Steel in the Kart and others applications

Steel is the name commonly given to an alloy made by iron and carbon in addition to other elements that allows to trim material characteristics to the particular needs of the component that will be realized. Carbon, usually present in a percentage lower than 2.11% (beyond we are talking about cast iron, a material that is different in terms of characteristics and machinability), is present in the lattice structure of the material as iron carbide and, is able to block the motion of the dislocation, that are the primary material failure causes.
The add of carbon allows then to obtain better mechanical properties than that of pure iron, making this material suitable for a large number of applications. Another relevant factor is the relative low cost of the material, that makes steel one of the world’s most used construction materials each year being produced over five millions of tons.
Go kart chassis are generally made using low-alloyed steels, that are steels that contains, beyond carbon (in percentage ranging between 0.2 and ), some alloying elements that improve mechanical strength, quench penetration, tenacity and so on. Low-alloyed steels are characterized by an higher strength-to-weight ratio then normal carbon steels but they also have an higher price.
They are particularly indicated for mechanical components subjected to high dynamic stress.
The most used alloy elements are Chromium (Cr), Molibdenum (Mo), Manganese (Mn) and Nickel (Ni).
In particular, Chromium improves steel hardness and elastic limit. In percentages higher than 10% it makes the steel stainless, and resistant to atmospheric and chemical agents.
Molibdenum is used to enhance quench penetration and then to give a better efficiency to the quench process, in a similar way than with Manganese, that also improve hardness and wear resistance. Nickel is instead used to for its effects on the thermal dilatation coefficient, that is substantially reduced by the presence of this element.
From a mechanical point of view, the better steels are the Nickel-Chromium-Molibdenum that, with an ultimate tensile strenght of 1200 N/mm² are largely used for gears, cranks, connecting rods and motor components.
For the manufacturing of kart and bike chassis, but even for race car roll cages, chromoly (Chromium-Molibdenum) are the most used steels, for their very good resistance and weldability properties. One of the most diffused is the 4130, of which tables 1 and 2 depict main mechanical properties.


Ing. Fabio Renzi
TVK Project s.r.l.
Motorsport software and consulting
Via Ignazio Guidi, 44
00147, Roma

renzi@ing.uniroma2.it
fabio.renzi@tvk-project.com
www.tvk-project.com

Phone +39 0672597136