中碳V-N微合金钢连续冷却奥氏体分解及晶内铁素体的形成  

Austenite decomposition and intragranular ferrite formation in a medium-carbon vanadium-nitrogen microalloyed steel

作　　者：许磊[1] 刘国权[1] 

机构地区：[1]北京科技大学材料科学与工程学院,新金属材料国家重点实验室,北京100083

出　　处：《材料热处理学报》2009年第3期102-106,共5页Transactions of Materials and Heat Treatment

基　　金：国际钒技术委员会资助(VANITEC);国家自然科学基金资助(50271009)

摘　　要：采用Gleeble-1500热模拟实验机，对一种中碳V-N微合金钢生产过程的中间冷却、再加热、张力减径及其后冷却过程进行了物理模拟。在张力减径变形后分别在800、730、650、630、615、600、585和550％采用水冷至室温。研究了张力减径变形后控冷过程中奥氏体的分解规律，重点分析了诱导晶内铁素体形成的因素。结果表明：奥氏体的分解转变依次为晶界铁素体、晶内铁素体和珠光体；在745～639℃范围内，奥氏体分解主要为晶界铁素体形核、长大阶段；冷却到639℃后，大量的晶内铁素体和珠光体开始形核析出。除已广泛接受的依附夹杂物形核外，析出相及先形成铁素体晶界同样是晶内铁素体的有效形核位置。能谱分析表明，诱导晶内铁素体形核的夹杂物附近没有出现贫化区，钢中夹杂物诱导晶内铁素体的形核应该是由惰性界面能和应力．应变能的共同作用。The intermediate cooling, reheating, stretch reducing and controlled cooling after stretch reducing in seamless tube manufacture process was simulated for a medium-earbon vanadium-nitrogen microalloyed steel by a Gleeble-1500 simulator. After stretch reducing, the samples were water quenched to room temperature from 800, 730, 650, 630, 615, 600, 585 and 550℃, respectively. Based on the experiments, austenite decomposition during controlled cooling after stretch reduction was studied. And factors promoting the formation of intragranular ferrite were also analysed. The results show that austenite decomposes into grain boundary ferrite （ GBF）, intragrannlar ferrite （IGF） and pearlite progressively. The decomposition products are mainly GBF when the quench-starting temperature is between 745 to 639℃, while both IGF and pearlite have been formed when the quench-starting temperature is below 639℃ . Besides nucleation at inclusions, second-phase precipitates and pre-formed ferrite can also be nucleation sites for IGF. Since no local solute depletion around the inclusions is found, it is considered that the IGF nucleation is promoted by the combination effect of the inclusions and volumetric strain concentration existing in the experimental steel.

关 键 词：V-N微合金钢 晶内铁素体 形核机理 连续冷却 变形 

分 类 号：TG111.7[金属学及工艺—物理冶金] TG142.33[金属学及工艺—金属学]