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Pros and Cons of High Strength Steel Tracks Pros and Cons of High Strength Steel


By Ben Knowing, Technical Support Director, SSAB Special Steels & Peter Falk, Heavy Transport Segment Manager, SSAB Special Steels


High Strength Steel has dramatically transformed a number of industries. Automotive body structures are both lighter and safer than was possible in the past. The capability of mobile cranes has increased ten-fold in the past few decades. Mining equipment runs longer between repairs and hauls more in every trip. All this is thanks to design improvements made possible by dramatic increases in steel performance. With this in mind, many manufacturers are working to understand whether using stronger steels is the right choice for their business. While it might seem obvious that stronger is better, there are actually quite a few factors that affect the choice of steel grade for different structures.


The main benefit of “upgrading” or using stronger steel in structural applications like trailers or lifting equipment is to increase the load carrying capacity of a structure. In many cases, an equipment designer will also choose to reduce the thickness of steel used in a structure and thereby reduce its weight. For on- road equipment, a reduction in weight directly translates into an increase in carrying capacity as total loaded weight is limited by regulations. For example, upgrading the steel used in a trailer’s structure from a yield strength of 50 ksi to 100 ksi could typically reduce the weight of these structures by about 30 percent and thereby increase the load capacity by 5 percent. As a result, the upgraded trailer can haul the same amount of cargo in 19 trips as would have originally required 20 trips to haul, with significant economic benefit to the operator.


In addition to carrying higher loads, stronger steels are better at resisting physical damage. This is due to their ability to resist higher levels of stress and elastic strain and then return to their original shape when unloaded. This increased flexibility leads directly into longer lasting equipment in abusive environments. It can also translate into secondary weight reduction opportunities. For example, dump bodies have traditionally been heavily reinforced to prevent accumulated damage from distorting their shape. When dump bodies are constructed of very strong steels, they naturally resist damage and many such reinforcements can be eliminated, reducing both weight and cost (See Figure 2).


Considering that modern steel producers now offer structural steels with guaranteed yield strength levels of 100, 130, 160 or even 189 ksi, it might seem surprising that “grade 50” steel is still quite common in structural applications. The main reasons for this can be grouped into the following areas of concern: deflection, stability, fatigue, workshop performance, cost, and availability of steel of suitable quality. Let’s address these one at a time, starting with material availability and quality.


Figure 1: Picture of a loaded crane showing the "fishing rod" effect".


Quenched and tempered steel plate with 100 ksi minimum yield strength has been around for some time, most commonly ordered to ASTM specification A514. More recently, 100ksi as-rolled steel plate has been listed under ASTM A656 and coils are specified in A1011 or A1018. European specification EN 10149-


54 March/April 2016 www.NATM.com


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