Furnace Operation

Basic Vacuum Practice by Varian

Basic vacuum practices, a primer and basic introduction for vacuum technicians

Read More

Understanding Emissivity and Thermocouple Test Blocks

A recent process development test relating to carburizing illustrated the need to better understand the effect of surface emissivity and the proper use of dummy thermocouple test blocks. The testing involved carburizing areas of a partially copper plated alloy steel part. The copper plating covered areas of the part that were not to be carburized. Since the configuration of the part made it impossible to place a thermocouple within the part, a dummy test block made of carbon steel with the approximate same cross-section was used for the process thermocouple without proper consideration of the surface condition of the test block. Using the test block as the control, carburizing was initiated at the proper temperature based on the test block having reached that temperature. At the completion of the test, the part was examined for carburizing results and found in the non-copper plated areas, the depth of the carburized case to be shallow. This indicated that the cycle performed did not initially hold the part long enough at the correct temperature prior to carburizing. This resulted in the conclusion that when using dummy test blocks for controlling process times and temperatures, many factors must be considered including surface emissivity.

Read More

Technical Considerations for the Use of Carbon and Carbon Composite Materials for Fixtures and Grids

Advanced material solutions for fixtures, grids and internal furnace components are available today. They are designed to allow for higher processing temperatures, larger loads, increased production rates, energy savings, and lower overall cycle costs.

Read More

Operating A Vacuum Furnace Under Humid Conditions

A specific concern to a vacuum furnace user is processing critical work during summer months with high temperatures and high humidity. This same concern could also be a problem on rainy winter months. Under these difficult conditions, it is most important to understand the impact that humid conditions can have on the final surface condition and appearance of the processed parts. Work discolored or oxidized by residual water vapor is unacceptable and must be controlled for many critical components like aerospace parts or medical implants and instruments. This paper will try to explain factors relating to humidity, air temperature, and methods to improve final product appearance and minimize possibility of contamination.

Read More

Understanding PID Temperature Control As Applied To Vacuum Furnace Performance

Proportional-Integral-Derivative (PID) control is the most common control type algorithm used and accepted in the furnace industry. These popular controllers are used because of their robust performance in a wide range of operating conditions and because of their simplicity of function once understood by the processing operator. The purpose of this paper is to further define and thoroughly explain the basics of the PID controller. It should be noted that many current instruments incorporate what is called an “Autotune” feature which can automatically set the PID variables for a given temperature setting allowing the operator to bypass much of the initial manual requirements. However, Autotuning was not introduced until the late 1980’s and there still exists many instruments in use which do not have this tuning feature and must still be manually set-up. Also, Autotuning often requires additional tuning or tweaking to reach final acceptable results. By understanding fully the basics of the PID functions as described below, it is hoped that any final adjustments or tuning will be simplified. Further discussion of the Autotune feature follows below. As the name suggests, the PID algorithm consists of three basic components: proportional, integral and derivative which are varied to get optimal response. If we were to observe the temperature of the furnace during a heating cycle it would be rare to find the temperature reading to be exactly at set point temperature. The temperature would vary above and below the set point most of the time. What we are concerned about is the rate and amount of variation. This is where PID is applied.

Read More

Optimizing Procedures For Temperature Uniformity Surveying For Vacuum Furnaces

A Temperature Uniformity Survey ( TUS ) for a vacuum furnace to satisfy AMS 2750D must be performed using established procedures and methods that fully meet the requirements of the specification and allows for consistent and more accurate results of actual furnace capabilities. Solar Atmospheres and Solar Manufacturing, with their extensive vacuum furnace experience and processing knowledge, have combined to create a standard procedure for TUS for all newly manufactured and current in-production vacuum furnaces. This procedure considers the many critical aspects of AMS 2750D that must be fully satisfied to produce acceptable processing results and the following outline could be applied to any vacuum furnace user to satisfy their TUS requirements.

Read More

High-Pressure Gas Cooling: the Case for Hydrogen

Hydrogen’s cooling power makes it an attractive higher performance alternative to nitrogen as a quenching gas, particularly in light of escalating price of helium. However, safety issues must be resolved before heat treaters will adopt it.

Read More

Adding High Velocity to High Pressure Gas Quenching

When gas quenching, the minimizing of heat treat distortion is gears may be a matter of high pressure and high velocity. That’s what Solar Atmospheres thinks, that’s why the heat treat company sends helium gas into its vacuum furnaces at more than 100mph.

Read More

High Gas Velocity: A New Frontier of Cooling Performance in Vacuum Furnaces

Because there are diminishing returns in cooling capacity by simply increasing quench-gas pressure, increasing gas velocity might be the answer to the problem.

Read More