Patent ID: 8028889

Claim:
A process for welding first and second steel elements together, the first element being formed from a low carbon steel and the second element containing, at a surface thereon, a high carbon steel, said process comprising: placing the two elements together, with the first element being against the surface of high carbon steel on the second element; heating the elements in a localized area where they are together to effect a bond between the steels of the two elements in that area, the heating further transforming the nearby high carbon steel in the second element into a heat affected zone (HAZ) in which the high carbon steel is austenitic; allowing the steel in the HAZ to cool yet remain austenitic and above the martensite start temperature; while the steel in the HAZ remains austenitic, subjecting the localized area to further heating that elevates the temperature of the HAZ to less than the eutectoid temperature and to further cooling such that some of the steel in the HAZ transforms from austenite to bainite; and thereafter allowing the steel in the HAZ to cool below the martensite start temperature for the steel in the HAZ, whereby the steel in the HAZ includes bainite in addition to martensite, with the bainite being at least 10% by volume fraction.