The so-called high-strength steel, a good combination of strength and toughness steels. Low-alloy structural steel, quenched and tempered with good mechanical properties. The tensile strength σb> 1200MPa, called high-strength steel; their tensile strength σb> 1500MPa, known as ultra-high-strength steel.

Ultra-high-strength steel, depending on how much of its alloy content, can be divided into the ultra-high-strength low alloy steel (alloy content is not more than 6%), ultra-high-strength alloy high strength steel and high alloy steel.

High-strength alloy steel containing an alloying element chromium steel, nickel steel, manganese steel; chrome-nickel steel, chromium, cutting wheel,manganese steel, chromium molybdenum steel alloy steel containing two alloying elements; containing three or more alloying elements. The high-strength alloy steel chrome manganese silicon steel, chrome-nickel-tungsten steel, chrome-nickel-molybdenum steel, chromium-manganese-titanium steel, chromium, manganese molybdenum vanadium steel.

Original strength and hardness of the high-strength steel and high strength steel is not high, but a higher strength can be obtained after quenching and tempering treatment, hardness between of HRC30 ~~ 50.

There is a certain relationship between the tensile strength and hardness of the steel. In general, the hardness increases strength along with it, but can not say that is the high hardness steel of high strength steel. The so-called high-strength steel and ultra-high-strength steel, the comprehensive performance. Hardened steel hardness is high, but can not be called a high-strength steel and ultra-high-strength steel, because of its overall performance is not good, almost no plastic toughness is very poor, and only as a wear-resistant parts and abrasive tools.