退火工艺对29Cr-4Mo超级铁素体不锈钢微观组织的影响

Effect of Annealing Process on Microstructure of 29Cr-4Mo Super Ferritic Stainless Steel

摘要:

以冷轧态29Cr-4Mo超级铁素体不锈钢无缝钢管为研究对象,研究了不同退火工艺对29Cr-4Mo超级铁素体不锈钢无缝钢管冷轧后微观组织的影响。结果表明,29Cr-4Mo超级铁素体不锈钢夹杂物主要成分为Cr2O3·MnO·Al2O3；在900 ℃下保温30 min,晶界三角连接处和夹杂物附近率先生成了少量σ相,σ相析出的平均面积分数随时间的延长而增加,随温度的升高而减少；当温度升高至1000 ℃,保温50 min未见有σ相析出,在900~1050 ℃整个温度区间内未见有χ相析出；建立了Sellars模型下铁素体再结晶晶粒长大经验公式,通过对比分析计算值与实验值,结果显示该公式能准确预测整个退火过程中的平均晶粒尺寸大小。

关键词:29Cr-4Mo钢;超级铁素体不锈钢;S44700;微观组织;σ相

Abstract:

The effect of different annealing processes on microstructure of 29Cr-4Mo super ferritic stainless steel seamless tube after cold rolling was investigated. The results show that the main inclusions in 29Cr-4Mo super ferritic stainless steel are Cr2O3·MnO·Al2O3. After annealing at 900 ℃for 30 min, the grain boundaries especially on triple junctions and near the inclusions firstly formed a small amount of σ phase. The average area fraction of σ phase increases with time prolonging while decrease with the temperature raising. There is no σ phase precipitating after holding for 50 min at 1000 ℃ and not founding χ phase during 900 ℃ to 1050 ℃. The empirical formula of ferrite recrystallization grain growth under classical Sellars model is established. The formula can accurately predict the average grain size in the whole annealing process by comparing the calculated value and the experimental value.

Key words:29Cr-4Mo steel; super ferritic stainless steel; S44700; microstructure; sigma phase; growth model