With the development of science, technology and industry, higher requirements have been placed on materials, such as higher strength, resistance to high temperatures, high pressures, low temperatures, resistance to corrosion, wear and other special physical and chemical properties. Carbon steel can no longer fully fulfil requirements.
Disadvantages of carbon steel:
(1) Low hardenability. Under normal circumstances, the maximum hardenable diameter of carbon steel liquid quenching is only 10mm-20mm.
(2) The strength and yield ratio are low. For example, the σs of ordinary carbon steel Q235 steel is 235MPa, while the σs of low alloy structural steel 16Mn is more than 360MPa. The σs /σb of 40 steel is only 0.43, which is much lower than alloy steel.
(3) Poor tempering stability. Due to the poor tempering stability, when carbon steel is quenched and tempered, in order to ensure higher strength, a lower tempering temperature needs to be used, so that the toughness of the steel is low; in order to ensure better toughness, a high tempering temperature is used The strength is low at high temperatures, so the comprehensive mechanical properties of carbon steel are not high.
(4) Unable to meet special performance requirements. Carbon steel is often poor in oxidation resistance, corrosion resistance, heat resistance, low temperature resistance, wear resistance and special electromagnetic properties, and cannot meet the needs of special performance.
(3) Poor tempering stability. Due to the poor tempering stability, when carbon steel is quenched and tempered, in order to ensure higher strength, a lower tempering temperature needs to be used, so that the toughness of the steel is low; in order to ensure better toughness, a high tempering temperature is used The strength is low at high temperatures, so the comprehensive mechanical properties of carbon steel are not high.
(4) Unable to meet special performance requirements. Carbon steel is often poor in oxidation resistance, corrosion resistance, heat resistance, low temperature resistance, wear resistance and special electromagnetic properties, and cannot meet the needs of special performance.
