| China's steel materials need to develop in the direction of high quality and high added value.Microalloyed steel is a kind of high-performance steel.Microalloying elements are added on the basis of carbon or low-alloy structural steel.Compared with traditional steel,the production process is shortened,the production cost is reduced,and the performance is improved.It is a high-quality new steel grade that is low-carbon,environmentally friendly,energy-saving and efficient.In order to further improve the properties of microalloyed steel and broaden the application range of non-quenched and tempered steels,this paper adopts the method of microalloying elements combined with heat treatment process to study the effect of microalloying on the structure and properties of steel,and analyze the mechanism of microalloying.Adding trace alloying elements V and Ti to medium carbon manganese steel,and three alloy steels with different compositions are designed to form three reference groups.The orthogonal experimental scheme was designed with the quenching and pre-cooling temperature,tempering temperature and tempering time as variables,and the microstructure observation,hardness test and mechanical property test were used to characterize the structure and performance of the material.Analyze the effects of V,Ti elements and heat treatment process on the structure and properties of medium carbon microalloyed steel.After adding 0.089% V(mass fraction)to medium carbon manganese steel,improved hardness and tensile strength,reduced plasticity and toughness.The hardness of V-containing microalloy steel reaches the maximum when the quenching and precooling temperature is 900?,the tempering temperature is 200?,and the tempering time is 1h,which is HRC53.4.When the quenching and pre-cooling temperature is 1000?,the tempering temperature is 200?,and the tempering time is 3h,the tensile strength reaches the maximum,which is 2033.6MPa.When the quenching and precooling temperature is 900°C,the tempering temperature is 200°C,and the tempering time is 1h,the plasticity and toughness reach the lowest.After Ti is added to V microalloyed steel,the microstructure is more uniform and finer,and titanium has an obvious effect of refining grains.The strength increased slightly,the plasticity and toughness increased significantly,the reduction of area increased by an average of 81%,the elongation after fracture increased by an average of 12%,and the impact energy increased by an average of 70%.Under the combined action of V and Ti,the hardness and tensile strength of the microalloyed steel have been improved.When the quenching and pre-cooling temperature is1000?,the tempering temperature is 200?,and the tempering time is 3h.The hardness of the alloy steel is HRC51.5,the strength is 2239 MPa,which is the best in this experiment.The quenching and precooling temperature is 900?,the tempering temperature is 600?,and the tempering time is 2h.Under the technological conditions,the vanadium-titanium microalloyed steel has the best plasticity,with a reduction of area of 52.9% and an elongation of 13.8% after fracture.When the quenching temperature is 950?,the tempering temperature is 600?,and the tempering time is 3h,the toughness of the vanadium-titanium microalloyed steel is the best,and the impact energy is 98.8J.The paper has 61 figures,50 tables,and 67 references. |
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