Influence of Pre‐Straining and Bake Hardening on the Strain Rate Sensitivity of Automotive Sheet Steels

The present investigation deals with the influence of pre‐straining with or without bake hardening on the strain rate sensitivity of automotive sheet steels in typical crash conditions. The strain rate sensitivity m has been determined by means of dynamic tensile tests in the strain rate range 0.005‐1000 s^?1 and in the temperature range 233‐373K. A bake hardening heat treatment at 170 °C for 20 min without pre‐straining does not influence the m‐value in comparison to the base material condition. A small pre‐straining near plane strain condition, as commonly found in outer door panels, or a 10% uniaxial, plane strain and biaxial pre‐straining, as typically used in formed automotive crash components, without bake hardening does not affect the m‐value of sheet steels in comparison to the base material condition. Uniaxial 2% to 10% pre‐straining, longitudinal or transverse to rolling direction with subsequent bake hardening, does not clearly change the m‐value in comparison to the base material condition either. Small differences in the strain rate sensitivity behaviour are rather attributed to experimental scattering without real physical background.     

提高硫酸装置的原料烘矿效率的方案

随着云浮广业硫铁矿企业集团公司化工厂8万t硫酸装置产能的扩大,原料需要增加,针对如何提高原料的烘矿效率的问题展开讨论和研究．确保了装置的高效开工率。     

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.     

延长工频感应熔化炉炉龄的实际操作方法

介绍了工频感应熔化炉通过改进筑炉和正确使用工频炉来延长炉龄的方法。     

高性能面砖的生产工艺

介绍了一种高性能面砖(釉面砖)的生产工艺.通过调整配料及其化学组成,在一定温度下,采用低温素烧高温釉烧,可烧制高性能面砖,特别对降低砖的水化膨胀率.改善抗冻性和耐碱性能收到明显的效果.     

微波炉法快速测定红粘土含水量的试验研究

对含水量的测定方法进行了分析比较,指出微波法具有广泛的应用前景,探讨了微波加热法的基本原理及试验过程,比较了微波加热法与标准烘干法试验数据,对微波炉法快速测定红粘土含水量的试验结果进行了回归分析,结果表明微波炉法测定红粘土含水量具有精度高、效率高的优点。     

Effects of Rolling Parameters on Texture and Formability of High Strength Ultra-Low Carbon BH Steel

 The effects of hot rolling and cold rolling parameters on texture and r (plastic strain ratio) value of high strength ultra low carbon bake hardening (ULC-BH) steels are studied with orientation distribution function (ODF) structural analysis method. After hot rolling, the high strength ULC-BH steel sheet has weak γ-fiber with uniform orientation distributions, and weak α-fiber, of which {445}<110> component forms a high intensity peak at coiling temperature of 750 ℃. After cold rolling, both {111}<110>-{111}<112> intensity on the γ-fiber and {111}-{112}<110> intensity on the α-fiber enhanced. As a result of substitutional solute elements Mn and P being added to the steel, strong {112}<110> deformation texture component is observed on α-fiber, especially at 80% cold rolling reduction, and this leads to the strong {111}<112> recrystallization texture after annealing. The increase of cold rolling reduction shifts the maximum intensity on the γ-fiber from {111}<112> to {111}<113>. After annealing, a very strong γ-fiber is obtained, with intensity peak at {111}<112> component when cold rolling reduction reaches 80%. Increasing coiling temperature and cold rolling reduction improve γ-fiber intensity and r value, resulting in good deep drawability.     

The effect of soft bake on adhesion property between SU‐8 photoresist and Ni substrate by molecular dynamics simulation

SU‐8 photoresist is a negative, epoxy‐type, near UV photoresist and is commonly used in micro electro mechanical systems (MEMS) and other thick resist application fields. However, poor adhesion strength between SU‐8 photoresist and metal substrate makes it difficult to bind, even contributes to the lithography failure. This significantly restricts the improvement of image resolution and depth‐to‐width ratio. As soft bake temperature and time are important for the interfacial adhesion property, in this article, molecular dynamics (MD) simulation was performed to investigate the effects of these two parameters on adhesion property between SU‐8 photoresist and Ni substrate. According to the adsorption theory, the simulation results were analyzed and validated by experiments. It is shown that with increasing soft bake temperature the adhesional work firstly increases and then decreases, and with increasing soft bake time the adhesional work decreases. This study provides theory basis for the confirmation of soft bake parameters. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of Thermo‐Mechanical Processing Parameters and Chemical Composition on Bake Hardening Ability of Hot Rolled Martensitic Steels

In recent years, the increasing demand for advanced high‐strength steels (AHSS) has mainly been driven by the automotive industry and the need to reduce weight and to improve safety. Besides good ductility and high strength, AHSS have a high bake hardening and ageing effect, giving additional contribution to the strength of structural parts, subjected to the paint baking process. This paper investigates their bake hardening behaviour in dependence of hot rolling parameters and chemical composition, however, focussing on martensitic steels. Tosimulate the finishing steps of the hot rolling process with slight changes in reduction and temperature and their influence on the final mechanical properties of hot rolled martensitic steels, different thermo‐mechanical paths were applied. The increase in strength due to bake hardening was determined for different thermo‐mechanical schedules. Additionally, samples of different chemical compositions within the characteristic industrial tolerance range were studied under variation of pre‐load conditions, simulating the thermo‐mechanical hot rolling process. The samples were then subjected to bake hardening to study the varying chemical composition on this effect. Furthermore, the local use of bake hardening and ageing in hot rolled multiphase steels was investigated. It could be shown that characteristic values integrally describing the ageing effect, depend on the deformation path and the degree of pre‐strain, as well as on temperature and duration of the subsequent heat treatment. This partial ageing is stable and has a potential to be used for local strengthening of the steels.     

Evolution of appearance profile of hot-dip galvanized car-body steel sheet during deformation process

In recent years,the waterborne free intermediate coating process has been widely used in the automotive industry.Because the baking times and coating thickness are decreased,the surface covering capability of the painting process is reduced,which directly affects the appearance quality (long-and short-wave values) of the body paint.Thus,there are correspondingly higher requirements for the white body surface profile prior to painting.The surface profile of the white body is mainly affected by the plate material,the surface profile,and the deformation process.So,the change rule for the surface profile during deformation of the steel plate is a key factor in coating appearance optimization.In this paper,we first analyze the typical deformation of the outer cover of a car body.Then,we examine the change tendency of the surface profile of steel plates with respect to different deformation rates,specifically for a steel plate comprising a hot-dip galvanized bake-hardened steel sheet.Based on our analysis of the influence of the deformation on the coating appearance,we selected 3％,5％,and 8％ deformation rates in this research.We found the roughness (Ra) value in the typical deformation range (3％-8％) of the car body to exhibit a decreasing trend at first and then an increasing trend.The Ra value of the 8％ deformation is not more than the original plate test value.When the Pc value of the original plate is in the lower range (about 60),it exhibits a slight increasing trend in the deformation process (3％-8％).And when the Pc value of the original plate is in the higher range (about 120),it exhibits no increasing trend in the deformation process (3％-8％).In contrast,the waviness (WCA) value in the car body's typical deformation range (3％-8％) shows a significant growth trend.