding process for JCO forming, including the following steps: Set the preliminary parameters of the pre-welding specification, and calculate the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount; Calculate the size of the pre-weld seam according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth, and the theoretical value of the wire melting amount. The size at least includes the actual penetration depth, the pre-weld reinforcement, and the weld width; Perform strength verification on the pre-weld seam, and determine the pre-welding specification parameters with the condition that the maximum bending moment stress of the pre-weld seam does not exceed the true tensile strength as the safety condition.

[0006] In one embodiment, the calculation formula for the theoretical value of the pre-welding penetration depth is: ; The calculation formula for the theoretical value of the wire melting amount is: ; Wherein, I is the pre-welding current, v is the welding speed, L is the wire extension length.

[0007] In one embodiment, the calculation of the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount includes: Obtain the tensile curves of the base metal of each steel grade and the tensile curve of the weld to establish the standard true stress-nominal strain curves of the base metal of the steel grade and the weld; Conduct pre-welding tests on the groove welds, and perform statistical regression analysis on the relationships between different pre-welding specification parameters, pre-welding penetration values, and wire melting amounts to obtain the calculation formulas for the theoretical values of pre-welding penetration and the theoretical values of wire melting amounts; Calculate the theoretical values of pre-welding penetration and wire melting amounts according to the preliminary parameters of the pre-welding specification.

[0008] In one embodiment, the key points include one or more of the elastic limit point, yield strength point, turning midpoint, tensile strength point, and fracture strength point.

[0009] In one embodiment, calculate the dimensions of the pre-welded seam according to the preliminary parameters of the pre-welding specification, the theoretical value of pre-welding penetration, and the theoretical value of wire melting amount. The dimensions at least include the actual penetration value, pre-weld reinforcement, and weld width, including: Calculate the weld cross-sectional area according to the theoretical value of pre-welding melting amount; Determine the weld state and weld width according to the groove width, wire diameter, groove area, and weld cross-sectional area in the preliminary parameters of the pre-welding specification; Calculate the actual penetration value according to the theoretical value of pre-welding penetration and the groove depth corresponding to the weld width; Calculate the pre-weld reinforcement according to the weld cross-sectional area.

[0010] In one embodiment, perform strength verification on the pre-welded seam. With the condition that the maximum bending moment stress of the pre-welded seam does not exceed the true tensile strength as the safety condition, determine the pre-welding specification parameters, including: Set the initial range of the C value after the tube blank opening is formed; Calculate the maximum value of the normal stress of the cross-sectional bending moment of the base metal of the steel grade and the maximum value of the normal stress of the cross-sectional bending moment of the pre-welded seam; Judge whether the pre-welded seam is safe according to whether the above maximum value of the bending moment normal stress is not greater than the true stress of the corresponding key point in the standard true stress-nominal strain curve of the weld; When the above maximum value of the bending moment normal stress does not exceed the true stress of the corresponding key point, judge that the pre-welded seam is safe; Calculate the range of the C value under the safe condition to determine the pre-welding specification parameters.

[0011] In one embodiment, the judgment of whether the pre-welded seam is safe according to whether the above maximum value of the bending moment normal stress is not greater than the true stress of the corresponding key point in the standard true stress-nominal strain curve of the weld further includes: When the maximum value of the normal stress of the pre-weld cross-section bending moment is greater than the true stress of the corresponding key point, a weld bending moment diagram is established according to the standard true stress-nominal strain curve of the weld, and correction verification is carried out.

[0012] In one embodiment, the calculation of the C value range under the safety condition includes: Under the safety condition, calculate the maximum value of the C value according to the yield strength limit of the steel grade base material to which the C value is subject; Determine the C value range according to the maximum value of the C value.

[0013] In one embodiment, when the maximum value of the C value exceeds the set range, reset the pre-welding specification parameters.

[0014] In one embodiment, the pre-welded seam is subjected to strength verification according to different steel grades, so that the pre-welding specification parameters meet the safety conditions.

[0015] The beneficial effects brought by the technical solution provided by the embodiments of the present application include: The present application provides a method for designing a longitudinal seam pre-welding process for JCO forming. First, preliminary parameters of the pre-welding specification are set, and the theoretical values of the pre-welding penetration depth and the theoretical value of the wire melting amount are calculated; then, the size of the pre-welded seam is calculated accordingly; finally, strength verification is carried out. Through the force analysis of the pre-welded pipe blank, the method of moment balance is used to determine the safety conditions for the stress of the pre-welded seam, so as to set reasonable pre-welding specification parameters. A complete set of longitudinal seam pre-welding processes is provided for steel pipes of different types or specifications, meeting the normal production of longitudinal seam pipe blanks, taking into account systematicness and safety, and ensuring pre-welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a flowchart of a method for designing a longitudinal seam pre-welding process for JCO forming according to an embodiment of the present invention.

[0018] Figure 2 It is a pre-welding torch and weld size diagram according to an embodiment of the present invention.

[0019] Figure 3 It is a pre-weld cross-section morphology diagram according to an embodiment of the present invention.

[0020] Figure 4 It is a pre-welding design morphology diagram according to an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of the residual stress of the steel pipe in an embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of the bending moment of the pipe blank in an embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram of the bending moment of the weld cross-section in an embodiment of the present invention. Detailed implementation manners

[0024] In order to enable those skilled in the art of the present technology to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0025] As Figure 1 shown, Figure 1 This is a flowchart of a method for designing a longitudinal submerged arc pre-welding process for JCO forming in an embodiment of the present invention.

[0026] This embodiment provides a method for designing a longitudinal submerged arc pre-welding process for JCO forming, including the following steps: Step S1: Set the preliminary parameters of the pre-welding specification, and calculate the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount; Step S2: Calculate the size of the pre-welding weld according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth, and the theoretical value of the wire melting amount. The size at least includes the actual penetration depth, the pre-welding reinforcement, and the weld width; Step S3: Perform strength verification on the pre-welding weld. Taking the maximum bending moment stress of the pre-welding weld not exceeding the true tensile strength as the safety condition, determine the pre-welding specification parameters.

[0027] This embodiment provides a method for designing a longitudinal submerged arc pre-welding process for JCO forming. First, set the preliminary parameters of the pre-welding specification, and calculate the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount; then calculate the size of the pre-welding weld accordingly; finally, perform strength verification. Through the force analysis of the pre-welded pipe blank, using the method of moment balance, determine the safety condition for the stress of the pre-welding weld, so as to set reasonable pre-welding specification parameters. A complete set of longitudinal submerged arc pre-welding processes is provided for steel pipes of different types or specifications, meeting the normal production of longitudinal seam pipe blanks, taking into account systematicness and safety, and ensuring the pre-welding quality.

[0028] The following will elaborate on each step in detail.

[0029] In step S1, when setting the pre-welding specification parameters in step S11, the pre-welding specification parameters include a series of process parameters and technical requirements adopted during the pre-welding process. These parameters and requirements directly affect the welding quality, efficiency, and performance of the welded joint. Such as welding current, welding voltage, welding speed, wire diameter, wire extension length, shielding gas, groove form, etc.

[0030] In one embodiment, the calculation formula for the theoretical value of pre-welding penetration depth is: ; The calculation formula for the theoretical value of wire melting amount is: ; Wherein, I is the pre-welding current, v is the welding speed, L is the wire extension length.

[0031] Through the above scheme, the calculation formulas for the theoretical value of pre-welding penetration depth and the theoretical value of wire melting amount are provided, providing a data basis for subsequent adjustment of the preliminary pre-welding specification parameters and calculation of the weld size.

[0032] In one embodiment, in step S1, in step S12, calculating the theoretical value of pre-welding penetration depth and the theoretical value of wire melting amount includes: Step S121, obtaining the tensile curves of base metals of each steel grade and the tensile curve of the weld to establish the standard true stress-nominal strain curves of base metals of each steel grade and the weld.

[0033] Specifically, for example, collecting the tensile curves of base metals of each pipeline steel grade that meet the API SPEC 5L standard and the tensile curve of the weld that meets the straight-seam pre-welding from the test curves of the universal testing machine, which include multiple key points.

[0034] Among them, the typical steel grades range from L245 - L625, and the wire meets the national standard GB / T8110-2020 "Solid Wires for Gas Shielded Metal Arc Welding of Non-Alloy and Fine Grain Steels". In this embodiment, the wire grades for the pre-welding process include ER50 and ER55 grades. The base metal corresponding to the ER50 grade wire is BM-X65 (L245 - L450), and the base metal corresponding to the ER55 grade wire is X70 - X80 (L485 - L555). The above steel grades meet the API SPEC 5L standard.

[0035] In one embodiment, the key points include one or more of the elastic limit point, yield strength point, turning midpoint, tensile strength point, and fracture strength point. For example, the elastic limit point is set to 90% of the yield strength point, the turning midpoint is set to the median or coefficient of the yield strength point and the tensile strength point, and the fracture strength point maintains a fixed ratio with the tensile strength point. The continuous tensile curve with elastic stage, yield stage, strengthening stage, and local necking stage is simplified into a plurality of formulaic line segments. Selecting the elastic limit point, yield strength point, approximate yield end point or midpoint of the line segment, tensile strength point, and fracture point as the above key points not only facilitates simplified calculation but also meets the design requirements.

[0036] Taking the tensile curve of the steel plate base material collected as an example, select the nominal strain ε of the above 5 key points from the actual tensile curve of the steel plate base material, and the nominal stress σ is selected from the theoretical values of the API SPEC 5L standard to calculate the true strain ε Z and the true stress σ Z , and the calculation formula is: , so as to obtain the standard true stress-nominal strain curve of the steel plate base material.

[0037] Step S122: Conduct a pre-welding test on the groove weld, and perform a statistical regression analysis on the relationship between different pre-welding specification parameters, pre-welding penetration values, and wire melting amounts to obtain the calculation formulas for the theoretical values of pre-welding penetration and the theoretical values of wire melting amounts.

[0038] Specifically, conducting a pre-welding test on the groove weld includes: welding the steel plate with a groove using the pre-welding process, performing a tensile strength test on the weld specimen to obtain the tensile strength of the base material and the tensile strength of the weld; conducting a deposited metal rod sample test to determine the strength difference and elongation of different welding consumables (ER50 and ER55 grade welding wires); conducting a surfacing test to accurately measure the melting amount of the welding wire. Through specific groove welding, simulating the on-site welding conditions, setting various pre-welding specification parameters, and measuring the weld morphology, perform a statistical regression analysis on the relationship between different pre-welding specification parameters, pre-welding penetration values, and wire melting amounts to obtain the calculation formulas for the theoretical values of pre-welding penetration and the theoretical values of wire melting amounts.

[0039] Step S123: Calculate the theoretical values of pre-welding penetration and the theoretical values of wire melting amounts according to the preliminary parameters of the pre-welding specification.

[0040] Through the above solution, the tensile curves of the base metals of each pipeline steel grade and the tensile curves of the welds are collected, and theoretical analysis is carried out to establish the standard true stress-nominal strain curves of the base metals and the welds of the steel grades. Then, combined with the pre-welding test, statistical regression analysis is carried out to obtain the reasonable theoretical value calculation formulas for the pre-welding penetration depth and the theoretical value calculation formula for the wire melting amount within the effective range. According to the trial production and test of the longitudinal submerged arc welding, the forming theoretical law of the pre-welding is obtained to guide the actual weld forming, which is convenient for guiding the welding of steel pipes with different wall thicknesses and also convenient for the forming control of the subsequent external welds.

[0041] In one embodiment, in step S2, the dimensions of the pre-welded joint are calculated according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth, and the theoretical value of the wire melting amount. The dimensions at least include the actual penetration depth, the pre-welded reinforcement, and the weld width, including: In step S21, the cross-sectional area of the weld is calculated according to the theoretical value of the pre-welding melting amount. In step S22, the weld state and the weld width are determined according to the groove width, the wire diameter, the groove area, and the cross-sectional area of the weld in the preliminary parameters of the pre-welding specification. In step S23, the actual penetration depth is calculated according to the theoretical value of the pre-welding penetration depth and the groove depth corresponding to the weld width. In step S24, the pre-welded reinforcement is calculated according to the cross-sectional area of the weld.

[0042] Specifically, a specific steel pipe specification is provided, including the outer diameter D , wall thickness t , and material, so as to prepare the standard milling groove parameters, including the root face P , angle a , and the outer weld height P2. The preliminary parameters of the pre-welding specification include the welding speed v , current I , voltage U , the wire extension length L range, etc. For detailed content, please refer to the embodiments below.

[0043] Through the above solution, by setting the specific preliminary parameters of the pre-welding specification, the penetration depth and the shape of the reinforcement of the pre-welded joint are analyzed, and design verification is carried out.

[0044] In one embodiment, in step S3, the strength of the pre-welded joint is checked. Taking the maximum bending moment stress of the pre-welded joint not exceeding the true tensile strength as the safety condition, the pre-welding specification parameters are determined, including: In step S31, the initial range of the C value after the tube blank opening is formed is set. In step S32, the maximum value of the bending moment normal stress of the tube blank base metal section and the maximum value of the bending moment normal stress of the pre-welded joint section are calculated. In step S33, it is judged whether the pre-welded joint is safe according to whether the maximum value of the above weld bending moment normal stress is not greater than the true stress at the corresponding key point in the standard true stress-nominal strain curve of the weld. When the maximum value of the normal stress of the weld bending moment does not exceed the true stress of the corresponding key point, it is determined that the pre-welded seam is safe; In one embodiment, step S33, determining whether the pre-welded seam is safe according to whether the maximum value of the normal stress of the weld bending moment is not greater than the true stress of the corresponding key point in the standard true stress-nominal strain curve of the weld further includes: When the maximum value of the normal stress of the cross-section bending moment of the pre-welded seam is greater than the true stress of the corresponding key point, a weld bending moment diagram is established according to the standard true stress-nominal strain curve of the weld for correction verification.

[0045] Through the above solution, according to the known tube blank information and pre-welding process, the safety of the weld is analyzed by bending moment, and the reasonable range of the formed opening C value is determined.

[0046] Furthermore, when the residual stress on the weld surface exceeds its yield strength, stress calculation is relatively difficult, and it is converted to that the maximum weld bending moment is not less than the residual bending moment of the base material. That is, the following formula is comprehensively used for strength verification: σ Bx ≤σ b Or the maximum bending moment M4 generated by the tensile strength point ≥ the base material bending moment MA.

[0047] Step S34, calculating the range of C value under safe conditions to determine the pre-welding specification parameters.

[0048] Through the above solution, after JCO forming, the opening of the tube blank and the analysis of the weld penetration and strength brought by the pre-welding process are carried out to ensure the safety of the pre-welding process. Combining historical actual data, shape design and strength verification are carried out. The research on the straight-seam pre-welding moment balance method makes the relationship between the formed opening and the pre-welding force clearer, and can be analyzed more accurately according to the actual tensile curve. That is, through moment balance operation, the process design under limit conditions meets the quality and safety requirements, and lays a good foundation for the subsequent internal welding and external welding designs.

[0049] In one embodiment, step S34, calculating the range of C value under safe conditions includes: Under safe conditions, according to the fact that the C value is limited by the yield strength of the steel grade base material, calculate the maximum value of the C value; Determine the range of the C value according to the maximum value of the C value.

[0050] In one embodiment, when the maximum value of the C value exceeds the set range, reset the pre-welding specification parameters.

[0051] Through the above solution, the limit formed opening is studied, and process adjustment is carried out under a larger opening to realize a new weld form, and a new welding process is optimized to meet the strength requirements.

[0052] In one embodiment, the strength of the pre-weld seam is checked according to different steel grades, so that the pre-weld specification parameters meet the safety conditions.

[0053] Through the above solution, the strength of the pre-weld seam is checked according to different steel grades, which not only ensures that the thin-walled base material with low yield strength meets the safety conditions, but also guarantees the safety of the thick-walled base material with high yield strength.

[0054] Through the method provided by the embodiments of the present application, the process parameter range for the straight-seam pre-welding of JCO forming is as follows: after JCO forming, pre-welding is carried out at the 12 o'clock position of the clock. Gas shielded welding is used, and the mixed gas is Ar:CO2 = 4:1, with a flow rate of 50 - 150 L / min. The welding current range is 450A - 900A, the voltage is 20V - 26V, the welding speed is 2.0 - 4.0 m / min, and the wire extension length range is 8 - 35 mm. The welding wire is solid wire, with a diameter range of 2.4 - 4.0 mm. The steel is pipeline steel, and the material is pipeline steel conforming to API SPEC 5L B-X80 (i.e., L245 - L555 material, which also conforms to the national standard GB / T9711-2023), with a wall thickness range of 7 - 33 mm. Using this design method not only improves the control accuracy of the pre-welding process, but also conveniently optimizes the process for the exceeded opening, which is of great help to the welding automation of the pre-welding process.

[0055] Specific embodiments are provided below for elaboration.

[0056] Embodiment 1: As Figures 2 to 4 shown, where Figure 2 is the pre-welding torch and weld size diagram in an embodiment of the present invention. Figure 3 is the pre-welding cross-sectional morphology diagram in an embodiment of the present invention. Figure 4 is the pre-welding design morphology diagram in an embodiment of the present invention.

[0057] Taking the L245M φ508mm×7.1mm submerged arc welded steel pipe for straight seam as an example.

[0058] Step S1: Set the preliminary parameters of the pre-welding specification, and calculate the theoretical value of the pre-welding penetration depth and the theoretical value of the welding wire melting amount.

[0059] As Figure 2 shown, according to the general straight-seam edge milling parameter settings, the groove dimensions are: root face P = 4mm, outside groove height P2 = 1mm, groove angle a = 55°, groove width b = 2.9mm, the depth P4 after pre-welding, and the wall thickness t.

[0060] Set preliminary parameters for pre-welding specifications: Select gas shielded welding wire ER50-G according to the base metal material (complies with American standard AWS A5.18 ER70S-G, GB / T8110 G49A). Mixed gas Ar:CO2 = 4:1, flow rate ~60L / min. Welding speed v = 3.5m / min, current I = 500A, voltage 22V, wire extension length L = 12.16mm, wire diameter d = 2.4mm. The welded weld is named pre-weld 50. Welding torch parameters: shielding sleeve height L1 , wire extension length L = x + L1 + P2 - d / 2 / tana, x = 2mm, x is the depth that the contact tip retracts into the shielding sleeve 。

[0061] Calculate the theoretical value of pre-welding penetration depth and the theoretical value of wire melting amount: ; .

[0062] Step S2: Calculate the size of the pre-welded joint according to the preliminary parameters of the pre-welding specifications, the theoretical value of the pre-welding penetration depth, and the theoretical value of the wire melting amount.

[0063] As Figure 3 shown, the size of the pre-welded joint includes: width b1 , actual penetration depth h1 , pre-weld reinforcement δ , groove depth H , root radius r1 , surface radius r . The length unit is mm, and the angle unit is °.

[0064] Weld cross-sectional area S = G / 7.85 / v = 110.84 / 7.85 / 3.5 = 4.03mm 2 .

[0065] Although the groove width b = 2.9mm > wire diameter d = 2.4mm, the groove area , so the weld is in the surfacing state. Estimate the surface width of the weld (surfacing state).

[0066] Actual penetration depth .

[0067] The weld reinforcement is calculated according to the spherical crown. By adjusting the arc radius r to make the filling area equal to the melting area, at this time rIf = 2.9mm, the formula for the pre-weld reinforcement height is: = 0.90mm; Weld root radius r1 = 1.5 - 2.0mm, please refer to Figure 4 a.

[0068] Step S3: Perform strength verification on the pre-weld seam. Determine the pre-weld specification parameters with the condition that the maximum bending moment stress of the pre-weld seam does not exceed the true tensile strength.

[0069] Set the initial range of the C value after the tube blank opening is formed as C = 90 - 120mm. The minimum opening is restricted by the width of the forming die handle of the JCOE forming process and shall not be less than 90mm.

[0070] Adopt the standard true stress - nominal strain curve of the standard steel plate base material and the mechanical experiment curve of the deposited metal. The data points are shown in Table 1.

[0071] Table 1 Data points of the standard true stress - nominal strain curves of the base material and the weld

[0072] As Figure 5 shown, according to the general circumferential residual stress formula of the steel pipe: 7.46 < 245MPa, it can be obtained that under this material, the opening after pre-welding is C1 = C.

[0073] As Figure 6 、 Figure 7 shown, according to the moment balance MA = MB. ; In the elastic stage of the weld, . Among them, σ A1x represents the maximum bending moment normal stress of the steel grade base material section (A surface); σ B1x represents the maximum bending moment normal stress of the pre-weld seam section (B surface). = 217.46MPa, then calculate: .

[0074] At the same time, its equivalent stress: = 535.12MPa << σbz = 1198MPa.

[0075] Therefore, it is judged that the pre-weld seam is safe from the strength perspective.

[0076] Since the maximum springback moment of the tube blank is determined by the elastic strength, the C value is restricted by the yield strength of the steel grade base material. Therefore, the maximum opening after pre-welding: ≈125 mm. At this time, the corresponding weld stress σ A1x = 691.48 MPa << σbz = 1198 MPa, so it is safe. This indicates that the formed opening C can be larger, but it is preferably below 150 mm for pipe shape control.

[0077] Since the corresponding parameters at this time are (C1max, σ s , t), specifically (125, 245, 7.1). Considering the positive tolerance of the wall thickness, another set of parameters (121, 290, 7.8) can be obtained by re-verifying according to the high steel grade. Overall, the actual formed opening control range is C = 90 - 150 mm.

[0078] According to the above steps, the pre-welding specification parameters are determined as follows: Use ER50-G φ2.4 mm welding wire, mixed gas Ar:CO2 = 4:1, flow rate ~60 L / min. Welding speed 3.5 ± 0.1 m / min, current 500 A ± 20 A, voltage 22 V ± 1 V, wire extension length 12 mm ± 2 mm. Formed opening control: C = 90 - 150 mm.

[0079] Example 2: Take the L555M φ1219 mm × 33 mm longitudinal submerged arc welded steel pipe as an example Step S1: Set the preliminary pre-welding specification parameters and calculate the theoretical pre-welding penetration value and the theoretical wire melting amount.

[0080] According to the ordinary longitudinal edge milling parameters, the groove dimensions are: root face P = 8.5 mm, outside groove height P2 = 13 mm, groove angle a = 30°, groove width b = 15.01 mm, post-pre-welding depth P4, wall thickness t.

[0081] Set the preliminary pre-welding specification parameters: Select the gas shielded welding wire ER55-G (meeting the American standard AWS A5.28 ER90S-G, GB / T8110 G55A) according to the base metal material. Mixed gas Ar:CO2 = 4:1, flow rate ~80 L / min. Welding speed v = 2.5 m / min, current I = 800 A, voltage 24 V, wire extension length L = 30.4 mm, wire diameter d = 3.0 mm. The welded weld is named pre-weld 55. Welding torch parameters: shielding sleeve height L1 , wire extension length L = x + L1 + P2 - d / 2 / tana, x = 2mm, x is the depth that the wire extends into the shielding sleeve from the contact tip 。

[0082] Calculate the theoretical values of the pre-welding penetration depth and the theoretical value of the wire melting amount: h = 4.34 mm, G = 212.37 g / min.

[0083] Step S2: Calculate the size of the pre-welding weld according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth, and the theoretical value of the wire melting amount.

[0084] Weld cross-sectional area S = G / 7.85 / v = 212.37 / 7.85 / 2.5 = 10.84 mm 2 .

[0085] Groove width b = 15.01 mm >> wire diameter d = 3.0 mm; and the groove area , so the weld is in the groove welding state. Estimate the surface width of the weld .

[0086] Determine the groove depth H = 3.65 mm according to the intersection of the weld width and the groove. The actual penetration depth h1 = 5.39 mm.

[0087] The weld reinforcement is calculated according to a circular crown. By adjusting the radius of the arc r to make the filling area equal to the melting area, at this time r = 2.59 mm, then the formula for calculating the pre-welding reinforcement is: = 1.07 mm; Weld root radius r1 = 1.5 - 2.0 mm.

[0088] Step S3: Check the strength of the pre-welding weld. Taking the maximum bending moment stress of the pre-welding weld not exceeding the true tensile strength as the safety condition, determine the pre-welding specification parameters.

[0089] Set the initial range of the C value after the tube blank opening is formed as C = 120 mm.

[0090] Then the maximum value of the bending moment normal stress of the steel grade base metal section is the maximum residual stress of the base metal , which is much smaller than the elastic limit of 501 MPa.

[0092] Then the maximum value of the bending moment normal stress of the pre-welding weld section is the maximum stress of the weld .

[0093] Since the stress exceeds the elastic section, a weld moment diagram is established based on the standard true stress-nominal strain curve of the pre-weld 55 and corrected for verification.

[0094] A moment diagram of M1 - M5 is established according to the weld deformation reaching points 1 - 5 of the tensile curve to specifically determine the range in which the weld stress lies. The weld moment is calculated based on the tensile stress corresponding to the maximum moment M4 generated at the point of maximum nominal strain.

[0095] Base metal moment 。

[0096] The weld moment M4 = 34857.72 N.mm.

[0097] Since M4 > MA, the weld stress is slightly less than the tensile stress, and the weld is safe. The equivalent stress is lower than the weld stress.

[0098] Therefore, it is judged from the strength perspective that the pre-weld is safe.

[0099] Since the maximum opening of the steel grade billet is much larger than the weld strength range and the C value is limited by the weld strength, the allowable maximum opening after pre-welding is:

[0100] = 118.6mm Since the corresponding parameters at this time are ([C1]max, σ s , t )), specifically (118.6, 555, 33). Considering the positive tolerance of the wall thickness, another set of parameters (108.4, 625, 34) is obtained by re-verifying according to the high steel grade. The comprehensive average shows that the actual forming opening control range is C = 90 - 114mm.

[0101] According to the above steps, the pre-welding specification parameters are determined as follows: use ER55 - G φ3.0mm welding wire, mixed gas Ar:CO2 = 4:1, flow rate ~80L / min. Welding speed 2.5 ± 0.1m / min, current 800A ± 20A, voltage 24V ± 1V, wire extension length 30mm ± 2mm. Forming opening control: C = 90 - 114mm.

[0102] Example 3: Take the L555M φ1219mm × 33mm longitudinal submerged arc welded steel pipe as an example When the maximum value of the C value in Example 2 exceeds the set range, the pre-welding specification parameters are reset.

[0103] When the forming opening C = 150 mm, the aforementioned pre-welding specification cannot perform reliable welding and the pre-welding will break. Therefore, the pre-welding specification parameters need to be optimized and adjusted. For example, adjust the current, change the welding speed, add manual gas shielded or electrode welding when necessary to thicken the weld seam, and replace the gas shielded welding wire with a higher steel grade, etc.

[0104] The steel parameters are as follows: the actual wall thickness is 33.8 mm and the actual yield strength is 580 MPa.

[0105] The optimization and adjustment process of the pre-welding specification parameters is as follows: First, consider the moment balance: , indicating that according to the original pre-welding specification parameters, the pre-weld seam will crack.

[0106] Therefore, the original penetration depth h 1 = 5.39 is continuously increased by 0.1 mm to continuously increase the weld seam moment M4 and make the minimum new penetration depth at which M4 ≥ MA h 1 = 6.2 mm.

[0107] At this time, M4 = 46127.45 N·mm > MA. Therefore, the strength of the pre-weld seam meets the safety conditions.

[0108] Then, reset the pre-welding specification parameters: To increase the penetration depth, the current is increased from 800 A to 850 A; since further increase will cause an increase in spatter and a decrease in weld quality, the welding speed is reduced starting from 2.5 m / min to continue increasing the penetration depth. When calculated at a reduction of 0.1 m / min to 2.05 m / min, the weld penetration depth reaches the theoretical requirement.

[0109] The specific calculation is as follows: The theoretical penetration depth .

[0110] Estimate the weld surface width . Determine the groove depth H = 3.79 mm.

[0111] The actual penetration depth .

[0112] The weld seam welded with the above pre-welding specification parameters meets the strength requirements.

[0113] Finally, determine the optimized pre-welding specification parameters: At the parameters (C1, σ s , t) specifically being (150, 580, 33.8), the optimized pre-welding specification parameters are: For pre-welding, use ER55-G φ3.0mm welding wire, with a mixed gas of Ar:CO2 = 4:1 and a flow rate of ~80L / min. The welding speed is 2.05 ± 0.1m / min, the current is 870A ± 20A, the voltage is 24V ± 1V, and the wire extension length is 30mm ± 2mm.

[0114] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present application. Unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0115] It should be noted that in the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0116] In the description of the embodiments of the present application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B; "and / or" in the text is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more than two.

[0117] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A design method for the straight-seam pre-welding process used in JCO forming, characterized in that The steps include: Set the preliminary parameters of the pre-welding specification, and calculate the theoretical values of the pre-welding penetration depth and the theoretical value of the wire melting amount; Calculate the size of the pre-welding weld according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount, and the size at least includes the actual penetration depth value, the pre-welding reinforcement and the weld width; Perform strength verification on the pre-welding weld, and determine the pre-welding specification parameters with the condition that the maximum bending moment stress of the pre-welding weld does not exceed the true tensile strength; 2. The design method of a longitudinal seam pre-welding process for JCO forming according to claim 1, characterized in that The theoretical formula for the pre-welding penetration depth is as follows: ; The theoretical calculation formula for the melting amount of the welding wire is as follows: ; Among them, I is the pre-welding current, v is the welding speed, L is the wire extension length.

3. A method for designing a straight seam pre-welding process for JCO forming according to claim 2, characterized in that, The calculation of the theoretical values of the pre-welding penetration depth and the wire melting amount includes: Obtain the tensile curves of the base metal of each steel grade and the tensile curve of the weld to establish the standard true stress-nominal strain curves of the base metal of the steel grade and the weld; Conduct pre-welding tests on the groove welds, and perform statistical regression analysis on the relationships between different pre-welding specification parameters, pre-welding penetration depth values and wire melting amounts to obtain the calculation formulas for the theoretical values of the pre-welding penetration depth and the theoretical value of the wire melting amount; Calculate the theoretical values of the pre-welding penetration depth and the wire melting amount according to the preliminary parameters of the pre-welding specification; 4. A method for designing a straight seam pre-welding process for JCO forming according to claim 3, characterized in that, The key points include one or more of the elastic limit point, yield strength point, turning midpoint, tensile strength point, and fracture strength point; 5. A method for designing a straight-seam pre-welding process for JCO forming according to claim 1, characterized in that, The calculation of the size of the pre-welding weld according to the preliminary parameters of the pre-welding specification, the theoretical value of the pre-welding penetration depth and the theoretical value of the wire melting amount, and the size at least includes the actual penetration depth value, the pre-welding reinforcement and the weld width includes: Calculate the weld cross-sectional area according to the theoretical value of the pre-welding melting amount; Determine the weld state and weld width according to the groove width, wire diameter, groove area and weld cross-sectional area in the preliminary parameters of the pre-welding specification; Calculate the actual penetration depth value according to the theoretical value of the pre-welding penetration depth and the groove depth corresponding to the weld width; Calculate the pre-welding reinforcement according to the weld cross-sectional area; 6. A method for designing a longitudinal seam pre-welding process for JCO forming according to claim 3, characterized in that, The strength verification of the pre-welding weld, and determining the pre-welding specification parameters with the condition that the maximum bending moment stress of the pre-welding weld does not exceed the true tensile strength includes: Set the initial range of the C value after the tube blank opening is formed; Calculate the maximum value of the normal stress of the cross-sectional bending moment of the base metal of the steel grade and the maximum value of the normal stress of the cross-sectional bending moment of the pre-welding weld; Judge whether the pre-welding weld is safe according to whether the maximum value of the above-mentioned bending moment normal stress is not greater than the true stress of the corresponding key point in the standard true stress-nominal strain curve of the weld; When the maximum value of the above-mentioned bending moment normal stress does not exceed the true stress of the corresponding key point, judge that the pre-welding weld is safe; Calculate the range of the C value under the safe condition and determine the pre-welding specification parameters; 7. A method for designing a straight-seam pre-welding process for JCO forming according to claim 6, characterized in that, The judgment of whether the pre-welding weld is safe according to whether the maximum value of the above-mentioned bending moment normal stress is not greater than the true stress of the corresponding key point in the standard true stress-nominal strain curve of the weld further includes: When the maximum value of the normal stress of the cross-sectional bending moment of the pre-welding weld is greater than the true stress of the corresponding key point, establish a weld bending moment diagram according to the standard true stress-nominal strain curve of the weld and perform correction verification; 8. A method for designing a straight-seam pre-welding process for JCO forming according to claim 6, characterized in that, The calculation of the range of the C value under the safe condition includes: Under the safe condition, calculate the maximum value of the C value according to the limitation of the C value by the yield strength of the base metal of the steel grade; Determine the range of the C value according to the maximum value of the C value.

9. A method for designing a straight seam pre-welding process for JCO forming as described in claim 8, characterized in that, When the maximum value of the C value exceeds the set range, reset the pre-welding specification parameters.

10. A method for designing a straight-seam pre-welding process for JCO forming as claimed in claim 6, characterized in that, Perform strength verification on the pre-welded seam according to different steel grades so that the pre-welding specification parameters meet the safety conditions.

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