BOB Miller, Crysteel Manufacturing's vice-president of sales and marketing, said spec writers and those who work with end users typically don't spend enough time discussing why certain types of steel are better than others.
“There are particular steels — which may cost a little more — that are really going to save someone money in the long run,” he said. “If you take more time, you're starting to create value in their mind.”
In “Selecting the Best Steel for Your Truck Equipment Application,” Miller said that many people have champagne tastes on a beer budget. They want to have their cake and eat it, too. The key is to discern their expectations and their intended use.
And to do that, there needs to be an understanding of the strength measurements of steel: Brinell hardness (BHN), tensile strength, and yield strength.
Brinell hardness is a measurement of a metal's hardness or ability to resist abrasion (on a scale of 100 to 500).
“In our industry, we work in places like rock quarries, where we haul concrete and rebar, and the steel needs to have a high degree of abrasive resistance,” Miller said. “But we also build farm bodies, some of which are used to haul grain. Obviously, wheat and soybeans and corn don't have the same abrasive characteristics as rock and stone and gravel.”
The Breaking Point
Tensile strength is the maximum load in pounds per square inch that a material sample will carry before breaking or cracking — a key factor in truck frames or floors of dump bodies.
Yield strength is the point at which a material exceeds the elastic limit and will not return to its original length or shape after the stress is removed. To simplify: yield strength = dent resistance.
“We were building a new concept body that was basically designed to haul aggregate,” Miller said. “We wanted to see how the steel would perform, so we gave it to a distributor and said, ‘Take it out and see if you can beat it up.’ They were hauling rocks of over 1,000 pounds. The surface looked like someone had taken a ball-peen hammer against some type of soft material and beat knots all over it. The yield strength was being exceeded, and although the metal didn't crack a lot, it took a set and wouldn't return to the original shape.”
So which measurement matters most to your customer: abrasive applications (BHN), load-bearing applications (tensile strength), or impact applications (yield strength)?
“It could be two, or all three,” Miller said. “So sit down with your customer and talk. If you do that, you'll provide him with something that, in a lot of instances, may be slightly more money, but the value to him is going to be more rewarding because you're not going to see him back in your shop for repairs.”
Joe Paulsen, Crysteel's sales manager, described the types of steel: carbon, exotic, and corrosion-resistant.
In the carbon line, A569 is a mild steel with 36,000 psi yield strength, 137 BHN and 50,000 psi tensile strength.
When discussing AR400, or Handox (the Swedish manufacturer's trade name), he said it has 145,000 psi yield strength and 400 BHN, and 180,000 psi tensile strength.
To demonstrate the difference between the mild steel and the 400, he asked a friend with a neighboring 100-yard indoor shooting range to shoot six different types of ammunition into each from the same distance and with the same gun. The mild steel had large dimples and divots; the 400 had only slight indentations.
Exotic Steels
The exotic steels are super high-strengths with a typical yield strength of 100,000 psi or greater. Miller said the low-alloy steels with minimum carbon (brittle) were first developed by a Swedish steel manufacturer, who eliminated the carbon content and added more expensive, less popular common elements such as phosphorous and vanadium to be able to achieve strength without brittleness.
AR235 is an abrasion-resistant steel, while AR514 is a Grade B steel with 265 BHN, 100,000 psi yield strength, and 120,000 psi tensile strength. 100X, or Domex, has 250 BHN, 100,000 psi yield strength, and 110,000 psi tensile strength. Paulsen said spec writing is important because on the surface, they look the same and weigh the same, but they have vastly different performance characteristics.
A606 (or Cor-Ten), a corrosion-resistant steel, has 50,000 psi yield strength, 156 BHN, and 70,000 psi tensile strength.
“It gives you higher strength,” he said. “It's a good structural piece of steel. Once it oxidizes, it gets that thin layer of rust. In dump bodies, we struggle with that in terms of application. Your load's going to exit the dump body and continually abrade that oxidization and you're not going to get the advantage of the Cor-Ten.”
He said the food-service industry, particular in the manufacture of milk tanker trucks, gravitates toward 304 stainless steel, with 35,000 psi yield strength, 180 BHN, and 85,000 psi tensile strength.
Paulsen said if the customer's main concern is cost, then the easy choice is A569. It would be particularly applicable to a customer who is leasing a vehicle and isn't concerned with cosmetics.
If the customer is more concerned about payload and wants to maximize on every trip he makes, then the choices are A570, 100 XF, or AR400.
Paulsen said many municipalities choose between AR235, A514, AR400, or AR500 if they are hauling broken curb and gutter that will be abrasive and thus require a higher BHN.
A606, 304, 409, and 1010 stainless steel are suitable for municipalities that want a one-unit-fits-all use for hauling rock salt, calcium chloride, ash, waste, and rendering services.