Tag Archives: annealing furnace

A Brief History of the Heat Treat Oven

Necessity is the greatest catalyst for innovation. This was also the case with the invention of the heat treat oven. The more man’s ambitions developed, the more he needed specific tools to accomplish his goals. This is where the idea of the heat treat oven was born.

This journey began with the production of iron somewhere around the 2000 BCE in southern Asia. Iron was replacing bronze due to its strength and durability. At this crude stage open fires acted as the heat treat oven. The iron was heated, worked, heated, worked, and so on until it was ready to be cooled.

The concept of heat treating was one of universal birth. All over the world in different civilizations in Europe, Asia and the Middle East, metalworkers began to enclose the fire pits little by little as it was noticed that heat uniformity and heat retention had a substantial effect on the product and on the productivity of the worker.

As man’s dreams for iron implements became more and more specialized, so did the heat treating requirements. The heat treat oven became a tool for science and engineering.  Heat treating became more than just a means of creating a desired product; it became the science of learning to controlling metallic compositions and their properties.

3,000 Years later steel replaced iron and brought with it a myriad of possibilities. Steel was stronger, more flexible, and more durable than cast or wrought iron. That said, producing steel was also time-consuming, labor intensive and costly.

As the demand for steel grew with the railway boom, a new process emerged called the Bessemer Process. This process allowed high quality steel to be manufactured in minutes instead of days and while using less fuel and labor.

From these earliest heat treat ovens of the Iron Age to the creation of mass assembly lines, heat treating has touched all aspects of everyday life from railroads, pipelines, refineries, vehicles, infrastructure, buildings, bolts, nuts, washers and dryers, and tools of every kind.

The heat treat oven revolutionized the world by providing endless possibilities for the creation, development and use of metals.

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Curing Ovens – FAQs

What are Curing Ovens used for?

A Curing Oven is an industrial oven that is intended to create a chemical reaction in a material once a specific temperature is achieved. Definitions for curing offer different viewpoints on the process.  Engineering and Polymer Chemistry refer to curing as the process of increasing the strength and durability of a substance. The online dictionary describes curing as the preparing or finishing of a material by means of a physical or chemical process. However, for our purposes, Merriam-Webster’s dictionary has the most accurate description referring to curing as altering a substance by physical or chemical means for the purpose of preparing it for use. Curing allows the materials to be toughened by heating individual links of the material until they can be cross-linked together into a chain; like a chain of DNA.

What is commonly cured in Industrial Curing Ovens?

The primary function of Curing Ovens is to create polymers. A polymer can be hundreds, thousands or millions of molecules that have been linked together. Polymers can be combined to form more simple structures like a chain or more complex structures similar to DNA strands.

Polymer products are used in manufacturing for numerous different types of industries. Polymer categories include epoxies (strong adhesives), phenolics (a key ingredient in pharmaceutical drugs and detergents), polyesters (used to make bottles, films, and filters), and silicones (used in sealants, medical applications and many more).

Another curing process performed in a curing oven is powder coating. Powder coating is a process of painting where the powdered molecules are heated to the point of bonding with each other and are able to completely coat the desired surface. The outcome of powder coating is that the surface has essentially been painted without the use of liquid. Powder coating is preferred above painting with liquid paints because they do not contain contaminants and the paint has a much longer lifespan. The practice of curing the aforementioned materials is essential for the manufacturing process. The curing process, in its most basic description, is taking the raw material, heating it to build a substance that can be made into something useful.

What to look for in a purchasing quality Curing Ovens:

The most important aspect of a curing oven is heat uniformity. Ideally, the goal is to obtain plus or minus 5° (F), but on the larger ovens plus/minus 10° is optimal. This level of uniformity is achieved by calculating the right amount of air changes per minute based on fan speed and cubic feet per minute. The larger the curing oven depth is the more fans are required. Uniformity is optimized further by engineering the flow of air through the sides and up through the vents.

For more information on obtaining optimal uniformity for a curing oven, see our previous post “7 Questions to Ask Before Buying a Car Bottom Furnace”

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Post Weld Heat Treating

Post Weld Heat Treatment (PWHT) is another term for relieving the stress from a material and allowing it to return to its original state. The stress relief process involves diminishing and redistributing the small folds and cracks (called stresses) in the metal that are created during the welding process.

Post Weld Heat Treatment is an essential practice in order to repair the macro structure of the welded material. The primary benefits of this process include the removal of hydrogen (which can cause cracking), increased ductile strength, and increased resistance to corrosion. The process of post weld heat treating includes relaxing and soaking the materials. While there is no universal rule for the temperature and length of time for these processes, the most commonly used formula prescribes a 1 hour soaking period at peak temperature per 1 inch (25mm) of thickness for each joint.

The stress relieving process can be performed in many different types of heat treating furnaces. The type of furnace required for post weld heat treatment can be a gas or electric furnace, the temperature ranges can vary greatly, and can be equipped with or without fans. Each of these options depends on the type of the material being heat treated, the desired outcome, and the specific process that is being performed.

The Post Welding Heat Treating process is a vital procedure for certain metals in order to maintain specific thicknesses or grades of quality. In some cases, heat treating can be detrimental to the welded metal if the procedure is not performed correctly, causing mechanism failure and corrosion. Steel is a metal that is often mishandled more than others and must be cared for properly. The tempering or aging process can cause the mechanical properties of the steel to deteriorate. Quenched and tempered steels, for instance, must be post weld heat treated at a lower temperature than the original tempering occurred at in order to preserve the natural strength and micro-structure qualities.

If you have more questions about the Post Weld Heat Treating process or PWHT Furnaces, contact us at Baker Furnace. Our on-staff industry experts are always available to assist you.

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7 Questions to Ask Before Buying a Car Bottom Furnace

Purchasing a Car Bottom Furnace is a large undertaking with many variables and expenses to consider.  We’ve compiled a few common questions that always come up as we work with our customers to build them the best quality car bottom furnace.

Here are some important questions to ask before you purchase a Car Bottom Furnace.

1. What is a typical Temperature Uniformity Specification for a Direct Fired Car Bottom Furnace?  A Car Bottom Furnace typically operates at plus or minus 25 degrees F uniformity inside the furnace’s “working space”. Tighter uniformity ( plus or minus 10 degrees F) has been achieved on some of our direct-fired units. Temperatures typically are in the 1350 degree F range.

 2. Does the Car Bottom Furnace  have pressure controlled Flue Dampers and what is the benefit?  A Car Bottom Furnace should utilize pressure transducers and a control motor/linkage that adjusts the flue. These pressure controlled flues ensure excellent furnace uniformity.

3. What temperatures can I achieve inside the Furnace?  Generally, a Car Bottom Furnace operates from 1000 degrees F up to 2200 degrees F.  High quality manufacturers should insulate the furnace with a combination of Ceramic Fiber and, Castable Refractory and Heavy Duty Refractory brick.  Linings as thick as 12” thick are used on 2200 degree F units.

4. Is the Car sealed to the side and back walls when inside the Furnace?  A Car Bottom Furnace should utilize some type of “bumper” system that thoroughly “seals” the car inside the furnace.  The drive Mechanism for the Car is located beneath the Car shielded by the Refractory surfaces.

5. Is the Control Panel approved by an accredited Agency?  Any good manufacturer will be accredited by the U.L. The U.L. is an independent, global accredited safety science company aimed at maintaining s high standard of safety in the workplace and quality of the product being manufactured. Control Panels have a U.L. Classified Sticker affixed inside. All components in the U.L. Classified Control Panel are U.L. listed or recognized.

6. Is the Combustion System rated to meet Factory Mutual, IRI and NFPA 86?  A Car Bottom Furnace should include numerous safety components including redundant Gas safety shut off valves, Isolation gas cocks, High/Low Gas Pressure Switches, Air Proving switches and flame supervision with Ultra Violet (U.V.) Scanners.  Burners should not light until a purge air cycle has been completed at start up. The burners light on low fire and modulate safely to high fire via linkage and drive component.

7. Can I receive Installation/Start up assistance with my order for a Car Bottom Furnace?  A standard Car Bottom Furnace should be supplied with detailed general arrangement drawings as well as track installation drawings.  Baker Furnace has engineers on staff who assist on site with the installation and start up of your furnace.

 Car Bottom Furnace

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Depending on your requirements, there are several other questions that may come up, but we hope this helps you in your initial stages.  If you need more information, check out our Car Bottom Furnace presentation here:  BAKER FURNACE CAR BOTTOM FURNACE LINK