FB3-F银钎剂去膜机理

Film Removal Mechanism of FB3-F Silver Brazing Flux

研究了由H_(3)BO_(3)、K_(2)B_(4)O_(7)和KF(质量比为7:10:3)3种组分配制而成的银钎剂的去膜机理。结果表明:在700℃时,K_(2)B_(4)O_(7)或KF都不能单独去除Q235钢板表面的氧化膜,且KF会加快高温下钢表面的氧化速率;H_(3)BO_(3)能够去除Q235钢表面的氧化膜,然而其反应产物具有明显的非晶结构特征,并且流动性差。此外在700℃时,H_(3)BO_(3)与KF能够发生反应,其反应产物可以去除钢表面氧化膜。KF和K_(2)B_(4)O_(7)之间也能在700℃发生类似的反应,然而其反应产物非常坚硬。因此,在700℃时,H_(3)BO_(3)、K_(2)B_(4)O_(7)和KF混合钎剂能够与Q235钢板表面氧化膜反应,且反应产物具有明显的非晶特征。KF的加入将非反应性H_(3)BO_(3)-K_(2)B_(4)O_(7)二元体系转化为反应性KF-H_(3)BO_(3)-K_(2)B_(4)O_(7)三元体系。在这个三元体系中,KF不但对钢板没有腐蚀性,反而促进了氧化膜的去除。

The film removal mechanism of FB3-F silver brazing flux consisting of H_(3)BO_(3),K_(2)B_(4)O_(7),and KF with the mass ratio of 7:10:3 was studied.Results show that K_(2)B_(4)O_(7) or KF cannot individually remove the oxide film on Q235 steel at 700℃,and KF even accelerates the oxidation rate of steel surface at high temperature.H_(3)BO_(3) can remove the oxide film at 700℃,but the product possesses an obvious amorphous structure feature and poor fluidity.Furthermore,H_(3)BO_(3) can react with KF at 700℃,and the reaction product can remove the oxide film.Similarly,K_(2)B_(4)O_(7) can react with KF,but the product is hard.The mixture solder consisting of H_(3)BO_(3),K_(2)B_(4)O_(7),and KF can react with the oxide film on surface of Q235 steel plate,and the reaction product presents obvious amorphous feature.The addition of KF transforms the nonreactive H_(3)BO_(3)-K_(2)B_(4)O_(7) binary system into the reactive KF-H_(3)BO_(3)-K_(2)B_(4)O_(7) ternary system at 700℃.KF shows no corrosivity and promotes the removal of oxide film of steel plates in this ternary system.