Method and apparatus for treating a steel article

A method for treating a steel article to form a high yield strength and ductile alloy comprising the steps of:

• (a) providing a steel composition having a material thickness less than 0.5 inches (12.7 mm), having an initial microstructure of ferrite and pearlite, and having a composition of, by weight,
• carbon between 0.25 and 0.55%
• silicon between 0.15 and 0.35%,
• manganese between 0.40 and 1.0%,
• chromium between 0.80 and 1.10%,
• molybdenum between 0.15 and 0.25%,
• sulfur less than 0.040%,
• phosphorus less than 0.035%,
• balance with iron and other elements and compounds in making steel;
• (b) preheating the provided steel composition at least 0.7° C. (33.3° F.) per second to between the austenization temperature and 815° C. (1500° F.);
• (c) heating the preheated steel composition to a peak temperature between 850-1150° C. (1562-2102° F.) in less than ten seconds;
• (d) holding the heated steel composition at the peak temperature range for between two and ten seconds;
• (e) quenching the heated steel composition to below 100° C. (212° F.) in less than four seconds;
• (f) removing residual quench media from the surface of the quenched steel composition;
• (g) tempering the quenched steel composition at a temperature between 100° C. and 260° C. (212-500° F.) for less than ninety minutes;
• (h) air cooling the tempered steel composition to less than 100° C. (212° F.) having a transformed microstructure of at least 80% martensite and up to 5% bainite by volume, a yield strength of at least 1800 MPa, and a total elongation between 5% and 12%.

A method for treating a steel article to form a high yield strength and ductile alloy comprising the steps of:

• (a) providing a steel composition having a material thickness less than 0.5 inches (12.7 mm), having an initial microstructure of ferrite and pearlite, and having a composition of, by weight,
• carbon between 0.25 and 0.55%
• silicon between 0.15 and 0.35%,
• manganese between 0.40 and 1.0%,
• chromium between 0.80 and 1.10%,
• molybdenum between 0.15 and 0.25%,
• sulfur less than 0.040%,
• phosphorus less than 0.035%,
• balance with iron and other elements and compounds in making steel;
• (b) preheating the provided steel composition to a temperature between 260° C. (500° F.) and 538° C. (1000° F.)
• (c) heating the preheated steel composition to a peak temperature of between 850° C. (1562° F.) and 1150° C. (2102° F.) in less than ten seconds;
• (d) holding the heated steel composition at the peak temperature range for between two and sixty seconds;
• (e) quenching the heated steel composition from the peak temperature range to below 100° C. (212° F.) at a temperature rate reduction of between 400 and 3000° C./sec (752-5432° F./sec);
• (f) removing residual quench media from the surface of the quenched steel composition;
• (g) tempering the quenched steel composition at a temperature from 100° C. to 260° C. (212-500° F.) for less than ninety minutes;
• (h) air cooling the tempered steel composition to less than 100° C. (212° F.) to form a steel article having at least 80% martensite and up to 5% bainite by volume, a yield strength of at least 1800 MPa, a total elongation between 5% and 12%, and having a V50 protection ballistic limit at 30° obliquity angle between 2300 and 2510 feet per second (701-765 m/s) with a .30 caliber armor piercing round for a thickness of 0.25 inches (6.35 mm).

A method for treating a steel article to form a high yield strength and ductile alloy comprising the steps of:

• (a) providing a steel composition having a material thickness less than 0.5 inches (12.7 mm), having an initial microstructure of ferrite and pearlite, and having a composition of, by weight,
• carbon between 0.25 and 0.55%
• silicon between 0.15 and 0.35%,
• manganese between 0.40 and 1.0%,
• chromium between 0.80 and 1.10%,
• molybdenum between 0.15 and 0.25%,
• sulfur less than 0.040%,
• phosphorus less than 0.035%,
• balance with iron and other elements and compounds in making steel;
• (b) preheating the provided steel composition at least 0.7° C. (33.3° F.) per second to not more than 538° C. (1000° F.);
• (c) heating the preheated steel composition to a peak temperature between 850-1150° C. (1562-2102° F.) in less than ten seconds;
• (d) holding the heated steel composition at the peak temperature range for between two and sixty seconds;
• (e) quenching the heated steel composition to below 100° C. (212° F.) in less than four seconds;
• (f) removing residual quench media from the surface of the quenched steel composition;
• (g) tempering the quenched steel composition at a temperature between 100° C. and 260° C. (212-500° F.) for less than ninety minutes;
• (h) air cooling the tempered steel composition to less than 100° C. (212° F.) having a transformed microstructure of at least 80% martensite and up to 5% bainite by volume, a yield strength of at least 1800 MPa, and a total elongation between 5% and 12%.