冷却工艺对贝氏体钢拉杆组织和性能的影响

研究了热处理冷却工艺对贝氏体钢拉杆组织及力学性能的影响。试验结果表明,ø70 mm贝氏体钢拉杆材料经920 ℃空冷+300 ℃回火、920 ℃水冷30 s后出水空冷+300 ℃回火后,杆体的组织为贝氏体铁素体和残留奥氏体;经920 ℃水冷+200 ℃回火后,杆体的组织为回火板条马氏体和残留奥氏体。920 ℃水冷+200 ℃回火时棒料1/2半径处的R_m为1513 MPa、KV₂为73.2 J、硬度为46.5 HRC;920 ℃水冷30 s后空冷+300 ℃回火时棒料1/2半径处的R_m为1254 MPa、KV₂为76.0 J、硬度为42.0 HRC;920 ℃空冷+300 ℃回火时棒料1/2半径处的R_m为1226 MPa、KV₂为75.5 J、硬度为41.9 HRC。ø70 mm贝氏体钢拉杆热处理先水冷后空冷可以提高其冲击性能。

Effect of heat treatment and cooling process on microstructure and properties of bainitic steel tie-rods

The effects of heat treatment and cooling process on the microstructure and mechanical properties of the bainitic steel tie-rod with 70 mm in diameter were studied. The results show that the structure of the rod is bainite ferrite and residual austenite when heated at 920 ℃ and air cooled, and then tempered at 300 ℃, or heated at 920 ℃, water cooled for 30 s and air cooled, and then tempered at 300 ℃. The structure of the rod body is tempered lath martensite and retained austenite when heated at 920 ℃, water cooled and then tempered at 200 ℃. At half radius of the bar after water cooling at 920 ℃ and tempering at 200 ℃, R_m is 1513 MPa, KV₂ is 73.2 J, hardness is 46.5 HRC; after water-cooling for 30 s and air cooling at 920 ℃ and tempering at 300 ℃, R_m is 1254 MPa, KV₂ is 76.0 J, hardness is 42.0 HRC; after air cooling at 920 ℃ and tempering at 300 ℃, R_m is 1226 MPa, KV₂ is 75.5 J and hardness is 41.9 HRC. When the ø70 mm bainitic steel tie rod is actually normalized, the impact toughness can be improved by water-cooling before air-cooling.