婷婷麻豆_青青草国产成人99久久_国产一级性生活片_日本特级黄色_日韩中文字幕在线一区_成人午夜sm精品久久久久久久_日韩黄色精品视频_亚洲色婷婷一区二区三区_影音先锋亚洲一区_又污又黄又爽的网站_少妇太紧太爽又黄又硬又爽小说_一区二区不卡av_又白又嫩毛又多15p_免费三片在线观看网站v888_午夜影院18

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.