Method for increasing the fatigue strength of a predominantly steel mechanical part of a wind turbine and/or for reducing the tendency to form what are called "white etching cracks" or "brittle flakes" in such steel mechanical parts

Abstract

Method for increasing the fatigue strength of a mechanical part of a wind turbine and/or for reducing the tendency to form what are called “white etching cracks” or “brittle flakes” in such a bearing, which includes making one or several of the bearing rings and/or roller elements concerned of the bearing at least partly of a hardened steel having a carbon content between 0.4 and 0.8 percent by weight.

1 . Method for increasing the fatigue strength of the predominantly steel mechanical part ( 1 ) of a wind turbine and/or for reducing the tendency to form what are called “white etching cracks” or “brittle flakes” in such steel mechanical part ( 1 ), which comprises making the mechanical part at least partly out of a hardened steel having a carbon content between 0.4 and 0.8 percent by weight. 
     
     
         2 . Method according to  claim 1 , characterised in that it is applied to a part of the gearbox of a wind turbine. 
     
     
         3 . Method according to  claim 1 , characterised in that the above-mentioned elements of the mechanical part ( 1 ) which are made of hardened steel are hardened by means of full-hardening. 
     
     
         4 . Method according to  claim 3 , characterised in that the above-mentioned elements of the mechanical part ( 1 ) which are made of hardened steel are entirely full-hardened. 
     
     
         5 . Method according to  claim 1 , characterised in that the above-mentioned elements of the mechanical part ( 1 ) which are made of hardened steel are hardened by means of induction hardening. 
     
     
         6 . Method according to  claim 1 , characterised in that the above-mentioned elements of the mechanical part ( 1 ) which are made of hardened steel are hardened by means of laser hardening. 
     
     
         7 . Method according to  claim 1 , characterised in that, when cooling the steel so as to harden it, the variation in temperature as a function of time is controlled such that a predominantly martensitic metal matrix is obtained with little or no carbide formation. 
     
     
         8 . Method according to  claim 1 , characterised in that, when cooling the steel so as to harden it, the variation in temperature as a function of time is controlled such that a predominantly bainitic metal matrix is obtained with little or no carbide formation. 
     
     
         9 . Method according to  claim 7 , characterised in that a hardened steel is used with a martensite content, bainite content respectively, of more than 80 percent by weight. 
     
     
         10 . Method according to  claim 7 , characterised in that the formation of carbides is restricted to less than 2% carbides measured as a portion of the surface. 
     
     
         11 . Method according to  claim 1 , characterised in that the hardened steel is alloyed with one of the following elements or a combination thereof: Cr, Mn, Si, Mo, V. 
     
     
         12 . Method according to  claim 1 , characterised in that it is applied to a bearing, in particular to one or several of the bearing rings ( 2 , 3 ) and/or roller elements ( 4 ) of the bearing ( 1 ) concerned. 
     
     
         13 . Method according to  claim 2 , characterised in that the above-mentioned elements of the mechanical part ( 1 ) which are made of hardened steel are hardened by means of full-hardening. 
     
     
         14 . Method according to  claim 8 , characterised in that a hardened steel is used with a martensite content, bainite content respectively, of more than 80 percent by weight. 
     
     
         15 . Method according to  claim 8 , characterised in that the formation of carbides is restricted to less than 2% carbides measured as a portion of the surface.