Thesis Advisor王仪康
Degree Grantor中国科学院金属研究所
Place of Conferral中国科学院金属研究所
Abstract高强度调质钢在结构用钢方面有广泛的应用,如管线、冶金设备、起重机和海上平台,具有良好的韧性和焊接性能。本论文针对宝钢八十公斤坯在重钢五厂的热轧板,系统的测定了此钢的连续冷却曲线(CCT)、等温转变曲线(TTT)、不同回火温度下的常规拉伸和冲击及缺口敏感性。对原钢板的断裂韧性、低温性能(如低温条件下的拉伸、冲击和落锤撕裂)做了系统的研究,同时对不同回火温度下的精细且织结构及其对性能的影响也做了详尽的分析。实验的结果表明:在连续冷却中,这种钢的临界冷却速度为9.3 ℃/S,马氏体的临界转为温度为420 ℃,因此具有较好的淬火工艺性能。在等温转为中,有较长的孕育期和转为时间,这主要是合金元素的加入和其碳化物的形成阻碍碳的扩散和合金元素的重新分布,为适当的改变热处理工艺、控制各相的含量提供了条件。随回火温度(550 ~ -650)升高,碳化物析出并长大,同时位错的强化作用减弱,使抗拉强度及硬度减小。横向试样的冲击在600 ℃回火时裂纹的形成功下降,出现横向回火脆现象,而纵向试样无比现象,反应热轧板的组织方向性。在原板的低温试验中,冲击和落锤撕裂测得的横向韧-脆转变温度分别为-28 ℃和17 ℃,与同类的结构钢板相比,此温度略高。这可能是由横向回火脆所引起的。低温拉伸在-10℃ 时出现断口分裂,这是由于成分偏析和夹杂物偏聚所造成的。关于横、纵断裂韧性,纵向明显高于横向,同Welten60相比,这种钢具有高的强度、良好的塑性和较小的裂纹扩展功。本论文还针对热轧后调质钢的横、纵向的性能差异及回火脆性和纵向试样拉伸出现的断口分裂现象做以详尽的讨化。
Other AbstractHigh strength quenched and tempered steels find a variety of application in structures including pipeline, mining equipments, cranes and off shore- platforms. where they offer weight savings combined with toughness and weldability. The Austenite transformation characteristics of the steel is studied in this article. Its schematic continuously cooling transformation (CCT) and isothermal transformation and critical transformation temperature are measured by Formaster-F type dilatometer. The mechanical properties, namely, tensile ductility, charpy impact energy at different heat-treatment procedure are studied the other properties such as tensile and impact and drop weight tear test(DWTT) at low temperature, fracture toughness from the original are researched systematically. the corresponding microstructure and carbide distribution in matrix are studied by electron microscopies, X-ray diffraction and TEM. the effects of microstructure on the properties are discussed in detail. In the view of the results, the critical rate of cooling for martensite transformation is 9.3 ℃/S, the critical transformation temperature is 420 ℃, this steel has good hardenability. for isothermal transformations, more transforming time is desired since alloy element adding in steel and carbide formed hold carbon diffusion and redistribution of alloy element. The possibility of improving heat treatment procedure and controlling the content of different phase is offered. As temptering temperature increase (550-650 ℃), tensile strength and yield strength and notch tensile strength and hardness gradually decrease byu growing of carbide and droping of dislocation harded functions. There is temper brittleness tempering at 600 ℃ in transeverse samples, the longistitude is not. It have proved that the microstructure of hot-rolling steel has orientation. For transeverse samples tough-brittle temperature is 17 ℃ measured by DWTT. Compared with the Welten60 steel. This steel have high-strength and more good plastics and less crack expand energy. The different of properties between the transverse and longititude from the quenched-tempered steel and temper brittleness and appearance of split in tensile at low temperature for element heterogentity are discussed.
Document Type学位论文
Recommended Citation
GB/T 7714
刘忠海. 八十公斤级调质钢组织结构与性能[D]. 中国科学院金属研究所. 中国科学院金属研究所,1992.
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