Effect of coiling temperature on the mechanical properties of Timicroalloyed high strength steel
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摘要: 固定化學成分和其他工藝參數,研究了緊湊式帶鋼生產卷取溫度變化(625和579℃對Ti微合金化高強鋼組織和力學性能的影響。熱軋帶鋼的力學性能測試表明,卷取溫度降低后,屈服強度降低205 MPa,而-20℃沖擊功由11.7J增加到47 J。采用光學金相、電子顯微術等手段分析了鋼中組織和析出物,625℃卷取帶鋼為鐵素體組織,579℃卷取帶鋼組織更為細小,貝氏體特征明顯;而卷取溫度降低后納米尺寸碳化物的數量顯著減少,由此降低了沉淀強化效果,造成強度大幅下降,并與組織細化一起改善材料的韌性。卷取溫度是Ti微合金化高強鋼生產中重要的工藝參數,需要嚴格控制。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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Key words:
- high strength steel /
- microalloying /
- titanium /
- coiling temperature /
- nanoparticles /
- carbides /
- strength of materials /
- toughness
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