20#无缝管冷弯断裂原因分析

20#无缝钢管按工艺要求进行冷弯成型时发生断裂.对其断口、材料的化学成分、力学性能和显微组织进行分析.结果表明,冷弯制断裂属于终轧温度偏低所致.针对冷弯制断裂情况提出一些预防改进措施.     

WK-10电铲斗杆开裂后的修复

针对白云鄂博铁矿使用的WK-10电铲斗杆断裂后难以修复的情况,根据材质特性及以往现场处理经历,通过对断裂的斗杆进行局部更换的方法,恢复其使用功能.     

管线钢冲击性能的实验研究

采用系列温度仪器化冲击实验的方法,对在特殊环境下使用的管线钢冲击断裂各阶段的能量变化情况及冲击断口的SEM形貌进行了研究.结果表明,该试验钢的抗塑性变形能力、抗裂扩展能力均随温度降低而降低.通过对各个实验温度下的特征值进行比较分析,掌据了材料微观断裂过程的变化情况,为采取相应措施,提高该钢种的低温冲击性能提供了依据.     

650轧机机前工作辊道辊颈的故障分析

就影响生产中工作辊道辊颈的断裂问题,从理论计算公式和实际生产状况进行了全面、详细地分析和计算.在理论上就设计手册中的计算公式与采利柯夫公式进行比较,阐述了两种公式的不同之处,就现场情况进行了验算,找出了用设计手册中计算公式验算工作辊道辊颈受力情况的不尽合理的地方.将走访几个厂家现场情况,逐一作了分析,找出了生产中工作辊道辊颈的断裂问题的几个主要因素,并提出预防措施.     

立辊轧机四列圆锥滚子轴承保持架有限元分析

针对某轧板厂立辊轧机辊颈四列圆锥滚子轴承保持架断裂事故,建立了轴承系统有限元模型;在轴承元件间重要接触位置采用接触单元建立了面-面接触对.仿真得到了保持架的变形和应力分布情况,找出了轴承保持架断裂的原因,并对今后此类轴承的设计提出了改进建议.     

某型飞机发动机卡箍失效分析

某型飞机在使用过程中发动机卡箍发生断裂,厂内普查也发现此类现象.针对此情况,对失效卡箍开展了外形观察、断口宏观观察、化学成分分析、金相组织检查和晶间腐蚀倾向性验证等手段.结果发现卡箍在生产过程中存在焊接现象,焊接热影响区存在晶间腐蚀倾向性,致使卡箍在使用过程中产生沿晶裂纹最后导致断裂.     

梁体断裂原因分析及处理措施

分析了南京钢铁股份有限公司梁体断裂的原因,并根据现场情况,采用结构胶植筋锚固的方法,对平台进行了修复,满足了生产要求.     

预应力混凝土钢丝张拉断裂分析

针对高碳钢盘条加工的预应力混凝土钢丝在轨枕模型中张拉断裂问题,对张拉断裂、拉拔断裂及盘条试样进行检验分析,并结合工艺参数控制情况,分析断裂产生的原因,提出改进的措施。经生产应用,后续生产盘条加工的钢丝未出现张拉断裂现象。     

PQF连轧机轧辊断裂的形成原因分析

文章分析了PQF连轧机前三架轧辊表面过早老化磨损及轧辊断裂的原因。根据现场实际情况,以轧制运行状态、轧辊表面老化磨损的情况、轧辊断裂的形态为依据,制定了PQF连轧机微张力轧制法,减少轧辊老化及断裂,提高轧辊寿命。     

钨骨架/Zr基非晶合金材料的静态力学行为

利用渗流铸造法制备出直径为8 mm、钨颗粒体积分数达40％的钨骨架/Zr基非晶合金复合材料,在室温下通过电子万能试验机对材料进行静态压缩实验.通过扫描电子显微镜(SEM)技术对复合材料的原始组织和断裂特征、裂纹扩展等情况进行研究.结果表明:材料在静态加载条件下屈服强度不具有应变率效应,其值基本保持不变;材料塑性良好,具有应变强化效应.复合材料断裂模式为一种混合断裂模式,在变形带间交界处发现若干裂纹.非晶基体阻碍钨骨架中裂纹的扩展,钨骨架防止复合材料发生大范围的流变.     

应力比对J55钢级疲劳裂纹断口形貌的影响

借助疲劳试验机及SEM,研究了应力比对J55钢级疲劳裂纹扩展性能的影响,并对断口形貌进行分析。结果表明:随着应力比增大,进入快速裂纹扩展区的ΔK变小;对于应力比0.1,低Paris区断裂模式为沿晶体学平面发生的穿晶断裂,Paris线性部分为由双滑移机制控制的疲劳条带断裂,高Paris区为疲劳条带断裂和延性静态断裂相结合的断裂模式;应力比为0.3、0.5与应力比为0.1的断裂模式相似;对于应力比0.7,沿晶体学平面发生穿晶断裂模式贯穿整个Paris区。     

Interpretation of the Effects of High Austenitizing Temperature on Toughness Behavior in a Low Alloy,High Strength Steel

An experimental investigation into the effects of high temperature austenitizing treatment (h.t.a.) on the microstructure and the mechanical properties, and micromechanisms of fracture in a variety of test conditions has been carried out on a Ni-Cr high strength steel. H.t.a. increased the fracture toughness, but decreased the tensile ductilities and notch toughness of this steel with a slight reduction in strength in the condition of strain-controlled fracture mode. However, the fracture toughness and notch toughness of steel were simultaneously improved by h.t.a. in the condition of stress-controlled fracture mode. This behavior of ductility and notch toughness is because the micro structural variations arising from h.t.a. have different roles in different fracture modes. It appears that the general effect of microstructural changes is beneficial to stress-controlled fracture, but the reverse is true to straincontrolled fracture. The fracture toughness behavior was greatly affected by the change in characteristic distance with austenitizing temperature, but the characteristic distance obtained from the best fitting of experimental results does not have clear physical meaning. It is observed that the application of macroscopic fracture stress or strain in analyzing local failure behavior ahead of the crack tip can be justified if the characteristic distance is consistent with the microstructural parameters related to the fracture process. The improvement in fracture toughness for stress controlled fracture mainly results from the large characteristic distance; whereas in the case of strain controlled fracture, this is caused by the much higher local fracture strain ahead of the crack tip of h.t.a. structure compared to that observed in structures produced by conventional austenitizing.     

低合金钢焊接热影响区的静载断裂特性

 低应力破坏是焊接结构常见的断裂形式之一,为确定其影响因素,采用插销法焊接试验和扫描电镜断口观察,研究了低合金钢焊接热影响区的静载断裂特性。试验结果表明,为防止焊接热影响区产生低应力断裂,采用预热措施是十分有效的;预热80℃以上时,断裂强度与母材强度相接近。断口观察表明,不预热时绝大部分为结晶状断口,微观上呈现氢致沿晶断裂和氢致准解理断裂;预热时绝大部分是纤维状断口,微观上呈韧窝状。     

Cu-5%Cr合金拉拔断丝原因检测分析

针对Cu-5%Cr复合材料在拉拔过程中常出现的断丝现象,用扫描电镜对拉拔断丝样品进行宏观和微观断口形貌观察及分析.结果表明,断口形貌为杯锥断口,属典型的微孔聚集型断裂.在拉拔过程中,丝材中存在的大量细小弥散的第二相Cr颗粒与Cu基体变形不协调,是微孔产生和裂纹扩展的主要原因.试验发现去除退火后丝材表面氧化皮、保证良好的润滑效果、采用合适的拉拔变形量可以有效的避免断丝现象的发生.     

断裂韧性与断裂表面分形维数的相关性研究

建立了材料断裂韧性与断裂表面分形维数的相关关系模型。结果表明，断裂韧性是分形维数、材料屈服强度、微结构尺寸及夹杂物体积分数等多参数的函数，并非只取决于分形维数。     

Stress Corrosion of X80 Pipeline Steel Welded Joints by Slow Strain Test in NACE H2S Solutions

The X80 pipeline steel was welded with the way of submerged arc welding. The SST (slow strain test) of the welded joint samples in the air, NACE (National Association of Corrosion Engineers) solution (no H2S), NACE solution (saturated H2S) was performed to research the sensibility index of SCC (stress corrosion cracking) Iscc. The morphologies of the welded joint fractures and the fracture modes were observed with SEM (scanning electron microscope), and the fracture chemical compositions were analyzed with EDS (energy dispersive spectrometer), respectively. The fracture mechanisms of the welded joints were discussed. The results show that sensibility index of SCC in the air is not obvious, the fracture is dimple, and the mode of fracture is ductile fracture. The sensibility index of SCC in NACE solution (no H2S) is 13.21%, the stress corrosion is not obvious. The sample fracture shows quasi cleavage+dimple, and the fracture mode is toughness+brittle rupture. The sensibility index of SCC in NACE solution (saturated H2S) is 56.94%, the plastic loss is the most serious, appearing an obvious stress corrosion tendency, and there is no obvious necking phenomenon. The fracture mode is brittle fracture, and the sample fracture has a high sulfur concentration, prompting S to a aliquation of crisp crystal in the welded zone, and making its mechanical properties worsen.     

Fracture behavior in medium-carbon martensitic Si- and Ni-steels

A study of fracture behavior in medium-carbon martensitic Ni- and Si-steels has been made. Charpy impact testing was conducted in order to investigate fracture mode as a function of test temperature. Whereas the transgranular cleavage fracture becomes the primary brittle fracture mode with decreasing test temperature in the Si-steel, intergranular fracture is the only brittle fracture mode observed at low temperatures in the Ni-steel. The different fracture behavior between these steels appears to be due to variation in intrinsic matrix toughness. Since Si may impair the intrinsic matrix toughness, the occurrence of transgranular cleavage fracture becomes relatively easy with decreasing test temperature. On the other hand, since Ni may improve considerably the intrinsic matrix toughness, the transgranular cleavage fracture is not able to occur although the test temperature decreases. Thus, the intrinsic matrix toughness can play a significant role in controlling the fracture behavior.     

Effect of quenching temperature on microstructure and fracture toughness of high carbon steel

The effect of quenching temperatures on microstructure and fracture toughness of high carbon steel was investigated. Plane strain fracture toughness was tested with compact tension specimen. Microstructure and fracture morphology of KIC samples after quenching and tempering treatment were examined by scanning electron microscope (SEM).The results show that the residual carbides of steel in hardened state decreasea with the quenching temperature increasing and totally disappear after quenched at 920??;the grain size grows up obviously when the quenching temperature is more than 960??. The microstructure in high temperature tempered state is composed of residual carbides, precipitated carbides and ferrite matrix;plasticity decreases monotonically; the fracture toughness gradually decreases in the range from 800?? to 960??,and then almost invariant; the fracture type of KIC specimens is gradually changed from cleavage fracture to intergranular fracture. The main reason for the changes of fracture toughness has close relationship with the plasticity.     

浅谈铝型材室温断后伸长率的检测

从试样加工形状尺寸,取样方向,拉伸速率,以及人工测量与机器测量等方面,对公司生产的铝挤压型材断后伸长率进行测试分析。得出结论,圆形试样的断后伸长率比矩形试样的断后伸长率略大;平行长度越大,断后伸长率越大;横向取样的断后伸长率明显小于纵向取样的断后伸长率;人工测量比机器测量更可靠,更接近真实的断后伸长率。     

X70管线钢DWTT试样的分层裂纹及其断口评价

通过对管线钢不同温度的落锤撕裂试验和微观断口分析,研究了DWTT试样断口的分层裂纹及其对断裂的影响.结果表明,分层裂纹是受力变形时管线钢内部的薄弱界面受到三维应力作用的结果.分层裂纹出现于主裂纹起裂或加速之前,裂纹稳定扩展或减速时不会产生新的分层裂纹.分层裂纹的数量、张开程度和分层裂纹间距与主裂纹起裂或加速时的应力状态有关,而分层裂纹的长度与裂纹扩展时裂尖的应力状态有关.分层裂纹表面为解理形貌,解理面较大.韧脆转变温度以下的脆性断裂断口或韧脆转变温度附近混合型断口的脆性断裂区,不出现分层裂纹,仅在韧性断口或断口的韧性区出现宏观分层裂纹.研究表明,产生分层裂纹处的断口,分层裂纹无论是三角形分布或是其它形状分布,该区域均应评价为韧性.