Consider the numerous systems in your heat treat operations. What makes up the anatomy of each furnace? In this "Anatomy of a Furnace" series, industry experts indicate the main features of a specific heat treatment system. For this inaugural feature, note how the schematics demonstrate how the tip-up furnace is able to process massive loads in an atmospheric sealed environment at highly controlled temperatures.
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Annotations for this furnace corpus were provided by Dan Herring, The Heat Treat Doctor®, The HERRING GROUP, Inc. A front view of a tip-up furnace as well as a back view of a different tip-up are provided along with the labels.
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This Technical Tuesday article is drawn from Heat Treat Today's February's Air & Atmosphere Furnace Systems print edition.
Heat Treat Today asked tip-up manufacturers to help heat treaters understand the variability of tip-up options in the market today. In this article, Gasbarre Thermal Processing Systems and Premier Furnace Specialists share unique approaches on how their own gargantuan furnaces serve heat treaters. As you read, note that customization is the critical component to operating a tip-up in your heat treat department.
This original content article is drawn from Heat Treat Today's February Air & Atmosphere Furnace Systemsprint edition. Have something to share about tip-up furnaces? Our editors would be interested in sharing it online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own ideas!
Gasbarre Thermal Processing Systems
What is your system and how does it differ from historic tip-up systems?
Gasbarre has a unique offering of tip-up style furnaces. We offer systems for conventional applications such as austenitizing, solution treating, stress relieving, and tempering. In addition, we also offer atmosphere processes such as annealing and ferritic nitrocarburizing (FNC). For us, tip-up systems are not one-size-fits-all type systems. Systems are designed around our customer’s specific processing requirements. This would include thermal process requirements, load geometry and weight, temperature ranges and uniformity requirements, as well as time to quench specifications.
What are its operational advantages?
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When evaluating a tip-up furnace system, they are typically compared against box-style furnaces and car bottom furnaces. So, what differentiates a tip-up from these other style furnaces? First, you can achieve the main goal of large capacity batch processing, while gaining advantages over box furnaces with wider temperature ranges and tighter uniformity requirements. Box furnaces are more challenging to evenly distribute heat due to the large space requirement for the furnace door, where it is difficult to include heating elements or gas fired burners. Second, you can achieve faster time-to-quench speeds in a tip-up furnace over a car bottom furnace. Car bottom furnaces require the load to be pulled out of the furnace and then the load is typically manually moved from the furnace hearth to the quench. In a tip-up, this process can be automated and completed in 60 seconds or less. Finally, when special atmosphere processes are required, a tip-up furnace offers a superior atmosphere seal to the other furnaces mentioned. With tip-up furnaces, you can seal the furnace using its own weight. Other furnaces require additional mechanical assemblies to achieve a proper seal, which ultimately is more susceptible to leaks and requires more maintenance than a tip-up furnace seal.
Tip-up furnace from Gasbarre Thermal Processing Systems Source: Gasbarre Thermal Processing Systems
Why should people be paying attention to what you have to offer?
Gasbarre’s broad product offering gives us the ability to evaluate your requirements objectively and offer the best solution for you and your company, whether that be box furnace, car bottom, or tip-up. Tip-up furnace systems are usually not one-off installations. These systems usually involve quenching equipment, material handling, load staging, and other integration. Gasbarre has the experience and personnel to manage such large projects and support the customer to effectively implement a system.
Premier Furnace Specialists
What is your system and how does it differ from historic tip-up systems?
The controls and automation capabilities of our furnaces set us above many older systems still in use today. On the control panel of an older system, you’re likely to see paper chart recorders, maybe a PanelView screen, and dozens of switches, pushbuttons, and pilot lights. Some of our customers prefer these control systems for their familiarity, and that’s fine because we are capable of building this style of enclosure, but most come to us for improvements or new systems entirely. Our standard panel comes with a 23.8” color touchscreen display that lets operators manage or record almost every aspect of the furnace’s operation. This package can be added to existing furnaces as well, as we have performed many control and combustion upgrades on older systems to keep them functional and reduce operating costs. We also offer tip-up furnaces that operate via jackscrews for customers who want to avoid the maintenance and flammability of hydraulics.
Open indirect gas-fired atmosphere furnace used to handle a variety of parts Source: Premier Furnace Specialists
Modern burner technology also offers a massive improvement over older systems. With rising energy costs for all fuel types, any increase in efficiency will quickly become a source of savings which can be redirected into other areas of your company. Improvements to burner design offer increased preheat, recuperative, and regenerative possibilities, which offer fuel savings across multiple temperature ranges and reduce emissions to keep in line with changing regulations. A standard burner can heat up and cool down faster, take less time to tune, and reduce maintenance hours and headaches compared to older models of burners with knowledgeable air and gas train design coupled with modern burners.
What are its operational advantages?
Our systems allow greater flexibility for integration with existing and future equipment as well as simplified operation. One of the largest complaints we hear in every industry is about the struggle to retain maintenance and equipment operators’ knowledge once a senior member leaves a company. For this reason, it is important to have a simplified controls interface that allows new operators to get up to speed quickly. As a service company as well as an OEM, we have extensive experience working on and upgrading many brands of equipment. This enables us to easily integrate our solutions to match what customers are familiar with while also reducing maintenance requirements.
Closed furnace with work chamber of approx 31' x 9' x 9' with load capacit of 90,000 lbs. Source: Premier Furnace Specialists
Why should people be paying attention to what you have to offer?
Despite OEMs trying to convince you, sometimes a standard “cookie cutter” model just isn’t the right fit for a job. It can take years to build up a budget for a new furnace system. Don’t invest those hard earned dollars into a piece of equipment that won’t do everything you need, exactly how you need it done. We are willing to take on the jobs that require creative solutions and extensive automation. Premier’s custom engineered systems live up to our namesake. Some of our recent projects have included a 130 ft long roller hearth furnace system with automated cooling/sequencing/handling of over 40 loads simultaneously; and a car bottom furnace with a 15’ x 15’ x 15’ work chamber capable of controlled heating and cooling of 160,000-pound loads.
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Are your brake rotors heat treated? Travel back in time to discover how ferritic nitrocarburizing (FNC) became the heat treatment of choice for automakers’ brake rotors and why the tip-up furnace forever altered the production process for this part.
This Technical Tuesday article is drawn from Heat Treat Today's February Air & Atmosphere Furnace Systems print edition.If you have any information of your own about heat treating brake rotors, our editors would be interested in sharing it online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own ideas!
The Problem: Brake Rotor Corrosion
Michael Mouilleseaux General Manager at Erie Steel, Ltd. Sourced from the author
In the early 2000s, corrosion was one of the top three issues that U.S. automotive manufacturers found negatively affected the perception of the quality of their cars. Brake rotors are made of cast iron. These components sit out in the elements, and in places like the U.S. Midwest where salt is often used on the roads, unprotected steel or iron will corrode or rust. Even on the coast, there is salt water in the air.
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What does rusting cause? The rotor rusts, and first, the cosmetics are negatively affected (i.e., rusty appearance). But more importantly, the first time you step on the brakes, it squeals like a pig, the vehicle shudders, and the driver feels pulsing in the pedal. He’ll also feel it in the steering wheel because the amount of rust coating one area is different from the amount of rust that’s on another. So, these brand new, forty- to seventy-thousand-dollar cars have orange rust over the brake rotor and a shaky drive. . . it’s not a good look!
Now, this is just a superficial coating of rust that will eventually abrade away; the rotor will look alright, the vehicle will stop better, and it won’t squeal. However, since the rust on the rotor wears off unevenly, the car may never have smooth braking.
A Move to FNC
In the early 2000s, all the big players were looking to FNC (ferritic nitrocarburizing) as a solution to corrosion, including Bosch Braking Systems, Ford, General Motors, Akebono, and the truck manufacturers. FNC was becoming popular since the process adds a metallurgical layer — called the “white layer” or “compound zone” — to the part, providing corrosion resistance and the bonus of improving wear.
Source: Oleksandr Delyk/Adobe Stock
To the OEMs, the benefits were perceived as:
The corrosion issue had an answer.
The life of the rotor doubled from roughly 40,000 to 80,000 miles. Although that meant half as many aftermarket brake jobs compared to before, consumers perceived it as a real advantage.
The rotors generated less dust. Brakes generate dust particles as the result of abrasion of the pads and the rotors. This particulate dust has been identified as both an environmental and a health concern. Now, flash forward to 2022: Electric vehicles are largely displacing the need to control emissions from ICE (internal combustion engine) vehicles. So, the new European standard on vehicle emissions implemented a requirement to control this dust that is harmful to the environment and which EV and traditional brake systems can emit.
But there were certain technical and practical challenges that automotive manufacturers faced when trying to implement this process at scale.
#1 Distortion. Brake rotors may distort during FNC. Since rotors are (gray iron) castings, the process temperature for FNC may stress relieve the rotor, causing it to change shape or distort, rendering it unusable as a disc brake rotor. It was determined that if the rotor castings were stress relieved prior to machining and FNC, the distortion issue was rendered moot.
#2 Loss of Necessary Friction. FNC gives the white layer on the surface of a part with a diffusion zone underneath. The compound zone has a very low coefficient of friction, which means excellent wear properties. However, manufacturers want friction between the rotor and the brake pads to slow the car down. Reducing the friction on the rotors extends the braking distance of the car.
". . .[M]anufacturers want friction between the rotor and the brake pads to slow the car down." Source: Unsplash.com/Craig MorolfLet me illustrate this: I ferritic nitrocarburized a set of brake discs for Bosch Braking Systems, which eventually went to Germany and then on a vehicle. The customer absolutely loved the corrosion resistance, but when it was time for the downhill brake test, the car went straight through an instrument house because the brakes couldn’t stop the car! Lesson: For rotors treated with FNC, the brake pads need to be made from a different frictional material!
#3 Cost. Overcoming the technical issues is simple. Stress relieving the casting at FNC temperatures before machining it would help the parts machine better and would eliminate distortion. Modifying the FNC process could reduce the depth of the white layer and, paired with the correct friction material, the acceptable braking capabilities were restored. Yet these additional steps presented a new challenge: higher costs.
The practical constraints of FNC in conventional batch or pit furnaces strained efforts to be cost-effective. The load (size) capacity of the conventional equipment, in conjunction with the time constraints of the FNC process presented a dilemma, as the OEMs’ benchmark was about one dollar per rotor.
Here Comes the Tip-Up
With traditional furnaces for FNC, there was just no way to reach the economics that were necessary for it. A bigger pit furnace might be the way to go, but they really weren’t big enough. So, here comes the tip-up.
Traditionally, a tip-up furnace has been used for processes with just air, no atmosphere. With direct fired burners, the furnace is used for tempering, stress relieving, annealing, and normalizing. Everything loads into the box, gets fired, and unloads, similar to a car-bottom furnace. With the appropriate external handling systems parts could be retrieved from the furnace and then quenched. This additional process increased the usefulness of the equipment and allowed for the processing of tubes, bars, big castings. . . big forgings for the oil industry and the like.
The question of how to heat treat brake rotors on a large scale still needed to be answered. It required a large, tightly sealed furnace with atmospheric integrity for excellent temperature uniformity. In ferritic nitrocarburizing, the processing range is about 950°F to 1050°F. It is well known that properties vary significantly across the temperature range. And they needed to be optimized to create the appropriate frictional properties for the rotors.
So, the answer was: Let’s make a tip-up furnace that can be sealed for atmospheric integrity, has the appropriate temperature uniformity, and can circulate gas evenly. A lot of this would have to be iterative — create, test, compare, repeat.
Tip-up furnace from Gasbarre Thermal Processing Systems Source: Gasbarre Thermal Processing Systems
The development of the perfect tip-up was essentially the work of one furnace manufacturer and one heat treater who together changed the industry.
American Knowhow Makes the Perfect Tip-Up
In the early 2000s, heat treaters worked with OEMs to develop a cost-efficient process in a tip-up. Manufacturers and service providers tested different methods, including atmosphere FNC and salt bath FNC.
By 2009, the perfect atmosphere furnace was complete and high volume brake rotors began to be processed for General Motors. The furnace manufacturer was JL Becker, Co., acquired by Gasbarre in 2011. The commercial heat treater was Woodworth, Inc., located in Flint, MI. Together, they spent a lot of time and money looking into FNC and figuring out how to make it work in a tip-up furnace.
General Motors was the first one to get on board, utilizing the FNC processed rotors on their pickup trucks and big SUVs, like the Escalade and Tahoe. Ford was not far behind using it on their F150 pickup truck. I was shocked the first time I saw the commercial: a Silverado pickup truck, out in the snow, and the speaker saying, “We now have an 80,000-mile brake system because of a heat treating process called FNC!”
It’s a great story of American knowhow and a collaborative effort between someone who saw a need and someone else who saw the way. To this day, if you want to get a replacement set of brake rotors for your car, go to a place like AutoZone; they will tell you that the difference in cost between the OEM parts and an off-brand is the fact that the off-brand is not heat treated.
About the author: Michael Mouilleseaux has been at Erie Steel, Ltd. in Toledo, OH, since 2006 with previous metallurgical experience at New Process Gear in Syracuse, NY, and as the Director of Technology in Marketing at FPM Heat Treating LLC in Elk Grove, IL. Having graduated from the University of Michigan with a degree in Metallurgical Engineering, Michael has proved his expertise in the fi eld of heat treat, co-presenting at the Heat Treat 2019 show and currently serving on the Board of Trustees at the Metal Treating Institute.
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