Occasionally this question comes up when a business is looking to expand its heat-treating capabilities, when parts or processes have changed, or when a furnace’s hot zone has reached it’s use capacity.
Graphite to All-Metal
If you’re processing sensitive parts such as titanium or stainless steel, a metallic hot zone will provide a cleaner working environment with a lower probability of contaminated parts. Also consider how your materials might react with carbons in a graphite furnace. Graphite dust lowers melting temperatures and can have an adverse effect — even eutectic reactions — on certain materials.
If your cycle requires high temperatures and ramp rates, an all-metal hot zone is capable of reaching temperatures above 2,400 °F and heating up at a maximum ramp rate of 75 °F per minute. An all-metal hot zone is also capable of achieving a lower leak-up rate than a graphite one, which is often required for processing parts for the aerospace and medical industries.
All-metal hot zones require a power supply with more capacity — as they experience more heat loss — so the first thing our aftermarket specialist would need to check is if your furnace has a large enough transformer. If the transformer needs to be replaced, this would add additional costs. It is more likely the power supply will need to be replaced on larger furnace models.
It is possible to replace your existing graphite hot zone with an all-metal one; however, there are several variables to consider, including your existing power supply, materials and processes. It’s also important to keep in mind metal hot zones require more maintenance and do not generally last as long as graphite ones.
An alternative to replacing the entire graphite hot zone with an all-metal design is switching just the heating element material to molybdenum. This may allow the furnace to ramp up in temperature at a faster rate, but maintain the lower heat loss properties of a graphite insulated hot zone. An Ipsen Customer Service Representative can assess your furnace and review the feasibility of this option.
All-Metal to Graphite
Graphite hot zones are more durable, less expensive, lower maintenance and more energy efficient than their metal counterpart. Graphite is also more resilient against certain brazing processes. If your process doesn’t meet the above considerations for a metal hot zone, replacing it with a graphite one can save you time and money in the long-run. Because graphite hot zones also require less power, you likely won’t have to adjust the power supply.
Switching hot zone types can be done successfully, but we do not recommend doing so without technical consultation. Ipsen’s Sales Engineers can help you determine the best option for your specific needs.
If you have questions about hot zone replacements, contact us at
[email protected] or call 1-844-GO-IPSEN.
Have a heat-treating related question?