Maraging steel and process for manufacturing a strip or a part cut out of a strip of cold-rolled maraging steel

A strip or part of maraging steel having a thickness of less than 1 mm, wherein the steel has a fine-grained structure with an ASTM index of higher than 8, and a composition that comprises, in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• P≦0.005%
• H≦0.0003%
• O≦0.001%
• iron and impurities resulting from smelting, the steel composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4,
• the steel having an elastic limit after hardening of greater than 1850 MPa.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4,
• wherein after recrystallization annealing, the strip or the part is subjected to cold rolling with a reduction ratio of between 1% and 10%.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4,
• wherein the maraging steel is remelted after smelting under vacuum by the VAR process or in a first step is remelted under vacuum by the VAR process or under electrically conductive slag of the ESP process and in a second step is remelted under vacuum by the VAR process.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4,
• wherein the hardening heat treatment comprises holding the strip or part between 450° C. and 550° C. for 1 to 10 hours.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4,
• wherein the hardening heat treatment is performed in a through furnace at a temperature of between 600° C. and 700° C. for a duration of between 30 seconds and 3 minutes.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, the steel having an elastic limit after hardening of greater than 1850 MPa, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4.

A process for manufacturing a strip or of a part cut out of a strip of cold-rolled maraging steel and hardened by a hardening heat treatment, the steel having an elastic limit after hardening of greater than 1850 MPa, wherein, before the hardening heat treatment is performed, the strip or the part is subjected to cold plastic deformation with a degree of working greater than 30% and the strip or the part is subjected to recrystallization annealing in order to obtain a fine-grained structure with ASTM index higher than 8, the chemical composition of the steel comprising in % by weight based on total weight:

• 12%≦Ni≦24.5%
• 2.5%≦Mo≦12%
• 4.17%≦Co≦20%
• Al≦0.15%
• Ti≦0.1%
• N≦0.003%
• Si≦0.1%
• Mn≦0.1%
• C≦0.005%
• S≦0.001%
• P≦0.005%
• H≦0.0003%
• O≦0.001%;
• and
• iron and impurities resulting from smelting, the chemical composition also satisfying the following relationships:
• 20%≦Ni+Mo≦27%
• 50≦Co×Mo≦200
• Ti×N≦2×10−4, wherein after recrystallization annealing, the strip or the part is subjected to cold rolling with a reduction ratio of between 1% and 10%.