A double-wire long-drawn MAG welding process

Abstract

The invention discloses a double-wire large dry extension MAG welding process, which relates to the technical field of thick-walled narrow deep groove type workpiece welding. In a narrow groove with a depth of 30-40 mm or a dry extension of 35-40 mm, by adjusting and controlling the welding position, welding parameters, swing width, etc., the preheating temperature before welding, the interlayer temperature and the heat input are strictly controlled according to the project and process requirements, the probability of the occurrence of pores can be greatly reduced, and the welding process is stable, and there will be no phenomenon affecting welding such as wire frying.

Description

Technical Field

[0001] The invention relates to the technical field of thick-walled narrow-deep groove workpiece welding, in particular to a double-wire large-drawout MAG welding process. Background Art

[0002] Oil cylinders are widely used in the engineering machinery industry. Their main material is heat-resistant steel, which is required to have high high-temperature strength and good chemical stability at high temperatures. Oil cylinder workpieces are mostly butt-jointed (in the form of root plug-in), and the grooves are mostly fine-machined, so the accuracy difference after assembly is very small. Due to the requirements of its use conditions, the deformation after welding should be small, so the welding filling amount should be small, and its parent material is mostly heat-resistant steel. At present, SMAW is used for the welding of such workpieces. When manual welding is used to fill the cover, the welding workload is large, the quality control requirements are high, the welding efficiency is low, and the cost is high. Summary of the invention

[0003] The present invention aims at solving the above technical problems, overcomes the shortcomings of the prior art, and provides a double-wire large-length extension MAG welding process, comprising:

[0004] (1) Use mechanical processing to bend the workpiece to be welded, and remove rust and oil stains near the groove of the workpiece according to the relevant standards;

[0005] (2) Select welding materials that match the parent material, dry, oil-free, and rust-free special welding wire, and conduct appropriate pre-welding inspection on the welding wire before welding;

[0006] (3) Preheating is performed before welding 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 is strictly controlled; the assembled workpieces are clamped on the positioner or tooling, and the welding robot is equipped with a double-wire welding gun for welding;

[0007] (4) During the welding process, the process parameters are adjusted and controlled in real time by observing the display screen of the robot teaching pendant to ensure the weld formation and stable arc combustion;

[0008] (5) After welding, the weld is inspected by appearance, X-ray, ultrasonic, tensile strength and impact toughness tests;

[0009] The dry extension length is 35-40mm, and the base welding process parameters are: welding current 260-280A, arc voltage 30-32V, welding speed 350-400mm / min, the front wire feeding speed of the double-wire welding gun is 12m / min, and the rear wire feeding speed of the double-wire welding gun is 10m / min.

[0010] The technical solution further defined in the present invention is:

[0011] In the aforementioned double-wire extended-draw MAG welding process, during the welding process, the welding parameters, oscillation frequency, oscillation width, inductance parameters and arc length adjustment are modified with the assistance of the arc tracking function according to different narrow and deep grooves.

[0012] The aforementioned double-wire large-drawout MAG welding process is suitable for narrow and deep groove workpieces with a groove depth ranging from 30 to 40 mm.

[0013] The aforementioned double-wire long-draw-out MAG welding process has a pair gap of 0-1 mm, a blunt edge of 3-4 mm, and an offset of 0-1 mm.

[0014] In the aforementioned double-wire long-draw-out MAG welding process, the interlayer temperature is controlled at 200-250°C, and a preheating treatment of 100-150°C is performed before welding.

[0015] The beneficial effects of the present invention are:

[0016] The present invention can ensure the welding stability and post-welding quality of the base weld in the weld with thick wall and narrow deep groove, and basically will not have welding defects such as pores or lack of fusion on both sides caused by insufficient protection of the shielding gas. The weld formation quality is good, the weld and the parent material have a smooth transition, and there are no defects such as cracks, pores, slag inclusions, and incomplete penetration on the surface. It can eliminate the base and root cleaning processes, simplify the process, improve welding efficiency, and ensure welding quality.

[0017] In the process of long-extended double-wire MAG welding, because the extended length is far beyond the commonly used length, it will normally cause poor arc starting, wire bursting, porosity and other adverse factors affecting welding. However, by changing the fine-tuning parameters of the voltage in the welding power supply, the inductance parameters that play a decisive role in the softness and hardness of the welding arc, and appropriately increasing the pre-gas supply and post-gas supply time before arc starting, the above adverse factors are avoided, ensuring the stability of the welding arc and the formation of the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the groove assembly of the present invention. Implementation

[0019] This embodiment provides a double-wire extended-length MAG welding process as follows:

[0020] 1. Welding equipment and materials

[0021] (1) The welding equipment used is a welding power source that is matched with a welding robot, model is QINEO START 502, the double-wire MAG welding gun is a CLOOS straight-shank double-wire water-cooled welding gun, and a positioner and tooling fixture equipment are used together.

[0022] (2) The base material of the welding material is 1Cr6Si2Mo, the workpiece specifications are φ200×150×45mm, the yield strength is 550MPa, and the tensile strength is 685MPa; the gas shielded welding wire ER55-G with a wire diameter of Φ1.2mm is used.

[0023] 2. Preparation before welding

[0024] (1) Bevel processing: Use a lathe to make a U-shaped bevel on the raw material, with a blunt edge of 3-4mm and a gap of 0-1mm. Be careful not to deform during the bevel processing and ensure that the misalignment is ≤1mm. Figure 1 shown.

[0025] (2) Cleaning: Use a grinder to clean rust, oil and other contaminants within 20-30 mm on both sides of the test plate groove.

[0026] (3) Butt assembly: imitate the use of tooling clamping assembly in actual welding to ensure accuracy.

[0027] (4) Preheating: Preheat to 100-150℃.

[0028] 3. Welding process

[0029] (1) Welding position: 1G position.

[0030] (2) Welding gun position: The welding gun is at 12 o'clock and the workpiece rotates counterclockwise.

[0031] (3) Through real-time adjustment and control of welding position, welding parameters, etc., multi-layer and multi-pass welding can be adopted, and the interlayer temperature is controlled at 200-250℃. The welding process parameters are shown in Table 1.

[0032] Table 1 Welding parameters

[0033]

[0034] 4. Post-weld inspection

[0035] After weld appearance inspection, X-ray inspection, ultrasonic inspection, tensile strength and impact toughness tests, the inspection and test results show that the weld is well formed, there are no obvious macro welding defects such as lack of fusion, incomplete 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.

[0036] Normal MAG welding is extremely unstable at this dry extension length (40mm). In addition to the influence of welding power supply and gas protection on the welding process, there is also the situation of rotating wire feeding in the coiled wire, which causes the arc to disperse and not burn in the predetermined position. Therefore, adding a wire straightener after the wire feeder can minimize the impact of this factor.

[0037] Through the above welding process, on the basis of obtaining higher welding quality, the welding wire is fully melted under the action of arc heat during the welding process, and at the same time, welding defects caused by base welding and operation can be eliminated, welding efficiency can be improved, the operation process can be simplified, the deposition efficiency is high, and the effect of efficient welding can be achieved. It solves the problems of large welding workload, high quality control requirements, low welding efficiency and high cost when using SMAW for base and manual gas shielded welding for filling and covering. The base effect is 3-4 times higher than the base efficiency of the normal SMAW process. The filling and covering effects are 2-3 times more efficient than manual gas shielded welding due to the effects of parameters such as high wire feeding speed, large welding current and fast welding speed.

[0038] 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 extended-length MAG welding process, characterized in that: Suitable for narrow and deep groove workpieces with groove depth ranging from 30-40mm, including: (1) Use mechanical processing to bend the workpiece to be welded, and remove rust and oil stains near the groove of the workpiece according to the relevant standards; (2) Select welding materials that match the parent material, dry, oil-free, and rust-free special welding wire, and conduct appropriate pre-welding inspection on the welding wire before welding; (3) Preheating is performed before welding 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 is strictly controlled; the assembled workpieces are clamped on the positioner or tooling, and the welding robot is equipped with a double-wire welding gun for welding; (4) During the welding process, the process parameters are adjusted and controlled in real time by observing the display screen of the robot teaching pendant to ensure the weld formation and stable arc combustion; (5) After welding, the weld is inspected by appearance, X-ray, ultrasonic, tensile strength and impact toughness tests; The dry extension length is 35-40mm, and the bottom welding process parameters are: welding current 260-280A, arc voltage 30-32V, welding speed 350-400mm / min, the front wire feeding speed of the double-wire welding gun is 12m / min, and the rear wire feeding speed of the double-wire welding gun is 10m / min; The gap between the pairs is 0-1mm, the blunt edge is 3-4mm, and the misalignment is 0-1mm; The interlayer temperature should be controlled at 200-250℃, and preheating treatment at 100-150℃ should be performed before welding.

2. A double-wire extended-length MAG welding process according to claim 1, characterized in that: During the welding process, 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 adjustment are modified.

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