碳含量对新型Fe-Ni-Mn-Si-C系TWIP钢组织和力学性能的影响

通过光学显微镜、X射线衍射和透射电镜等方法研究了碳含量对Fe-Ni-Mn-Si-C系合金微观组织和力学性能的影响。结果表明:Fe-Ni-Mn-Si-C系合金的主要塑性变形机制为孪生诱发塑性(TWIP)效应。碳的质量分数由0.70%增加至0.98%,合金的屈服强度和抗拉强度分别由391 MPa和860 MPa增大到458 MPa和974 MPa,伸长率由63.6%提高到69.2%。随着碳含量的提高,Fe-Ni-Mn-Si-C系合金出现明显的动态应变时效现象。Fe-15Ni-12Mn-2.5Si-XC合金具有良好的应变硬化能力,随着碳的质量分数提高至0.98%,最大应变硬化指数达到0.73。     

固溶温度对节约型双相不锈钢TRIP/TWIP行为的影响

 通过微拉伸、电子背散射（EBSD）、透射电子显微镜（TEM）等手段,研究了具有亚稳奥氏体相的节约型双相不锈钢在1 000～1 200 ℃范围内不同固溶温度下的组织与性能的演变规律;探讨了固溶温度对形变诱导塑性（TRIP/TWIP）的作用机制。结果表明,随着固溶温度的升高,抗拉强度与伸长率均先升高后降低,而亚稳奥氏体相比例由74%（1 000 ℃）降低到37%（1 200 ℃）;1 050 ℃固溶时,试验钢表现出最佳综合性能,抗拉强度达到960 MPa,伸长率达到62%,强塑积达到60 GPa·%。在经拉伸变形的微观结构中形变诱导马氏体与形变孪晶共存,表明试验钢中亚稳奥氏体相的变形机制主要受TRIP及TWIP共同控制,从而导致其塑性变形过程呈现多阶段应变硬化特征,而钢中铁素体相的变形机制主要变形为位错的滑移。     

低碳Si-Mn系TRIP钢的动态拉伸性能

在气动式间接杆杆型冲击拉伸实验机上对工业生产的两种低碳Si-Mn系TRIP钢不同应变率下的高速冲击拉伸性能进行了研究,并和静态拉伸性能进行了比较.结果表明,两种钢的室温拉伸性能随应变率变化具有相同趋势,但动态下的应变率敏感性比静态下的要高得多.由于TRIP钢组织中残余奥氏体的变形诱发向马氏体的转变显著改善了材料的塑性.     

Fe Mn C系TWIP钢的拉伸应变硬化行为研究

 通过试验研究了Fe Mn C系TWIP钢的拉伸应变硬化行为。结果表明：试验钢在拉伸过程中的应变硬化表现为阶段性多n值行为。其应变硬化机制有两种：在0.4%～3%的应变区间为位错强化阶段,10％～50%的应变区间为孪晶强化阶段。在这两个区间内n值皆为定值,而在4％～10％的应变区间n值呈不断上升趋势。     

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.     

Effects of Pre-strain and Temperature on Bake Hardening of TWIP900CR Steel

The effects of pre-strain and baking temperature on bake hardening behaviour of TWIP900 CR steel were investigated.The results reveal that the bake hardening process contributes to an increase in yield strength up to 65 MPa at the baking temperature of 200℃.The difference in yield strength between baking temperatures of 170 and 200℃is almost insignificant.It is clearly observed that baking at a high temperature does not result in a significant increase in yield strength.For a reasonable bake hardening,agood combination of pre-strain and baking temperature is necessary.Besides,the toughness of the material is found to decrease with increasing pre-strain.     

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Forming limit diagram (FLD) of cold- rolled TRIP steel was established by experiments. The microstructures of samples before and after deformation were examined by metalloscopy and scanning electron microscopy and at the same time the contents of retained austenite after different strain ratios were measured by X- ray diffraction. The results show that the ultimate strain under plane strain state(FLD0) is 0. 397. With the strain ratio increasing, strain path changes from uniaxial stretching to plane strain and then biaxial stretching and the transformation amount of residual austenite increases gradually. Compared with dual- phase steel, the higher FLD0of TRIP steel is ascribed to TRIP effect and necking area is wider during deformation.     

亚稳态奥氏体钢的形变硬化

研究了亚稳态奥氏体不锈钢的形变硬化,结果表明：低温下由于产生应变诱发马氏体相变,其拉伸曲线硬化阶段呈现Ｓ形,硬化指数ｎ为非恒定值,硬化率与硬化指数ｎ随应变量的增加表现为抛物物型。     

碳含量对Fe-Ni-Mn-Si-C系TWIP钢应变硬化行为的影响

采用单向拉伸、金相组织观察、TEM等方法,研究了3种不同碳含量Fe-Ni-Mn-Si-C系TWIP钢的拉伸应变硬化行为。研究结果表明,随着碳含量的增加,合金的强度和伸长率均提高,当碳质量分数为1.0%时,该TWIP钢具有较好的综合力学性能,强塑积达到83 160 MPa.%。3种TWIP钢的真应力-真应变曲线均不完全遵...     

高性能钢铁材料在实体膨胀管领域的应用前景

实体膨胀管技术作为一项先进的钻井技术,其技术优势在套损修复、固井、完井等领域逐渐显露出来。管材的设计研发是实体膨胀管3大关键技术之一,也是制约膨胀管应用的主要技术瓶颈。介绍了实体膨胀管的技术原理,综述了国内外实体膨胀管管材的研发现状,重点分析了实体膨胀管管材所需的力学性能。在此基础之上,着重介绍了现有的双相钢、TRIP-assisted钢以及高锰奥氏体TWIP/TRIP钢3种高塑性高强度钢铁材料的力学性能特点、材料设计原理及热处理工艺,对它们作为实体膨胀管管材使用的可行性进行了讨论。     

高锰奥氏体TRIP/TWIP钢的组织和力学性能

研究了两种不同锰含量的高锰奥氏体钢在室温拉伸变形过程中力学性能和组织的变化.结果表明,随着钢中锰含量的变化,实验钢在流变应力的作用下出现相变诱导塑性的TRIP效应和孪晶诱导塑性的TWIP效应.在1×10-3 s-1的初始应变速率条件下,锰的质量分数为23.8%的实验钢可达到666 MPa的抗拉强度和67%的伸长率,而锰的质量分数为33%的实验钢可达到540 MPa的抗拉强度和97%的伸长率.并且在10-3～10-1 s-1的初始应变速率范围内,实验钢的抗拉强度对于流变应力不敏感,而实验钢的塑性则表现出一定的应变速率敏感性.由于该钢具有较好的综合力学性能,有望作为新一代高强度、高塑性汽车用钢.     

New Steel Solutions for the Worldwide Car Industry

Steel development as a scientific process requires both metallurgical background and state‐of‐the‐art analysis and testing technology. In the future, we expect much shorter development periods owing to the increased use of computer simulation. Successful developments are the result of consistent team work, both in the steel companies and in the cooperation with automobile producers. Customer involvement at an early stage permits to speed up the development by simultaneous engineering. The success of a material in the market depends more and more on its comprehensive definition by relevant parameters. Scientific technical services form a part of marketing. Modern high‐strength steels are enjoying success and are finding ever more application in new cars.     

TRIP780钢贝氏体区等温转变的规律

采用 DIL805L 型淬火膨胀仪测定了 C-Si-Mn 系 TRIP780钢贝氏体区等温转变曲线。依据膨胀量-时间曲线,计算出相变过程中的组织转变率,分别统计不同工艺下的转变率以及对应的时间关系。研究了 TRIP 钢在等温转变时的相变规律。结果表明：加热温度相同时,贝氏体转变速率随着等温温度的升高而提高,但总转变率降低;在等温温度相同时,加热温度越高,转变率也相应增大。在贝氏体等温转变图上,转变终了线为 C 形,即存在一个鼻尖,对应于最短的转变时间。     

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。     

Study of Bake Hardening Effect on Laser Welded Hot Rolled Ferrite‐Bainite Dual Phase Steels

The influence of bake hardening (BH) effect on laser welded hot rolled ferrite‐bainite dual phase steel (FBS) with respect to the process conditions was investigated. The samples were firstly laser welded and then pre‐strained. Pre‐strained the samples with defined degrees of deformation and a subsequent aging treatment leads to enhanced hardness and strengthening for both conditions. The microstructure of the fusion zone (FZ) and heat affected zone (HAZ) was studied. A high volume fraction of martensite could be observed in the FZ as well as in the HAZ. Both steels exhibited a clear BH effect in both, the as‐received and the laser welded conditions. The BH effect is more pronounced in the pre‐strained laser welded condition.     

In‐situ Synchrotron XRD Analysis of the Effect of Static Strain Aging on the Elasto‐plastic Transition in CMnSi TRIP Steel

In situ synchrotron X‐ray diffraction was used to investigate the martensitic transformation kinetics, lattice straining and diffraction peak broadening in cold‐rolled TRIP steel during tensile testing. Direct evidence of stress‐strain partitioning between different phases, dislocation pinning and differences in yielding behaviour of the different phases were clearly observed. The TRIP steel was subjected to a bake‐hardening treatment and a pronounced static strain aging effect was observed. In the present work, the martensitic transformation kinetics and the elastic micro‐strain evolution for both ferrite and retained austenite during the elasto‐plastic transition are reported with an emphasis on bake‐hardening with and without pre‐straining.