Steel cord with a brass coating enriched with iron particles

Abstract

A steel cord that is suitable for reinforcing rubber articles such as tires. The inventive steel cord enables to completely eliminate the presence of cobalt in a tire when combined with the proper cobalt free compound. Advantageously the steel cord adheres equally well to rubbers containing organic cobalt salts. The inventive wire is different from prior art steel cords in that the brass coating now comprises iron particles. The iron particles have a size between 10 nm and 10 000 nm. The presence of iron mitigates the adhesion retention loss of the rubber to steel cord bond in a hot and humid environment. It is a further advantage that the inventive steel cord does not contain any intentionally added cobalt thereby contributing to the elimination of harmful substances in the production area as well as the environment.

1 - 14 . (canceled) 
     
     
         15 . A method of producing a filament of a steel cord comprising the following steps:
 a. providing an intermediate steel wire having an intermediate diameter;   b. electrolytically coating said intermediate steel wire with copper, iron and zinc;   c. subjecting said copper-iron-zinc coated intermediate steel wire to a heat treatment to diffuse the zinc into the copper at a temperature of at least 420° C. and below 530° C. resulting in an intermediate steel wire with a brass coating enriched with iron particles;   d. optionally removing the zinc oxide and iron oxide from the surface of said intermediate steel wire with a brass coating enriched with iron particles by immersion in an acid bath; and   e. subjecting the intermediate steel wire with a brass coating enriched with iron particles to a wet wire drawing operation thereby obtaining said filament,   
       wherein by the wet wire drawing operation the iron particles as present on the intermediate steel wire with a brass coating enriched with iron particles are diminished to a size of below 10,000 nm and larger than 10 nm. 
     
     
         16 . The method according to  claim 15  wherein the step:
 b. electrolytically coating said intermediate steel wire with copper, iron and zinc; 
 is performed by the following substeps of:
 b1. electrolytically coating said intermediate wire with copper; 
 b2. electrolytically coating the copper coated intermediate wire with iron; and 
 b3. electrolytically coating the copper-iron coated intermediate wire with zinc. 
 
 
     
     
         17 . The method according to  claim 16  wherein the step:
 b2. electrolytic coating said copper coated intermediate steel wire with iron; 
 is performed in any one out of the group consisting of following electrolytic plating solutions:
 ferrous chloride solutions; 
 ferrous sulfate solutions; 
 ferrous ammonium sulfate solutions; 
 ferrous fluoroborate solutions; 
 ferrous sulfamate solutions; and 
 mixed sulfate—chloride baths. 
 
 
     
     
         18 . The method according to  claim 15  where in the step of:
 e. subjecting the intermediate steel wire with a brass coating enriched with iron particles to a wet wire drawing operation; 
 
       wet wire drawing is performed to a true elongation of at least 3.5. 
     
     
         19 . The method according to  claim 15  wherein the step of:
 e. subjecting the intermediates steel wire with a brass coating enriched with iron particles to a wet wire drawing operation; 
 
       wet wire drawing is performed by means of one or more dies comprising diamond.