冷轧深冲薄板的模拟成形性能研究

通过拉深、扩孔、锥杯、凸耳等模拟成形性试验,全面比较了IF、08Al、SPCC3种深冲钢板的成形性能。试验结果表明,IF板的成形性能最好,08Al板其次,SPCC板最低。同时,从力学角度分析和比较了各钢板在相应模拟试验中的成形难易程度。     

1000MPa级DP钢的成形特性试验

对宝钢产1000MPa级冷轧双相钢和热镀锌双相钢的材料特性和成形特性进行试验,深入分析钢板的力学性能、扩孔性能和成形极限。研究表明,宝钢1000MPa级超高强钢板具有较好的力学性能,其延伸率和扩孔率与国外同类产品相近,成形极限试验测量得到的FLD0为18%,低于采用软钢经验公式计算值。摩擦试验表明,冷轧GI板表面摩擦系数明显低于热镀锌CR板,此外,涂油对CR板表面影响较小,但对GI板表面有较大的影响。     

退火温度对21Cr-0.3Cu铁素体不锈钢组织性能的影响

通过光学显微镜、拉伸试验及背散射电子衍射,研究了退火温度对21Cr-0.3Cu超纯铁素体不锈钢显微组织、力学性能、成形性能和微观织构的影响。结果表明,试验钢经970 ℃退火时,晶粒细小且均匀,组织处于完全再结晶状态。退火温度低于970 ℃时,再结晶不完全;退火温度高于970 ℃时,再结晶晶粒异常长大,这两种情况均出现混晶组织。试验钢在970 ℃退火时,综合力学性能最佳,抗拉强度为473 MPa,屈服强度为315 MPa,伸长率35.7%。随退火温度的升高,试验钢的平均塑性应变比r_m值先增加后减少。当退火温度达到970 ℃时,r_m可以达到最大值1.82。γ纤维织构密度变化趋势与r_m值一致,退火温度为970 ℃时,γ纤维增强明显,此时其取向密度达到最大值f(g)=20.56,成形性能最佳。     

双相钢板应变强化和烘烤硬化特性试验研究

近年,国内高强度钢板品种开发取得了快速的进步,双相钢等先进高强度钢板日趋系列化,同时强度等级也有了大幅度的提高。但是与国外先进钢厂相比,国内先进高强度钢板的推广应用步伐相对缓慢。该文针对C-Mn钢、高强度低合金钢、590MPa双相钢和780MPa双相钢的应变强化特性和烘烤硬化特性开展了深入的试验研究。研究结果表明,与C-Mn钢和HSLA钢相比,双相钢应变强化和烘烤硬化效应十分显著,有利于提高零件的使用强度。     

Influence of nonmetallic inclusion characteristics on the mechanical properties of rail steel

An extensive investigation has been carried out on six commercial heats of pearlitic rail steel to study the influence of nonmetallic inclusion characteristics on the tensile, fatigue, and fracture toughness properties. The steels investigated were made through the basic oxygen furnace (BOF)-continuous casting route and rolled in the rail and structural mill into 90 kg/mm² ultimate tensile strength (UTS) grade rails. While tensile properties (yield strength [YS], UTS, and elongation) of the rail steels investigated were found to be insensitive to inclusion type and volume fraction at their present level (0.23 to 0.45%), the fracture toughness and high-cycle fatigue properties were found to be inclusion sensitive. The fracture toughness values of the steels were found to range between 42.33 and 49.88 MPa √m; higher values, in general, were obtained in heats exhibiting lower volume fractions (0.15 to 0.19%) of sulfide inclusions. The high-cycle fatigue limit, i.e., stress corresponding to 10⁷ cycles, was found to be higher in cleaner steels, particularly in those with lower volume fractions of oxide inclusions. This phenomenon was corroborated by scanning electron microscopy (SEM) observations of fracture surfaces, where oxide inclusions in particular were found to be instrumental in crack initiation. Although fatigue life did not show any direct correlation with the volume fraction of sulfides, elongated MnS inclusions were sometimes observed at crack initiation sites of fatigue-tested specimens.     

镀锌家电板成形性能试验研究

研究了首钢生产镀锌家电板的力学性能，胀形性能，成形极限及实冲情况。结果表明，该家电板具有良好的力学性能和成形性能。实冲零件质量良好。     

Comparison of formability of steel strips, which are used for deep drawing of stampings

The paper concerns evaluation and comparison of formability of steel strips, which are used in Czech Republic for production of intricate deep stampings. The properties of sheet-metal which have the principal influence upon the success of deep drawing or strech-forming are described. Two methods used for determination of strain-hardening exponent are compared. It is concluded, that the method according to SN 42 0436 is suitable for approximation of stress-strain curve of given sheet-metal only from point of view of functional values. The values of strain-hardening exponent, calculated by the method using maximum uniform elongation, are more strongly correlated with pure stretchability than are the values of it, calculated by the method according to SN 42 0436.     

测定钢板成形极限的三种方法与应用比对

近邻破裂点离线测量法是成形极限试验用来观察成形极限应变的最常用方法。随着光学视频技术在成形试验中的应用,通过测量网格临界破裂时应变的临界破裂点原位测量法,以及ISO12004标准中新推荐的破裂区截面线拟合法,均已进入到成形极限的测量领域。这两种测定成形极限的新方法弥补了紧邻破裂点测量法带来的近似效应和误差,极大提高了成形极限曲线的可信度。文章运用3种不同的方法,对一种高强度冷成形用钢进行成形试验,测定其在近似平面应变状态下的成形极限,并对结果进行比较。     

典型汽车用钢板应变速率敏感性实验

为研究应变速率对汽车钢板冲压成形性能的影响,采用单向拉伸实验,对3种不同强度级别的典型汽车用钢板进行应变速率敏感性研究。结果显示,电镀锌BSUFD+Z钢板的屈强比对应变速率的敏感性最大,其次是烘烤硬化BH220钢板,敏感性最小的是双相DP600钢板;双相DP600钢板的硬化指数具有较大的应变速率敏感性,而电镀锌BSUFD+Z钢板和烘烤硬化BH220钢板的硬化指数对应变速率的敏感性较低;3种钢板的应变速率敏感指数,电镀锌BSUFD+Z钢板最大,烘烤硬化BH220钢板次之,双相DP600钢板最小。研究结果为汽车钢板快速冲压生产工艺设计提供了参考。     

回火温度对低合金双相钢的组织和力学性能的影响

通过对低合金双相钢Fe-0.14C-0.9Mn-0.025Nb不同温度的回火处理,通过控制组织的碳化物的析出和位错变化,研究回火温度对双相钢组织和性能的影响.试验表明:随着回火温度的增加,MA岛逐渐分解,逐渐析出颗粒状碳化物；显微硬度和抗拉强度降低,屈服强度先增后降,断后伸长率、均匀伸长率和加工硬化指数先降后增,冲击吸收能量逐步增加.     

退火和退火-时效工艺对热轧中锰钢组织及性能的影响

分别采用退火和退火-时效工艺来调控热轧态Fe-10.2Mn-0.41C-2.2Al-0.6V中锰钢中的奥氏体体积分数、奥氏体稳定性及VC析出来优化中锰钢的力学性能组合。结果表明,经退火-时效热处理后试验钢的屈服强度、抗拉强度和伸长率均获得提升。大量的纳米级VC颗粒是促进中锰钢屈服强度增加的主要因素。     

Effect of coating characteristics on friction and formability of Zn-Fe alloy electroplated sheet steel

The effects of coating composition and coating weight on friction characteristics and formability under different deformation modes, as well as their mechanisms, were studied on zinc-iron electroplated drawing-quality special-killed (DQSK) sheet steels. Friction tests, simulative formability tests, and coating characterization were performed. The experiments revealed that the iron concentration of the coating has a tremendous effect on friction in the deep-drawing operation, but only a slight effect in the stretching operation. Uniaxial tension tests indicated that both coating weight and coating composition affectn-value andr-value. The dependence of friction characteristics,n-value, andr-value on iron concentration is related to the variation of coating hardness caused by the variation of iron concentration in the coating.     

冷轧工艺对301L不锈钢组织及性能的影响

对1.5 mm厚的301L不锈钢板材进行多道次冷轧试验,得到压下率分别为20%,30%,40%的板材;通过对冷轧板材的拉伸试验、金相分析、SEM分析、XRD衍射分析及硬度测试,研究冷轧压下率对301L不锈钢组织及性能的影响规律。研究表明,随着冷轧压下率的增大,301L不锈钢中的应变诱发马氏体会逐渐增多,材料的屈服强度由789 MPa提高至1260 MPa,抗拉强度由977 MPa提高至1317 MPa,显微硬度则提高了120 HV;材料出现晶粒碎化现象,产生细晶强化;同时,由于301L不锈钢中的马氏体相变,20%压下率的301L不锈钢拉伸应变硬化指数要高于30%压下率的301L不锈钢。     

Influence of impact energy on work hardening ability of austenitic manganese steel and its mechanism

To further understand the hardening mechanism of austenitic manganese steel under actual working conditions,the work hardening ability was studied and the microstructures of austenitic manganese steel ...     

Influence of strain rate on microstructure and formability of AZ31B magnesium alloy sheets

The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^?4, 10^?3, 10^?2, 10^?1 s^?1 at 200 °C. The results show that the volume fraction of dynamic recrystallization grains increases and the original grains are gradually replaced by recrystallization grains with the strain rate decreasing. A larger elongation and a smaller r-value are obtained at a lower strain rate, moreover the erichsen values become larger with the strain rate reducing, so the formability improves. This problem arises in part from the enhanced softening and the coordination of recrystallization grains during deformation.     

超快冷对高强度Mn-B钢板组织与性能的影响

将Mn-B系高强度贝氏体钢板轧成25 mm规格采用超快冷系统进行加速冷却。冷却后钢板可以获得710~850 MPa的高抗拉强度,但断后伸长率仅12.0%~13.0%。通过光学显微镜、扫描电镜、透射电镜等对钢板及单向拉伸断口的显微组织、析出物等进行分析。结果表明,在超快冷条件下钢板表层可以获得广泛的板条贝氏体组织,板条贝氏体中的渗碳体分布于板条及板条束间的界面上,形成类似珠光体的片层结构,明显提高钢板强度。在变形过程中,渗碳体内易生成微裂纹,降低基体组织的加工硬化能力,导致断后伸长率偏低、钢板塑性下降。     

镀锌钢板的锌层附着特性及成形性研究

文章针对4种不同种类的镀锌钢板开展了锌层附着特性和成形特性研究,深入分析了镀锌钢板的抗粉化和剥落性能以及锌层对钢板成形极限和极限拱顶高的影响。结果表明,对于镀层强度较高的热镀锌铁合金钢板,其抗粉化和剥落性能较差。且随着温度的升高,镀锌板的锌层脱落量增加。锌层对钢板成形极限的影响很小,但对极限拱顶高有一定影响。     

汽车6016-T4铝合金板材成形性能实验及数值模拟

利用实验与数值模拟结合的方法研究6016-T4铝合金板材室温下材料的成形性能。通过铝合金板材室温拉深实验,得到极限拉深比为1.913;针对铝合金板材成形实验过程,采用DYNAFORM有限元分析软件进行模拟分析,得到极限拉深比为1.925。实验结果与模拟结果表明,随着板料尺寸的增加,成形板料圆角区域的厚度逐渐减小,凸模行程曲线、拉深深度和板料厚度分布对比的结果显示,模拟结果与实验结果具有良好的一致性,进一步为汽车铝合金覆盖件成形工艺研究分析提供参考。     

Effect of the annealing temperature on the mechanical properties,formability and corrosion resistance of hot-rolled duplex stainless steel

The industrial sequence for obtaining duplex stainless steels by rolling includes two annealing steps: one intermediate after the hot rolling, and the final one after the cold rolling. The aim of this paper is to study the consequences of deviations from the current industrial intermediate annealing temperature. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), together with X-ray diffraction (XRD), were used to investigate the microstructural changes of the steel. The only transformation observed was the precipitation of sigma phase for all the considered annealing conditions. A decrease in the heat treating temperature augmented the percentage of sigma phase, which generated an increase in tensile strength and hardness, concurrently with drastic reductions on ductility and impact resistance. In addition, compression testing and cold rolling at laboratory scale were done in order to compare the formability of the steel subjected to the new annealing conditions with the current industrial rolled products. On the other hand, the pitting potential of the thermo-mechanically treated samples was determined by potenciodynamic polarization tests. The electrochemical results showed that sigma phase markedly decreases the pitting potential. SEM observations revealed that pits appear mainly in regions adjacent to sigma phase, where secondary austenite forms.     

Forming characteristics of coarse and fine-grained AA 2024 aluminum alloy sheet

The forming behavior of Al-Cu-Mg-Mn alloy 2024 sheet with fine, equiaxed and coarse, elongated grain structures was characterized in the O temper (fully annealed) and W temper (solution heat treated and quenched) conditions. The fine-grained materials had better biaxial stretching capabilities in both tempers. The fine-grained O temper also had superior drawing and plane-strain stretching properties. For the O temper, conventional tensile forming indicators such as elongation and strain ratio correlated with ball punch depth, forming limit strains, and limiting draw ratio. Such correlations were not apparent in the W temper, however, nor could the two tempers be compared on the basis of tensile data alone.