| In this study, we have attempted the solid-phase welding of superplastic ultra-high carbon steel that has a carbon content of 1.4 wt.% (UHCS-1.4C) with 40Cr steel. The UHCS-1.4C was preprocessed into ultrafine grain and fully spheroidized microstructure through a controlled rolling and divorced eutectoid transformation. And the 40Cr steel was also preprocessed into fine grain through salt-bath cyclic quenching. The welding was performed at 1053 - 1093K, under compression strain rate rage of 10-3 - 10-1 s-1 and compression strain rage of 0.1 - 0.2. The ultimate tensile strength of the welded specimen increases with increasing welding time and with decreasing compression rate, and becomes approximately the same as that of 40Cr steel for a welding time above 600 s and a compression strain rate of 10-3 s-1. The carbon content of 40Cr increases, while that of UHCS-1.4C decreases in the region near the interface. Considering from these result, the carbon in UHCS-1.4C diffuses into 40Cr. The fracture surface of the joints consists of sags and crests, which reveal a metallurgy bonding. The results indicate that UHCS-1.4C can be suitably used for solid-phase welding with 40Cr steel in a short-duration. |
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