Abstract: The present invention provides a method for heat-treating seam-welded constructions of hardenable steel and ferrous alloys with reduced weld-zone hardness and improved weld-zone ductility and toughness. This method consists of heating the seam weld rapidly with a secondary heat source to a temperature greater than the martensitic start temperature but not greater than the lower critical temperature, followed by immediately allowing the seam weld to air-cool. The rapid tempering of this invention is particularly suited to the production of high strength hardenable alloy seam-welded pipe and tubing and other structures.

Abstract: A method for making gas and liquid storage tanks such as automotive fuel tanks includes providing two or more blanks of air hardenable martensitic stainless steel in the annealed condition. The steel blanks have a thickness in the range of 0.5-5.0 mm., and are formed utilizing stamping, forging, pressing, or roller forming techniques or the like into the form of a tank shell components. The shell components are hardened and assembled into a storage tank. The shell components are hardened by application of heat, preferably to between 950° C. and 1100° C. for standard air hardenable martensitic stainless steels. Thereafter, the automotive fuel tank is preferably cooled at a rate greater than 25° C. per minute to achieve a Rockwell C hardness of at least 39. The automotive fuel tank may undergo additional heat treating processes including high temperature or low temperature tempering processes which may incorporate electro-coating.

Abstract: The present invention provides seam-welded, air hardenable steel tubes, methods of manufacturing seam-welded air hardenable steel tubes, tube mills for practicing such methods and applications for using seam-welded, air hardenable steel tubing of the present invention.

Abstract: A method for fabricating multi-component structural members includes brazing a first component of air-hardenable martensitic stainless steel to a second component made of ferrous, stainless or nickel alloy steels. The martensitic stainless steel first component is preferably type 410, 420 or 440 and formed while in the annealed condition. The martensitic stainless steel component is simultaneously brazed and hardened to the second structural component by heating both components to between 950° C. and 1100° C. while depositing a brazing compound between the structural components to form a joint. The structural members are then cooled at a rate of 25° C. per minute or greater so as to transform the air-hardenable martensitic stainless steel to a predominantly martensitic state.

Abstract: A method for making structural automotive components and the like includes providing a blank of air hardenable martensitic stainless steel in the annealed condition. The steel blank has a thickness in the range of 0.5-5.0 mm., and is formed utilizing stamping, forging, pressing, or roller forming techniques or the like into the form of an automotive structural member. The automotive structural member is then hardened by application of heat, preferably to between 950° C. and 1100° C. for standard martensitic stainless steels. Thereafter, the automotive structural member is preferably cooled at a rate greater than 25° C. per minute to achieve a Rockwell C hardness of at least 39. The automotive structural member may undergo additional heat treating processes including high temperature or low temperature tempering processes which may incorporate electro-coating.