Above: Wear plate is an ideal material for heavy-duty, high-impact applications like truck bodies that haul ores or aggregates. Making plate lighter increases payloads.

Steelmaker expands range of wear plate that will take a beating and stay strong

April 2018 - Several serious studies have been done and others are under way, in Asia, Europe and North America, about the impact of lightweighting components on heavy-duty commercial equipment.

“Lightweighting for freight efficiency is a critical component as it will facilitate the adoption of additional fuel efficiency technologies,” according to a 2015 report by the North American Council for Freight Efficiency. “Fleets should specify lightweighting options together with their other efficiency choices,” the study’s researchers recommended.

In an in-depth, 199-page report prepared for the European Commission’s Directorate General for Climate Action, researchers found that tractor-truck and trailer manufacturers “are increasingly introducing lightweight constructions into the market.”

Although a lightweight steel tipper (dump body) weighs around 5 metric tons compared with 4.5 metric tons for an aluminum box body, “Steel tends to be more robust and therefore more suitable for frequent tipping,” according to Climate Action’s survey and analysis of existing research.

Consumption of advanced and ultra-high-strength steel grades has been on the rise, due to their increased yield and tensile strengths. The shift from conventional steels to AHSS allows weight reductions of up to 30 percent, according to a 2013 study by the U.S. Department of Energy.

Hardox 500 Tuf plate can be used in grinding and crushing operations (above) as well as in  bulk and earthmoving vehicles.

The increased cost of lightweight materials remains a barrier to adoption for some. A supplier surveyed for the European Commission report stated that, “As a rule of thumb, OEMs and operators are looking for payback times of less than two years.” Further, equipment owners “are willing to pay up to €10 per kilogram of weight reduction. This rule applies to weight-sensitive applications such as tanker and tipper trucks.”

Producers have become more successful in changing both the perception that steel can be light, and that steel can help to curtail heavy equipment weight, thereby lowering greenhouse gas emissions in service.

SSAB, the Swedish steelmaker, recently added a new grade to its Hardox line of steels. Called Hardox 500 Tuf, the material is hard, toughened to withstand repeated heavy impacts, and hard wearing for a long service life.

Maurice Picard, technical director for SSAB Special Steels, describes the process of creating the new grade and how it functions down the supply chain.

“The process of making it is basically a plate that is rolled, then quenched through a very high efficiency roller quencher, then tempered to remove some of the residual stress. The final result is a plate that is workshop friendly. [Fabricators] can cut, bend and weld it without any issues,” says Picard. Hardox 500Tuf  has almost as high impact toughness as  Hardox 450 but the higher hardness gives you a better wear resistance and longer service life.”

The big advantage is if a customer is interested in building lighter equipment, it can use the Hardox 500 Tuf in a thinner gauge than a product that is less hard. “It is the Brinell hardness [measurement],” he explains. “Grade 450 Brinell is a standard for dump bodies and buckets, while Hardox 500 Tuf reaches a 500 Brinell hardness.”

The Hardox 500 Tuf plate is rolled in standard gauges of 4mm (5⁄32 inch) to 25.4mm (1 inch) and standard sizes of 8 feet wide by 24 feet long. “We can make 10 foot wide by 48 foot long on special orders. We are also very flexible in terms of volumes customers can take per order—one plate to a couple hundred tons.”

Proven applications

For the time being, the product is made in Oxelosund, Sweden, and exported to select North American consumers. The grade has gone through trials in Sweden and throughout Europe for dump bodies and buckets.

“This is developed for the sake of lightweighting for higher payload. With a lot of dump bodies, the end users are paid by payload so this product is beneficial for them. If you have a 1⁄4-inch-thick floor in a dump body of a medium-duty truck, Picard says, “you could go down to 3⁄16-inch. For a truck that is 20 feet long, that could be a 400-pound weight savings, and for a dump body that is 25 foot long, it is a 500-pound reduction. That is a quick way to go to a higher hardness and have a slightly longer wear life, and achieve the weight savings.”

Applications include heavy-duty mobile equipment at quarries and mines, at construction sites, yellow goods generally, including attachments, dump bodies, roll off containers and railcars—“anything that has wheels,” says Picard. The fact that the equipment builder can create a lighter product helps the end user promote and sell their services as more efficient, because of the greater payload.

“The trends in that [heavy equipment] market is to go lighter for the same wear life, and for the same weight, to work longer,” he says. With the Hardox 500 Tuf, OEMs could, of course, stay with the same gauge material they use now but realize greater durability, because the material will wear “30 to 40 percent longer at the same thickness.”

As Picard explains, “Toughness is a measure of how much impact the material can take before it cracks. The hardness is a measure of wear resistance. The 500 Tuf has both. The goal will be to produce it in North America once the market here is established.” MM