Why should steel pipes be heat-treated
In the heating and cooling process of steel pipe, because of the inconsistent cooling rate and time period between the surface and the core, the temperature difference will cause the uneven expansion and closure of the body and the ground stress, that is, the internal stress. Under the effect of internal stress, because the surface temperature is gradually lower than the heart, the closing is also higher than the core, so that the heart is strained. When the cooling is completed, because the final closing of the cooling volume of the heart cannot be carried out freely, the surface force of the heart is strained. That is, under the effect of internal stress, the workpiece surface is stressed and the core is strained. These are now subject to factors such as cooling rate, chemical composition of raw materials and heat treatment.
The faster the cooling rate, the higher the carbon content and the material composition of the steel tube, the larger the asymmetrical plastic deformation under the effect of the internal stress in the whole process of refrigeration, and the larger the resulting internal stress. On the other hand, when the structure of steel changes from ferrite to austenite in the heat treatment process, the increase of vaporization heat will increase with the volume of the product, and the positions of the product parts will change in turn, resulting in inconsistent volume growth and resulting in the ground stress of the mechanism. The result of the transformation of mechanical ground stress ****** is that the surface tensile stress and the heart stress are the reverse of the internal stress. The stress of the mechanism is related to the cooling rate, appearance and raw material composition of the steel tube in the austenitic changing zone.
1. Improve the compressive strength, strength, surface wear resistance and corrosion resistance of the steel pipe.
