仿SIMA法钎焊对Mn-Cu合金与430不锈钢接头组织及性能的影响

Effect of SIMA-imitated Brazing on the Microstructure and Shear Strength of Mn-Cu/430 Stainless Steel Joints

采用Cu-Mn-Ni-Sn钎料对Mn-Cu合金与430不锈钢分别进行普通钎焊(铸态钎料,850℃)和仿SIMA法钎焊(轧制态钎料,半固态温度790℃),研究钎焊温度对接头微观组织、化合物的形成数量以及剪切强度的影响。结果表明:普通钎焊接头中,不锈钢与钎缝的界面处形成(Mn,Fe,Cr)固溶体扩散层,但扩散层与钎缝界面位置形成裂纹。富Sn相沿Mn-Cu合金的晶界渗透促进了合金的熔化,钎缝与Mn-Cu合金之间形成联生结晶。不锈钢向钎料中的过度溶解以及Mn-Cu合金的局部熔化导致钎缝中形成大量针状Mn-Cr-Cu-Fe化合物。仿SIMA法钎焊接头中,不锈钢与钎缝的界面结合良好。在半固态温度下,钎料向不锈钢侧的扩散量减小,同时不锈钢向钎料溶解的程度也较小。在Mn-Cu合金侧,富Sn相沿晶界的渗透得到了有效抑制,钎缝与Mn-Cu合金之间可观察到明显的界面。由于钎料与母材之间的相互作用减弱,钎缝中针状化合物的数量明显减少。剪切试验中,两种钎焊接头均断裂于钎缝中的针状化合物分布区域。普通钎焊接头的剪切强度为173 MPa,仿SIMA法钎焊接头的剪切强度有所提高,为230 MPa。

In this paper,Cu-Mn-Ni-Sn brazing filler metal was used to braze Mn-Cu alloy and 430 stainless steel(SS)by ordinary brazing(as-cast brazing filler metal,850℃)and SIMA-imitated brazing process(rolled brazing filler metal,semi-solid temperature 790℃),respectively.The effects of brazing temperature on the microstructures,the formation of compounds and the mechanical properties of the joints were studied.In ordinary brazed joint,(Mn,Fe,Cr)solid solution diffusion layer was formed at the interface between stainless steel and brazing seam,however,cracks were formed at the interface between the diffusion layer and the brazing seam.The penetration of Sn-rich phase at grain boundaries of Mn-Cu alloy promoted the melting of alloy.The excessive dissolution of SS and partial melting of Mn-Cu alloy resulted in the formation of a large number of needle-like Mn-Cr-Cu-Fe compounds in the brazing seam.In SIMA-imitated brazed joint,the interface between stainless steel and brazing seam was well bonded.At the semi-solid temperature,the diffusion of filler metal to SS was decreased,and the dissolution of SS to filler metal was decreased as well.At the Mn-Cu alloy side,the penetration of Sn-rich phase along the grain boundaries was also effectively suppressed.Since the interaction between the substrates and filler metal was weaker,the amount of needle-like compounds decreased obviously in the brazing seam.In shear test,both brazed joints were broken in the distribution area of needle-like compounds in the brazing seam.The shear strength of ordinary brazed joint was 173 MPa,and that of SIMA-imitated brazed joint was 230 MPa.