EN36C is a 3.50 % Nickel steel with Chromium & Molybdenum. It is a carburizing steel grade with very high surface strength with a soft but strong core. The material retains an incredible degree of toughness and fatigue resistance.
Case hardened steel is usually formed by diffusing carbon and/or nitrogen into the outer layer of the steel at high temperature. The carbon combines with the steel to make it nearly glass-like in its hardness. The core of the metal stays soft. This gives you a piece of metal that you cannot cut with a saw, but also will not shatter.