Product Development of High Strength and Toughness Spring Flat Steel

With the continuous development of mechanical industry,higher requirements are put forward for the comprehensive properties of spring steel.The chemical composition and production process of spring flat steel are designed to meet the requirements of high strength and high toughness of spring flat steel,through the test,the product surface quality and internal quality all meet the national standards,the performance indicators to meet user requirements.

Surface decarburization characteristics and relation between decarburized types and heating temperature of spring steel 60Si2MnA

The characteristics of complete and partial decarburizations in spring steel 60Si2MnA were systematically investigated, including the microstructure, the hardness gradient, and the formation mechanism. The relation between decarburized types and heating temperature of the steel was comprehensively discussed. It is found that heating temper- ature has an important influence on the decarburized types. With the rise of heating temperature, the decarburized types change from no decarburization to complete decarburization, complete and partial decarburizations, partial decarburiza- tion, and no decarburization.

Forming condition and control strategy of ferrite decarburization in 60Si2MnA spring steel wires for automotive suspensions

The ferrite decarburization behavior of 60Si2MnA spring steel wires for automotive suspensions, including the forming condition and the influence of heating time and cooling rate after hot rolling, was investigated comprehensively. Also, a control strategy during the reheating process and cooling process after rolling was put forward to protect against ferrite decarburization. The results show that ferrite decarburization, which has the strong temperature dependence due to phase transformation, is produced between 675 and 875°C. The maximum depth is found at 750°C. Heating time and cooling rate after rolling have an important influence on decarburization. Reasonable preheating temperature in the billet reheating process and austenitizing temperature in the heat-treatment process are suggested to protect against ferrite decarburization.

Theory and Practice of Oxide Inclusion Composition and Morphology Control in Spring Steel Production

In order to control the composition,morphology and size distribution of oxide inclusions in spring steel,the relationship between the content or activity of aluminum and calcium in molten steel and compositions of oxide inclusion precipitated at different temperatures was determined based on thermodynamic equilibrium for spring steel 60Si2 MnA,and has been verified by practice.The size distribution of non-metallic inclusions electrolytically extracted from specimens of hot rolled spring steel was determined by image analyzer.The results show that there are a great deal of large inclusions in spring steel produced by the conventional process,and the quantity and the size of large inclusions in spring steel produced by new process are largely reduced.As a result,the fatigue properties of the spring steel produced by new process are highly improved,and the ratio ofσ-1/σbis raised from 0.451 to 0.468.

Development of a New Kind of High Strength Spring Steel

A new kind of high strength, high toughness and high plasticity spring steel has been developed. The strength, the reduction of area and the elongation of the steel are all higher than those of the steel 60Si2CrVA. The decarburization resistance and the sag resistance are also higher than those of the steel 60Si2CrVA. It has good hardenability, and is suitable for making springs with big cross section. The bogie springs made of this kind of steel have passed 2×106 cycles without broken under the conditions of maximum stress of 906 MPa and the minimum stress of 388 MPa.

Corrosion behavior of high-strength spring steel for high-speed railway

The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.

FEM Simulation of Effect of Process Parameters on Static Recrystallization in 60SiMnA Spring Steel

Two-dimensional rigid-plastic finite element method (FEM) was used for simulation of the effect of process parameterson the static recrystallization of 60SiMnA spring steel using MARC/AutoForge 3.1 software. A thermo-mechanicalcoupled analysis was conducted considering the heat transfer between the workpiece, the roll and the environment,and the heat generation due to plastic work. The static recrystallization laws under different processing conditionsand the predicted distribution of the static recrystallization volume fraction on the deformation cross section arepresented.

Effect of Boron on Delayed Fracture Resistance of Medium-Carbon High Strength Spring Steel

The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron eontent from 0. 000 5% to 0. 001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initia tion area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 （C, B） phase.

Inclusion control of automotive spring steel in the basic oxygen furnace and ingot casting process

The process of automotive spring steel in the basic oxygen furnace and ingot casting （BOF-IC） of Baosteel is described in this paper. High quality spring steel can be obtained through designing reasonable deoxidization and alloying processes ,enhancing steel purity and reducing inclusions in steel.

Analysis of vibration reduction characteristics and applicability of steel-spring floating-slab track

A coupled dynamics computation model for metro vehicles, along with a steel-spring floating-slab track, is developed based on the theory of vehicle-track coupled dynamics. Using the developed model, the influences of the thickness, length and mass of floating-slab, spring rate and its arrangement space, running speed, etc. on the time and frequency domain characteristics of steel-spring fulcrum force are analyzed. The applicability of steel-spring floatingslab track is discussed through two integrated example cases of metro and buildings possessing distinct natural vibra- tion characteristics. It is concluded that, it is quite significant, in the optimization modular design of the parameters of steel-spring floating-slab track, to take the matching relationship of both the amplitude-frequency characteristics of steel-spring fulcrum force and natural vibration characteristics of integrated structures into comprehensive consideration. In this way the expensive steel-spring floating-slab track can be economically and efficiently utilized according to the site condition, and at the same time, the economic losses and bad social impact resulted from the resonance during usage of steel-spring floating-slab track can be avoided.

Relationship between microstructures and mechanical properties of resistance spot welded joint of spring steel

Based on mechanical properties tests and microstructures investigations, the relationship between microstructures and mechanical properties of resistance spot welded joints of spring steel is studied. The agglomeration of precipitated carbide is the sign that indicates spot welded joints structure of spring steel is fully tempered. Spot welded joints microstructure of nickelplaied spring steel is fully tempered in random tempering heat treatment process, and mechanical properties of the welded joints are advanced. This research results showed a new approach for increasing spot welded joints quality of spring steel and hardened steel.

3-D thermo-mechanical coupled FEM simulation of continuous hot rolling process of 60SiMnA spring steel bars and rods

The 3-D thermo-mechanical coupled elasto-plastic finite element method (FEM)was used for the simulation of the two-pass continuous hot rolling process of 60SiMnA spring steelbars and rods using MARC/AutoForge3.1 software. The simulated results visualize the metal flow andthe dynamic evolutions of the strain, stress and temperature during the continuous hot rolling,especially inside the work-piece. It is shown that the non-uniform distributions of the strain,stress and temperature on the longitudinal and transverse sections are a distinct characteristic ofthe continuous hot rolling, which can be used as basic data for improving the tool design,predicting and controlling the micro-structural evolution of a bar and rod.

Present situation and countermeasure of low-alloy spring steel wire rod for domestic automobile

The variety,inner quality and surface quality of low-alloy spring steel wire rod for domestic automobile is summarized in detail.And according to commercial low-alloy spring steel wire rod variety, product quality level and its actual application situation on automobile supplied by present industrially developed country metallurgy enterprises,it is pointed that the variety of low-alloy spring steel wire rod for domestic automobile can't satisfy the requirements of automobile industry development,compare with overseas advanced technology,product quality has the following gaps:the first is that steel purity is low,the control level of non-metallic inclusions is not steady,there is often large grain difficult deforming non-deformation inclusions existing,the control level of steel purity has big difference,the level of large steel factory is high,but its steady has a large gap compare with foreign advanced level,not to mention small steel factory which research and development powder is low.The second is surface complete decarburization can' t be avoided completely.The third is that surface defects are more.The fourth is that composition segregation and structure segregation are not steady,steel wire can't be drawn normally when the segregation is serious. In all,the segregation of 55SiCrA is superior to 60Si2MnA obviously.The industrialization of domestic high level low-alloy spring steel wire rod can't seek quick success and instant benefits,independent innovation perseveringly must be adopted,the success may be reached after master core technologies and adopt the science way of step by step.

Effects of F-EMS on the solidification structure of 60Si_2CrVAT spring steel billets

The effects of the final electromagnetic stirring （EMS） on the solidification structure of 60Si2CrVAT high strength spring （HSS） steel of continuous casting （CC） billets has been studied. The analysis of the solidification structure is based on the comparison between the macrostructure, microstructure, carbon segregation and defects of the 60Si2CrVAT billet with mold-electromagnetic stirring （ M - EMS ） and those with the M ＋ final solidification zone electromagnetic stirring （ F - EMS）. It is found that the solidification structure of the billet with the F - EMS is improved with the tightness of the billet and the increase in the ratio of the equiaxed structure,the inner porosity and the shrinkage are remarkably reduced, and that the ratio of central carbon segregation sharply decreases. Meanwhile, the secondary dendrite arm spacing （SDAS） is improved, and the ratio of central equiaxed grain considerably increases, which results in finer grains. Therefore ,the quality of the billet is enhanced with the F - EMS.

Development of Low and Middle Carbon Martensite Spring Steel with High Strength and Toughness for Automobile

The conventional middle and high carbon spring steels have some drawbacks in properties, production and application. In order to meet the demands of rapid development of automobile, a new low and middle carbon spring steel 35Si2CrMnVB, C0.34, Sil.66, MnO.80, CrO.67, V0.13, B0.001, P0.011, S0.014 wt.%, has been developed. Comparison between the new spring steel 35Si2CrMnVB and the conventional spring steel 60Si2MnA, C0.61, Si 1.75, MnO.76, P0.021, S0.018 wt.%, shows that the new spring steel has not only high strength, good ductility, good comprehensive mechanical properties, but also low decarbonization tendency, sufficient hardenability and high elastic sag resistance, etc.. The microstructure change in quenched steel caused by the decreasing of carbon contents is detected through metallographic observation, the new low and middle carbon spring steel 35Si2CrMnVB after quenching is composed of almost lath martensite with high dislocation density and only a little martensite with twin structure. It is testified that to develop low carbon spring steel with more excellent properties for automobile is feasible.

Analysis of Fatigue Fracture with Scanning Electron Microscopy of Valve Spring Steel

Valve spring steel for engines, belonging to the class of super clean steel, must be supported due to their application, high numbers of cycles in fatigue and cannot suffer any type of failure, which would be catastrophic for the vehicle. From these considerations, it was tested in axial fatigue, a test that can detect possible internal defects in their structure, caused by inclusions, a class of valve spring steel, where it aimed to discover the values of their fatigue life, followed by an analysis ofmicrostructural fracture surface by SEM （scanning electron microscopy）. It was proved, after testing, the specimens tested broke up a number of cycles always compatible with the life work of a valve spring and that fractures always occurred by surface defects in the specimens.

等温淬火温度对51CrMnV弹簧钢组织及性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、电子背散射衍射(EBSD)技术和电子万能试验机等研究了等温淬火温度对51CrMnV弹簧钢组织及力学性能的影响。结果表明:使用高温油淬火介质进行等温淬火处理后,51CrMnV弹簧钢的组织主要为马氏体、贝氏体铁素体、残留奥氏体及碳化物;经过860℃奥氏体化30 min后淬入280℃的高温油中等温处理30 min后,51CrMnV弹簧钢的力学性能较好,其抗拉强度为1641 MPa、总伸长率为15.57%、断面收缩率为33%,且该工艺条件下的拉伸试样断口为韧性断裂,这归因于该工艺条件下试验钢具有亚微米级贝氏体铁素体和弥散分布的碳化物,多相微观组织的协同作用提高了51CrMnV弹簧钢的综合力学性能。

抗震钢支座中新型钢板簧的优化

钢弹体抗震钢支座是一种新型抗震支座,其通过在传统球型钢支座外侧增设的新型钢板簧为支座提供必要的地震恢复力以及地震耗能,在小震下保证了支座在震后的基本复位;强震作用下吸收地震能量,并可实现支座在震后的部分复位,满足基本的通车要求。首先,对该新型钢板簧进行了力学性能试验,建立了有限元模型,并利用试验结果验证了支座有限元模型的有效性。其次,对单个钢板簧和钢支座整体结构进行了动力特性分析,研究了新型钢板簧对抗震耗能的贡献;同时,对新型钢板簧结构进行了参数分析,找出各参数的影响规律。最后,对新型钢板簧的刚度和尺寸参数进行了多参数拟合,得到拟合函数,完成了新型钢板簧尺寸的结构优化,达到了节省材料、缩小结构空间的目的。

车辆载荷下钢弹簧浮置板轨道振动特性分析

建立车辆-钢弹簧浮置板轨道垂向耦合振动有限元模型,分析车载作用下的浮置板轨道和车辆垂向振动特性。结果表明,钢轨和车体垂向振动在浮置板1阶弯曲频率(10 Hz)、P2共振频率、部分阶次的轮对弯曲频率及车轮辐板模态频率处存在明显峰值,其中车体振动在车体浮沉频率(1 Hz左右)处也存在明显峰值。扣件刚度和阻尼的影响主要在轮对1阶弯曲频率以内的车辆-轨道系统耦合振动行为,扣件阻尼在高频处对轨道垂向振动也有较大影响。钢弹簧刚度和阻尼主要影响浮置板1阶弯曲频率附近的车辆和轨道响应,对车辆运行平稳性影响显著。车辆悬挂参数及车体和构架质量对轨道振动基本无影响,簧下质量通过P2共振以及系统约束下的轮对1阶弯曲和辐板对称伞形模态影响轨道振动。增大一系悬挂刚度和阻尼以及二系悬挂阻尼会增大中高频的车体垂向振动加速度,二系悬挂刚度主要影响车体浮沉频率附近的车体垂向振动。车体、构架和簧下质量对车体浮沉运动、浮置板1阶弯曲和P2共振处的车体振动加速度峰值有影响。

低频脉冲磁场对60Si2CrVA弹簧钢凝固组织的影响

研究了浇注前与浇注后施加脉冲磁场对60Si2CrVA弹簧钢凝固组织的影响。结果表明,浇注前与浇注后施加脉冲磁场对铸锭边部柱状晶生长均有明显的抑制作用,对铸锭心部晶粒有明显的细化作用,但二者之间差别不大。与常规浇注铸锭相比,浇注40 s后施加脉冲磁场柱状晶区仅为(4.9±0.3)mm,降低了53.7%,心部晶粒尺寸细化至(407±30)μm,降低了47%。脉冲磁场引入的强制对流可使中心熔体的平均冷却速率由常规时的1.45℃/s提高至2.36℃/s左右。脉冲磁场调控凝固组织的作用机制主要是促进了晶核增殖和漂移,对柱状晶生长的阻碍效果更明显。