Because one of the main parameters of the erw steel pipe welding process, that is, the welding current (or welding temperature) is difficult to measure, it is replaced by input heat, which can be expressed by the oscillator output power:
N = Ep·Ip
When the oscillator, inductor, and resistor are determined, the efficiency of the oscillating tube channel, output transformer, and inductor is determined, and the change in input power is roughly proportional to the change in input heat.
When the input heat is insufficient, the heated edge does not reach the soldering temperature, and the solid structure is still not welded, forming a solder joint crack; when the input heat is large, the heated edge exceeds the soldering temperature, which is likely to cause overheating or even overheating. Cracking occurs after the force; when the input heat is too large, the welding temperature is too high, causing the weld to break down, causing the molten metal to splash and form a hole. The melting welding temperature is generally from 1350 to 1400 ° C.
The welding pressure is one of the main parameters of the welding process. After the two edges of the tube blank are heated to the welding temperature, a common metal grain is formed under the action of the pressing force, that is, crystallizing each other to produce welding. Different from the seamless steel pipe,the size of the welding pressure affects the strength and toughness of the weld. If the applied welding pressure is small, the metal welding edge can not be fully pressed, and the non-metallic inclusions and metal oxide remaining in the weld are not easily discharged due to the small pressure, the weld strength is lowered, and the crack is easy to be cracked after being stressed;.
The pressure is too large at the time, most of the metal that reaches the soldering temperature is extruded, which not only reduces the weld strength, but also causes defects such as excessive internal or external burrs or lap welding. Therefore, the optimum welding pressure should be obtained in practice according to different specifications. According to practical experience, the unit welding pressure is generally 20~40MPa.
Due to the possible tolerances of the tube blank width and thickness, as well as fluctuations in the welding temperature and welding speed, it is possible to involve changes in the welding extrusion force. The amount of welding extrusion is generally controlled by adjusting the distance between the pressing rolls, or by the circumferential difference between the front and rear of the pressing rolls.