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利用热膨胀仪研究了DP600双相钢、Q&P钢和22MnB5热冲压成形钢的奥氏体临界转变温度和CCT曲线,分析了合金元素对高强度汽车板相变规律的影响。结果表明,随着加热速率的增加,DP600双相钢、22MnB5钢的Ac_1和Ac_3温度增加。相同加热速率条件下,高强汽车板改变成分对Ac_1影响小,但DP600钢添加Cr后,Ac_3降低约20℃;Q&P钢降低1.0%Si、增加0.47%Al时,Ac_3增加50℃;22MnB5钢改变Si、Mn含量时,Ac_3变化约为10℃。DP600钢添加Cr元素后,奥氏体化曲线呈直线增加,相同温度时的奥氏体转变量明显增加。22MnB5钢中奥氏体化曲线呈直线增加,添加Cr元素后奥氏体化曲线右移,Si元素减少后,奥氏体转变量<40%阶段,奥氏体转变速率增加。Q&P钢奥氏体转变曲线呈直线增加,温度接近Ac_3时增速减缓,加入Al元素后奥氏体转变速率降低。C元素推迟了铁素体、珠光体、贝氏体、马氏体转变;Cr元素推迟了珠光体、贝氏体转变,降低了马氏体临界冷却转变速率,提高了高强汽车钢板的淬透性。
The critical austenite transformation temperatures and CCT curves of DP600 dual-phase steel, Q & P steel and 22MnB5 hot-stamping steels were studied by means of thermal dilatometer. The influence of alloying elements on the phase transformation of high strength automotive sheet was analyzed. The results show that the Ac_1 and Ac_3 temperatures of DP600 duplex steel and 22MnB5 steel increase with the increase of heating rate. Under the same heating rate, Ac_1 was reduced by about 20 ℃ for Cr600 steel and 1.0% for Q & P steel, and Ac_3 increased by 50 ℃ when 0.47% Al was added. The content of 22MnB5 steel changed In the case of Si and Mn, the change of Ac_3 is about 10 ℃. After adding Cr element to DP600 steel, the austenitization curve increases linearly and the austenite transformation amount increases obviously at the same temperature. The austenitization curve increases linearly in 22MnB5 steel, and the austenitization curve shifts to the right after adding Cr. When the Si content decreases, the austenite transformation rate increases with the reduction of austenite <40%. The austenite transformation curve of Q & P steel increases linearly. When the temperature approaches Ac_3, the growth slows down. The austenite transformation rate decreases with the addition of Al. C element delayed the transformation of ferrite, pearlite, bainite and martensite; Cr element postponed the transformation of pearlite and bainite, reduced the critical cooling rate of martensite transformation, and improved the quenching of high-strength automobile steel plate Sex.