相变诱发塑性钢研究开发的进展

介绍了高强度低合金相变诱发塑性钢的研究现状,残余奥氏体形态、尺寸和体积分数对钢强塑性的影响以及为改善钢的热镀锌性能所进行的以铝代硅的成功开发;以热力学、动力学为工具进行的TRIP钢的成分设计以及相变塑性钢高速冲击拉伸性能的特点;800～1200MPa级微合金TRIP钢的研发和激光焊接试验以及具有优良焊接性能和热镀锌性能的新型相变塑性钢的开发进程.     

Macromodelling of Transformation Induced Plasticity combined with Viscoplasticity for Low‐Alloy Steels

Metal forming processes are important technologies for production of engineering metal components. In order to optimize the resulting material properties, it becomes necessary to simulate the entire forming process by taking into account physical effects such as phase transformations. In this work we concentrate on the phase change from austenite to martensite and present a macroscopic material model, which combines the effects of viscoplasticity with the effect of transformation induced plasticity (TRIP). An extensive experimental data basis for a low‐alloy steel is used for parameter identification, thus taking into account the effects of uniaxial compressive and tensile stress on the kinetics of phase transformation at different temperatures. In a finite element simulation the austenite to martensite phase transformation within a shaft subjected to thermal loading is investigated.     

应用马氏体转变分析方法对304不锈钢冷轧板拉深应变的研究

应用马氏体转变分析方法,对304不锈钢冷轧板拉深应变试验过程中拉深件各个区域的应变分布规律、马氏体转变分析、壁厚、硬度变化历史进行了研究;分析304不锈钢冷轧板性能对拉深件应变的影响及用户开裂水槽的应变分布特点;提出了确定拉深成形零部件危险部位的方法和改进措施.     

Weldability of Low Carbon Transformation Induced Plasticity Steel

Transformation induced plasticity （TRIP） steel exhibited high or rather high carbon equivalent （CE） because of its chemical composition, which was a particularly detrimental factor affecting weldability of steels. Thus the weldability of a TRIP steel （grade 600） containing （in mass percent, %） 0.11C-1. 19Si-1.67Mn was extensively studied. The mechanical properties and impact toughness of butt joint, the welding crack susceptibility of weld and heat affected zone （HAZ） for tee joint, control thermal severity （CTS） of the welded joint, and Y shape 60° butt joint were measured after the gas metal arc welding （GMAW） test. The tensile strength of the weld was higher than 700 MPa. Both in the fusion zone （FZ） and HAZ for butt joint, the impact toughness was much higher than 27 J, either at room temperature or at -20 ℃, indicating good low temperature impact ductility of the weld of TRIP 600 steel. In addition, welding crack susceptibility tests revealed that weldments were free of surface crack and other imperfection. All experimental results of this steel showed fairly good weldability. For application, the crossmember in automobile made of this steel exhibited excellent weldability, and fatigue and durability tests were also accomplished for crossmember assembly.     

锰钢板在矿山溜井支护中的应用效果

分析了矿山溜井支护层破坏的原因,阐述了溜井支护方式及锰钢板支护效果,为溜井支护方式的选择提供参考.     

鞍钢先进高强汽车用钢的研制开发

介绍了鞍钢先进高强汽车用钢开发研制情况,包括以980 MPa级DP钢、TRIP钢、TWIP钢和QP钢为代表的热轧、冷轧和热镀锌先进高强钢系列产品,以及鞍钢开发的先进高强钢热镀锌生产技术,并对鞍钢先进高强汽车钢未来的发展方向进行了展望。     

铌的析出行为对形变诱导相变的影响

在Gleeble热模拟试验机上,研究含铌微合金钢中铌的析出物在形变诱导相变过程中的作用机理,结果表明:当加热温度为1000℃时,部分铌的碳化物未溶解于奥氏体中,而加热温度为1100℃时,铌的碳化物能够全部溶解到奥氏体中,含铌微合金钢加热温度范围约在1000～1100℃之间。铌的未溶解碳化物和在冷却过程中析出的碳化物都能作为铁素体形核位置,从而促进γ→α相变的发生。     

Finite Element Modelling of TRIP Steels

A constitutive model that describes the mechanical behaviour of steels exhibiting “Transformation Induced Plasticity” (TRIP) during martensitic transformation is presented. Multiphase TRIP steels are considered as composite materials with a ferritic matrix containing bainite and retained austenite, which gradually transforms into martensite. The effective properties and overall behaviour of TRIP steels are determined by using homogenization techniques for non‐linear composites. The developed constitutive model considers the different hardening behaviour of the individual phases and estimates the apportionment of plastic strain and stress between the individual phases of the composite. A methodology for the numerical integration of the resulting elastoplastic constitutive equations in the context of the finite element method is developed and the constitutive model is implemented in a general‐purpose finite element program. The prediction of the model in uniaxial tension agrees well with the experimental data. The problem of necking of a bar in uniaxial tension is studied in detail.     

Influence of Strain‐Induced Retained Austenite Transformation on the Dynamic Tensile Behaviour of TRIP‐aided Steels

Tensile tests for two commercial TRIP‐aided steels with the compositions of 0.091%C‐1.456%Si‐1.061%Mn and 0.134%C‐1.525%Si‐1.226%Mn in the strain rate range of 10^?4‐10³ s^?1 were performed. Results for a pneumatic indirect bar‐bar tensile impact tester displayed sensitivity of tensile properties to strain‐rate within the testing range. XRD analysis for the relationship between the strain‐hardening exponent and the strain‐induced transformation of retained austenite suggested significant influence of the transformation of retained austenite on their work‐hardening behaviour.     

超轻汽车车体用钢热镀锌的研究及应用现状

综述了超轻汽车车体用钢热镀锌的研究及应用现状,重点介绍了烘烤硬化钢、高强度IF钢、双相钢、相变诱导塑性钢等热镀锌的生产工艺和性能影响因素。     

形变诱导铁素体逆相变过程中的组织及取向变化

 通过对普碳钢Q235在Gleeble1500热模拟机上变形后的微观组织分析,研究了组织中形变诱导的铁素体在变形后保温阶段转变为奥氏体的逆相变现象;并利用背散射电子衍射(EBSD)技术分析了晶粒取向变化。结果表明,在变形后的保温过程中,形变诱导的铁素体先逆相变为奥氏体,同时伴随着诱导铁素体晶粒的长大;然后随着变形后保温时间的延长,逆相变后的奥氏体由马氏体相变逐渐过渡到铁素体的平衡转变,相应地铁素体由具有少量亚结构的形变诱导铁素体逐渐转变为具有较多亚结构的先共析铁素体。     

Transformation Conditions ‐ Microstructures ‐ Mechanical Properties Relationship in 0.60%C Hypoeutectoid Steel

The relationship between transformation conditions, microstructures and mechanical properties were investigated on a 0.60%C hypoeutectoid steel, which has predominantly pearlitic microstructure. The steel had been austenized at 850‐1050 °C and then isothermally transformed at 570‐660 °C. Afterwards, the microstructures were analyzed by optical microscope, scanning electron microscope, and quantitative metallography. And the mechanical properties were determined. The results indicated that the interlamellar spacing, the pearlitic colony size and the proeutectoid ferrite content follow a linear relationship with the reciprocal of the undercooling, and the strength, the hardness and the toughness follow a Hall‐Petch type of relationship with the inverse of the square root of the interlamellar spacing. Besides, the stress condition should be taken into account during analyzing the effect of the interlamellar spacing on the mechanical properties. The results have been explained on the basis of transformation conditions ‐ microsturctures ‐ mechanical properties ralationship.