Heavy Metal - Why blade materials matter

In a previous post, we learned that our ancient ancestors used iron to fashion their blades, which they first discovered in-of all places-meteors that fell out of the sky. But we have come a long way since then and nowadays, the metal we use has a less mysterious origin. Namely, steel. Which is, in essence, a combination of iron and carbon.

What is your purpose?

When selecting your steel, you have to bear in mind the ultimate purpose of the blade. What is it for, exactly? Various other elements can be added to enrich the "recipe" of the steel, depending on its desired use. These elements include chromium, molybdenum, vanadium, nitrogen, and sulphur.

There are five key properties that decide which elements are included and indeed, the manufacturing process to be applied.

The all important properties

1. Hardness

This speaks of the blade's ability to resist becoming deformed when subjected to force or stress. It relates directly to the strength of the knife and is measured using the Rockwell C scale

2. Wear Resistance

Your knife will not be fit for purpose unless it can withstand damage. Resistance to both abrasive and adhesive wear can be significantly influenced by the chemistry of the steel used. Steels with larger carbides will usually wear better. 

3. Toughness

This property differs to hardness in that it refers to the ability of the steel to resist chips or cracks. As a general rule, the harder the steel, the less tough it is likely to be. So a happy medium has to be struck!

4. Corrosion Resistance

Can your blade withstand rust? Obviously, a resistance to such corrosion is desirable. However, to achieve such a high resistance, you might have to sacrifice on edge performance. So again, a balance must be sought.

5. Edge Retention

Just how long will your knife be able to maintain its sharpness? How much will you be able to use it before it starts to blunt? A crucial factor, I think you will agree. 

What exactly is my knife made from?

So now you've purchased your knife. From what type of steel is it most likely to be constructed?

There are three broad categories:

• Tool Steels

As the name implies, these are used in cutting tools. They are a very popular choice and tend to be carbon steels with additional alloying elements, which often increase the steel's resistance to corrosion. 

• Carbon Steels

If you've purchased a survival knife or a machete, the chances are that this is what your blade is made from. Carbon steel is used where durability an toughness are important. It is vital that proper heat treating is used during the manufacturing process, to avoid the knife being either too brittle or too soft. Carbon steel can, unfortunately, be prone to rusting.

• Stainless Steels

This category is much better at resisting rusting, which is mainly due to the addition of chromium, (at least 13%). It is the most popular steel used for EDC knives. 'EDC' stands for 'Every Day Carry'. So if you have a pocket knife that you typically have about your person-something that is lightweight, compact and often multi-functional-the chances are that it is made from stainless steel. Again, there is a trade off involved, as the better resistance to corrosion usually comes with inferior toughness.

Of course, knives can be made from materials other than steel, such as cobalt and titanium alloys, ceramics, obsidian and even plastic.

If you are in any doubt, just ask your friendly knife maker ... !