Technical Papers
 Steam Treating: Enhancing the Surface Properties
of Metal Components
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
Steam treating is the controlled oxidation of metals to produce a thin layer of oxide on the surface of a component. This process can be used to provide a component with increased corrosion resistance, better wear resistance, increased surface hardness, an attractive surface finish and, in the case of porous materials such as powder metal, seal the part porosity and increase the density.
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 Gassing Up To Get The Right Atmosphere
Akin Malas
BOC Gases, A Linde Group Company
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
In a continuous sintering furnace, one of the most important variables in achieving a successful process is control of the atmosphere. From the initial installation and start-up of the furnace to its maintenance throughout its life cycle, the process atmosphere demands an attentive eye in order to produce powder metal parts that are well sintered, meet the specification and have no defects. Starting with the source of the atmosphere gases and working through the components of the furnace, the atmosphere integrity must be verified before any parts can be processed. As the furnace ages, issues will arise that affect the integrity of the atmosphere and ultimately the quality of the product. Continual preventative maintenance and troubleshooting techniques will maintain the integrity of the process atmosphere. An understanding of the causes, diagnostic techniques and solutions to the many atmosphere problems that may compromise the atmosphere integrity, will enable a furnace operator to run an efficient and profitable process.
This paper focuses on the important parameters of the furnace and its atmosphere that affect the integrity of the sintering process, and gives guidance on how to approach and solve the problems they may cause.
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 Advances in Powder Metal Sintering Technology
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
The traditional powder metal process, often referred to as “press and sinter”, is constantly driven to change by an industry goal of entering new markets through substitution and the development of innovative products for new applications. Although much advancement has been made in the area of compaction, new materials and sintering technology continue to broaden the applications and improve the overall quality and competitiveness of powder metal components.
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A Review of the Fundamentals of Stainless Steel Brazing in
Continuous Style, Controlled Atmosphere Brazing Furnaces
Stephen L. Feldbauer, Ph.D.
 Abbott Furnace Company
The use of continuous style, controlled atmosphere brazing furnaces to braze stainless steels is becoming more common as the aerospace and automotive producers increase the use of stainless steel components on existing designs and explore new designs. Although much of the metallurgy and thermodynamics of Iron, Chrome, Nickel and their compounds are well understood, a review of the application of the fundamentals to the current practices and equipment technology can help with improved product quality, expanded applications, and the optimization of costs for a net improvement in competitiveness.
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 Paste or Preforms, the Brazer’s Question
Ken Allen
Bellman-Melcor, Inc.
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
There is a spirited debate among manufacturers involved in copper brazing in controlled atmosphere furnaces. Which form of filler metal is better to use; paste or preforms? This paper addresses the relative advantages and limitations of paste and performs.
Furnace brazing differs from hand brazing and many types of open air brazing in that the filler metal must be pre-placed on the part. Furnace brazing is done in a controlled atmosphere brazing furnace. This furnace type uses a stainless steel mesh belt that carries the product through a heated muffle containing the furnace atmosphere. The furnace atmosphere is typically neutral to reducing in nature. The atmosphere in the furnace usually contains significant amounts of Hydrogen and Nitrogen that allow high temperature brazing to be accomplished without oxidation or minimal to no flux.
A copper braze paste consists of copper powder blended into a neutral suspending agent. The product is a semi-solid consistency, somewhat similar to toothpaste.
A preform is a solid piece of copper (or any braze alloy) that has been pre-engineered to provide an exact volume and shape to accommodate a particular part or application. Preforms made from wire include rings, ring segments, wire segments, and four-slide fabrications of limitless geometries. Preforms manufactured from flat stock include washers, shims, and a wide variety of stamped configurations.
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 Stainless Steel Brazing
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
Atmosphere integrity and control are key to the successful brazing of stainless steel components. Due to the very high affinity that stainless has for Oxygen at high temperatures, the presence of Oxygen or moisture in the furnace will oxidize the surfaces to be brazed and result in a defective braze. Vacuum furnaces and Humpback furnaces have been the traditional systems used to braze stainless steel because of their ability to ensure an Oxygen-free atmosphere with a very low dew point. However, both furnace technologies bring with them issues that result in higher operational costs, increased maintenance costs, and other process related costs that can be avoided by using straight through continuous belt furnace technology.
Recent advances in furnace design and atmosphere control have made it possible for stainless steel to be brazed in straight through continuous belt furnaces. This step forward in technology now permits continuous processing at lower operational costs, less maintenance and higher yields than realized with traditional brazing systems. Oxygen levels of less than 10 ppm and dew points as low as –85ºF are common in a state-of-the-art straight through continuous belt brazing furnace. The adoption of this technology by some of the leading producers of brazed components is allowing the industry to become more competitive.
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 Troubleshooting Continuous Controlled Atmosphere Brazing Furnaces
Stephen L. Feldbauer, Ph.D.
Abbott Furnace Company
Controlled atmosphere brazing furnaces of the continuous type are some of the most common furnaces used in brazing. The goal of a brazing furnace is to provide a time, temperature, atmosphere relationship that is accurate, repeatable and economical in meeting the requirements of the brazing process. Although the general operation of this equipment is fairly straight forward, the troubleshooting that can often accompany a brazing issue can be frustrating.
This paper provides a step-by-step methodical approach for troubleshooting the furnace and identifies what steps need to be taken to address any problems.
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