Abstract
This report presents the structural variations such as width of recrystallized zone and recrystallized grain size of heat-affected-zone of commercially pure aluminum welds and their influences on the tensile strength. Test pannels were made by MIG welding process using 6 mm thick plate whose mechanical properties had been controlled by H1n or H2n-tempering.
Softening behavior at heat-affected-zone is occurred in accordance with ordinary recrystallization sequence, but the extraordinary grain growth are not observed. The width of recrystallized zone is increased with increase of cold rolling reduction (for H1n series) and drop of pre-annealing temperature (for H2n series) of base metal, while its grain size becomes finner reversely.
Softening curve obtained by hardness distribution at heat-affected-zone and peak temperature in weld heat cycle depends on only tempering conditions of base metals. The recrystallizing temperature shown in this curve is recognized to decrease with increase of cold rolling reduction or drop of pre-annealing temperature of base metal.
The tensile strength of heat-affected-zone is under the severe influence of tempering conditions of base metal, that is, it is increased with increase of cold rolling reduction or drop of pre-annealing temperature. This fact seems to result from mainly the variation of grain size at heat affected zone mentioned above.
So long as the base metals possess similar strength in spite of difference in tempering conditions of them, there is observed little difference in the strength of heat-affected-zone. However, width and grain size of recrystallized zone are fairly influenced by tempering conditions.
