Become an expert in heavy abrasion / pressure wear management

Become an expert in heavy abrasion / pressure wear management

As mentioned in our article “The 10 types of stress that impact your running costs“, 67% of wear in the minerals industry is related to abrasion phenomena.

The first step in the mineral industry is extracting the ore, which requires solutions with good abrasion resistance. Once extracted, the ore needs to be reduced in size for further processing. Primary reduction methods include crushing and impact:

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Locations

Gyratory crusher

Hammer crusher

Jaw crusher

For secondary reduction, crushers (such as roller presses, vertical shaft mills, ball mills, and vertical mills) are typically used.

Crushing, Grinding, and Impact:

Crusher being hardfaced in our Integra™ workshops

Impact Crushing (percussion): Uses a high-speed rotor with hammers or beaters to impart high energy to the material, causing it to break upon impact with the hammers, other materials, or an anvil.

Crushing and Grinding: Apply pressure to break materials. Two metal parts compress the material, causing it to fragment due to the intense pressure. This results in strong contact between the mineral and metal surfaces and between the material particles themselves.

Pressure on the ore causes it to fragment, while pressure on the metal surfaces leads to abrasion. The harder and more angular the mineral (as noted on page 32 of our brochure “The Fundamentals of Hardfacing by Arc Welding“), the greater the abrasive wear.

In both primary and secondary reduction, various components of the equipment experience significant abrasion, affecting their durability.

Example: Vertical Crusher

A vertical crusher can grind both soft materials (like limestone) and highly abrasive materials (such as coal with high silica content or blast furnace slag). It operates with vertically positioned rollers rotating against a rotary table.

The material to be ground is fed into the centre of the mill and distributed between the rollers and the table by centrifugal force. The combined weight of the rollers and applied mechanical pressure grinds the material. The infeed zone is more resistant to severe abrasion than the outfeed zone (outer diameter of the track) due to lower pressure and the presence of larger material particles that limit high-speed movement.

Worn roller

Operating Characteristics of Vertical Mills

Vertical mills have a bed of material trapped between the rollers and the table:

A raw mill may have a bed exceeding 300mm in thickness.
A slag or clinker mill typically has a bed no thicker than 50-80mm.

This material bed acts as an abrasive and greatly increases wear on the grinding elements due to high relative speeds. The maximum speed is reached in the outlet zone, where abrasion is greatest.

Combining pressure, abrasiveness, and speed results in severe to very severe abrasion.

Roller being hardfaced

What solutions should be used to combat this severe abrasion under pressure?

ASTM G-65 wear test

Solutions to combat abrasion under pressure involve overlays with excellent abrasion resistance that can withstand mechanical stresses from pressure and surface abrasion from ground products. Mechanically welded or cast solutions are suitable for mechanical stresses but offer limited abrasion resistance. To enhance abrasion resistance, surface treatment via hardfacing welding is ideal.

Welding Alloys offers an unrivalled range of welding alloys providing optimal abrasion resistance and durability. Welding is not only the most economical solution but also environmentally friendly. Our custom abrasion-resistant solutions consider all factors, including maintenance schedules, optimised performance, and reduced energy consumption.

To learn more about how Welding Alloys addresses issues such as abrasion resistance, yield reduction, lower product quality, increased energy consumption, and environmental impact, contact us.

The primary alloys used for maintaining and improving the abrasion resistance of vertical mills belong to the HARDFACE family. As part of our Integra™ services, we use the Integra™ Mill range. Additionally, our innovative MillCarb™ technology incorporates ceramic particles into the welded deposit for exceptional part service life and abrasion resistance.

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