双辊薄带铸轧技术的进展及热点问题评述

美国纽柯公司双辊薄带铸轧生产线2002年投产以来,已经累计生产了近50万t薄带,最薄钢带厚度0.7mm,产品可部分替代冷轧钢板.介绍了纽柯公司双辊薄带铸轧生产线的最新进展,并对一些技术特点和热点问题进行了分析和评述.     

双辊薄带连续铸轧熔池内金属流动及传热特性的研究

本文建立了双辊式薄带连续铸轧熔池内二维传热流动数学模型，使用有限元计算方法实现了控制方程及边界条件的数值求解，计算结果揭示了熔池内的流场、凝固温度场的特点和规律。     

耐候钢的化学成分和性能

综述了化学成分对耐侯耐钢性能和综合力学性能的影响，同时指出Ｃｕ、Ｐ和稀土元素对该网的有利作用。     

镍含量对高强耐候钢组织与性能的影响

针对铁路高强耐候钢的特点,本文通过调整钢中的镍含量,研究了耐候钢组织和性能的变化规律.结果表明:增加钢中的镍含量,耐候钢的组织由铁素体+珠光体向铁素体+贝氏体+珠光体转变,耐候钢的屈服强度和拉伸强度有所降低,延伸率有所提高,并且实验钢的年腐蚀速率降低,高Ni含量的耐候钢极化阻力为394(Ω·cm-2),而低Ni含量的耐候钢极化阻力为602(Ω·cm-2).     

三种非晶薄带弯曲性能与组织的研究

本文研究了三种非晶薄带的弯曲与组织之间的关系，为非晶薄带的研制了应用提供了应用的信息。     

铸轧AZ31镁合金的高温拉伸性能

研究了铸轧AZ31镁合金的高温拉伸性能和变形机制.在300~450℃条件下,分别以恒定拉伸速率10^-3 s^-1和10^-2 s^-1进行拉伸至失效试验,在真实应变率为2×10^-4~2×10^-2 s^-1的范围内进行变应变率拉伸试验.当拉伸速率为10^-2s^-1时,试样在400℃和450℃的延伸率均超过100%;当拉伸速率为10^-3 s^-1时,试样在400℃和450℃的延伸率均超过200%,该条件下的应力指数ⁿ≈3,蠕变激活能^Q=148.77 kJ·mol^-1,变形机制为溶质牵制位错蠕变和晶界滑移的协调机制.通过光学金相显微镜和扫描电子显微镜观察显示试样断口处存在由于发生动态再结晶和晶粒长大而形成的粗大晶粒,断裂形式为空洞长大并连接导致的韧性断裂.     

化学成分和生产工艺对09CuPCrNi耐候钢性能的影响

介绍了０９ＣｕＰＣｒＮｉ耐候钢优良的综合性能。通过剖析Ｃｒ、Ｐ等合金元素在不同生产工艺条件下在钢中存在的形态，提示其对钢中耐候性影响规律和机理，提出降低铬的碳化物析出量是提高耐大气腐蚀性的有效措施，发现磷作为一种很强的上坡扩散元素有极明显的表面富集疚。富集可以通过热处理工艺增加，以便进一步提高耐大气腐蚀性能作用。     

耐候钢SPA-H的耐腐蚀性能研究

采用加速腐蚀试验方法研究了珠钢生产的耐候钢SPA-H的耐腐蚀性能。结果表明:在72h的加速腐蚀条件下,珠钢生产的耐候钢SPA-H的耐腐蚀性能优于国内A厂和B厂生产的同类钢种;高钙、低硫、高钛、少量珠光体组织,有利于提高钢的耐腐蚀性能。     

凝固组织对耐候钢中磷偏析的影响

进行了高温模拟实验,通过改变凝固速率和添加稀土元素来改变耐候钢的凝固组织,研究了枝晶大小以及等轴晶率的不同对耐候钢中磷元素宏观偏析的影响.结果表明,加快冷速、添加稀土元素可以明显细化晶粒,提高等轴晶率,从而显著减轻磷元素的宏观偏析.     

超低屈强比高强耐候钢的组织与性能研究

研究了试制的超低屈强比高强耐候钢的组织与性能。结果表明:试验钢的组织由多边形铁素体+贝氏体+少量珠光体构成;屈服强度达426.9 MPa,屈强比为0.6,断后延伸率为24%,-40℃冲击功为64.4 J,耐蚀性良好。盐雾试验显示试验钢锈层主要由α-FeO(OH)、γ-FeO(OH)和Fe_3O_4构成,且随时间增加,α-FeO(OH)相对含量基本稳定,γ-FeO(OH)相对含量逐渐减少,Fe_3O_4相对含量逐渐增多。     

薄带连铸耐大气腐蚀钢高温相变过程的原位观察

对不同含磷量的耐大气腐蚀钢薄带的高温相变过程进行了原位观察。结果表明,磷对薄带耐大气腐蚀钢高温相变过程有显著影响,随着含磷量的提高,高温δ→γ相变起始温度和相变终了温度都明显降低,且相转变温度区间增大,相变过程持续时间延长,使高温的6相滞留至较低的温度;残余的δ相能有效阻碍奥氏体晶粒长大,为γ→α理的转变提供有利的形核核心,从而细化奥氏体晶粒。     

双辊铸轧Cr12钢的热处理工艺对深冲性和抗皱性的影响

将双辊铸轧Cr12钢薄板于1 000℃固溶,再采用炉冷和水淬两种方式冷却至室温,分别获得了多边形铁素体和板条马氏体两种组织,再经过相同冷轧和退火工艺,得到了两种成品板.经拉伸试验测定,水淬板的深冲性和抗皱性均强于炉冷板.组织分析发现:热处理后,水淬板内马氏体板块明显细小于炉冷板内铁素体晶粒;冷轧后,水淬板内板块间界演变...     

M2高速钢铸带组织特征及其后续处理

研究了M2高速钢在不同制备条件下的凝固组织特征以及工业铸带中碳化物在高温热处理、热变形作用下的变化,测量了在不同制备条件下高速钢的凝固速度和共晶碳化物网的厚度,采用透射电镜研究了后续高温热处理、热变形对工业铸带中碳化物相的影响,采用定量金相法分析了制备条件和后续处理工艺对铸带组织的影响.研究结果表明,双辊薄带连铸工艺可以细化高速钢凝固组织的枝晶和共晶碳化物网的厚度,改善碳化物的分布,后续高温热处理和热变形可以进一步优化工业铸带中的碳化物组织.建议在工业铸带的后续处理中同时采用高温热处理和热变形工艺以改善铸带组织.     

加钛深冲钢的工艺优化实践

为了获得深冲性能优良的冲压用冷轧板,对济钢加钛深冲钢的化学成分进行了优化设计,即降低了碳质量分数,并采用高温终轧、高温卷取、适宜的冷轧变形量(70%～75%) 等优化的热轧、冷轧和退火工艺。工艺优化后的加钛深冲钢具有比原工艺更低的下屈强比、更高的塑性应变比、更高的应变硬化指数和更多的有利的{111}取向织构比例,最终使其具有优异的深冲性能,满足了市场的深冲压要求。     

微碳深冲钢的生产工艺研究

研究了采用连续退火方式生产微碳深冲钢的工艺。通过实验室模拟的方法研究了工艺参数热轧卷取温度，冷轧压下率及退火温度对宝钢微碳深冲钢性能的影响，从而为实际生产过程的工艺参数优化提供参考。实验结果表明，热轧卷取温度为730℃，冷轧压下率在75％，退火温度在830℃时，深冲板的综合性能最佳，此时轧向试样的塑性应变比r值可达到2．0，延伸率δ可达到48％。     

Corrosion Resistance of High Performance Weathering Steel for Bridge Building Applications

 The mechanical properties, corrosion resistance and microstructures of high performance steel (HPS) was investigated by tensile testing machine, Charpy V-Notch (CVN) testing machine, cyclic immersion corrosion tester, XRD, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe micro-analyzer (EPMA). The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was composed of α-FeOOH phase and denser than that on PCS that was a mixture of α-FeOOH and Fe3O4. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS enrich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.     

Effect of Heat Treatment on Structure and Wear Re- sistance of High Chromium Cast Steel ContainingBoron

The microstructure, mechanical properties and wear resistance of high chromium cast steel containing boron after different heat treatments were studied by means of the optical microscopy （OM）, the scanning electron microscopy （SEM）, X-ray diffraction （XRD）, hardness, impact toughness, tensile and pin-on-disc abrasion tests. The results show that as cast microstructures of boron-free high chromium steel consist of martensite and a few （Cr, Fe）_7C_3 carbide, and the macro-hardness of boron-free high chromium steel is 55-57 HRC. After 0.5 mass% B was added into high chromium cast steel, as-cast structure transforms into eutectic （Fe, Cr）2B, （Cr, Fe）7 （C, B）a and martensite, and the macro-hardness reaches 58-60 HRC. High temperature quenching leads to the disconnection and isolated distribution of boride, and there are many （Cr,Fe）_23 （C,B）_6 precipitated phases in the quenching structure. Quenching from 1050 ℃, high chromium steel obtained the highest hardness, and the hardness of high chromium cast steel containing boron is higher than that of boron-free high chromium steel. The change of quenching temperature has no obvious effect on impact toughness of high chromium steel, and the increase of quenching temperature leads to tensile strength having an increasing tendency. At the same quenching temperature, the wear resistance of high chromium cast steel containing boron is more excellent than that of boron-free high chromium steel. High chromium cast steel guide containing boron has good performance while using in steel bar mill.     

Nb-V微合金化含Cu高强度耐候钢的开发和耐蚀性

通过合适的成分设计和控轧控冷工艺开发出一种综合力学性能优异的Nb-V微合金化含Cu高强度耐候钢（/%:≤0.12C,≤0.40Si,≤1.40Mn,≤0.020P,≤0.010S,0.40～0.45Cr,0.25～0.35Cu, ≥0.020Al,0.02～0.03Nb,0.02～0.03V）,并对其耐蚀性能进行了研究。该高强耐候钢组织由铁素体、珠光体和贝氏体组成,抗拉强度高达697 MPa,屈强比为0.73,断后伸长率为24.6%, -40℃纵向冲击功为70.6 J。盐雾及周期浸润试验结果表明,该钢耐蚀性能显著优于Q345B,其锈层主要由Fe₃O₄、α-FeO（OH）和γ-FeO（OH）构成,且随着时间增加,Fe₃O₄相对含量增加,α-FeO（OH）变化较小,γ-FeO（OH）减少。     

High Strength and Retained Ductility Achieved in a Nitrided Strip Cast Nb-Microalloyed Steel

The current study investigates the strengthening of an Nb-microallyed CASTRIP^® steel at 798 K (525 °C) by nitriding in a KNO₃ salt bath. Nitriding up to 1 hour dramatically increased the yield strength of the steel by ~35 pct (from 475 to 645 MPa) with no sacrifice of ductility (~16 pct). Further nitriding led to brittle fracture. Hardness profiles of the nitrided steels through the thickness reveal hard surfaces and a relatively softer core. The hardening of the shell in the nitrided steels is thought to be the combined effect of solid solution strengthening from nitrogen and dispersion strengthening from clusters and precipitates. The retained ductility is attributed to the hard-shell–soft-core structure through nitriding.     

热变形后的冷却速度对高碳铬铸钢组织和性能的影响

研究了经40％热变形后不同冷却速度下高碳铬铸钢的组织和性能。结果表明：热变形后的冷却速度与组织及性能有良好的对应关系。高碳铬铸钢变形后风冷（冷却速度约7℃／s）时，其综合力学性能最好。