【作者】 魏胜辉；

【导师】 刘瑞玲；

【作者基本信息】 河北科技大学 ， 材料加工工程， 2009， 硕士

【摘要】 钢铁生产中微合金化技术的开发和应用是20世纪后期物理和力学冶金的重大进展之一,从20世纪60年代开始,微合金化技术就以其显著的技术、经济优势在世界范围内得到广泛应用。微合金化铸钢是在微合金化钢技术基础上发展起来的。相对于一般工程用铸钢,其特点是具有高的屈服强度,较高的韧性和良好的焊接性能。同时由于微合金化元素加入量少,对铸钢的铸造性能影响很小,同时也可用常规熔炼设备生产,故成本较低。用该材料制造构件可减轻构件重量,提高寿命,维修方便,尤其适合于铸焊复合结构件,可显著节省材料和能源,提高经济和社会效益。微合金化铸钢不同于微合金化控扎钢材和锻钢,不能通过热机械加工变形细化晶粒来强化,只能依靠选择适当的合金成分,控制凝固过程和通过适当的热处理来调整钢的内部组织,提高力学性能,以适应各种不同的需要。本课题是在铸钢ASTM A27 65-35的基础上,通过对单独和复合加入不同量微合金化元素Nb、V、Ti的试件进行力学性能测定,以及用金相显微镜和扫描电镜对试件显微组织进行观察,研究了单独和复合加入不同量微合金化元素Nb、V、Ti对铸钢组织和力学性能的影响。研究表明,Nb、V、Ti的单独加入,细化了铸钢的组织,起到了细晶强化的作用,有效提高铸钢的强度、硬度及塑性。同时由于碳化物的形成,起到了很好的沉淀强化的作用。其中,Nb对铸钢的塑性提高作用较大,V对铸钢的低温冲击功提高较大,Ti的加入使铸钢强度提高作用较大,但使低温冲击功下降较大。复合加入对铸钢力学性能的影响比单独加入大。当铸钢中复合加入Nb、V、Ti三种元素中两种以上时,能显著提高钢的力学性能。复合加入时,Nb、V和V、Ti两种元素的复合加入,对提高铸钢的屈服强度、抗拉强度的效果要好于单独加入。相对于单独加入Ti,Nb、Ti的复合加入效果不明显。其中,Nb、V复合加入在提高铸钢强度的同时,塑性和低温冲击韧性下降较少。V、Ti复合对增加铸钢的抗拉强度效果好于Nb、V和Ti、Nb复合加入。Nb、V、Ti三种元素的复合加入所产生的强韧化作用,是晶粒细化、沉淀强化以及固溶强化等综合作用的结果。研究表明,复合加入合适的微合金化元素后,可使试件的抗拉强度提高22%,屈服强度提高34%,同时保持了原来的塑性和低温冲击韧性。更多还原

【Abstract】 The development and application of microalloy technology in steel production is the significant development of Metallurgy of Physics and Mechanics in the 20th century. This technology has been widely used in the whole world because of its obvious technical and economic advantage. Micro-alloyed cast-steel was developed from microalloy technology in steel, which features a high yield strength; high toughness and good welding performance compared with ordinary cast steel. Since micro-alloying element is used less, the effects on casting properties is very small. Micro-alloyed cast-steel can also be produced in normal smelting unit, so the cost is quite low. And when using it in casting, it can reduce weight, reduce service component and bring convenient maintenance, and it is particularly suitable for compounded casting by welding and casting, which can save material and energy largely, improve social and economic benefits.Micro-alloyed cast steel is different from microalloy rolling steel and forging steel, and can not be strengthened through the thermo-mechanical deformation of grain refinement process. It can be improved microstructure and mechanical properties by using suitable alloying component, controlling the process of the metal solidification and heat treatment. At the same time,it can be suited to different requirement.This topic is based on the cast steel ASTM A27 65-35. By adding individual and compound different amount of micro-alloying elements Nb, V, Ti, mensurating the mechanical properties of the specimen and observing the microstructure with the optical microscope and scanning electron microscope,study the effect on microstructure and mechanical properties of cast steel by adding individual and compound different amount of micro-alloying elements Nb, V, Ti.The studies show that adding individual elements Nb, V, Ti to the cast steel, refined the microstructure, played a role in fine-grain strengthening, effectively improve the steel’s strength, hardness and plasticity. At the same time due to the form of carbides, which played a very good precipitation strengthening and toughening effect. Among them, Nb enhanced role of the plasticity of the steel large, V improved the cast of the low-temperature impact energyr, Ti make steel strength increased more, but make the greatest decline in low-temperature impact energy.The effect on the mechanical properties of cast steel by adding compound elements is large than that by adding individual element. By adding two or more elements of Nb, V, Ti, it can improve obviously the mechanical properties of steel. The effects on improving yield strength, tensile strength by adding Nb, V, and V, Ti is better than adding individual element. Relative to adding individual Ti,adding compound Nb, Ti have a little effect. Adding compound Nb, V can enhance the strength of steel, while plastic and low-temperature impact toughness descend smally. The effect of increasing the tensile strength by adding V, Ti is better than adding Nb, V and better than adding Ti, Nb. The effects to improve the strength and toughness by adding the three elements are a comprehensive results of the grain refinement,precipitation strengthening and solid solution strengthening. Studies show that adding compound appropriate micro-alloying elements, the sample’s tensile strength can be increased 22%, yield strength be increased 34%, while maintain tensile stretch and low temperature impact toughness.更多还原