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Formation of weld heat affected zone on welded steel pipes
- Dec 13, 2017 -

Welding is a local rapid heating and cooling process of the heat cycle on welded steel pipes, the heating process causes the metal to melt rapidly into the weld area, and the parent material close to the weld part is subjected to a special thermal cycling effect, which changes the microstructure, which is called the Heat effect zone (Heat Affected Zone, abbreviated HAZ).

In the heat affected zone, the distance from the center of the weld is different, different parts of the heat cycle process is also different, that is, the weld center of the heating speed, peak temperature, heat preservation time, cooling speed is different, so that the region of the different locations of the parent material has undergone different phase change, the different tissues affected the performance of the region, The peak temperature and cooling speed are the most important.

In welding practice, according to the thermal cycle curves measured at different test points from the center of Weld, the results show that the weld heat affected zone is occured due to the local rapid heating in different position and the solid phase transition of different content, in which the performance of the coarse grain region is the most changeable. The study of microstructure and properties of thermal effect mainly refers to the coarse-grained zone with thermal effect, HAZ is abbreviated to coarse-grained.