回火温度对高强无碳化物贝氏体钢无缝管组织和性能的影响

研究了正火后回火温度对无碳化物贝氏体钢无缝钢管组织和性能的影响。试验结果表明,930 ℃正火后在600 ℃以下回火时,随回火温度的提高,试验材料的抗拉强度有降低的趋势,但降幅不大,强度在973~1012 MPa变化。试验材料的冲击吸收能量在300 ℃达到最大值,为72 J;400 ℃回火时,冲击吸收能量出现最低值,出现无碳化物贝氏体钢的回火脆性;回火温度超过400 ℃时,冲击吸收能量上升;300~350 ℃回火时,伸长率和断面收缩率最高。在400 ℃以下回火时,试验材料的组织由无碳化物贝氏体、块状铁素体和残留奥氏体组成;超过400 ℃回火时,组织为粒状贝氏体及块状铁素体。无碳化物贝氏体钢无缝钢管930 ℃正火,300 ℃回火时具有较佳的综合力学性能。

Effect of tempering temperature on microstructure and properties of high strength carbide-free bainitic steel seamless pipe

Effect of tempering temperature after normalizing on the microstructure and properties of carbide-free bainitic steel seamless pipe was studied. The results show that when normalized at 930 ℃ and then tempered at below 600 ℃, the tensile strength of the tested material tends to decrease with the increase of tempering temperature and changes within the range of 973 MPa to 1012 MPa. When tempered at 300 ℃, the impact absorbed energy of the tested material is the maximum, as 72 J. When tempered at 400 ℃, the impact absorbed energy is the lowest, and the tempering brittleness of carbide-free bainitic steel appears. When tempered at above 400 ℃, the impact absorbed energy of the tested material increases. The elongation and the reduction of area reach the maximum when tempered at 300-350 ℃. When the tempering temperature is below 400 ℃, the microstructure of the tested material consists of carbide-free bainite, bulk ferrite and austenite. When the tempering temperature is over 400 ℃, the microstructure becomes granular bainite and bulk ferrite. Carbide-free bainitic steel seamless pipe has the better comprehensive mechanical properties when normalized at 930 ℃ and then tempered at 300 ℃.