Heat treat equipment upgrades were included in the investments made at a global industrial solutions company that produces fasteners and fastening assemblies.
A. Raymond Tinnerman, based in Brunswick, Ohio, has seen significant upgrades and additions to its Logansport, Indiana, facility, which includes the rebuild of the heat treating processes and the addition of an endothermic generator.
Mark Schahczinski, Sales Engineer, Wisconsin Oven Corporation
A metal treating company based in Raleigh, North Carolina, recently purchased five electrically heated standard draw batch (SDB) series furnaces to be used for stress relieving at its facility.
East Carolina Metal Treating received shipment of the equipment, which have maximum operating temperatures of 1250°F, from Wisconsin Oven Corporation, a Thermal Products Solutions company. Guaranteed temperature uniformity of ± 10°F at set points 300°F, 750°F, and 1250°F was documented with a 9-point temperature uniformity survey in empty oven chambers under static operating conditions.
“East Carolina Metal Treating has been incredible to work with,” said Mark Schahczinski, Sales Engineer, “and we look forward to working with them for many years to come. ECMT even filmed the installation process for these five batch ovens, and the time lapse video is available to watch on both the WOC and ECMT Facebook pages.”
A U.S. integrated steel producer headquartered in Pittsburgh, Pennsylvania, recently announced that it will invest more than $1 billion to construct new facilities in Pennsylvania, including a sustainable endless casting and rolling facility at its Edgar Thomson Plant in Braddock, Pennsylvania.
David B. Burritt, president and CEO of U.S. Steel
United States Steel Corporation (U.S. Steel) announcement highlights] the company’s continued commitment to steelmaking in Pennsylvania. In addition to the endless casting and rolling facility, the company plans to build a cogeneration facility at its Clairton Plant in Clairton, Pennsylvania. Both are part of the U.S. Steel’s Mon Valley Works.
The cutting-edge endless casting and rolling technology combines thin slab casting and hot rolled band production into one continuous process and, according to U.S. Steel, will make Mon Valley Works the first facility of this type in the United States, and one of only a handful in the world, replacing the existing traditional slab caster and hot strip mill facilities at the Mon Valley location.
“This is a truly transformational investment for U. S. Steel,” said David B. Burritt, president and CEO of U.S. Steel. “We are combining our integrated steelmaking process with industry-leading endless casting and rolling to reinvest in steelmaking and secure the future for a new generation of steelworkers in Western Pennsylvania and the Mon Valley. U. S. Steel’s investment in leading technology and advanced manufacturing aligns with our vision to be the industry leader in delivering high-quality, value-added products and innovative solutions that address our customers’ most challenging steel needs for the future. We believe that adding sustainable steel technology to our footprint will create long-term value for our employees, our region, our customers and our investors.”
With this investment, Mon Valley Works will become the principal source of substrate for the production of
the company’s industry-leading XG3™ Advanced High Strength Steel (AHSS) that assists automotive customers in
meeting fuel efficiency standards. This project, in addition to producing sustainable AHSS, will improve
environmental performance, energy conservation and reduce our carbon footprint associated with Mon Valley Works. First coil production is expected in 2022, contingent upon permitting and construction.
This article on the critical role of valve safety trains in the prevention of catastrophic fuel-delivery accidents at heat treating facilities is authored by Robert Sanderson, P.E., Director of Business Development in the Combustion Safety division of Rockford Systems, LLC, based in Rockford, Illinois. Valve safety trains require regular inspections, maintenance, and training.
Heat treating, a thermal process used to alter the physical, and sometimes chemical, properties of a material or coating, is a high-temperature operation that involves the use of heating or chilling, normally to extreme temperatures, to modify a material’s physical properties — making it harder or softer, for example. Applications for heat treating are virtually endless, but at the heart of all thermal processes is the valve safety train.
These fuel-delivery devices maintain consistent conditions of gasses into furnaces, ovens, dryers, and boilers, among others, making them crucial in assuring safe ignition, operation, and shutdown. Equally important, they keep gas out of the system whenever equipment is cycled or shut off.
A valve safety train isn’t a single piece of equipment. Instead, it has many components including regulators, in-line strainers (“sediment traps”), safety shut-off valves (SSOV), manual valves (MV), pressure switches, and test fittings logically linked to a burner management system.
Flame-sensing components make sure that flames are present when they are supposed to be, and not at the wrong time. Other components may consist of leak-test systems, gauges, and pilot gas controls. At a minimum, there are two crucial gas pressure switches in a valve safety train, one for low pressure and one for high pressure. The low gas pressure switch ensures the minimum gas pressure necessary to operate is present. As you would assume, it will shut off fuel to the burner if the gas pressure is below the setpoint. The high gas pressure switch ensures excessive pressure is not present. It too will shut off fuel if the gas pressure is too high. Both switches must be proven safe to permit operation. Additionally, there will be an air pressure switch to ensure sufficient airflow is present to support burner operation.
Some systems have supplementary pressure switches, such as a valve-proving pressure switch. Switches such as these are typically used to enhance safety or provide other safety aspects specific to that application’s needs. A multitude of sensors within the valve safety train — pressure switches, flame detectors, position indicators — and isolation and relief valves work together in concert to prevent accidents.
Valve safety trains must be compliant with all applicable local and national codes, standards, and insurance requirements. The most common of these for North America are NFPA, NEMA, CSA, UL, FM. Annual testing and preventive maintenance are not only an NPFA requirement, but also oftentimes required by insurance agencies, equipment manufacturers, and national standards, including ANSI, ASME, and NEC.
Set Your Trap
The primary function of a valve safety train is to reliably isolate the inlet fuel from the appliance. Safety shut-off valves are purposely selected to do this. To protect these valves, the initial section of a safety train is used to condition the fuel and remove debris that could potentially damage or hinder all downstream safety components.
The first conditioning step is a sediment trap (a.k.a. dirt leg, drip leg). This trap captures large debris and pipe scale and provides a collection well for pipe condensates. The proper orientation of a sediment trap is at the bottom of a vertical feed. This downwards flow arrangement promotes the capture of debris and condensate into the trap. A horizontal feed across a sediment trap is an improper application. The second conditioning step is a flow strainer or filter element. These devices are fine particulate sieves. The removal of fine particulates from the fuel stream further protect the downstream safety devices from particulate erosion and abrasion. Taken together these conditioning steps remove particulates and condensates that might block, hinder, erode, or otherwise compromise the safety features of the downstream devices.
The Explosive Force of a Bomb
Owing to the presence of hazardous vapors and gases, a poorly designed or inadequately maintained safety train can lead to catastrophic accidents, ranging from explosions and fires to employee injuries and death. When this explosive force is unleashed, the shock wave carries equipment, debris, materials, pipes, and burning temperatures in all directions with tremendous force.
The following incidences provide just a few examples of why it is important to purchase the highest quality valve safety train and to keep it professionally maintained, inspected, and tested.
In 2018, a furnace explosion at a Massachusetts vacuum systems plant killed two men and injured firefighters as a result of fuel malfunction.
In Japan, an automobile manufacturer lost tens of millions of dollars when it was forced to shut down production for nearly a month after a gas-fueled furnace exploded due to flammable fumes building up in the tank.
In a Wisconsin bakery, an employee was seriously injured when he ignited an oven’s gas and was struck by a door that was blown off. A malfunctioning valve had allowed natural gas to build up inside the oven.
In 2017, a van-sized boiler exploded at a St. Louis box company, killing three people and injuring four others. The powerful, gas-fueled explosion launched the equipment more than 500 feet into the air.
In 2016, a boiler explosion in a packaging factory in Bangladesh enveloped the five-story building in flames, killing 23 people.
Two Dangers: Valves and Vents
Valves are mechanical devices that rely upon seats and seals to create mechanical barriers to control flow. Over time, these barriers wear out for a variety of
Glassblowing Furnace with Pipes
reasons, whether it is age, abrasion, erosion, chemical attack, fatigue or temperature. Increased wear contributes to leaks, and leaks lead to failures and hazards. Defective valves can allow gas to leak into a furnace even when the furnace is not in operation. Then, when the furnace is later turned on, a destructive explosion could occur.
Testing a valve’s integrity is an evaluation of current barrier conditions and may be used to identify a valve that is wearing out prior to failure. As such, annual valve leakage tests are an important aspect of a safety valve train inspection program. Along with annual testing, valves should be examined during the initial startup of the burner system, or whenever the valve maintenance is performed. Only trained, experienced combustion technicians should conduct these tests.
Improper venting is another danger. Here is the problem: Numerous components in a valve safety train require an atmospheric reference for accurate operation. Many of these devices, however, can fail in modes that permit fuel to escape from these same atmospheric points. Unless these components are listed as “ventless,” vent lines are necessary. Vent lines must be correctly engineered, installed, and routed to appropriate and approved locations. In addition, building penetrations must be sealed, pipes must be supported, and the vent terminations must be protected from the elements and insects. In short, vent lines are another point of potential failure for the system.
Even when vent lines are properly installed, building pressures can vary sufficiently enough that they prevent optimal burner performance. Building pressures often vary with seasonal, daily weather, and manufacturing needs, further complicating matters. Condensate in vent lines can collect and drain to low points or into the devices themselves. Heating, cooling, and building exhausters are known to influence building pressures and device responses, but so can opening and closing of delivery doors for shipping and receiving. Hence a burner once tuned for optimal operation might not be appropriately tuned for the opposite season’s operation.
The smart alternative to traditional vented valve trains is a ventless system that will improve factory safety and enhance burner operation. Ventless systems reference and experience the same room conditions where the burners are located, resulting in more stable year-round operating conditions, regardless of what is happening outside. Additionally, ventless designs typically save on total installation costs, remove leaky building penetrations, eliminate terminations that could be blocked by insects, snow or ice, improve inspection access, and ensure a fail-safe emergency response.
Final Thoughts
Valve safety trains are critical to the operation of combustion systems. Despite being used daily in thousands of industrial facilities, awareness of their purpose and function may be dangerously absent because on-site training is minimal or informal. To many employees on the plant floor, this series of valves, piping, wires, and switches is simply too complex to take the time to understand. What is known can be dangerously misunderstood.
Understanding of fuel-fired equipment, especially the valve safety train, is necessary to prevent explosions, injuries, and property damage. The truth is, although valve safety trains are required to be check regularly, they are rarely inspected, especially when maintenance budgets are cut. And while codes require training, they offer very little in terms of specific directions.
As a safety professional, the onus is on you. You and your staff must have a core level of knowledge regarding safe practices of valve safety trains, even if a contractor will be doing the preventive maintenance work. Most accidents and explosions are due to human error and a lack of training when an unknowing employee, for example, attempts to bypass a safety control. Preventive maintenance is essential to counter equipment deterioration, as is the documentation of annual inspection, recording switch set points, maintaining panel drawings, and verifying purge times. Accidents happen when this type of documentation is not available. Don’t wait for a near-miss or accident to upgrade your valve safety train.
DC53 Steel, a general purpose cold work mold and die steel with exceptional strength and resistance qualities, is nonetheless “only as good as the heat treatment it receives,” according to our Best of the Web resource today. Not surprisingly, manufacturers find these excellent characteristics for machining applications.
The folks at International Mold Steel, Inc., a steel distributor in Florence, Kentucky, have compiled a primer on heat treating DC53, which is known not only for its strength and resistance, as mentioned, but also for have a higher hardness than D2 after heat treatment. This is critical for machining shops where die and mold life expectancy is dependent upon proper high-temperature tempering and high hardness.
A University of Texas at Arlington thesis student recently investigated thermal annealing to determine how to increase inter-bead bond strength overall in 3D printing processes.
Rhugdhrivya Rane tackled the dilemma of weak tensile strength in FDM parts and whether parameters chosen by the user — such as temperature ranges and pressure gradients — can affect an increase in inter-bead bond strength. The researcher used thermal annealing, and thermal annealing with unidirectional mechanical pressure in the Z direction, 3D printing a variety of specimens in ABS. The method of 3D printing was chosen due to its increased popularity in mainstream manufacturing.
“The parts were printed using two different sets of print parameters: high and low settings, to investigate the effect of heat treatment on both sets of print parameters. The values of temperature, time and applied pressure during heat treatment were varied to obtain a detailed comparative study and the correlation between the given variables and the increase in ultimate tensile strength.” ~ Rane
The discovery was that “higher temperatures and longer exposure to heat produced better tensile strength, along with increased ductility.”
“Though thermal annealing and uniaxial pressure cause an increase in the strength of the parts, the print parameters play a vital role in determining the initial mechanical properties of the parts. When the parts are fabricated with a higher value of flow rate and extrusion temperature, they exhibit significantly higher mechanical properties as compared to parts printed with substandard setting,” concluded the researchers. “Thus, by controlling the print parameters and using the right values of temperature and pressure we can see substantial increase in strength of FDM parts.”
Photo credit/caption: via UTA / “Tensile testing of dogbone specimens”
During the day-to-day operation of heat treat departments, many habits are formed and procedures followed that sometimes are done simply because that’s the way they’ve always been done. One of the great benefits of having a community of heat treaters is to challenge those habits and look at new ways of doing things. Heat TreatToday‘s 101 Heat TreatTips, tips and tricks that come from some of the industry’s foremost experts, were initially published in the FNA 2018 Special Print Edition, as a way to make the benefits of that community available to as many people as possible. This special edition is available in a digital format here.
Today we continue an intermittent series of posts drawn from the 101 tips. The tips for this post come from a variety of categories but all generally address safety or cost-saving ideas.
Dr. Valery Rudnev, FASM, Fellow of IFHTSE, Professor Induction, Director Science & Technology, Inductoheat Inc., An Inductotherm Group company
Heat TreatTip #2
Avoid axle shaft cracks after induction tempering
Situation: In induction scan hardening of axle shafts, there was NO cracking occurred after scan hardening (case depth varies from 5 mm to 8 mm). Cracks appeared in the spline region after induction tempering.
Solution: Most likely, the cause of this problem is associated with a reversal of residual stress distribution during induction tempering. Reduce coil power for tempering and increase time of induction tempering. Multi-pulse induction tempering applying lower power density might also help. As an alternative, instead of modifying temper cycle, you can also try to reduce quench severity by increasing the temperature of the quenchant and/or its concentration.
When designing a vacuum furnace installation with a closed loop water system, elevate the tank and pump about 9 feet, then cage the space underneath for thermocouple storage, spares, and tools. Saves shop floor space.
IR cameras have come way down in price—for a thousand dollars, you can have x-ray vision and see furnace insulation problems before they cause major problems—also a great diagnostic tool for motors, circuit breakers, etc. (And you can spot deer in the dark!)
When SCRs are involved in the design of a new piece of equipment, questions arise. Control Concepts Inc of Chanhassen, MN, offers a 20-point design checklist to help engineers who don’t specialize in power controllers. Good reading. Search for “design checklist” at the website.
Before you specify a heat treatment, stop and consider your options. Rather than reusing an old specification, ask the design engineer to determine the stress profile, and base the hardness or case depth on real stress data. Is this complicated? Maybe. But especially for carburizing, why pay for more depth than you need, and why take the risk of inadequate strength? The 21st century is here. We have ways to help with the math. Let’s move beyond guess and test engineering methodology.
A steel manufacturer recently announced that it will build its new state of the art steel plate mill in Brandenburg, Kentucky, producing cut-to-length, coiled, heat-treated, and discrete plate.
Nucor Corporation will invest approximately $1.35 billion to build the mill along the Ohio River southwest of Louisville, which will be capable of producing 1.2 million tons per year of steel plate products and is expected to be fully operational in 2022, pending permit and regulatory approvals.
John Ferriola, Chairman, CEO & President of Nucor Corporation
“This strategic investment will enable us to build a clear market leadership position in the U.S. plate market. Kentucky is an excellent location for this mill, right in the center of America’s largest plate consuming region,” said John Ferriola, Chairman, CEO & President of Nucor Corporation. “Our acquisition of the Gallatin sheet mill in Ghent, Kentucky five years ago has been a tremendous success, and we are pleased to add a second mill in the state.”
The new plate mill will give Nucor the ability to produce 97 percent of the products demanded in the domestic plate market, including the specialty higher-margin products, including the discrete plate ranging from 60 to 160 inches wide, and in gauges from 3/16 of an inch to 14 inches. The selected location on the Ohio River will give Nucor logistical advantages in sourcing raw materials and serving customers throughout the Midwest. Nucor currently operates plate mills in North Carolina, Alabama, and Texas.
Nucor has two additional major investment projects underway at its Gallatin sheet mill in Kentucky. Nucor Steel Gallatin’s new galvanizing line will be operational during the second quarter of this year. And, its project to increase Gallatin’s hot-rolled coil capacity at expanded widths of up to 73 inches is expected to come online during 2021. The new plate mill and the projects at Nucor Steel Gallatin represent more than $2 billion in investments in the state of Kentucky.
This article continues the ongoing discussion on Equipment Selection for Induction Hardening by Dr. Valery Rudnev, FASM, IFHTSE Fellow. Dr. Rudnev previously reviewed equipment selection for scan hardening in three parts. The first part on equipment selection for continuous and progressive hardening is here; the third part is here. To see the earlier articles in the Induction Hardening series at Heat TreatTodayas well as other news about Dr. Rudnev, click here.
Frequency Selection
Depending on the application specifics, continuous and progressive hardening lines may use the same frequency for various in-line coils. In other cases, power levels and frequencies may be different at different heating positions. The presence of three general process stages (described in Part 1) makes a marked impact on a selection of process parameters and the design of an induction system.
When using different frequencies for the various heating stages, the coil design may need to change as well (e.g., a number of coil turns may need to be adjusted for load matching purpose). Just as the eddy current penetration depth in the heated part is affected by the frequency, the current flow in the inductor is affected as well. The wall thickness of the inductor turns (i.e., copper tubing wall) might need to be adjusted to accommodate different frequencies to maximize the coil electrical efficiency.¹
The wall thickness of an inductor’s heating face should be increased as frequency decreases. It is highly desirable for the current-carrying copper wall thickness to be 1.6 times greater than the current penetration depth in the copper (δCu). Increased kilowatt losses in the copper, which are associated with reduced electrical efficiency and greater water-cooling requirements, will occur if the wall is thinner than 1.6∙δCu. In some cases, the copper wall thickness can be noticeably thicker than the recommended value of 1.6∙δCu. This is because it may be mechanically impractical to use a tubing wall thickness of, for example, 0.25 mm (0.01 in.).
As an example, Figure 1 shows a number of continuous in-line multi-coil systems for induction heat treating wire products.²
Several continuous in-line systems for heat treating wire products (Courtesy of Radyne Corp., and Inductotherm Heating & Welding, UK. Both are Inductotherm Group companies.)
There are noticeable benefits of compact induction systems compared to fluidized beds, infrared heaters, and gas furnaces, such as quick response and the ability to provide a rapid change in the process operating parameters to accommodate the required temperature of the wire/cable being processed at speeds up to 5 mps. Frequencies that are in the range of 10 to 800 kHz are commonly applied. A dual-frequency concept can be beneficial to enhance electrical efficiency of while heating different diameters/thicknesses or it can be advantageous for through heating of metallic alloys that exhibit low toughness/high brittleness.
According to the dual-frequency concept, a lower frequency is used during the initial heating stage when the steel is magnetic. In the final heating stage, when the steel becomes nonmagnetic with significantly increased current penetration depth δsteel and becomes substantially more ductile, it is beneficial to use a higher frequency.
Case study¹:
As an example, consider the induction heating of a 1/8 inch-diameter (3.2 mm-diameter) steel rod from ambient to 2000°F (1100°C) using both a single 10-kHz frequency and dual 10-kHz/200-kHz frequencies (see Figure 2). When using the single frequency of 10 kHz (Figure 2, left), the rod’s final temperature experiences very little change regardless of the coil power that is increased more than fivefold (from 17 to 90 kW). The only noticeable difference is related to the initial slope of the temperature-time curve, where the steel is ferromagnetic. Upon reaching the Curie point, there is no noticeable temperature rise. This is the result of severe eddy current cancellation making the steel rod transparent (practically speaking) to the electromagnetic field of the induction coil.
Illustration of the dual-frequency concept when induction heating a 1/8 inch-diameter (3.2 mm-diameter) carbon steel rod from room temperature to 2012°F (1100°C) using both a single frequency of 10 kHz (a) and dual frequencies of 10 kHz/200 kHz (b). (Source: V.Rudnev, Systematic analysis of induction coil failures, Part 11c: Frequency selection, Heat Treating Progress, January/February, ASM Intl., 2008, pp. 27–29.)
In contrast, Figure 2, right, shows that a dual-frequency approach provides a remarkable improvement in the ability to heat the rod above the Curie temperature. A power of 14 kW/10 kHz was used to heat the rod below the Curie point and a power of 19 kW/200 kHz was used above it. The total required power is only 33 kW, compared with 90 kW using just 10 kHz, which was still unable to provide the required temperature rise.
Note: The target temperature of 2000°F (1100°C) is above typical target temperatures when hardening plain carbon or low alloy steels and it is more suitable for hot forming applications. This temperature was selected here to better illustrate a dual-frequency concept and the importance of avoiding eddy current cancellation when choosing operating electrical frequencies. It should be noted though that it is not unusual that the heat treating protocols/recipes for some alloyed steels and stainless steels may require target temperatures of 1900°F to 2100°F (1050°C to 1150°C) range.
In some not too often cases, three frequencies may be used. Lower frequency is applied for preheating inductors, a medium frequency is used for mid-heat inductors, and a high frequency is used for final heat inductors.
Sometimes, it is required that the induction system should be able to heat a variety of sizes using a single frequency. In these cases, in order to provide efficient steel heating, it is necessary to choose a frequency that will guarantee that the “diameter-to-current penetration depth (δsteel)” ratio exceeds 3.6 for any workpiece diameter or heating stage. Thus, it is important to remember that when calculating δsteel, the values of electrical resistivity and relative magnetic permeability of the heated material should correspond to their values at the highest temperature that occurs during the entire heating cycle.
The next installment of this column will review a variety of styles of inductors used in continuous and progressive induction hardening applications.
J.Mortimer, V.Rudnev, D.Clowes, B.Shaw, “Intricacies of Induction Heating of Wires, Rods, Ropes, and Cables”, Wire Forming, Winter, 2019, p.46-50
Dr. Valery Rudnev, FASM, IFHTSE Fellow, is the Director of Science & Technology, Inductoheat Inc., and a co-author of Handbook of Induction Heating (2nd ed.), along with Don Loveless and Raymond L. Cook. The Handbook of Induction Heating, 2nd ed., is published by CRC Press. For more information click here.
A family-owned commercial heat treating company recently expanded the capabilities of its Ontario-based facility with the purchase of two batch furnaces.
Cambridge Heat Treating, located in Cambridge, Ontario, purchased two new Allcase® Batch Integral Quench Furnaces in addition to two used Allcase furnaces to be used in the same line, along with a previously purchased 30”x30”x48” Allcase with top cool.
Surface Combustion, headquartered in Maumee, Ohio, commissioned the new furnaces. which are all serviced by Surface’s charge car, Uni-DRAW® Batch Tempering Furnaces, washers, and RX® Endothermic Atmosphere Gas Generator. The 36”x48”x36” batch heat treat line expands Cambridge’s capacity for carbonitriding, carburizing, neutral hardening, and has added ferritic nitrocarburizing (FNC) and normalizing capacity with the atmosphere top cool chambers on the two new Allcases.
“We could not be happier with our Surface purchases,” said Peter Robbins, owner of Cambridge Heat Treating. “Their robust equipment is built for longevity, and we appreciate that they are easy to operate and maintain. Surface’s Aftermarket parts department ensures that we always have the necessary parts for maintenance in a timely manner, and their customer service department is always available for a telephone or service call.”
