Spanners are made from steel. Steel is an alloy (mixture) of mainly iron and carbon with small quantities of other elements.
Increasing the amount of carbon makes the steel harder but brittle (more likely to break). Adding manganese to the alloy makes it less brittle and improves its ability to be shaped with a hammer when hot.
Many spanners are made from chrome vanadium steel. Chromium and vanadium are metal elements that are added to steel to increase the metal’s strength. Chromium also increases the steel’s resistance to rusting.
The overall chromium content of chrome vanadium steel is usually between 12% and 20% while the overall content of vanadium is generally between 0.2% and 1%.
Vanadium is expensive so cheaper chrome vanadium steel products often have a very low vanadium content, as low as 0.1%. The product description of the tool should provide the standard the tool has been tested to and so give an indication of the material’s quality. Ideally it should be tested to the most recent German DIN (Deutsches Institut für Normung)standard. ASME (American Society of Mechanical Engineers) is the American standard and is also reliable.
Some high quality spanners designed for regular use, such as scaffold spanners, are made from titanium. Titanium is as strong as steel but much lighter and longer-lasting. These tools are expensive but worth the investment if your spanner is an essential part of your everyday work.