We like to inform you with the composition of the different steels and other materials used in the manufacturing of grinding barrels to help you choose the most suitable ones for your operations.
This steel is recommended in applications where molybdenum interferes in the analysis of the material that will be ground as it is the case in some geochemical work. It has the same hardness as alloy 1, 58-62 Rockwell but, because it does not have molybdenum it is somewhat less wear and abrasion resistant; approximately 10-25% upon the media to be ground.
It is the most used for general purpose pulverizing (assaying), where the alloying elements of chromium and molybdenum do not affect the analysis. This material is very hard and tough and it is recognized to be the best for applications where abrasion and impact is the norm.
This steel has only 0.5% chromium and 0.5% tungsten among other alloying elements and it is used where very small traces of chromium and tungsten can be tolerated. These low amounts of alloying elements in many cases can be accepted as the contamination occurring from a grinding cycle is extremely low. However, this steel is not recommended for wearing and impact applications as alloy 1 or alloy 2. Moreover, as it wears its surfaces are not as smooth as originally and certainly not as smooth as the surfaces of alloy 1 and alloy 2.
This steel is fully hardened having a .65 – .75 carbon and a .60 – .90 manganese content. Since this steel is produced from ingots originating from mined ore and not from recycled steel, which notoriously has more contaminating elements, it is a highly recommended steel to minimize cross contamination. It will wear slightly faster than alloy-2 and alloy-1.
Its composition, toughness, mass, and hardness makes it an ideal alloy for grinding applications as it out performs all the others in performance (faster grinding) and contaminates less than all the other steels. But its costs and the rare cases when it chips or cracks discourages people from using it. This alloy and ceramic are the best for minimizing contamination the obvious reason being their extreme hardness.
Its composition, hardness, and wear resistance makes it the ideal material for this application. Sadly, it is relatively easy to rupture and is not repairable.
The 250mL grinding barrel, alloy-2, upon the hardness and the length of the grinding cycle, releases approximately from 4 to 28 ppm for each 1% of total metal composition. For example when grinding a sample of 250 grams in the 250mL grinding barrel alloy-1, for 90-180 seconds the amount of contamination in the media released from the various grinding surfaces that should be expected is 4 – 28 ppm moly, 4 – 28 ppm carbon, 4 – 28 ppm silicon, 2- 18 ppm man., 40 – 280 ppm cr., and 330 – 2250 ppm iron.
Tungsten carbide and ceramic grinding barrels release 0.5 – 2 % the amount above mentioned. On the contrary, grinding elements made of alloy 01 release slightly more and the ones made of mild steel wear out more than all the others.
Contamination due to wear can vary considerably from the indicative percentages above mentioned. Hardness of media to be ground, length of grinding cycle, change volume and/or mass ground from time to time, initial size of media to be ground, versus final product obtained wear condition of grinding elements etc. are all factors that affect the performance and results in the pulverizing process.
COMPOSITION OF GRINDING BARRELS
|Tungsten Tool Steel||0.5%||Chromium||Max.|
* Additive of several elements in amounts of less than 0.05% for facilitating casting. Will release 2 – 4 ppm of tungsten and less of that, if at all, of any other alloying element. Seems to be as durable as other types of tool steel. Any amount of less than 0.03% is considered impurities and is insignificant.
CARBON STEEL COMPOSITION
Unless otherwise specified, the amount indicated is in ppm (parts per million).