Fine-grained martensitic stainless steel and method thereof

A method of producing an alloy comprising:

• preparing an alloy comprising (wt. %):
• greater than 0.05% and less than 0.15% C;
• greater than 7.5% and less than 15% Cr;
• greater than 1% and less than 7% Ni;
• up to about 15% Co;
• up to about 8% Cu;
• up to about 8% Mn;
• up to about 4% Si;
• up to about 6% (Mo+W);
• greater than 0.01% and less than 0.75% Ti;
• less than 0.1% N;
• up to about 2% Al;
• and
• at least about 40% Fe;
• thermal mechanically treating by austenitizing the alloy at a temperature greater than 1000° C.,
• hot working the alloy at a temperature greater than 1000° C. to impart a true strain of greater than about 0.20 (20%);
• and
• cooling the alloy to room temperature to obtain a fine-grained martensitic microstructure in which the ASTM grain size is greater than or equal to 5.

A method of producing a fine-grained iron base alloy comprising:

• preparing an iron base alloy consisting essentially of (wt. %):
• 0.05<C<0.15;
• 7.5<Cr<15;
• 1<Ni<7;
• Co<10, Cu<5;
• Mn<5;
• Si<1.5;
• (Mo+W)<4;
• 0.01<Ti<0.75;
• 0.135<(1.17 Ti+0.6 Nb+0.6 Zr+0.31 Ta+0.31 Hf<1;
• V<2;
• N<0.1;
• AI<0.2;
• (AI+Si+Ti)>0.01;
• each of B, CE, CA, Mg, Sc, Y, La and Be less than 0.1;
• P<0.1;
• S<0.05;
• each of Sn, SB, O, Pb and other impurities less than 0.1;
• and the balance essentially iron;
• thermal mechanically treating by austenitizing it at a temperature above 1000° C., hot working the alloy at a temperature greater than 1000° C. to impart a true strain of greater than 0.15 (15%);
• and cooling the alloy to room temperature to obtain a fine-grained martensitic microstructure in which the ASTM grain size number is greater than or equal to 5.