CARBON EQUIVALENT AND MULTIPLYING FACTOR FOR HARDENABILITY OF STEEL

The carbon equivalent and the multiplying factor are indexes for hardenability of steels. The carbon equivalent is used generally in welding and is related to the critical cooling time for the full martensite structure in the HAZ. The multiplying factor is used in heat treatment of hardenable steels and is related to the critical diameter for the full martensite. A heat conduction in a round bar has clarified that the ideal critical diameter should be expressed in a product form of alloy elements as long as the carbon equivalent is expressed in a linear combination of elements. Coefficients of the elements in the carbon equivalent have been calculated from their multiplying factors reported in the literature in light of the result of a heat conduction analysis. The coefficients of Mn, Cr, Mo and Cu are in fairly good agreement with the experimental results, while the coefficients of Si and Ni are in poor agreement.