Magsat is determined by fully magnetizing a sample in a strong magnetic field created by a large permanent magnet. The sample is then removed from the magnetic field through a test wire coil; the resulting emu (electro motive unit) is measured and divided by the sample weight to determine the magnetic saturation of the sample.
Magsat is a measure of the lump sum magnetism of pure cobalt. Pure cobalt in cemented carbides has normal magnetic properties. During sintering some of the cobalt in the cemented carbides will alloy with either carbon or tungsten carbide. The maximum Magsat of pure cobalt is 160 emu/g. A 10% cobalt carbide grade can have a maximum Magsat of 10% X 160 = 16.0 emu/g. The following table summarizes the significance of Magsat.
Magsat in a 10% cobalt cemented carbide grade.
| Condition of cobalt | Resulting Magsat for a 10% cobalt grade with a maximum Magsat of 16.0. | ||
| % | Magsat | ||
| Cobalt alloyed with carbon behaves like a ferrite and will be more magnetic than normal. | 97-100+% | >15.5 | Free carbon C02-C08 |
| 95-97% | >15.2-15.5 | Pre-carbon | |
| Cobalt alloyed with normal tungsten carbide, WC, will form a phase at the WC grain boundary that is non magnetic. | 95% | >15.2 13.6 | Pre-carbon |
| 85% | 12.0 | NORMAL | |
| 75% | Pre-Eta | ||
| Cobalt alloyed with bi-tungsten carbide, W2C (Eta), will form the phase we normally refer to as Eta-phase, a non-magnetic alloy. | 77-75% | 12.3-12.0 | Pre-Eta |
| 75-65% | 12.0-10.4 | Medium Eta | |
| 65 or less | 10.4 | Coarse Eta | |
Similar calculations may be made of any known cobalt content straight (WC & Co – only) grade. Steel cutting (WC, Co & cubic carbides TaC, Tic, etc) grades have a larger amounts of cobalt alloyed in the cubic carbide (gamma-phase) solutions.
Note: alpha = WC, beta=Co (binder), and gamma= alloys of various carbide, particularly the cubic crystal from carbide TaC, TiC, etc.