Method of refining metal surface and metal product by method

Abstract

This invention relates to a method for fining a surface of a metal product to form crystal grains having sizes less than 1 μ m at their surfaces and the metal product produced thereby. The method is comprised of a process for forming crystal grains having sizes less than 1 μ m at the surface of the metal product by projecting or peening shots or projectiles while a power per unit of area of the surface, which power is caused by projecting or peening shots or projectiles, is controlled at a predetermined value.

1 . A method for fining a metal surface, comprising a process for forming crystal grains having sizes less than 1 μm at the surface of a metal product by means of projecting or peening shots or projectiles to the surface while a power per unit of area of the surface is controlled at a predetermined value.  
   
   
       2 . A method for fining a metal surface according to  claim 1 , wherein the shots or projectiles are made from high-carbon steel, ferrous metallic glass, or stainless steel, and the diameters of the shots or projectiles are 30 μm to 2000 μm.  
   
   
       3 . A method for fining a metal surface according to either of claims  1  and  2 , wherein the power per unit of area is greater than 11 KJ/sec*mm 2 .  
   
   
       4 . A method for fining a metal surface according to any of claims  1 ,  2 , and  3 , wherein the process for projecting or peening shots or projectiles to the surface is carrired out while the temperature of the metal surface is controlled to be between room temperature and −150° C.  
   
   
       5 . A method for fining a metal surface according to any of claims  1 - 4 , wherein the unit area is calculated by multiplying a contact surface of a projectile or a shot by a number of the shots or projectiles.  
   
   
       6 . A method for fining a metal surface according to  claim 5 , wherein the unit area is calculated by subtracting the overlapped areas that is calculated based on the number of shots or projectiles that have their contact surfaces overlap from the sum of the contact surfaces.  
   
   
       7 . A metal product having surfaces hardened by the method for fining a metal surface according to any of claims  1 - 6 .