无镍高氮奥氏体不锈钢软化工艺研究

Study on Softening Process for Nickel-free High-nitrogen Austenitic Stainless Steel

手表壳的制作工序包括冲压、软化退火、切削加工、磨、抛等。材料的加工硬化、回复、再结晶、晶粒长大、夹杂物等严重影响手表壳的生产效率。由于低镍或无镍高氮不锈钢不会使人体皮肤过敏,是制作手表壳的首选材料。为此,设计并炼制了一种含0.59%N(质量分数)的无镍高氮奥氏体不锈钢。研究了该钢的冲压和软化退火工艺、加工硬化率,并检测了使用该钢制作的手表壳坯的硬度。结果表明:氮能显著提高无镍奥氏体不锈钢的加工硬化率,是316L和904L钢的3倍以上。手表壳坯经多次冲压后,硬度从280 HV0.3提高到了400 HV0.3,并难以通过网带炉退火软化至原始硬度。将手表壳坯的软化退火工艺从1100℃保温25 min调整为1100℃保温35 min,并在每冲压6次后进行1100℃保温1 h的固溶处理。结果,无镍高氮奥氏体不锈钢手表壳坯的硬度达到了要求。

Making process steps of watch shell involve stamping,softening,machining,grinding,and polishing.The work hardening,recovery,recrystallization,grain growth and inclusion of material will have serious influence on production efficiency of watch shell.Low-nickel or nickel-free high-nitrogen stainless steel is a preferred material from which watch shell is made because human skin is not allergic to it.In light of this fact,a nickel-free high-nitrogen austenitic stainless steel having 0.59%N by mass has been designed and smelted.Stamping and softening processes and work hardening rate for this steel were investigated.The watch shells made from this steel also were tested for hardness.The results showed that work hardening rate of the nickle-free austenitic stainless steel was considerably enhanced due to the addition of nitrogen,which was more than three times those of 316L and 904L steels.The hardness of watch shell blank increased from 280 to 400 HV0.3 after being stamped many times,and was difficult to be reduced to original hardness by softening in a mesh belt furnace.The softening process was adjusted from soaking at 1100℃for 25 min to soaking at 1100℃for 35 min,and the watch shell blanks were subjected to a solution treatment at 1100℃for 1 h after being stamped 6 times.As a result,the watch shell blanks made from the nickel-free high-nitrogen austenitic stainless steel achieved hardness which conformed with the requirements.