Supplier Believes Lightweight Steel Has A Place In Light-Duty Pickups
Though Ford is going all in on aluminum for its upcoming F-150, with General Motors following suit soon after, one supplier believes lightweight steel can be just as effective as the alloy best known for holding beer and keeping turkeys juicy in the oven.
Luxembourg-based ArcelorMittal is offering two such solutions for helping light-duty pickups meet ever-tightening CAFE mandates, going so far as to rebuild a 2009 model using newer steel components for a 23 percent reduction of 384 pounds in comparison to a similar 2014 model.
In contrast, the 2015 F-150 gains a 732-pound loss over the outgoing 2014 version on the truck scale, a result of extensive use of aluminum in the body panels throughout the new truck.
No matter the solution, both offerings would likely find a place at the table as every automaker fights to hit a CAFE-mandated fleet average of 54.5 mpg by 2025. That said, aluminum may be going up to bat more times than lightweight steel alloys in order to meet the target.
My guess is it is not about the 5% strength to weight difference, but the corrosion resistance for the salt belt market. Yes, you can use thinner high strength light weight steel, but then your truck will rust a lot sooner than an aluminum truck of the same strength because 1) the aluminum truck will have thicker metal body for the same strength and weight, and 2) aluminum itself is more corrosion resistant than steel.
So..I and going to ask this due to the fact that I dont know...So maybe some of you guys in the know will enlighten me. How come no one is using Nano Steel or Nano Aluminum? Or is High strength steel the same thing? I read about these about four years ago and they both seemed promising.
As for "strength", there are actually four measures that are correctly called "strength", and then there's stiffness which is often incorrectly called "strength". 1) Tensile strength is the stress at which the material will part altogether. (Pull on a rubber band till it snaps; that's the tensile strength of the material.) 2) Yield strength is the stress at which the material will deform permanently. (Bend a paper clip.) 3) High cycle fatigue strength is the stress level at which a component can be flexed back and forth (at a stress level well below the yield strength) without failing for an essentially indefinite period of time. 4) Low cycle fatigue is the stress level at which a component can be flexed back and forth (at a stress level very close to yield strength, or even with yielding deformation) without failing for a defined number of cycles. 5) And finally, stiffness is the relationship between force and deflection for stress levels below the yield strength. Stiffness of all steels is essentially the same. Stiffness of all aluminum alloys is essentially the same, and considerably lower than that of steel. This means two steel components (or two aluminum components) of the same cross section subjected to the same load, below the yield stress, will deflect the same amount. Yield strength, tensile strength, low cycle and high cycle fatigue strength are all highly variable among alloys of the same material (and for many of those alloys they are also highly dependent on processing) and are highly variable between different materials. It is not a complete statement, for example, to say "steel is stronger than aluminum." What alloy? How was it processed? There are many aluminum alloys that are stronger than many steel alloys, if you are considering one or two measures of strength. There are many different types of components in an automobile body. Here are some examples of trade-offs that would affct them. 1) Body panels. They need to be made from a ductile alloy (low carbon steel, low alloy Al - low yield strength) so they can be easily formed with acceptable die wear. But they need to have a sufficient combination of yield strength and thickness, plus shape, to resist denting. Body panels that are involved in crashworthiness need to have sufficient yield strength for their function. They are usually spot welded, which is a process well-developed for low carbon steel, but not so much for Al. Tensile strength would be an issue in forming possibly, but I can't imagine tensile strength or fatigue strength being much of an issue in operation. Steel tends to corrode more than Al, but watch out for galvanic corrosion. 2) Frame rails. There's a lot less deformation in production, usually, so higher strength materials can be used. Tensile strength is probably not an issue. I think yield strength could be an issue, both for crashworthiness and for overloading conditions. High cycle fatigue could definitely be a concern. And so on. I'm sure my quick comments have left out several factors that have to be considered, never mind cost considerations. So this is why I get annoyed when people make statements like "BS. Why didn’t they offer that up to Ford before they went aluminum?" The decision to go away from a well-proven material in an application like this is extremely complex, and sometimes they make the wrong choice. But it's never the "we decided in ten minutes over drinks to change materials" kind of process that some people seem to imagine.
The really big problem is in the rust belt all these thin metal trucks will be eaten alive, the lifespan and durability will be greatly reduced compared to a truck from the eighties . I already see newer trucks getting frame rust even trucks from the ninties have severe frame rot, which you never seen in the older trucks the frames would outlast the truck.