A method for producing a martensitic stainless steel strip, said method comprising: a quenching step wherein a steel strip, which contains, in mass %, from 0.3% to 1.2% of C and from 10.0% to 18.0% of Cr and has a thickness of 1 mm or less, is passed through a quenching furnace so as to be heated to a quenching temperature, and is subsequently cooled to a temperature that is not more than the Ms point; a heat retention conveyance step wherein the steel strip is conveyed to a an annealing furnace, while retaining the temperature of the steel strip so as not to decrease to a temperature less than 80° C.; and an annealing step wherein the steel strip is passed through the annealing furnace in a non-oxidizing gas atmosphere so as to be heated to an annealing temperature.

A method for producing a martensitic stainless steel strip, said method comprising: a quenching step wherein a steel strip, which contains, in mass %, from 0.3% to 1.2% of C and from 10.0% to 18.0% of Cr and has a thickness of 1 mm or less, is passed through a quenching furnace so as to be heated to a quenching temperature, and is subsequently cooled to a temperature that is not more than the Ms point; a heat retention conveyance step wherein the steel strip is conveyed to a an annealing furnace, while retaining the temperature of the steel strip so as not to decrease to a temperature less than 80° C.; and an annealing step wherein the steel strip is passed through the annealing furnace in a non-oxidizing gas atmosphere so as to be heated to an annealing temperature.

This application discloses thin metal strips and methods of making thin metal strip. Particular embodiments of such methods include cooling the thin metal strip to a temperature equal to or less than a bainite or a martensite start transformation temperature B.sub.S or M.sub.S to thereby form bainite and/or martensite, respectively, within the thin metal strip, reheating the thin metal strip to a reheat temperature equal to or greater than transformation temperature Ac.sub.3 and holding the thin metal strip at the reheat temperature for at least 2 seconds and thereby forming austenite within the thin metal strip with at least 75% of austenite grains having a grain size equal to or less than 15 μm, and rapidly recooling the thin metal strip to a temperature equal to or less than the martensite start transformation temperature M.sub.S and thereby providing finer martensite within the thin metal strip from a finer prior austenite.

This application discloses thin metal strips and methods of making thin metal strip. Particular embodiments of such methods include cooling the thin metal strip to a temperature equal to or less than a bainite or a martensite start transformation temperature B.sub.S or M.sub.S to thereby form bainite and/or martensite, respectively, within the thin metal strip, reheating the thin metal strip to a reheat temperature equal to or greater than transformation temperature Ac.sub.3 and holding the thin metal strip at the reheat temperature for at least 2 seconds and thereby forming austenite within the thin metal strip with at least 75% of austenite grains having a grain size equal to or less than 15 μm, and rapidly recooling the thin metal strip to a temperature equal to or less than the martensite start transformation temperature M.sub.S and thereby providing finer martensite within the thin metal strip from a finer prior austenite.

A method of heat treating a high strength cold rolled steel strip including a) soaking a cold rolled steel strip, b) cooling the soaked steel strip c) heat treating the cooled strip; d) cooling the heat treated steel strip to ambient temperature range;
such that the steel strip has a microstructure including various ferrites, retained austenite and martensite. The main components in the steel composition includes carbon, manganese, silicon and aluminium in addition to iron.

A method of heat treating a high strength cold rolled steel strip including a) soaking a cold rolled steel strip, b) cooling the soaked steel strip c) heat treating the cooled strip; d) cooling the heat treated steel strip to ambient temperature range;
such that the steel strip has a microstructure including various ferrites, retained austenite and martensite. The main components in the steel composition includes carbon, manganese, silicon and aluminium in addition to iron.

A heat treatment of a high strength cold rolled steel strip includes the steps of a) soaking a cold rolled steel strip, b) cooling the soaked steel strip c) heat treating the cooled strip; d) cooling the heat treated steel strip to ambient temperature range;
such that the steel strip has a microstructure including various ferrites, retained austenite and martensite. The main components in the steel composition include carbon, manganese, silicon and aluminium in addition to iron.

A heat treatment of a high strength cold rolled steel strip includes the steps of a) soaking a cold rolled steel strip, b) cooling the soaked steel strip c) heat treating the cooled strip; d) cooling the heat treated steel strip to ambient temperature range;
such that the steel strip has a microstructure including various ferrites, retained austenite and martensite. The main components in the steel composition include carbon, manganese, silicon and aluminium in addition to iron.

A method of heat treating a cold rolled steel strip includes soaking a cold rolled steel strip having a specific composition above (Ac3−60)° C. for a certain duration thereby obtaining a cold rolled strip having a partially austenitic microstructure; cooling of the resulting soaked steel strip to a temperature below Ms; heating and heat treating the cooled steel strip in the temperature range of Bs-Ms; and cooling the heat treated steel strip to ambient temperature.

A method of heat treating a cold rolled steel strip includes soaking a cold rolled steel strip having a specific composition above (Ac3−60)° C. for a certain duration thereby obtaining a cold rolled strip having a partially austenitic microstructure; cooling of the resulting soaked steel strip to a temperature below Ms; heating and heat treating the cooled steel strip in the temperature range of Bs-Ms; and cooling the heat treated steel strip to ambient temperature.