Method for annealing or hardening of metals

Abstract

The invention relates to a method for annealing or hardening of a metal or an alloy in a controlled furnace atmosphere, wherein said furnace atmosphere is a hydrogen-free atmosphere comprising nitrogen and carbon monoxide.

1 . Method for annealing or hardening of a metal or an alloy in a furnace atmosphere, comprising providing a hydrogen-free atmosphere comprising nitrogen and carbon monoxide. 
   
   
       2 . Method according to  claim 1 , wherein said furnace atmosphere comprises a carbon containing enrichment gas. 
   
   
       3 . Method according to  claim 2 , wherein said enrichment gas is selected from acetylene, propane and methane. 
   
   
       4 . Method according to  claim 1 , comprising removing hydrogen from syngas, from endogas or from cracked methanol for producing said furnace atmosphere. 
   
   
       5 . Method according to  claim 1 , comprising reacting nitrogen containing less than 10% oxygen over graphite for producing said furnace atmosphere. 
   
   
       6 . Method according to  claim 1 , comprising injecting formic acid into a heated reactor filled with sulphuric acid or phosphoric acid and dissociating said formic acid for forming the carbon monoxide. 
   
   
       7 . Method according to  claim 1 , comprising measuring carbon monoxide and temperature of said furnace atmosphere by a heated external oxygen probe or a carbon dioxide gas analyser for controlling the annealing or hardening. 
   
   
       8 . Method according to  claim 1 , wherein said furnace atmosphere comprises between 1% and 5% CO, between 90% and 99% N 2  and between 0.05% and 1% hydrocarbon gas. 
   
   
       9 . Method according to  claim 1  comprising subjecting said metal or alloy to a hardening process comprising heating said metal or alloy and quenching said metal or alloy. 
   
   
       10 . Method according to  claim 1 , further comprising manufacturing fasteners made of metal or alloy in said furnace atmosphere.