1. The circular pipe welded by steel plate is divided into high frequency resistance welded pipe (ERW welded pipe) and straight seam arc welded pipe (LSAW), spiral welded pipｅ（ＳＳＡＷ）
2、In electrical engineering, it can be expressed as "SC", it can be used as water gas pipe and can be used as piercing pipe, which is thicker.
3. ERW pipe is a "high frequency resistance welded steel pipe", which is different from common welded pipe welding technology. The weldｉｎｇｌｉｎｅ is formed by melting the base material of the steel strip body, the mechanical strength is better than that of the common welded pipe.
4. ERW indicates that resistance welding has the advantages of high production efficiency, low cost, low material saving and easy automation, so it is widely used in various industrial sectors, such as aviation, aerospace, energy, electronics, automobile, light industry, etc.
The high temperature welding process of ERW steel pipe caused the temperature gradient near the edge of the tube, and formed the melting zone, semi melting zone, overheating structure, normalizing zone, incomplete normalizing zone and tempering zone. In the superheated zone, the austenite grains grow sharply due to the welding temperature above 1000 degrees. Under the cooling condition, the hard and brittle coarse crystalline phases are formed, and the welding stress is produced in the presence of temperature gradient. In this way, the mechanical property of the weld area is lower than that of the base metal.
The physical seamlessly is heating the weld area to AC3 (927 degrees C) by conventional heat treatment process of the weld line, that is, using the intermediate frequency induction heating device, and then carrying out the air cooling process of 60m length and speed at 20m/, and water cooling when necessary. Thｉｓ method has achieved the goal of eliminating stress, softening and refining microstructure and improving the comprehensive mechanical properties of welding heat affected zone.
The quality of ERW steel pipe is not only unable to identify the weld, and the weld coefficient reaches 1, which realizes the matching between the weld area and the base metal.
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