Effect of Ultra Fast Cooling on the Alloy Cost Reduction of the X80 Pipeline Steel

Abstract

The microstructures and mechanical properties of X80 pipeline steels produced by both novel ultra fast cooling and conventional-accelerated continuous cooling modes are investigated. Results showed that different levels of Mo addition had a remarkable effect on the microstructures and mechanical properties of the investigated pipeline steels. The proeutectoid ferrite and pearlite formation is inhibited in the high-Mo steel and acicular ferrite is obtained over a wide range of cooling rates, whereas the dominant acicular ferrite microstructure can only be obtained when the cooling rates reach up to 5 C s-1. Very similar microstructures and mechanical properties are obtained in the low-Mo steel produced with ultra fast cooling and in the high-Mo steel produced by the conventional-accelerated continuous cooling. It was proved by simulation and industrial trials that high-strength low-alloy steels such as pipeline steels, can be produced using the novel ultra fast cooling which also reduce alloy cost. Very similar microstructures and mechanical properties are obtained in the low-Mo steel produced with ultra fast cooling and in the high-Mo steel produced by the conventional-accelerated continuous cooling. It is proved by simulation and industrial trials that high-strength, low-alloy steels such as pipeline steels can be produced using the novel ultra fast cooling which also reduces alloy cost.