60Mn环件断裂分析

60Mn环件在装配150h后发生崩裂.利用断口分析、化学成分分析、显微组织检验以及有限元计算对断裂件进行了分析.结果表明,环件中存在白点,白点在装配应力和内部氢压的作用下发生滞后扩展,当白点裂纹扩展到临界尺寸时,裂纹尖端的应力强度因子超过零件材料的断裂韧度,从而发生崩裂.     

高耐蚀性热镀锌板的钝化处理工艺探讨

介绍了热镀锌板钝化膜的形成机理 ;针对攀钢热镀锌板出现白锈、黑斑等问题 ,分析了钝化液pH值、添加剂及操作条件对钝化膜质量的影响 ,同时提出了改进热镀锌板耐蚀性能的措施     

高铬白口铸铁复合孕育的作用及动力学条件

采用V渣+Ti+Zn对高铬白口铸铁进行复合孕育。在炉内、炉外实行“二步法”处理并按孕育合金异质形核的生核能大小设计分级处理的顺序,起到了控制碳化物的析出量和改善析出形态、净化铁液、净化晶界、细化晶粒等良好的孕育效果。     

Effects of secondary carbide precipitation and transformation on abrasion resistance of the 16Cr-1Mo-1Cu white iron

The relationship between secondary carbide precipitation and transformation of the 16Cr-1Mo-1Cu white iron and abrasion resistance were investigated. The results show that secondary carbide precipitation and transformation at holding stage play an important role in the hardness and abrasion resistance. After being held for a certain time at 853 K for subcritical treatment, the grainy secondary carbide, (Fe,Cr)₂₃C₆, precipitated first and then Fe₂MoC or MoC carbides precipitated in the alloy, both of which improve the bulk hardness and abrasion resistance of the alloy. The reasons for these improvements are the secondary carbide precipitates from the austenite and the retained austenite transforms into the martensite, both make the matrix strengthen. So the matrix has more effective support to the harder eutectic carbide against exterior abrasion. With expanding the holding time, the in situ transformation from the granular (Fe,Cr)₂₃C₆ carbide into laminar M₃C carbide causes the formation of the pearlitic matrix and an associated decrease of the alloy abrasion resistance.     

热连轧机轧辊用多元白口铁的冶金技术

从合金设计、凝固组织、凝固顺序、相图、相转变行为和热处理特性等方面综述多元白口铁作为热连轧精轧机架工作辊的新材质的研发.结果表明,共晶碳化物的类型和形态能通过合金成分组合控制.从连续冷却转变图获得的相转变行为对热处理过程提供了有用的指导.投入实际应用时其抗磨性优于常规轧辊.     

高铬白口铸铁中碳当量对抗磨性能的影响

高铬白口铸铁的共晶显微组织与普通白口铸铁的共晶组织不同,其中不连续的条块状共晶铁、铬碳化物M7C3占25%左右,与富铬的二次碳化物位于金属基体奥氏体或其转变产物中,而后者的M3C碳化物能占到48%,可看作渗硫体基体或海锦状渗碳体,里面镶嵌奥氏体转变产物,所以共晶型高铬白口铸铁的韧性比普通共晶型白口铸铁好,共晶组织中碳化物的短小空间对共晶奥氏体基体起到良好的保护作用,在高应力磨料磨损条件下,过共晶高铬白口铸铁中的大块状初生M7C3碳化物能很好地抵抗磨粒对抗磨件施加的法向压力和切向剪切力,不易断裂,故而抗磨性能较好.     

离心铸造CrMoWVNb白口铸铁轧辊的研究

应用离心铸造方法：以Cr,Mo,V,Nb为主要合金元素，研制成功了CrMoWVNb白口铸铁轧辊，分析了合金元素在轧辊中的作用，指出在轧辊中加入适量稀土和钛可细化轧辊组织，改善轧辊性能，同时还分析了轧辊生产中裂纹产生的原因，提出了消除裂纹的措施，并应用于高速线材轧机预精轧机架，使用寿命达到高镍铬无限冷硬铁轧辊的4－5倍。     

载荷对高铬铸铁磨料磨损的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验；对在不同的载荷作用下碳化物对基体的保护作用与碳化物的剥离进行了相关的分析。结果表明载荷在一定值以下磨损较为缓慢，当载荷超过一定值时，磨损急剧加剧，随着载荷的增加“尺寸较小”的碳化物首先剥离基体，当载荷继续增大时，“尺寸较大”的碳化物也剥离基体并有碎裂现象。因此，要求高铬铸铁中的碳化物不仅要分布均匀，而且尺寸也要合适。     

钒和铜对高合金白口铸铁铸态组织及性能的影响

针对磨钼矿用磨球的湿式磨损工矿条件,通过对高合金白口铸铁进行成分设计、材料制备以及相应的性能测试和组织观察,分析了不同配比的Cu和V对高合金白口铸铁铸态组织及性能的影响.研究结果表明,不同的Cu和V含量对高合金白口铸铁碳化物的形态和分布影响不同.含量为1.0%的Cu和V的该合金（12.0%Cr）,其碳化物呈现短杆状、块状,均匀弥散分布于基体中,材料的硬度、冲击韧度和耐腐蚀磨损性能得到有效提高,相对耐磨性比不含Cu、V的普通高铬铸铁（18.0%Cr）约提高了15%.     

Asymptotic stability in probability and stabilization for a class of discrete‐time stochastic systems

This paper investigates asymptotic stability in probability and stabilization designs of discrete‐time stochastic systems with state‐dependent noise perturbations. Our work begins with a lemma on a special discrete‐time stochastic system for which almost all of its sample paths starting from a nonzero initial value will never reach the origin subsequently. This motivates us to deal with the asymptotic stability in probability of discrete‐time stochastic systems. A stochastic Lyapunov theorem on asymptotic stability in probability is proved by means of the convergence theorem of supermartingale. An example is given to show the difference between asymptotic stability in probability and almost surely asymptotic stability. Based on the stochastic Lyapunov theorem, the problem of asymptotic stabilization for discrete‐time stochastic control systems is considered. Some sufficient conditions are proposed and applied for constructing asymptotically stable feedback controllers. Copyright © 2014 John Wiley & Sons, Ltd.