卷取温度对Ti微合金化高强钢力学性能的影响机理

Effect of coiling temperature on the mechanical properties of Timicroalloyed high strength steel

  • 摘要: 固定化学成分和其他工艺参数,研究了紧凑式带钢生产卷取温度变化(625和579℃对Ti微合金化高强钢组织和力学性能的影响。热轧带钢的力学性能测试表明,卷取温度降低后,屈服强度降低205 MPa,而-20℃冲击功由11.7J增加到47 J。采用光学金相、电子显微术等手段分析了钢中组织和析出物,625℃卷取带钢为铁素体组织,579℃卷取带钢组织更为细小,贝氏体特征明显;而卷取温度降低后纳米尺寸碳化物的数量显著减少,由此降低了沉淀强化效果,造成强度大幅下降,并与组织细化一起改善材料的韧性。卷取温度是Ti微合金化高强钢生产中重要的工艺参数,需要严格控制。

     

    Abstract: Keeping chemical composition and other parameters unchanged, the effects of coiling temperature (625 and 579℃) on the microstructure and properties of Ti-microalloyed high strength steel were investigated during compact strip production (CSP). Experimental results of mechanical properties show that compared with steel strips coiled at 625℃, the yield strength of steel strips coiled at 579℃ decreases by 205 MPa, but the impacting energy at -20℃ increases from 11.7 J to 47 J. Optical microscopy and electron microscopy were used to study the microstructure and precipitates in the steel. It is found that the primary microstructural constituent of steel strips coiled at 625℃ is ferrite grains, but the microstructure of steel strips coiled at 579℃ is finer and characterized with bainite grains. The volmne fraction of uanometer carbides in steel strips significantly reduces with decreasing coiling temperature, which weakens the precipitation hardening effect and causes a marked reduction of strength. However, the toughness is improved due to grain refinement and volume fraction decreasing of precipitates. Coiling temperature needs to be strictly controlled, because it is a more important parameter of producing Ti-microalloyed high strength steel.

     

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