| In recent years,oil and gas exploration has been acute with the growing global demand of oil and gas resources.The depth and difficulty of drilling increases,and the requirements of the mechanical properties of oil casing steel continuously increase.At the same time,cases of corrosive media in oil and gas fields causing damage to oil casing increases,the oil casing steel need better corrosion resistance.Heat treatment is an important means of improving material properties and is widely used in the production of steel materials.Through the appropriate heat treatment,the best cooperation between mechanical properties and corrosion resistance is sought,which is of great significance for the production and application of oil casing steel.This subject first studied the effect of quenching temperature on the microstructure and properties of 25Cr2 MoVA steel,and determined the best quenching temperature.After 25Cr2 MoVA steel specimens were quenched at the best temperature,the effect of tempering temperature on the microstructure and properties of 25Cr2 MoVA steel was studied to determine the best tempering temperature.It found that the highest micro-hardness was 553 HV which sample quenched at 910?.Quenched in the temperature range of 870?~990?,with the increase of quenching temperature,tensile strength increased from 1246 MPa to 1548 MPa,impact toughness decreased from 132 J to 49 J.After quenched at 910?,the corrosion tendency of the material is the lowest.After quenched at 910?,the microstructure was homogeneous tempered sorbite when tempered at 560?~750?.With the increase of tempering temperature,the micro-hardness of the material decreased from 399 HV to 216 HV,the tensile strength decreased from 1447 MPa to 758 MPa,and the impact toughness increased from 68 J to 201 J.Corrosion resistance rose first and then decreased with the increase of tempering temperature.When the tempering temperature was 650?,the corrosion rate of the material under the different corrosion media was the lowest.The best heat treatment process was quenched at 910? and tempered at 650?.At that time,the micro-hardness was 362 HV,the tensile strength was 1310 MPa,the impact energy was 149 J.The best corrosion resistance in different corrosive media was the best.The research results provide feasible suggestions for industrial production of corrosion-resistant oil casing steel. |
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