Residual stresses of polycrystalline CBN abrasive grits brazed with a high-frequency induction heating technique

Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using ?nite element analysis, with a consideration of the nonuniform temperature distribution in the induction brazing model. The in?uences of induction brazing parameters on the residual stresses of polycrystalline CBN abrasive grits have been analyzed, including the embedding depth, grit side length, etc. Results obtained show that the tensile stress with a 40% embedding depth is 292 MPa, which is the minimum on the bonding interface compared with other embedding depths. Meanwhile, the maximum tensile stress is 575 MPa, with an increase of 59% compared with that of a grit side length of 50 mm. Finally, the simulation results of the brazing residual stress of polycrystalline CBN abrasive grits have been con?rmed valid based on the residual stress measurement of the brazed monocrystalline CBN grit.

Compressive Strength and Interface Microstructure of PCBN Grains Brazed with High-Frequency Induction Heating Method

In order to prepare monolayer brazed superabrasive wheels, the polycrystalline cubic boron nitride（PCBN）grains were brazed to AISI 1045 steel matrix with Ag–Cu–Ti filler alloy using the high-frequency induction heating technique. The compressive strengths of brazed grains were measured. Morphology, chemical composition and phase component of the brazing resultant around PCBN grain were also characterized. The results show that the maximum compressive strength of brazed grains is obtained in the case of brazing temperature of 965 °C, which does not decrease the original grain strength. Strong joining between Ag–Cu–Ti alloy and PCBN grains is dependent on the brazing resultants,such as TiB_2, TiN and AlTi_3, the formation mechanism of which is also discussed. Under the given experimental conditions, the optimum heating parameters were determined to be current magnitude of 24 A and scanning speed of0.5 mm/s. Finally, the brazing-induced residual tensile stress, which has a great influence on the grain fracture behavior in grinding, was determined through finite element analysis.

钯含量对银铜钯合金箔带钎料性能的影响

钎焊是一种常用的金属连接方法,然而钎焊过程中产生的一些不良现象,如氧化膜、气孔等,影响了合金钎焊料的质量和可靠性。本论文旨在探讨钯对银铜钯箔带合金钎焊清洁性的影响,并寻找提高其清洁性的方法。通过实验研究和分析,发现添加钯银铜钯合金钎料能够有效减少氧化膜的生成,并提高钎焊接头的力学性能和界面的稳定性。钯银铜合金箔带的钎焊接头在气孔方面也呈现出明显的改善。此外,钯的添加还能够改善钎焊接头的焊接质量,为箔带材合金钎料的广泛应用提供了有力支持。

感应钎涂粉末熔融及传热机制

感应钎涂技术是材料表面修型提性的重要技术手段,分别选用碳钢和陶瓷作为基板进行感应钎涂试验,系统研究了粉状和膏状钎涂层温度变化规律,分析了钎涂过程热量传递方式和路径.结果表明,感应钎涂时涂层材料不能被直接感应加热,钎涂层升温的热源几乎全部来自于钢基体的热传导,液固界面剧烈传热并梯次推进,促进了金属钎料的熔融铺展;当基材由导电且能够被感应加热的碳钢替换为陶瓷时,涂层材料升温只能依靠自身生热.粉状钎涂料呈游离态,粉末颗粒之间及粉末颗粒与金刚石之间充满气体,基体的热量难以传导至上部,粉末难以充分熔融,而添加粘结剂的膏状钎涂料在感应过程中能快速熔化,粘结剂兼有导热、助熔和保护等多重作用.

铜与不锈钢高频感应钎焊工艺及组织分析

针对电解铜阴极板导电杆钢包铜结构难以连接的问题,采用高频感应钎焊焊机,以Sn Cu0.7锡焊丝作为钎料进行了阴极板导电杆铜-钢异种金属的高频感应钎焊工艺研究。试验中采用Raytek FR1B红外测温系统实现对高频感应钎焊工艺温度的实时监测与控制,重点分析了高频感应钎焊工艺对导电杆钢包铜结构的质量及性能的影响,并观察分析了钎焊接头的微观组织和接头区域的成分。研究表明,以Sn Cu0.7锡焊丝作为钎料可以实现阴极板导电杆钢包铜结构的高频感应钎焊连接;获得的最佳工艺参数范围能够获得内外部质量、连接强度优良的接头;研究结果对进一步研究导电杆的导电性能及大批量生产阴极板导电杆具有重要意义。

Al-Si-Cu-Ge钎料性能的研究

通过熔炼方法制备了一系列不同Ge含量的低熔点的Al-Si-Cu-Ge钎料。利用示差扫描量热仪(DSC)对钎料的熔化区间及显微组织进行分析和判定;研究上述钎料的铺展性能并通过感应钎焊方法实现2A12的焊接;通过接头抗剪强度评价钎料的力学性能。结果表明,加入Cu、Ge能够显著降低钎料熔点;能够与Al形成化合物,从而降低表面张力,极大地改善钎料的润湿性能;但随着Ge含量的增加,由于焊缝中脆性相的增加,导致焊后接头抗剪强度下降。

BNi52MnCoNbSiFeB合金钎料粉末的制备与性能研究

采用真空感应熔炼结合气雾化的方式制备BNi52MnCoNbSiFeB合金钎料粉末,分析了不同粒径粉末的微观形貌与组织,表征了该合金钎料粉末的成分和熔化温度。结果表明,通过精确控制熔炼和雾化工艺,可以得到分散性较好、球形度高、成分可控和熔化温度范围小的BNi52MnCoNbSiFeB合金钎料粉末。

PdNiCrBSi合金钎料粉末的制备及钎焊应用研究

针对航空航天钎焊用钎料合金粉末的需求,采用真空感应熔炼气雾化法制备PdNiCrBSi合金钎料粉末,研究了该粉末的物理性质、微观形貌与结构以及在高温合金基材上的钎焊性能。结果表明:PdNiCrBSi粉末主要为球形,由多种物相组成,且在GH3536母材上具有良好的润湿铺展性和可钎焊性。该钎料焊后的焊缝最大拉力38.2~38.9 kN,钎焊接头剪切强度为382~389 MPa,基本与母材强度相近,其断裂方式为脆性断裂。