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.

Description

FIELD OF THE INVENTION[0001]The technology described herein relates generally to metal heat treating processes such as annealing, patenting, or tempering. More specifically, the technology described herein relates to a method and system to prevent iron oxide formation and decarburization during strand heat treating of a steel product without the required use of acid pickling. Additionally, this technology relates to 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.BACKGROUND OF THE INVENTION[0002]Patenting is a heat treatment process for a metal or alloy. Patenting is used to soften a steel metal or alloy and remove any existing brittleness. Control of both time and temperature during the patenting process is critical in order to achieve a final product with app...

AI Technical Summary

Benefits of technology

[0025]Advantageously, this technology provides a method and system to prevent iron oxide formation and decarburization during strand heat treating of a steel product without the required use of acid pickling. Additionally, this technology provides placing a coating, such as copper pyrophosphate electrolytic plating, to the surface of a steel wire prior to strand heat treating to avoid both the iron oxide formation and decarburization through the surface of the steel wire by preventing interactions between the steel wire and the furnace atmosphere.

Problems solved by technology

Pickling acids, such as concentrated hydrochloric acid, HCl, or sulfuric acid, H2SO4, are expensive and environmentally unfriendly.

Furthermore, such pickling acids create maintenance and health issues related to disposal, potential spills, and fumes.

When decarburization occurs, generally at the hot surface of the steel wire, and in the presence of water vapor resulting from combustion of gases like natural gas, the wire is unfit for subsequent conversion.

Additionally the wire may exhibit property degradation such as low strength, low fatigue life, and / or unsuitable draw ability.

It is also known that the rate of diffusion of copper into steel is slow, making it unlikely for copper-steel alloys to form at the surface of the wire.

However, copper is not known or used in the art as a “mask” to prevent carbon from leaving the surface of a steel part.

It is very difficult to control both the wire temperature and the furnace atmosphere; any shift in the furnace atmosphere will result in a change in the wire temperature.

Therefore, the gas-rich portion of the furnace shifts toward the furnace entrance, reducing the oxygen-rich zone and resulting in a decrease in convective heat transfer and a corresponding decrease in wire temperature.

Both of these furnaces, by definition, heat wire indirectly and are relatively energy inefficient.

In addition, cost to produce and maintain such a furnace atmosphere in a strand furnace, which is open at both ends, is prohibitively expensive.

These and other problems exist.

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