The tungsten-tough approach to tackling ploughing wear-and-tear
Do you ever wonder how machinery companies manage to make their wearing parts tough enough to withstand years of work in difficult soils?
Pottinger engineers gave journalists an insight into this manufacturing process during the recent press trip to the company’s manufacturing plant in the Czech Republic.
They outlined how the rate of wear that a machine part undergoes depends on the characteristics of the soil, the working speed and the working depth.
In terms of soil characteristics, the proportion of minerals such as quartz sand content, the compaction level and the water content are all decisive.
The higher the mineral content of the soil, the higher the rate of wear because mineral particles have a very abrasive effect on tillage tools.
As the effects of wear increase, the geometry of the tillage tools change for the worse as they become less efficient.
Cutting angle and the penetration of the implement becomes blunted which leads to increased power requirement and higher diesel consumption.
Pottinger now looks at different soil and operating conditions and offers three wear parts lines.
The first, known as Classic, is for standard soil conditions and average stress levels. Durastar, meanwhile, is for above-average soil situations which place high demands on the working tools.
At the top end is Durastar Plus which is for extreme soil conditions and maximum stress for use by large farms and contractors.
The heat treatment of metal has a long tradition and modern machinery companies still use this process to add durability to their working kit.
Pottinger uses various hardening and tempering systems, including a modern high-temperature low-pressure carburizing plant. When hardening right through, the entire cross section of the component is hardened.
However, in order to achieve a high impact strength – especially in the case of wear parts – it is advantageous to harden only the surface which is subject to wear.
Many of the production sequences are semi-automised, which means key process measurements such as hardening temperatures, furnace atmosphere, cycle times, quenching rates and press forces are programmed depending on the component.
The result is wearing parts with hardened, wear-resistant surfaces that also have high impact strength.
Carburizing is a process applied during the heat treatment of steel.
The component is heated to a temperature of around 960C and the surface of the component is enriched with carbon.
The steel is then hardened by plunge-cooling (also known as quenching) in a polymer or oil quench and then tempered between 180 and 350C.
This process makes the surface of the steel hard and resilient, which significantly increases the wear resistance of the components.
The core remains flexible, which prevents fractures and cracks from occurring when the material is subjected to stress.
Hardening is mainly used in zones where the reduction of surface wear is a priority – such as on mould boards for ploughs, for example.
Tillage tools (such as plough shares) are armoured on the underside using a special deposition welding process. This involves welding tungsten carbide powder onto the surface of the components, a process that gives a layer of tough additional wear protection.
This strengthens the part without affecting the cutting edge or angle of soil penetration.
The uneven hard layer applied to the side facing away from the direction of travel increases the service life, but does not increase the draft (pulling resistance) of the implement.
The smooth upper surface still ensures that the soil flows across cleanly. In addition, this process has the advantage of a self-sharpening effect on the cutting edge of the wear part.
The coating technology is used especially in areas where the reduction of edge wear is a priority – such as on stubble cultivator points and reversible points for plough shares.
Finally, tungsten carbide coating adds an extra layer of toughness.
With this process the likes of power harrow tines and packer roller scrapers are dip-coated in tungsten carbide to make the surfaces even more resistant to reduce wear.