Martensitic Stainless Steel and Manufacturing Process Therefor

Abstract

The present invention provides a martensitic stainless steel and manufacturing process therefor, the mass ratio of chemical elements of the stainless steel is C: 0.01˜0.18 wt %, Si: 0.4˜1.5 wt %; Mn: 0.4˜3.0 wt %, P: ≤0.04 wt %, S: 0.002˜0.01 wt %, Cr: 11.0˜15.0 wt %, N: 0.01˜0.15 wt %, Nb: 0.001˜0.01 wt %, V: 0.05˜0.25 wt %, Ti: 0.001˜0.01 wt %, Mo: 0.01˜1.50 wt %, B: 0.0005˜0.001 wt %, and balance being Fe and other unavoidable impurities. Further, the present invention provides a method for producing a martensitic stainless steel. The martensitic stainless steel of this present patent has a high hardness and high toughness and has excellent high-temperature oxidation resistance.

1 . A martensitic stainless steel, wherein the mass ratio of chemical elements is C: 0.01˜0.18 wt %, Si: 0.4˜1.5 wt %, Mn: 0.4˜3.0 wt %, P: ≤0.04 wt %, S: 0.002˜0.01 wt %, Cr: 11.0˜15.0 wt %, N: 0.01˜0.15 wt %, Nb: 0.001˜0.01 wt %, V: 0.05˜0.25 wt %, Ti: 0.001˜0.01 wt %, Mo: 0.01˜1.50 wt %, B: 0.0005˜0.001 wt %, and balance being Fe and other unavoidable impurities. 
     
     
         2 . The martensitic stainless steel according to  claim 1 , wherein the mass ratio of chemical elements is C: 0.03˜0.15 wt %, Si: 0.53˜1.25 wt %, Mn: 0.45˜2.45 wt %, Cr: 11.2˜14.5 wt %, N: 0.01˜0.08 wt %, Nb: 0.001˜0.007 wt %, V: 0.05˜0.23 wt %, Ti: 0.002˜0.008 wt %, Mo: 0.01˜1.10 wt %, B: 0.0005˜0.0009 wt %, and balance being Fe and other unavoidable impurities. 
     
     
         3 . The martensitic stainless steel according to  claim 1 , wherein the mass ratio of chemical elements satisfies a relationship: 0.02 wt %≤C+N≤0.20 wt %. 
     
     
         4 . The martensitic stainless steel according to  claim 1 , wherein the mass ratio of chemical elements satisfies a relationship: V+Ti+Nb≤0.25 wt %. 
     
     
         5 . The martensitic stainless steel according to  claim 1 , wherein the microstructure of the martensitic stainless steel is a complex phase structure of martensite and residual austenite. 
     
     
         6 . The martensitic stainless steel according to  claim 5 , wherein in the microstructure, the phase ratio of the martensite is 55˜65%, and the phase ratio of the residual austenite is 35˜45%. 
     
     
         7 . The martensitic stainless steel according to  claim 1 , wherein the martensitic stainless steel is prepared by the following steps:
 (1) Hot rolling of steel billets or contiguous casting billets into hot rolled steel plates or steel strips, and annealing;   (2) Heating the annealed hot-rolled steel plates or steel strips to 850˜1000° C. and insulating for 5˜30 min, then rapidly cooling to a two-phase zone of the martensite and austenite with a speed greater than or equal to 30° C./s; the cooling termination temperature is 150˜220° C.; then heating the steel plates or strips to 350˜500° C., and air cooling to room temperature to obtain the martensitic stainless steel.   
     
     
         8 . A method for producing the martensitic stainless steel, which includes the following steps:
 (1) Hot rolling of steel billets or casting billets into hot rolled steel plates or steel strips, and annealing;   (2) Heating the annealed hot-rolled steel plates or steel strips to 850˜1000° C. and insulating for 5˜30 min, then rapidly cooling to a two-phase zone of martensite and austenite with a speed greater than or equal to 30° C./s; the cooling termination temperature is 150˜220° C.; then heating the steel plates or strips to 350˜500° C., and air cooling to room temperature to obtain the martensitic stainless steel,   wherein the mass ratio of chemical elements of the martensitic stainless steel is C: 0.01˜0.18 wt %, Si: 0.4˜1.5 wt %, Mn: 0.4˜3.0 wt %, P: ≤0.04 wt %, S: 0.002˜0.01 wt %, Cr: 11.0˜15.0 wt %, N: 0.01˜0.15 wt %, Nb: 0.001˜0.01 wt %, V: 0.05˜0.25 wt %, Ti: 0.001˜0.01 wt %, Mo: 0.01˜1.50 wt %, B: 0.0005˜0.001 wt %, and balance being Fe and other unavoidable impurities.   
     
     
         9 . The method according to  claim 8 , wherein the mass ratio of chemical elements of the martensitic stainless steel is C: 0.03˜0.15 wt %, Si: 0.53˜1.25 wt %, Mn: 0.45˜2.45 wt %, Cr: 11.2˜14.5 wt %, N: 0.01˜0.08 wt %, Nb: 0.001˜0.007 wt %, V: 0.05˜0.23 wt %, Ti: 0.002˜0.008 wt %, Mo: 0.01˜1.10 wt %, B: 0.0005˜0.0009 wt %, and balance being Fe and other unavoidable impurities. 
     
     
         10 . The method according to  claim 8 , wherein the mass ratio of chemical elements of the martensitic stainless steel satisfies a relationship:
   0.02 wt %≤C+N≤0.20 wt %.
   
     
     
         11 . The method according to  claim 8 , wherein the mass ratio of chemical elements of the martensitic stainless steel satisfies a relationship: V+Ti+Nb≤0.25 wt %. 
     
     
         12 . The method according to  claim 8 , wherein the microstructure of the martensitic stainless steel is a complex phase structure of martensite and residual austenite. 
     
     
         13 . The method according to  claim 12 , wherein in the microstructure, the phase ratio of the martensite is 55˜65%, and the phase ratio of the residual austenite is 35˜45%. 
     
     
         14 . The martensitic stainless steel according to  claim 2 , wherein the mass ratio of chemical elements satisfies a relationship: 0.02 wt %≤C+N≤0.20 wt %. 
     
     
         15 . The martensitic stainless steel according to  claim 2 , wherein the mass ratio of chemical elements satisfies a relationship: V+Ti+Nb≤0.25 wt %. 
     
     
         16 . The martensitic stainless steel according to  claim 2 , wherein the microstructure of the martensitic stainless steel is a complex phase structure of martensite and residual austenite. 
     
     
         17 . The method according to  claim 9 , wherein the mass ratio of chemical elements of the martensitic stainless steel satisfies a relationship: 0.02 wt %≤C+N≤0.20 wt %. 
     
     
         18 . The method according to  claim 9 , wherein the mass ratio of chemical elements of the martensitic stainless steel satisfies a relationship: V+Ti+Nb≤0.25 wt %. 
     
     
         19 . The method according to  claim 9 , wherein the microstructure of the martensitic stainless steel is a complex phase structure of martensite and residual austenite.