Abstract : According to the structural characteristics of large insulated door panels and the technical requirements for thin plate joint welding, the welding parameters of the automatic TIG welding of stainless steel sheets are determined by welding test, and the welding equipment controlled by microcomputer is used. And the bad copper padding strictly controls post-weld deformation. This process is used in production and fully meets the product design requirements.

Key words : automatic TIC welding; stainless steel sheet; tailor welding process

CLC number : TG444.74

Document ID: B

In the trial production process of the large-size heat-insulating door panel of the H6645B fiber dryer main door, our factory encountered the problem of seam welding of any 0. 8MM thick 0Cr18Ni9 stainless steel sheet. The structure and expansion diagram of the large-size heat-insulated door panel of the main gate are shown in the figure. 1, Figure 2.

The design requires that the large heat-insulating door be made of 0. 8mm thick 0Cr18Ni9 material. The front side of the panel is not allowed to be welded, and the surface of the weld must be free of dents after the side seam welding. No undercut, smooth and smooth, and no wave deformation defects occur after the entire panel is welded. Due to the small size of the large insulated door panel and large area (3046mm*1352mm*0. 8mm), due to the limitation of the sheet material, two splicing welds must be designed on the panel, as shown in Figure 2. Therefore, in the welding process, not only the welding quality of the long weld of the stainless steel sheet but also the deformation of the panel after welding should be controlled. Considering that the automatic TIG welding process has the advantages of single-sided welding double-sided forming, good weld quality, small deformation after welding, high welding efficiency, etc., it is especially suitable for the welding of long-weld seams of stainless steel sheets, and it is decided to adopt automatic TIG welding single-sided welding double The surface forming process solves the problem of tailor welding of 0. 8mm thick 0Cr18Ni9 thin plate.

1 Test purpose

Through the automatic TIG welding single-sided welding double-sided forming process test of 0. 8mm thick 0Cr18Ni9 thin plate, reasonable welding process parameters are determined; appropriate welding process measures are taken to obtain high-quality welds that can meet the design requirements.

2 welding process test

2.1 Welding equipment The welding equipment is selected by ARISTO-500 computer-controlled universal welding machine. It has storage program and memory welding, and can adjust the optimization of welding parameters while welding. It is also equipped with a pneumatic piano-type clamp and a copper pad with a bad copper to obtain high-quality welds and control the deformation of the thin plate after welding.

2.2 Preparation before welding In the special number control cutting bed, the material is prepared. 0. 8mm thick 0Cr18Ni9 test piece 200mm * 3050mm several pieces, try to make the cutting mouth straight, no burrs, curling and other defects, first use manual TIG welding method Two pieces of test piece are spot welded into a welded test plate (one spot is welded every 100mm, the wire number is HOCr21Ni10, the diameter is 1. 2mm), then the spot weld is leveled with a wooden hoe, and the oil to be welded is treated with acetone solution. Wipe clean, and finally press the welding test plate on the grooved copper pad with the pneumatic keyboard type clamp. As shown in Figure 3, the welding parameters can be adjusted before welding.

2 .3 welding process parameter selection

2 .3 .1 Welding current and tungsten diameter selection After many tests, it is proved that when the tungsten electrode diameter is 1.6mm and the welding current is greater than 60A, the molten pool is easily burnt, and even the partial butt gap of the test plate is too large. Raw burn through defects. If a burn-through defect occurs, it is difficult to repair the weld. Secondly, even if the manual TIG repair welding effect is good, a large wave deformation will occur: when the welding current is less than 50A, the back surface is prone to incomplete penetration defects, and the single defect is not achieved. The effect of double-sided forming of face welding. Therefore, the welding current selection of 50-60A is more suitable.

2 .3 . 2 argon flow rate and nozzle diameter According to the data, under certain conditions, the argon gas flow rate and the nozzle diameter have a better matching range during TIG welding. At this time, the argon gas protection effect is the best, that is, when the nozzle When the diameter is constant, the argon gas protection flow rate is too low, the air flow stiffness is poor, the ability to exclude the surrounding air is low, and the protection effect is not good; the argon gas flow rate is too large, which is easy to cause turbulence, so that the outside air is involved, and the protection effect is also reduced. The test proves that when the nozzle diameter is 10mm and the argon flow rate is 8-10L/Min, the argon gas protection effect is better. In addition, the flow rate of the back protective gas should also be suitable, the flow rate is too small, and the protection effect is not obtained; if the flow rate is too large, not only the gas is wasted, but also the back weld is concave, and the back protective gas flow is selected during the actual welding. 6L/mm.

2.3.3 Welding speed During the welding process, the welding speed is inversely proportional to the welding heat input under certain welding current conditions. When the welding speed is too large, the welding heat input is small, and it is easy to produce incomplete penetration. Defects such as undercuts do not achieve the effect of double-sided welding on both sides; when the welding speed is too small, the welding heat input is large, which may cause the weld pool to burn. Even burned through. Therefore, the welding speed must have a suitable range. The test shows that when the welding current is 50-60A, the welding speed is preferably 0.60-0.65m/min.

2.3.4 Platen spacing The platen spacing is related to the thickness of the stainless steel. The thinner the plate is, the smaller the spacing between the plates is. If the spacing between the plates is too large, the plate will be deformed during the welding process, which will easily cause burn-through defects, but the platen spacing should not be too small. Otherwise, the nozzle can not be close to the molten pool, which will make the argon gas protection effect worse. After many tests, the welding effect is better when the pressure plate type clamp clamp plate spacing is adjusted to 11-12mm.

After repeated welding process tests, the automatic TIG welding double-sided welding process parameters are shown in Table 1. According to the welding process parameters given in the table, a plurality of welding test plates are welded, and the appearance quality is checked. Claim.

3 production applications

The automatic TIG welding single-sided double-sided forming welding process has been applied to the test process of the large-scale heat-insulating door panel of the main part of our H6645B fiber dryer, which better solves the problem of tailor welding of 0Cr18Ni9 thin plate. The surface of the weld has no undercut, no dent, smooth and smooth, and the deformation of the panel is small, which fully meets the design requirements, thus ensuring the successful completion of the trial production of the H6645B fiber dryer.

4 Conclusion
The automatic TIG welding single-sided welding double-sided forming welding process can better solve the problem of tailor welding of 0. 8mm thick 0Cr18Ni9 thin plate, not only can obtain high-quality weld seam, but also can well control post-weld deformation.

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