In foundries, accurate temperature control is absolutely critical, as this profoundly impacts both the quality and efficiency of foundry operations. Two different kinds of pyrometers are used for temperature measurement: contact and non-contact. In this article, we’ll review factors impacted by temperature control, explore the differences between contact and non-contact pyrometers, and examine the pros and cons of each method of measurement.
In metallurgical processes, temperatures must be maintained with precision. Whether you’re melting, alloying, or casting, even small temperature variations can compromise the mechanical properties of the metal and lead to defects like shrinkage, porosity, or cracks in castings. Pyrometers provide the high level of accuracy that’s needed to assure consistent, high-quality results.
More accurate temperature control enables shorter cycle times and improved casting release, supporting higher productivity.
Accurate temperature control is one of the best ways to minimize waste. Maintaining correct temperatures helps ensure the right amount of metal is used for each casting and extends the lifespan of crucibles, refractories, and other equipment.
Maintaining correct temperatures prevents overheating, allowing for more efficient energy consumption. This not only saves money but also helps minimize a foundry’s environmental impact.
Non-contact pyrometers measure the temperature of molten metal without making direct contact with it. They rely on the following components:
As an object is heated, it emits infrared radiation, which is detectable as electromagnetic waves on the infrared spectrum.
The optical systems use lenses or mirrors to focus incoming infrared radiation onto the detector.
The detector generates an electrical signal proportional to the intensity of the infrared radiation it receives.
The infrared pyrometer uses the intensity of the generated electrical signal to calculate the temperature of the object, using the Stefan-Boltzmann law, Planck's radiation law, or another radiation-to-temperature conversion formula.
Some of the benefits of a non-contact pyrometer include:
Non-contact pyrometers offer several advantages for foundries, but also have limitations:
A contact pyrometer, on the other hand, measures the temperature of molten metal using a sensor that comes into direct contact with it and applying the principles of thermal conductivity.
The thermocouple contains two dissimilar metals that produce an electric charge when heated. When the pyrometer comes in contact with an object, the two metals produce a current proportional to the temperature of the object.
A probe is the part of a thermocouple that comes into direct contact with the object being measured.
The galvanometer measures the electrical current produced by the thermocouple and converts it into a temperature reading.
In foundry environments, contact pyrometers are often the better choice for several reasons:
While contact pyrometers with immersible thermocouples are almost always a better choice for molten metal applications, these issues should also be acknowledged:
Pyrometer Applications in Foundries
Pyrometers use a variety of data, including emissivity factors and surface slag interference, in temperature measurement. The result is an extremely accurate temperature, providing all the essential information needed for foundry applications. While contact pyrometers offer serious advantages over non-contact units, pyrometer accuracy can vary quite a bit depending on the application. This makes it critical to choose the right instrument for the job.
SYSCON Sensors provides state-of-the-art molten metal temperature analysis sensors. We’ve been in the industrial business since 1975, crafting high quality instrumentation designed to deliver the most accurate readings possible. With nearly five decades of experience behind us, we’ve now partnered with a new organization that is wholly dedicated to bringing our products directly to our customers. You can always count on SYSCON Sensors for your molten metal analysis needs.