Metallurgy really is a wonderful thing and it’s a source of constant wonder and excitement! The different properties of various materials, including our own favourite, steel, can genuinely be researched forever and the different alloys, treatments and processes to tweak and alter the properties and capabilities of each material are practically boundless.
A common practise for low carbon and alloy low steel grades is case-hardening. Also referred as carburising, case-hardening involves the diffusion of carbon onto the surface of a steel, which forces the material to form a much harder surface layer while allowing the metal at a further depth to remain softer.
Case hardening steels are commonly low carbon or alloy steel specifications with both usually achieving a 59/62 HRc after heat treatment. The low carbon steel grades (such as EN32 080M15) will achieve a core strength of about 500 N/mm² whilst the high alloyed grades such as (EN36 655M13) can achieve a core strength in excess of 1000 N/mm².
Combining wear resistance and strength case hardening steels are suitable for a wide range of engineering applications. Choosing a case-hardened steel makes sense when the conditions of usage can be variable and involve extremes that could cause untreated steels to suffer deformation. It’s particularly useful for items such as firing pins in rifles, which deal with a range of conditions, from explosive forces, high impacts, rapid heating and cooling and require high levels of reliability in uses such as the military. Surface-hardening is a reliable and expedient way of inputting a greater range of capabilities into a material without having to radically alter the processes or chemical make up of your steel.