1000 MPa级热轧双相钢不同弛豫时间的热处理工艺

基于汽车轻量化原则,应用热轧+超快冷+弛豫热处理一体化工艺技术得到了1000 MPa级热轧双相钢,并研究了弛豫时间对试验钢组织和性能的影响。结果表明,随着弛豫时间的增加,试验钢中铁素体和马氏体组织的带状分布越明显,其中铁素体晶粒尺寸与体积分数均增加,屈服强度降低,伸长率增加;抗拉强度先增加后降低,是马氏体体积分数和碳含量综合作用的结果;屈强比减小,n值增加。弛豫时间影响两相的体积分数、晶粒大小和内部亚结构。弛豫时间为10 s时,试验钢的抗拉强度为1025 MPa、伸长率为17.5%、屈强比为0.48、n值为0.13,具有最优综合力学性能;综合考虑力学性能和生产效率,试验钢在该工艺技术条件下合适的弛豫时间为7~10 s。     

X80管线钢变形弛豫后的显微组织及析出行为

应用Gleeble-1500D热模拟试验机、维氏硬度计和ZEISS Supra55型场发射扫描电子显微镜研究了不同弛豫时间下X80管线钢的显微组织、硬度及析出物的变化情况。研究结果表明,X80管线钢弛豫后的主要组织类型为贝氏体铁素体+条片状贝氏体,在弛豫过程中显微组织得到细化,并且显微组织的形态发生改变,片条状贝氏体数量增多。在弛豫时间200 s时,硬度出现峰值。随着弛豫时间延长,析出物的数量逐渐增多,并且弥散分布。     

机械用HG785钢的控轧控冷工艺研究

利用热轧机在880℃的变形温度下,研究了变形量和弛豫时间对HG785钢应变诱导析出的影响。结果表明:HG785钢中粒径尺寸100~200 nm的为未固溶的第二相粒子,而尺寸小于20 nm的析出物为应变诱导过程中产生的析出相。在试验条件下,62%的变形量和1 min的弛豫时间是最好的控制工艺参数。     

辐射聚合甲基丙烯酸甲酯的^1H NMR研究

用^1H NMR谱、质子自旋弛豫时间,研究了用γ射线辐射引发甲基丙烯酸甲馥的聚合反应,其聚合转化率和聚合物链运动与反应时间的关系,考察了聚合物在不同溶剂中的溶剂效应。结果表明甲基丙烯酸甲酯聚合转化率随着反应时间的增长而增大,从自旋-晶格弛豫时间（T1）和自旋-自旋弛豫时间（TD测定中得知,自旋-晶格弛豫时间几乎不随反应时间变化而变化,在氯苯溶剂中,不仅提高了谱图的分辨率,也使各质子化学位移发生了移动。     

弛豫时间和终冷温度对X70HD抗大变形管线钢微观组织的影响

通过金相组织分析研究了X70HD管线钢在两阶段变形后弛豫时间和终冷温度对微观组织的影响。结果表明,第二阶段变形后空冷弛豫到700℃,获得铁素体+下贝氏体的双相组织且无先共析铁素体生成,但随弛豫时间的延长有先共析铁素体生成并获得多边形铁素体+贝氏体的双相组织。终冷温度影响贝氏体的种类及含量,终冷温度保温时会产生更多下贝氏体;在相同弛豫条件下,终冷到320℃获得铁素体+少量粒状贝氏体,终冷到350℃获得铁素体+少量下贝氏体。     

Nb-O的Snoek-Kster弛豫

用低频扭摆和弹性后效测量了掺氧的超纯Nb的Snoek-K(o|¨)ster弛豫,研究了氧含量、形变量以及退火处理等因素对S-K弛豫的影响.实验观测到4种不同类型的S-K弛豫过程.在氧含量较低因而位错具有非饱和的填隙原子气团的条件下出现“SK-1”和“SK-2”弛豫,在饱和气团条件下出现“SK-4”弛豫,而“SK-5”弛豫也属于非饱和的情况.发展了一种处理弛豫时间连续分布的两个弛豫过程并存的方法,从而较精确地获得了这些S-K弛豫的激活参数.除了SK-1对退火较不稳定以外,其它均较为稳定.这些S-K弛豫过程的弛豫强度与弛豫时间分布宽度特征值均与测量温度无关.     

聚二甲基硅氧烷涂层自修复过程中的弛豫时间分布研究

针对传统电化学分析技术不能完全反映有机涂层腐蚀电化学过程的问题，采用弛豫时间分布(DRT)技术分析电化学阻抗谱(EIS)，研究了聚二甲基硅氧烷(PDMS)涂层在长效防腐过程及“人工划伤-自修复”循环过程中的动态弛豫时间分布。结果表明：结合等效电路模型分析方法，DRT技术能够清晰地分析PDMS涂层电化学过程中总电化学阻抗的组成及各部分贡献率，并从理论方面阐明了EIS等效电路中各元件对应的弛豫时间归属问题。为腐蚀电化学机理研究提供了一种新的分析技术。     

弛豫时间对1200MPa级热轧双相钢组织性能的影响

基于合金减量化原则,采用以超快冷技术为核心的新一代TMCP技术制备了1200 MPa级热轧双相钢,研究了弛豫时间对试验钢组织和性能的影响。研究表明:随着弛豫时间增加,试验钢铁素体晶粒尺寸和体积分数均增加,屈服强度降低,伸长率均在10.0%以上;组织中马氏体均以块状马氏体为主,并由块状向小岛状转变,其体积分数减少,抗拉强度降低,屈强比减小,n值增加。弛豫时间影响到铁素体和马氏体的体积分数及内部结构。弛豫9 s的试验钢,铁素体体积分数为44.2%,铁素体晶粒尺寸为3.4μm,组织中块状马氏体中板条束条宽细化至0.3μm及较多的小岛状马氏体有利于n值,抗拉强度达到1258 MPa,伸长率为12.0%,屈强比最低为0.55,n值高达0.13,其综合性能最好。     

高强度低碳贝氏体钢的工艺与组织细化

在超低碳贝氏体钢中，采用弛豫-析出-控制相变(RPC)技术可得到细化的中温转变组织，组织类型为细化的板条贝氏体及少量不规则粒状贝氏体或针状铁素体，与一般控轧空冷和调质处理组织比较，除细化外，所得贝氏体类型及形貌均有所不同，通过这种工艺细化的低碳贝氏体钢板其强度比控轧后空冷或轧后再加热-淬火(调质处理)钢有明显提高。在采用RPC工艺时，轧后弛豫时间长短对最终组织细化程度和形貌也有明显影响，从而造成性能有所差别，终轧后弛豫阶段形成并被应变诱导析出物钉扎的位错胞状组织或亚晶结构是细化相变组织、阻碍贝氏体生长的主要原因，冷却过程中，在贝氏体相变前形成的不规则粒状贝氏体或针状铁索体，分割了压扁的原奥氏体晶粒，同样限制了贝氏体板条柬的长度和宽度。     

二元合金非平衡凝固溶质分配的统计模型

本文用非平衡统计理论研究二元合金凝固时界面的溶质分配，得到了一般情况下溶质分配系数Ｋ与时间ｔ的函数关系。当ｔ→∞，Ｋ就成为平衡溶质分配系数Ｋ０，在ｔ大于热平衡弛豫时间ζ，小于结构平衡弛豫时间ζ０的时间区间内，Ｋ对Ｋ－的偏离随过热度ΔＴ的增大而增大，与实验结果一致。     

Effects of concavity on tensile and fatigue properties in fibre laser welding of automotive steels

DP980 dual phase and high strength low alloy (HSLA) steels were welded, using fibre laser, with varying amounts of concavity to determine its effects on the tensile and fatigue properties. Higher concavity, 25 to 35%, was observed to reduce the tensile strength of the DP980 welds, while not affecting the tensile strength of HSLA welds. All welds exhibited lower fatigue resistance compared to their base metals. However, DP980 welds with higher concavity (25 to 35%) exhibited even lower fatigue resistance while HSLA welds showed similar performance regardless of changes in concavity. Concavity could be minimised by reducing welding power and increasing the welding speed.     

回火时间对含铜HSLA钢板组织性能的影响

含铜HSLA钢板是高强度船舶用钢的理想材料,为确定其最佳热处理工艺,对不同回火时间下含铜HSLA钢板进行拉伸试验、冲击试验、测定宏观硬度,并借助OM、SEM等检测手段观察其金相组织.试验结果表明,随回火时间的延长,含铜HSLA钢板的基体组织中板条马氏体的板条结构逐渐消失,且钢板屈服强度、抗拉强度及硬度呈先升高后下降的趋...     

两相区淬火+回火对600 MPa级低合金高强钢组织与性能的影响

对某600 MPa级低合金高强钢采用了淬火+回火的热处理方式,研究了不同回火温度以及不同淬火温度对其组织性能的影响。结果表明,随着回火温度的升高,屈服强度、抗拉强度以及屈强比都呈下降趋势,伸长率逐渐上升,在620 ℃以上回火时出现第二类回火脆性,导致冲击性能急剧降低;在淬火温度达到820 ℃后得到的两相区淬火组织为铁素体+粒状贝氏体,有利于阻止裂纹的扩展,确保有较高的冲击性能。     

Welding behaviour,microstructure and mechanical properties of dissimilar resistance spot welds between galvannealed HSLA350 and DP600 steels

Abstract

Resistance spot welding experiments were conducted on dissimilar material combination of HSLA350/DP600 steels. The welds were characterised using optical and scanning electron microscopy. The fusion zone of the dissimilar material spot weld was predominantly martensitic with some bainite. Mechanical properties were also determined by tensile shear, cross tension and fatigue tests. The performance of dissimilar material spot weld was different from that of the similar ones in each of the HSLA350 and DP600 steels and exhibited different heat affected zone hardness. The DP600 weld properties played a dominating role in the microstructure and tensile properties of the dissimilar material spot welds. However, the fatigue performance of the dissimilar welds was similar to that of the HSLA350 welds. Fatigue tests on the dissimilar material spot welds showed that the 5·5 mm diameter nugget exhibited higher fatigue strength than the 7·5 mm diameter nugget.     

退火和平整工艺对冷轧HSLA钢组织性能的影响

 本文以Nb微合金化冷轧HSLA钢为研究对象,探讨了退火和平整工艺对钢板组织性能的影响,结果表明:退火温度从700℃升至840℃,钢板的强度逐渐降低,伸长率逐渐升高,纤维状组织逐渐减少,铁素体再结晶更加充分;预拉伸量对带钢抗拉强度和断后伸长率无明显影响,随着预拉伸量提高至2. 0%,屈服强度略有升高,屈服点伸长率Ae逐渐减小,但预拉伸量达到2. 0%时,屈服平台仍无法消除;平整压下率对带钢抗拉强度和断后伸长率无明显影响,当压下率达到1. 0%时,屈服平台可完全消除,屈服平台消除后,随着压下率提高,规定塑性延伸强度R_{p0. 2}缓慢升高。      

时效温度对HSLA100钢组织与性能的影响

研究了HSLA100钢轧态及时效过程中组织与力学性能的变化.结果表明:HSLA100钢轧态组织为高密度位错的板条贝氏体,板条间分布着少量M-A岛.经450℃时效处理后,大量球状ε-Cu相沉淀析出,此时钢板屈服和抗拉强度最高,而-40℃冲击功最低.在450～720℃时效时,随时效温度升高,高密度板条贝氏体发生回复,ε-Cu相粗化成短棒状,屈服强度连续下降,但在650℃时效时仍达到760 MPa的较高水平;抗拉强度在650℃时达到最低值后小幅上升:-40℃冲击功持续升高至700℃附近达到峰值.钢质纯净度是影响HSLA100钢低温韧性的一个主要因素,虽然通过升高时效温度可在一定程度上提高钢的低温冲击韧度,但增幅有限.     

Mechanical clinching of ultra-high strength steel sheets and strength of joints

Ultra-high strength steel sheets having low ductility were joined by mechanical clinching with dies for control of metal flow. The diameter and depth of the die were modified to relieve concentration of deformation of the sheets for avoidance of the occurrence of sheet fracture. As the tensile strength of the steel sheets increased, the interlock decreased due to small metal flow. Two kinds of the ultra-high strength steel sheets having different ductility were used. The ultra-high strength steel sheets having large ductility were successfully joined using die having modified shape, whereas the sheets having small ductility were not joined. The static and fatigue strengths of the mechanically clinched joint were compared with those of the resistance spot welded joint. Although the static load of the mechanically clinched joint was smaller than that of the resistance spot welded joint in both tension-shearing and cross-tension tests, the fatigue load of the clinched joint was larger in the large number of cycles. It was found that mechanical clinching has superior fatigue strength due to the large yield stress of the sheets and relaxation of the stress concentration.     

冷轧高强度低合金钢HC420LA的连续退火工艺

根据冷轧高强度低合金钢HC420LA的产品要求对其冷轧连续退火工艺进行了研究。HC420LA钢产品成分采用Nb、Ti微合金化成分体系、生产工艺选择热连轧+冷轧连续退火的工艺路线。通过实验室再结晶温度试验测定了HC420LA钢产品的再结晶温度,在工业化试生产阶段对连续退火工艺进行了试验研究,得出冷轧低合金高强钢 HC420LA 的再结晶温度为700 ℃,工业化生产时最佳加热均热温度为760 ℃。     

Study on static and fatigue strength of structural adhesive-bonded joints of steel sheets for automotive application

The static and fatigue strength of crush durable structural adhesive-bonded lap joints of steel sheets for automobiles was evaluated by tensile shear tests. The steel sheets used in this study were uncoated and galvannealed (GA) with tensile strength ranging from 270 MPa-grade to 980 MPa-grade and the thickness ranging from 0.7 to 1.8 mm. Also, the effects of the adhesive types were evaluated. The results are as follows: In the static tensile shear tests, when the steel sheets deformed during the tensile test, the tensile shear strength increased with the increase in the base metal properties, such as the yield strength and thickness; however, when the base metal properties were sufficiently high not to undergo plastic deformation, the tensile shear strength exhibited a constant value. On the other hand, the effect of base metal properties on the fatigue joint strength was relatively small. The static joint strength of the GA steel joints was slightly lower than that of the uncoated steel sheets; however, the fatigue strength of the GA steel joints was higher than that of the uncoated steel sheets. The coating failure of the GA was affected by the type of adhesive, base metal properties and type of test. Choosing the proper adhesive can reduce the failure of the GA coating, and the high strength steel showed fewer coating failures than the mild steel.     

先进高强度钢板的冲压成形特性及其应用

文章在研究高强度钢板成形特性、回弹特性以及拉毛特性的基础上,深入探讨了先进高强度钢板冲压过程的变形特征。研究结果表明,与传统HSLA钢板相比,DP钢和TRIP钢具有较好的应变均化能力,和较高的成形性,有利于提高零件的使用强度。钢种特性和材料参数对回弹影响显著,使先进高强度钢板尺寸精度控制难度加大。当钢板强度升高时,高强度钢板表现出更易产生拉毛的趋势。