三催气压机入口过滤器短接开裂失效原因分析

三催气压机入口过滤器短接在很短的时间内会产生裂纹。对裂纹部位进行了宏观检验、化学成分分析、显像组织分析、扫描电镜分析、力学性能分析。分析结果得知,裂纹产生的主要原因如下:工件在含有H₂S的腐蚀介质中,法兰与接管在加工制造过程中产生焊接残余应力,在腐蚀介质与残余应力的共同作用下导致应力腐蚀,从而产生沿晶脆性开裂。针对断裂原因提出了改进方案。     

多层包扎尿素合成塔无损评价方法

利用声发射技术对一台多层包扎尿素合成塔进行了检测和整体性状况评价,并用超声相控阵成像方法对声发射集中定位源进行了复验.试验结果表明,声发射能够有效检出深环焊缝中存在的活性缺陷,超声相控阵技术能实现活性埋藏缺陷的精确定位和测量.采用以声发射技术为主,结合超声相控阵技术的无损检测方法能够实现带有深环焊缝的多层包扎容器的无损评价.     

多层包扎尿素合成塔无损评价方法

利用声发射技术对一台多层包扎尿素合成塔进行了检测和整体性状况评价，并用超声相控阵成像方法对声发射集中定位源进行了复验.试验结果表明，声发射能够有效检出深环焊缝中存在的活性缺陷，超声相控阵技术能实现活性埋藏缺陷的精确定位和测量.采用以声发射技术为主，结合超声相控阵技术的无损检测方法能够实现带有深环焊缝的多层包扎容器的无损评价.     

316L焊缝与304母材C型环试样应力腐蚀敏感性研究

采用数值模拟方法对C型环试样进行了应力分析计算,得到了C型环试样沿环向和厚度方向的详细应力分布.通过316L焊缝和304母材在沸腾氯化镁溶液中的应力腐蚀试验,分析了合金元素和应力分布对应力腐蚀性能的影响.结果表明:316L焊缝的抗应力腐蚀性能比304母材好,主要原因是316L不锈钢的含碳量较304低,并且合金元素镍和钼的质量分数较高;通过C型环试样应力腐蚀裂纹的位置和应力分布结果的分析,可以初步确定材料应力腐蚀开裂的临界应力值.     

液化气管线焊缝区开裂泄漏原因分析

对材质为20#钢的液化气管线焊缝区产生裂纹的原因进行了研究。材质化学成分检验结果符合国家标准,无冶金缺陷。对焊缝附近材料进行了取样分析,采用金相检验法检验了试验材料的微观组织及裂纹形态。裂纹起源于管线的内表面热影响区和临近热影响区的母材部位,主裂纹由内壁向外壁扩展,在主裂纹附近有大量的微裂纹。利用扫描电镜和电子探针分析裂纹中的腐蚀产物类型及其分布。研究结果表明,泄漏裂纹出现在焊缝附近,管线开裂是由应力腐蚀引起的,即碱脆所至。应力来源于焊接残余应力,碱洗液NaOH在管线中残存和管线工作温度是产生碱脆的根本原因。防止措施是消除焊接残余应力,减少管线中碱洗液NaOH的残存量,在工艺条件允许时,管线工作温度远离100℃。     

重催油浆换热器管板开裂的应力腐蚀失效

锦州石化六厂的重催油浆换热器,在投入使用半年多就在浮头管板处出现多处裂纹,裂纹大多从管束开始呈环状沿径向管板延伸,导致不能正常生产,造成较大的经济损失。介绍了此换热器的工艺条件,对开裂的浮头管板进行断口宏观形貌、微观形貌、准解理微观形貌、腐蚀产物和管桥部位裂纹分析,并得出应力腐蚀是引起重催油浆换热器管板开裂的重要原因之一。分析油浆换热器管板受力和腐蚀环境:管板在焊接残余应力、温差应力、气-液两相流的诱导振动及装配应力的相互叠加作用下,受拉应力;在高温环烷酸和高温重硫醇、重硫醚的腐蚀环境中,导致应力腐蚀开裂。     

正交层板受双向拉伸时的横向开裂

基体横向开裂是复合材料正交层板的主要损伤类型.假设正交层板在双向受拉时,基体内横向裂纹达到特征饱和损伤状态,层板在两个受拉方向上的位移都沿层板厚度按抛物线分布.分别在0°层和90°层取单元体,考虑单元体的平衡而得到平衡方程,引入平均应力和平均位移的概念,利用剪切迟滞理论研究了层板中的应力分布,推导出一组偏微分方程.当层板处于损伤的早期阶段,假设只有90°层基体开裂,从而得到平均应力和层间剪应力的解析解.     

波形膨胀节环焊缝接头裂纹分析

在波形膨胀节环焊缝接头裂纹处直接取样，进行金相、电镜等检验，结合焊接接头处工作状态的应力分析，结果表明这是一种应力腐蚀裂纹．     

物料化学爆炸引起尿塔塔体爆破可能性分析

1995年和2005年,国内发生了两起尿素合成塔(以下简称“尿塔”)塔体严重爆破事故.作者就尿塔内物料发生化学爆炸的多种可能性做了具体分析和计算,并与实际尿塔爆破事故所产生的破坏程度进行了比较.结果表明,如果尿塔未存在严重缺陷,塔内物料发生化学爆炸所产生的能量不足以造成两起事故尿塔塔体的严重爆破和周边环境的巨大破坏.因此,作者认为尿塔塔体爆破的原因是：尿塔塔体存在严重制造缺陷或者是强度层板存在严重应力腐蚀开裂,产生塔体严重破裂引发的物料蒸汽爆炸.     

水泥回转窑简体裂纹模型的建立和安全评定

回转窑是水泥生产系统的关键设备之一,其服役状况直接影响水泥的产量和质量.针对某水泥回转窑筒体焊缝沿筒体轴线方向开裂问题,对轮带与筒体进行力学分析,得出引起垫板处筒体焊缝开裂的应力主要包括弯曲应力、温度应力、残余应力等.结合断裂力学和弹塑性力学构建筒体焊缝裂纹的力学模型,按应力强度因子建立筒体焊缝的断裂判据,对裂纹进行安全评定,并通过现场裂纹统计证实了模型和评定的准确性,裂纹临界尺寸为141 mm.     

Effect of deteriorated microstructures on stress corrosion cracking of X70 pipeline steel in acidic soil environment

In order to investigate stress corrosion cracking (SCC) of X70 pipeline steel and its weld joint area in acidic soil environ-ment in China, two simulating methods were used: one was to obtain bad microstructures in heat affected zone by annealing at 1300°C for 10 min and then, quenching in water; the other was to get different simulating solutions of acidic soil in Yingtan in south-east China. The SCC susceptibilities of X70 pipeline steel before and after quenching in the simulating solutions were analyzed...     

Corrosion leaking of preheater weldment in alumina factories

Stress corrosion cracking （SCC） and anticorrosion measures of TU42C weld-joint were studied by constant load experiments and pickling experiments. The results show that in 40% （mass fraction） NaOH solution at 110℃, caustic SCC occurs in TU42C weld-joints at the applied potential of —1020 mV（vs SCE） for 3 d while at the potential of—950 mV（vs SCE） for 10 d. All the cracks are intergranular. In the 10% sulfuric acid, the cracks have the most negative self-corrosion potential —432.5 mV（vs SCE） and are active to be further corroded by the acid. Because of the same corrosion behaviour as the lab weldment, preheater＇s cracking in alumina factories is attributed to the combining actions of previous caustic SCC in Bayer solutions and continuous acid corrosion by pickling with the addition of RD. The following measures are effective to prevent the corrosion failure of preheater, such as postweld heat treatment at 620 ℃ to relax the residual weld stress, addition of CC3 and L826 as the corrosion inhibitors to improve the pickling and cleaning by the high pressure water instead of by pickling.     

随焊冲击碾压控制平面封闭焊缝残余变形研究

随焊冲击碾压是一种控制平面封闭焊缝残余应力变形及防止热裂纹的新方法,它通过2个冲击碾压轮迫使焊缝金属沿着一定的方向严生塑性变形流动,达到减小应力变形防止热裂纹的产生．试验结果证明随焊冲击碾压试件表面平整光滑,没有热裂纹．在一定的范围内,试件的最大残余变形量与气锤压力之间有一定的对应关系;在合适的气锤压力下,随焊冲击碾压法可以将薄壁构件平面封闭焊缝引起的残余变形降低到常规焊接状态的1／12以下．由于随焊冲击碾压能够将焊缝外侧周向压应力降低到结构的临界失稳压应力以下,因而减小了薄壁构件失稳变形,同时还减小了由焊缝收缩引起的焊接变形．     

Relativity between corrosion—induced stress and stress corrosion cracking of brass in an ammonia solution

The susceptibility to stress corrosion cracking (SCC) of brass in an ammonia solution with various pH values or under various applied potentials was measured at slow strain rate tests. The additive stress in the same solution was measured using two methods. The results indicate that the variation of the susceptibility to SCC with pH value or with potential is in an excellent agreement with the corrosion (passive film or dezincification layer)-induced stress. When pH≥7, the corrosion-induced tensile stress andthe susceptibility to SCC have maximum values and hardly change with increasing the pH value. However, when pH < 7, both the corrosion-induced tensile stress and the susceptibility to SCC reduce rapidly with decreasing the pH value. Both the corrosion-induced tensile stress and the susceptibility to SCC have maximum values at the open-circuit potential, decrease slightly under the anodic polarization, and reduce gradually to zero under the cathodic polarization.     

Effect of hydrogen on the stress corrosion cracking behavior of X80 pipeline steel in Ku'erle soil simulated solution

Hydrogen was a key factor resulting in stress corrosion cracking (SCC) of X80 pipeline steel in Ku'erle soil simulated solution. In this article, the effect of hydrogen on the SCC susceptibility of X80 steel was investigated further by slow strain rate tensile test, the surface fractures were observed using scanning electron microscopy (SEM), and the fracture mechanism of SCC was discussed. The results indicate that hydrogen increases the SCC susceptibility. The SEM micrographs of hydrogen precharged sample...     

An investigation of corrosion-induced stress during SCC

TEM (Transmission Electron Microscope) observations show that corrosion process during stress corrosion cracking (SCC) enhances dislocation emission and motion; and microcrack of SCC initiates when the corrosion-enhanced dislocation emission and motion reaches a certain condition. The passive film or dealloyed layer formed during corrosion or SCC can induce a large tensile stress, which can assist the applied stress to enhance dislocation emission and motion, and then SCC occurs. Experiments show that the variation of SCC susceptibility of brass,α-Ti and stainless steel with the applied potential and pH value of the solution is consistent with that of the corrosion-induced additive stress. Molecular dynamics simulations show that a dealloyed layer can generate a tensile stress; and the corrosion (dealloyed layer)-induced tensile stress can assist the applied stress to enhance dislocation emission and crack propagation.     

应力在16MnR钢—饱和硫化氢溶液应力腐蚀体系中的作用

通过分析16MnR钢在饱和硫化氢溶液中的应力腐蚀现象,发现了应力与材料自腐蚀电位的关系,分析了应力在不同应力腐蚀类型的裂纹孕育、扩展过程的作用。     

钢结构厂房横梁开裂分析与修复

针对钢结构厂房横梁翼板与端板之间热影响区开裂,用光学显微镜观察母材、焊缝、热影响区显微组织,用直读光谱仪对钢板、焊丝、焊缝的成分进行了分析。证明了横梁开裂是因为翼板中存在带状组织和夹杂物,由于焊接线能量过大导致焊接热影响区出现魏氏组织和翼板中的夹杂物进入焊缝,在焊接应力的作用下产生了开裂。并通过改进工艺和结构解决了开裂问题。     

Effect of a novel three-step aging on strength,stress corrosion cracking and microstructure of AA7085

The influence of a novel three-step aging on strength, stress corrosion cracking(SCC) and microstructure of AA7085 was investigated by tensile testing and slow strain rate testing combined with transmission electron microscopy(TEM). The results indicate that with the increase of second-step aging time of two-step aging, the mechanical properties increase first and then decrease, while the SCC resistance increases. Compared with two-step aging, three-step aging treatment improves SCC resistance and the strength increases by about 5%. The effects of novel three-step aging on strength and SCC resistance are explained by the role of matrix precipitates and grain boundary precipitates, respectively.     

Corrosion-enhanced dislocation emission and motion resulting in initiation of stress corrosion cracking

A special constant deflection device for TEM has been designed, and then change of dislocation configuration ahead of a crack tip during stress corrosion cracking (SCC) of brass in water and of Ti-24Al-11Nb alloy in methanol and initiation of SCC can he observed in TEM In situ tensile test in TEM for brass was carried out for comparison The results show that anodic dissolution during SCC can facilitate dislocation emission, multiplication and motion, and a dislocation free zone (DFZ) is formed The stress at a particular site in the DFZ, which is an elastic zone and is thinned gradually through corrosion-enhanced dislocation emission and motion, is possibly up to the cohesive strength, resulting in initiating of a nanocrack of SCC in the DFZ or sometimes at the crack tip. Because of the action of the corrosion solution the nanocrack of SCC propagates into a cleavage or intergranular microcrack rather than blunts into a void like in situ tension in TEM