Dynamic Recrystallization Behavior and Microstructure Evolution of AISI 304N Stainless Steel

Dynamic recrystallization of 304N stainless steel was investigated at deformation temperatures of 900- 1 300 ℃ and strain rates of 0.01 10 s by a Gleeble-1500 thermo-mechanical simulator. And the microstructure evolu lions of specimens with different deformation temperatures were observed by using a transmission electron micro scope. Results indicated that compared with conventional AISI 304 austenitie stainless steel, 304N stainless steel has higher deformation resistance force and deformation activation energy under similar conditions. In addition, the flow stress constitutive equation of 304N stainless steel was obtained by regression analysis of experimental stress strain data, and the calculated values proposed by the mathematical model agree well with the experimental results.

SiCa和SiCaBa合金对304N不锈钢脱氧和夹杂物变性的影响

通过实验研究SiCa(Si71%-Ca28%)和SiCaBa(Si52%-Ca14%-Ba14%-Al1.82%)合金对304N不锈钢脱氧和夹杂物改性及总氧含量的影响。加入SiCa或SiCaBa合金后,夹杂物中MnO消失,并改性为CaO-Al_(2)O_(3)-SiO_(2)-MgO-(BaO)体系,塑性增强。SiCa处理相比于无脱氧剂处理,夹杂物数密度由350个/mm2降低至170个/mm2,尺寸由0.8μm增加至2.7μm,面积占比为0.05%,但全氧含量并未明显降低。SiCaBa合金处理后夹杂物熔点进一步降低,塑性进一步增强。夹杂物数密度降低至155个/mm^(2),尺寸增加至3μm,面积占比为0.049%。全氧含量进一步降低,由111×10^(-6)降至36×10^(-6)。此外,在加入精炼渣15 min后加入SiCaBa合金,对比30 min后加入的试验结果表明:夹杂物的数量密度进一步下降到70个/mm^(2),直径3.4μm,在几种脱氧处理中夹杂物数量最少、改性最优。全氧含量降至最低为原钢样的73%,使冶炼后的304N不锈钢洁净度达到最高。

304N不锈钢的最佳固溶处理工艺

通过Thermo Calc热力学计算软件计算了理论固溶温度,通过正交试验、显微组织观察、SEM组织形貌及能谱分析等方法,研究了温度及保温时间对试验钢的影响。结果表明,热力学软件计算的理论固溶温度与试验温度基本吻合。温度对固溶的影响大于时间。综合考虑晶粒大小及其对力学性能的影响,最佳固溶处理制度为1100℃×2 h。