Metallographic diagram of 65Mn spheroidizing annealing

The heat treatment of 65Mn ball is very important for its mechanical properties. In this paper, a simplified heat treatment process of ball annealing and microstructure of 65Mn steel after this heat treatment was studied.

The 65Mn steel used in this study was provided by a local company. The chemical composition of 65Mn steel is shown in table 1. Before heat treatment, 65Mn steel rods were cut into a certain shape, then ground and cleaned.

The heat treatment of 65Mn steel involves three steps: homogenization annealing, homogenization cooling and ball annealing. Firstly, homogenization annealing was performed by heating the 65Mn pieces at 890℃ for 8 hours and then cooling in furnace at a rate of 20℃/min. After homogenization annealing, one batch of 65Mn steel was ball annealed at a temperature of 740℃ , preserving for 2 hours and cooled in air.

The hardness and microstructure of the 65Mn steel ball annealing were tested by Rockwell hardness tester and optical microscope, respectively. Figures 1 to 3 show the microstructure of the 65Mn steel ball annealing and hardness before and after the heat treatment, respectively. It can be seen that after the ball annealing, the ferrite and pearlite microstructure of 65Mn steel has been transformed into a mixture of ferrite and carbide. The hardness of 65Mn steel has been decreased from 189HBS before the heat treatment to 141HBS after the heat treatment. This is because the ball annealing can effectively reduce the hardness of 65Mn steel, improve its plasticity, and enhance its comprehensive mechanical properties.

In conclusion, 65Mn steel can effectively reduce its hardness and improve its comprehensive mechanical properties by ball annealing. It is a kind of effective heat treatment process for 65Mn steel. 65Mn steel should strictly control the homogenization annealing and ball annealing process in order to more effectively improve the comprehensive mechanical properties of 65Mn.

Table 1 Chemical composition of 65Mn steel (%)

C: 0.65

Si: 0.17

Mn: 0.90

P: 0.020

S: 0.033

Figure 1 Microstructure of 65Mn steel before ball annealing

Figure 2 Microstructure of 65Mn steel after ball annealing

Figure 3 Hardness of 65Mn steel before and after ball annealing

ASTM A565 (SAE 65) Ball Bearing Steel Introduction

ASTM A565 (SAE 65) is a ball bearing steel, also known as SAE 65 or ASTM A565 grade 65. It is a commonly used steel in ball and roller bearings, as well as automotive components. This grade of steel is known for its excellent mechanical properties, such as high tensile strength, wear resistance and good formability.

The chemical components of ASTM A565 steel depend on the grade and manufacturer, but the alloy generally contains carbon, manganese, silicon and molybdenum. The carbon content ranges from 0.60-0.90%, manganese is 0.85-1.25%, silicon is 0.15-0.4%, and the molybdenum content is 0.45-0.75%. ASTM A565 grade 65 is classified as a heat treatable steel, although it is not a heat treatable steel spur gear because of its low hardness.

ASTM A565 (SAE 65) ball bearing steel is usually produced in the annealed state, meaning that it has not been heat-treated. Once formed into a finished product, it may be heat-treated to achieve a higher hardness and additional strength, and must then go through a process called tempering. This is done to soften the steel, remove any residual stresses and improve its overall toughness.

The heat treatment process for ASTM A565 steel grades involves austenitizing, quenching, and tempering. Austenitizing involves heating the steel to a very high temperature and then cooling it rapidly. Quenching then follows by rapidly cooling the steel with a liquid, oil, gas or air to produce martensitic grain structure. Tempering is the last step, in which the steel is heated to a lower temperature to soften it and eliminate any residual stresses.

In conclusion, ASTM A565 steel grades are known for their excellent mechanical properties, such as high tensile strength and wear resistance, making them suitable for a variety of uses. The steel is usually supplied in the annealed state and can be heat treated to increase its hardness for improved strength. The steel grade is a member of the heat treatable family and is produced through a combination of austenitizing, quenching and tempering steps.