Low-carbon bainitic steel has been widely used in various important industrial fields of the national economy due to its superior mechanical properties and welding properties, and low manufacturing cost. However, due to the late development of this type of steel, the problems of steel toughening and microstructure control have not been well solved, which has caused certain difficulties in the development and use of this type of steel.
1. Test materials and methods
The test material is a forged low-carbon bainitic steel with a yield strength of 785MPa. The steel is normalized, quenched and tempered. By adjusting the tempering temperature, the test steel is tempered at the following temperatures: 570℃, 600℃, 630℃, 660℃. The heat-treated test steel is processed into specimens, and the mechanical properties and metallographic structure of the specimens are tested to study the influence of different tempering temperatures on the microstructure and properties of the test steel.
When the tempering temperature is between 570 and 630 °C, the yield strength and tensile strength are between 995 and 716 MPa and 1077 and 804 MPa. When the temperature rises to 660 °C, the yield strength and tensile strength decrease a lot. With the continuous increase of tempering temperature, the yield strength and tensile strength of the test steel gradually decrease. The elongation is not obviously affected by the tempering temperature, but it can be seen from the image that the elongation gradually increases with the increase of tempering temperature. The impact toughness shows an upward trend with the increase of tempering temperature.
Mild Steel Pipe
