井巷支护用U型钢亚温淬火及自回火工艺的研究

Study on Intercritical Hardening and Self-tempering of U-shape Steels for Mine Roadway Support

以20MnK、Q275两种牌号U型钢进行试验，全面探索了U型钢经亚温淬火及自回火后的强韧性。试验表明，经770～820℃水淬＋300℃自回火处理后，Q275U型钢的屈服强度σ0．2≥440MPa；经790～820℃水淬＋300℃自回火后，20MnKU型钢的屈服强度σ0．2≥520MPa。两种钢的屈服强度均比处理前提高50％以上，而屈强比≤0．75，伸长率δ5≥16％，达到国外同类U型钢的力学性能水平。此外，还对U型钢亚温淬火及自回火工艺的可行性及其强韧化机理进行了初步探讨。

This paper comprehensively studies the properties of strength and toughness of U-shape steels 20MnK,Q275 on test pieces under various processes of intercritical hardening and self-tempering. Experiments show that so long as the process of water quenching at 770~820℃ and succeedingly self-tempering at 300℃ is adopted,the σ0. 2 of U-shape steel Q275 is more than 440MPa, and after water quenched at 790~820℃ and self tempering at 300℃,U-shape steels 20MnK possess its σ0. 2≥520MPa. The yield strengthes of two steels can be increased by 50%,which is as high as that of imported U-shape steel and meet the performance demands of the elongation δ5≥16%,the ratio σ0. 2/σb≤0. 75. The feasibility and strengthening and toughening mechanisms of in tercritical hardening plus self-tempering process have also been discussed.