Properties of alloy steel
With the development of science, technology and industry, higher requirements have been put forward for the material, such as higher strength, resistance to high temperature, high pressure, low temperature, corrosion resistance, wear and other special physical and chemical properties, carbon steel has been unable to fully meet the requirements.
Deficiencies of carbon steel:
(1) low hardenability.In general, the maximum quenching diameter of the carbon steel water quenching is only 10mm-20mm.
(2) the strength and buckling are relatively low.For example, s of ordinary carbon steel Q235 is 235MPa, while s of low-alloy structural steel 16Mn is more than 360MPa.S/b of 40 steel is only 0.43, much lower than that of alloy steel.
(3) poor temper stability.Due to poor tempering stability, carbon steel in the quenching and tempering treatment, in order to ensure a higher strength need to use a lower tempering temperature, so that the steel toughness is low;In order to ensure good toughness, high tempering temperature is used when the strength is low, so the comprehensive mechanical properties of carbon steel is not high.
(4) it cannot meet the requirements of special performance.Carbon steel in oxidation resistance, corrosion resistance, heat resistance, low temperature resistance, wear resistance and special electromagnetism and other aspects of the poor, can not meet the needs of special performance.
Classification of alloy steels
According to the content of alloying elements, it can be divided into:
Low alloy steel (total alloying elements less than 5%),
Medium alloy steel (total alloying element is 5%-10%)
High alloy steel (total alloying element > 10%).
According to the main alloy elements contained, they can be divided into:
Chrome steel (Cr - Fe - C)