焊缝中氢的扩散行为及影响因素

 扩散氢会在焊缝中引起氢脆、延迟裂纹等,导致结构产生低应力断裂。为了研究氢的扩散行为,采用水银法和气相色谱法测定了逸出的扩散氢量,并采用真空抽取法测试了不同温度下残余氢的释放量。试验表明,扩散氢量不受焊道数量的影响,它的逸出时间随焊道数的增多而增长,逸出速度随合金含量的增多而降低。随着焊后冷速的降低,冷却过程中逸出的氢增多,测定出的扩散氢量减少;测氢试样在100~200℃保温时,逸出氢的总量变化不大,但逸出时间随温度的升高而明显缩短。残余氢量与扩散氢量的多少无关,它与焊缝的含氧量、组织和硬度等有关系。     

水银法测定焊缝扩散氢的影响因素

采用水银法研究了环境湿度、烘干温度、保护气体露点等测试条件对焊缝扩散氢含量的影响,分析了我国碳钢及低合金风焊条中的扩散氢含量,并且与国外焊条的扩散含量进行了对经     

金属中氢的分析技术进展

介绍了金属中氢的存在状态及其对材料的影响。总结了近年来金属中氢的检测方法及目前实验室常用的测氢设备以及分析方法。除常规取样、实验室检测方法外,由于工艺的要求,在线检测手段发展越来越快。钢液、铝液中氢的在线测量技术越来越多地应用到实际生产中,并已经研制出可在线同时检测钢液中氧、氮、氢3种气体元素的检测设备。熔敷金属中氢的检测已经逐渐由热导法替代了传统的水银法和甘油法。     

钢中钛与氢的作用

利用电化学氢渗透技术研究了热轧碳钢和含钛钢的氢渗透,得出如下结论:①当少量钛在钢中以弥散TiC相分布时,氢陷阱能为20.0kJ/mol,远远大于碳钢的氢陷阱能;②当少量钛在碳钢中以弥散TiC形式存在时,能大大增加氢扩散激活能,因此氢扩散系数明显减小;③在某些应用领域,含TiC沉淀相的低合金钢是较好的抗氢材料。     

金属薄板的氢扩散试验

 金属板材氢扩散计算试验选用材料为40Cr及4Cr13轧制板材,运用电化学方法进行氢扩散试验。通过对薄板进行表面处理,且进行预镀镍及镀镍的处理,最终进行氢扩散系数的测定试验,并根据氢扩散试验得到的数据参数进行氢扩散系数的计算,最终得到两种钢的氢扩散系数。氢扩散计算试验适用于各种不同金属材料氢扩散系数的测定,为检测钢在使用过程中氢的积累提供基本参数及计算依据,且对于材料中氢的定量计算起到至关重要的作用。通过对两种材料成分及扩散系数的比较,进一步研究金属中合金元素质量分数对氢在金属中扩散的影响作用。     

高强钢焊接氢致裂纹断口微观形貌的研究及模式化

采用插销实验和扫描电镜观察方法详细研究了焊缝扩散氢含量和非金属夹杂物对10Ni5CrMoV低碳中合金高强钢焊接热影响区氢致裂纹断口微观形貌的影响。结果得出,扩散氢含量是影响氢致裂纹断口微观形貌的主要因素,在插销净截面应力300～800MPa的范围内,加载应力对延迟扩展区断口形貌无明显影响。钢中硫化物夹杂的增加使扩展区形貌从IG_(HE)向MVC_(HE)转变,而含氧化物夹杂钢则转为QC_(HE)。作者提出了一个新的适于解释氢致裂纹扩展第Ⅱ阶段断口微观形貌的竞争开裂模式,从而从氢致裂纹本质机制上圆满说明了上述实验结果。     

利用氢扩散诱导相变进行钛的低温精密焊接

正在钛制精密机械及装置的制造中,要求开发并建立一种无变形且尺寸精密的焊接技术。由于电弧焊、激光焊等焊接技术需要将钛熔融,很难用于精密焊接,而扩散焊等固相焊接是一种可望用于钛的精密焊接方法。这种固相焊接通常要在钛的β相变     

利用HTDS对钢材料中氢扩散行为的分析研究

介绍了利用升温测氢装置(HTDS)进行的钢材料中扩散氢及非扩散氢定量区分与检测的方法,绘制出不同温度下氢扩散速率曲线图,找出最佳扩散温度区间。通过对管线钢服役中失效样品中扩散氢和不易扩散氢的测定,为失效分析提供有力判据。     

焊接接头氢陷阱性质及捕获氢能力

用电火花切割方法，制备出１０ＳｉＭｎＮｉＣｒ钢焊接接头母材、熔合线（含ＨＡＺ区）及焊肉的特殊试样。用真空加热炉分别作晶界、夹杂陷阱氢逸出处理，用离子探针测氢逸出量（或捕获量），结果是（１）焊接接头的晶界陷阱及夹杂物陷阱捕氢量依焊缝、ＨＡＺ、母材次序从高到低；（２）晶界陷阱是弱陷阱，夹杂陷阱是强陷阱。     

铁基激光熔覆层的开裂行为及开裂机理研究

本文通过研究铁基熔覆层裂纹的开裂形貌、扩展方向、裂纹源、断口特征等开裂行为探讨了其开裂机理.结果表明：熔覆层表面裂纹起源于熔覆层和基体结合处,垂直于焊道向表面扩展,且贯穿整个熔覆层表面,呈沿晶开裂特征;熔覆层中存在的孪晶,可提高熔覆层的塑性和韧性,降低了熔覆层的开裂倾向;熔覆层中的δ铁素体,可以增强熔覆层的抗热裂纹能力;开裂的熔覆层δ铁素体中存在大量体心立方结构的含Si复杂固溶体（C-Fe-Mn-Mo-Si）,且δ铁素体含量较少,是导致其韧性下降、裂纹出现的主要原因.     

酸轧入口步进梁移行缸底座设计缺陷分析和改进

针对酸轧机组入口步进梁移行缸底座在运行过程中的拉弯脱焊现象,通过计算验证焊接的设计强度是否符合要求,分析了焊接的理论强度在实际应用中遇到的具体问题,并通过改造移行缸底座结构、增加螺栓联接,使问题得到最终解决。     

1350m^3高炉旋流顶燃式热风炉的改造

分析了宣钢1350m3高炉应用的旋流顶燃式热风炉的使用过程中存在的问题,通过改造,提高了热风炉的使用寿命和效率,满足了高炉生产的要求。     

油毡屋面开裂的原因及预防措施

本文主要介绍了工业与民用建筑屋面防水层开裂的原因。针对永平铜矿建筑屋面的防水层在结构层受到各种荷载作用时 ,由于基层 (找平层 )和所用材料的不足而导致防水层的开裂的成因 ,阐述了防水屋面所用材料的性能及对材料的要求、基层的处理以及屋面防水层的施工方法和质量保证措施     

Crack Bridging in Polymer Nanocomposites

Carbon nanotube reinforced composites offer enhancements in fracture properties since the reinforcing nanotubes provide a bridging mechanism to resist crack growth. In this paper, a study of crack bridging by nanotubes in a nanotube-reinforced polymer composite is presented. The process of crack bridging is idealized as normal pullout of the participating nanotubes from the polymer matrix. The resistance to crack growth due to bridging is taken as the aggregate of the resistance offered by all the nanotubes, ignoring any interaction among the nanotubes themselves. The pullout of a single nanotube from the polymer matrix is modeled as an axisymmetric, nearly one-dimensional problem. This is done by assuming that fracture along the nanotube–polymer interface is dominated by shear openings, and that the nanotube behaves as a rigid body. When the polymer is a linear elastic material, the force–displacement relation for pullout is obtained as a function of dimensionless variables representing the interfacial fracture energy and the pullout length scale. Applying the correspondence principle, the elastic results are extended to the case where the polymer is a linear viscoelastic material with a single relaxation time. The force–displacement relation is then a function of the viscoelastic properties of the polymer and the pullout velocity as well. Using these results, the apparent enhancement in the fracture energy of the composite is obtained. This provides a guideline to design these composites for desired fracture properties in terms of the interfacial strength of the nanotube–polymer interface and the volume fraction of the nanotubes. Results of numerical simulations of nanotube pullout are compared to the predictions of the analytical model.     

Effective Toughness of Damaged Solids Containing Ribbon Cracks

The crack-tip toughness of materials with two-dimensional random orientation of ribbon cracks is evaluated theoretically. The effective elastic moduli reduce when the cracks exist within the isotropic material so as to enhance the material toughness. The results show that the crack density and the Poisson ratio of the matrix dominate the behavior of the overall effective toughness. As crack density η = 1, the toughness increment is 0.44–0.48 of the original toughness approximately, but three out of five moduli, μ12, μ23, and κ23, reduce at least 0.57 of their moduli. The explicit forms of the crack-tip toughness and five transversely isotropic moduli of the material containing ribbon cracks are also shown.     

电子束焊接钼及其合金

通过与熔铸钢和钼铼合金的对比，表征出了粉末冶金生产的同种金属与合金的电子束可焊性，组织和机械性能。结果发现，粉冶材料的焊缝不仅具有作为高温材料的很大可能性，而且有潜力用作结构零件。     

WKz─4型挖掘机中减速机大齿轮断齿的修复

介绍了大齿轮断齿的补焊修复新工艺,该工艺简便易行,耗费低廉,效果良好。     

Shanghai’s Experience on Utilizing the Rubblization for Jointed Concrete Pavement Rehabilitation

As agencies continue looking for cost-effective methods to rehabilitate deteriorated jointed concrete pavement (JCP), rubblization using a resonant breaker has been experimented by the Shanghai Municipal Roadway Authority (SMRA). It was demonstrated that rubblization using a resonant breaker offers a viable option for the SMRA because the rubblized pavement sections have been performing very well with no visible distress. Based on field observation for a typical hot mix asphalt concrete (HMAC) overlay on a nonrubblized JCP, it was found the treatment normally would have reflective cracking for the same overlay thickness in the first three years. Besides the cost advantage over the reconstruction, a resonant breaker also had yielded the minimum disturbance during the rubblization. It was observed that it was very effective to use water during compaction on a rubblized JCP surface to improve compaction efficiency and to control dust. Furthermore, there is no need to apply a prime coat before the HMAC overlay, as there was no detrimental effect that could be identified. The average rubblized JCP moduli were found to be 1,323?to?1,375?MPa, which are within the range reported in the literature. It was believed that there were high possibilities to increase rubblized JCP moduli without sacrificing the performance by increasing the particle size, because a reduction of 200?mm of HMAC was observed when rubblized JCP increased from 345?to?3,445?MPa at a subgrade modulus of 138?MPa and traffic of 30 million ESAL. However, further research is needed to optimize the rubblized JCP moduli in an attempt to reduce overlay thickness without creating reflective cracking.     

9Cr18轧制开坯工艺的探讨

主要介绍9Cr18这类高碳高铬马氏体不锈钢，采用“电炉（EF＋LF＋VD）＋轧制开坯”的生产工艺路线，探讨解决轧制开坯开裂的工艺问题，进而为我公司利用“这一生产方式”开发这类产品的成本优势，提升产品市场竞争力、拓展市场起到积极的作用。