Effect of Controlled Rolling and Cooling on Microstructure and Properties of Cold Heading Steel Containing Boron and Titanium
The effect of controlled rolling and cooling on microstructure and mechanical properties of micro-alloyed cold heading steel 6AB-Ti and 35KB-Ti with diameter 6.5 mm was studied. The results showed that the controlled rolling and cooling process had a great effect on the microstructure and properties of 6AB-Ti than 35KB-Ti. For 6AB-Ti steel, the tensile strength value decreased from 460 to 360 MPa and the microstructure evolved from quasi-polygonal ferrite and pearlite to polygonal ferrite and pearlite when the finish rolling decreased from 920 to 850 °C (and the laying head temperature decreased from 900 to 800 °C). For 35KB-Ti steel, the tensile strength decreased from 630 to 610 MPa and the microstructure with ferrite net disappeared for controlled rolling and cooling process. The above phenomena are explained by the CCT curve of steel and the influence of boron and titanium on the phase transformation of steel.
KeywordsControlled rolling and cooling Boron and titanium Microstructure Mechanical properties CCT
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