新一代高强塑性钢的开发与应用

为满足汽车、建筑、能源等工业对材料强度级别和使用性能不断提高的要求,世界钢铁业正在开发新一代高强塑性钢。基于先进高强度钢AHSS汽车板,高强度抗震建筑用钢和高等级管线钢的开发,讨论了新一代高强塑性钢的主要技术特征,包括使用性能（成形性、抗冲撞能力、抗震性能、抗皱能力）超载下的形变能力,对塑性指标"（均匀延伸率、n值、屈强比）的要求、复相组织与残余奥氏体的强塑化机理、关键工艺技术以及新产品新技术的发展方向,同时考虑到对强韧性和焊接性能的要求,讨论了热变形奥氏体动力学模型、高韧性焊接热影响区HAZ的细化韧化以及硫含量的影响与控制。     

先进短流程—深加工新技术与高强塑性汽车构件的开发

在近年来国内外薄板坯连铸连轧TSCR和先进热成形处理AHFT技术发展的基础上,提出了先进的短流程与深加工技术相结合的工艺途径,为高强塑性汽车构件的生产制造开发了一种高效率、低能耗、低排放、低成本的新工艺。首先采用先进短流程工艺,包括以CSP、FTSR、ISP半无头轧制为主要特征的第2代TSCR技术和以ESP无头轧制技术为主要特征的第3代TSCR技术,生产高强度薄规格汽车板作为热冲压成形的原料; 然后采用先进热成形处理AHFT技术,对短流程薄规格热轧酸洗板进行热冲压与热处理相结合的深加工,制作高强塑性汽车构件。本文简要介绍了短流程薄板坯连铸连轧TSCR技术的发展,先进热成形处理AHFT技术的强塑化工艺与主要技术特征。讨论了采用短流程TSCR新工艺生产先进高强度钢AHSS薄规格汽车板,为先进热成形处理AHFT提供热冲压成形板料的主要技术关键。介绍了在超短流程的双辊薄带连铸工艺线上开发高强塑性TWIP钢的试验进展。短流程TSCR新工艺与先进热成形处理AHFT深加工新技术相结合,开发与生产超高强塑性汽车构件,需要钢铁与汽车行业的密切合作。这项短流程—深加工新技术不仅可以满足新一代汽车对轻量化节能减排和抗冲撞安全的要求,而且可以显著降低汽车板构件生产制造过程中的能耗与温室气体排放。     

我国汽车板生产现状及展望

介绍了当前汽车业主流车型对汽车板的要求和使用情况,新一代超轻钢和未来钢汽车在节能、环保、安全、舒适方面的结构特征,及其对各种新型汽车材料的技术要求和近期市场需求。概述了我国汽车板生产现状和宝钢、武钢、鞍钢、首钢等主要厂家的技术和产品发展。介绍了高品质和高等级汽车板的发展趋势与关键技术,包括冷轧汽车外板的典型表面缺陷形成机理与工艺控制,先进高强度钢AHSS汽车板的强塑化机理与连续退火工艺控制,以及热镀锌高强钢汽车板的发展。指出了利用短流程CSP－冷轧－罩式退火工艺中AlN固溶析出和{111}//RP织构发展,生产高r值冷轧深冲板的工艺优势。简述了汽车板深加工技术和产品开发的新进展——热冲压成形。指出我国汽车板生产面临着3个方面技术挑战：产品系列化和均质化、深加工与先期介入、新技术新产品的原创发明。     

TRIP钢的研究进展

相变诱发塑性钢,即TRIP钢是一种具有高强塑性的高强钢,其强塑积可达 21000MPa·%,作为汽车用钢的应用前景十分广阔.TRIP钢在TRIP效应、成分设计、成形性、焊接性、可镀性、动态力学性能等方面的研究十分活跃,已取得显著成果,并且在相图计算应用于成分和组织设计的研究方面也取得明显进展.     

超高强塑性汽车构件的先进热成形处理AHFT深加工技术

为满足新一代汽车对轻量化、节能和抗冲撞安全的需求,开发了一种新型先进热成形处理（AHFT）技术,以制造强塑积达15~30 GPa·%的超高强塑性汽车构件。基于先进高强度钢AHSS塑性化热处理技术和残余奥氏体相变诱导塑性TRIP效应,在传统热冲压成形后随即控制淬火冷却速率和温度,并进行贝氏体等温淬火处理（AT）或淬火-碳分配-回火处理（Q-P-T）,使热成形淬火构件获得超高强度（抗拉强度不小于1.0 GPa）铁素体-残余奥氏体型的F-TRIP钢、贝氏体-残余奥氏体型的B-TRIP钢、马氏体-残余奥氏体型的M-TRIP（或Q-P）钢,可以显著提高热成形超高强度构件的伸长率和强塑性。这种先进热成形处理AHFT技术,可以采用22MnB5、TRIP钢、Q-P钢和Q-P-T钢为基础的化学成分,通过传统热连轧宽带钢机组或者短流程CSP薄板坯连铸连轧机组,生产热轧超薄（1.2~2.0 mm厚）酸洗板作为原料。先进热成形处理AHFT技术与短流程CSP相结合,生产超高强塑性汽车构件,是高效、节能、环保的短流程深加工技术,可以显著缩短汽车构件的整体制造流程,降低生产成本,大幅度减少汽车构件制造过程中和汽车使用过程中的CO2排放,并拓宽热成形构件产品的种类及其强度和塑性级别范围。     

汽车用高强塑积钢关键研究进展之一:Q&P钢的研究进展

高强塑积QP钢以其优异的强度、塑性及成型性能得到诸多研究者的关注,并在汽车轻量化研究中起到了重大作用。本文以汽车用第三代高强塑积QP钢的关键研究进展为对象,从高强塑积QP钢的成分设计及优化、热处理工艺对组织调控的影响及其性能强化机制3个方面对国内外QP钢的合金化、制备及强化机制进展进行了概括介绍。以期为我国高强塑积QP钢的研发及推广提供参考。     

汽车零部件用高强度钢材的进展

论述了近年来汽车用高强度钢材（钢板和钢管）的发展现状和未来研究方向,着重评价日本在汽车用高强钢方面的新材料、新工艺和新技术的研究与开发的情况,特别是固溶强化钢板和ＴＲＩＰ钢板的研究和生产进展情况。     

汽车用传统高强钢和先进高强钢

现代汽车工业的发展趋势是在保证安全性能不变的前提下尽可能轻量化以降低油耗和排放,汽车轻量化的首选材料就是高强度钢。文章介绍了当前汽车工业中普遍使用的各种传统高强度钢——IF钢（HSSIF）、烘烤硬化钢（BH）、各向同性钢（IS）、高强度含P钢和低合金高强钢（HSLA）,以及先进高强度钢——双相钢（DP）、复相钢（CP）、相变诱导塑性钢（TRIP）、铁素体-贝氏体（FB）钢和马氏体钢（M）、TWIP钢以及热成型（HF）钢、预成型热处理钢（PFHT）的特点及优异性能,并简要分析了未来汽车用钢的发展方向。     

高强度高塑性第三代汽车钢的M3组织调控理论与技术

高强度、高塑性是汽车钢的重要发展方向,本文综述了高强度高塑性第三代汽车钢的"多相(multiphase)、亚稳(metastable)和多尺度(multiscale)"M~3组织性能调控理论和技术,以及面临的新挑战。M~3组织与性能调控理论为高强度高塑性钢提供了理论支持,亚稳奥氏体的相变诱发塑性(TRIP)效应能够提高加工硬化率并推迟颈缩的发生,从而提高了钢的强度与塑性,同时产生了剪切边裂纹敏感性提高,氢致延迟断裂性能下降,循环载荷下亚稳奥氏体的转变行为复杂等新的问题和挑战。当前,含亚稳奥氏体高强度高塑性钢的质量一致性和应用基础研究缺乏,而汽车钢作为量大面广的产品,需要从它的成分设计和组织调控-冲裁切割-成形制造-连接涂装-服役评价等全链条环节中开展组织演变和性能评估,充分考虑产品的技术适用性和成本,进而为组织调控理论和技术的完善提供依据。     

第三代高强度汽车钢的性能与应用

为满足汽车轻量化的需要,高强度钢板在白车身上的应用比例呈增长趋势,第三代高强钢由于具备高强度、高韧性、优良的冷成形性能而深受汽车制造业关注。本文列举了两类三代钢Q&P钢和ART钢的冶金设计原理、基本性能、最新应用研究成果及可行性验证实例,通过与传统的第一代高强钢的性能对比展示了第三代钢的突出性能并预测了未来第三代钢在汽车上的应用趋势。     

抗地震用建筑结构钢的显微组织及成分设计

地震波谱分析表明，地震区建筑结构用钢受震时的主要失效形式是高应力低周疲劳损伤和断裂。提高建筑结构钢的抗震性，应在保证钢材具有较高强度的同时，提供其塑性和韧性。低碳微合金铁素体晶粒超细化钢、双相钢和低合金相变诱发塑性钢都具有良好的抗震性。本文对钢的抗震性、显微组织和成分设计进行了简要阐述。     

Dissimilar metal joining of aluminium to zinc-coated steel by ultrasonic plus resistance spot welding – microstructure and mechanical properties

Vehicle body structures are increasingly utilising multi-materials designs with advanced high strength steels (AHSS) and aluminium alloys. A robust process for joining aluminium alloys to AHSS based on resistance spot welding (RSW) is essential to widespread application of such bi-metallic structures in fuel-efficient vehicles. In this study, ultrasonic plus RSW was applied to join AA6022 to Zn-coated dual-phase steel DP980. During solid-state ultrasonic spot welding, an interface structure comprising multilayer, Al–Zn and Zn–Fe intermetallics formed due to alloying of aluminium with steel coating. Such structure was subsequently melted into the aluminium nugget, and new Al–Fe intermetallics formed during RSW. Ultrasonic plus resistance spot-welded joints had superior fracture energy than direct resistance spot-welded joints.     

先进高强钢电阻点焊接头断裂模式的研究进展

随着汽车轻量化的发展趋势,先进高强钢(Advanced high strength steels,AHSS)在汽车结构中的应用逐渐增加,因此研究AHSS电阻点焊接头具有重要意义。重点关注AHSS点焊接头的断裂模式问题,综述近年来国内外关于同种材料两层板断裂模式、异种材料两层板断裂模式、三层板断裂模式、断裂模式的数值模拟以及界面断裂抑制方法等方面的研究进展,提出AHSS点焊接头的断裂模式及机制研究中有待解决的问题,展望未来关于AHSS点焊接头的断裂模式的研究热点和方向。     

Bendability of advanced high strength steels—A new evaluation procedure

The significant lightweight engineering potential of advanced high strength steels (AHSS) is limited by its moderate formability and altered failure behavior compared to mild steel grades. Especially bendability is crucial in automotive applications. The failure phenomena and underlying damage mechanisms in small curvature bending of AHSS are revealed in this work. A new characterization approach based on optical strain measurement is presented to comprehensively identify the failure stages, critical strains and bending angles in a user-independent manner. The novel approach is generalized and broadly applicable. Thus it gives a prerequisite for improved and material specific industrial process design in future.     

Copper brazing response of some advanced high strength steel grades

Sheet steels are commonly used in automotive powertrain applications wherein formed and assembled components undergo a copper brazing operation as part of the manufacturing process. For high performance applications including transmission pump housings and turbines, specially processed microalloyed steels have been developed and specified in order to develop the desired mechanical properties after exposure to brazing temperatures of ～1100 °C. New families of advanced high strength steel (AHSS) sheet are currently being developed and implemented. These are typified by increased alloy levels and exhibit unique property combinations that are particularly suited to auto body applications requiring the dual characteristics of high formability and high strength. Here it is considered that such grades may also be suited to powertrain components requiring high initial formability coupled with high final strength after copper brazing. That is, transformation strengthening during cooling after brazing is envisioned as a potential strengthening mechanism available with these new steels. In this work, initial screening results are reported to elucidate the response of some experimental AHSS to a simulated copper brazing operation during which the steels are taken into the austenitic temperature range and subsequently cooled at moderate rates to ambient conditions.     

Improvement of stretch flangeability of ultra high strength steel sheet by smoothing of sheared edge

Stretch flangeability of an ultra high strength steel sheet having small ductility was increased by improving quality of a sheared edge. The effect of the quality of the sheared edge on the stretch flangeability of the high strength steel sheets was examined from expansion of a sheared hole with a conical punch. The quality of the sheared edge varied with the clearance between the punch and die, and the quality influenced the limiting expansion ratio. It was shown from measurement of surface of the sheared edge that the limiting expansion ratio of the sheared ultra high strength steel sheet is dependent on the macroscopic unevenness and hardness of the sheared edge and not on the microscopic roughness. The macroscopic unevenness of the sheared edge was eliminated by smoothing the edge with a conical punch. It was found that the smoothing of the sheared edge is effective in improving the stretch flangeability of the ultra high strength steel sheet.     

Plastic Joining of Ultra High Strength Steel and Aluminium Alloy Sheets by Self Piercing Rivet

Ultra high strength steel and aluminium alloy sheets were plastically joined by a self piercing rivet driven through the upper sheet and spread in the lower sheet with a die. The self piercing rivet directly pierces into the sheets without drilling the sheets beforehand unlike the conventional rivets. Insufficient driving though the upper sheet and fracture of the lower sheet occur due to the high hardness and low ductility of the ultra sheet, respectively. An ultra high strength steel sheet having a tensile strength of 980MPa and an aluminium alloy sheet were successfully joined by optimising shapes of the die.     

稀土La对3Cr2W8V热作模具钢组织和性能的影响

研究了在3Cr2W8V热作模具钢中分别加入3种不同含量稀土La后,对组织、强度、硬度、冲击韧度和塑性的影响,并在相同的热处理工艺条件下,与不添加稀土La的3Cr2W8V钢进行对比。研究结果表明:稀土La加入量在适当的范围内可使组织得到明显细化,强度、冲击韧度和塑性有显著提高而硬度无明显变化,当稀土La加入量为0.20%时,3Cr2W8V钢可获得最好的综合力学性能。