Introduction
34CrMoA steel, a kind of low-alloy steel, is a type of colored steel in the form of ingot and has high strength, large plasticity and excellent hardenability. It is one of the most widely used steels in machinery industry.
Historically, 34CrMoA steel, or alloy true steel named as bi-alloy, was developed in the end of 80s as a necessary modification for the development of large-scale components with good mechanical properties. It is also used to manufacture high-end hot-rolled steel slabs and steel billets. A part from these, the 34CrMoA steel can also bear its part of bearing the load in automobile parts, railway vehicles and other high-end machineries.
The 34CrMoA steel includes low carbon count and low alloy content, which helps in achieving high strength and ductility at elevated temperatures as compared to its unalloyed counterparts. 34CrMoA also proves to be sympathetic towards multiple thermo-mechanical treatments such as quench and tempering. This provides additional strength gains over other conventional alloys.
The important features of the alloyed (34CrMoA) steel are its light weight, good fatigue characteristics, corrosive properties and very low thermal conduction losses. Due to low carbon levels, fine-grained structures are achieved. Faultless welding surfaces and improved fatigue strength by almost three times as compared to plain carbon steels are also worth noting.
Microstructure and Non-Metallic Inclusions
The microstructure of 34CrMoA steel is built with several elements such as bainite, ferrite and netting structures. The ferrite is made up of an oxide or oxide-carbon matrix and is a slow-cooling phase of 34CrMoA steel. The orientation of the crystal grains in ferrite results in the increased mobility of atoms, hence giving the steel a high yield strength and extreme wear resistance.
Non-metallic inclusions or particles such as calcareous particles or sulphide, silicate-based particles, SiC particles, and other inorganics are present in the alloyed steel. These type of inclusions can be found in large numbers and can greatly reduce the fatigue strength and mechanical resistance of the alloyed steel, leading to weaker products.
Heat Treatment
The heat treatment of the alloyed steel usually involves controlled heating and cooling of the 34CrMoA steel, so that the desired mechanical properties can be developed in the alloys, taking away some of the undesired features.
The most commonly used heat treatments of the 34CrMoA steel are normalizing, annealing, quenching, and tempering. Normalizing involves reheating the bar up to a temperature just above the upper critical temperature and then cooling it in air. This is done to achieve a homogeneous structure. Annealing is performed in order to obtain a soft material, quenching is done for increased strength and toughness, while tempering is performed to improve the flexibility and ductility of the steel.
Conclusion
In conclusion, 34CrMoA steel is a type of low-alloy steel that is used in a variety of industries, such as automotive and railway vehicles. This alloyed steel has a low carbon count and low alloy content, allowing it to attain high strength and ductility. It is also sympathetic towards multiple thermo-mechanical treatments. The microstructure of the alloyed steel includes ferrite, bainite, and netting structures. Non-metallic inclusions such as calcareous particles or sulphide and silicate-based particles can be found in large numbers and can weaken the steel. The various heat treatments for the alloyed steel includes normalizing, annealing, quenching, and tempering.
