Think of a Formula 1 racing car and you invariably think of a machine that’s made almost entirely from carbon fibre. But that’s only partially true. While carbon fibre has been rightly acknowledged as the wonder material that’s enabled the sport to build safer, faster and ever more sophisticated cars, it is just one of many materials used by F1 teams.
The heavy CNC machine shops, equipped with the finest tooling machines, work extensively with titanium, aluminium and stainless steel. Why? Because sometimes carbon-fibre components don’t offer a better solution than a well-machined metal part.
F1 teams use titanium because its strength-to-weight ratio makes it an incredibly versatile material; aluminium is heavier, but still comparatively lightweight, and also very strong; stainless steel is heavier, but it has incredible wear-resistance and strength characteristics.
As always, the purpose of the component dictates the material in use. Even in a sport where carbon-fibre is so prevalent, the CNC heavy machine shops are busy during winter months when the whole teams are focused on building cars for new racing season.
The range of materials which are used to make the components of an F1 racing car is truly impressive:
-Low pressure cast aluminium alloys are used for engines and sometimes gearboxes. Radiators use aluminium too.
-Magnesium alloys in die cast or thixomolded spec for small parts.
-Copper for cables. Neodymium for magnets in servo motors. Lithium in batteries.
-Earlier F1 constructors used depleted uranium for ballast, but it got banned due to cost reasons and now teams use proprietary heavy metal formulae.
-A bunch of engineering thermoplastics and thermosets such as LCP, PEEK, silicon, synthetic and natural elastomers for insulation and gaskets.
-Acrylics for paint.
-Confor foam for head rests.
-Stainless steel for exhausts.
There is a wide range of materials from which racing exhausts are made today. The choice depends mostly on the budget, although some of the more expensive materials available aren’t used because they either aren’t mature enough or engineers haven’t figured out how to use them yet.
Whilst there are a lot of exhaust systems still being made of steel, for a number of reasons, it isn’t as widely favoured as it once was. The obvious one is that it corrodes very easily. Welding carbon steel to stainless steel is a good way to make the metal corrode, even quicker than normal carbon steel would. One motorcycle manufacturer discovered this very costly mistake during the production of motorcycles. If you are going to be welding different materials together, you should be sure of materials compatibility beforehand.
The most common material choice for racing exhausts, although not in F1, is probably stainless steel. Austenitic stainless grades such as 304 are a popular choice for all manner of exhaust systems for everything from tuned road cars and motorcycles through club racing to Le Mans and beyond. This material has a good corrosion resistance compared to carbon steel, but it is not so easy to work, owing to the rate of strain hardening. If severe bending is required, it may be necessary to stress-relieve the material by annealing after bending process. There are other stainless materials used commercially such as 441 which is a ferritic grade characterized by a good degree of corrosion resistance coupled with greater formability than the austenitic grades. Austenitic grades of steel also suffer from galling, which is a micro-welding process where joints between similar or identical materials with sliding movement become cold-welded to each other with very little force applied, and this phenomenon is not limited to exhausts, or to stainless steel.
Titanium is very widely used for exhausts on motorcycles, although Formula One has largely shunned this material, and there is a good reason for this. In general, motorcycles support their exhausts with more than one support. Their tubes are obviously fixed to the engine at the cylinder head, but they also benefit from further supports either underneath the engine, or close to the end of the exhaust system, or possibly both. This largely mitigates the bending stresses which would be present if the extra supports weren’t used. The main advantage of titanium is its low density. With around 40% lower density than stainless steel, the advantages are obvious, especially for motorcycles. These exhausts are made from standard titanium materials, although some with increased high-temperature capabilities are available and have been tried in Formula One, although without success. In the same way that sports car teams support their exhausts (especially those using turbocharged engines) to reduce the bending stress at the head, this technique could be employed to make titanium a realistic possibility for Formula One. Let’s not forget that the turbo Formula One engines used exhaust supports so there is a precedent for this measure. There seems to be little reason why a titanium tailpipe couldn’t be used, and perhaps some Formula One teams already do this.
Now we turn to Formula One, and the materials of choice here are the high-temperature ‘super-alloys’ containing lots of what we often hear called ‘strategic elements’. These elements which are used by the military and coincidentally are the ones that attract the ever-unpopular alloy surcharge, namely Nickel and Chromium. Inconel 625 is the popular choice, although there are some good alternatives available with potentially better performance, and certainly some teams already use these alternatives, with others looking at newer superalloy materials.
There is some evidence that non-metallic materials have been tried and tested for some exhaust components, although this seems to have been limited to small-scale testing in Formula One. There is no doubt that the material in question is impressive, and it seems to have a natural niche in aerospace and defence markets.
Stainless Europe sells over 20 grades of stainless steel, including those that can be successfully used in the production of racing car parts.
