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Manganese Content
Posted by Michael from Kansas City, MO, US on June 5, 2007
What factors are to be taken into consideration when selecting Mn content in cones parts?
The reason I ask is that I have heard the more abrasive the material the lower the Mn content you should have, i.e. high abrasion = low Mn content and high compressive strength = high Mn content.
Though perhaps not your intent, there are two subjects in this inquiry.
Let's start by noting that the manganese element content is relative to the carbon content. We've found a considerable inter-relationship between manganese and carbon content of wear steel, especially as it applies to fatigue resistance of crusher parts.
Regarding manganese content, we've been able to amass some useful generalizations regarding application of high alloy manganese. It goes like this:
The best use of high alloy manganese comes when the material being crushed is at a mid-point between low and high compressive strength values, along with low and high silica contents. The low end of that scale is 20k p.s.i. compressive strength and .2 silica content; the high end of that scale is 80k p.s.i. compressive strength and .8 silica content. This allows maximum advantage for use of high alloy manganese with materials at 50k p.s.i. with a .5 silica content. Any deviation in either value, in either direction, alters the degree of gain or loss in the successful application of the high alloy material.
We drew those conclusions from a customer site where we doubled the service life of jaw dies over conventional 12% manganese. At the low end of the scale, low silica and strength values don't allow the manganese to work harden enough to improve wear rates. The high end values will overcome the manganese steel's ability to resist fatigue and fail before they are fully expended.
To reply to your question as presented -- the more abrasive the material being crushed, the higher carbon levels are in order, such as those in high hardness carbon steels, or high hardness irons. The crushing of very high compressive strength materials is best suited to conventional 12% manganese content levels with low carbon values of under 1.0. This concurs with the original principle of crushed materials somewhere between those extremes optimizes the application of high manganese and carbon wear alloys.
The development of better wearing manganese is an evolutionary process. In another 20 years, there'll be a different set of numbers in ratio that optimize crusher wear materials.