What is Heat Treatment?: A Guide to the Types & Benefits of Heat Treatment

February 11, 2019

Long before our modern metalworking techniques, craftsmen relied on heat to make their materials workable. No matter how long it took, or how complicated the process was, once those heated metals were formed into the necessary shapes, they were then cooled, either rapidly or slowly depending on the goals of the blacksmith. But just like today, the quicker the metals were cooled, the harder they would become – and vice versa for slow-cooled metals.

Of course, after decades of industrial refinement, today’s heat-treating techniques are much more sophisticated, allowing for highly impressive levels of precision and swiftness, regardless of whether you’re working with nickel, aluminum, incoloy, or any number of other materials.

In this blog, we’re going to break down each of the heat treating services we implement in our own facilities to give you a better idea of how modern heat treating works, why it’s done, and how different techniques are used to create metals of varying strengths, elasticities, shapes, and even colors.

Let’s get to work!

The Stress Relieving Procedure

In the majority of cases, the stress relieving procedure is an essential part of the overall heat treatment process. That’s because the manufacturing and fabrication processes will often cause a build-up of stress in materials. Too much stress can cause deformities in the materials, leading to unwanted stretching, compression, and various other types of strain that can inadvertently alter a material’s dimensions. So, to prevent these unwanted dimension changes from accidentally occurring, the stress relieving procedure is done on various parts to reduce internal stress.

The typical stress relieving heat treatment process involves heating your components to an appropriate temperature, then holding them there long enough for the entire part to reach this temperature. Doing this allows all of the part’s stresses to be relieved, leaving you with a much more resilient part that’s much less prone to dimensional distortion. The materials that benefit the most from the stress relieving heat treatment process are ones with tighter tolerances, larger weldments, or ones that have undergone a significant amount of stock removal.

The Annealing Procedure

Annealing is another popular heat treating method, which is used to prepare various materials for the manufacturing process. Whenever a metal is annealed, it’s heated to the ideal temperature, then kept there long enough for re-crystallization to occur. Arguably, the most important part of the entire annealing process is the cooldown, which must be done at a very slow, very controlled rate to achieve the desired effect.

The main reason a product undergoes annealing is to reduce its hardness so it can be machined with greater ease. However, sometimes metals are softened up to increase their electrical conductivity, to restore their ductility, or to make them softer and therefore more reactive to cold working.

The Tempering Procedure

In most instances, tempering is done to improve the fortitude of an iron alloy so it can hold up during more intensive processing procedures. One of the defining characteristics of tempering is that it requires the alloy to be heated to a temperature below the critical melting point, but this temperature could range dramatically depending on the alloy you’re working with. For example, it could go as low as 400 degrees, or as high as 1,300 degrees, all depending on the particular materials you’re working with. Regardless of the temperature, however, the alloy is always then cooled by air.

Even more interesting is the fact that tempering will affect the color of your materials based on the amount of heat to which they are exposed, and metal workers will often use different colors to identify when the tempering process should be finished. Anything from light yellow, purple, brown, or various shades of blue can be used to indicate when the heated properties are finished. As a general rule of thumb, the deeper the color, the higher the temperature at which the material was tempered. After finishing the tempering process, the alloy is now much easier to shape, cut, and file, a critical component of the manufacturing process.

The Precipitation Hardening Procedure

Precipitation hardening – otherwise known as “age hardening” or even “particle hardening” – is a heat treatment method used to increase both the hardness and the yield of certain materials. It’s also one of the most popular techniques for strengthening materials.

With precipitation hardening, the treated parts are first machined in soft conditions before being hardened at relatively low temperatures. Different strengths and conditions can be achieved by altering the timing and temperatures of the precipitation-hardening treatments, but the end result is always the same: a stronger, harder material.

Indeed, the overall duration of the process can vary quite drastically, ranging in time from one hour to several; it all depends on the characteristics of the materials you’re working with. Nickel, magnesium, titanium, aluminum, and stainless steels are all good candidates for this sort of treatment, as are certain hybrids such as aluminum-copper, copper-tin, magnesium-aluminum, and so on.

The Hydrogen Bakeout Procedure

The hydrogen bakeout process involves heating up your steel, then giving it plenty of time for the molecular hydrogen to diffuse out of the steel, leaving it much more susceptible to welding than it was before.

Interestingly, however, there are no industry-wide standards or regulations for the exact times and temperatures required to bake out enough hydrogen in any given material. Naturally, this can be a cause of confusion in some cases, but at Globe LLC, we have our set of own rules related to hydrogen baking. Still, even these are flexible based upon the exact needs of a particular job or task, as well as the type of material that’s being worked on.

Want the Benefits of Heat Treatment for Your Most Valuable Materials?

Don’t just send your million-dollar part to anyone! To experience the full benefits of heat treatment, send it to someone with the experience and knowledge to provide you with top-quality heat treating services.

Here at Globe LLC, each and every part is professionally supported on a state-of-the-art furnace. We use tightly calibrated Honeywell Controllers & Recorders, and our furnace has an upgraded Allen Bradley processor for guaranteed ramp cycles and temperatures. All components have attached certified thermocouples that measure the part throughout during the entire heat treat process. For our clients, this means you’ll always get strong, well-crafted materials possessing the ideal properties for whatever applications they’re needed for.

With 30+ years of experience, your job will be done right at Globe LLC. Contact us today to discuss your needs, or learn more about our various heat treating services, our company history, or our other custom pipe fabrication services.