MOSi2-淬火45#钢在油润滑下的摩擦学特性

利用M-200型磨损试验机考察了MoSi2-淬火45针仪分析讨论其磨损机理.结果表明:润滑油明显改善了MoSi2材料的摩擦学性能;MoSi2与淬火45#钢对摩在120～150 N载荷范围内表现出较好的摩擦磨损综合性能;其磨损机制主要表现为疲劳磨损、磨粒磨损和轻微粘着磨损.图4,参10.     

20G钢焊接接头组织对其电化学行为的影响

分析了20G钢焊接接头的显微组织，并在33％NaOH溶液中测定了焊接接头的焊缝中心、热影响区、基体的阳极极化曲线，结果表明，20G钢捍接接头热影响区由于晶粒粗大、组织形态及成分不均匀，导致该区域成为20G钢焊接接头应力腐蚀断裂最敏感区域。     

控制冷却对CSP低碳锰钢组织和性能的影响

利用Gleeble1500热模拟机测定了薄板坯连铸连轧EAF-CSP工艺生产的低碳含锰钢经奥氏体区二次变形后的CCT曲线.实验钢含有0.17%C,1.21%Mn和0.28%Si(质量分数).研究表明:提高热轧后的冷却速度使Ar3温度降低,导致试验钢的晶粒进一步细化;冷速大于20℃/s时,出现贝氏体和铁素体的混合组织,可降低钢的屈强比;790℃终轧,550℃卷曲时出现铁素体/珠光体带状组织,提高冷速使溶质(如Mn和C)富集区在形成珠光体之前完成奥氏体-铁素体相变是避免生成铁素体/珠光体带状组织的有效方法.     

电脉冲改善HRB335钢宏观凝固组织的作用

采用正交实验方法对hRB335钢进行电脉冲处理.考虑了最大脉冲电流、频率和处理时间的搭配作用,得出实验条件下的最佳参数范围.通过和前人结果的分析比较得出电脉冲效果可能与钢种无关的初步结论,以及对树枝晶打断理论的不同观点,指出实验过程中液面波动现象是金属中溶入了过多的氧所致.     

宽带钢热连轧工作辊热辊形模型

实现工作辊热辊形的在线预报是板形控制的难题之一.采用一维有限差分方法建立了工作辊热辊形在线计算模型,并利用该模型计算了热轧过程中和下机后任意时刻工作辊温度场及其热辊形.仿真和在线应用结果表明,此在线模型计算速度快,精度高,能满足板形在线过程控制的需要.     

低温下钢-混凝土组合结构疲劳试验和极限承载力

针对钢-混凝土结合梁在青藏铁路上的应用情况,模拟青藏铁路线的温度环境,用专门研制的低温设备(最低温度能保持在-50℃以下),对由14MnNbq钢构件、直径为22 mm的栓钉(下称ψ22栓钉)和强度等级为C50的混凝土组成的钢-混凝土组合件作了低温疲劳试验和极限承载力试验.试验中,考虑了钢板的轧向和环境温度变化等因素对组合件承载力的影响,研究了低温下ψ22栓钉的破坏形式,疲劳承载力和极限承载力等问题,并将低温下的试验结果同常温下的试验结果进行了对比.研究结果表明:在同等荷载下,ψ22栓钉在-50～0℃的低温环境下疲劳寿命比在室温下的疲劳寿命长,且有温度越低,抗疲劳性能越强的趋势;钢板轧向对栓钉疲劳寿命影响很大,但对栓钉极限承载力没有明显影响;14MnNbq钢材质优良,转变温度低于-50℃.在温度为-50℃时,栓钉焊在14MnNbq钢板上对钢板材质无影响.     

Atomic-scale computer simulation for early precipitation process of Ni75Al10V15 alloy

The kinetic model for a ternary system is introduced based on the microscopic diffusion form of the phase-field equations for a binary alloy. The equation is solved in the reciprocal space. This model is used to investigate the early precipitation process of Ni75-Al10V15 by simulating the atomic pictures of the two ordered phases and calculating the order parameters of γ′(Ni3Al) phase. Simulation results show that the γ′ ordered phases precipitate from the disordered matrix by a non-classical nucleation mechanism, and the nonstoichiometric γ′ ordered phase appears first and then transforms into the stoichiometric one. Clusters of V atoms appear at the γ′ phase boundaries followed by the formation of the nonstoichiometric θ ordered phase. The farther the location from γ′ phase boundary is, the lower the order degree of θ phase is. There exist two kinds of DO22 ordered domains: a horizontal one and a vertical one, related to their adjacent γ′ phase boundaries. The model could describe the atomic ordering and composition clustering simultaneously, and any a priori assumption about the new phase structure and precipitation mechanism etc. is unnecessary.     

Computer simulation for the precipitation process of Ni75Al7.5V17.5 alloy

The precipitation mechanism of Ni75Al7.5V17.5 alloy above the L12 instability line, between the L12 and D022 instability lines and below the D022 instability line are studied using microscopic phase-field kinetic equation. This paper is aimed at investigating the effect of temperature on precipitation mechanism and morphological evolution of the alloy. Our simulations demonstrate that the precipitation is a mixed mechanism of non-classical nucleation growth and spinodal decomposition above the L12 instability line. It needs certain thermal fluctuations for nucleation and the number of θ phases is small at this temperature. The precipitation mechanism of γ'phase is congruent ordering followed by spinodal decomposition, and θ phase is a mixed mechanism of non-classical nucleation growth and spinodal decomposition between the L12 and D022 instability lines. The mechanism below the D022 instability line is similar to that between the L12 and D022 instability lines. With the decrease of the temperature, ordering and phase separation becomes fast, the dimension of γ'phase becomes small, the shape transforms from equiaxed to block, the dimension of θ phase becomes large and the shape transforms from strip to circle.     

节点板域厚度对钢框架静动力反应的影响

水平荷载作用下,节点板域的剪切变形降低钢框架结构的侧向刚度,使结构的水平位移及层间位移增大.对各种节点板域厚度的钢框架进行了水平静动力分析,结果显示,适当增加节点板域的厚度可有效地减少其不利影响.在强烈地震作用下节点板域较早地屈服,使结构层间位移过大增加,可能引起结构失效,工程中应高度重视.     

新型耐热钢NF709的研究进展

随着锅炉蒸汽参数的提高,对受热面管材的要求愈发苛刻,新型奥氏体耐热钢以其高蠕变强度、优良的抗腐蚀和氧化性能逐步取代马氏体耐热钢应用到高参数机组的过热器和再热器,但其导热性差、膨胀系数大、合金元素含量高等问题,易导致焊接缺陷。此外,奥氏体耐热钢在长期服役过程中有可能析出σ和Cr2N等有害相,降低材料的高温性能。因此,增加奥氏体耐热钢中Cr和Ni含量,通过多元合金化,以Z相、MX相和M23C6相共同复合强化,并借助合理的冷热成型加工工艺,获得适宜的晶粒尺寸和表面质量,进一步提高组织稳定性及高温性能,以满足更高蒸汽参数超超临界锅炉的过热器和再热器使用要求。