热冲压成形新型B 钢开发与工艺研究

在传统22MnB5成分基础上添加Cr、Mo等化学元素,开发出热冲压专用新钢种22MnMoB材料,并通过金相显微镜、显微硬度计、电子拉伸试验机等设备对22MnMoB材料进行材料性能、材料连续冷却转变曲线(CCT)、热处理工艺性能测试,通过中试线、热冲压模具等设备测试材料的工艺参数、试制热冲压零件并测试零件性能。试制结果显示,新开发的22MnMoB材料具有良好的抗短时高温氧化性能、成形淬火后材料组织细小、强度级别与原有22MnB5相当,但总延伸率大大提高。     

超高强度硼钢板热弯曲数值模拟

为研究热自由弯曲和热接触弯曲方法的淬火效果和成形精度,应用ABAQUS软件,对超高强度硼钢板U形件的热弯曲过程进行了数值模拟研究.研究表明:热接触弯曲改善了热弯曲零件底部的淬火效果,且热接触弯曲可获得比热自由弯曲更好的成形精度;不同压边力下热接触弯曲回弹均随着压边力的增加而逐渐减小;数值模拟结果与实验结果吻合较好,验证了有限元模型的可靠性.     

筒形件毛坯热冲压成形过程数值模拟

针对某厚壁深孔筒形件,借助三维有限元模拟软件Deform-3D,对其成形的压型、冲盂和拔伸等3个工步进行模拟,分析得到各工步变形特点。结果表明,压型即将结束时载荷急剧升高,坯料底部转角处和凸台未完全充满,未充满部位在冲盂工步即将结束时得以充满;冲盂时凸模端部以下一部分锥形金属由于受摩擦作用不参与变形,随凸模刚性下移;拔...     

铝合金板材热成形-淬火一体化工艺研究进展

为解决铝合金室温塑性差和成形后热处理变形的问题,发展起来了一种铝合金板材热成形-淬火一体化新工艺。该工艺是将热处理和热成形在同一工步完成,即固溶后板材快速转移到模具中成形,然后完成模内淬火,最后通过时效来提高其强度。高温成形可提高板材成形性能,模内淬火能够保证其强度和尺寸精度。重点介绍了铝合金板材热成形-淬火一体化工艺关键技术及最新研究进展,总结了铝合金板材热成形-淬火一体化工艺实验研究和数值模拟的研究现状。     

异形件冲压成形工艺及模具设计

介绍了一异形件的冲压成形工艺,并针对该异形件的初步设计方案进行了改进,对冲压成形工序进行了合理的组合,设计并加工了生产该异形件的3套模具,对类似零件的冲压工艺分析和模具设计将会有一定的参考和借鉴价值.     

淬火时间对硼钢板热冲压的作用

现代汽车制造中越来越多地应用硼钢板热冲压技术来减轻车身重量并提高碰撞安全性,淬火时间对该过程中板料热力学行为和组织转变有重要作用。以汽车热冲压件的典型特征结构——U形梁为对象,将马氏体相变动力学模型嵌入硼钢板热冲压全过程热力耦合三维有限元模型中,实现了对该过程中板料热力学行为和马氏体相变的有效预测,预测结果与实验结果吻合良好。揭示了淬火时间对硼钢板热冲压的影响,结果表明,随淬火时间的延长,板料温度和温降速率均降低,温度分布越均匀;马氏体转化率增加,分布趋于均匀,但淬火时间超过22s后,马氏体转化率的大小和分布不再发生变化;最大回弹值减小。     

硼钢热冲压模具CAE顺序耦合建模及强度校核

目的针对热冲压模具开裂的问题,提出一种模具强度校核方法。方法借助有限元仿真软件ABAQUS,对B柱进行循环仿真,获取稳定变化的模具温度场;借助专业成形软件Dynaform完成B柱成形、保压过程的仿真,获取模具和板料间的节点接触力;将模具温度场和节点接触力作为边界条件进行模具强度仿真分析。结果模具的危险区域是模具内部靠近圆角的流道交接处,此处因为承受强烈的热冲击存在交变拉应力作用,同时又因为加工缺陷存在应力集中,是疲劳裂纹最容易萌生的地方。结论 CAE顺序耦合仿真能准确高效地计算热冲压模具的温度场、热-机械耦合应力场,分析模具的危险区域,指导模具的设计和加工,延长模具使用寿命。     

高强度钢-普通钢拼焊板热冲压成形机理研究

目的 研究高强度钢-普通钢拼焊板热冲压成形机理.方法 对高强度22MnB5钢-Q235钢拼焊板高温力学性能及U形热弯曲件的微观组织和力学性能进行实验研究,对高温下拼焊板协调变形进行数值分析,研究拼焊板高温力学性能和热弯曲件微观组织、力学性能的影响机制及拼焊板热变形协调机制.结果 焊缝与拉伸方向平行时,800℃下拼焊板伸...     

钢板热冲压技术在汽车制造中的应用

钢板热冲压技术能够在确保制作高强度的钢板时其形状不变,这种钢板用于汽车制造领域可提升汽车的碰撞性能。该文主要介绍了钢板热冲压技术及其工艺原理、数值应用,并进行数值模拟,最后对这项技术的使用现状以及未来的发展前景进行了阐述。     

工艺参数对热冲压成型钢组织性能及硼偏聚的影响

通过Gleeble1500热/力模拟实验机对轧后含硼钢板进行了热冲压过程模拟,分析了各种热处理条件对含硼钢组织性能的影响,并采用X射线衍射技术和径迹照相技术分析了硼的偏聚和硼相析出情况。研究结果表明:提高加热温度或延长保温时间,可促进钢的奥氏体化和硼的偏聚。通过偏聚合适含量的硼,能够很好地起到提高淬透性作用,使材料得到全部马氏体组织。热冲压成型过程中的变形破碎了奥氏体组织,促进相变,更易获得细小的马氏体组织。当冷却速度不高时,钢中"硼相"会沿晶界连续析出,从而降低了硼钢的淬透性。     

Numerical simulation of hot stamping of quenchable boron steel

Quenchable boron steel is a new type of ultra-high-strength steel used for automotive parts to reduce the weight of automobiles and maintain the safety requirements. On the basis of experimental data of mechanics and thermal physical properties, a material model under hot stamping condition of quenchable steel was set up, and the numerical simulation to the whole hot stamping process of hot forming, quenching and spring-back of bending parts was made with ABAQUS software. The results show that the springback of hot stamping parts increases when the blank-holder force (BHF) decreases; and it increases when the clearance between punch and dies increases and when the die radius increases. The simulation results are basically in agreement with experimental results.     

New generation ultrahigh strength boron steel for automotive hot stamping technologies

Abstract

The automotive industry is under increasing pressure to: (1) reduce the weight of vehicles and (2) improve crash performance. ‘Hot stamped’ mild carbon–manganese–boron steel 22MnB5 has become common place in the body structure of the European vehicle over the past decade. The ultrahigh strength martensitic microstructure resulting from hot stamping (proof strength ～1200 MPa and ultimate tensile strength ～1500 MPa) enables down gauging while not compromising crash performance. However, with demands for yet higher strength in the final component so to enable further down gauging, novel grades must be developed. In this paper, development of the novel grade 38MnB5 was reported. Following hot stamping, 38MnB5 demonstrated proof strength in excess of 1400 MPa and ultimate tensile strength in excess of 2000 MPa. Owing to the immense strength, the novel grade 38MnB5 was considered to offer significant down gauging and weight reduction opportunities to the automotive industry.     

Study on the thermo-mechanical-metallurgical couple model of tailored hot stamping

In order to predict the microstructures and hardness evolution of tailored hot stamping (THS) component, a thermo-mechanical-metallurgical couple finite element model was established. In particular, the activation energies for ferrite and bainite in the model were optimised. THS experiment of U-shape component with segmented heating and cooling was also performed to compare the hardness distribution and phase change with numerical simulation. The results showed that the original model and the activation energy optimised model can both be used to predict the microstructures and hardness evolution for hot stamping components with full martensite. As for THS component, the effect of cooling path and deformation on the activation energies of phase transformation should be considered.     

Effect of carbon and microalloy additions on hot-stamped boron steel

Hot stamping was performed with seven novel boron steels, exhibiting various carbon contents and microalloy additions of Mo, V and Ni compared to the standard 22MnB5 boron steel. The lower carbon content of 15MnB5 resulted in total elongation in excess of 11.0%. The higher carbon content of 38MnB5 resulted in ultimate tensile strength in excess of 2000?MPa. The vanadium addition resulted in ultimate tensile strength in excess of 1600?MPa combined with total elongation in excess of 11.0%. The carbon and microalloy additions were concluded to give rise to improved mechanical properties in hot-stamped boron steel for automotive body engineering applications.     

Modelling flow behaviour of quenched boron steel with different microconstituent volume fractions

Hot stamped component of boron steel with tailored mechanical properties has multiphase microstructures. It is very important to establish a constitutive model related to multiphase microstructures for predicting the mechanical properties in the final component. Boron steel quenching experiments under different tool temperatures were performed with self-made experimental apparatus to achieve quenched specimens with different microconstituent volume fractions. Colour tint etching and image processing techniques were used to quantify the volume fractions of microconstituents. Tensile tests were also conducted to obtain stress–strain curves of the component with different volume fractions of microconstituents. The constitutive model of flow behaviour for quenched boron steel related to strain, strain rate and the volume fraction of quenched microconstituents was established by modified Field–Backofen.     

应变速率对热冲压淬火-配分钢显微组织与力学性能的影响EI北大核心CSCD

采用分离式Hopkinson压杆对热冲压淬火-配分(HS-Q&P)钢在0~12000 s^(-1)应变速率范围内进行动态压缩实验,利用SEM,EBSD,XRD等分析表征手段探究动态压缩过程中试样的变形行为。结果表明:实验钢在不同速率下的变形行为基本相似且分为3个阶段,在平台处应力有小幅度增加,增幅更多体现在应变上。在压缩过程中出现的绝热升温会带来软化效应。残余奥氏体的存在会提高实验钢的强度和塑性变形能力。钢中残余奥氏体发生相变诱导塑性(transformation induced plasticity,TRIP)效应减少的体积分数与马氏体增加的体积分数基本一致,证明TRIP效应为钢中主要的强化机制。同时,通过SEM可观测到残余奥氏体发生TRIP效应转变成细小针状马氏体,随着应变速率增加,晶格畸变越来越严重,EBSD图像中可以观测到部分形变孪晶,在不同应变速率下,〈001〉取向的晶粒都会更容易产生形变孪晶。     

基于AUTOFORM模拟的顶盖前边梁加强板热冲压工艺

目的 研究顶盖前边梁加强板热冲压成形过程中不同参数对零件成形的影响规律,为生产提供技术指导。方法 通过AUTOFORM模拟零件热成形过程,并对模拟结果对比分析,得到了板料尺寸、成形温度、保压时间、成形压力、冷却时间等工艺参数对成形性能的影响。结果 优化了板料尺寸及板料定位,并通过调节模具间隙保证了零件的成形性,得到零件最大减薄率小于15%,平均抗拉强度达到1450 MPa,平均硬度达到HV475,从而确定了顶盖前边梁加强板的热冲压工艺。结论 结合此有限元分析方法试制出抗拉强度大于1450 MPa的合格零件,为此类零件批量化生产提供理论依据。     

热成形钢22MnB5的Q&P工艺

采用盐浴法对热成形钢22MnB5进行了Q&P工艺(quenching and partitioningprocess)处理,研究了淬火终点温度、分配温度和分配时间对试验钢的显微组织、力学性能和残余奥氏体含量的影响。结果表明:Q&P工艺处理22MnB5钢的显微组织主要为马氏体和残余奥氏体组织,同时有一定量的碳化物析出,随着淬火终点温度和分配温度的升高或分配时间的延长,马氏体和碳化物的微观形貌会发生变化;在淬火终点温度和分配温度为325℃,分配时间为60s时得到的试样强塑积最高,达到20435MPa.%;试样的拉伸断口都显示出良好的韧性断裂特征;XRD分析表明,在Q&P工艺处理后试验钢的残余奥氏体含量可达5.5%。