Representation system of cleanness of filler metal

The high quality of filler metals are required by the equipment manufacturing industry to obtain the highperformance brazed joint.For the problems of impurities in filler metal,the concept of entropy has been carried out to describe the cleanness of filler metal.The math expressions of process entropy,S_p,and performance entropy,S,,have been presented.S_p characterizes the manufacturability of filler metal,corresponding to the spreading coefficient and the viscosity.S_t characterizes the mechanical property of the brazed joint,corresponding to the tensile strength and the shear strength.With the increase of entropy value,the cleanness as well as the brazability of filler metal and the mechanical property of joint deteriorate.The physical verification indicates that the expressions of S_p and S_t could characterize the cleanness of filler metal.