Please explain in details the difference between refractory grade and metallurgical grade minerals.?

Question

My focus is especially in chrome ore.

Sorry, my question is very practical while your experience is only theoretical. The different grades of mineral is to distinguish their application. For example, if the ore consists too low Cr2O3, then the only aplication is for chemical use and not (economically) worth to produce chrome metals (which, in practical metallurgy, 40% min Cr2O3 would be the min appropriate). What my question is: most recently I received from chrome ore mines offer of refractory grade at 53% min Cr2O3 concentrates but I don't know this high refractory grade is even superior than metallurgical grade and their actual difference.

Please refer to the following website and you may have some ideas on refractory grade chrome ore: http://www.tatasteel.com/company/ORISSA_chromite.asp

Answer 1

In regards to ores of Chrome, the Refractory industry prefers the following 4 grades:
Refractory Special Grade: 52 – 54%Cr (with SiO2 at 2% max)
Refractory Grade I: 52 – 54%Cr (with SiO2 at 5% max)
Refractory Grade II: 46 – 48 %Cr (with SiO2 at 6 to 9%)
Refractory Grade III: 40 – 42%Cr (with SiO2 at96 to 12%)

The Metallurgical industry prefers the following grades:
Metallurgical Grade – Ferro Chrome: Cr2O3 46%min (with SiO2 at 4 to 6% and A12O3 at 3 to 10%)
Metallurgical Grade – Charge Chrome Cr2O3 40%min (with Cr:Fe at 1:6 min.)

The specifications for metallurgical use are becoming less rigid with the Cr2O3 requirement dropping to 46%. This has resulted in broadening the base of supplies of metallurgical grade ore.

Answer 2

I'm not exactly sure what is meant by metallurgical grade, but it might have something to do with the amount of impurities in the substance. Refractory grade has to do with a substance's melting temperature. Most refractory materials have melting points between 1815ºC - 3315ºC and can only tolerate 1-5% melting. They are used in kilns and therefore must be structurally sound. There exists a complete solid solution series between Fe3O4 and FeCr2O4, where Cr2O3 concentration varies beween 0 and 68 weight%. Melting temperature varies between 1594 ºC for pure Fe3O4 to 2180 ºC for pure FeCr2O4. As the chromium content increases, melting temperature increases, and hence the material becomes more refractory.

Answer 3

Metallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. Refractory is a term used in casting of metals.
Refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory.
Chromium is mined as chromite (FeCr2O4) ore, this is the only ore that is really commercially mined. I never found in any of my research the terms refractory grade or metallurgical grade. The definitions of each term do not seem to correlate to one another.
Hope this helps