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Quenching

Browse previously asked/answered questions below.

  • Why would I want to cryogenically treat tool steels? Does it really affect the microstructure?
    Minfa Lin
    Senior Principal Research Engineer, Ph.D.

    After austenitizing and quenching, tool steels are sometimes subjected to cold treatment at approximately –80°C, followed by tempering. Primarily, the cold treatment is done to increase strength, improve dimensional or microstructure stability, and improve wear resistance. These benefits are due to the transformation of retained austenite to martensite. Some studies show that lowering the cold treatment temperature below
    –100°C does not significantly increase the amount of retained austenite-to-martensite transformation—therefore it does not result in additional benefits. However, other studies show that compared to cold treatment (–80°C), cryogenic treatment (–190°C) further improves wear resistance. For help determining which subzero quenching process can help you produce the best parts, call us at 800-654-4567.

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  • How can I provide customer documentation proving my heat treat process was controlled while treating their products?
    Quality programs that require information about how you process a part for your customers are becoming more common. Understanding what variables you control and what effect they have on your parts is an important step in starting this effort. Variables such as temperature, time, atmosphere flow rates and composition, and utility consumption are good places to start tracking.

    A monitoring system makes this task easier day to day and increases the accuracy of recorded data. Air Products' PURIFIRE® process management system automates data monitoring and collection, and provides additional benefits such as remote monitoring of your process, alarming to indicate problems, and custom report generation for customer documentation. Our engineers help you determine what variables are important for you to monitor and then customize a system that fits both your specifications and those of your customers.

    Benefits such as reduced scrap, elimination of manual data collection, faster problem troubleshooting, and increased product quality can enhance your customer relationship and help your bottom line.

    For more information please call us at 800-654-4567.
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  • I know my flowmeter tells me that I have a certain gas flow rate, but how can I be sure?
    Flowmeters must be sized properly for each particular application, type of gas, gas pressure, and operating range. First, make sure that your flowmeter is calibrated for the specific gravity of the gas that you are metering. Check the label or the glass tube of the flowmeter or call the manufacturer to be sure. Second, operate the flowmeter only at the pressure for which it was calibrated. As an example, a variable-area flowmeter calibrated for 80 psi and reading 1000 scfh will really only be delivering 760 scfh if it is operated at 40 psi. This is a 24% error! Third, for best accuracy and to allow room for adjustment, size the flowmeter so that your normal flow rate falls within 30%–70% of full scale. These three steps will help ensure that you have good control over your gas flows and, ultimately, your process.

    For a free copy of Gas Atmosphere Analysis Guidelines, please call 800-654-4567.
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  • Our gas quenching process uses a lot of gas and then vents it. Can we purify and reuse that gas?
    Annemarie Weist
    Global Lead, Gas Recovery and Recycle

    Depending on impurities, gas volumes and ease of capture, many gases can be and are recycled. You can purify gases like helium with simple membrane or adsorption systems, or argon with an adsorption and getter combination. Adsorption systems are effective because you can select the sieves to optimize impurity removal. If you use layers of sieves, a variety of impurities can be removed to <10 ppm. Air Products’ systems can remove nitrogen, oxygen, argon, carbon monoxide, carbon dioxide, moisture, methane and hydrogen from process gases. In some processes, impurities are so low that you may not need purification—a simple capture and pressurize system may be adequate. We can help recycle your gas. Call us at 800-654-4567.

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  • I use high-pressure gas cylinders and am concerned about safety. Is there a better way?
    John Tapley
    Microbulk Business Development Manager

    Traditionally, high-pressure gas cylinders have been the supply mode for users in the low- to medium-volume range. This has left companies vulnerable to safety risks associated with moving cylinders and exposure to high pressure. Consolidating to a centralized microbulk system eliminates the need to handle cylinders and reduces the risk of product mix-up. Further benefits include decreased exposure to high-pressure containers and reduced traffic congestion with less frequent supplier deliveries.

    Air Products developed the microbulk supply option as a cost-effective, reliable alternative to high-pressure cylinders for nitrogen, argon, oxygen and carbon dioxide supply. In addition to efficient and flexible storage systems, innovative piping solutions are available to help you have a smooth transition from cylinders to microbulk.
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  • I’m experiencing intermittent oxidation in my furnace. Could leaks in the nitrogen houseline be the problem?
    Don Bowe Don Bowe
    Sr. Applications Engineer

    Yes, leaks in any pressurized high-purity gas line can cause intermittent oxidation. There are several possible causes. One is through retrodiffusion—the movement of impurities from the surrounding air to a high-pressure, low-impurity gas houseline. This is driven by concentration gradients, not pressure gradients, and is aggravated by changes in flow rate, pressure or piping temperature.

    Air Products industry specialists can help you determine the cause of your problem. Since the oxidation is intermittent, you’ll need to continuously monitor your nitrogen houseline for leaks with a trace oxygen analyzer. For combustible gas lines, a combustible gas sniffer can also be used. Once impurities are found, the source of the leak can be identified using various techniques, including soap bubble testing, static pressure testing or helium mass spectrometry. Leaks often occur in weld cracks, mechanical joints, valve packing and loose fittings.

    To help minimize wasted product and part oxidation, call us for a leak detection or full process audit at 800-654-4567.
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  • Can I remotely monitor what’s happening in my furnaces and other process equipment while I’m away from my plant?
    Chris Ward Chris Ward
    Engineering Associate

    With the proper instrumentation and controls, you can securely monitor and control your heat treating or thermal process from nearly anywhere in the world! This is possible using a variety of hardware and communication methods, including Internet, dial-up, and cell phones. Alarm and warning notifications can also be proactively delivered to you so you can react to upsets, trends, and events before it’s “too late.” It’s important to identify the key parameters, equipment and instrumentation you want to monitor, and then select the hardware and software that best match your needs. Contact Air Products’ team of remote process monitoring and control specialists at 800-654-4567 for an assessment and recommendations as to how to get started.
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  • How do I know if I’m wasting gas due to leaks in my gas piping?
    John Green
    Research Technician

    Gas piping leaks can result from various conditions, including improper thread sealing, missed brazed joints, defective piping, over pressurization, or even vibration and shocks. A pinhole leak can cost you tens of thousands of dollars per year, depending on the size, number and severity of the leak(s). There are many ways to detect leaks; for instance, using soap tests, pressure drop tests, mass spectrometry or thermal conductivity tests. They all have their place; however, they also often come with limitations in precision, speed, difficulty or cost.

    Air Products’ leak detection service can identify and repair costly leaks in your piping to help improve your part quality and bottom line.

    In a short video, various methods for identifying leaks are described in more detail. You can view it online at www.airproducts.com/experts2. If you’d like to speak to a specialist about a leak detection audit of your facility, give us a call at 800-654-4567, and mention code 833.

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