Abstract: At present, the empirical formulas are used in the design of carbon steel electrode coating. In the tensile strength carbon equivalent (Ct) or lower yield strength carbon equivalent (Cy) of formulas, there are carbon equivalents of C, Mn, Si, Ca, Cr, etc., but no any exact carbon equivalent of rare earth elements, thus being unsuitable for design of the ingredients of low carbon steel electrode containing rare earth. So a proper amount of lanthanum (La) and yttrium (Y) is transferred through the electrode coating in developing an ingredient for the new type electrode. By means of mechanical property test of deposited metals of five representative ingredients, the quantified formulas and 3-D net chart of the tensile strength and lower yield strength are obtained by Matlab function aided calculation and curve fitting. Tensile strength and lower yield strength of deposited metal with rare earth multicomponent can be known in advance. The results show that the conversion can’t be realized between the carbon equivalent and rare earth elements by the empirical formulas. Consequently, the problem of the big errors can be solved by the quantified formula. Especially, it can clearly reveal the quantitative relationship between the addition of La and Y and the mechanical properties.

Key words: Design, Lanthanum, Tensile strength, Welding electrodes, Yttrium