退火方式对含磷高强IF钢FeTiP析出及二次加工脆性的影响

Effect of annealing method on FeTiP precipitation and secondary working embrittlement of phosphorus-contained high strength IF steel

通过同炉钢相同工艺工业试制获得冷轧卷,经过罩式退火和连续退火生产含磷高强IF钢退火卷,研究了2种退火方式对含磷高强IF钢FeTiP析出及二次加工脆性的影响。利用低温落锤冲击试验机、TEM和析出物萃取定量分析法等手段分别对2种退火卷进行二次加工脆性转变温度及析出物表征分析研究。结果表明:连续退火和罩式退火生产卷FeTiP析出相主要集中在100 nm以下,罩式退火时间较长,罩式退火生产卷的FeTiP析出相数量是连续退火卷的2倍以上;根据定量分析法检测含磷析出相总量结果,结合热力学和动力学分析,P在晶界处的富集程度由最大偏聚系数和有效扩散距离决定,罩式退火卷P在铁素体晶界处偏聚远远大于连续退火卷,连续退火可得到比罩式退火更低的二次加工脆性转变温度的含磷高强IF钢。

The cold rolled coils were manufactured by the same furnace steel with the same process.The annealed coil of phosphorus-contained high strength IF steel was produced by batch annealing and continuous annealing.The effect of two annealing methods on the FeTiP precipitation and secondary working embrittlement of phosphorus-contained high strength IF steel were studied.The embrittlement transition temperature and precipitate characterization of anneal coil produced by two annealing methods were studied by means of low temperature drop hammer impact testing machine,TEM and precipitate extraction quantitative analysis.The results show that the FeTiP precipitates of continuous annealing and batch annealing are mainly concentrated below 100nm.Due to the longer annealing time of batch annealing,the FeTiP precipitates are more than twice that of continuous annealing.According to the amount of containing phosphorus precipitated phase detection results by quantitative analysis method,combined with thermodynamic and kinetic analysis,degree of enrichment in the grain boundary is determined by the maximum deflection coefficient and effective diffusion distance,the segregation of phosphorus at ferrite grain boundary place in batch annealed coil is much more than that of continuous annealed coil.Therefore,compared with batch annealing,continuous annealing can obtain phosphorus-contained high strength IF steel with lower embrittlement transition temperature in its secondary working.