Methods and Systems for Preventing Iron Oxide Formulation and Decarburization During Steel Tempering

Abstract

The technology described herein provides a method and system to prevent iron oxide formation and decarburization during strand heat treating of a steel product without the subsequent required use of acid pickling, which has associated health and environmental risks. Additionally, this technology provides placing a coating, such as copper plating, to the surface of a steel wire prior to strand heat treating to avoid both iron oxide formation and decarburization through the surface of the steel wire by preventing interactions between the steel wire and the furnace atmosphere. To remove oxides formed by the plating metal, the oxides are chemically reduced by passing the steel wire through a reducing gas, electrolytically reduced by plating with the wire anodic, mechanically reduced through the use of brushes, or the like, or chemically reduced by acid pickling.

1 . A method to prevent iron oxide formation and decarburization during the patenting of steel wire, the method comprising:
 coating a steel wire with a metal plating prior to heat treating the steel wire and thereby masking the steel to prevent carbon from leaving a surface of the steel wire;   austenitizing the plated steel wire in a gas furnace, wherein the steel wire is protected against iron oxide formation and decarburization, which would otherwise occur as a result of exposure to the atmosphere of the furnace, because of the plating;   cooling, immediately, the austenitized and metal plated steel wire in a controlled cooling process environment;   reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace and;   cooling the steel wire to room temperature;   wherein the coating of the steel wire with the metal plating prior to heat treating prevents iron oxide formation and decarburization during the heat treating, without a required use of acid pickling.   
   
   
       2 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , wherein the coating used for metal plating a steel wire is an electrolytic copper pyrophosphate plating. 
   
   
       3 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , wherein the coating used for metal plating a steel wire is an electrolytic copper sulfate plating. 
   
   
       4 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 austenitizing the plated steel wire in a gas furnace to a temperature of 950° C. to 1050° C.   
   
   
       5 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 cooling the steel wire to within the range of 500° C. to 650° C.   
   
   
       6 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace by passing the steel wire through a reducing gas, wherein the reducing gas is hydrogen.   
   
   
       7 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace by passing the steel wire through a reducing gas, wherein the reducing gas is carbon monoxide.   
   
   
       8 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace by passing the steel wire through a reducing gas, wherein the reducing gas is a mixture of reducing gases.   
   
   
       9 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further compromising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace by a copper pyrophosphate electrolytic removal process.   
   
   
       10 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further compromising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace by a copper sulfate electrolytic removal process.   
   
   
       11 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace using acid pickling; and   rinsing with water the steel wire to remove the acid used in the acid pickling.   
   
   
       12 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace using mechanical descaling of the oxides with mechanical brushes.   
   
   
       13 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 plating, reversely, and after the cooling of the steel wire to room temperature, the oxides on the surface of the wire formed by the oxidation of the metal plating in the atmosphere of the furnace; and   reusing the plating to apply it to an unplated steel wire prior to its austenization.   
   
   
       14 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising:
 etching, lightly, subsequent to the reducing of oxides formed, with a mild acid solution, the steel wire to help improve subsequent electroplating.   
   
   
       15 . The method to prevent iron oxide formation and decarburization during steel tempering of  claim 1 , further comprising, prior to coating a steel wire with a metal plating:
 drawing the steel wire from a steel wire rod taken from a steel coil;   descaling the steel wire of any mill scale, or preexisting iron oxides used to prevent further oxidation during shipment; and   rinsing the steel wire to remove any extraneous debris from the surface of the wire.   
   
   
       16 . A system for preventing iron oxide formation and decarburization during steel tempering, the system comprising:
 a plating device for coating a steel wire with a metal plating prior to heat treating the steel wire and thereby masking the steel to prevent carbon from leaving a surface of the steel wire;   a patenting device for austenitizing the plated steel wire, wherein the steel wire is protected against iron oxide formation and decarburization, which would otherwise occur as a result of exposure to the atmosphere of the furnace, because of the plating;   a controlled cooling device for immediately cooling the austenitized and metal plated steel wire; and   a device for reducing oxides formed by the oxidation of the metal plating in the atmosphere of the furnace; and   wherein the coating of the steel wire with the metal plating prior to heat treating prevents iron oxide formation and decarburization during the heat treating, without a required use of electrolytic acid pickling.   
   
   
       17 . The system for preventing iron oxide formation and decarburization during steel tempering of  claim 16 , wherein the tempering device for austenitizing the plated steel wire is a direct-fired gas furnace. 
   
   
       18 . The system for preventing iron oxide formation and decarburization during steel tempering of  claim 17 , wherein the atmosphere of the furnace is optimized for heat transfer to improve energy efficiency. 
   
   
       19 . The system for preventing iron oxide formation and decarburization during steel tempering of  claim 16 , wherein the controlled cooling device, for immediately cooling the austenitized and metal plated steel wire, cools the steel wire to within the range of 500° C. to 650° C. in order to obtain a microstructure subsequent drawing for tire cord applications.