超碰在线人人_jizz18女人高潮_国产主播在线一区_福利视频网_亚洲97色_同人本子_男人操女人动态图_香蕉视频国产精品_日韩欧美亚_欧洲成人一区二区_一区二区伦理片_久久久久久国产精品日本_国产又粗又长又黄的视频_日韩一区二区三区在线观看_中文精品在线

Stainless steel head in the heating and cooling process, the cooling rate is inconsistent surface and center and time, forming temperature, resulting in volume expansion and contraction of the uneven stress that the heat stress. Stainless steel head under the effect of thermal stress due to a temperature below the surface began to core section, leaving the central portion is greater than the contraction also central portion tension, when the end of the cooling, since the cooling core section final volume shrinkage can not freely leaving the surface layer by Ministry press center of tension. That is under the influence of thermal stress and finally to the workpiece surface pressure and heart Ministry tension. This phenomenon is cooled velocity, material composition and heat treatment and other factors.

 

When cooled, the faster, the higher the carbon content and alloy composition, inhomogeneous plastic deformation of the cooling process in the thermal stress generated by the larger, the final form of the residual stress is greater.

On the other hand the steel during heat treatment due to the change in the organization that is the transformation of austenite to martensite, accompanied by the increase of the specific volume of the volume expansion of the workpiece, the various parts of the workpiece has a phase change, resulting in inconsistency of the volume of tissue grown stress.

 

The end result stainless steel head the surface tissue stress is tensile stress, the heart portion compressive stress, and thermal stress exactly the opposite. The stress in the workpiece size and cooling rate of martensite transformation zone factor, shape, chemical composition of the material.