Innovative Stainless Steel Applications in transport ... - Euro Inox

Apart from the materials included in the table, some experiments were also carried out
for materials 304SP 2B and 1.4318 in C850 and C1000 temper-rolled conditions
(DOLTRAC p. 99). However, because the material thickness (1.0 and 1.2 mm) and
joining methods (arc and laser brazing) were different from the BUS project data, these
results have not been included here but in a separate table.
According to the results in Table 27, practically full base-material strength can be
obtained with MAG welding for all the base materials in 2B condition. This applies to
both yield strength and tensile strength values. However, it is rather surprising that the
dominant failure mode is still in the weld metal, the only exception being the ferritic
1.4003, which shows base-material failure.
The cold rolled higher-strength grades fall behind the increased base-material strength
levels. The 304 sp and 16-7 Mn still retain approximately 80 % of both base-material
yield strength and tensile strength but the drop is more remarkable for 1.4301: only 40 -
50 % of the base-material level is reached. However, it should be noted that the degree
of strengthening due to cold forming is much higher for 1.4301, compared to other
alloys. This can be seen particularly in yield strength, where cold forming has increased
the base-material strength by a factor of four, whereas for other alloys the strength is
increased by factors of between 2 and 2.5. The difference in tensile strength is also
marked: 304SP and 16-7 Mn show a strength gain of 30 - 50 % while with 1.4301
tensile strength has almost doubled. Again, the most common failure location is the
weld metal or the weld-HAZ interface. Another important feature is that elongation is
lost almost completely in the cold-rolled material welds. Some drop (though much less
dramatic) can also be seen in the 2B-material results.
The powder plasma arc welding experiments showed similar behaviour: for the 2B
materials, strength values at or very close to the base-material tensile strengths were
reached, but differences in yield strengths were greater. Only tensile strengths were
determined in these tests, so the yield strengths cannot be compared to the MAG-welded
results.
Laser welding is commonly regarded as one possible way to avoid the excessive drop in
strength values that results from the softening of cold-rolled material. This is because
the small heat input, compared to that of arc welding, results in a much narrower
softened region (i.e. weld metal and HAZ). The effect is most pronounced in 304SP and
1.4003 welds. With 1.4301, the effect is less.
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