The Research Of Heat Treatment Characteristics On 30MnCr22/P110 Seamless Pipe

Oil well pipe is strongly used in petroleum and natural gas exploration. As the strategic of oil drilling industry shifts from east to west and coastal, the depth of oil layer changes from shallow to deep and this change calls for reasonable adjustment on steel grade and structure, higher and newer requirements on oil well pipe strength, performance and quality, therefore, great efforts to develop high-grade special steel oil well pipes is imperative. Meanwhile, because of the effect of financial crisis and the excess of steel capacity, enterprises continue to reduce production costs, the development of marketable products has important practical significance.This article focuses on the heat treatment phase transition characteristics of steel 30MnCr22, that is, continuous cooling transformation (CCT) curve and hardenability were studied. It includes: the determination of CCT curve with the method of DTA in order to determine the martensite critical cooling rate, austenite temperature range and the microstructure; the measurement of hardenability on different quenching temperatures with the method of end quenching in order to research the effect rules of quenching temperature on the steel hardenability.On this basis, heat treatment process parameters of this steel were studied, which contained the effect rules of quenching temperature, holding time of quenching, tempering temperature, holding time of tempering on 30MnCr22 mechanical properties and microstructure. So, the heat treatment process of 30MnCr22 of F177.8×9.19mm steel is determined as follows: at 880~℃, holding time 50min, water quenched; 530~℃tempered, holding time 60min, air-cooled. By the research of heat treatment parameters, all the mechanical properties of 30MnCr22 (P110) are in coincidence to API standards. After quenching and tempering, morphology is homogeneous, grain is small, strength and toughness has a good match and it is suitable for industrial production. The research of steel 30MnCr22 microstructure and properties has basic importance on verify steel reasonableness and the manufacturing process search of P110.