煤矿机械用Q690高强钢抗裂性研究

对煤矿机械用Q690高强钢,采用其配套焊丝(GHS75M)进行抗裂性试验,并测定了焊丝熔敷金属扩散氢逸出特性,研究了焊缝金属残余扩散氢对试验用钢抗裂性的影响.结果表明:该钢具有一定的冷裂倾向.试验焊材熔敷金属扩散氢含量为1.7 mL/100 g,初期扩散氢逸出速率较大,在焊缝冷却过程中扩散氢可以较快逸出.残余扩散氢含量主要与从峰值温度到100℃温度区间的冷却时间t100有关,单道焊焊缝金属冷速快,t100较小,残余扩散氢较多,而多层多道焊增加了t100,且提高HDr100容许值,残余扩散氢含量很低.该钢采用焊后热处理是保守的工艺.     

Corrosion fatigue of coated AISI 4340 high strength steel with dent damage

Tension‐compression fatigue behaviour of a high‐strength steel, coated with cadmium and zinc‐nickel, with dent damage was investigated under saltwater environment. Dent damage exposed coated high‐strength steel substrate to saltwater environment to study hydrogen reembrittlement. Three types of specimens were tested: cadmium and zinc‐nickel‐coated specimens with dent damage and uncoated specimens with similar dent damage that were shot‐peened in a similar way as the coated specimens. The environmentally friendly zinc‐nickel‐coated specimens displayed similar fatigue behaviour like hazardous cadmium‐coated specimens. Scanning electron microscopy with an apparatus Quanta 450 confirmed that damage mechanisms were similar in all 3 types of specimens.     

热输入对Q890高强钢焊缝组织及性能的影响

针对国内某钢厂最新研制的Q890高强钢,采用三种不同的热输入对其进行气体保护焊接,研究了不同热输入对焊缝金属组织、硬度及冲击韧性的影响.结果表明,3种热输入下,焊缝组织主要以板条贝氏体为主,并含有粒状贝氏体、少量的板条马氏体和残余奥氏体.随着热输入的增大,焊缝组织中贝氏体铁素体板条粗化,板条马氏体逐渐减少,而粒状贝氏体逐渐增多,部分残余奥氏体由薄膜状向块状转变;焊缝金属硬度随着热输入的增大而下降;焊缝金属的冲击韧性亦呈逐渐下降的趋势.     

先进高强度钢板弯曲类回弹特性的试验研究

随着先进高强钢板在汽车及航天航空领域的广泛应用,回弹导致的成形精度问题日益突出.为了获取先进高强钢的弯曲回弹特性,通过采用U形件回弹模型,针对600MPa级别的3种典型高强钢(DP钢、TRIP钢、HSLA钢)进行了回弹试验研究.实验结果表明:在相同变形条件下,TRIP钢弯曲回弹最大,DP钢次之,HSLA的弯曲回弹最小;不同工艺条件、不同材料性能参数对弯曲回弹呈单调的影响规律,而润滑条件对弯曲回弹的影响趋势并未出现一致性规律.     

高强度热冲压钢板强韧性工艺优化研究

为改善强韧性,本文基于热冲压高强度钢板强度、塑性和韧性指标,选取加热温度、保温时间和开始淬火温度为设计因子,引入Kahn试验获得高强度热冲压硼钢撕裂强度和单位面积裂纹形核功来表征材料断裂韧性,进行多指标综合评分的L9(34)正交试验设计,以研究不同淬火工艺参数对热冲压高强钢强韧性的影响规律.结果表明:在加热温度为920~950℃、保温时间1 min、开始淬火温度为650~700℃条件下,热冲压硼钢SPFH具有优良的成形性能和强韧化指标.采用优化后工艺进行典型车身结构件热冲压试验,其撕裂强度、单位面积裂纹形核功和强韧比分别提升10.91%、20.32%和22.17%,在保证强度的基础上韧性得到了大幅度提高.     

高强钢TRB高温下热流变特性

为了准确仿真高强钢板热冲压成形过程,获得高强钢高温下的材料本构关系模型,利用Gleeble3500热模拟试验机在不同温度和应变速率下对不同厚度的高强钢B1500HS钢板进行了单向拉伸试验,获得各种工艺条件下的应力-应变曲线,并基于变形抗力数学模型,引入板材厚度参数,通过最小二乘法进行数据拟合获得高强钢TRB高温下的材料本构关系.利用试验结果对本构关系模型进行的拟合验证表明,拟合程度较好,说明建立的材料本构关系能很好地描述高强钢TRB在高温下的应力-应变关系.     

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.     

Effect of heat treatment on mechanical and ballistic properties of a high strength armour steel

In the present study an ultra high strength armour steel was austenatised at 910°C followed by tempering at 200, 300, 400, 500 and 600°C. After heat treatment the properties of tensile strength, ductility, charpy impact strength, hardness and microstructure were evaluated from the mechanical tests and metallographic analysis respectively. The ballistic behavior of the heat-treated plates was evaluated impacting against non-deformable hard steel core projectiles at 840 ± 15 m/s at normal angle of attack. The changes in the microstructure and mechanical properties with heat treatment have been correlated with ballistic performance of the steel. Experimental results showed that 200°C tempering gives the best ballistic performance.     

高强钢框架-屈曲约束支撑体系抗震性能研究

针对高强钢结构在抗震设计中存在的结构延性差、刚度小的问题,提出了高强钢框架-屈曲约束支撑结构.为研究此类结构的抗震性能,对2个足尺单榀单跨单层试件进行了拟静力加载试验,观测了结构在水平往复荷载下变形特征与破坏模式,分析了结构及构件滞回曲线特征,探讨了试件强度退化、刚度退化、塑性变形、耗能能力以及钢框架和屈曲约束支撑的承...     

Very high cycle fatigue properties of high‐strength spring steel 60SiCrV7

The very high cycle fatigue properties of spring steel 60SiCrV7 for automotive suspension system with different hydrogen contents were studied by using ultrasonic fatigue testing and fatigue crack growth testing. The results show that the S–N curves exhibit continuous drop of fatigue lives and no obvious horizontal line exists. Similar fracture surface features were observed for all the specimens that failed mainly from internal inclusions with surrounding granular bright facet (GBF). Fatigue strength decreases remarkably with increasing hydrogen content. The applied stress intensity factor range at the periphery of GBF ΔK_GBF is approximately proportional to 1/3 power of the square of GBF area. The average values of ΔK_GBF for uncharged specimens are close to crack growth threshold ΔK_th, which indicates that ΔK_GBF could be regarded as the threshold value governing the beginning of stable fatigue crack propagation. The increase of hydrogen content tends to reduce ΔK_GBF.     

高强钢板冲压成形的回弹规律与工艺参数研究

高强钢板冲压成形的回弹问题在很大程度上制约了其深入应用,合理的工艺是减少回弹的关键和有效途径之一.建立了曲面扁壳件冲压成形的有限元模型,基于正交试验法研究了工艺参数,包括压边力、摩擦系数、板厚以及拉深筋的布置方式对回弹的影响规律,采用普通钢板和高强钢板分别进行了冲压成形实验,并与数值模拟结果进行对比.结果表明,高强钢板冲压成形的回弹较大,但通过合理的压边力和拉深筋布置方式可以实现高强钢板冲压成形回弹的有效控制.     

Mechanical properties of normal strength mild steel and high strength steel S690 in low temperature relevant to Arctic environment

The development of Arctic oil and gas fields requires low temperature high strength steel materials that can resist critical loads in extreme environments. This paper investigates the mechanical properties such as stress–strain curves, elastic modulus, yield strength, ultimate tensile strength, and fracture strain of normal mild steel and high strength S690 steel to be used in low temperatures relevant to arctic environment. Tensile tests are carried out on steel coupons at different temperatures ranging from −80 °C to +30 °C in a cooling chamber. The influences of the low temperatures on the mechanical properties of mild steel and high strength steel are compared and their differences are discussed. Regression analyses are also carried out on the test data to develop empirical formulae to predict the elastic modulus, yield strength, and ultimate strength of the steels at ambient low temperatures. Finally, design formulae are recommended and their accuracies are further confirmed by the test data including those from the literature.     

基于BP神经网络遗传算法的高强钢成形研究

对新材料DP-780高强钢依据国家标准GB/T228.1-2010进行室温拉伸试验,获得材料的力学性能参数;依据冲压成形极限图,进一步提出冲压成形质量评价指标;针对车身侧围板整个冲压制造工艺过程,对不同的工艺参数设计正交试验,并得到试验数据库;根据BP神经网络遗传算法得到最优参数组合,最后经试验验证,满足成形工艺要求并且与数据库结果相匹配。     

Q460高强钢柱在近爆荷载作用下的动力响应研究EI北大核心CSCD

采用有限元软件ANSYS/LS-DYNA,建立钢柱有限元模型,运用流固耦合计算方法,模拟Q460高强钢柱在爆炸荷载作用下的动力响应,在此基础上提出了分段等效三角波计算方法对结构/构件施加爆炸荷载,并对影响钢柱动力响应的主要因素进行数值分析。结果表明:分段等效三角波计算方法和流固耦合方法计算吻合较好,验证了分段等效三角波计算方法的可行性;爆炸冲击波速度快,荷载峰值大,持续时间短,对钢柱的破坏力极强;钢材强度等级越大,钢柱抵抗变形的能力越强;炸药位置越低,柱脚越容易发生剪切破坏;翼缘作为迎爆面更能抵抗爆炸冲击的作用;适当减小翼缘和腹板的宽厚比能增强钢柱抵抗动力荷载的能力。提出的分段等效三角波计算方法为研究抗爆提供进一步参考。     

高强度低屈强比铆螺钢轧制工艺的研究

为消除螺栓在热处理中产生的各种缺陷,缩短生产周期,使铆螺钢免热处理.采用热模拟试验机、实验室轧机和多工位冷镦机对铆螺钢轧制实验,铆螺钢原料和成品分别在拉力试验机和万能试验机上进行拉力试验,并对其组织进行了分析.结果表明,铆螺钢经过控轧控冷,获得具有多边形铁素体、细片状珠光体、粒状贝氏体、残余奥氏体和少量MA岛的多相组织.由于控轧控冷后的多相组织及TRIP效应,改善了螺栓的强韧性.铆螺钢因低的屈强比可以直接由热轧棒材冷镦成螺栓,螺栓无需最终热处理,产品的力学性能满足8.8级螺栓国家标准的相应要求.     

Fatigue behavior of press hardened Al-Si coated high strength steel

The fatigue behavior of press hardened Al-Si coated high strength steel has been investigated and the fatigue strength turns out to be about 1000MPa. Surface morphology of fractured and non-fractured specimen has been observed and the coating shows significant influence on the fatigue behavior. The difference of elastic modulus between coating and substrate leaded to the main cracks perpendicular to the loading direction. Coating close to the fracture lamellar exfoliated while the coating far away from the fracture kept integrated. Though the specimen has been polished to obtain high surface quality, three types of cracks occur during the fatigue test. What’s more, inclusion particles proved to play a crucial role in causing the cracks.     

高强钢合金化热镀锌研究进展

随着汽车工业的发展,高强钢合金化热镀锌板作为一种资源节约、环境友好型的新型材料得到了广泛的应用.与普通热镀锌钢板相比,高强钢合金化热镀锌板具有优异的焊接性、涂装性及涂装后的漆膜耐砂砾冲击性.介绍了高强钢合金化热镀锌的研究现状、基板种类和生产工艺对镀层结构及性能的影响,初步探讨了合金层形成机理,并对高强钢合金化热镀锌今后的发展进行了展望.     

Hybrid laser/arc welding of advanced high strength steel in different butt joint configurations

An experimental procedure was developed to join thick advanced high strength steel plates by using the hybrid laser/arc welding (HLAW) process, for different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm from the weld centerline. The cross-section of the welds was examined by microhardness test. The microstructure of welds was investigated by scanning electron microscopy and an optical microscope for further analysis of the microstructure of fusion zone and heat affected zone. It was demonstrated that by changing the geometry of groove, and increasing the stand-off distance between the laser beam and the tip of wire in gas metal arc welding (GMAW) it is possible to reduce the width of the heat affected zone and softened area while the microhardness stays within the acceptable range. It was shown that double Y-groove shape can provide the optimum condition for the stability of arc and laser. The dimensional changes of the groove geometry provided substantial impact on the amount of heat input, causing the fluctuations in the hardness of the weld as a result of phase transformation and grain size. The on-line monitoring of HLAW of the advanced high strength steel indicated the arc and laser were stable during the welding process. It was shown that less plasma plume was formed in the case where the laser was leading the arc in the HLAW, causing higher stability of the molten pool in comparison to the case where the arc was leading.     

高强钢22MnB5扭力梁热成形热力耦合数值模拟

为了探究高强钢管22MnB5热气胀成形V型截面扭力梁的工艺,采用热力耦合数值模拟的方法研究了高温成形时扭力梁温度场、应力场、应变场、壁厚分布规律以及成形精度.研究发现:成形结束时,由于温度场分布的差异,各个区域材料流变性能不同,因此,最大主应力位于温度场较低区域,最大主应变位于温度场较高且膨胀量较大区域;随着试件初始温度的提高,成形后试件最低温度和最大减薄率均增大,成形精度提高;随着摩擦系数的增大,成形后试件最大减薄率增大.研究表明:当初始试件温度为850℃、摩擦系数为0.1、整形气压20 MPa时,成形后得到成形精度较高,最大减薄率为14%的试件,且成形后最低温度为499℃,高于马氏体开始转变温度.     

Fatigue strength prediction of ultra high strength steel butt‐welded joints

First, fatigue tests were performed on butt‐welded joints made of novel direct quenched ultra high strength steel with high quality welds. Two different welding processes were used: MAG and Pulsed MAG. The weld profiles, misalignments and residual stresses were measured, and the material properties of the heat‐affected zone were determined. Fatigue tests were carried out with constant amplitude tensile loading both for joints in as‐welded condition and for joints after ultrasonic peening treatment. Finally, in fatigue strength predictions, the crack initiation phase was estimated using the procedures described by Lawrence et al. [Lawrence F V, Ho N J and Mazumdar P K (1981) Predicting the fatigue resistance of welds. Annu. Rev. Mater. Sci, 11, 401–425]. The propagation phase was simply estimated using S–N curves for normal quality butt welds, which may contain pre‐existing cracks or crack‐like defects eliminating the crack initiation stage.