ERW welding seam process
Forming nature of seam welding and spot welding on the same head, thereby affecting the quality of welding such factor is similar. The main welding current, electrode force, welding time, rest time, the welding speed and the diameter of the roulette and the like.
1, the welding current
Seam weld nugget same amount of heat required to form the source and spot welding, is the use of the heat current through the weld zone resistor. Under other conditions given situation, the size of the welding current determines the penetration rate and the amount of overlap of the nugget. When welding mild steel, the average penetration rate nugget plate thickness of 30-70% to 45-50% for the best. In order to obtain the airtight seam weld nugget overlap amount of not less than 15-20%. When the welding current exceeds a certain value, continue to increase the current can only increase the rate of penetration and the amount of overlap of the nugget without increasing the strength of the joint, which is not economical. If the current is too big, too deep indentation will burn and welding defects. Since the weld nugget overlap each other and cause a large diversion, and therefore, the welding current is usually increased 15-40% compared to the spot welding.
2, electrode force
Electrode pressure consistent impact on nugget size and spot welding seam welding. Electrode pressure is too high too deep indentation, and it will accelerate the loss of deformation and roll disc. Insufficient pressure is prone to shrinkage, and due to the contact resistance is too easy to make a large roll disc burning and shorten its life.
3, welding time and rest time
When the seam welding, the main welding time by controlling the size of the nugget, by the cooling time control the amount of overlap. At lower welding speed than the welding and ending time of 1.25: 1-2: 1, will be satisfied with the results. When increasing welding speed, spot pitch increases, this time to get the same amount of overlap welds must be increased ratio. For this reason, at higher welding speed, welding and than the rest time of 3: 1 or higher.
4, welding speed
Welding speed and the welded metal, plate thickness, and the weld strength and quality requirements and so on. Usually in the welding of stainless steel, high temperature alloys and non-ferrous metals, in order to avoid splashing and to obtain a dense high weld must be lower welding speed. Sometimes stepping seam welding, a nugget is formed so that the whole process were carried out under the roulette stops. This seam welding welding speeds than conventional intermittent seam welding is much lower. Welding speed determines the roulette plate member with the contact area and the contact time with the heated portions of the roller tray, thus affecting the heating and cooling of the joint. When the welding speed increases, in order to obtain sufficient heat, necessary to increase the welding current. Excessive welding speed can cause burning and the electrode plate surface adhesion, even if the external water cooling, the welding speed should be limited.