Bainitic steel for rock drilling component

Abstract

A bainitic steel comprising, in weight % (wt %) C: 0.16-0.23, Si: 0.8-1.0, Mo: 0.67-0.9, Cr: 1.10-1.30, V: 0.18-0.4, Ni: 1.60-2.0, Mn: 0.65-0.9, P: 50.020, S: 50.02, Cu: <0.20, N: 0.005-0.012, balance Fe and unavoidable impurities.

What is claimed is: 
     
         1 . A top hammer drill rod, comprising:
 a central rod portion extending longitudinally from a first end to a second end;   a case hardened, threaded male connector at the first end; and   a case hardened, threaded female connector at the second end,   wherein the drill rod is formed from a steel comprising, in weight % (wt %):   C: 0.16-0.23   Si: 0.85-0.95   Mo: 0.67-0.9   Cr: 1.10-1.30   V: 0.18-0.4   Ni: 1.60-2.0   Mn: 0.65-0.9   P: 0.020   S: ≤0.02   Cu: ≤0.20   N: 0.005-0.012   balance Fe and unavoidable impurities,   wherein at least one of the male connector and the female connector includes a core region and a surface zone,   wherein a microstructure of the surface zone includes martensite, and   wherein a microstructure of the core region includes bainite.   
     
     
         2 . The top hammer drill rod according to  claim 1 , wherein the microstructure of the core region consists of martensite and bainite. 
     
     
         3 . The top hammer drill rod according to  claim 2 , wherein the amount of Si in the steel is 0.85-0.95 wt %. 
     
     
         4 . The top hammer drill rod according to  claim 3 , wherein the amount of Si in the steel is 0.87-0.89 wt %. 
     
     
         5 . The top hammer drill rod according to  claim 2 , wherein the amount of Mo in the steel is 0.70-0.80 wt %. 
     
     
         6 . The top hammer drill rod according to  claim 2 , wherein the amount of Cr in the steel is 1.20-1.25 wt %. 
     
     
         7 . The top hammer drill rod according to  claim 2 , wherein the amount of V in the steel is 0.20-0.30 wt %. 
     
     
         8 . The top hammer drill rod according to  claim 2 , wherein the amount of N in the steel is 0.008-0.012 wt %. 
     
     
         9 . The top hammer drill rod according to  claim 2 , wherein the top hammer drill rod is used during air-cold top hammer drilling above ground.