基体对高锰钢辙叉爆炸硬化效果的影响

为了研究基体对高锰钢辙叉爆炸硬化效果的影响,使用厚度3mm、密度1.38g/cm3的板状炸药分别在50mm厚钢板上、空气中及沙土上对高锰钢辙叉试件进行爆炸硬化。试验结果表明,在钢板上、空气中和沙土上对高锰钢进行爆炸硬化后,高锰钢辙叉试件的硬度分别提高了85.1%、76.6%和82.6%。与在钢板上和空气中相比,在沙土上对高锰钢辙叉试件进行爆炸硬化既能保证硬化后辙叉试件的硬度≥350HB,又能保证辙叉试件的整体不发生严重的变形。     

基体对高锰钢辙叉爆炸硬化效果的影响

为了研究基体对高锰钢辙叉爆炸硬化效果的影响,使用厚度3mm、密度1.38g/cm3的板状炸药分别在50mm厚钢板上、空气中及沙土上对高锰钢辙叉试件进行爆炸硬化。试验结果表明,在钢板上、空气中和沙土上对高锰钢进行爆炸硬化后,高锰钢辙叉试件的硬度分别提高了85.1%、76.6%和82.6%。与在钢板上和空气中相比,在沙土上对高锰钢辙叉试件进行爆炸硬化既能保证硬化后辙叉试件的硬度≥350HB,又能保证辙叉试件的整体不发生严重的变形。     

钢轨铝热焊接头韧性研究

本文对钢轨铝热焊焊接接头各部位的韧性进行了试验研究。试骏确定接头低韧性区为焊缝和近缝区,该部位的冲击韧性值约为49.035KJ/m~2左右。作者在分析其薄弱原因的基础上对改善焊接接头的韧性的途径进行探讨,并指出小试样试验中采用900℃保温20分钟空冷热处理,可使接头各部位的冲击值均达到98.070KJ/m~2以上,热处理过程中影响焊缝金属韧性的主要因素为化学成份均匀化,而影响热影响区韧性的主要因素为晶粒大小。     

高密度脉冲电流对服役后期高锰钢辙叉组织结构的影响

用高密度脉冲电流对服役后期的高锰钢辙叉进行表面处理,研究了对其组织结构的影响。结果表明,在较低的温度下（786 K）辙叉发生再结晶,再结晶晶粒尺寸约为29.3μm,远比处理前的晶粒尺寸小,处理后的显微硬度显著降低。在高密度脉冲电流作用下,位错运动能力、原子的扩散能力以及振动频率都提高了,从而使再结晶的形核速率显著提高,...     

钢轨闪光焊接后轨腰原始裂纹的特征

在U75V钢轨的端部轨腰处采用线切割和高频疲劳预制轨腰裂纹,并进行闪光焊接,在放置7a（天）后对焊接接头试样的裂纹表面形貌和脱碳现象进行了分析和研究。研究表明,预制轨腰裂纹与其他轨腰焊接水平裂纹的宏观和微观区别,为今后焊接接头处的轨腰水平裂纹质量检验和判断提供了依据。     

我国铁路无缝线路焊接技术分析研究

铁路钢轨无缝焊接是铺设无缝线路的重要环节,是线路行车安全的重要保证。分析我国铁路无缝线路焊接技术的发展现状,着重介绍铁路无缝线路焊接方法及其工艺流程,以此作为无缝线路焊接技术的参考。     

起重机钢轨窄间隙焊接工艺探讨

天钢高速线材工程原料跨起重设备为17．5＋17．5t电磁桥式起重机,其大车运行轨道为QU80钢轨,按照图纸要求轨道接头采用焊接接长。本文工程实际论述了起重机钢轨窄间隙焊接工艺的可实施性,并通过了实践的验证,对今后类似工程安装工作具有一定的借鉴意义。     

金刚石薄膜与基材之间过渡层技术的研究

通过ＴＥＭ观察发现在金刚石膜与单晶硅片，金刚石膜与ＡｌＮ陶瓷之间存在一层过渡层，过渡层的存在为金刚石的形核及生长提供了有利的条件，受此启发，为了改善金刚民基材的结合强度，采用磁控溅射，空心离子镀，真空蒸镀等方法在Ｍｏ片上沉积ＴｉＣ，ＴｉＣＮ（Ｃ／Ｎ＝１／２）ＴｉＣＮ（Ｃ／Ｎ＝１／１０）等薄膜，研究了它们对金刚石膜与基材的结合强度的影响。     

含过渡层氧化铝膜的制备

用ＣＶＤ法在铝表面同时沉积氧化铝和铜，在热扩散的作用下铜铝形成合金，使氧化铝和铝之间存在连续过渡层。这种氧化铝膜在厚度１００μｍ时仍和铝材有良好的结合强度。     

无缝线路钢轨铝热焊接接头质量控制

焊接接头质量控制方法为通过控制焊接碳含量,进而确保接头整体稳定,但由于缺乏对接头的热处理,因此导致质量控制效果较差。为此,该文提出无缝线路钢轨铝热焊接接头质量控制方法。根据钢轨型号进行焊接接头热处理,并计算焊接线能量以及焊道碳当量,最后对钢轨预拱度进行调整。试验结果表明,采用该文提出的方法对焊接接头质量进行控制,接头的耐腐蚀性较高,具备较好的质量控制效果。     

Hybridization of filler wire in multi-pass gas metal arc welding of SA516 Gr70 carbon steel

In the present investigation, multi-pass gas metal arc welding (GMAW) of SA516 Gr70 carbon steel was carried out by different filler wires such as solid, metal cored and flux cored, wherein, other process parameters were kept constant. The hybrid approach of multi-pass filler wires was applied to obtain three different welds. The root pass was filled by a solid wire for all three cases while the subsequent filler pass was applied through solid, flux-cored and metal cored filler wires, respectively. Metallographic, mechanical and metallurgical analyses such as macrograph study, optical microscopy, tensile testing and hardness variations were performed to address the quality of weld. The results revealed that defect-free sound welds were produced by the hybrid approach of different filler wires in multi-pass GMAW. Overall cost and time reduction can be achieved through hybrid filler welds, without affecting their mechanical strength. Angular distortion was reported minimum at hybrid weld of solid and metal cored filler wire. Maximum reinforcement with higher penetration was observed at weld of solid and metal cored filler wire. Impact toughness was reported higher in case of hybrid weld of solid and flux cored filler wire. Higher macro hardness was reported at weld of solid and flux cored filler wire.     

Contact stress and residual stress in the nose rail of a high manganese steel crossing due to wheel contact loading

Fatigue failure of a high manganese steel crossing is related to its internal crack initiation and growth, which is affected significantly by the magnitude and distribution pattern of contact stress and residual stress in the crossing. Considering the actual service conditions of a crossing and the accuracy requirement for numerical calculation, a whole model of wheel/crossing/ties and a partial model of wheel/crossing are established using elastic‐plastic finite element method. The distributions of contact stress fields and residual stress fields due to wheel contact loading are studied. The effect of train speed on the residual stress in the nose rail is discussed. The contact stress field shows regular contours in the cross‐section of nose rail and decreases remarkably with increasing distance of the wheel‐crossing contact position. The maximum contact stress is located at the contact surface between wheel and crossing. The maximum residual stress is located at a position of 1.5‐2.0 mm below the surface of the nose rail, rather than at the contact surface of wheel and crossing. In a failed high manganese steel crossing, the dense cracks mainly were observed neither at the position of maximum contact stress (the contact surface between the wheel and the crossing), nor at the position of maximum residual stress (1.5‐2.0 mm below the surface of the nose rail), but around the depth of 0.8‐1.0 mm from the worn surface, which is between the position of maximum contact stress and the position of maximum residual stress. It indicates that the combined effects of the maximum contact stress and the maximum residual stress play important roles in fatigue crack initiation in the nose rail. The size of high residual stress region increases with the increase of the train speed. The maximum residual stress in the nose rail increases remarkably with the increase of the train speed.     

Zr-Cu-Ni非晶钎料真空钎焊TiAl合金/316L不锈钢接头的界面组织与剪切性能

采用自主设计制备的Zr-42.9Cu-21.4Ni非晶钎料对TiAl合金和316L不锈钢进行真空钎焊,研究钎焊温度和钎焊时间对TiAl合金/316L不锈钢异种金属接头微观组织和剪切性能的影响。结果表明：钎缝界面可以划分为6个不同的反应层。1040 ℃/10 min下制备的钎焊接头从TiAl合金到316L不锈钢侧界面组织依次为γ(TiAl)+AlCuTi/α₂(Ti₃Al)+AlCuTi/AlCu+ZrCuNi+FeZr/Cu₈Zr₃+ZrCuNi+TiFe+Fe₂Zr/FeZr+Fe₂Zr+TiFe₂+ZrCu/α-(Fe, Cr)。随着钎焊温度的升高,接头的抗剪强度先升高后降低。当钎焊温度为1040 ℃和钎焊时间25 min时,接头抗剪强度达到最大值162 MPa。断口分析表明,接头在FeZr+Fe₂Zr+TiFe₂+ZrCu界面处萌生,沿着Cu₈Zr₃+ZrCuNi+TiFe+Fe₂Zr和α-(Fe, Cr)扩展,呈解理断裂。     

钛基非晶钎料真空钎焊TA15钛合金的研究

针对TA15薄壁及蜂窝等复杂结构件设计和焊装的需求,本文采用急冷技术成功制备Ti-Zr28-Cu15-Ni15(1#),Ti-Zr21-Cu20-Ni15(2#)非晶箔带钎料.通过SEM,EDS和XRD等分析测试手段,分析了钎料及钎焊工艺对TA15钛合金钎焊接头界面组织和力学性能的影响.研究结果表明:两种钛基非晶钎料成带性能良好,与相同成分晶态钎料相比,液相线温度降低,熔化温度区间减小.钎料对母材有明显润湿作用,并且2#钎料共晶成分的提高使得其润湿性和非晶形成能力较1#钎料优异.1#钎料对接接头室温拉伸强度在970℃/30min工艺下达到最高325MPa,2#钎料在950℃/30min工艺下接头强度达到最高359MPa,并且其接头力学性能的稳定性较1#钎料要高.对比相同工艺下不同钎料焊缝组织,钎缝均为α+β层片状组织,2#钎料界面处Ti-Cu和Ti-Ni金属间化合物含量较少.     

Microstructure and XRD analysis of brazing joint for duplex stainless steel using a Ni–Si–B filler metal

Brazing of a nitrogen-containing duplex stainless steel was preformed using a nickel-based filler metal (Ni-4.5wt.%, Si-3.2wt.%, B). The microstructure of the brazed joint was investigated using scanning electron microscopy, energy dispersive spectrometry, electron probe microanalyzer, and layer-by-layer X-ray diffraction analysis. The results indicated that before completion of isothermal solidification, BN, Ni₃B and Ni₃Si precipitates formed at the interface, in the athermally solidified zone and isothermally solidified zone, respectively. After isothermal solidification, only γ-Ni phase appeared in the brazed interlayer. The appearance of hardness peak values in the athermally solidified zone and the interface most probably corresponded to the formation of Ni₃B and BN, respectively.     

Fatigue crack initiation in hardened medium carbon steel due to manganese sulphide inclusion clusters

Forged steel generally suffers from strong fatigue anisotropy. This anisotropy is more pronounced in standard sulphur (SS) steels (typically 0.04 wt percent) with a dense manganese sulphide (MnS) population as compared with low sulphur (LS) steels (down to 0.004 wt percent or less). Anisotropy due to MnS arises because of the flattened shape which sulphides obtain upon a forging operation. The higher grade of anisotropy in SS materials is attributed to the occurrence of sulphide clusters that are exclusive to these materials. It is shown that the prediction of fatigue limit with respect to conventionally recorded inclusion size is highly non-conservative when it concerns cluster-affected material, but only when the clusters are oriented perpendicular to the loading axis. Fatigue failures occurred at stresses much lower than expected. An interaction of the single sulphide within one cluster and an interaction of the clusters within the test volume are believed to cause the inferior fatigue performance.     

A novel high manganese austenitic steel with higher work hardening capacity and much lower impact deformation than Hadfield manganese steel

To tackle the problem of poor work hardening capacity and high initial deformation under low load in Hadfield manganese steel, the deformation behavior and microstructures under tensile and impact were investigated in a new high manganese austenitic steel Fe18Mn5Si0.35C (wt.%). The results show that this new steel has higher work hardening capacity at low and high strains than Hadfield manganese steel. Its impact deformation is much lower than that of Hadfield manganese steel. The easy occurrence and rapid increase of the amount of stress-induced ε martensitic transformation account for this unique properties in Fe18Mn5Si0.35C steel. The results indirectly confirm that the formation of distorted deformation twin leads to the anomalous work hardening in Hadfield manganese steel.     

Cu-P-Sn-Ni钎料真空钎焊MGH956合金的研究

为扩展Cu-P基钎料在连接MGH956合金中的应用,采用新型Cu-P-Sn-Ni钎料对MGH956合金在800~890℃进行了真空钎焊,研究了不同钎焊温度和保温时间对焊缝组织及力学性能的影响.结果表明:在所研究的钎焊温度范围内保温5 min均可获得成形效果良好的钎焊接头,其主要由钎缝中心区和界面反应层组成,其中,钎缝中心区由α(Cu)固溶体基体和化合物Cu_3P+(Fe,Ni)_3P+FeCr组成,反应层由α(Fe)固溶体、Fe_3P和Cu_3P组成;随着钎焊温度的升高,反应层厚度逐渐增加,钎缝中心区中的化合物Cu_3P+(Fe,Ni)_3P+FeCr的形态也随之发生明显改变;各钎焊温度下获得的钎焊接头经室温拉伸,断裂均发生在钎缝中心区,断口形貌呈现韧性和脆性的混合断裂特征.830℃钎焊5 min的接头抗拉强度最大,为510.3 MPa,达到了母材抗拉强度的70.9%.     

变形制度对低碳锰钢组织性能的影响

为了获得细晶铁素体/贝氏体的复相组织,通过控轧控冷工艺研究了低碳锰钢在奥氏体区变形时变形量、终轧温度和卷取温度对组织演变和力学性能的影响规律.研究表明,增加变形量(对应道次间隔时间缩短)可以细化铁素体晶粒,但当终轧温度降低到800℃时,变形量的增加以及开冷温度的降低不利于贝氏体组织的获得.通过调整变形量、终轧温度、可开冷温度并适当降低卷取温度,可使实验钢获得晶粒尺寸约为5μm的铁素体和10%~20%的贝氏体组织,低碳锰钢强塑性能良好.     

变质高锰钢析出相的演变及力学性能的研究

为了有效改善高锰钢的组织和性能,通过变质处理和弥散处理相结合的方法,采用X射线衍射(XRD)、光学显微镜、扫描电镜(SEM)及透射电镜(TEM),对稀土-低熔点合金变质高锰钢时效析出相进行研究.结果表明:实验用钢在460℃时效1 h时,基体上开始有球状析出相析出,随着时效时间的延长,析出相由球状向针状转变;520℃时效1 h,晶界上有少量的球状析出相,基体上析出相为细针状;580℃时效1 h,析出相为粗大的针状,且基体发生了奥氏体向珠光体转变.随着时效温度的升高,变质高锰钢时效析出相由球状转变为针状,针状析出相与球状析出相晶体结构不同,针状析出相更加趋于稳定.变质高锰钢的硬度随着析出相增多而升高,(Mn,Fe)7C3细针状析出相在冲击韧性和耐磨性起主导因素,变质高锰钢最佳时效工艺应使耐磨析出相析出,且未引起微观应变增大.本次实验用钢最佳时效工艺参数为520℃下时效1 h.