©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
V
5.11.0.3
Normally the most severe dilution of
the weld metal by the base metal is 40%. Thus, the
weld metal in the joint is comprised of 60% from the electrode and 40% from the
base metal as
shown in Figure 14. In the case of butt joints between dissimilar steels,
half of the dilution
comes from each side of the joint, or 20% from each base metal.
5.11.0.4 Many
times, type 310 and 312 electrodes are used erroneously for welding stain-
less to mild or low alloy steel. In
many cases, not only can more dependable welds be made with
309 electrodes, but appreciable savings can be achieved because of their lower
cost. 308 ELECTRODE
ELECTRODE X 60%
304 X 20% MILD
WELD STEEL
X 20% METAL
CHROMIUM 19.5
11.7 18.0
3.6 0
0 15.3
NICKEL 9.5
5.7 8.0
1.6 0
0 7.3
The composition of 15.3% chromium and
7.3% nickel does not meet the minimum 17-7% proportion.
The weld metal will be mostly martensitic with a very small amount of ferrite.
This structure is quite brittle.
310 ELECTRODE
ELECTRODE X 60%
304 X 20% MILD
WELD STEEL
X 20% METAL
CHROMIUM 26.0
15.6 18.0
3.6 0
0 19.2
NICKEL 21.0
12.6 8.0
1.6 0
0 14.2
The composition of 19.2% chromium and
14.2% nickel is not near the 18/8 proportion. The
weld metal would be fully austenitic and crack sensitive.
309 ELECTRODE
ELECTRODE X 60%
304 X 20% MILD
WELD STEEL
X 20% METAL
CHROMIUM 23.0
13.8 18.0
3.6 0
0 17.4
NICKEL 13.0
7.8 8.0
1.6 0
0 9.4
The composition of 17.4% chromium
and 9.4% nickel is close to the 18/8 proportion. The
weld metal will be austenitic with
some ferrite and a small amount of martensite to keep the
weld metal from being tough and crack resistant. 309 is the best choice.
60% 20%
304 MILD
STEEL 20%
ELECTRODE SELECTION - 304 STAINLESS
TO MILD STEEL FIGURE
14 ELECTRODE
