冷轧带钢切边圆盘剪装置的优化与改进

针对冷轧带钢切边后产生的边部梗压印缺陷,结合切边圆盘剪的剪切原理,设计了一种圆盘剪复合衬套,其采用100Cr钢质内圈和MC尼龙外圈复合结构组成,取代原纯钢质衬套,使圆盘剪在剪切带钢过程中由钢性接触转变为弹性接触,从而避免了带钢边部梗压印缺陷的产生,提高了切边质量与剪切里程数,降低了圆盘剪备件成本,提高了生产效率。     

Regression analysis of surface roughness and micro-structural study in rotary ultrasonic drilling of BK7

Ceramic materials have tremendous demand in manufacturing sectors. However, poor machinability impedes their widespread applications on an industrial scale. BK-7 falls in the same category and is normally processed by ultrasonic machining. But nowadays rotary ultrasonic machining is overtaking the ultrasonic machining for processing difficult to cut materials because of its superlative material removal mechanism. Current study aims to improve the surface quality of BK7 by studying the effect of input factors on surface roughness during rotary ultrasonic machining. Response surface methodology has been used to observe the effect of input variables ― spindle speed, feed rate and ultrasonic power ― on surface roughness (SR). Thereafter, central composite design was employed to estimate the regression coefficients of quadratic model for surface roughness. Fitness of developed quadratic model was checked by ANOVA test, which also revealed that all the model terms of input factors were significant except feed and speed interaction. Feed has the maximum impact over surface roughness descended by moderate impact of power and spindle speed. The study was further reinforced on observing the surface integrity of processed surfaces using scanning electron microscopic images. Mixed flow of material was observed to occur at lower feed rate and higher levels of rpm and ultrasonic power.     

Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ∼100 displacements per atom

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradation of material properties under intense neutron irradiation is a critical feasibility issue. This study evaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite, reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-Nicalon^TM Type S SiC fiber, following neutron irradiation at 319 and 629?°C to ～100 displacements per atom. Both the proportional limit stress and ultimate flexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at 319?°C, the quasi-ductile fracture behavior of the nonirradiated composite became brittle, a result that was explained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphase due to irradiation. The specimens irradiated at 629?°C showed increased apparent failure strain because the fiber/matrix interphase was weakened by irradiation-induced partial debonding.     

Mullite-bonded SiC-whisker-reinforced SiC matrix composites: Preparation,characterization, and toughening mechanisms

A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al₂O₃. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO₂–Al₂O₃ triple-layered structure were obtained after the Al₂O₃-coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8?±?1.4%, flexural strength of 533.3?±?18.2?MPa, fracture toughness of 13.6?±?2.1?MPa?m^1/2, and Vickers hardness of 20.6?±?2.5?GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface.     

NiTi-W原位复合材料的马氏体相变与性能

为获得高性能NiTi基记忆合金复合材料,通过熔炼、锻造、拔丝等手段获得一种NiTi-W原位复合材料。利用SEM扫描电镜观察材料显微组织;DSC测试材料的马氏体相变行为;利用WDT II-20万能拉伸试验机测试材料的力学性能。SEM分析结果显示,拔丝加工使W纤维直径细化至几微米,甚至亚微米级别,在NiTi基体中沿拔丝方向一致排布。DSC测试结果显示,材料经不同温度退火后展现出复杂的可逆马氏体相变行为,在某些升、降温曲线上出现多个吸放热峰现象。拉伸测试结果显示,600 ℃退火样品经适当的预拉伸变形后,屈服强度会大大增加,由~200 MPa提升到~800 MPa,断裂应力超过1 GPa,断裂应变高达40%,材料展现出优秀的线性超弹性,是一种集高强度、高塑性、高线性超弹性于一身的高性能材料。     

扩散退火和热轧温度对钛铜界面结合强度的影响

对热挤压的钛铜复合棒进行扩散处理,研究扩散退火温度及保温时间对界面结合强度的影响,并通过测试Ti和Cu在高温下的拉伸性能来选择较为合适的热轧温度。结果表明:扩散退火可有效促进界面处金属原子的扩散和增强结合强度,当扩散退火在780～800 ℃/30 min时复合界面的结合强度最高;钛铜复合棒热轧温度应选择780 ℃较为合适,此时Ti、Cu的强度和塑性指标相近,利于热轧时的均匀变形;钛铜复合棒的热轧结合机理可用N.Bay理论、热作用机制及位错学说进行解释。     

豫西地区三软煤层选煤系统的优化设计

豫西地区三软煤层由于底板为泥岩、砂质泥岩、泥质粉砂岩,顶板为泥岩、砂质泥岩等原因,采用放顶煤工艺进行采煤时原煤发热量起伏较大,原煤发热量较差时小于12.56 MJ/kg。而依据河南省相关政策要求,商品煤发热量应达到18.84 MJ/kg以上。为了满足销售要求,必须对原煤进行筛选。以河南永华能源嵩山煤矿为例,通过科学的数据分析和严谨的工艺设计,充分利用现有条件,选用复合干法分选排矸技术,较好地解决了商品煤发热量不足的问题。对解决豫西地区三软煤层同类问题具有借鉴意义。     

钢中非金属夹杂物标准评级图法解析及修订建议

从标准图谱、术语、夹杂物类型和系列的划分、级别评定和检验方法深入剖析了GB/T 10561-2005《钢中非金属夹杂物标准评级图显微检验法》存在的问题，提出对标准评级图片修订和评定方法完善的具体建议，以规范评定方法，消除歧义，推进标准修订工作。     

Cu-Al2O3弥散强化铜合金接触线的组织和性能

采用内氧化法制备的Cu-Al2O3弥散强化铜合金接触线,并对其组织和性能进行了研究。结果表明:Cu-Al2O3合金接触线抗拉强度达到568 MPa,导电率达到84%IACS,载流量达到764 A,技术性能优于TB/T 2809-2017标准中Cu-Cr-Zr合金接触线的技术要求;其强化机制主要为细晶强化及Al2O3粒子引起的弥散强化和应变强化;由于合金基体内Al2O3粒子不均匀,导致合金内部组织的不均匀,从而引起显微组织的尺寸不均和拉伸断口混合断裂的断裂方式。     

时效处理对高频感应熔覆TiC/Ni复合涂层的组织及性能影响

为了改善抽油杆材料的表面性能,采用高频感应熔覆技术在其表面制备了TiC/Ni复合涂层。采用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)等研究了涂层经固溶及不同时间时效处理后的显微组织及物相组成,并利用显微硬度计及摩擦磨损实验测试了时效后涂层的性能变化。结果表明:经固溶时效后的涂层并未出现明显缺陷,涂层主要以γ-Ni固溶体、Ni的化合物、CrB、碳化物以及δ相等硬质颗粒组成;时效后涂层的最大硬度达到928.2 HV0.2,相比时效前提高了4%,最低磨损量为48.9 mg,比基材减少了62%,在时效4 h后,涂层的综合性能最好。