A bonded portion formed by welding a steel structural member, component or panel.
Seam welding is a welding method in which a pair of roller electrodes are used instead of spot-welded cylindrical electrodes to move relative to the workpiece to produce a sealed weld seam in which nuggets overlap each other.
The weldment is assembled into a lap joint or butt joint and placed between the two roller electrodes. The roller pressurizes the weldment and rotates to continuously or intermittently transmit electricity to form a continuous weld joint resistance welding method.
Seam welding is widely used in oil drums, cans, radiators, aircraft and automotive fuel tanks, as well as thin-plate welding of sealed containers in jet engines, rockets and missiles.
Welding tools The electrodes for seam welding are round rollers. The diameter of the rollers is generally 50-600 mm, and the usual diameter is 180-250 mm. The thickness of the roller is 10-20mm. The shape of the contact surface is cylindrical or spherical, and in some cases a conical surface is used (Fig. 12-1). In addition to the form of double-sided chamfering, the cylindrical rolling plate can also be formed into a single-measuring chamfer to accommodate the seam welding of the crimped joint. The contact surface width ω is 3-10 mm depending on the thickness of the workpiece, and the spherical radius R is 25-200 mm. Cylindrical rolling discs are widely used for welding various steels and high-temperature alloys. Spherical rolling discs are often used for light alloy welding because of their easy heat dissipation and uniform indentation transition. The scroll is usually cooled externally. When welding non-ferrous metals and stainless steel "target=_blank> stainless steel, use clean tap water. When welding ordinary steel, in order to prevent rust, it is usually cooled by an aqueous solution containing 5% borax. The rolling plate is sometimes cooled by internal circulating water, especially It is a welder for welding aluminum alloys, but its construction is much more complicated.
Seam welding method According to the rotation of the roller and the feeding mode, the seam welding can be divided into continuous seam welding, intermittent seam welding and step seam welding.
Continuous seam welding
The roller rotates continuously and the current continuously passes through the workpiece. This method tends to overheat the surface of the workpiece, and the electrode is worn out so that it is rarely used. However, at the high-speed seam welding (4-15m/min), a solder joint is formed every half cycle of the 50Hz alternating current, and the alternating current zero-crossing corresponds to the rest time, which is similar to the intermittent seam welding described below, thus forming the cylinder, Applicable in the barrel industry.
Intermittent seam welding
The scroll rotates continuously, the current is intermittently passed through the workpiece, and the formed weld is composed of nuggets that overlap each other. Since the current is intermittently passed, the reel and the workpiece are cooled during the rest time, thereby improving the life of the reel, reducing the width of the heat-affected zone and the deformation of the workpiece, and obtaining superior welding quality. This method has been widely used for seam welding of various steels, superalloys and titanium alloys of less than 1.5 mm. In intermittent seam welding, since the roller continuously leaves the weld zone, the nugget crystallizes under reduced pressure, so surface overheating, shrinkage and cracking (such as when welding high temperature alloys) are easily generated. Although the molten metal at the latter point can fill the shrinkage hole of the previous point when the solder joint overlap exceeds 50% of the length of the nugget, the final shrinkage hole is difficult to avoid. However, the microcomputer control box developed in China can solve the problem by reducing the welding current point by point at the end of the weld.
Step seam welding
The rolling wheel rotates intermittently, and the current passes through the workpiece when the workpiece is not moving. Since the melting and crystallization of the metal are performed while the rolling plate is not moving, the heat dissipation and the pressing condition are improved, so that the welding quality can be more effectively improved and the rolling plate can be extended. life. This method is more than seam welding of aluminum and magnesium alloys. It is also used for seam welding of high-temperature alloys, which can also effectively improve the quality of welding. However, this type of AC welding machine is rare in the country and has not been applied. When welding hard aluminum. As well as various metals with a thickness of 4+4mm or more, step seam welding must be used, so that for each solder joint, forging pressure can be applied like spot welding, or both warm and cold pulses can be used. But the latter case is rarely used.
Weld classification 1. Flat weld 2. Fillet weld 3. Ship weld 4. Single weld 5. Single weld double weld
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