By adopting the ferrite tester, the precipitation regularity of ferrite of 316 LN stainless steel with different heating temperatures and cooling rates has been researched. The results show that there is no ferrite to precipitate when the heating temperature is below 1280℃, or when the cooling rate is above 20℃/h. Based on the physical and chemical testing and combined with the heat treatment process test, the cause for appearing no bottom ware during the ultrasonic test of 316 LN stainless steel forgings and the improving method have been analyzed. The results indicate that the cause for appearing no bottom ware is the serious mixed crystal. And the difference between grain sizes can be reduced by means of heat treatment, so as to improve the detectability of ultrasonic wave. The results of the mechanical property test at ambient temperature and high temperature and the intercrystalline corrosion property test after the solution treatment with different temperatures show that the mechanical property of 316 LN stainless steel has slightly fluctuated when the grade of grain size varies in the range of 4.0 and 1.0. At this time, the intercrystalline corrosion property can meet the requirements. During the solution treatment with same temperature, the number of times of heat treatment has less influence on the grain size and the mechanical property, in order to make the intercrystalline corrosion property meet the requirements of specifications.
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