High strength and toughness stainless steel strip and process for the production of the same

A high strength and toughness stainless steel strip which consists essentially of in mass %:

• C:
• up to 0.1% (exclusive of 0%);
• Si:
• more than 1.0% and not more than 4.0%;
• Mn:
• up to 5.0% (exclusive of 0%);
• Ni:
• from 4.0 to 10.0%;
• Cr:
• from 12.0 to 18.0%;
• Cu:
• up to 5.0% (exclusive of 0%);
• Mo:
• from 1.0 to 5.0%;
• N:
• up to (exclusive of 0% );
• the balance being Fe and unavoidable impurities with the proviso that
• C+N.gtoreq.0.1%
• is satisfied, and wherein the alloying elements are adjusted so that a value of Md(N) defined by the following equation:
• Md(N)=580 -520.times.[% C]-2.times.[% Si]-16.times.[% Mn]-16.times.[% Cr]-23.times.[% Ni]-26.times.[% Cu]-10.times.[Mo %]
• falls within the range between 20 and 100, said strip having a metallic structure of a retained austenitic phase containing from 30 to 80% by volume of a work induced martensitic phase.

A process for the production of a high strength and toughness stainless steel strip which comprises the steps of:

• solution treating a stainless steel strip which consists essentially of in mass %:
• C:
• up to 0.1% (exclusive of 0%);
• Si:
• more than 1.0% and not more than 4.0%;
• Mn:
• up to 5.0% (exclusive of 0%);
• Ni:
• from 4.0 to 10.0%;
• Cr:
• from 12.0 to 18.0%;
• Cu:
• up to 5.0% (inclusive of non-addition);
• Mo:
• from 1.0 to 5.0%;
• N:
• up to (exclusive of 0%);
• the balance being Fe and unavoidable impurities with the proviso that
• C+N.gtoreq.0.1%
• is satisfied, and wherein the alloying elements are adjusted so that a value of Md(N) defined by the following equation:
• Md(N)=580-520.times.[% C]-2.times.[% Si]-16.times.[% Mn]-16.times.[% Cr]-23.times.[% Ni]-26.times.[% Cu]-10.times.[Mo %]
• falls within the range between 20 and 100 at a temperature within the range between 980.degree. and 1150.degree. C. and under conditions for forming grains of a single austenite phase having an average diameter of from 5 to 50 .mu.m, each grain including not more than 5 undissolved precipitates having a size of more than 100 nm,
• cold rolling the strip having the so obtained metallic structure at a rolling reduction sufficient to form 30 to 80% by volume of work induced martensite, and
• aging the strip at a temperature of from 300.degree. to 650.degree. C. for 0.5 to 5 minutes.

An ID saw blade for slicing a semi-conducting material comprising a generally annular disc of a high strength and toughness stainless steel strip and fine particulate diamond fixed on the inner periphery of said annular disc constituting a blade edge for slicing the semi-conducting material, said strip consisting essentially of in mass %:

• C:
• up to 0.1% (exclusive of 0%);
• Si:
• more than 1.0% and not more than 4.0%;
• Mn:
• up to 5.0% (exclusive of 0%);
• Ni:
• from 4.0 to 10.0%;
• Cr:
• from 12.0 to 18.0%;
• Cu:
• up to 5.0% (exclusive of 0%);
• Mo:
• from 1.0 to 5.0%;
• N:
• up to (exclusive of 0%);
• the balance being Fe and unavoidable impurities with the proviso that
• C+N.gtoreq.0.1%
• is satisfied, and wherein the alloying elements are adjusted so that a value of Md(N) defined by the following equation:
• Md(N)=580-520.times.[% C]-2.times.[% Si]-16.times.[% Mn]-16.times.[% Cr]-23.times.[% Ni]-26.times.[% Cu]-10.times.[Mo %]
• falls within the range between 20 and 100, said strip having a metallic structure of a retained austenitic phase containing from 30 to 80% by volume of a work induced martensitic phase, said strip having a tensile strength of at least 1800 N/mm.sup.2 and an Erichsen break stress of at least 1000 N/mm.sup.2.