The brazed joints are generally weak to impact loads; this results in the low reliability to the mechanical properties of the joints. Therefore, methods to increase the impact strength of carbon steel braze joints by utilizing dissolution and deposit of base metal was studied. The results were as follows:
(1) Charpy U-notch (GUN) impact strength of the low carbon steel (0.17%C)/high carbon steel (1.04%C) joint brazed with Cu filler metal is increased remarkably from 2.9 J/cm2 to 27.2 J/cm2 at room temperature, when both base metals are linked with the deposited columnar Fe-9 to 12%Cu-1 to 2%C alloy.
(2) When using Deposit-Filler metal (which consists of high carbon steel foil plated with Cu of 10μm thickness on both sides) for similar low carbon steel joint, CUN impact strength of the joint is advanced 89.4 J/cm2 because of linking both base metals with the columnar phase through the foil.
(3) Due to carburizing-effective case depth of 0.2 mm-one of base metals prior to Cu brazing for similar low carbon steel joint, CUN impact strength of the joint is attained 89.2 J/cm2 by linking, since the columnar phase deposits from the carburized low carbon steel.
