Choosing Steels

Stub Mandrel offers some advice on choosing the right steel for the job

- Stub Mandrel

One of the first challenges for anyone taking up engineering as a hobby is making the right choices of materials. Often the easy way out is to simply choose materials that other people have used successfully for similar applications, but sooner or later you will find yourself wanting to make better informed decisions. A particularly confusing area is choosing between different steels. You will often see descriptions like ‘bright mild steel’, ‘black bar’ or ‘case hardening steel’. While this may help you get something more or less right, it helps to understand the more formal designations used by steel stockholders and which you may come across in articles from time to time.

There are two systems you will probably come across in the UK. The longest standing are the ‘Emergency Numbers’. These were established during the Second World War to promote consistency in the products of different steel manufacturers. Clearly if you wanted steel for making guns or armour in wartime, you wanted to be able to specify the composition whatever the source, rather than having to work out which of each manufacturer’s range of products would suit. These numbers all take the form of the letters EN followed by a number for the composition of the steel and sometimes a letter to show how it has been heat treated. In very rough terms the higher the number the higher the carbon content of the steel.