A double-wire free-root-cleaning MAG welding process for thick-walled double V-grooves

Abstract

The present invention relates to a double-wire root-free MAG welding process for thick-walled double V grooves, including using a mechanical processing or flame cutting method to groove a workpiece to be welded; then selecting a welding material matching the parent material, and preheating before welding according to the parent material characteristics and related process requirements, welding can only be performed after the weldment reaches the preheating temperature, strictly controlling the interlayer temperature, clamping the assembled workpiece on the tooling, and welding robots equipped with double-wire welding guns for welding; during the welding process, by observing the molten pool and the post-welding forming, the welding parameters, swing width, etc. are adjusted and controlled in real time through the robot teaching display screen to ensure weld formation and stable arc burning; after welding, the weld appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness test and other quality inspections are performed. The advantages of the present invention are saving labor costs, simplifying procedures, improving welding quality and efficiency, and reducing welding costs.

Description

Technical Field

[0001] The invention relates to the technical field of metal-electrode gas shielded automatic welding technology, in particular to a double-wire root cleaning-free MAG welding technology method for thick-walled double V grooves. Background Art

[0002] At present, thick-walled workpieces are widely used in engineering machinery and offshore oil engineering industries. Their main material is low-alloy steel, which has good weldability. However, according to the requirements of different project sites and service environments, preheating and interlayer temperature control are required. Previously, SMAW or manual MAG was used, which had the following defects: First, the welding workload was large when single-wire welding was used for base and single-wire welding for filling and covering, and the quality control requirements were high, the welding efficiency was low and the cost was high; secondly, according to the normal process, after the welding of the small groove on the back side, grinding and root cleaning operations were required before welding the large groove on the front side. This was to minimize the probability of defects in the base layers on the front and back sides, but the increase in the grinding and root cleaning process undoubtedly slowed down the overall work efficiency and the process was relatively complicated; furthermore, the biggest difficulty was to ensure the quality of the base layers on both sides of the double V groove and the good fusion of both sides of each weld. The existing welding process often resulted in welding defects such as base welding and the lack of fusion at the joint of the two base layers during operation. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of low efficiency, large workload, high cost and easy occurrence of welding defects in existing single-wire welding, and provide a double-wire root-free MAG welding process method for thick-walled double V-grooves, which saves labor costs, simplifies the process, is simple to operate, and eliminates the probability of welding defects as much as possible, thereby improving welding efficiency and reducing welding costs.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A double-wire root-cleaning-free MAG welding process for thick-walled double V-grooves, the specific steps are as follows, including:

[0006] (1) Groove processing: Use mechanical processing or flame cutting to make double V-shaped grooves on the workpiece to be welded. The depth of the large groove on the front side ranges from 25mm to 100mm, the blunt edge is 2~3mm, and the assembly gap is 0~1mm. Be careful not to deform during the groove processing process and ensure that the misalignment is 0~1mm;

[0007] (2) Welding material preparation: Select welding materials that match the parent material. The parent material of the welding material is D36, the workpiece specifications are 1000×200×38mm, the yield strength is ≥355Mpa, the tensile strength is 490~630Mpa, and the gas shielded welding wire JQ·MG50S-6 with a wire diameter of Φ1.2mm is used;

[0008] (3) Workpiece preheating and clamping: Preheat the workpiece before welding according to the characteristics of the parent material and related process requirements to avoid cold cracks. Welding can only be carried out after the weldment reaches the preheating temperature. Strictly control the interlayer temperature. Clamp the assembled workpiece on the tooling. The welding robot is equipped with a double-wire welding gun for welding. The welding position is 1G, and the welding gun is perpendicular to the workpiece.

[0009] (4) Double-wire welding: During the welding process, observe the molten pool and post-weld formation through the robot teaching pendant display screen. According to different narrow and deep grooves, with the assistance of the arc tracking function, adjust the welding parameters, swing frequency, swing width, inductance parameters and arc length to ensure weld formation and stable arc burning. After the welding of the small groove on the back is completed, there is no need to grind and clean the root before welding the large groove on the front. Direct welding can be carried out. When welding the large groove on the front, the double-wire deep-melting welding method is used. This method has the characteristics of large melting depth. The arc can reach the small groove on the back to penetrate the bottom layer, so the probability of defects such as incomplete fusion can be reduced to a minimum.

[0010] (5) Post-weld inspection: After welding, the weld undergoes quality inspections such as weld appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness test.

[0011] Furthermore, in the step (1), rust, oil and other contaminants within a range of 20 to 30 mm on both sides of the positive and negative grooves of the workpiece are polished away with a grinder to prevent the formation and quality of the weld from being affected.

[0012] Furthermore, in step (2), the welding wire is required to be dry, oil-free and rust-free, and the welding wire used is subjected to corresponding pre-welding inspections before welding, such as checking the factory warranty and the tightness inspection of the welding wire reel before opening.

[0013] Furthermore, in step (3), the preheating temperature of the weldment is 80-90°C.

[0014] Furthermore, in the step (4), single-wire welding is adopted for the small groove side on the back side, and its backing welding process parameters are welding current 280-290A, arc voltage 31-32V, and wire feeding speed 12m / min. Double-wire welding is adopted for the large groove side on the front side, and its backing welding process parameters are welding current 356 / 218A, arc voltage 38V / 23V, welding speed 450mm / min, and wire feeding speed 12 / 8m / min, respectively. The above data are much more efficient than single-wire welding under the same conditions.

[0015] Furthermore, in the step (4), the interlayer temperature is controlled at 100-150°C when multi-layer and multi-pass welding is adopted.

[0016] Furthermore, in the step (4), the positive and negative grooves are both welded by MAG welding, the welding current polarity is DCEP, there are ten welding layers or welds, the first layer of base welding uses double wires, the welding current is (350~360) / (210~220)A, the arc voltage is 38 / 23V, the welding speed is 450mm / min, the minimum line energy is 24.2KJ / cm, and the maximum line energy is 25KJ / cm.

[0017] Furthermore, in step (4), the second to seventh layers of filling are made of double wires, the welding current is (200-210) / (180-190) A, the arc voltage is 30 / 30, the welding speed is 400 mm / min, the minimum wire energy is 17.1 KJ / cm and the maximum is 18 KJ / cm.

[0018] Furthermore, in the step (4), the eighth to tenth layers of cover are made of single wire, the welding current is 280-290A, the arc voltage is 31, the welding speed is 350mm / min, the minimum line energy is 14.88KJ / cm and the maximum is 15.42KJ / cm.

[0019] In the technical solution of the present invention, under the condition of wall thickness of 25-100mm, by adjusting and controlling the welding position, welding parameters, swing width, etc., the welding process is stable and basically defect-free, and the preheating temperature, interlayer temperature and heat input before welding are strictly controlled according to the project and process requirements. The method is used to weld the thick-walled double V-groove weld base layer, reduce the grinding and root cleaning process of the large groove side, simplify the processing process, save production time, improve welding efficiency, and at the same time, the weld is well formed, and there are no defects such as cracks, pores, slag inclusions, and incomplete penetration in the weld as a whole, ensuring the welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of the groove assembly of the present invention. Implementation Example

[0021] To make the present invention more clear, a double-wire root-free MAG welding process method for thick-walled double V-grooves of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] A double-wire root-free MAG welding process for thick-walled double V grooves, characterized in that:

[0023] (1) Use mechanical processing or flame cutting to bevel the workpiece to be welded. According to the relevant standards, such as ASME standards, remove rust, oil and other contaminants near the positive and negative grooves of the workpiece to prevent affecting the formation and quality of the weld;

[0024] (2) Select welding materials that match the parent material, including dry, oil-free, and rust-free special welding wire, and conduct appropriate pre-welding inspections on the welding wire before welding, such as checking the factory warranty and the tightness of the welding wire reel before opening;

[0025] (3) Preheating before welding is required according to the characteristics of the parent material and related process requirements. Welding can only be carried out after the weldment reaches the preheating temperature, and the interlayer temperature must be strictly controlled. The assembled workpieces are clamped on the tooling, and the welding robot is equipped with a double-wire welding gun for welding;

[0026] (4) During the welding process, by observing the molten pool and post-weld formation, the welding parameters, swing width, etc. are adjusted and controlled in real time through the robot teaching pendant display screen to ensure weld formation and stable arc combustion;

[0027] (5) After welding, the weld undergoes quality inspections such as weld appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness test.

[0028] The actual welding is carried out according to the following steps:

[0029] 1. Welding equipment and materials:

[0030] (1) The welding equipment used is a welding power source that is matched with a welding robot, model is QINEO START 502, and the double-wire MAG welding gun is a CLOOS straight-shank double-wire water-cooled welding gun, which is used together with tooling fixture equipment.

[0031] (2) The base material of the welding material is D36, the workpiece specification is 1000×200×38mm, the yield strength is ≥355Mpa, and the tensile strength is 490-630Mpa; the gas shielded welding wire JQ·MG50S-6 with a wire diameter of Φ1.2mm is used.

[0032] 2. Preparation before welding:

[0033] (1) Bevel processing: Use a milling machine to open a double V-shaped bevel on the raw material, with a blunt edge of 2~3mm and a gap of 0~1mm. Be careful not to deform during the bevel processing and ensure that the misalignment is 0~1mm. Figure 1 shown.

[0034] (2) Cleaning: Use a grinder to clean rust, oil and other contaminants within 20 to 30 mm on both sides of the test plate groove.

[0035] (3) Butt assembly: imitate the use of tooling clamping assembly in actual welding to ensure accuracy.

[0036] (4) Preheating: Preheat to 80-90℃.

[0037] 3. Welding process:

[0038] (1) Welding position: 1G position.

[0039] (2) Welding gun position: The welding gun is perpendicular to the workpiece.

[0040] (3) Through real-time adjustment and control of welding parameters, multi-layer and multi-pass welding can be adopted, and the interlayer temperature is controlled at 100~150℃. The welding process parameters are shown in the following table.

[0041]

[0042] 4. Post-weld inspection: After weld appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness test, the inspection and test results show that the weld is well formed, there are no obvious macro welding defects such as lack of fusion, lack of penetration, undercut, etc. on the weld surface, the weld strength can match the strength of the parent material, and there are no micro welding defects such as pores, slag inclusions, cracks, etc.

[0043] The present invention is used in the technical field of welding process for thick-walled grooved workpieces. The process requires the workpiece to open a double V-shaped groove, the assembly gap is 0-1mm, the blunt edge is 2-3mm, and the misalignment is 0-1mm. Therefore, most plate workpieces are butt-jointed, and the grooves are mostly fine-machined or flame-cut, so the accuracy difference after assembly is relatively small. And because of the requirements of its use conditions, the deformation after welding should be small, so the welding filling amount is required to be small and the welding line energy input should be relatively small. Most of its parent materials are low-alloy steel. On the basis of comprehensive consideration of the deformation after welding and ensuring the welding quality, the interlayer temperature is controlled, and 80°C preheating treatment is performed before welding, so as to avoid cold cracks as much as possible. The core point is that SMAW or manual MAG was used before, and now single-side double-wire MAG automatic welding is used for double V grooves, and single-wire MAG is used for the other side to prime, and no grinding and root cleaning process is performed in the process, so the biggest difficulty is to ensure the quality of the primer on both sides of the double V groove and the good fusion of both sides of each layer of weld.

[0044] The welding process of the present invention solves the problem of low welding efficiency of long plate workpieces, saves labor costs, simplifies the process, is easy to operate and eliminates the probability of welding defects as much as possible, improves welding efficiency and reduces welding costs.

[0045] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A double-wire free-root-cleaning MAG welding process for thick-walled double V-grooves, the specific steps are as follows: Features: (1) Groove processing: Use mechanical processing or flame cutting to make double V-shaped grooves on the workpiece to be welded. The depth of the large groove on the front side ranges from 25mm to 100mm, the blunt edge is 2~3mm, and the assembly gap is 0~1mm. Be careful not to deform during the groove processing process and ensure that the misalignment is 0~1mm; (2) Welding material preparation: Select welding materials that match the parent material. The parent material of the welding material is D36, the workpiece specifications are 1000×200×38mm, the yield strength is ≥355Mpa, the tensile strength is 490~630Mpa, and the gas shielded welding wire JQ·MG50S-6 with a wire diameter of Φ1.2mm is used; (3) Workpiece preheating and clamping: Preheat the workpiece before welding according to the characteristics of the parent material and related process requirements to avoid cold cracks. Welding can only be carried out after the weldment reaches the preheating temperature. Strictly control the interlayer temperature. Clamp the assembled workpiece on the tooling. The welding robot is equipped with a double-wire welding gun for welding. The welding position is 1G, and the welding gun is perpendicular to the workpiece. (4) Double-wire welding: During the welding process, the molten pool and the post-weld formation are observed through the robot teaching pendant display screen. According to different narrow and deep grooves, with the assistance of the arc tracking function, the welding parameters, swing frequency, swing width, inductance parameters and arc length are adjusted and modified to ensure the weld formation and stable arc burning. After the welding of the small groove on the back side is completed, there is no need to grind and clean the root before welding the large groove on the front side. Direct welding can be carried out. Double-wire deep fusion welding is used when welding the base layer of the large groove on the front side. (5) Post-weld inspection: After welding, the weld is subjected to appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness tests. The weld is well formed, and there are no obvious macro welding defects such as lack of fusion, lack of penetration, undercut, etc. on the weld surface. The weld strength can match the strength of the parent material, and there are no micro welding defects such as pores, slag inclusions, cracks, etc. inside.

2. The double-wire free-root-cleaning MAG welding process for thick-walled double V-groove according to claim 1, Features: In the step (1), rust, oil stains and other contaminants within a range of 20 to 30 mm on both sides of the positive and negative grooves of the workpiece are polished away with a polishing machine.

3. The double-wire free-root-cleaning MAG welding process for thick-walled double V groove according to claim 1 or 2, Features: In the step (2), the welding wire is required to be dry, oil-free and rust-free, and the welding wire used is subjected to corresponding pre-welding inspections before welding, such as checking the factory warranty and the tightness inspection of the welding wire reel before opening.

4. The double-wire root-free MAG welding process for thick-walled double V groove according to claim 1 or 2, Features: In the step (3), the preheating temperature of the weldment is 80-90°C.

5. The double-wire root-free MAG welding process for thick-walled double V groove according to claim 1 or 2, Features: In the step (4), single-wire welding is adopted for the small groove side on the back side, and its backing welding process parameters are welding current 280-290A, arc voltage 31-32V, and wire feeding speed 12m / min. Double-wire welding is adopted for the large groove side on the front side, and its backing welding process parameters are welding current 356 / 218A, arc voltage 38V / 23V, welding speed 450mm / min, and wire feeding speed 12 / 8m / min respectively.

6. The double-wire free-root-cleaning MAG welding process for thick-walled double V groove according to claim 1 or 2, Features: In the step (4), when multi-layer and multi-pass welding is adopted, the interlayer temperature is controlled at 100-150°C.

7. The double-wire free-root-cleaning MAG welding process for thick-walled double V-groove according to claim 6, Features: In the step (4), the positive and negative grooves are both welded by MAG welding, the welding current polarity is DCEP, there are ten welding layers or welds in total, the first layer of base welding is welded by double wires, the welding current is (350~360) / (210~220)A, the arc voltage is 38 / 23V, the welding speed is 450mm / min, the minimum line energy is 24.2KJ / cm, and the maximum line energy is 25KJ / cm.

8. The double-wire free-root-cleaning MAG welding process for thick-walled double V-groove according to claim 6, Features: In the step (4), the second to seventh layers are filled with double wires, the welding current is (200-210) / (180-190) A, the arc voltage is 30 / 30 V, the welding speed is 400 mm / min, the minimum line energy is 17.1 KJ / cm and the maximum is 18 KJ / cm.

9. The double-wire free-root-cleaning MAG welding process for thick-walled double V-groove according to claim 6, Features: In the step (4), the eighth to tenth layers of cover are made of single wire, the welding current is 280-290A, the arc voltage is 31V, the welding speed is 350mm / min, the minimum line energy is 14.88KJ / cm and the maximum is 15.42KJ / cm.

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