Question: What is the strongs steal

Angus Cook answered on 19 Jun 2016:

This is a tough question, partly because I don’t know ALL of the types of steel that there are. There are also some different ways of testing how ‘strong’ a steel is. The way I’m talking about it ‘Ultimate Tensile Strength’, which is like a measurement of how much pulling a steel bar can take before it starts to break. But you can also talk about how good a material is at being squashed, or how good it is at being twisted.

The strongest alloy of steel that I found that was best against pulling forces is called ‘X5CrNiCuNb16.4’. It’s twice as good as other common steels (i.e. it can take twice the pulling force before it starts to break).
It’s got some other names too though, including ‘Grade 630’, and ‘UNS S17400’ (we use lots of different names, because lots of different countries all have their own systems of naming). I’m going to keep calling it Grade 630 for now, because that’s the easiest to read.

Grade 630 is an alloy, mostly made of iron with a little bit of carbon (that’s what makes it a steel), but it’s also got some chromium, some nickel, some copper and some niobium added as well. This mix of elements is what helps give it its strength.