Category Archives: Induction Heating

The 4 Benchmarks of Good High Temp Insulation


Posted by Avery Webster

High temperature thermal insulation requires using the most current manufacturing processes and a high level of specificity in every aspect of production. If you are a manufacturer or purchaser of thermal insulation products, including blankets, boards, modules, papers, ropes, felts or any other variety, it’s crucial to understand what makes for a quality insulation product. These are the six most crucial aspects.

Conductivity
Both heat and thermal conductivity are important parts of the process. Thermal conductivity is a measure of a material’s ability to transfer heat energy through its mass. When a material has a low thermal conductivity, it will be a good insulator. Heat conduction occurs when vibrating molecules bump into each other and transfer heat from one to another. The arrangement and type of fiber used in insulation will determine its heat conductivity, which should also be low.

Conduction can also occur through a convective process, though this requires a medium such as liquid or gas to carry heat from one surface to another. Small pore size in ceramic fiber insulation reduces the occurrence of meaningful convection to provide a more efficient insulation.

Radiation cannot be ignored as a form of head transfer either. It is the primary mode of heat transfer at high temperatures seen in industrial processes. Ceramic insulation is the most efficient way to block radiation because it disrupts the electromagnetic wave that transfer the energy.

Shot
Shot is the unfiberized material left after the spinning or blowing method used to convert molten glass into ceramic insulation. Although these processes are generally efficient, they always leave some shot. This is expressed in the “fiber index” of material, which is a measurement of the weight of the fiber and can tell how much shot, which is heavier, is still included in a mass of insulation. More shot will mean a higher level of conductivity, but can still be appropriate for some lower temp applications.

Shrinkage
Just like any fibrous material (think about a favorite t-shirt that spends too long in the dryer!) ceramic insulation will shrink with continual exposure to high temperatures. Fortunately, most of this shrinkage occurs in the first 24 hours of heat exposure and is fairly easy to control for on the manufacturing side.

Environmental Factors
Ambient temperature, external wind speed, emissivity and hydrogen content all play an undeniable role in the performance of ceramic insulation. Speak to your supplier about the conditions your insulation will be under to determine appropriate products and manufacturing methods are being used.


Induction Hardening Depth – Some Basic Principles


Posted by Staff

As an engineer is designing a part to be used for a purpose, they must take many things into consideration. One consideration may be the properties of hardness desired. As they design a piece they may realize that there is surface area that will be subject to wear or abrasion, but the engineer may not be 100% certain of the heat treat properties they desire.

So, the engineer might call out the heat treat characteristic as needing a higher surface hardness but with few other details. Or, perhaps it is wear surface but also important for strength. This requires additional consideration beyond just the surface hardness; the depth is also important. With some of the information potentially missing or perhaps incomplete, an engineer will often wonder “how deep can we go?”

The depth of hardness is most dependant on material chemistry, with a few other factors also that need to be considered. The depth of hardness or hardenability of the material is determined for different material using the Jominy Test.

For example certain alloys of material are ideal for shallower depths but harder surfaces. Typically low alloy but high carbon materials will be suitable for such applications. Other material will allow much deeper case depth to be achieved and will typically have both higher carbon content as well as other alloying agents.

The hardness of the depth can also be affected by part geometry. Features such as shoulder or holes that result in thin wall areas will be affected differently than straight wall shafts. A hollow tube may harden deeper or even through harden compared to solid shaft of the same dimensions.

A quality induction hardening provider can help answer the question “How deep can we go?” via industry expertise, listening and learning about your application and by utiliozing published industry data.