When the stainless steel elbow processing, whether heating or cooling, they are not consistent because the cooling rate and the time of its surface and the formation of the temperature difference. This will cause the volume expansion and contraction caused stress, called thermal stress.
Stainless steel elbow
Stainless steel elbow under the action of thermal stress, the surface temperature will be lower than the heart, when the end of the cooling shrinkage, not free heart finally cooling, and the surface tension of heart compression. Under the action of thermal stress, the workpiece surface pressure and the heart of tension.
Thus causes this kind of phenomenon is due to the influence of cooling rate, material composition and heat treatment process.
Stainless steel elbow high frequency welding is the use of the alternating current trend skin effect and proximity effect, when the steel after rolling forming, forming a section break open the round tube blank, when the tube billet near the center of the induction coil near impedor, impedance and tube formed at the opening of an electromagnetic induction loop.
In the trend of the skin effect and proximity effect, blank opening edges will produce powerful and concentrated heat effect, and the edge of the weld is rapidly heated, reach the required welding temperature in the roll extrusion, the molten metal to achieve intergranular bonding, cooling after forming a firm butt weld.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)