Related: Automotive Materials
Quiet Steel, a product of Material Sciences Corp. (matsci.com), is a tailored steel, specifically engineered to attenuate specific vibrations, thereby reducing noise. It is a sandwich material, with a 0.001-in. viscoelastic layer bonded between two layers of cold-rolled steel; the steel can be coated as required by the specific application.
The material has had some notable, highly visible applications over the years. You may recall a TV ad for the Ford F-150 from a few years back where the use of Quiet Steel—for a dash panel—was cited as an advantage of the vehicle.
Among the applications that Cliff Nastas, Material Sciences CEO, ticks off as being prime application areas, in addition to the dash panel, are floor panels, wheel wells, and cowl plenums. And the steel is being used also for oil pans, transmission covers, and engine covers.
In some regards, this may seem like old news.
But Nastas says, “Over the last few years, the use of Quiet Steel in body structures has declined.”
And the reason, he suggests, is the economic crisis that the industry went through. If you’re looking at deadening sound, then there are a whole lot of ways that it can be accomplished, from using thicker carpet backings to using liquid applied sound deadener (LASD) and mastics. All of these are low-cost means to reduce cabin noise.
Times have changed in the last few years, and with them, requirements. Every vehicle manufacturer nowadays tends to tout the quietness of its new vehicles. There is certainly a customer expectation that they’re able to hear their new infotainment system with a fidelity not marred by, say, engine noise, and that their voice recognition system will be able to understand their commands without road noise getting in the way. NVH (noise, vibration, harshness) is an area of particular concern for the OEMs.
Another change is that there is a greater proliferation of small and midsize cars. Which means that the occupants of the cabin are closer to the sources of noise than they would be in, for example, an F-150. What makes the smaller cars more challenging is that because they are smaller, there are packaging issues: OEMs are working
to keep the size of the cabins as large as possible and boast when they add half an inch here or there, so doing things like increasing the thickness of carpet backing isn’t advantageous for that effort.
And what is perhaps the biggest change, is now that OEMs are facing increased fuel economy standards, mass reduction is becoming an essential undertaking. Taking weight out is essential, but it is not being done at any cost.
So the new argument for Quiet Steel, which is not old news, is that it, says Nastas, can “offer a substantial mass reduction and in many cases a cost-save” compared with using the less expensive (as in purchase cost) materials. “When you use Quiet Steel,” he says, “you can eliminate other materials that weigh more without sacrificing the acoustical properties.”
Nastas says there have been instances where they lost the business because the material had a cost premium of $2 or so for the application, but had it been used, it could have resulted in a mass save on the order of 6 lb. He goes on to say that as OEMs are spending about $2.50 per vehicle to reduce the weight by a single pound, saving 6 lb. for $2 makes economic sense: “If there is a mass save and a cost save, it’s a home run.”
Of course, in many vehicle develop-ment programs there are the people who are working NVH over here and the people concerned with mass over there and the people concerned with budgets up there. So the need is for a more systemic approach to dealing with these issues. What’s more, Nastas admits that his company’s material “is not the answer for every body part. It is predicated on the design of the vehicle, the infrastructure of the vehicle, and what they are trying to achieve.”
According to Bilal Bizzi, MSC’s Auto-motive strategic account manager for North America, if there is early involvement during the design phase of a program, “We can do CAE [computer-aided engineering] and predict where there is the best use of Quiet Steel panels so as to avoid weight and secondary operations like applying LASD.”