A method for argon arc welding of high-strength steel BS700MCK2.

Abstract

This invention relates to an argon arc welding method for high-strength steel made of BS700MCK2, belonging to the field of argon arc welding technology. It includes pre-welding preparation to obtain a weldment with a V-groove, a corresponding high-strength steel welding wire, and welding fixtures. The weldment is made of BS700MCK2 high-strength steel, and the welding wire is made of GHQ80 material. The method involves installing the weldment in the fixture and performing tungsten inert gas (TIG) welding for tack welding; performing TIG welding for root welding; performing MIG welding for filler welding; and then finishing and inspecting the weld appearance. By cleaning the heat-affected zone, CNC machining the groove, using fixtures for fixing and preheating the weldment, performing TIG welding for tack welding, root welding, and MIG welding for filler welding, this method achieves argon arc welding of BS700MCK2 high-strength steel, avoiding cracking while producing a high-quality and aesthetically pleasing weld.

Description

Technical Field

[0001] This invention relates to the field of argon arc welding technology, specifically to an argon arc welding method for high-strength steel made of BS700MCK2. Background Technology

[0002] BS700MCK2 high-strength steel is one of Baosteel's BS series high-strength steels, belonging to low-alloy high-strength structural steel. It not only possesses high yield strength and tensile strength but also maintains good plasticity and toughness, making it widely used in the manufacturing industries of machinery, vehicle structures, and pressure vessels.

[0003] The high strength of BS700MCK2 high-strength steel structural components makes them highly sensitive to welding cracks. If the welding process is not properly implemented, the tensile strength of the weld will decrease, and defects such as cracks and lack of fusion will easily occur, leaving great quality risks for product application.

[0004] Therefore, a high-strength steel argon arc welding method using BS700MCK2 material is needed to solve the above problems. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides an argon arc welding method for high-strength steel of material BS700MCK2.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A method for argon arc welding of high-strength steel BS700MCK2 includes the following steps:

[0008] Step 1: Pre-welding preparation, including cleaning the heat-affected zone of the weldment, CNC machining the weldment with a V-shaped bevel, and making a set of welding fixtures that can fix and preheat the weldment.

[0009] Step 2: Install the welded parts in the tooling and apply tungsten inert gas (TIG) welding to secure them;

[0010] Step 3: Perform root welding using tungsten inert gas (TIG) welding;

[0011] Step 4: Perform gas metal arc welding (GMAW) filler welding;

[0012] Step 5: Repair the appearance of the weld and inspect the weld bead.

[0013] In some specific implementations, pre-welding preparation further includes:

[0014] For the area within 40mm of the heat-affected zone of the welded parts, use a wire brush to grind and remove corrosion pits and rust spots until the metal luster is exposed.

[0015] A single-sided V-shaped bevel is CNC machined on the long side of the welded part. The bevel angle is 30 degrees, the blunt edge is between 0.5mm and 1mm, and the surface roughness Ra value of the bevel is not greater than 3.2um.

[0016] Make a welding fixture with a platform for fixing the welding parts on the upper side. The height of the pressure plates at both ends can be adjusted by rotating bolts. Leave a gap of not less than 80mm at the bottom of the fixture. If necessary, use the flame gun at the bottom of the fixture for flame preheating.

[0017] In some specific embodiments, mounting the weldment within the tooling and performing tungsten inert gas (TIG) welding further includes:

[0018] Two welded parts, each measuring 6mm × 100mm × 200mm, are joined together and placed on the fixed platform of the fixture. The welded parts are pressed into the fixture by tightening the pressure plates at both ends with bolts. The gap between the welded parts is adjusted to the range of 0 to 0.5mm.

[0019] For tungsten inert gas (TIG) welding, apply a weld point approximately every 100mm. The weld point should penetrate the blunt edge, with a length of 2-4mm and a weld leg height of 1-2mm. Use φ2mm welding wire, a welding current of 240-280A, a welding voltage of 27V, and a shielding gas of 80% Ar and 20% CO2 with a flow rate of 20-24L / min.

[0020] In some specific embodiments, root welding using tungsten inert gas welding further includes:

[0021] The welding process involves manually moving the filler wire from one side to the other using tungsten inert gas welding, applying four weld passes, and welding three layers.

[0022] The first layer of welding uses low current and slow speed to ensure that the blunt edge is completely melted through.

[0023] The second layer of welding uses high current, high voltage, and rapid welding, and the interpass temperature must not be lower than 150℃;

[0024] The current, voltage, and speed for the third layer of welding are the same as those for the second layer, and the interlayer temperature must not be lower than 150℃.

[0025] The thickness of the three-layer weld after welding is 2-3 mm.

[0026] In some specific implementations, the specific parameters for tungsten inert gas welding include:

[0027] During the first layer welding process, the welding wire specification is φ2mm, the welding current is 120~160A, the welding voltage is 24V, the welding speed is 100~140mm / min, the shielding gas is a mixture of 80%Ar and 20%CO2, and the shielding gas flow rate is 10~16L / min.

[0028] During the welding of the second and third layers, the current is adjusted to 180-220A, the welding voltage is adjusted to 27V, and the welding speed is adjusted to 180-240mm / min. Other welding parameters are the same as those for the first layer.

[0029] In some specific embodiments, the filler welding using gas metal arc welding further includes:

[0030] If the temperature cannot reach the welding conditions, turn on the flame gun at the bottom of the tooling for local flame preheating. The preheating range is within 40mm around the weld width.

[0031] Multi-layer, multi-pass welding is employed to ensure that the interpass temperature of each layer is not lower than 150℃;

[0032] When welding the last layer, the reinforcement height should be controlled between 0.5 and 1.5 mm, the weld should transition smoothly with the base material, and the weld filling thickness should be 2 to 3 mm.

[0033] In some specific implementations, the specific parameters for multi-layer, multi-pass welding in gas metal arc welding include:

[0034] The welding wire specification is φ1.2mm, the welding current is 200~240A, the welding voltage is 27V, the welding speed is 220~260mm / min, the shielding gas is 80%Ar and 20%CO2, and the shielding gas flow rate is 16~20L / min.

[0035] In some specific embodiments, finishing the weld appearance and inspecting the weld bead further includes:

[0036] Use a wire brush or hand grinder to polish the weld bead, remove the slag from the weld edges, and smooth out any unevenness in the weld pattern.

[0037] In some specific implementations, weld inspection can be performed by testing to demonstrate its structural characteristics, which may include X-ray inspection and mechanical testing.

[0038] Specifically, X-ray inspection primarily checks for defects such as cracks, weld beads, porosity, and slag inclusions inside the weld after arc welding, ensuring it meets the Class I quality standard requirements of QJ176A. In mechanical testing, test pieces are taken from the arc-welded components and placed on a tensile testing machine for mechanical property testing. The tensile strength of the test pieces must reach at least 90% of the lower limit of the tensile strength of the base material.

[0039] In some specific implementations, the above-mentioned spot welding, root welding, and filler welding processes all have temperature requirements, which must meet the following conditions: ambient temperature > 10℃ and humidity ≤ 75%.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. This invention ensures the purity of the material by cleaning the heat-affected zone before welding, thus reducing welding defects. CNC machining of the V-groove ensures a surface roughness Ra value of no more than 3.2µm, resulting in smoother manual wire feeding in TIG welding and automatic wire feeding in MIG welding. Fixtures that can be fixed and preheated not only control weldment deformation but also rationally control the welding temperature, reducing the susceptibility to welding cracks. TIG spot fixing further controls weldment deformation, ensuring it remains in a good welding condition. A 3-layer, 4-pass welding method is used for TIG root welding, refining the grain structure of the bottom weld and ensuring weld stability. MIG filler welding improves efficiency, reduces heat dissipation, effectively controls interpass temperature, avoids cracking, and ensures a smooth transition between the weld and base material, reducing stress concentration and resulting in excellent weld mechanical properties and an aesthetically pleasing appearance. Attached Figure Description

[0042] Figure 1 This is a flowchart of the welding process of the present invention;

[0043] Figure 2 This is a schematic diagram of the weld bead layers of the welded part bevel and the root welding of the tungsten inert gas welding in an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the welding fixture in an embodiment of the present invention. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] Due to the high strength of BS700MCK2 high-strength steel structural components, they are highly sensitive to welding cracks. If the welding process is not properly implemented, the tensile strength of the weld will decrease, and defects such as cracks and lack of fusion are also likely to occur, leaving great potential quality risks for product application.

[0047] To prevent the formation of welding cracks, this invention provides an argon arc welding method for high-strength steel BS700MCK2, aiming to achieve high-quality welds, superior mechanical properties, and aesthetically pleasing appearance in the argon arc welding of this grade of high-strength steel.

[0048] like Figures 1 to 3 As shown, it includes the following steps:

[0049] Step 1: Pre-welding preparation, including cleaning the heat-affected zone of the weldment, CNC machining the weldment with a V-shaped bevel, and making a set of welding fixtures that can fix and preheat the weldment.

[0050] Step 2: Install the welded parts in the tooling and apply tungsten inert gas (TIG) welding to secure them;

[0051] Step 3: Perform root welding using tungsten inert gas (TIG) welding;

[0052] Step 4: Perform gas metal arc welding (GMAW) filler welding;

[0053] Step 5: Repair the appearance of the weld and inspect the weld bead.

[0054] Pre-welding preparation, including cleaning the heat-affected zone, ensures the purity of the material and reduces welding defects. CNC machining creates a V-shaped bevel with a surface roughness Ra value of no more than 3.2µm, resulting in smoother manual wire feeding in TIG welding and automatic wire feeding in MIG welding. Fixtures that can be fixed and preheated not only control weldment deformation but also regulate welding temperature, reducing weld crack sensitivity. TIG spot treatment further controls weldment deformation, ensuring it remains in good welding condition. A 3-layer, 4-pass welding method is used for TIG root welding, refining the grain structure of the bottom weld and ensuring weld stability. Finally, MIG filler welding improves efficiency, reduces heat dissipation, effectively controls interpass temperature, prevents cracking, and results in welds with excellent mechanical properties and an aesthetically pleasing appearance.

[0055] Pre-welding preparations include:

[0056] Step 1.1: Clean the heat-affected zone of the welded parts;

[0057] Step 1.2: CNC machine the welded parts with V-shaped bevels;

[0058] Step 1.3: Make a welding fixture that can fix and preheat the welding parts.

[0059] Pre-welding preparation and cleaning of the heat-affected zone ensure the purity of the material itself and reduce welding defects; CNC machining of the V-shaped bevel ensures that the surface roughness Ra value is no greater than 3.2um, making manual wire feeding in tungsten inert gas welding and automatic wire feeding in metal inert gas welding smoother; the fixture for fixing and preheating the welding parts can not only control the deformation of the welding parts, but also reasonably control the temperature during welding, reducing the sensitivity to welding cracks.

[0060] Step 1.1: Clean the heat-affected zone of the weldment. This includes using a wire brush to grind the area within 40mm of the heat-affected zone of the weldment to remove corrosion pits and rust spots until the metal luster is exposed. The 40mm range of the heat-affected zone is the area within 40mm around the weld. After cleaning, the contamination of impurities is reduced, and the heat-affected zone is in a good state ready for welding, thus reducing welding defects.

[0061] Step 1.2: CNC machining of the V-groove weldment involves CNC machining a welding groove on the long side of the weldment, single-sided machining, with a groove angle of 30 degrees, the opposite side of the angle in the thickness direction, a blunt edge allowance between 0.5mm and 1mm, and a groove surface roughness Ra value not exceeding 3.2um. A well-designed groove structure makes manual wire feeding in tungsten inert gas welding and automatic wire feeding in metal inert gas welding smoother and more efficient, improving weld quality and ensuring a beautiful weld appearance.

[0062] Step 1.3: The welding fixture for fixing and preheating the welded parts includes a platform on the upper side of the fixture for fixing the welded parts. The height of the pressure plates at both ends can be adjusted by rotating bolts to clamp the welded parts. A gap of not less than 80mm is left at the bottom of the fixture. If necessary, a flame gun at the bottom of the fixture is used for flame preheating. The flame gun can be moved freely by hand along the direction of the hole axis.

[0063] Step 2: Install the weldment in the tooling and perform tungsten inert gas (TIG) welding to fix the weldment. This includes:

[0064] Step 2.1: Butt-joint two weldment pieces, each with dimensions of 6mm × 100mm × 200mm, with the 6mm × 200mm surface as the contact surface. Place them on the fixed platform of the fixture, and tighten the end plates with bolts to press the weldment pieces into the fixture. Then adjust the butt joint gap of the weldment pieces to control it within the range of 0–0.5mm. The fixture for fixing and preheating weldment pieces can not only control the deformation of the weldment pieces, but also reasonably control the temperature during welding, reducing the sensitivity to welding cracks.

[0065] Step 2.2: Apply tungsten inert gas (TIG) welding at approximately 100mm intervals, using rapid spot welding. The weld should penetrate the blunt edge, with a length of 2-4mm and a weld leg height of 1-2mm. Use φ2mm welding wire, a welding current of 240-280A, a welding voltage of 27V, and a shielding gas composition of 80% Ar and 20% CO2 at a flow rate of 20-24L / min. TIG welding further controls deformation of the weldment, ensuring it remains in a good welding condition.

[0066] Step 3, root welding with tungsten inert gas (TIG) welding includes:

[0067] The welding process involves manually feeding wire from one side to the other using tungsten inert gas welding, applying four weld passes, and welding three layers.

[0068] Step 3.1: The first layer of welding consists of one weld bead, using a low current and slow speed to ensure complete penetration of the blunt edge.

[0069] Step 3.2: The second layer of welding includes one weld pass. High current, high voltage and fast welding are used. The second weld pass is performed while ensuring that the interlayer temperature with the first weld pass is not lower than 150°C.

[0070] Step 3.3: The third layer of welding includes two weld passes. The welding current, welding voltage, and welding speed are kept consistent with those used in the second layer of welding. The third and fourth weld passes are performed while ensuring that the interlayer temperature between the second and third weld passes is not lower than 150°C.

[0071] Using a 3-layer, 4-pass tungsten inert gas (TIG) welding method for the root of the weld can refine the grain structure of the bottom weld, thereby ensuring the stability of the weld. The thickness of the three-layer TIG weld after welding is 2–3 mm.

[0072] Preferably, in step 3.1, during the first layer of tungsten inert gas (TIG) welding, a φ2mm welding wire is used, the welding current is 120–160A, the welding voltage is 24V, the welding speed is 100–140mm / min, and the shielding gas is a mixture of 80% Ar and 20% CO2 with a flow rate of 10–16L / min. Similarly, preferably, in step 3.2, during the second and third layers of TIG welding, the current is adjusted to 180–220A, the welding voltage to 27V, and the welding speed to 180–240mm / min, with other welding parameters consistent with the first layer. The thickness of the three-layer weld is 2–3mm.

[0073] Step 4, the filler welding of the gas metal arc welding process includes:

[0074] Step 4.1: After root welding, ensure the preheating temperature is between 150℃ and 250℃ before performing GIGABYTE filler welding. If the temperature cannot meet the welding conditions, turn on the flame gun at the bottom of the tooling for flame preheating. Manually move the flame gun freely along the hole axis to uniformly and locally preheat the weld to achieve temperature control.

[0075] Step 4.2: Using GIGABYTE (Gastrointestinal Arc Welding), slowly move the welding torch from one side to the other with automatic wire feeding, employing multi-layer, multi-pass welding. Ensure that the interpass temperature of each layer does not fall below 150℃ before welding the next layer. When welding the last layer, control the reinforcement height between 0.5 and 1.5 mm, ensuring a smooth transition between the weld and the base material. The filler thickness of the GIGABYTE weld should be 2 to 3 mm.

[0076] In step 4.1, uniform local preheating of the weld to achieve temperature control refers to localized flame heating within a 40mm radius around the weld, based on the weld width of the welded part. Preferably, in the multi-layer, multi-pass GIGABYTE welding process in step 4.2, the welding wire specification is φ1.2mm, the welding current is 200-240A, the welding voltage is 27V, the welding speed is 220-260mm / min, the shielding gas is 80%Ar and 20%CO2, and the shielding gas flow rate is 16-20L / min. Through high-efficiency welding using GIGABYTE, heat dissipation is reduced, interpass temperature is effectively controlled, and cracks are avoided. Simultaneously, the transition between the weld and the base material is smooth, reducing stress concentration, resulting in excellent weld mechanical properties and an aesthetically pleasing appearance.

[0077] Step 5: Repair the appearance of the weld and inspect the weld bead.

[0078] Use a wire brush or hand grinder to polish the weld bead, remove slag from the weld edges, smooth out uneven weld patterns, reduce stress concentration, improve weld quality, and enhance appearance.

[0079] Weld inspection can verify its structural characteristics through experiments, which may include X-ray inspection and mechanical testing.

[0080] Specifically, X-ray inspection primarily checks for defects such as cracks, weld beads, porosity, and slag inclusions inside the weld after arc welding, ensuring it meets the Class I quality standard requirements of QJ176A. In mechanical testing, test pieces are taken from the arc-welded components and placed on a tensile testing machine for mechanical property testing. The tensile strength of the test pieces must reach at least 90% of the lower limit of the tensile strength of the base material.

[0081] All of the above-mentioned tack welding, root welding, and filler welding processes have temperature requirements, which must meet the following conditions: ambient temperature > 10℃ and humidity ≤ 75%.

[0082] Example: This example provides an argon arc welding method for BS700MCK2 high-strength steel. This method aims to ensure excellent weld quality, superior mechanical properties, and aesthetically pleasing appearance, while effectively preventing weld cracks. The detailed steps of this method are as follows:

[0083] Step 1: Pre-welding preparation

[0084] Cleaning the heat-affected zone of the weld: Use a wire brush to grind the heat-affected zone (within 40mm of the weld) to remove corrosion pits, rust spots, and other impurities until the metal shines through. This step ensures the purity of the welding material and reduces the occurrence of welding defects.

[0085] CNC machining of V-grooves: A single-sided V-groove is CNC machined on the long side of the weldment, with a groove angle of 30 degrees, a blunt edge allowance controlled between 0.5mm and 1mm, and a surface roughness Ra value not exceeding 3.2µm. A reasonable groove structure facilitates smoother wire feeding during tungsten inert gas welding (TIG) and metal arc welding (MAG), thereby improving weld quality.

[0086] Fabricate the welding fixture: Construct a fixture to hold and preheat the workpiece. The fixture has a fixed platform on the upper side, and the height of the end plates can be adjusted by rotating bolts to clamp the workpiece. A gap of at least 80mm is left at the bottom of the fixture to facilitate localized preheating with a flame torch if necessary. The flame torch can be manually moved freely along the hole axis to achieve precise temperature control.

[0087] Step 2: Installation and tack fixing of welded components

[0088] Install the welded parts: Join two welded parts with dimensions of 6mm×100mm×200mm together and place them on the fixed platform of the fixture. Tighten the end plates with bolts to press the welded parts into the fixture, and adjust the joint gap of the welded parts to within the range of 0 to 0.5mm.

[0089] TIG welding tack welding: TIG welding is used for tack welding, with one weld point applied approximately every 100mm. The weld point must penetrate the blunt edge, with a length controlled between 2 and 4mm and a weld leg height of 1 to 2mm. The welding wire specification is φ2mm, the welding current is 240–280A, the welding voltage is 27V, and the shielding gas is a mixture of 80% Ar and 20% CO2, with a shielding gas flow rate of 20–24L / min. Tack welding helps to further control the deformation of the weldment.

[0090] Step 3: Root welding of tungsten inert gas (TIG)

[0091] The welding process was carried out by manually moving the filler wire from one side to the other using tungsten inert gas welding, applying a total of 4 weld passes in 3 layers.

[0092] First layer of welding: Use low current and slow speed to ensure complete penetration of the blunt edge. Use φ2mm welding wire, 120–160A welding current, 24V welding voltage, and 100–140mm / min welding speed. The shielding gas and flow rate are the same as for tack welding.

[0093] Second layer welding: Use high current, high voltage, and high-speed welding. Perform the second weld pass while ensuring the interpass temperature with the first weld pass does not fall below 150℃. Adjust the welding current to 180–220A, the welding voltage to 27V, and the welding speed to 180–240mm / min. Other welding parameters are the same as the first layer.

[0094] The third layer of welding consists of two weld passes, with the same welding parameters as the second layer. The third and fourth weld passes are performed while ensuring that the interpass temperature with the second layer does not fall below 150°C. The final thickness of the three-layer weld is 2–3 mm.

[0095] Step 4: GIGABYTE filler welding

[0096] Preheating: After root welding, ensure the preheating temperature is between 150℃ and 250℃ before performing GIGABYTE filler welding. If the temperature cannot reach the welding conditions, turn on the flame torch at the bottom of the tooling for local preheating. The preheating range is within 40mm around the weld width to ensure uniform temperature.

[0097] Filler welding: Using GIGABYTE (Gastrointestinal Array) welding, the welding torch is moved slowly from one side to the other with automatic wire feeding for multi-layer, multi-pass welding. During each layer, ensure the interpass temperature does not fall below 150℃. For the final layer, control the reinforcement height between 0.5 and 1.5 mm, ensuring a smooth transition between the weld and the base metal. The filler thickness is 2–3 mm. The welding wire specification is φ1.2 mm, the welding current is 200–240 A, the welding voltage is 27 V, and the welding speed is 220–260 mm / min. The shielding gas and flow rate are the same as for GIGABYTE.

[0098] Step 5: Weld Repair and Inspection

[0099] Finishing the weld: Use a wire brush or hand grinder to grind the weld bead, removing slag and unevenness from the weld edges. This step helps to improve stress concentration, enhance weld quality, and improve appearance.

[0100] Weld inspection: The weld is inspected using X-ray inspection and mechanical testing. X-ray inspection mainly checks for defects such as cracks, weld beads, porosity, and slag inclusions inside the weld, which must meet the Class I quality standard requirements of QJ176A. Mechanical testing involves cutting test pieces from the welded parts and placing them on a tensile testing machine to ensure that the tensile strength of the test pieces reaches more than 90% of the lower limit of the tensile strength of the base material.

[0101] Precautions:

[0102] The welding process must be carried out under conditions of ambient temperature >10℃ and humidity ≤75%.

[0103] Temperature must be strictly controlled during tack welding, root welding, and filler welding to meet welding requirements.

[0104] Through the implementation of the above steps, this embodiment successfully achieved argon arc welding of BS700MCK2 high-strength steel. The weld quality is excellent, the mechanical properties are outstanding, and the appearance is beautiful, effectively preventing the generation of welding cracks.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for argon arc welding of high-strength steel of material BS700MCK2, characterized in that, Includes the following steps: Step 1: Pre-welding preparation, including cleaning the heat-affected zone of the weldment, CNC machining the weldment with a V-shaped bevel, and making a set of welding fixtures that can fix and preheat the weldment. Step 2: Install the welded parts in the tooling and apply tungsten inert gas (TIG) welding to secure them; Step 3: Perform root welding using tungsten inert gas (TIG) welding; Step 4: Perform gas metal arc welding (GMAW) filler welding; Step 5: Trim the appearance of the weld and inspect the weld bead; The root welding using tungsten inert gas welding further includes: The welding process involves manually moving the filler wire from one side to the other using tungsten inert gas welding, applying four weld passes, and welding three layers. The first layer of welding uses low current and slow speed to ensure that the blunt edge is completely melted through. The second layer of welding uses high current, high voltage, and rapid welding, and the interpass temperature must not be lower than 150℃; The current, voltage, and speed for the third layer of welding are the same as those for the second layer, and the interlayer temperature must not be lower than 150℃. The thickness of the three-layer weld after welding is 2-3 mm; The specific parameters for the tungsten inert gas welding include: During the first layer welding process, the welding wire specification is φ2mm, the welding current is 120~160A, the welding voltage is 24V, the welding speed is 100~140mm / min, the shielding gas is a mixture of 80%Ar and 20%CO2, and the shielding gas flow rate is 10~16L / min. During the welding of the second and third layers, the current is adjusted to 180-220A, the welding voltage is adjusted to 27V, and the welding speed is adjusted to 180-240mm / min. Other welding parameters are the same as those for the first layer. The filler welding using gas metal arc welding further includes: If the temperature cannot reach the welding conditions, turn on the flame gun at the bottom of the tooling for local flame preheating. The preheating range is within 40mm around the weld width. Multi-layer, multi-pass welding is employed to ensure that the interpass temperature of each layer is not lower than 150℃; When welding the last layer, the reinforcement height should be controlled between 0.5 and 1.5 mm, the weld should transition smoothly with the base material, and the weld filling thickness should be 2 to 3 mm. The specific parameters for multi-layer, multi-pass welding using gas metal arc welding include: The welding wire specification is φ1.2mm, the welding current is 200~240A, the welding voltage is 27V, the welding speed is 220~260mm / min, the shielding gas is 80%Ar and 20%CO2, and the shielding gas flow rate is 16~20L / min.

2. The argon arc welding method for high-strength steel of material BS700MCK2 according to claim 1, characterized in that, The pre-welding preparation further includes: For the area within 40mm of the heat-affected zone of the welded parts, use a wire brush to grind and remove corrosion pits and rust spots until the metal luster is exposed. A single-sided V-shaped bevel is CNC machined on the long side of the welded part. The bevel angle is 30 degrees, the blunt edge is between 0.5mm and 1mm, and the surface roughness Ra value of the bevel is not greater than 3.2um. Make a welding fixture with a platform for fixing the welding parts on the upper side. The height of the pressure plates at both ends can be adjusted by rotating bolts. Leave a gap of not less than 80mm at the bottom of the fixture. If necessary, use the flame gun at the bottom of the fixture for flame preheating.

3. The argon arc welding method for high-strength steel of material BS700MCK2 according to claim 2, characterized in that, The step of installing the weldment within the tooling and applying tungsten inert gas (TIG) welding spot fixation further includes: Two welded parts, each measuring 6mm × 100mm × 200mm, are joined together and placed on the fixed platform of the fixture. The welded parts are pressed into the fixture by tightening the pressure plates at both ends with bolts. The gap between the welded parts is adjusted to the range of 0 to 0.5mm. For tungsten inert gas (TIG) welding, apply a weld point approximately every 100mm. The weld point should penetrate the blunt edge, with a length of 2-4mm and a weld leg height of 1-2mm. Use φ2mm welding wire, a welding current of 240-280A, a welding voltage of 27V, and a shielding gas of 80% Ar and 20% CO2 with a flow rate of 20-24L / min.

4. The argon arc welding method for high-strength steel of material BS700MCK2 according to claim 1, characterized in that, The process of finishing the weld appearance and inspecting the weld bead further includes: Use a wire brush or hand grinder to polish the weld bead, remove the slag from the weld edges, and smooth out any unevenness in the weld pattern.

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