Translated Abstract
High strength and high toughness oil casing materials mainly applied to casing performance requirements especially harsh deep well and ultra deep wells with complex geological structure conditions. As the oil industry development, safe service of the casing pipe became more tough, low-qualified casing pipe materials could not meet actual need of oil field. Currently the highest standard of API for casing steel is grade Q125, so it is imperative to develop not API grade of steel-casing pipe with high strength and high toughness. This paper firstly researched the relationship between the heat treatment process and strength、plasticity and toughness of P110 steel grade of the casing material. Secondly, explored the 75# new material heat treatment process and researched the mechanical properties. By optimizing the two material heat treatment process and assessment the two materials could meet high strength and high toughness mechanics performance requirements or not.Firstly, researched the P110 steel grade casing pipe in detail, including the improvement of heat treatment, property of tensile performance and impact strength, pattern of impact fracture, microstructure, shape and composition of foreign impurity and so on. The results showed that: P110 steel grade of the casing material which has been quenched 890 ℃, 550℃ ~ 650℃ range of tempering, 2min/mm ~ 5min/mm range of tempering coefficient, the different heat treatment parameters combination is able to meet the mechanical properties high strength requirements of the 110 ~ 140 grade steel. P110 has quite high impact resistance, Transverse specimen’s impact energy higher than 110J in 0℃ which has been quenched 890℃, 550℃ ~ 650℃ range of tempering. Only from the material consideration, the material with little impurity, But also contain a few multiple components of inclusion. According to the result of the experiment, This material of P110 is difficult to meet the use of 140 steel grade above level high strength requirement.On the basis of P110 casing material, a new 75# material has been developed which specially added elements of V and Nb, a large number of heat treatments were carried out to determine the best heat treatment process in addition, the relationships between mechanical properties and the microstructure of 75# which influenced by heat treatment process through tensile test, low temperature impact test. The results showed that: the new material of 75# which has been quenched 830℃ ~ 930℃, 500℃ ~ 620℃ range of tempering, 2min/mm ~ 5min/mm range of tempering coefficient, the different heat treatment parameters combination is able to meet the high strength mechanical properties requirements of the 140 ~ 160 grade steel. As well as the steel quenched at 900℃, 500℃ ~ 620℃ range of tempering, 2min/mm ~ 5min/mm range of tempering coefficient, the transverse specimen impact energy > 70J which have been impact in the low temperature of 0℃. The 75# material has good low temperature impact toughness properties.
Translated Keyword
[High strengthHigh toughnessCasingMechanical propertiesHeat treatment]
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