Effect of RE oxide on growth dynamics of primary austenite grain in hardfacing layer of medium-high carbon steel

The flux cored wires with different rare earth oxide additions for hardfacing the workpieces of medium-high carbon steel were developed. The microstructure of the hardfacing layer was observed using the optical microscopy. The average dimension of primary austenite grains in hardfacing layer was measured by image analyzer. The primary austenite grain growth activation energy and index were calculated according to Sellars’s mode and Beck formula, respectively. Moreover, the effect of rare earth oxide on the growth dynamics of primary austenite grain was analyzed, and then discussed with the misfit theory. The experimental results showed that, by adding rare earth oxide, the average dimension of primary austenite grains in hardfacing layer of medium-high carbon steel decreased, and it was the smallest when the addition of rare earth oxide was 5.17 wt.%. Meanwhile, at this rare earth oxide addition, the primary austenite grain growth activating energy in hardfacing layer was the largest, while its index was the smallest. The calculated results indicated that the primary austenite grain could be refined because LaAlO3 as heterogeneous nuclei of γ-Fe was the most effective.     

Effects of rare earth oxide on hardfacing metal microstructure of medium carbon steel and its refinement mechanism

The electrodes for hardfacing medium carbon steel with six additions of rare earth oxide were developed in this work. By means of optical microscopy and scanning electron microscopy, the microstructure, inclusion and the fractograph of the hardfacing metal were observed. Then, the effects of rare earth oxide on microstructure and inclusions in hardfacing metal were analyzed. The effectiveness of rare earth oxide as heterogeneous nuclei of δ-Fe was calculated with the misfit theory. The results showed that, the microstructure of hardfacing metal was composed of ferrite and small amount of pearlite. The microstructure was refined at first and then coarsened with the increase of rare earth oxide addition. The fractograph was changed from brittle to equiaxed dimples, then became quasi-cleavage and cleavage gradually. The calculated results showed that, the ferrite grain size could be refined because that LaAlO3 as heterogeneous nuclei of δ-Fe was moderately effective, and the ferrite grain size was coarsened because the misfits between Ce2O3 and δ-Fe, Ce2O2S and δ-Fe were increased with futher increase of rare earth oxide addition.     

润滑剂对U-PVC管生产过程的影响

简述了PVC管材配方设计的关键因素润滑剂的特性及其对混料、生产工艺、产品质量的影响,并通过生产实践证实了润滑体系在生产中的重要性.     

结构施工阶段的钢筋定距框施工

<正>GB 50204—2002(2011版)《混凝土结构工程施工质量验收规范》中对钢筋安装位置及检查有明确要求:在同一检验批内,对梁、柱和独立基础,应抽查构件数量的10%,且不少于3件;对墙和板,应按有代表性的自然间抽查10%,且不少于3间;对大空间结构,墙可按相邻轴线间高度5 m左右划分检查面,板可按纵横轴线划分检查面,抽查     

对甲酚催化氧化合成对羟基苯甲醛的研究

以Co(OAc) 2 ·4H2 O为催化剂 ,Cu(OAc) 2 ·H2 O为助催化剂 ,催化氧化对甲酚合成对羟基苯甲酚 ,实验结果表明 ,Co(OAc) 2 ·4H2 O∶Cu(OAc) 2 ·H2 O的物质的量比为 5 ∶1,对甲酚与催化剂的质量比为 385 ∶1。     

纳米金刚石无助剂烧结的可行性分析

本文主要阐述了金刚石烧结的目前国内外研究现状,比较了国内外烧结的异同点及其优缺点。参阅大量中外文献,分析了纳米金刚石的一些特性,及用纳米金刚石无助剂烧结需要解决的问题,分析了纳米金刚石无助剂烧结的可行性。分析表明,消除吸附物,利用纳米金刚石众多的悬键、合理的工艺条件相结合,是可以实现无助剂烧结的。     

高层型钢钢筋混凝土结构二次设计施工技术

北京华汇大酒店工程主楼部分采用40根型钢钢筋混凝土柱。施工前,对型钢柱及梁节点进行二次设计,型钢上的穿孔全部在生产厂家成孔,既保证了工期又保证了质量。吊装采用两台经纬仪保证位置准确,钢柱根部采用无收缩砂浆灌注,保证钢柱生根质量,柱接头设耳板,有利于临时固定和校正。施工速度快,工程质量高。     

应急通信保障研究

近年来,应急通信保障迅速发展,但还是存在诸多的需要解决问题,本文主要介绍了应急通信的相关概念,对国内外应急通信保障的研究和发展现状进行了阐述,详细分析了我国应急通信保障存在的问题,并深入探讨了发展和完善我国应急通信保障的建议和对策。     

望京国际商业中心A3综合楼型钢混凝土结构节点的二次设计

介绍型钢钢筋混凝土柱梁节点的二次设计中型钢和钢筋的设计原则、位置关系、注意事项,满足规范和结构设计的要求,保证工程质量;压型钢板组合楼板与栓钉焊、楼板模板同步变形支撑的施工准备阶段需注意的问题,既要考虑施工方便快捷,又要考虑减少了周转材料的使用,便于现场清理。     

润滑剂对U-PVC管生产过程的影响

本文主要分析润滑剂对混料、生产工艺、产品质量的影响。