余热锅炉低温过热器E3514出口弯头开裂分析

尾气余热锅炉低温过热器E3514出口弯头发生开裂,检查发现弯头内侧发生开裂,出现了多处裂纹.通过对弯头开裂处进行检验检测,分析了弯头开裂的主要原因.结果表明:弯头处材料发生高温蠕变,生成的蠕变孔洞连接后形成裂纹,导致弯头最终发生开裂.     

二甲苯管线弯头表面裂纹失效分析

采用化学成分分析、硬度测定、金相分析、SEM观察和能谱分析等手段,对二甲苯管线弯头表面裂纹产生的原因进行了分析,并结合管线的损伤模式和检验情况,提出了管线安全运行措施。结果表明:弯头内外表面裂纹为管坯皮下气泡热推成型所致,属于制造缺陷;高温硫化物腐蚀和冲蚀是管线的主要损伤模式;打磨去除弯头外表面裂纹,控制二甲苯物料中的硫含量,严格工艺操作,能够保障管线的安全运行。     

不锈钢反应器的开裂原因分析

对一台不锈钢反应器进行检验,发现该容器存在多处裂纹,出料法兰开裂最严重.焊接记录表明,开裂处均采用二氧化碳药芯保护焊(FCAW).光谱分析表明出料法兰C、Mn含量超标,并含有一定量的Cu,由此判断材料加焊接影响造成出料法兰严重开裂.     

一台储罐外表面焊缝裂纹开裂原因分析

本文采用了磁粉检测、化学成分分析、硬度测定和金相分析等方法对储罐外表面裂纹进行了分析,结果表明,该裂纹主裂纹位于焊缝上,与环焊缝平行,裂纹中部有腐蚀坑,主裂纹两侧有次生裂纹产生,并有树枝状扩展,裂纹周边无塑性变形,具有典型的应力腐蚀开裂的特征。针对该应力腐蚀开裂的主要原因,提出了预防措施。     

紫铜板与低碳钢焊接工艺

在充分实践的基础上，介绍了紫铜板与低碳钢板在仰焊位置施焊时如何防止或减少焊透、冷热裂纹、气孔和外观缺陷和采取的工艺措施，并在理论和实际施焊两方面进行了分析和探索。     

1000 MW超超临界锅炉屏式过热器爆管原因分析

某1 000 MW超超临界锅炉屏式过热器管（12Cr1MoVG）弯头部位发生爆管事故。对爆口部位进行宏观检查、化学成分分析、金相组织检验和硬度检验,根据试验结果可知,爆管的原因是该弯头处存在氧化皮堵塞问题,使该部位介质流通面积减小,不能得到有效冷却,造成管壁长期超温运行,加速氧化皮的生成与脱落,使微观组织的严重球化,导致弯头背弧面处强度降低严重,最终在弯头背弧面拉应力最大部位发生纵向开裂。     

低合金高强钢焊接延迟裂纹的声发射信号监测及敏感特性研究

采用焊接试验和声发射监测对斜Y字型坡口SPV490Q钢焊接试件焊后延迟裂纹形成过程的声发射信号进行了分析,研究了低合金高强钢焊接延迟裂纹孕育、扩展和开裂过程的声发射信号特性。通过对不同规格和焊接条件的焊接试件进行对比,进一步得出了该材料焊接延迟裂纹开裂敏感特性。     

氧气气瓶开裂原因分析

通过宏观检测、化学分析、金相分析、扫描电镜分析等方法对开裂氧气瓶进行了检测,并根据检验检测结果对发生开裂的原因进行了综合分析。结果表明,氧气瓶开裂主要由瓶肩内腔表层折叠裂纹引起,裂纹在设备运行时多次扩展,直至部分穿透导致氧气瓶泄漏。     

2~#加氢裂化V105顶放空线焊缝开裂原因分析

从工程施工质量角度分析茂名石化2~#加氢裂化装置V105顶管道焊缝开裂在安装施工过程中,由于存在材料代用,接头组对,焊缝施焊,焊后热处理等环节控制不当,安装质量没有达到设计和工程质量标准要求,导致工程投用后焊缝开裂失效。     

A234材质弯头裂纹产生的原因分析

对ASTM A234 WPB材质弯头检测发现,在弯头外侧拱背上存在非贯穿性纵向表面裂纹。对弯头基材和焊接部位进行了试验,分析了裂纹产生的原因。管材的表面质量对成型后弯头的质量具有重要的影响。     

MAG焊在压力容器中的应用

本文通过对比分析,选择适当的焊接材料,并通过对试件进行探伤、金相分析、抗裂性能、拉伸、弯曲、冲击韧性等实验,在压力容器生产中创造性地引进了MAG焊焊接方法。     

Mechanisms of crack propagation in dry plaster

Controlled crack propagation tests were performed on single edge notched bend samples to investigate the crack growth behaviour of dry plaster. The influence of the relative notch depth on the crack resistance curve has been studied and appears to be very important. The results are discussed considering a qualitative model based on the specific microstructure of plaster and in situ observations of the crack propagation. Two mechanisms acting at different scales and undergoing complex interactions are involved: crack bridging by small gypsum crystals acting locally behind the crack tip and secondary cracking in a macroscopic frontal process zone. Interaction of the main crack with secondary ones undergoes substantial branching and crack accelerations leading to bridging destruction due to sudden crack opening.     

Pitting and stress corrosion cracking behavior in welded austenitic stainless steel

The effect of microstructural changes in 304 austenitic stainless steel induced by the processes of gas tungsten arc welding (GTAW) and laser-beam welding (LBW) on the pitting and stress corrosion cracking (SCC) behaviors was investigated. According to the in situ observations with scanning reference electrode technique (SRET) and the breakdown potentials of the test material with various microstructures, the GTAW process made the weld metal (WM) and heat-affected zone (HAZ) more sensitive to pitting corrosion than base metal (BM), but the LBW process improved the pitting resistance of the WM. In the initiation stage of SCC, the cracks in the BM and HAZ propagated in a transgranular mode. Then, the crack growth mechanism changed gradually into a mixed transgranular + intergranular mode. The cracks in the WM were likely to propagate along the dendritic boundaries. The crack initiation rate, crack initiation lifetime and crack propagation rate indicated that the high-to-low order of SCC resistance is almost the same as that for pitting resistance. High heat-input (and low cooling rate) was likely to induce the segregation of alloying elements and formation of Cr-depleted zones, resulting in the degradation in the corrosion resistance.     

UHDE-ICI-AMV型一段转化炉猪尾管开裂原因浅析及解决措施

性能变化、原始焊接缺陷和吊架受力不均引起局部应力集中及长期失效的综合作用,会引发一段炉猪尾管的不可预见随机性开裂。利用更换猪尾管局部管段并配合严格的焊接工艺,消除了猪尾管的开裂现象,且节约了大量资金。     

循环机压力表导管断裂原因分析

通过宏观、微观等金相组织分析方法，分析了循环机压力表导管的失效原因。结果表明，导管破裂裂纹起源于角焊缝熔合区的焊接微裂纹及粗大的魏氏组织，并在随后的试车中不断扩展而造成导管环状断裂。     

A preliminary SEM study of crack propagation in mortar

A device constructed to permit the testing of wedge-loaded compact tension specimens of mortar within the sample chamber of an SEM is described. Using this device, the process of cracking was observed in mortar specimens. It was found that the process of crack extension in mortars is very complicated: the crack is tortuous, there is some branch cracking, discontinuities in the cracks are observed, and there is some tearing away of small bits of material in some areas of cracking. The results suggest that the simple fracture mechanics models oversimplify the geometric features of the crack extension process.     

Fatigue crack retardation in polycarbonate

Results are presented from a recent study of the influence of tensile overloads on fatigue crack growth in polycarbonate. Fatigue cracks were grown under conditions of constant range in stress intensity factor in four-point bend specimens. The data presented here indicate that tensile overloads may significantly retard subsequent fatigue crack growth in polycarbonate. The period of delay in crack growth was shown to increase with the magnitude of the overload. Recovery of stable crack extension following the overload appeared to involve reinitiation of separate crack growth sites at the tip of the blunted crack tip, similar to the original crack initiation at sharp V-notches.     

不锈钢管在聚酯生产行业中的选用

采用慢应变速率拉伸试验、扫描电镜断口分析以及金相显微组织分析检测等方法对0Cr13Al铁素体不锈钢及2205双相不锈钢在酸性介质中应力腐蚀开裂行为进行了研究。并评定不锈钢管在腐蚀性介质中应力腐蚀开裂的敏感性。为在聚酯生产行业中选择容器用钢提供依据。结果表明,拉伸试样全部断裂在焊缝或热影响区。试样断口形貌呈准解理断裂和韧性断裂。2205双相不锈钢的应力腐蚀敏感性比0Cr13Al铁素体不锈钢低。     

冷高压分离器在H2S环境下应力腐蚀开裂敏感性评估

针对制造过程中由于开孔失误而进行补焊的冷高压分离器在高压、高浓度的H₂S环境的使用安全问题,采用了电化学充氢、恒应变和慢拉伸的实验方法,研究了制造冷高压分离器的主体材料16Mn(HIC)钢和普通的16Mn钢及其焊缝的氢扩散系数,在不同H₂S浓度、pH值,模拟冷高压分离器操作环境溶液和实际溶液中的腐蚀规律和硫化氢应力腐蚀开裂（SSCC）敏感性,结合实际腐蚀环境的检测和分析结果,对补焊后的冷高压分离器的使用安全给出了综合评估.     

电弧焊在窑磨修理中的应用实例

在回转窑和磨机的修理中，用焊接的方法处理开裂问题是相当普遍的。根据多年的实践，作者介绍了手工电弧焊处理铸铁滚圈、铸铁轴承座开裂问题的一些经验，包括焊接材质的选取、焊接工艺的确定以及焊接操作中应注意的问题等。