Thermal fatigue crack on spiral welded pipe,Technology

 The stability of spiral welded pipe thermal fatigue generally refers to the work in the cold, heat alternating the role of the ability to resist cracks, which is called thermal fatigue crack due to cold, heat alternating crack said. Limit of weld conditions. Ideally, the steel pipe weld for a parameter fixed spiral, but in the pipe welding process sometimes go awry, causing the steel pipe weld geometry parameters change, thus requiring the testing equipment to compensate for this kind of change.

When the metal material in the course of their work when the temperature difference, because part of the expansion, shrinking mutual constraints and generate additional heat stress. If the temperature cycle, thermal stress will also change with, accompanied by the circulation of the elastic and plastic deformation, plastic deformation gradually accumulated caused injury, leading to rupture. This destruction withstand and repeatedly periodic thermal stress was known as the thermal fatigue damage. Thermal fatigue crack generally occurs in the surface of metal parts for cracks like. Boiler superheater, reheater, steam drums, steam turbine cylinder, bulkhead, there is the possibility of thermal fatigue.

For the die steel, the thermal fatigue stability determines the toughness and strength of steel. Therefore, thermal fatigue and good stability mold steel must have a good co-ordination of good toughness and high strength (wet strength).