Vacuum is used to control the environment in many heat treatment processes and the vacuum pumping systems used may be simple or complex. This article offers practical recommendations to handle operational issues that can arise with these systems to optimize performance, reliability and safety.

The application of vacuum in industrial processes is widespread with the heat treating industry using vacuum in a broad range of processes, many of which place particular demands on the vacuum pumps. Today, there are many types of vacuum pumps available, from traditional oil-sealed rotary vane pumps to the so called “dry” pumps developed for use in the semiconductor industry, and which have found their way into industrial processes. By Dick Amos and Simon Bruce

Quenching is an integral part of any metal alloy heat treating application. It helps define the metal’s microstructure and is a critical step in determining whether a part will meet specifications and properties after tempering. Having a full understanding of the types of quenchants available and in what applications they are best used will improve a heat treater's overall operation.

Everyone who has ever seen a movie about medieval life is likely familiar with the image of a sweaty, soot-covered blacksmith pounding away with his hammer on a sword. When finished, he lifts the bright red, heated blade from the anvil and plunges it into a nearby bath. Most audiences probably think the water was meant just to cool the hot blade. But as any metallurgist or heat treater knows, the blacksmith was forging and heat treating the sword and using the water bath to quench it. By Michael Edens

Four, five, six, counting molecules is a job for vacuum gauges, and it’s now time to understand the differences between these devices and when to use them. Recall first that the vacuum level in a vessel is determined by the pressure differential between the evacuated volume and the surrounding atmosphere (Table 1). The two basic reference points in all these measurements are standard atmospheric pressure (760 torr) and perfect vacuum (0 torr), so calculating changes in volume in vacuum systems requires conversions to negative pressure (psig) or absolute pressure (psia). By Daniel Herring

New developments in welding and thermal processing are enabling the cost-effective use of martensitic stainless steels in exciting new applications. These advancements, coupled with an increased demand for high-strength, lightweight structures, are positioning martensitic stainless as an attractive alternative to costly high-alloy materials. Stainless, or corrosion-resistant, steels are defined as iron-based alloys with a minimum 10.5% chromium content, which promotes the development of an invisible, adherent and self-healing chromium-rich oxide surface film. Stainless steels are commonly divided into five groups classified by their microstructure at room temperature. By Daniel Codd, P.E.

Counting molecules is a job for vacuum gauges. Depending on the type of vacuum systems and the required operating vacuum level, different vacuum gauges are required, often in combination with one another, to accurately determine and/or control the vacuum level of the chamber at any given moment in time. By Daniel Herring

In this third and final installment, we will examine technological developments in vacuum heat treating and look to the future. Many new technologies owe their success to vacuum processing. Examples include; 1) Rotational compression brazing of aerospace rocket and military jet engines, 2) Titanium processing including beta annealing, slow cooling and age hardening (BASCA 160) of titanium alloys, 3) Vacuum carburizing/carbonitriding and high-pressure gas quenching of automotive powertrain components and 4) High-temperature sintering followed immediately by vacuum hardening for automotive transmission components. By Daniel Herring Read part One of three - Read part Two of three

To fully understand the advantages of heat-treating processes to manufacturing it is important to first understand a fundamental principal of metals – structure. As a molten metal solidifies, the atoms orient themselves into a repetitive pattern that we call a crystal structure. Body-centered cubic (BCC) and face-centered cubic (FCC) are two of the more common crystal structures. Elements such as Aluminum (Al), Chromium (Cr), Copper (Cu), Iron (Fe), Molybdenum (Mo), Nickel (Ni) and Silicon (Si) are a few examples of metals having these crystal structures. By Daniel Herring