Advanced HSLA Steels for Automotive Use

Characteristic HSLA steels for automotive use are introduced in which both of precipitation and microstructure is controlled to obtain suitable mechanical properties.For outer panels such as fender,the combination of low yield strength,high tensile strength and deep-drawability were realized by controlling the distribution of NbC and precipitation free zone.The other steel,developed for chassis parts such as lower arm,utilizes extremely fine interphase precipitation to obtain high yield strength and excellent hole expansionability.Both steels have contributed to the reduction of weight in car body.     

Improvement of Drawability at Room Temperature in AZ31 Magnesium Alloy Sheets Processed by Equal Channel Angular Rolling

A new rolling process, so-called as equal channel angular rolling (ECAR) process, for fabricating the magnesium alloy sheets with an enhanced formability at room temperature is introduced. The ECAR device was designed so that it could feed the sheet with the preheated temperature of 673 K in a continuous manner at a relatively high speed of 0.43 m/s. A significant amount of the shear deformation could be achieved by passing the sheet through the mold with the oblique angle of 115°. The x-Ray spectra were examined to analyze the crystal orientation of the sheets, which indicates that the crystal orientation with non-basal plane was fabricated after ECAR processing. The grain was not refined and plenty of twins were brought out because of the low-shear deforming temperature. The high stress and low ductility for the ECARed specimens can be related to the presence of twins. In spite of having the similar optical microstructure, the elongation to failure for the ECARed specimens after annealing was above 33%, which was larger than that of about 20% for the as-received/annealed specimens. And the drawability for the ECARed/annealed specimens with the Erichsen value of 6.24 mm and the limiting drawing ratio of 1.6 can be obtained, which is improved dramatically than that of 4.18 mm and 1.2 for the as-received/annealed specimens, respectively. These can be related to the rotation of (0002) basal plane toward the rolling direction because of the shear deformation induced by ECAR process.     

汽车用铝合金板拉深性能评估参数

为了准确地评估汽车用铝合金板的拉深性能,在单向拉伸试验、平面应变拉伸试验和圆筒件拉深试验获得的样本基础上,采用回归分析方法,全面地分析了汽车用铝合金板各种材料性能参数与其拉深性能之间的对应关系。研究表明:在所给出的材料性能参数中,xb值(平面应变抗拉强度与单向抗拉强度之比)对极限凸模行程的相关性最为显著,其次是硬化指数n及宽度颈缩率ψ等参数,而厚向异性系数r与铝合金的拉深性能并不相关。上述结果表明,在评估汽车用铝合金板的拉深性能时,使用xb值为评价指标最为准确。     

顶煤块度预测方法与应用

以岩(煤)体裂隙网络模拟技术为基础，推导了放顶煤采场项煤三维块度预测法的求解过程与计算公式，提出了顶煤可放性块度评价法及其对应的评价分类指标，用此法来评价顶煤可放性具有直观、可靠性高、易于接受的优点。     

钢板深冲性与织构研究的进展

对近年来深冲钢板在织物研究方面如（1）铁素体区轧制的可行性及其工艺制度变形织构的影响。(2）冷轧织构的组成；（3）再结晶织构与前续工序的关系及形成理论；（4）织构在板材厚度方向的表现特点等作了评述。     

铝-钢复层板材的力学性能与拉深成形性能

对一种国产铝-钢复层板材的力学性能及拉深成形性能进行了试验研究。研究了退火温度对该材料力学性能的影响及两种板材复合后表现出来的各向异性。根据圆筒形拉深试验的结果,讲座了凸模圆角半径R p对板材极限拉深比R max的影响并由此发现铝-钢复层板材R max值与铝或钢所处的内外面位置有关。分析了造成这种现象的原因。     

Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed InterstitialFree Steel

The processing conditions of the texture formation and deep drawability of a TiIF steel strip hotrolled in ferritic region and subsequently annealed were investigated. The rvalue increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the rvalue is raised up to 175, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the rvalue is below 10 in the case of unlubricated rolling. The Xray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong {111}∥ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of {110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and {110}∥ND recrystallization texture is strong, which deteriorates the formability.     

IF钢搪瓷板析出相的研究

2001年武钢开始生产冷轧IF钢搪瓷板，为了解IF钢瓷板成分设计的合理性和优化生产工艺，在透射电镜上观察了钢中析出相的形态，用能谱仪分析了析出相的成分，并对析出相的平衡进行了计算。研究结果表明：IF钢搪瓷板中的析出相主要为TiS、Ti4C2S2、TiN以及细小的FeTiP相；钢的碳含量增加和低的热轧加热温度有助于Ti4C2S2相的析出；钢中富余的固溶Ti将在退火温度下形成FeTiP相，粗大的TiS、Ti4C2S2析出相，既使钢板具有良好的涂搪性能，又对钢的深冲性能无有害影响，因此，IF钢搪瓷板具有很好的涂搪性能和深冲性能。     

Melt processability of polytetrafluoroethylene: Effect of melt treatment on tensile deformation mechanism

It is widely accepted that the melt processibility of polytetrafluoroethylene (PTFE) is poor. In this article, a high‐molecular‐weight PTFE was extruded smoothly with a modified die; and critical shear rate could be raised to 4 s^?1, using a die with L/D (length to diameter) ratio of 200. Meanwhile, we compared the current PTFE fiber spinning method with melt spinning to investigate the effects of high‐temperature treatment on the drawability of PTFE and found that the processing sequence could play a key role. The deformation imposed before or after the high‐temperature treatment could determine whether the fibrillation can be achieved continuously and effectively. Based on the experiment phenomenon, together with the results of differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy characterization, we proposed a model to describe the submicron structural change of PTFE during extension. From this model, the fundamental mechanism for the poor melt processibility of PTFE was elucidated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012