焊接参数对硬质合金/钢异质金属高频钎焊接头组织与性能的影响

Effect of welding parameters on the microstructure and properties of cemented carbide/dissimilar steel high-frequency brazed joint

采用CuZn钎料对硬质合金/钢异种金属进行了高频钎焊,并对高频焊接工艺主要参数(加热时间、加热电流、保温电流和保温时间等)对接头显微组织与性能的影响进行了详细研究。研究结果表明:加热时间和保温电流主要影响焊接过程中的最高温度,加热电流和保温时间主要影响加热过程和保温过程的时间进而影响元素的扩散程度。在其他参数不变条件下,随加热时间和保温电流的增加或随加热电流的减小、保温时间的减少,接头由纯钎焊状态向钎焊、熔焊混合状态转变。接头纯钎焊区域由单一的Cu(s,s)组成,因此,显微硬度稳定在250 HV左右。而熔化区域由于Fe(s,s)的出现,显微硬度显著增加,且随着Fe(s,s)的含量增加,显微硬度数值持续增加。随着加热时间、加热电流、保温电流和保温时间的增加,接头剪切强度均呈先上升后下降的趋势,在加热时间为30 s,加热电流为850 A,保温电流为740 A和保温时间为40 s时接头强度达到最大值288.44 MPa,且接头均断裂在硬质合金侧界面处,主要原因在于脆性η相的生成导致了该区域的脆化。

High frequency brazing of cemented carbide/dissimilar steel is carried out with CuZn as the brazing material,and the influence of the main parameters of high-frequency welding process(heating time,heating current,holding current,and holding time)on the microstructure and properties of the joint is studied in detail.The results show that the heating time and holding current mainly affect the maximum temperature in the welding process,while the heating current and holding time basically affect the duration of heating and holding processes,consequently influencing element diffusion.With the increase of heating time and holding current or the decrease of heating current and holding time,the joint changes from the pure brazing state to a mixed state of brazing and fusion welding when other parameters remain the same.The pure brazed area of the joint consists of a single Cu(s,s),so the microhardness stably rests at around 250 HV.However,the microhardness of the melting zone increases significantly due to the appearance of Fe(s,s),and the microhardness value continues to increase with the increase of the content of Fe(s,s).Following the increase of heating time,heating current,holding current and holding time,the shear strength of the joint increases first and then decreases.When the heating time reaches 30 s,the heating current is 850 A,the holding current is 740 A,and while the holding time is 40 s,the joint strength reaches the maximum value of 288.44 MPa,and all the joints break at the interface of cemented carbide side,mainly because the formation of brittleηphase leads to embrittlement in this region.