Welding base metal for recycling railway wheel and method for recycling railway wheel using the same

Abstract

The welding base metal for recycling a railway wheel may be used as a surface hardened layer of a railway wheel because the welding base metal has high hardness while exhibiting a similar property to the railway wheel. Furthermore, the welding base metal can change the metal structure of the recycled railway wheel, and thus delay the initial wear time of the recycled railway wheel. The method for recycling a railway wheel may overlay-weld the damaged railway wheel to its original size, form a surface hardened layer, and change the metal structure of the railway wheel by changing the composition of the welding base metal and performing the pre-heat treatment and the post heat treatment, thereby minimizing the occurrence of damage to the recycled railway wheel.

What is claimed is: 
     
         1 . A welding base metal which is used for a process of overlay-welding a worn railway wheel and then forming a surface hardened layer by welding the overlay-welded railway wheel in order to recycle the worn railway wheel,
 wherein the welding base metal contains carbon of 0.1 to 0.25 wt %, silicon 1.0 to 2.0 wt %, manganese of 2.2 to 3.3 wt %, nickel 0.45 to 0.65 wt %, chromium 0.85 to 2.45 wt %, molybdenum 0.01 to 0.4 wt %, titanium 0.01 to 0.05 wt %, vanadium 0.03 to 0.1 wt %, niobium 0.01 to 0.1 wt %, inevitable impurities and the remainder of iron.   
     
     
         2 . A method for recycling a railway wheel, comprising:
 a railway wheel overlay-welding step of overlay-welding a worn railway wheel by welding the worn railway wheel with a first welding base metal; and   a surface hardened layer forming step of forming a surface hardened layer by welding the overlay-welded railway wheel with a second welding base metal,   wherein the first welding base metal contains carbon of 0.05 to 0.15 wt %, silicon 0.2 to 1.0 wt %, manganese 1.0 to 2.0 wt %, chromium 0.6 to 1.2 wt %, inevitable impurities and the remainder of iron,   wherein the second welding base metal contains carbon of 0.1 to 0.25 wt %, silicon 1.0 to 2.0 wt %, manganese of 2.2 to 3.3 wt %, nickel 0.45 to 0.65 wt %, chromium 0.85 to 2.45 wt %, molybdenum 0.01 to 0.4 wt %, titanium 0.01 to 0.05 wt %, vanadium 0.03 to 0.1 wt %, niobium 0.01 to 0.1 wt %, inevitable impurities and the remainder of iron,   wherein the railway wheel is a railway wheel of any one of a freight car, a passenger car, an urban railway train and a subway train.   
     
     
         3 . The method of  claim 2 , wherein the welding in the railway wheel overlay-welding step and the surface hardened layer forming step is performed by any one of gas shield welding, open arc welding, submerged arc welding and automatic welding. 
     
     
         4 . The method of  claim 2 , further comprising a railway wheel pre-heating step of pre-heating the worn railway wheel, before the railway wheel overlay-welding step. 
     
     
         5 . The method of  claim 4 , wherein the railway wheel pre-heating step is performed in a temperature range of 250° C. to 300° C. 
     
     
         6 . The method of  claim 2 , further comprising a railway wheel post heat treatment step of post heat-treating the welded railway wheel, after the surface hardened layer forming step. 
     
     
         7 . The method of  claim 6 , wherein the railway wheel post heat treatment step is performed in a temperature range of 240° C. to 260° C. for four hours. 
     
     
         8 . The method of  claim 7 , further comprising, after the railway wheel post heat treatment step is performed in a temperature range of 240° C. to 260° C. for four hours:
 slowly cooling the railway wheel at a temperature of 260° C. at a speed of 40° C. per hour for four hours until the temperature of the railway wheel becomes 100° C.; and 
 slowing cooling the railway wheel under the atmospheric condition while the temperature is maintained at 100° C. or less. 
 
     
     
         9 . The method of  claim 8 , further comprising a railway wheel processing step of cutting or grinding the heat-treated railway wheel, after the railway wheel post heat treatment step. 
     
     
         10 . The method of  claim 9 , wherein the cutting or grinding process is performed by a CNC turning machine.