Martensitic stainless steel, method for making parts from said steel and parts thus made

Abstract

Martensitic stainless steel, characterised in that it comprises, in percentages by weight: 0.22%≦C≦0.32% 0.05%≦N≦0.15%, with 0.33%≦C+N≦0.43% 10%≦Cr≦12.4% 0.10%≦V≦0.40% 0.10%≦Mo≦1.0% trace levels≦Ni≦1.0% trace levels≦Mn≦1.0% trace levels≦Si≦1.0% trace levels≦W≦1.0% trace levels≦Co≦1.0% trace levels≦Cu≦1.0% trace levels≦Ti≦0.010% trace levels≦Nb≦0.050% trace levels≦Al≦0.050% trace levels≦S≦0.020% trace levels≦O≦0.0040% trace levels≦P≦0.03% trace levels≦B≦0.0050% trace levels≦Ca≦0.020% trace levels≦Se≦0.010% trace levels≦La≦0.040% trace levels≦Ce≦0.040% the remainder being iron and impurities resulting from the production operation. Method for producing a component from this steel, and component obtained in this manner, such as a mould element for the production of articles of plastics material.

1 . Martensitic stainless steel, characterised in that it comprises, in percentages by weight:
 0.22%≦C≦0.32%   0.05%≦N≦0.15%, with 0.33%≦C+N≦0.43%   10%≦Cr≦12.4%   0.10%≦V≦0.40%   0.10%≦Mo≦1.0%   trace levels≦Ni≦1.0%   trace levels≦Mn≦1.0%   trace levels≦Si≦1.0%   trace levels≦W≦1.0%   trace levels≦Co≦1.0%   trace levels≦Cu≦1.0%   trace levels≦Ti≦0.010%   trace levels≦Nb≦0.050%   trace levels≦Al≦0.050%   trace levels≦S≦0.020%   trace levels≦O≦0.0040%   trace levels≦P≦0.03%   trace levels≦B≦0.0050%   trace levels≦Ca≦0.020%   trace levels≦Se≦0.010%   trace levels≦La≦0.040%   trace levels≦Ce≦0.040% the remainder being iron and impurities resulting from the production operation.   
     
     
         2 . Steel according to  claim 1 , characterised in that 0.08%≦N≦0.12%. 
     
     
         3 . Steel according to  claim 1 , characterised in that 11.0%≦Cr≦12.4%. 
     
     
         4 . Steel according to  claim 1 , characterised in that 0.15%≦V≦0.35%. 
     
     
         5 . Steel according to  claim 1 , characterised in that trace levels≦Si≦0.5%. 
     
     
         6 . Steel according to  claim 1 , characterised in that 0.10%≦Mo+W/2≦1.20%. 
     
     
         7 . Steel according to  claim 1 , characterised in that trace levels≦Ti≦0.003%. 
     
     
         8 . Steel according to  claim 1 , characterised in that trace levels≦Nb≦0.010%. 
     
     
         9 . Steel according to  claim 1 , characterised in that trace levels≦O≦0.0015%. 
     
     
         10 . Steel according to  claim 1 , characterised in that trace levels≦S≦0.003%. 
     
     
         11 . Steel according to  claim 1 , characterised in that trace levels Mn≦+Cu+Co≦1.8%. 
     
     
         12 . Method for producing a component of martensitic stainless steel, characterised in that:
 a steel according to  claim 1  is produced, cast, forged or rolled and annealed;   the steel is machined in order to confer thereon the shape of the component;   the machined steel is austenitised at a temperature of from 990-1040° C., preferably 1000-1030° C.;   the austenitised steel is quenched at a rate of between 10 and 40° C./min in the temperature range of from 800 to 400° C.;   two tempering operations are carried out on the quenched steel, in order to confer thereon its final hardness.   
     
     
         13 . Method according to  claim 12 , characterised in that the tempering operations are each carried out at a temperature of from 200 to 400° C., preferably from 300 to 380° C. for a minimum of 2 hours whilst ensuring that the nominal temperature is maintained in the core for at least 1 hour, in order to obtain a hardness of from 49 to 55 HRC. 
     
     
         14 . Method according to  claim 12 , characterised in that the tempering operations are each carried out at a temperature of from 530 to 560° C. for a minimum of 2 hours whilst ensuring that the nominal temperature is maintained in the core for at least 1 hour, in order to obtain a hardness of between 42 and 50 HRC. 
     
     
         15 . Component of martensitic stainless steel, characterised in that the element produced using the method is produced in accordance with  claim 12 . 
     
     
         16 . Component according to  claim 15 , characterised in that it is a mould element which is intended for the production of articles of plastics materials.