热处理对Q235钢微结构演变及疲劳性能的影响

Effect of Annealing Temperature on Microstructure Evolution and Fatigue Performance of Q235

通过在不同温度下对Q235钢进行退火处理,研究其微结构的变化及对疲劳性能的影响,分析不同退火温度下材料损伤变量与塑性应变之间的关系.研究结果表明:不同退火温度对疲劳后材料的力学性能有不同的影响:退火温度较低试样和未退火试样力学性能相差不大;当退火温度升高以后,抗拉强度降低,延性升高,韧性升高;屈服强度下降,疲劳寿命也随之降低,当达到材料的临界温度(300℃)疲劳寿命又随之升高.引入损伤形状因子,研究了不同退火温度下材料的微结构演变.100℃退火试样和初始试样的损伤形状因子变化趋势相似,初始损伤阶段增长较300℃退火试样增长明显,超过损伤临界点后增长较为迅速.而退火温度较高时,材料初始损伤阶段增长较为平缓,超过损伤临界点后损伤因子迅速增大.

The Q235 steel was annealed at different temperatures to study the changes in microstructure and the effect on fatigue performance.The relationship between the damage variables and plastic strain at different annealing temperatures was analyzed.The results show that different annealing temperatures have different effects on the mechanical properties of fatigued materials.There is little difference in mechanical properties between low annealing temperature samples and unannealed ones.When the annealing temperature increases,the tensile strength decreases while the ductility and the toughness increase.As the yield strength decreases,the fatigue life also decreases.When the critical temperature（300℃）of the material is reached,the fatigue life increases.In this paper,the damage shape factor was introduced to study the microstructure evolution of materials at different annealing temperatures.The change trends of the damage shape factor are similar in the annealed samples at100℃ and the initial samples.Compared to the growth of annealed samples at 300℃,it is more obvious in initial damage stage,and it increases more rapidly after exceeding the damage critical point.