Calculation of Carbon Equivalents for Mechanical Properties of Basic Weld Deposits (Report 3)
Correlation between Chemical Composition and Crack Sensitives of Weld Metals
1967 Volume 36 Issue 10 Pages 1110-1116
Details
1967 Volume 36 Issue 10 Pages 1110-1116
Weld crack is one of the most difficult problems encountered in welding processes of high strength steels. It is classified into heat affected zone crack and weld metal crack. This report clarified the correlation of chemical composition, hardness and structure of weld metals to weld metal cracks.
The basic electrodes were prepared so that the main effects of C, Si, Mn, Ni, Cr, Mo and the interactions between C and the other elements for the weld metal cracks could be analyzed using orthogonal array table L16(215). Weld metal cracking tests were carried out with U groove cracking test specimens.
From the results of the weld metal cracking tests, the carbon equivalent equations for the crack sensi-tivities of weld metals were calculated and the correlation between the values of the carbon equivalent equations and weld cracks was obtained.
The conclusions are as follows:
1. The carbon equivalent equations for the crack sensitivities of weld metals are expressed by the following equations.
Surface cracking percentage: +0×Cr ..................0.03%≤Cr≤0.53%
Ceq(f)=C+0.14Si+0.10Mn+0.04Ni+0.11Mo+0.27(Cr-0.53) .........0.54%≤Cr≤1.49%
Section cracking percentage: +0×Cr ................0.03%≤Cr≤0.53%
Ceq(s)=C+0.15Si+0.11Mn+0.05Ni+0.12Mo+0.24(Cr-0.53) .........0.54%≤Cr≤1.49%
Root cracking percentage: +0×Cr ................0.03%≤Cr≤0.53%
Ceq(r)=C+0.15Si+0.12Mn+0.05Ni+0.13Mo+0.26(Cr-0.53) ........0.54%≤Cr≤1.49%
0.10%≤C50.18%, 0.12%≤Si≤0.53%, 0.70%≤Mn51.38%
0.03%≤Ni≤1.17%, 0.01%≤Mo≤0.49%, 0.03%≤Cr≤1.49%
2. It was confirmed after testing more than ten basic electrodes including commercial high tensile strength electrodes that the tendency of crack sensitivities of basic weld metals conld be well represented by the carbon equivalent equations as above mentioned.
3. In order to prevent the initiation of weld metal cracks, the upper limit of weld metal hardness must 270Hv. The chemical composition and cooling rate must also be selected so that ferrite may precipitate in the structure of weld metals.
