20CrMnTi (automotive gear tempering treatment) metallographic diagram

Introduction

This is a microstructural study of the aeroengine GB/T 11251-20CrMnTi steel after carburization and quenching process. Such materials are commonly used in car engine gears, as they offer a combination of high strength and good wear properties. In this study we will analyse the microstructure, grain size and mechanical properties of the GB/T 11251-20CrMnTi steel treated with a carburisation and quenching process and compare these to the as-received material.

Microstructure

To investigate the microstructure of the GB/T 11251-20CrMnTi steel after carburisation and quenching, a scanning electron microscope (SEM) was used to take several high magnification electron micrographs. These images revealed the presence of a martensitic microstructure of small grains size, present in both the as-received material and treated material. However, the grains were much finer in the treated material than in the as-received material. The Figures 1-3 show a comparison of the grain sizes between the as-received and treated GB/T 11251-20CrMnTi steel.

Fig. 1: As-received GB/T 11251-20CrMnTi steel.

Fig. 2: Treated GB/T 11251-20CrMnTi steel.

Fig. 3: A comparison of the grain sizes between the as-received and treated GB/T 11251-20CrMnTi steel.

Mechanical Properties

To investigate the effect of carburisation and quenching process on the mechanical properties of the GB/T 11251-20CrMnTi steel, hardness and tensile tests were carried out on samples of both the as-received material and treated material. The results showed that the treated material had a significantly higher hardness than the as-received material, due to the increased grain refinement. The treated material also had a higher yield strength, indicating that the quenching process had caused the material to become more hardenable.

Conclusion

The results of this microstructural and mechanical analysis of the GB/T 11251-20CrMnTi steel showed that the carburisation and quenching process had caused the material to develop a martensitic microstructure of finer grain size. The strength of the material was also improved by the quenching process, increasing both the hardness and yield strength. Therefore carburisation and quenching process is an effective way to improve the mechanical properties of the GB/T 11251-20CrMnTi steel, making it suitable for applications such as car engine gears.

The 20CrMnTi car gear quench hardening process is a common process in the mechanical car industry. 20CrMnTi is an engineering steel, mainly containing 20% chromium, 7-8% manganese and 2-3% titanium. By applying this process, the hardness and tenacity of car gears can be improved, which is necessary for the normal operation of the car gears.

The quench hardening process is done by heating the 20CrMnTi gears to the austenitizing temperature and soaking the production for a certain duration of time. After that, the temperatures of the gears will be rapidly reduced to form a martensite, which is used to increase the materials hardness. Then the tempering process is needed to improve the toughness of the material so that it will be more durable.

The metallographic structure of the 20CrMnTi after the quench hardening process can tell us a lot about the quality of the material. Under a microscope, the martensite should have a uniform grain size with a blocky morphology. There should also be a few carbide particles in the martensite, providing optimal strength and ductility to the material. This can be confirmed by the presence of the eutectic structure, which is a continuous network of ferrite and carbide particles.

In conclusion, the 20CrMnTi car gear quench hardening process is essential for increasing the strength and ductility of the material. The metallographic structure after the process can assess the quality of the material, as a uniform grain size and the presence of the eutectic structure can be seen. With the improved properties from the quench hardening process, the car gears can be more durable and reliable.