Silicon carbide (SiC) heating elements are the workhorse of industrial high-temperature furnaces up to roughly…
MoSi2 Element Diameter Guide: Φ3/6, Φ4/9, Φ6/12, Φ9/18
MoSi2 Element Diameter Guide: Φ3/6, Φ4/9, Φ6/12, Φ9/18
The diameter pair — written hot / cold in millimetres — sets how much power an element can carry and how it fits your furnace. This guide explains the four standard MoSi2 sizes and how to choose between them.
See the full MoSi2 spec sheet and our surface-load limits (in the spec sheet) for the underlying numbers.
The four standard sizes
| Hot / cold diameter | Approx. current at working temp | Relative surface load | Typical use |
|---|---|---|---|
| Φ3/6 | Low (~30–40 A) | Highest W/cm² per size | Compact dental / small chambers |
| Φ4/9 | ~60–80 A | High | Dental sintering (Sirona HTC Infire), small units |
| Φ6/12 | ~150–170 A | Medium | General box / tube furnaces, most common |
| Φ9/18 | ~250–300 A | Lower per area, high total | High-power, large chambers, fast heat-up |
Note: exact current comes from the element datasheet; the values above are planning figures for the heated zone.
How to choose
- Power needed: a bigger diameter carries more total watts.
- Chamber size: small chamber → Φ3/6 or Φ4/9; large → Φ6/12 or Φ9/18.
- Surface load: stay within the W/cm² table — lower load means longer life.
- Fit: match the U-bend reach and shank spacing to your furnace drawing.
Because MoSi2 has a positive temperature coefficient (resistance rises as it heats), new and old elements self-balance on a shared circuit — you do not have to replace all at once.
Related guides
- Molybdenum disilicide heating elements
- Silicon carbide heating elements
- MoSi2 vs SiC heating elements guide
- W-type MoSi2 heating elements
- Silicon carbide heating elements complete guide
Why Specify Molybdenum Disilicide (MoSi2) heating elements with HeatingDriver
HeatingDriver is a manufacturer and exporter of Molybdenum Disilicide (MoSi2) heating elements with nearly 20 years of experience supplying furnace builders, labs, and integrators worldwide. We stock standard grades and build custom sizes from your drawings, and we review your element drawings free of charge before production. Browse our Molybdenum Disilicide (MoSi2) heating elements catalog or contact our engineers for a quote.
Frequently Asked Questions
Q: What do the two numbers in a size such as Φ6/12 mean?
They are the hot and cold diameters in millimetres. Φ6/12 has a 6 mm hot zone and 12 mm cold ends. The hot diameter sets the surface load and current the element can carry, while the thicker cold end keeps the terminal area cool.
Q: Which of the four standard diameters fits my furnace?
Φ3/6 carries roughly 30–40 A and suits compact dental or small chambers. Φ4/9 carries about 60–80 A for dental sintering units such as the Sirona HTC Infire. Φ6/12 carries about 150–170 A and is the most common size for general box and tube furnaces. Φ9/18 carries about 250–300 A for high-power, large chambers and fast heat-up. Exact current comes from the element datasheet; these are planning figures for the heated zone.
Q: How do I decide when two sizes both fit mechanically?
Work through four checks: the power needed, since a bigger diameter carries more total watts; the chamber size, where small favours Φ3/6 or Φ4/9 and large favours Φ6/12 or Φ9/18; the surface load, staying inside the W/cm² table because a lower load means longer life; and the fit, matching U-bend reach and shank spacing to your furnace drawing.
Q: Do I have to change all elements at the same time?
No. MoSi2 has a positive temperature coefficient, so resistance rises as the element heats and new and old elements self-balance on a shared circuit. You can replace them individually rather than as a full set.
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