Method for the manufacture of steel products of a precipitation hardened martensitic steel, steel products obtained with such method and use of said steel products

Abstract

A method for the manufacture of steel products and products thus produced, wherein steel is subjected to precipitation hardening in a martensitic structure subsequent to soft annealing and thereafter shaping. The method steps include shaping followed by solution annealing between 1200° C. and 1050° C., quenching from the solution annealing temperature with a quenching speed of at least 5° C. per second to a temperature below 500° C., subjecting said steel to an isothermal martensitic transformation and subsequently hardening the steel at a temperature between 450° C. and 550° C. to precipitate particles out from solution into said martensitic structure.

What is claimed is:  
     
         1 . A method for the manufacture of a steel product comprising the steps of: 
 (a) subjecting the steel to precipitation hardening in a martensitic structure subsequent to soft annealing;    (b) shaping said steel, followed by solution annealing between a temperature of 1200° C. and 1050° C. and for a time period of from 5 to 30 minutes;    (c) quenching the steel from the solution annealing temperature to a temperature below 500° C. with a quenching rate of at least 5° C. per second, said quenched steel being subjected to an isothermal martensitic transformation; and    (d) hardening at a temperature between 450° C. and 550° C. for at least 3 minutes to cause particles to precipitate out from solution into the martensitic structure.    
     
     
         2 . The method according to  claim 1 , wherein the quenched steel is subjected to an isothermal martensitic transformation at a temperature between −30° C. and −50° C. for at least one hour.  
     
     
         3 . The method according to  claim 1 , wherein, between the solution annealing and the quenching of the steel, the steel is subjected to a sensitizing procedure between 950° C. and 850° C. for at least 5 minutes thereby optimizing initiation of the isothermal martensitic transformation.  
     
     
         4 . The method according to  claim 3 , wherein the sensitizing procedure homogeneously nucleates martensite during the isothermal martensitic transformation.  
     
     
         5 . The method according to  claim 1 , wherein the steel comprises chromium (Cr) in a weight percentage between 10% and 14%.  
     
     
         6 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a cap of an electric rotary shaver.  
     
     
         7 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a cutter of an electric rotary shaver.  
     
     
         8 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a cap of an electric translation vibration shaver.  
     
     
         9 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a cutter of an electric translation vibration shaver.  
     
     
         10 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a blade shaver.  
     
     
         11 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a cutter in a domestic appliance.  
     
     
         12 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a knife in a domestic appliance.  
     
     
         13 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a spring in a domestic appliance.  
     
     
         14 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a medical instrument.  
     
     
         15 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a dental instrument.  
     
     
         16 . A steel product manufactured by the method of  claim 1 , wherein the steel product is a diaphragm plate spring in a fluid valve.