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[About wear steel]  [Weld bucket steel & wear plate]  [Wear of wear steel - Steel vs Stone]  [About cemented carbide]

Hardest wins. The resistance of a steel to the abrasive wear of stone materials to which buckets, crushers, plowshares and flakes are exposed depends mostly on the hardness of the steel. When two surfaces wear against each other, the side with the hardest material will wear out the other more.

Hard minerals with sharp structures that are pulled over a steel surface under pressure grip the surface of the steel and tear it off gradually; just like sandpaper on a tape set. The harder the steel surface, the worse the mineral gets and the slower the steel wears.  
The mineral that wear steel is most often worn down by in Sweden is quartz. Quartz is much harder than the hardest weldable steel that can be produced. Granite and gneiss are the rocks that are most crushed in Sweden and used in roads and foundations. These rocks are composed of several types of minerals where quartz is the largest component. Natural sand, which is still also extracted and used in Sweden, contains a very high content of quartz. However, the natural sand grains are grinded against each other for millennia in water so they do not tear the steel in the same way as crushed material with the same high quartz content does. The level of quartz in the rock varies between different quarries and even within the same quarry there can be large differences. 

How quickly a bucket steel or a wear plate wears down, for example crushed granite, are mostly depending on:

  • The hardness of the steel.
  • The amount of quartz content of the granite.
  • The pressure which the steel and the stone material wear against each other. 
  • The density of the contact surface between the steel and the stone material - finer material - more contact surface - faster wear. 
  • The heat of friction and the ability of the steel to maintain its hardness at the temperature the friction heats it to.

In practice, there are many things that cause the above factors. For example:

  • A lot of rain gives wet crushed stone which becomes heavier and thus increases the pressure and the wear on, for example, the wear surfaces of the loader bucket.
  • Dry roads with cold snow gives high friction and poor cooling and therefore faster wear of the plow steel than sludge.
  • The design of the tool or, for example, the bucket tooth affects how the pressure of the stone material is distributed and thus the wear speed.
  • How the implement is driven affects wear a lot, sometimes most of all, due to the reasons described above.

In Sweden, we usually measure hardness of steel with Brinell (HBW). Hardness of minerals is usually given in the Mohs hardness scale. Mohs scale is 1 to 10 where 10 is the hardest. The hardest mineral is diamond (10). Quartz is at a hardness of 7 Mohs. The hardest possible hardened steel, which has a Brinell hardness of  700 HBW (approx.), corresponds to about 5.5 Mohs, in other words softer than quartz. On the other hand, tungsten carbide is 9 in hardness on the Mohs scale and therefore wears much more slowly than hardened wear steel, which is very useful in snow plow edges, for example.

Even if no hardened wear steel is harder than the quartz-containing stone you break or plow snow on top of, the steel's wear rate decreases with increasing steel hardness. In some cases, 50 HBW higher hardness can double the wear time of, for example, a cutting steel on a rock bucket. The lower the quartz level in the stone material, the more the wear time for each brinell increases. The higher the quartz level in the crushing material, the less difference each brinell makes. In such extreme stone materials, for example, the design of the excavator and the teeth and the machine operator's technology can be more important for the wear time of the steel than Brinell.

Frictional heat is an additional factor that can dramatically increase the wear of the steel. This is because hardened steel loses hardness when it reaches the temperature limit. For example, 500 brinell boron alloy wear steel begins to soften at about 200 degrees. Ordinary 600 brinell boron alloy steel begins to soften at about 175 degrees. This becomes apparent on plow steel that is driven against asphalt at high speed. The higher the speed and pressure, the higher the friction, the higher the temperature and thus the steel softens and it wears very quickly.

Choosing the right steel is a consideration between different factors. Depending on what and how it is going to be used. That decision also includes the question of weldability, read more about it here.

Ask us about the choice of wear steel according to your specific needs and conditions and we will help you find a good solution. It all depends on how the wear steel is supposed to be used.

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