Laser welding method of t4003 ferritic stainless steel

Abstract

The application provides a laser welding method of T4003 ferrite stainless steel, which is implemented by a laser welding pipeline manufacturing device comprising a welding wire feeding device, a laser welding device and a post-welding heat treatment device; the laser welding method comprises the following steps: first, debugging is performed to determine parameter values; second, the welding wire diameter and the wire feeding speed are determined according to the weld cross-sectional area and the element composition of the base material, the welding wire and the weld; third, the base material is welded, and the formed weld is subjected to heat treatment. The laser welding method can make the mechanical properties of the weld meet the requirements of load-bearing structure steel pipes and does not reduce the welding efficiency of the welded pipe.

Description

Technical Field

[0001] This invention relates to the technical field of welding methods for ferritic stainless steel, and specifically to a laser welding method for T4003 ferritic stainless steel. Background Technology

[0002] T4003 is a low-chromium ferritic stainless steel. The weld seam after traditional welded pipeline construction is predominantly ferrite with a small amount of grain boundary martensite (e.g., ...). Figure 2 As shown in the figure, it has poor plasticity and toughness, and can currently only be used in non-load-bearing structures, such as coal idlers.

[0003] Traditional methods for welding steel pipes include argon arc welding, plasma welding, laser welding, and high-frequency induction welding, all of which are self-fusion welding methods without filler material. For T4003 ferritic stainless steel, the weld seams produced by argon arc welding, plasma welding, and laser welding consist of coarse ferrite with a small amount of martensite at grain boundaries, resulting in poor ductility and toughness. High-frequency induction welding of T4003 ferritic stainless steel produces a weld seam with a finer ferrite structure than the base metal, resulting in excellent mechanical properties. However, high-frequency induction welding requires high consistency in the properties of the base metal; fluctuations in the properties of the base metal between batches can cause serious welding defects such as incomplete penetration. Furthermore, the welding speed of high-frequency induction welding is very high, generally around 20 m / min, leading to a large amount of waste during the commissioning process and a low yield of welded pipes. Moreover, high-frequency induction welding equipment is expensive. All these factors limit the application of high-frequency induction welding.

[0004] Laser welding is the most feasible method to obtain welded joints that meet the mechanical performance requirements of steel pipes used in load-bearing structures. This is because laser welding has concentrated energy, a very small heat-affected zone, and the microstructure of the weld can be controlled by altering its composition and subsequent treatments.

[0005] There are many existing technologies for laser welding, including laser filler wire welding. However, for low-chromium ferritic stainless steel such as T4003, there are no technologies for laser filler wire welding and weld microstructure control that can meet the mechanical performance requirements of welded pipes for load-bearing structures. Summary of the Invention

[0006] To address the problem of poor ductility and toughness in the weld seam of T4003 welded pipe, this invention provides a laser welding method for T4003 ferritic stainless steel, which enables the mechanical properties of the weld seam to meet the requirements of steel pipes for load-bearing structures without reducing the welding efficiency of the welded pipe.

[0007] Specifically, the present invention is achieved through the following technical solution:

[0008] A laser welding method for T4003 ferritic stainless steel, wherein the laser welding method is implemented using a laser welding pipeline comprising a wire feeding device, a laser welding device, and a post-weld heat treatment device; the laser welding method includes the following steps:

[0009] The first step is to perform debugging and determine the parameter values;

[0010] The second step is to determine the wire diameter and wire feeding speed based on the cross-sectional area of ​​the weld and the elemental composition of the base material, welding wire, and weld.

[0011] The third step is to weld the base material and then heat-treat the resulting weld.

[0012] Optionally, the laser welding pipeline setup includes: positioning the laser beam, welding wire, and shielding gas nozzle on the same plane, perpendicular to the base material to be welded and intersecting the center line of the weld bevel; the forward tilt angle of the laser beam is 5°–10°, and the defocusing amount ranges from -5 to 0 mm; the angle between the welding wire and the base material is 45°–70°, and the welding wire fills the laser spot in the molten pool; the shielding gas nozzle is located behind the laser beam, at an angle of 45°–70° to the base material, and 30–50 mm away from the molten pool.

[0013] Optionally, in the first step, the parameter values ​​are determined as follows: laser power of 1kW to 1.5kW per millimeter of thickness, welding speed of 1.5m / min to 2.5m / min, welding bevel of 0mm and extrusion through forming rollers.

[0014] Optionally, the nickel content of the base material is 0.5%, and the nickel content of the weld is ≥2%.

[0015] The elemental composition of the welding wire is: C≤0.02%, Si≤0.5%, 1.0%≤Mn≤2.0%, P≤0.025%, S≤0.020%, 19.5%≤Cr≤20.5%, 9%≤Ni≤10%, with the balance being Fe and unavoidable impurity elements.

[0016] Optionally, the second step includes:

[0017] (1) Calculate the weld cross-sectional area according to formula (a) based on the weld width on the front and back sides:

[0018]

[0019] in:

[0020] S1 is the cross-sectional area of ​​the weld, in mm. 2 ;

[0021] D1 is the weld width on the front side, in mm;

[0022] D2 is the weld width on the back side, in mm;

[0023] t is the thickness of the base material, in mm;

[0024] (2) Calculate the amount of filler wire:

[0025] The nickel content of the weld is determined according to formula (b), and the filler wire amount per unit weld length is determined according to formula (c).

[0026]

[0027]

[0028] in:

[0029] S2 is the amount of filler wire per unit weld length;

[0030] d is the diameter of the welding wire, in mm;

[0031] v 丝 It is the wire feeding speed, in m / min;

[0032] v 焊 This refers to the welding speed, measured in m / min.

[0033] (3) Determine the range of welding wire diameter d according to formulas (b) and (c), and select the welding wire diameter;

[0034] (4) Determine the wire feeding speed v according to formulas (b) and (c). 丝 The range.

[0035] Optionally, in step (3), the range of the welding wire diameter d is calculated according to formula (d):

[0036]

[0037] The available welding wire diameters include: 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.4mm, and 1.6mm.

[0038] Then, according to formula (d) according to v 丝 =v 焊 If the calculation yields d ≥ d1, and this range includes the specified welding wire diameter, then the diameter value closest to d1 is selected as the welding wire diameter. If this range does not include the specified welding wire diameter, then, according to formula (d), based on v... 丝 =0.8v 焊 The calculation yields d ≥ d², according to v 丝 =1.2v 焊 The calculation shows that d ≥ d3, and the diameter value of the welding wire between d2 and d3 is taken as the welding wire diameter.

[0039] Optionally, in step (4), the wire feed speed v is determined according to formula (e) and the selected welding wire diameter. 丝 Scope:

[0040]

[0041] Then, the final wire feeding speed is selected as a value close to the lower limit of the range.

[0042] Optionally, in the third step, the heat treatment temperature is 400–500°C.

[0043] As can be seen from the above technical solution, the laser welding method for T4003 ferritic stainless steel of the present invention has at least the following beneficial effects:

[0044] The present invention improves the welding device so that the welding method of the present invention can be matched with existing production lines as much as possible, thereby avoiding the cost increase that may be caused by adopting new processes.

[0045] This invention employs a laser-assisted wire-filler welding method. By altering the welding wire material, wire feed speed, welding speed, welding wire insertion position and angle, and post-weld heat treatment, the weld microstructure is controlled. This transforms the traditional T4003 ferritic stainless steel weld microstructure, which is dominated by coarse ferrite with a small amount of martensite at grain boundaries, into a microstructure dominated by tempered martensite with a small amount of ferrite. This significantly improves the mechanical properties of the weld, enabling it to meet the requirements for load-bearing structural steel pipes, namely, the weld does not crack when flattened, and the weld does not crack when the pipe expands 1.3 times, while simultaneously maintaining the welding efficiency of the pipe. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the laser welding pipeline layout and welding process of the present invention; wherein, the direction of the arrow indicates the movement direction of the base material, and the direction pointed to by the arrow indicates the rear part of the laser welding pipeline of the present invention; 1 represents the wire feeding device, 2 represents the laser beam, 3 represents the protective gas nozzle, 4 represents the online heat treatment device, α represents the angle between the welding wire and the base material, β represents the forward tilt angle of the laser beam, and γ represents the angle between the protective gas nozzle and the base material.

[0047] Figure 2 The image shows the weld structure of T4003 ferritic stainless steel formed by conventional laser welding.

[0048] Figure 3 The image shows the weld structure formed by the laser welding method of Embodiment 1 of the present invention. Detailed Implementation

[0049] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0050] To address the problem of poor ductility and toughness in welds of T4003 ferritic stainless steel with a thickness of 2 mm or more, the inventors of this invention conducted in-depth research and creatively proposed a laser welding method for T4003 ferritic stainless steel.

[0051] The technical concept of this invention is to use laser filler wire welding to control the weld microstructure by adjusting parameters such as wire composition, wire feeding speed, welding speed, and post-weld heat treatment. This results in a tempered martensite / ferrite duplex microstructure with excellent mechanical properties, which meets the mechanical performance requirements of welded pipes for load-bearing structures, without reducing the welding efficiency of the welded pipes.

[0052] The laser welding pipeline fabrication method used in this invention is achieved by modifying existing laser welding pipeline fabrication methods. Specifically, refer to... Figure 1 To address this issue, a wire feeding device is added to the existing laser welding pipeline fabrication line, positioned in front of the laser beam. The positional relationship between the laser beam and the shielding gas nozzle is altered so that the laser beam, welding wire, and shielding gas nozzle are all on the same plane, perpendicular to the base material and intersecting the centerline of the weld bevel. The laser beam's forward tilt angle is 5°–10°, and the defocusing distance ranges from -5° to 0mm. The angle between the welding wire and the base material is 45°–70°, and the welding wire fills the laser spot in the molten pool. The shielding gas nozzle is positioned behind the laser beam, at an angle of 45°–70° to the base material, and 30–50mm from the molten pool. An online heat treatment device is added to the rear of the existing laser welding pipeline fabrication line to heat the weld. The distance between the online heat treatment device and the laser welding molten pool is more than 1 meter, and induction heating or flame heating can be used. Specific configurations of the existing laser welding pipeline fabrication line can be found in relevant existing technologies and will not be elaborated upon here. By modifying existing laser welding pipelines and setting equipment parameters, the welding method of this invention can be matched with existing production lines as much as possible, ensuring smooth welding. This not only improves welding quality and ensures welding efficiency, but also avoids the cost increase that may be caused by adopting new processes.

[0053] The laser welding method for T4003 ferritic stainless steel of the present invention includes the following steps:

[0054] The first step is to perform debugging and determine the parameter values.

[0055] Before formal welding, a test weld without filler wire is performed to adjust the laser power and welding speed, ensuring good weld formation. The welding speed should not be lower than the normal production speed of laser-welded tubes, and the laser power should be matched with the welding speed. Furthermore, the weld width on both the front and back sides is measured.

[0056] In one specific implementation, after a trial weld without filler wire, the laser power is set to 1kW to 1.5kW per millimeter of plate thickness, the welding speed is 1.5m / min to 2.5m / min, the weld bevel is 0mm, and the plate is extruded through a forming roller conveyor.

[0057] The second step is to determine the wire diameter and wire feeding speed based on the cross-sectional area of ​​the weld and the elemental composition of the base material, welding wire, and weld.

[0058] In this invention, the wire feeding speed needs to be matched with the welding speed. Specifically, the wire feeding speed is controlled to be 0.8 to 1.2 times the welding speed.

[0059] In this invention, when considering the influence of the elemental composition of the base metal, welding wire, and weld on the welding wire diameter and wire feed speed, the main consideration is the nickel content of the base metal, welding wire, and weld. Specifically, the laser welding method of this invention is for T4003 ferritic stainless steel, which has a nominal nickel content of 0.5%. Based on the inventors' research, in order to refine the weld grains, improve the weld microstructure, and enhance the weld toughness, it is desirable to obtain a martensitic microstructure of more than 50% in the weld. According to Delonte's prediction, the nickel content of the weld needs to be above 2% to achieve the required weld microstructure.

[0060] In one specific embodiment, the elemental composition (wt%) of the welding wire used in this invention is as follows: C≤0.02%, Si≤0.5%, 1.0%≤Mn≤2.0%, P≤0.025%, S≤0.020%, 19.5%≤Cr≤20.5%, 9%≤Ni≤10%, with the balance being Fe and unavoidable impurity elements. The use of the aforementioned elemental composition of the welding wire is primarily based on the following considerations:

[0061] (1) Because T4003 is a low-carbon ferritic stainless steel, if the carbon content of the weld increases, intergranular corrosion and brittleness will occur. Therefore, the carbon content of the welding wire is required to be below 0.02%.

[0062] (2) Since the weld composition is a mixture of base metal T4003 and welding wire, considering that the nickel content after mixing needs to reach more than 2%, and the weld reinforcement limits the amount of filler wire, the nickel content of the welding wire is controlled at 9% to 10%.

[0063] (3) Considering that the corrosion resistance of the weld should not be lower than that of the base metal T4003, and the need for reliable welding wire production, the chromium content of the welding wire is controlled at 19.5% to 20.5%.

[0064] (4) Considering the need for welding wire production costs, the silicon content and manganese content are controlled within the ranges above.

[0065] Specifically, the methods for determining the welding wire diameter and wire feed speed are as follows:

[0066] (1) Calculate the weld cross-sectional area according to formula (a) based on the weld width on the front and back sides:

[0067]

[0068] in:

[0069] S1 is the cross-sectional area of ​​the weld, in mm. 2 ;

[0070] D1 is the weld width on the front side, in mm;

[0071] D2 is the weld width on the back side, in mm;

[0072] t is the thickness of the base material, in mm.

[0073] (2) Calculate the amount of filler wire.

[0074] The nominal nickel content of T4003 ferritic stainless steel is 0.5%, and the lower limit of nickel content in welding wire is 9%. However, the nickel content of the weld in this invention should not be less than 2%. Therefore:

[0075]

[0076] S2 is the amount of filler wire per unit weld length (mm), specifically:

[0077]

[0078] in:

[0079] d is the diameter of the welding wire, in mm;

[0080] v 丝 It is the wire feeding speed, in m / min;

[0081] v 焊 This refers to the welding speed, measured in m / min.

[0082] (3) Determine the diameter of the welding wire.

[0083] The equipment used to manufacture the welding wire is conventional equipment, and the diameter specifications of the obtained welding wire include: 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.4mm, and 1.6mm. In this invention, the range of welding wire diameter d is determined according to formulas (b) and (c), and then the diameter of the welding wire to be used is determined in combination with the aforementioned diameter specifications.

[0084] Specifically, firstly, based on formulas (b) and (c), the range of the welding wire diameter d is determined as follows:

[0085]

[0086] Then, according to formula (d), according to v 丝 =v 焊 If the calculated value is d ≥ d1, and this range includes the aforementioned wire diameter specifications, then the diameter value closest to d1 is selected as the wire diameter. If this range does not include the aforementioned wire diameter specifications, then, according to formula (d), based on v... 丝 =0.8v 焊 The calculation yields d ≥ d², according to v 丝 =1.2v 焊 The calculation shows that d ≥ d3. The diameter value between d2 and d3 of the above-mentioned welding wire diameter specifications is taken as the welding wire diameter. If no welding wire diameter meets the requirements, the nickel content in the welding wire is increased.

[0087] (4) Determine the wire feeding speed.

[0088] First, determine the wire feeding speed v according to formulas (b) and (c). 丝 The range. Specifically, the wire feeding speed v is determined by deriving formulas (b) and (c). 丝 The scope is as follows:

[0089]

[0090] Then, according to formula (e), substitute the welding wire diameter selected in the previous step to calculate v. 丝 The range will be determined by selecting a wire feeding speed that is close to the lower limit of that range, specifically rounded up to one decimal place. For example, when the calculated value is v... 丝 When ≥1.88, v 丝 =1.9, when v is calculated 丝 When ≥1.94, v 丝 =2.

[0091] The third step is to weld the base material and then heat-treat the resulting weld.

[0092] After determining the values ​​of all parameters involved in the welding process, the actual welding begins. Throughout the welding process, 99.999% argon gas is used for protection at a flow rate of 20 L / min.

[0093] The weld is subjected to online heat treatment after welding to transform the martensite structure in the weld into tempered martensite. The temperature range for online heat treatment is 400–500℃.

[0094] Example

[0095] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, are performed according to conventional methods and conditions.

[0096] The elemental composition (wt%) of the welding wire used in the following embodiments is as follows: C≤0.02%, Si≤0.5%, 1.0%≤Mn≤2.0%, P≤0.025%, S≤0.020%, 19.5%≤Cr≤20.5%, 9%≤Ni≤10%, with the balance being Fe and unavoidable impurity elements.

[0097] Example 1

[0098] This embodiment uses 3mm thick T4003 ferritic stainless steel as the test material for welded pipes. The welding gap is 0mm, and it is pressed with a forming roller. Laser wire filler welding is used.

[0099] The parameters for laser welding pipeline fabrication are as follows: laser beam tilt forward 5°, defocusing amount -1mm, angle between welding wire and base material 45°, angle between shielding gas nozzle and base material 50°, and distance between shielding gas nozzle and molten pool 35mm.

[0100] The process in this embodiment is as follows:

[0101] The first step was a trial weld without filler wire. After parameter optimization, a good weld formation was achieved. Specific parameters were: laser output power 3.8kW, welding speed 2m / min, weld bevel gap 0mm, and extrusion via forming rollers. After welding, the welded pipe was cut off, and the width of the weld on the front side was measured to be 2.06mm, and the width of the weld on the back side was 1.36mm.

[0102] The second step is to determine the welding wire diameter and the wire feeding speed.

[0103] First, calculate the weld cross-sectional area according to formula (a): S1 = 5.13 mm. 2 .

[0104] Then, calculate the filler wire amount, determine the range of welding wire diameter based on the filler wire amount, and according to formula (d), follow v 丝 =1.0v 焊 The calculation shows that d ≥ 1.18 mm; therefore, a welding wire with a diameter of 1.2 mm is selected. Further, according to v... 丝 =0.8v 焊 and v 丝 =1.2v 焊 Calculations were performed to verify this, and the results were d≥1.32mm and d≥1.08mm respectively. Since 1.2mm falls between 1.08mm and 1.32mm, the requirement is met.

[0105] Then, according to formula (e), substitute the selected wire diameter of 1.2mm from the previous step to calculate the wire feed speed v. 丝 Range: v 丝If the speed is ≥1.94m / min, select a wire feeding speed of 2m / min.

[0106] The third step is the formal welding. The laser output power is 3.8kW, the welding speed is 2m / min, the laser beam tilt is 5°, and the defocusing amount is -1mm. The weld bevel gap is 0mm, and the weld is extruded via forming rollers. The shielding gas used is 99.999% argon, with a flow rate of 20L / min. The angle between the shielding gas nozzle and the base material is 50°, and the distance between the shielding gas nozzle and the molten pool is 35mm. The welding wire diameter is 1.2mm, the wire feed speed is 2m / min, and the angle between the welding wire and the base material is 45°. The post-weld heat treatment temperature is 420℃.

[0107] The weld metallographic structure obtained in this embodiment is as follows: Figure 3 As shown, the microstructure is a tempered martensite / ferrite duplex structure with approximately 60% tempered martensite. The welded pipe did not crack when flattened at the weld, and the weld did not crack after expanding the pipe 1.3 times its original size.

[0108] Example 2

[0109] This embodiment uses 3.5mm thick T4003 ferritic stainless steel as the test material for welded pipes. The welding gap is 0mm, and it is pressed with a forming roller. Laser filler wire welding is used.

[0110] The parameters for laser welding pipeline fabrication are as follows: laser beam tilt forward 5°, defocusing amount -1.5mm, angle between welding wire and base material 55°, angle between shielding gas nozzle and base material 50°, and distance between shielding gas nozzle and molten pool 40mm.

[0111] The process in this embodiment is as follows:

[0112] The first step was a trial weld without filler wire. After parameter optimization, a good weld formation was achieved. Specific parameters were: laser output power 4.2kW, welding speed 2m / min, weld bevel gap 0mm, and extrusion via forming rollers. After welding, the welded pipe was cut off, and the width of the weld on the front side was measured to be 2.32mm, and the width of the weld on the back side was 1.58mm.

[0113] The second step is to determine the welding wire diameter and the wire feeding speed.

[0114] First, calculate the weld cross-sectional area according to formula (a): S1 = 6.825 mm. 2 .

[0115] Then, calculate the filler wire amount, determine the range of welding wire diameter based on the filler wire amount, and according to formula (d), follow v 丝 =1.0v 焊 The calculation shows that d ≥ 1.36 mm; therefore, a welding wire with a diameter of 1.4 mm is selected. Further, according to v... 丝 =0.8v焊 and v 丝 =1.2v 焊 Calculations were performed to verify this, and the results were d≥1.53mm and d≥1.2mm respectively. Since 1.4mm falls between 1.2mm and 1.53mm, the requirement is met.

[0116] Then, according to formula (e), substitute the selected wire diameter of 1.4mm from the previous step to calculate the wire feed speed v. 丝 Range: v 丝 ≥1.90m / min, select the wire feeding speed as 1.9m / min.

[0117] The third step is the formal welding. The laser output power is 4.2kW, the welding speed is 2m / min, the laser beam tilt is 5°, and the defocusing amount is -1.5mm. The weld bevel gap is 0mm, and the weld is extruded via forming rollers. The shielding gas used is 99.999% argon, with a flow rate of 20L / min. The angle between the shielding gas nozzle and the base material is 50°, and the distance between the shielding gas nozzle and the molten pool is 40mm. The welding wire diameter is 1.4mm, the wire feed speed is 1.9m / min, and the angle between the welding wire and the base material is 55°. The post-weld heat treatment temperature is 450℃.

[0118] The obtained welded pipe did not crack when flattened at the weld seam, and the weld seam did not crack after the pipe was expanded 1.3 times.

[0119] Example 3

[0120] This embodiment uses 5mm thick T4003 ferritic stainless steel as the test material for welded pipes. The welding gap is 0mm, and it is pressed with a forming roller. Laser wire filler welding is used.

[0121] The parameters for laser welding pipeline fabrication are as follows: laser beam tilt forward 8°, defocusing amount -2mm, angle between welding wire and base material 60°, angle between shielding gas nozzle and base material 60°, and distance between shielding gas nozzle and molten pool 45mm.

[0122] The process in this embodiment is as follows:

[0123] The first step was a trial weld without filler wire. After parameter optimization, a good weld formation was achieved. Specific parameters were: laser output power 5.5kW, welding speed 1.8m / min, weld bevel gap 0mm, and extrusion via forming rollers. After welding, the welded pipe was cut off, and the width of the weld on the front side was measured to be 2.52mm, and the width of the weld on the back side was 1.64mm.

[0124] The second step is to determine the welding wire diameter and the wire feeding speed.

[0125] First, calculate the weld cross-sectional area according to formula (a): S1 = 10.4 mm. 2 .

[0126] Then, calculate the filler wire amount, determine the range of welding wire diameter based on the filler wire amount, and according to formula (d), follow v 丝 =1.0v 焊 The calculation yields d ≥ 1.68 mm, excluding selectable welding wire diameter specifications. Therefore, further calculation of v is needed. 丝 =0.8v 焊 and v 丝 =1.2v 焊 The diameter ranges were calculated to be d≥1.88mm and d≥1.54mm respectively. Therefore, a welding wire with a diameter of 1.6mm was selected.

[0127] Then, according to formula (e), substitute the selected wire diameter of 1.6mm from the previous step to calculate the wire feed speed v. 丝 Range: v 丝 If the speed is ≥1.99m / min, select a wire feeding speed of 2m / min.

[0128] The third step is the formal welding. The laser output power is 5.5kW, the welding speed is 1.8m / min, the laser beam tilt is 8°, and the defocusing amount is -2mm. The weld bevel gap is 0mm, and the weld is extruded via forming rollers. The shielding gas used is 99.999% argon, with a flow rate of 20L / min. The angle between the shielding gas nozzle and the base material is 60°, and the distance between the shielding gas nozzle and the molten pool is 45mm. The welding wire diameter is 1.6mm, the wire feed speed is 2m / min, and the angle between the welding wire and the base material is 60°. The post-weld heat treatment temperature is 490℃.

[0129] The obtained welded pipe did not crack when flattened at the weld seam, and the weld seam did not crack after the pipe was expanded 1.3 times.

[0130] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any substitutions, modifications, combinations, changes, simplifications, etc., made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A laser welding method for T4003 ferritic stainless steel, characterized in that, The laser welding method is implemented using laser welding pipeline fabrication equipment, which includes a wire feeding device, a laser welding device, and a post-weld heat treatment device; the laser welding method includes the following steps: The first step is to perform debugging and determine the parameter values; The second step is to determine the wire diameter and wire feeding speed based on the cross-sectional area of ​​the weld and the elemental composition of the base material, welding wire, and weld. The third step is to weld the base material and then heat-treat the resulting weld. The second step includes: (1) Calculate the weld cross-sectional area based on the weld width on the front and back sides according to formula (a): （a） in: S1 is the cross-sectional area of ​​the weld, in mm. 2 ; D1 is the weld width on the front side, in mm; D2 is the weld width on the back side, in mm; t is the thickness of the base material, in mm; (2) Calculate the amount of filler wire: The nickel content of the weld is determined according to formula (b), and the filler wire amount per unit weld length is determined according to formula (c). Nickel content in weld (b) （c） in: S2 is the amount of filler wire per unit weld length; d is the diameter of the welding wire, in mm; v 丝 It is the wire feeding speed, in m / min; v 焊 This refers to the welding speed, measured in m / min. (3) Determine the range of welding wire diameter d according to formulas (b) and (c), and select the welding wire diameter; (4) Determine the wire feeding speed v according to formula (b) and formula (c). 丝 The range.

2. The laser welding method according to claim 1, characterized in that, The setup of the laser welding pipeline includes: placing the laser beam, welding wire, and shielding gas nozzle on the same plane, perpendicular to the base material to be welded and intersecting the center line of the weld bevel; the forward tilt angle of the laser beam is 5°~10°, and the defocusing amount ranges from -5 to 0 mm; the angle between the welding wire and the base material is 45°~70°, and the welding wire fills the laser spot in the molten pool; the shielding gas nozzle is behind the laser beam, with an angle of 45°~70° to the base material, and a distance of 30~50 mm from the molten pool.

3. The laser welding method according to claim 1, characterized in that, In the first step, the parameter values ​​are determined as follows: laser power is 1kW~1.5kW per millimeter of thickness, welding speed is 1.5m / min~2.5m / min, welding bevel is 0mm and extruded through forming rollers.

4. The laser welding method according to claim 1, characterized in that, The base material has a nickel content of 0.5%, and the weld has a nickel content of ≥2%. The elemental composition of the welding wire is: C≤0.02%, Si≤0.5%, 1.0%≤Mn≤2.0%, P≤0.025%, S≤0.020%, 19.5%≤Cr≤20.5%, 9%≤Ni≤10%, with the balance being Fe and unavoidable impurity elements.

5. The laser welding method according to claim 1, characterized in that, In step (3), the range of the welding wire diameter d is calculated according to formula (d): （d） The available welding wire diameters include: 0.8mm, 0.9mm, 1.0mm, 1.2mm, 1.4mm, and 1.6mm. Then, according to formula (d) according to v 丝 =v 焊 If the calculation yields d ≥ d1, and this range includes the specified welding wire diameter, then the diameter value closest to d1 is selected as the welding wire diameter. If this range does not include the specified welding wire diameter, then, according to formula (d), based on v... 丝 =0.8V 焊 The calculation yields d ≥ d², according to v 丝 =1.2v 焊 The calculation shows that d ≥ d3, and the diameter value of the welding wire between d2 and d3 is taken as the welding wire diameter.

6. The laser welding method according to claim 1, characterized in that, In step (4), the wire feed speed v is determined according to formula (e) and the selected welding wire diameter. 丝 Scope: （e） Then, the final wire feeding speed is selected as a value close to the lower limit of the range.

7. The laser welding method according to any one of claims 1 to 6, characterized in that, In the third step, the heat treatment temperature is 400~500℃.

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