随着汽车行业的高速发展，汽车钢的高性能与轻量化要求越来越高。弹簧是汽车重要部件，我国60%的弹簧钢消耗量都来自于汽车领域，其中悬架簧是连接汽车悬架和车体的关键部件，其质量对汽车的性能至关重要，因此，开发与研究性能优异的悬架簧用钢具有重要的现实意义。本文采用多种表征手段以及拉伸、包辛格扭转、循环拉伸等性能测试实验围绕悬架簧用钢的强化方式、成分优化设计、合金元素作用机理、松弛抗力和滞弹性等方面展开研究，以期开发出具有优异的强塑性和松弛抗力的2100MPa级工业悬架簧用钢。本文选取54SiCrV6弹簧钢为基础研究对象，对54SiCrV6弹簧钢进行了组织表征。54SiCrV6弹簧钢的基体组织为回火马氏体，析出相主要有细小的球型碳化物MC、长条状的Fe2.4C或Fe2.5C和少量的尺寸较大的球形Fe3C，位错密度在1015m-2量级。将组织信息代入屈服强度模型，量化了各强化方式的贡献量：54SiCrV6弹簧钢的主要强化方式为位错强化（50%）、析出强化（26%）和细晶强化（13%）。基于此，设计添加Nb和Si元素，得到2100MPa级别强塑性匹配良好的新型弹簧钢。通过对比S1与S2、S3与S4的组织性能差异分析Nb和Si在弹簧钢中的作用及机理。微量Nb元素可以大幅度细化基体组织，这是由于Nb是强碳化物形成元素，易形成NbC钉扎晶界从而细化组织。Nb元素导致的组织细化是强塑性提高的根本原因。Si元素可以改善碳化物的形态和分布，延缓ε碳化物向θ渗碳体的转变，这是S4号钢强度和弹减抗力提高的主要原因。对S4号钢不同回火温度的组织性能的研究表明，随着回火温度的提高，马氏体板条边界逐渐分解为链状碳化物M23C6，马氏体板条或马氏体片内的长条状ε碳化物逐渐转化为球状θ渗碳体；同时位错逐渐回复，位错密度降低，强度下降而塑性提高。因此确定实验钢最优回火温度为400℃。此外提出新的参数cSv（Si在富Si层的体积浓度）判断碳化物类型的变化，与实际吻合较好。 对不同回火温度下S4号钢的循环拉伸结果进行分析，探索了滞回环和滞弹性应变的机理。滞回环是由于位错的背应力造成，滞回环的大小与位错密度和碳化物的形态分布有关，通常是二者竞争的结果。滞弹性应变是可逆位错的有限移动造成的，与位错密度和可动位错段长度有关，经证明，滞弹性应变与两者乘积成正比。

With the rapid development of automobile industry, demand of high performance and lightweight of automobile steel becomes higher. Spring is an important part of automobile. In China, 60% of the consumption of spring steel comes from the field of automobile. Suspension spring is the key component connecting suspension and vehicle body, so its quality is important to automobile performance. Therefore, the development and research of suspension spring steel with excellent performance is of great practical significance. In this paper, characterization methods (OM, SEM, TEM, EBSD, XRD) and mechanical property tests (tensile test, Bauschinger torsion test and cyclic tensile test) are used to study the strengthening mechanism, composition optimization design, effect of alloy elements, sag resistance and anelasticity of suspension spring steel in order to develop 2100MPa industrial suspension spring steel with excellent strength, good ductility and sag resistance.In this paper, 54SiCrV6 spring steel is selected as the basic research object. The microstructure of 54SiCrV6 spring steel are analyzed. Matrix of 54SiCrV6 spring steel is tempered martensite. Precipitates in 54SiCrV6 spring steel are mainly fine spherical carbide MC, rod-like Fe2.4C or Fe2.5C and a small amount of spherical Fe3C precipitate with large size. Dislocation density is in the order of 1015m-2. These microstructure information is substituted into the yield strength prediction model to quantify the contribution of each strengthening part. The results show that the main strengthening methods of 54SiCrV6 spring steel are dislocation strengthening(50%), precipitation strengthening(26%) and fine grain strengthening(13%). Therefore, the design direction of alloy elements should be committed to improving fine grain strengthening and precipitation strengthening. Based on this idea, Nb and Si are designed to be added. The tensile results show that the performance of S4 steel with high Si content is the best, which meets the strength and ductility requirements of 2100MPa new spring steel.By comparing the microstructure and properties of S1 and S2, S3 and S4, effect and mechanism of Nb and Si in spring steel are analyzed. Trace Nb element can greatly refine the microstructure. This is because Nb is a strong carbide forming element, which tends to form NbC pinning grain boundary to refine the microstructure. The microstructure refinement caused by Nb element is the fundamental reason for the improvement of strength and ductility. Si element can improve the morphology and distribution of carbides, delaying the transition of ε-carbides to θ-cementites. It is the main reason for the improvement of strength and sag resistance of S4 steel.The study on the microstructure and properties of S4 steel at different tempering temperatures shows that with the increase of tempering temperature, the boundary of martensite lath gradually decomposes to chain M23C6 carbides, and rod-like ε-carbides gradually transform into spherical θ cementites. At the same time, dislocation recovers gradually and the dislocation density decreases with the tempering temperature increases, resulting in the strength decreasing and the ductility increasing. Therefore, the optimum tempering temperature of the experimental steel is 400℃. Besides, a new parameter cSv is proposed to predict the types of carbides, which means the volume concentration of Si in Si-rich layer and the result is in good agreement with the experimental resultsBy analyzing the cyclic tensile test results of S4 steel at different tempering temperatures, the mechanism of hysteresis loop and anelastic strain is explored. Hysteresis loop is caused by the back stress of dislocation. The area and width of hysteresis loop are related to the dislocation density and the morphology and distribution of carbides, which are usually the results of competition between dislocation and carbides. The anelastic strain is caused by the limited movement of reversible dislocations. It is related to the dislocation density and the length of movable dislocation segment. It is proved by calculation and experiment that the anelastic strain is directly proportional to the product of dislocation density and the length of movable dislocation segment.