製程參數對冷軋IF鋼二次加工脆化的影響

Effect of Processing Parameters on the Secondary Work Embrittlement in Cold-rolled IF Steels

10.6409/JMSE.200001.0209

陳煌湶(Huang-Chuan Chen)；張六文(Liuwin Chang)

冷軋 ； IF鋼 ； 二次加工脆化 ； 轉脆溫度 ； 鋼胚再加熱溫度 ； Cold-rolled ； IF steel ； Secondary work embrittlement (SWE) ； SWE-temperature ； Slab reheating temperature

材料科學與工程

32卷4期（2000 / 01 / 01）

209 - 216

繁體中文

添加Ti及複合添加Ti+Nb極低碳IF鋼經不同熱軋、冷軋及退火製程後，量測其二次加工轉脆溫度，顯示降低鋼胚再加熱溫度(SRT)可降低轉脆溫度。提高盤捲溫度(CT)對轉脆溫度影響不大，但可降低再結晶溫度及材料強度。其原因爲微細TiC析出物略粗大化之故。析出物分析顯示，低SRT鋼料有較多自由C，因其強化晶界而使鋼材有較低轉脆溫度。Ti+Nb IF鋼之轉脆溫度比Ti IF鋼之轉脆溫度低，可能主要因固溶Nb偏析至晶界因而強化晶界。提高冷軋率可使材料∆r值降低因而降低轉脆溫度。轉脆溫度的高低除了須攷慮晶界強度外，尚須攷慮材料本身之強度。文中對二次加工脆化之機構提出了說明。

Ti and Ti+Nb added extra-low carbon IF (Interstitial free) steels were hot-rolled, cold- rolled and annealed at various conditions. It is found that decreasing SRT (slab reheating temperature) decreases SWE-temperature (secondary work embrittlement temperature). Increasing coiling temperature decreases recrystallization temperature and strength of the material but does not give much effect on SWE-temperature. This is attributed to the coarsening of the fine TiC precipitates. Precipitates analysis shows that more amount of free carbon remains in low SRT materials. This free carbon segregates to grain boundary to increase the strength of the grain boundary. Therefore, the SWE-temperature in low SRT materials is low. Nb+Ti IF steel reveals lower SWE-temperature than Ti IF steel. This may be due to the segregation of solute Nb to the grain boundary. Increasing the amount of cold reduction decreases Ar value and results in improving the resistance to SWE. It is suggested that both grain boundary strengthening and material strengthening affect the SWE-temperature. An explanation is proposed to illustrate the mechanism of the secondary work embrittlement phenomenon.