飞机舵机壳体裂纹产生原因

某飞机舵机壳体在服役过程中多次发生漏油故障，采用化学成分分析、荧光渗透检测、断口分析、金相检验等方法对漏油壳体进行检测及分析，对不同批次壳体材料进行了力学性能测试。结果表明：在脉冲油压的作用下，舵机壳体传感器孔壁萌生裂纹，并进一步扩展导致漏油；故障批次壳体材料为再结晶等轴晶组织，正常批次壳体材料为枝晶网状晶界组织，组织差异导致材料力学性能的差异，故障批次壳体材料的横向力学性能、断裂韧度以及疲劳性能等均低于正常批次壳体材料；力学性能的降低是传感器孔薄壁部位产生疲劳裂纹的主要原因。     

某型弹用尾翼片裂纹分析

目的分析弹用尾翼片淬火、回火后表面裂纹产生的原因。方法通过对存在裂纹的尾翼片进行金相检测、化学成分分析、硬度检测、断口检测、力学性能检测,对尾翼片产生的原因进行了分析和讨论。结果确定了尾翼片裂纹的性质和产生原因。结论尾翼片裂纹为淬火裂纹;尾翼片裂纹产生的主要原因是由于原材料钢板剪尾翼片条料过程中,在条料的表面产生了冷变形开裂缺陷,出现了较深的线状缺口,导致淬火热处理时产生了严重的应力集中,诱发了裂纹的萌生,同时,原材料钢板中存在的魏氏组织和硫化物夹杂等材质缺陷,也对促进了淬火裂纹的萌生。     

60Si2Mn弹簧钢力学性能不合格原因分析

采用宏观及微观断口分析、金相检验、化学成分分析等方法,对60Si2Mn圆钢材料力学性能检测不合格的原因进行了分析。结果表明:由于材料内部的氢未完全扩散出去,且材料内部存在偏析缺陷,氢原子在偏析区聚集,在材料内部产生氢致裂纹是造成力学性能不合格的主要原因。     

SUS304不锈钢三通裂纹产生原因分析

某电厂氨气输送管道上的SUS304不锈钢三通多次出现裂纹,通过宏观观察、渗透检测、化学成分分析、硬度测试、力学性能测试、金相检验等方法,分析了该三通裂纹产生的原因。结果表明:由于三通成型后没有进行规范的固溶热处理,导致显微组织中存在较多的形变马氏体和弥散分布的碳化物,增加了材料的硬度和脆性,加之三通成型内应力没有充分释放,三通在应力最大的肩部产生了裂纹。     

40 Cr 重载车轴断裂失效分析

目的研究车轴在热校直过程中的断裂原因和机制。方法通过对该车轴进行化学分析、金相检测、力学性能检测,对车轴断裂的性质和产生原因进行了分析和讨论。结果准确得出了车轴断裂的性质和产生原因。结论车轴制造工艺不合理,导致车轴轴头产生了严重的过热组织,这是车轴断裂的主要原因;原材料中较多的非金属夹杂物等材质缺陷,造成了材料的综合力学性能降低,尤其是材料的屈服强度降低,是车轴断裂产生的重要原因。建议改进车轴的制造工艺,过热严重的车轴应报废处理。     

过火后机床立柱裂纹分析

某机床立柱在运输途中发生意外火灾,灭火后发现立柱一侧的孔口处产生了一个张开型裂纹.对立柱材料的化学成分、组织结构及力学性能进行了全面检查,立柱材料为常规机床基础材料,未发现由过火造成的本质损伤.立柱裂纹产生的原因是立柱在火灾和灭火过程中的温度差导致立柱的非均匀变形,在装配约束的作用下,在危险截面处产生了过大的拉应力.     

掘进机回转架裂纹分析

通过断口宏观观察、化学成分分析、力学性能检测、金相检验以及扫描电镜分析等方法对材料为ZG35CrMnSi的掘进机回转架裂纹产生原因进行了分析。结果表明:掘进机回转架裂纹的产生主要是由于零件基体内部存在大量的疏松孔洞缺陷和沿晶分布的夹杂物,加之零件没有经过热处理,其显微组织保留着粗大的铸态组织结构,使其塑性和冲击韧度都远低于技术要求;当掘进机在使用过程中受到外力作用时,就会在应力集中严重的回转架耳轴根部过早的萌生应力裂纹并迅速扩展。     

BZ102井S13Cr110钢油管裂纹成因分析

BZ102井S13Cr110钢油管出现裂纹,通过磁粉探伤、金相分析、点蚀坑分析、化学成分分析、力学性能试验等方法对裂纹产生的原因进行了分析。结果表明:油管纵向裂纹为应力腐蚀裂纹,裂纹产生与A环空腐蚀环境、油管材料特性及油管受力条件有关。     

机车轮箍崩裂原因分析

机车轮箍在运行中发生崩裂。为确定轮箍失效原因,采用断口观察、低倍检验、力学性能检测和化学成分分析等方法对失效轮箍进行分析。结果表明,轮箍崩裂由轮缘处热裂纹引起,热裂纹的产生与其使用、路况等因素有关。     

锅炉HR3C不锈钢末级过热器管泄漏原因

某超超临界锅炉末级过热器管发生泄漏事故,通过宏观观察、化学成分分析、力学性能试验、金相检验和能谱分析等方法,对过热器管的泄漏原因进行了分析。结果表明:HR3C不锈钢末级过热器管材料中存在晶间氧化和原始内折叠缺陷,采用水浸法超声波检测未检出,运行过程中在缺陷部位产生应力集中并萌生裂纹源,裂纹在轧制过程中的交变应力作用下沿缺陷扩展最终造成管壁泄漏。     

Microstructure—Properties Correlation of Dual Phase Steels Produced by Controlled Rolling Process

The purpose of this research is to quantify the effects of compositional and processing parameters on the microstructure and properties of dual phase steel produced directly by hot rolling and rapid cooling.Steels with the base composition of 0.1%C,1.4%Si,and 1.0%Mn with additions of 0.5%Cr to influence hardenability,0.04%Nb to retard recrystallization in the latter stages of rolling,or 0.02% Ti to inhibit grain growth during and after reheating were investigated.Investigation was made to predict microstructure evolution and to correlate microstructure with processing parameters.The effects of the important microstructure parameters such as ferrite grain size,martensite volume fraction (VM) and morphology (polygonal or fibrous) on the tensile and impact properties are discussed.Multiple linear regression analysis of the ultimate tensile strength has shown that,increasing VM and martensite microhardness and grain refinement of ferrite are the major contributions to increase the strength of the steel.It was found that the dual-phase steel produced by controlled rolling process,with a microstructure which consisted of fine grained ferrite(4μm) and 35%-40% fibrous martensite,presented optimum tensile and impact properties because of enhanced resistance to crack propagation.     

Al-Zn-Mg-Cu-Sc合金中剪切带形成与演化机理研究

Al-Zn-Mg-Cu合金是超高强难变形合金,加工过程中易产生大的剪切带和裂纹等缺陷.制备了一种含钪Al-Zn-Mg-Cu合金,研究了该合金在热轧和热处理过程中宏观剪切带和轧制裂纹的形成与扩展规律.采用光学显微镜、扫描电镜、透视电镜和能谱分析对该合金热轧时产生变形局部化的力学条件和微观结构进行了深入分析.结果表明:在非均匀变形条件下,变形局部化导致局部变形区应变大和应变率高是产生剪切带和轧制裂纹的原因,与合金基体中组织和成分的不均匀性有关.在高温固溶条件下剪切带内发生了再结晶.     

Influence of the thermomechanical processing on the fracture mechanisms of high strength aluminium/pure aluminium multilayer laminate materials

The microstructure and mechanical properties, with emphasis in the impact fracture toughness behaviour, of two multilayer laminate materials have been investigated. The multilayer materials are constituted by alternated sheets of pure aluminium (Al 1200 or Al 1050) and high strength Al 7075 alloy. Stacked layers of these alloys have been successfully joined using two processing routes with different total hot rolling strains. Both laminates have been tested at room temperature under impact Charpy tests, three-point bend tests and shear tests on the interfaces. Both laminates exhibited more than eight times improvement in impact fracture toughness over the monolithic Al 7075-T6. The toughness increase in the higher rolling strained laminate is almost entirely due to crack blunting mechanism, while in the lower strained laminate, crack deflection by delamination and crack renucleation processes were active.     

Si和Nb对高强热轧高扩孔钢组织和性能的影响

为了研究Si和Nb对高强热轧高扩孔钢板显微组织、力学性能和扩孔性能的影响,在CSP连轧线上进行了3种成分试验钢的热轧试制,并对试验钢在扩孔过程中裂纹的形成和扩展行为进行了分析.研究表明:3种成分热轧钢板的显微组织均由铁素体和贝氏体组成,钢板的抗拉强度均高于610 MPa,伸长率大于24.5%,扩孔率高于104%;Si含量的增加,提高了组织中铁素体的含量,钢板的强度、伸长率和扩孔率得到提高;Nb含量的增加,细化了钢板的组织,钢板的强度和扩孔率增加明显,伸长率变化不大;试验钢在扩孔过程中裂纹主要沿铁素体和贝氏体的晶界处扩展,部分裂纹穿过铁素体晶粒.     

Q460C钢组织特性对表面裂纹成因的影响分析

通过光学显微组织观察,测定显微组织硬度和能谱分析等方法对Q460C中厚板表面裂纹成因进行了分析研究,分析了热送热装工艺对裂纹形成的影响,分析了轧制过程中裂纹的形成机理.利用热膨胀法结合金相法在Gleeble-1500热模拟实验机上测定了实验钢连续冷却转变曲线,分析了材料组织转变与裂纹形成规律的联系.分析结果表明：热送热...     

行星轧制变形程度对TP2铜管材组织及性能的影响

目的研究行星轧制变形程度对TP2铜管材在轧制和联拉时的组织和性能的影响。方法采用金相显微分析和拉伸实验,研究行星轧制变形程度对TP2铜管铸坯轧拉态以及拉拔态组织及性能的影响规律。结果经连续铸造的TP2铸坯为柱状晶,且由外向内成长。经行星轧制、联拉后的管材晶粒纤维流线,其晶粒显著拉长,随着轧制变形程度的增加,流线减弱,晶粒更加细化。轧制变形程度为93%与90%的轧管屈服强度、抗拉强度分别降低了22.83%和7.59%,伸长率提升了4.44%,塑性变形能力增加。结论随着轧制变形程度的增加,联拉管抗拉强度略有提高,而伸长率得到了保持。     

交叉轧制在Mo-1钼板生产中的应用

研究了轧制方式对Mo-1钼板组织和性能的影响,交叉轧制可使钼板的延伸率显著提高,Rp0.2和Re明显下降,加强了组织的均匀性和等轴性。交叉轧制的Mo-1钼板具有良好的深冲性能。     

Pinch Roller Failure Analysis and Resulting Enhancement of Rebar Mechanical Properties

Reinforcing bars, popularly termed “rebars,” are used to impart tensile strength to concrete structures. Concrete has high resistance to weathering and fire and high compressive strength but almost no tensile strength, hence rebars are used to provide the latter to concrete. Property consistency along the length of rebars is an important prerequisite. When the finished product is subjected to thermomechanical treatment (TMT), proper control of rolling and water box parameters and efficient pinch rolling are needed to achieve acceptable properties. Variation of yield strength (YS) along TMT bars from the front to back end has been observed within the same heat treatment. In the presented investigation, it was observed that pinch rolling ineffectiveness is the main reason for the poor mechanical properties at the back end. The pinch roller was unable to support the back end of the TMT bars properly to maintain the speed and tension of the bars, resulting in nonuniform cooling of the back end through the water box and subsequent mechanical property failure. Due to the substandard material of the pinch roller, it was unable to hold the back end of the bar properly. Based on analysis of the roller it was concluded that it failed due to improper microstructure, resulting in inadequate hardness and toughness for the stringent operating conditions. AISI H13 is a better material to use in such high-service-temperature conditions. Moreover, proper heat treatment is needed to achieve adequate hardness and microstructure properties. After proper heat treatment of pinch rollers, their service life was increased twofold, minimizing the YS variation along the rebars.     

引线框架铜合金精轧薄板表面起皮剥落的数值分析

运用弹塑性有限元方法的平面应变分析模型，依据引线框架Cu-Fe-P合金精轧后表面起皮剥落处的显微组织特征，研究了Cu基体和Fe相颗粒界面附近的应力应变场分布。研究表明：铜基体与铁相的塑性行为及应力应变分布具有明显的不均匀性．界面区强烈的应力集中易造成界面开裂；精轧前Fe相周围的微裂纹在精轧变形时将进一步发展，直至发生引线框架扳材表面起皮剥落破坏。应避免热轧板坯中出现较大Fe颗粒。