影响硬质合金耐磨焊条质量的因素及分析

1 前言 本文采用高硬度的WC硬质合金颗粒与Cu-Zn-Ni钎料复合,形成棒状的硬质合金复合耐磨堆焊焊条。研究加热工艺参数对焊条成形质量、组织和性能的影响,探索提高硬质合金耐磨堆焊焊条质量的途径。 2 试验材料和研究方法 试验用硬质合金及粘结金属的主要化学成分和性能分别见表1,硬质合金的颗粒大小约6-8mm,用Cu-Zn-Ni钎料按图1所示的成形工艺在电炉中将硬质合金颗粒粘结成棒状气焊条。     

TiC硬质合金颗粒堆焊材料的组织和耐磨性

研究了TiC硬质合金颗粒堆炼材料的组织、硬度和耐磨性,并分析了磨料的硬度和粒度对堆焊材料耐磨性的影响。实验结果表明,在柘榴石磨料磨损时,TiC 堆焊材料的耐磨性是WC 堆焊材料的3倍多。     

含WC颗粒高锰钢堆焊层的组织及耐磨性能

自制了不同含量及粒径的WC高锰钢焊条,采用火焰堆焊获得了高锰钢堆焊层,运用金相分析、X射线衍射分析、磨损试验等方法研究了WC颗粒含量和粒径对堆焊层组织及耐磨性能的影响。结果表明:堆焊层中WC颗粒与基体界面结合良好,组织为奥氏体枝晶和莱氏体共晶碳化物;随着WC含量的增加,组织由奥氏体等轴晶转变为枝晶,枝晶间合金碳化物及共晶组织随之增多;小粒径颗粒对堆焊层组织的影响略于大粒径颗粒的;WC颗粒显著提高了高锰钢堆焊层的耐磨性能。     

火焰喷焊和等离子堆焊制备Ni60及Ni60-WC涂层的组织与性能

采用火焰喷焊与等离子堆焊工艺分别制备了Ni60与Ni60-WC涂层,对比研究了两种涂层的显微组织、物相组成、硬度和耐磨性能。结果表明:Ni60与Ni60-WC喷焊层比相应堆焊层的内部缺陷多、孔隙率高;喷焊层硬度曲线波动大,堆焊层硬度分布均匀;喷焊层磨损表面粗糙,划痕较多,而堆焊层磨损表面平滑;WC颗粒的添加提高了喷焊层与堆焊层的硬度和耐磨性;火焰喷焊工艺下,WC颗粒的添加使得涂层孔隙率增大,WC颗粒发生一定的脱碳,而等离子堆焊工艺下WC颗粒的添加对涂层孔隙率影响不大,WC颗粒能较完整地保存在涂层内。     

硬质合金抗弯强度及其分散性的研究

用三点弯曲法测定了硬质合金的抗弯强度σm,用两参数Weibull统计法分析了σm 的分散性。试验和分析结果表明 :硬质合金的抗弯强度与材料中WC的粒度和粒度均匀性有关 ,σm 的平均值随材料中WC颗粒平均尺寸d的增大而减小 ,随WC粒度均匀性变好而增大。     

热处理态钢结硬质合金WC相析出微结构分析

利用SEM研究了热处理后钢结硬质合金TLMW50复式碳化物中WC相的析出及其微结构.结果表明:经过1100℃淬火后烧结态钢结硬质合金TLMW50中主要复式碳化物Fe3W3C、Fe2W2C相发生析出分解.三角状、菱形状WC相颗粒随机分布在Fe3W3C、Fe2W2C相颗粒上.淬火二次析出WC相颗粒有利于提高烧结态钢结硬质合...     

硬质合金YG30/45钢TIG焊连接的研究

选用Ni-Fe合金和纯Ni焊丝对硬质合金YG30与45钢进行了TIG焊连接试验。采用Ni-Fe合金焊丝4层对焊时，焊接接头硬质合金YG30热影响区中有η相形成。当采用纯Ni焊丝4层对焊、堆焊及Ni-Fe合金焊丝堆焊时，硬质合金YG30热影响区中均没有η相形成。扫描电镜结合成分分析得出，这些η相主要是由于在焊接过程中C向焊缝金属中扩散，而Fe、Ni向WC中扩散形成的。有η相存在的硬质合金YG30／焊缝界面区域硬度急剧变化，没有η相存在的硬质合金YG30／焊缝界面区域硬度变化平缓。     

不同WC粒径的硬质合金的高温耐磨性研究

利用粉末冶金方法制作不同碳化钨粉（Wolfram Carbide,WC）粒径的硬质合金,有利于工作人员分析不同WC粒径的硬质合金材料性能,并进行高温摩擦实验。结果表明,随着WC粒径的增加,平均晶粒尺寸会受到不同程度的影响,且很容易引起WC晶粒出现各种情况,可以有效扩展晶粒的分布范围。硬质合金硬度随着WC粒径的增加产生下降,当WC粒径为2.5μm时,硬质合金具有较强的综合力学性能。在室内温度为350℃摩擦条件下,WC粒径为2.5μm的硬质合金磨损度最低。但是,在700℃条件下时,2.5μm粒径的硬质合金和1μm粒径硬质合金磨损率基本相同,而3.5μm粒径的硬质合金磨损度是其他粒径的2.5倍左右。     

硬质合金复合堆焊焊条的研制

本文研究了用硬质合金生产过程中的返回料粉末和用废硬质合金机械破碎粉末制造硬质合金复合堆焊焊条的工艺。研究结果指出,这种焊条制造工艺简单,堆焊性能优于管状焊条,解决了管状焊条长期末解决的堆焊层气孔高的问题。     

纳米WC-Co硬质合金研究现状

综述纳米硬质合金的研究开发概况及应用。重点介绍纳米WC和WC-Co粉体的制备方法和烧结工艺,指出要成功地制备纳米硬质合金,关键在于抑制烧结过程中WC晶粒的长大。简要介绍纳米硬质合金的应用前景。     

一种窄间隙GMA焊缝深度的自动跟踪与控制方法

在窄间隙GMA中，采用协调控制的方式，在形成背面焊缝的同时，得到稳定的第一层焊缝深度。焊缝自动跟踪系统由DSP芯片完成，并由个人电脑控制。焊枪不仅要横向摆动，而且还要沿焊缝方向前后移动。焊枪首先向前移动形成背面焊缝，然后重叠向后移动形成第一层焊缝，因此，可获得单面焊双面成型。     

Autonomous seam acquisition and tracking system for multi-pass welding based on vision sensor

Automatic welding technology is a solution to increase welding productivity and improve welding quality, especially in thick plate welding. In order to obtain high-quality multi-pass welds, it is necessary to maintain a stable welding bead in each pass. In the multi-pass welding, it is difficult to obtain a stable weld bead by using a traditional teaching and playback arc welding robot. To overcome these traditional limitations, an automatic welding tracking system of arc welding robot is proposed for multi-pass welding. The developed system includes an image acquisition module, an image processing module, a tracking control unit, and their software interfaces. The vision sensor, which includes a CCD camera, is mounted on the welding torch. In order to minimize the inevitable misalignment between the center line of welding seam and the welding torch for each welding pass, a robust algorithm of welding image processing is proposed, which was proved to be suitable for the root pass, filling passes, and the cap passes. In order to accurately track the welding seam, a Fuzzy-P controller is designed to control the arc welding robot to adjust the torch. The Microsoft Visual C++6.0 software is used to develop the application programs and user interface. The welding experiments are carried out to verify the validity of the multi-pass welding tracking system.     

Study on the burning loss of magnesium in fiber laser welding of an Al-Mg alloy by optical emission spectroscopy

In order to study the burning loss of magnesium, a specially designed device was used to capture the spectrum emitted from the keyhole plasma in deep penetration laser welding of aluminum alloy 5052. The content of magnesium in the weld bead was measured by an electron probe micro-analyzer (EPMA). The effect of the welding parameters on the spectral intensity of magnesium plasma was examined, and the distributions of the spectral intensity of magnesium plasma in the radial and depth directions of the keyhole were investigated. Finally, the mechanism of the magnesium loss was analyzed. The results indicate that burning loss of magnesium can be monitored by spectral analysis technique. The welding parameters have a great effect on the burning loss of magnesium. The influence of welding speed on the burning loss of magnesium on the top surface is dependent on the penetration regime. The distribution of magnesium in the weld is not uniform. In the radial direction of the weld bead, the content of magnesium increases from the center to the edge of the keyhole. In the depth direction of the weld bead, the content of magnesium decreases firstly and then increases from the top to bottom. The maximum burning loss of magnesium occurs at the middle of the weld bead.     

A control system for uniform bead in fillet arc welding on tack welds

Positioning a workpiece accurately and preventing weld distortion, tack welding is often adopted before main welding in the construction of welded structures. However, this tack weld deteriorates the final weld bead profile, so that the grinding process is usually performed for a uniform weld bead profile. In this study, a control system for uniform weld bead is proposed for the fillet arc welding on tack welds. The system consists of GMA welding machine, torch manipulator, laser vision sensor for measuring the tack weld size and the database for optimal welding conditions. Experiments have been performed for constructing the database and for evaluating the control capability of the system. It has been shown that the system has the capability to smooth the bead at the high level of quality.     

A novel iso-scallop tool-path generation for efficient five-axis machining of free-form surfaces

Weld cladding is a process of depositing a thick layer of a corrosion resistance material over carbon steel plate to improve the corrosion resistance properties. The main problem faced in stainless steel cladding is the selection of process parameters for achieving the required clad bead geometry and its shape relationships. This paper highlights an experimental study carried out to develop mathematical models to predict clad bead geometry and its shape relationships of austenitic stainless steel claddings deposited by gas metal arc welding process. The experiments were conducted based on four-factor, five-level central composite rotatable design with full replication technique. The mathematical models were developed using multiple regression method. The developed models have been checked for their adequacy and significance. The direct and interaction effects of process parameters on clad bead geometry and its shape relationships are presented in graphical form.     

Metal bead crystals for easy heating by direct current

The preparation of metal bead crystals with two wires attached to the crystal is described. These crystals allow for a very easy and efficient method to heat metal single crystals by direct current heating through the connecting wires of the bead crystal. This heating of the bead crystal is sufficient to clean metal surfaces such as the surfaces of Pt and Au as confirmed by Auger spectroscopy and scanning tunneling microscopy (STM). There is no need for any ion sputtering which is conventionally used to clean metal single crystal surfaces. The bead crystals with two leads fabricated from a wide range metals and metal alloys such as Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, PtRh, AuAg, and PtIr can be used as general purpose metal substrates for surface science studies and other applications. Additionally, these bead crystals can be used to reshape STM tips by indentation of the tip into the soft metal in order to recover atomic resolution imaging on hard substrates.     

Microstructure and hardness of Al-Mg-Si weldments produced by pulse GTA welding

This paper describes the effects of pulsed TIG welding process parameters (pulse duration, peak current, and pulse frequency) on the microstructure and microhardness of Al-0.8%Mg-0.5%Si (6061) alloys. It was observed that pulse TIG welding produced finer grain structure of weld metal than conventional TIG welding (without arc pulsation). An increase in the pulse frequency has been found to refine the aluminium and eutectic grain structure of weld metal especially when welding is done using short pulse duration. Long pulse duration lowers the pulse frequency up to which refinement of constituents in weld metal takes place. Effect of the pulse frequency on the grain structure was found to be determined by pulse duration. For a given pulse frequency, long pulse duration produced a coarser structure than short pulse duration. An increase in the peak current coarsened the grain structure.     

钛材上火焰喷焊Ni-WC耐磨涂层的组织和性能

研究了在钛合金Ti-6Al-4V表面上采用火焰喷焊技术制备镍基碳化钨型自熔性合金涂层的可行性，利用SEM、XRD等手段分析了它的组织和性能。结果表明：采用火焰喷焊技术在钛合金表面上获得了功能梯度涂层，Ni-WC涂层为韧基体＋硬质相的耐磨组织，涂层和过渡层之间形成了韧性镍基合金层，在涂层、过渡层和基体之间形成了牢固的冶金结合，涂层的组织和显微硬度沿层深方向呈连续性和渐变性，喷焊表层中WC起到了主要的抗磨作用，涂层磨损失重仅为未喷焊钛合金的1／10。     

厚板窄间隙埋弧焊焊缝阶梯形断口形成机理研究

为提高2.25Cr-1Mo-0.25V耐热钢埋弧焊接头的韧性,采用冲击试验和三点弯曲试验找到接头韧性的薄弱环节,并通过进一步的微观分析,试图揭示接头韧性的弱化机理。冲击试验显示,焊缝的韧性低于母材和热影响区,因此利用三点弯曲试验,对裂纹在焊缝中的扩展过程进行更深入的研究。在三点弯曲试验时观察到焊缝中出现阶梯形断口。通过扫描电镜观察到断口表面呈现出韧窝和准解理共存的混合形貌。金相观察发现,阶梯形断口出现在焊缝的柱晶区,其方向与柱晶生长方向平行或垂直。利用苦味酸腐蚀试样,观察到阶梯形断口与结晶方向平行的部分是沿原奥氏体晶界开裂,电子背散射衍射(Electron backscattered diffraction, EBSD)试验结果也证明了这一点,而垂直于结晶方向的部分是沿层状线开裂。因此,原奥氏体晶界和层状线是焊缝中需要特别关注的部位。通过调整焊丝成分和工艺参数,减少了焊缝中的层状线,焊缝韧性明显提高。     

铝合金双面双弧同步立焊工艺特征与接头组织性能分析

采用双面双弧同步立焊工艺方法,对8 mm厚5083铝合金进行自熔试验,I形坡口一次熔透,焊缝成形美观。通过调节两侧电弧热量配比研究熔池成形规律,并从焊接接头的微观组织、力学性能分析其连接机理。研究结果表明,随着热输入的增加,双面双弧同步立焊热量加速集聚,熔深以三次幂函数的速度增大。双面双弧同步立焊接头轮廓呈“双曲线形”,而相同热输入下的单面焊接头则呈“倒马鞍形”。总热输入一定的情况下,双面双弧接头正面熔宽随能量配比系数的增大而增大,反面熔宽随能量配比系数的增大而减小,中间熔宽基本不变,熔化面积随能量配比系数的增大先增大后减小;能量配比系数一定时,随着焊速的增大,接头熔宽和熔化面积均减小。母材组织为条带状纤维织构,热影响区发生静态回复与再结晶,变形组织消失,产生新晶粒,焊缝区主要由α-Al固溶体、β相(Al8Mg5)质点和骨骼状的Mg2Si析出相组成。焊缝的抗拉强度随着能量配比系数的增大而减小,拉伸断裂形式为韧性断裂。热影响区出现软化现象,双弧交汇区硬度低于正面焊缝区。