We continue our discussion on the factors that must go into the decision making process during the acquisition phase of a vacuum furnace. Part One focused on how one goes about choosing the right furnace for the job and talked about the various choices for hot zones (e.g. insulation, heating elements, etc.). Part Two discussed pumping systems, controls and ancillary support items (e.g., grids/baskets/fixtures, water systems, features & options). It is now time to understand how your supplier partner will handle the project once an order is received, including project management, codes & standards, approvals, installation, commissioning and long-term support.

Order Processing; Okay, you have selected a vendor partner to supply your vacuum furnace, so what type of support should you now expect? To begin with, it is important to understand how your order will be handled internally by the company you have selected. The first task they face is to transfer the order from their sales team to their engineering team and, ultimately, to the manufacturing and service/support teams. After receipt of an order, your supplier partner will typically schedule an engineering “kickoff” meeting where the project is given to engineering and a project manager (or project engineer) is assigned. Out of that meeting will be generated the final equipment specification and this should be provided to the purchaser shortly (e.g., 1 – 2 weeks) after receipt of the purchase order for approval. By Dan Herring

Tips for Selecting Vacuum Furnace Equipment – Part One

Tips for Selecting Vacuum Furnace Equipment – Part Two

The interlamellar spacing of pearlite is a very important microstructural parameter for steels containing pearlite, and becomes more important as the pearlite content increases towards a fully pearlitic microstructure. As the amount of pearlite in ferrite-pearlite microstructures increase, so does the strength, but toughness and ductility decrease. For a fully pearlitic steel, as the interlamellar spacing becomes finer, strength, toughness and ductility all increase. Consequently, in structure-property correlations it is important to measure the interlamellar spacing. This paper reviews procedures for performing such measurements. Due to the fineness of the spacing, either SEM images or TEM images of replicas or thin foils can be utilized. The range of spacings in a given specimen will be much narrower if the pearlite in the steel was formed isothermally rather than transformed over a range of temperatures, as in as-rolled or normalized steels. By George Vander Voort

CLICK ON LINK BELOW TO DOWNLOAD PDF OF THE DOCUMENT VAC AERO – PURCHASE ORDER TERMS AND CONDITIONS – April 1, 2015

Even as turbomolecular vacuum pumps have displaced most small laboratory sized oil diffusion pumps these days because of perceived ease of use and cleanliness, most high vacuum heat treating furnaces still rely on a large oil diffusion pumps to generate the pressures below about 10^-3 Torr needed for many metal conditioning processes.

The main reason for this is that turbomolecular vacuum pumps have a physical size limit due to the high rotational speed of the rotor. That size limit is around 320 mm or 13 inches inlet diameter and may vary a small amount from manufacturer to manufacturer. In many cases the pumping speed may not be high enough as it is directly related to the inlet size of the pump. Metal can disintegrate at very high speed, so the tip speed of the rotor blades has to be within the safe limit. Turbomolecular pump rotors have to move faster than the speed of the gas molecules they are pumping in order that the rotor blades can deflect the gas molecules downwards in the pump mechanism. The second reason that turbomolecular pumps are not used in many metal treating systems is they cannot tolerate any particulate matter entering them. They must only be used on clean vacuum systems. By Howard Tring

A number of brazing shops today combine brazing and heat-treatment in their vacuum furnaces to join components together and then obtain certain desired base-metal properties in those brazed components via rapid cooling (quenching) immediately after brazing is done, and before the components are removed from the furnace. Thus, the same vacuum-furnace brazing cycle combines brazing and heat-treatment, yielding clean brazed components with special base-metal properties to meet unique end-use service conditions.

Vacuum furnaces today offer a number of options regarding the introduction and use of circulating gases in the furnace hot-zone during brazing processes. Gases typically introduced into the vacuum furnace are either argon or nitrogen, but a number of shops have found success with hydrogen and helium gases as well. Often gases are combined rather than just using one gas. Hydrogen/nitrogen and helium/nitrogen are typical combinations used in some brazing shops. by Dan Kay

We continue our discussion on the many factors that must go into the decision making process during the acquisition phase of a vacuum furnace. Part One focused on how one goes about choosing the right furnace for the job and talked about the various choices for hot zones (e.g. insulation, heating elements, etc.).

 We now continue this discussion by looking at other common vacuum furnace features and options. Recall that the four common elements of any vacuum furnace are; Hot zone (c.f. Part One), Heating elements (c.f. Part One), Pumps and Controls. Once decisions have been made in these areas, other ancillary items (e.g. partial pressure control, loaders, etc.) must also be considered and will be talked about here as well. By Dan Herring

Tips for Selecting Vacuum Furnace Equipment – Part One

Tips for Selecting Vacuum Furnace Equipment – Part Three

The reflected light microscope is the most commonly used tool for the study of the microstructure of metals. It has long been recognized that the microstructure of metals and alloys has a profound influence on many of their properties. Mechanical properties (strength, toughness, ductility, etc.) are influenced much more than physical properties (many are insensitive to microstructure).

The structure of metals and alloys can be viewed at a wide range of levels – macrostructure, microstructure, and ultra-microstructure. Microstructural examination should always begin with the light microscope progressing from low magnifications to higher magnifications, followed by the use of electron instruments, as needed. In the study of microstructure, the metallographer determines what phases or constituents are present, their relative amounts, and their size, spacing, morphology and arrangement. The microstructure is established based upon the chemical composition of the alloy and the processing steps. A small specimen is cut from a larger mass (for example: a casting, forging, rolled bar, plate, sheet, or wire) for evaluation. By George Vander Voort

Burlington, Ontario, February 16, 2015 – VAC AERO has recently received orders for three complete all-metal hot zone refurbishments for customers in Florida, Connecticut and Indiana, in the Aerospace, Medical and Commercial Heat Treatment industry sectors. The retrofit work is for two horizontal and one vertical furnace. VAC AERO hot zones feature unitized construction for easy removal and maintenance. The lightweight design’s low thermal mass enables faster quenching and longer life. The heat shield package consists of one layer of .020” thick lanthanted molybdenum (Mola) sheet backed by one layer of .010” thick molybdenum sheet, and three layers of .014” stainless steel sheet. The heat shield package is supported by a 14 gauge stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload. Built for rugged usage and low maintenance VAC AERO hot zones feature unitized construction for easy removal and maintenance.

When a vacuum system is designed it is often necessary to select a mechanical vacuum pump or pump set that will evacuate the chamber and associated piping in a certain amount of time. In laboratory or research situations that may not be as necessary as in a production environment where the time to complete a process has quite a lot to do with the cost of the manufactured part.

In addition, the cost of the vacuum system has to be taken into consideration as well. Larger pumps may reduce the evacuation time, but also are more expensive. There has to be a balance between all the parameters. There are two simple methods for calculating evacuation time; one for a rotary vacuum pump, vane or piston, on its own, and a second for larger volumes when a vacuum booster pump may be used. Both methods give good results for simple vacuum systems where the mechanical vacuum pumps are located close to the chamber and the chamber is relatively empty. By Howard Tring 

Acquisition of a vacuum furnace represents a major capital equipment investment and one that creates a long-term relationship with your supplier partner. Thus the choice of what to buy and who to purchase it from requires careful planning and considerable up-front research.

You need to know when and how to apply vacuum technology, if it will be the most cost effective solution for what you need to do, what questions to ask and what information to provide. The process begins by understanding your specific needs and asking all the right questions. Is it more prudent to upgrade an older piece of equipment, purchase new or purchase used? Is it better to have one large furnace or two smaller ones? Is a batch solution best or is a continuous approach better? By Dan Herring

Tips for Selecting Vacuum Furnace Equipment – Part Two

Tips for Selecting Vacuum Furnace Equipment – Part Three