Adding carbon to steel makes it harder and stronger. Is this true for all metals? Could you add carbon to titanium or vanadium to make them even harder and stronger?

Asked by: Bill Devenport

Answer

Adding carbon to iron to make steel does make it stronger and tougher, up to a point. Then it will get stronger but less tough (ie like cast iron). Carbon strengthens iron by distorting its crystal latice. This distortion is similar in effect to work hardening. It is unfortunately a very complex effect and depends on how the steel is heat treated and exactly what percentage of carbon is added (<4% by wieght normally). It is not true of all metals.

The effectiveness of adding carbon to strengthen metal depends on the latice spacing, crystal structure and possible chemical effects between the metal and the carbon. Titanium and vanadium might be hardened by carbon, but might be made brittle or even softer by it. There are a variety of other ways to harden metals. Adding copper to aluminium hardens it quite a lot. Metallurgy is an interesting field and any basic text on the subject should answer your questions in more than enough detail.
Answered by: Mark Bruckard, B.S., Physicist, Canberra, Australia