Abstract:The step type critical region normalizing (STCRN) heat treatment process (HTP) was put forward as the center part of heavy cylinder was prone to mixed grain and crystal grain structure,long period of heat treatment,large energy consumption after the isotherm type austenite region normalizing (ITARN) process. The microstructure and mechanical properties after the proposed HTP methods were verified,and the two times STCRN was the best HTP. The results show that: First,the two- time STCRN on eliminating mixed grain and crystal grain is better than that with ITARN method,and the average grain size is 18um after the heat treatment. Also,the cementite spheroidization and homogenization inside the grain is more effective. Besides,the yield strength,tensile strength and the-30 ℃ charpy impact energy of the heavy cylinder material are 681 MPa,768 MPa and 181 J,respectively after two- time STCRN HTP,and the comprehensive mechanical properties are better than that with the ITARN method. Furthermore,the -30 ℃ impact fracture after the two- time STCRN is quasi- cleavage fracture,with significantly more plastic ridge and larger low temperature impact absorbing energy than that with ITARN. Finally,compared with the ITARN,the holding time of two- time STCRN can be shortened by 30% and the normalizing temperature is also decreased,which greatly reduces the energy consumption.
孙建亮,张永振,彭艳,戚向东,郝露菡. 大型筒节台阶式临界区正火热处理工艺[J]. 钢铁, 2015, 50(8): 65-70.
SUN Jian- liang,ZHANG Yong- zhen,PENG Yan,QI Xiang- dong,HAO Lu- han. Step type critical region normalizing heat treatment process of heavy cylinder. Iron and Steel, 2015, 50(8): 65-70.
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