Formed product and method for production thereof

Abstract

A formed product, characterized in that it is produced by using, as a material, a steel having an ultra fine structure comprising ferrite grains having an average grain diameter of 3 μm or less and by a method comprising only a forming step and including none of refining steps; and a method for producting the above formed product with ease. The formed product contains no alloying element and has been subjected to no refining step, and has been imparted with high strength and high toughness by the above ultra fine structure.

1 - 12 . (canceled) 
   
   
       13 . A production method for a screw or bolt without refining treatments comprising employing a steel bar or wire having an ultra fine structure comprising ferrite grains of average grain diameter of 1 μm or less as raw material, and forming only by at least one process of cold working and warm working, not followed by refining steps. 
   
   
       14 . The production method for a screw or bolt of  claim 13 , in which said steel bar or wire has an ultra fine structure comprising ferrite grains of average grain diameter of 0.7 μm or less as raw material. 
   
   
       15 . (canceled) 
   
   
       16 . (canceled) 
   
   
       17 . A production method for a screw or bolt, which comprises using a steel bar or wire having an ultra fine structure comprising elongated ferrite grains of grain diameter shorter diameter of 3 μm or less as raw material, by warm working or cold working of material having ultra fine structure, and being produced by a forming step only, not followed by refining steps. 
   
   
       18 . A steel composition comprising, by weight,
 C: 0.001% to 1.2%,   Si: 2% or less,   Mn: 3% or less,   P: 0.2% or less,   S: 0.1% or less,   Al: 0.3% or less,   N: 0.02% or less,   
     and a balance of Fe and unavoidable impurities.