Catalogue - Decarburization-free and soot-free batch annealing with automated atmosphere control. - RAD-CON



Decarburization-Free and Soot-Free Batch-Annealing with Automated Atmosphere Control

Decarburization-Free and Soot-Free Batch-Annealing with Automated Atmosphere Control

A new method of controlling a nitrogen/propylene furnace atmosphere was found to offer substantial and repeatable results annealing ferrous wire and wire rod. By Chris Messina, Arno Muennich and Robert Blumenthal (As presented on May 13^th at Interwire 2003)

foreward The article deals specifically with a new method of controlling a nitrogen/ propylene protective atmosphere for the annealing process. This new method uses a zirconium oxide sensor in conjunction with a proprietary algorithm in order to determine the optimum atmosphere flow settings. The proprietary algorithm, known as "Annealing Process Equilibrium", is hereafter referred to as "APEx". To understand the importance of APEx, it is necessary to know the historical development of the nitrogen/propylene atmosphere. The first half of the article describes the evolution of this atmosphere. The second half of the article details the APEx technology and gives some field results.	inert gas, the process relies on the dilution of decarburizing agents (O₂, H₂O, and CO₂). For end-uses that could not tolerate decarburized wire, high flows of high-purity nitrogen were necessary to keep the decarburization agent levels low. Further, the annealing equipment relied on atmosphere chamber integrity—a leaky furnace needed yet more nitrogen. Thus, the true cost of nitrogen began to reflect the desired product quality coupled with the condition of the annealing equipment. Since most generated gases retain reactive hydrocarbons that scavenge oxygen to prevent damaging of the work, additives to pure nitrogen soon became commonplace to provide this reactivity. Propylene became the most utilized because of its low cracking temperature and its relative low cost. (Since very little propylene is needed, the operational cost impact goes virtually unnoticed.) Thus, by adding a small amount of propylene, less nitrogen could be used for diluting since			the cracked propylene scavenges the oxygen and other decarburizing agents. How much propylene to use? The answer to this central question has remained elusive since propylene began being used as a replacement for generated gas. Too little propylene provides insufficient protection against decarburizing agents, but with too much propylene, soot deposits are left on the charge. Soot leads to cleaning and coating issues, and ultimately higher operating costs. traditional propylene control A typical plant will use predetermined gas flow rates to strive for a consistent atmosphere. The nitrogen and propylene flows are dictated by a predetermined recipe, and are coordinated with the temperature control events. Figure 1 shows a typical example.
*PART-I* background The necessity for a protective atmosphere during the annealing of steel is well known with various atmospheres available to processors. Historically, gas generators were typically used because high purity gases were not available at an affordable rate. Gas generators produce a background gas of mostly nitrogen, with a small hydrocarbon component. As bulk, high-purity nitrogen became affordable, and as maintenance staffs became leaner, gas generators began being replaced by delivered nitrogen. Processors soon realized that inert nitrogen alone could not replace generated gas for all applications. With a purely
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Decarburization-free and soot-free batch annealing with automated atmosphere control. - RAD-CON - #1

Sintering furnace, Software, Bell furnace, Process software, Annealing furnace