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How steel copes with continuous wear

Submitting materials to stress tests

At the new wear laboratory, wear-resistant steel grades are tested for their resilience against abrasion.

(Text: Judy Born, Photo: thyssenkrupp Steel Europe photography)

Heavy plate equals big plate, eye-catchingly big: Enormous crawler excavators and front-end loaders, mile-long belt conveyors, giant shredders, and scrap compactors. It’s the type of machinery that needs to withstand extreme mechanical stresses and aggressive wear. Heavy plate grades, such as the XAR® product range, are therefore characteristically hard and tough, and highly resistant to wear.

Materials researchers understand wear to be the progressive deterioration of a solid body’s surface caused by mechanical stress. “To put it simply: Something keeps rubbing or grinding on the material and thus removes particles from the surface,” says Dr. Christian Heet, who is in charge of the new wear laboratory at thyssenkrupp Steel in Duisburg.

First and foremost, the lab investigates the material properties of heavy plate. In addition, Heet and his team also examine other types of steel. Their work helps to determine very early on which steels are suitable for which purposes, and how to develop them further to be more resistant to wear. “When we make a recommendation, we can back it up black-on-white – we’ve got all the evidence,” says Dr. Nina Kolbe, a technical customer adviser in the Heavy Plate business unit. “That’s beneficial not just to our heavy plate customers.”

When we make a recommendation, we can back it up black-on-white – we’ve got all the evidence.

Dr. Nina Kolbe, Business Unit Heavy Plate

Material tests with synergy

The laboratory is used right across the different sales areas and for a wide range of industrial sectors. “Our results enable us to provide even better advice to customers with wear applications, and to help them select the best possible materials,” says Dr. Franz Domenic Boos from Product Management.

In the future, testing will also be adapted to match specific real-world customer requirements, enabling thyssenkrupp Steel to provide fully individual advice to its customers. The system is already being practised with Global Wear Parts Management at sister company Industrial Solutions. “Our colleagues there test rock abrasivity, while we investigate the wear resistance of the metals used to work the rock," says Heet. "It's a nice synergy effect."

Two possible test methods

Two possible test methods

How does it work? Essentially, there are two methods. Firstly, the amount of wear depends on the amount of force being exerted on the material. That’s why Heet’s team subjects its test samples to different levels of pressure. Testing with an abrasion vessel makes it possible to vary this pressure by altering the amount of abrasive material, which is usually quartz sand or gravel. The hardness of the sand and the speed at which it traverses the steel sample also affect the result. With an abrasion vessel, the real-world conditions that the material will be subjected to can be simulated very accurately.

Secondly, a so-called rubbing wheel is used to test a material’s more general wear characteristics. With this method, a lever arm pushes the test sample against a rubber-coated wheel rotating at a set speed. At the same time, sand trickles down from above and gets caught between the wheel and the sample, thus causing wear. Both of these testing methods work with dry as well as wet types of sand. “The rubbing wheel test takes between 30 seconds and 30 minutes,” says Heet. “A test using the abrasion vessel, on the other hand, usually takes three days.”

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