Method for preventing carbon steel from intergranular cracking

Abstract

A method for preventing carbon steel from intergranular cracking utilizing a reducing gas instead of nitrogen gas for a heat treatment of feeder pipes for a pressurized heavy water reactor (PHWR) nuclear power plant. This heat treatment protects carbon from oxidation to prevent the formation of decarburized layers so that the feeder pipes can be prevented from intergranular cracking. In addition, intergranular segregation of impurities is inhibited and intergranular strength of the carbon steel is enhanced. Therefore, no intergranular cracking occurs despite the concentration of stress.

1 . A method for preventing carbon steel from intergranular cracking, the method comprising heat treatment of carbon steel in a mixed reducing gas atmosphere in order to prevent the formation of a decarburized layer in the carbon steel. 
   
   
       2 . The method according to  claim 1 , wherein the mixed reducing gas contains hydrogen gas. 
   
   
       3 . The method according to  claim 2 , wherein the hydrogen gas is present in an amount of 25 vol % or more, based on the total volume of the mixed reducing gas. 
   
   
       4 . The method according to  claim 1 , wherein the heat treatment is normalizing. 
   
   
       5 . The method according to  claim 1 , wherein the carbon steel is a feeder pipe for a pressurized heavy water reactor (PHWR) nuclear power plant.