2001 Volume 19 Issue 3 Pages 513-520
Stress-strain characteristics of S15C carbon steel friction welded butt joints under impact tensile loading are evaluated using the split Hopkinson bar. Round tensile specimens machined from as-welded butt joints of 13 mm diameter are used in both static and impact tension tests. Friction welding is carried out using a brake type friction welding machine under fixed welding conditions. The effect of strain rate up to ε≅700/s on the tensile stress-strain characteristics of both friction welded butt joints and a base material (S15C carbon steel) is studied. It is shown that the flow stress for friction welded butt joints is always higher than that for the base material at low and high rates of strain, but the former are less sensitive to strain rate than the latter. Microhardness measurements are conducted to examine the extent of the heat-affected zone (HAZ) across the weld interface. Metallographic examination reveals that there are zones of different grain structure through the weld region. The increase in the flow stress for friction welded butt joints is attributed to the presence of a locally-hardened region within the HAZ.