深冲冷轧板塑性应变比及各向异性与织构相关性分析

采用X射线衍射三维取向技术(ODF)并结合力学性能试验及金相组织观察,着重研究了不同冲压级别的深冲冷轧板塑性应变比(r)及平面各向异性系数(Δr)与织构之间的相互关系。从织构角度探讨了深冲冷轧板r和Δr差异的原因。研究结果表明织构的组分、含量及取向密度与深冲板板的r值和Δr具有较强的相关性和一致性。获得高取向密度的γ纤维织构({111}//ND)有利于改善深冲钢板的r值,是提高材料深冲性能的有效手段。     

冷轧板塑性应变比对凸耳率影响规律的研究

冷轧板料塑性应变比r值存在各向异性,容易造成冲压凸耳现象。利用Dyna Form数值软件,通过输入不同的材料参数,定量分析了不同r值、不同Δr值对凸耳率影响的规律。结果显示:相同r下,凸耳率随着Δr的增大而增大;相同Δr的情况下,凸耳率随着r的增大而减小;凸耳率与Δr/r值成指数关系,Δr/r值定义为相对塑性应变比各向异性度。     

IF钢平面各向异性与制耳效应的研究

分析了提高IF钢的冷轧压下率、调整Ti和Nb含量等方式对IF钢平面各向异性性能及后续深冲过程制耳的影响。结果表明,冷轧压下率从70%提高至82%,IF钢的各向异性性能得到改善;在冷轧压下率为82%时,加入适量Nb元素代替部分Ti,Δr和r值下降的同时制耳指数增加;制耳是塑性应变比和平面各向异性度综合作用的结果。     

铝含量对GCr15钢带织构和深冲性能的影响

在杭钢集团大生产的条件下,分析了不同铝含量对退火后GCr15钢带的织构、金相组织、晶粒取向、硬化指数n和塑性应变比r以及凸耳指数Δr的影响。试验结果表明:在[Al]s的质量分数为0.017%~0.027%时,铝对高碳的GCr15钢带的深冲成型性能影响规律与铝对低碳钢板基本一致,随着钢中铝含量的升高,r值升高,且{111}面有利织构含量增加,但相同铝含量下GCr15钢的r值比低碳钢却要小很多,n值则相差不大,Δr指数比低碳钢更小,晶粒取向也有明显的区别,说明高碳的GCr15钢各向性能比较均匀,能满足一般用途的深冲成型要求。     

用塑性应变比及凸耳参数评定P1钢的压延成型性能

对五种规格加磷钢深冲薄板进行了r值及Δr值测试,以便获得最佳塑性应变比和凸耳参数的轧制工艺。结果表明,采用72%左右和冷轧形变量轧制的深冲薄板,不仅能获得较高的塑性应变比,也能获得较理想的凸耳参数。文内对加磷钢薄板在不同应变水平下r值取值问题进行了探讨,认为取工程应变e=15%处的r值,是十分可靠的。本文还分析了一点宽度测量法(用岛津AG-25TA电子拉伸试验机)与标准法(三点宽度测量法)测定r值造成差异的原因。指出,只要试样的宽度加工满足标准规定的精度要求,采用一点宽度测量值是可靠的。     

深冲钢板的主要织构对塑性应变比的影响

总结了深冲钢板织构影响塑性应变比的研究方法,分析了８种主要织构对深冲钢板塑性应变比的影响特点,探讨了深冲钢板△ｒ值偏大时的织构原因,可为深冲钢板塑性应变比的改善提供依据。     

铜对08A1冷轧薄板再结晶织构的(井彡)响

引言低碳冷轧钢板的主要使用性能是深冲性能,而决定深冲性能的主要冶金因素是再结晶织构,这已为近十余年来大量的生产实践及科研工作所证实。深冲性能所要求的有利织构应保证薄板具有垂直塑性各向异性,亦即要求薄板在厚度方向的强度大于平均强度,这样就可以保证薄板在冲压成形时主要由板面内的塑性流动完成而不易减薄,因而就可减少冲压破损率。从晶体学考虑,为获得这样的塑性各向异性需要再结晶后各晶粒的<111>晶轴垂直     

热轧温度对3004H19易拉罐各向异性和织构的影响

采用ＯＤＦ织构分析和各向异性测试技术,研究了热粗轧温度和热精轧温度对３００４Ｈ１９易拉罐用特薄铝板的各向异性和织构的影响。实验结果表明：当热粗轧温度≥７３３Ｋ,热精轧温度≥６２３Ｋ时,３００４Ｈ１９薄板中具有强的铜织构和较强的立方织构,各向异性小,深冲性能好,制耳率低,达到国际先进水平;较高的热轧温度减弱了薄板冲杯时４５°方向制耳的形成;当成品板中有较强的立方织构与变形织构共同存在时,成品板材的各向异性和制耳率很小,深冲过程中才有可能形成８个小制耳。     

中间退火对3004合金组织,织构和各向异性的影响

本文采用ODF织构分析、TEM、偏光金相及性能测试等手段,研究了高温快速退火和常规退火两种不同的中间再结晶退火制度对3004铝合金冷轧薄板显微组织、织构、力学性能及各向异性的影响.实验结果表明:采用高温快速退火有利于强烈立方织构的获得和成品板材中显微组织的改善,大变形量冷轧后仍保留有少量立方织构.各向异性较小;而经常规中间退火的板材立方织构较弱.冷轧后没有发现立方织构,深冲时只出现与轧向呈45°的制耳.而不是前一种板材的0°/90°和45°方向共存的八个小制耳.织构测定的结果与深冲时的制耳行为是一致的.     

D08RE热轧深冲钢的试验研究

本文总结D08RE热轧汽车深冲薄板添加稀土改善深冲性能的试验过程。试验结果表明:钢包吹氩插入法加稀土操作简便,稀土夹杂球化率高。D08RE钢成形性良好,力学性能稳定。负载疲劳寿命达到同类产品先进水平。以形变硬化指数(n)值,塑性应变比(r) 值和面内各向异性(△r)值,探讨稀土元素对D08RE钢深冲性能的影响,经用户实际使用后认为,D08RE钢能较好地满足我国汽车工业生产的要求。     

Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.     

Elevated temperature plastic anisotropy of Ti-6AI-4V plate

The influence of temperature on the planar and normal anisotropy parameters (ΔR andR, respectively) for mill annealed, duplex annealed, and cross rolled Ti-6A1-4V plate was investigated from 25 to 704°C (77 to 1300°F). Both parameters were assessed in terms of the plastic strain ratio (R), ratio of width to thickness strain at maximum load (~0.065 longitudinal strain) in tensile specimens oriented at 0, 45, and 90 deg to the rolling direction, and correlated with texture and microstructure. With increasing temperature, plates characterized by alpha deformation type basal plane textures exhibited significantly larger anisotropy variations than plate with a beta transformation type texture. This behavior was related to the degree of textural randomness and to a thermally induced transition in primary deformation mode from twinning to slip. Depending on texture, the results strongly suggest that working temperature may be utilized advantageously to alter the plastic anisotropy of Ti-6A1-4V plate for improved formability in a given fabrication operation.     

Effects of Rolling Processes on Yield Ratio and Formability of Hot Rolled Gas Cylinder Steel

 Deep drawing properties of hot rolled gas cylinder steel was investigated by using HP295 steel in terms of microstructure, texture, yield ratio, plastic strain ratio (r-value) and plastic anisotropy (Δr). The grains in the hot strip were largely equiaxed, and the texture was weak, containing α- and γ-fibre. Reheating temperature, finish rolling temperature and cooling rate after rolling influenced the ferrite-pearlite band formation significantly, and the yield ratio increased steeply with decreasing coiling temperature below 630 ℃. The anisotropy is relatively high due to retained severe ferrite-pearlite band. A mechanism of the band formation due to manganese segregation is elaborated and confirmed validly, from which the measures to avoid the band formation are worked out. Rolling parameters have been optimized by the measures, and industrial production of the gas cylinder steel has been made possible with much improved r-and Δr-values, while meeting other specifications.     

Plastic anisotropy in a superplastic Al-Li-Mg-Cu alloy

The plastic anisotropy of AA8090 Al-Li-Cu-Mg alloy sheet has been evaluated by tensile testing and by deep drawing at temperatures in the range 200 °C to 525 °C. At temperatures of about 500 °C and strain rates of about 10^-3 s^-1, this material exhibits a high strain-rate sensitivity of flow stress which reduces any tendency to strain localization in stretching and allows so-called superplastic forming of the sheet. Most models of the material behavior in this regime require highly inhomogeneous deformation on the scale of the material’s grain size. The plastic anisotropy measured in the superplastic regime was similar in form, though of reduced magnitude, to that measured under conditions associated with a much smaller strain-rate sensitivity. Homogeneous slip models predict the correct form of anisotropy, and inclusion of slip-rate senitivity can reduce the magnitude of anisotropy predicted but not sufficiently to give good correlation with the experimental results unless very high values are used. The development of the preferred crystallographic orientation in deep drawing has also been examined. The predictions of homogeneous slip models correlate quite well with experimental results at low temperatures, but the situation is more complex in the superplastic regime where, although there is some evidence of texture changes as predicted, there is a general reduction in the intensity of preferred orientation with deformation. However, the results indicate that a greater contribution of homoeneous slip deformation is involved in superplastic deformation than is assumed in some models of superplasticity.     

Deep‐drawing quality of cold rolled sheet made of ferritically rolled hot strip

In the so‐called ferritic rolling the finishing is shifted down into the temperature region of ferrite, which enables a production of thinner hot strips (compared to the conventional hot rolling in austenite) with a changed texture development. The present study is focused on the effect of the process parameters of such initial warm rolled hot strips on the texture formation and hence on the deep‐drawing quality of the final cold strips. A special attention is given to the transmission of the hot strip texture to the cold strip. The investigation was carried out on commercial IF‐ and ELC‐steels by a laboratory simulation with the hot deformation simulator Wumsi (rolling simulated by the plane strain compression test). It was possible to optimize cold rolling and subsequent annealing by means of the measurements of the texture development during the ferritic (warm) deformation as well as the parameters of the processing route of such special production of cold strips by means of the calculation of r‐values. If compared with the conventional processing route, a considerable improvement of deep‐drawability with a diminished earing is achievable especially with the IF‐steel.     

Deformation Inhomogeneity and Texture Development brought about in Steel Strip by Multi‐Step Cold Rolling

Predicting the microstructure obtained in cold‐rolled strips is of major importance with regard to optimizing the production of deep‐drawing steels with high and defined mechanical and technological properties. By using the hydrodynamic rolling theory of A. Kneschke, it has been possible to determine the effects of the most important rolling parameters and also of the rolling strategy on the velocity field and on the in‐homogeneous distribution of deformation over the strip thickness. Rolling on experimental laboratory facilities has provided the opportunity to observe the texture evolution. The tests were carried out on two deep‐drawing steel grades IF and ULC. The initial thickness of the strip samples was 3.0 mm. The textures were determined at 3 locations over the strip thickness by means of pole figure measurements according to the X‐ray diffraction method.     

冷轧深冲用钢生产工艺改进

冷轧深冲用钢通过试制改进后采用无间隙原子钢材质,并对热轧工艺、冷轧工艺、退火工艺等进行调整。工艺调整后材料具有高的塑性应变比、高的应变硬化指数、低的屈服强度,使材料具有优良的成型性能,最终产品满足了用户的使用要求。     

Texture in deep drawing columbium (Nb)-treated interstitial-free steels

The development of the crystallographic texture in hot-rolled, cold-rolled, and recrystallized Cb-treated interstitial-free steels was investigated using the crystallite orientation distribution analysis as well as X-ray pole figures. The influence of chemical composition of the steel and processing variables on texture and on normal and planar anisotropy of the γ-value of cold-rolled and annealed sheet are discussed and compared with those of aluminum-killed deep drawing steels. While, in terms of ideal orientation components, the re-crystallization texture of aluminum-killed steels can be described as having significant amounts of {lll}〈110〉 and {lll}〈112〉 components, Cb-treated steels show these components and in addition even stronger {554}〈225〉 and {322}〈296〉 components. Distinctions in the hot-rolled texture, the cold-rolled texture, and the recrystallization texture are described. Cb-treated steels have an entirely different planar distribution of γ values or plastic strain ratios compared with aluminum-killed steels. The resulting average γ value, γ_m, is significantly higher for Cb-treated steels and results in superior deep drawing characteristics. A. ELIAS is deceased.