In the thirties, Kanthal introduced a new resistance heating alloy (called Kanthal®) based on iron-chromium-aluminum with a longer life and a higher maximum operating temperature than nickel-chromium. Kanthal manufactures both types of alloys under the names Nikrothal® (nickel-chromium) and Kanthal® (iron-chromium-aluminum).
The two main types of alloys have their own specific properties, with advantages and disadvantages, and are supplied in many different grades and forms. In general Kanthal® type alloy is superior to Nikrothal® in respect of performance and life and is therefore nowadays a standard material choice when it comes to metallic heating elements for industrial furnaces.
The Nikrothal® alloy may have special advantages if you need a heating element having very good mechanical properties in the hot state. Kanthal® APM has, however, creep strength at elevated temperatures in the same level as Nikrothal®.
For the furnace user, using Kanthal® results in less amount of element material and also a longer life. The table below shows an example of weight saving obtained by using Kanthal® instead of nickel-chromium alloys. This lower element weight will also result in considerable cost savings regarding the support system, because fewer suspension hooks are necessary.
The most important advantages with Kanthal® type alloy are:
- Higher maximum temperature of 1425°C compared to 1250°C for Nikrothal®
- Up to four times longer life
- Higher surface load
- Higher resistivity
- Lower density
- No spalling oxide, which may contaminate the goods and the furnace and also cause short circuit or failure of elements and gas burners
A 120 kW furnace equipped with ROB elements. Three elements of 40 kW each, 380 V
|Furnace temperature, °C||1000||1000|
|Element temperature, °C||1068||1106|
|Hot resistance, Rw||3.61||3.61|
|Temperature factor, Ct||1.05||1.06|
|Cold resistance, R20||3.44||3.41|
|Wire diameter, mm||5.5||5.5|
|Surface load, W/cm2||3.09||3.98|
|Wire length 3 elements, m||224.9||174.6|
|Wire weight 3 elements, kg||44.4||29.6|
Weight saving based on same wire diameter:
kg: 44.4 – 29.6 = 33 %