金刚石锯片焊接部位的组织结构与力学性能

Microstructure and mechanical properties of welding zones of diamond saw blade

采集金刚石圆锯片激光焊和高频钎焊部位作试样,分析研究了钢基体与粉末烧结刀头过渡层对焊焊缝横向的区段划分、焊缝形貌、金相组织、成分与物相、硬度及抗弯强度,并阐述了激光焊气孔的成因。结果表明:激光焊熔化区柱晶组织排布细腻,有残留气孔,硬度呈线性变化;钎焊熔化区为两相组织,枝晶明显,无裂纹气孔,硬度较低。激光焊钢热影响区产生针状马氏体;钎焊不存在相变引起的热影响区。激光焊和钎焊的刀头过渡层,在特定的配料体系下,也不存在固态相变引发的热影响区,基本保持了粉末烧结组织。激光焊和钎焊焊缝的抗弯强度均值分别为1 175 MPa、983 MPa,都大于国外安全强度要求,但激光焊焊缝强度波动相对较大,这与其残留气孔密切相关。

The transverse section division of welding seam,morphology,microstructure,composition and phase,hardness and bending strength of laser welding and brazing were analyzed,the samples were from buttwelded steel matrix and powders sintering segments of diamond saw blade. The cause of the laser welding pores was also stated. Results show that the fine-arrangement column grain and residual pores exist in the laser welding melting zone with the hardness varies linearly;while bi-phase structure,obvious dendritic structure and no cracks and pores exist in the brazing melting zone with low hardness. Acicular martensite appears in the laser welding heat- affected zone（HAZ） of steel side,while in the brazing,there is no HAZ caused by phase transition in the steel side. With specific proportioning system,there is also no HAZ caused by solid phase transition in the cutter head transition layer of laser welding and brazing segments,which remains powder sintering microstructure. The bending strength of laser welding and brazing seam are 1 175 MPa and 983 MPa,respectively,both higher than the overseas security strength requirements. The bending strength of laser welding has relatively large fluctuations,which is closely related to residual pores.