Study On L80-9Cr Steel Containing Rare Earth In Baotou Steel Union Co.,LTD. Used For Corrosion-resistant Oil Well Pipe

With the growing drilling and development difficulty and depth of petroleum and natural gas,there has been a higher requirement of the comprehensive mechanical performance and corrosion resistance of steel for the use of oil well pipes.L80-9Cr oil well pipes are products with a high added value.Therefore,it has been an imperative to study corrosion-resistant and rare-earth-containing L80-9Cr steel of Baotou Steel Union Co.,LTD.,which holds vital significance to make up Baogang's product gap.This paper proceeds from technical specifications of API SPEC 5CT product standard about L80-9Cr steel to study the working status and use conditions of oil well pipes,finish the component design,chauffer smelting,and simulated rolling of two experimental steel types,10Cr9Mo V and 10Cr9Mo VRE,observe their rolled microstructure and analyze their chemical components and mechanical performance.Additionally,the phase transformation point test is carried out and the quenching and tempering heat treatment process was studied;Concerning steel types with a better comprehensive mechanical performance,the high-temperature tensile test and the high-temperature,high-pressure anti-corrosion simulation experiment are conducted.Research findings indicate that the phase transformation points₁ andof the experimental steel 10Cr9Mo V are 799?and 858?,respectively;the phase transformation points₁ andof the experimental steel 10Cr9Mo VRE are 800?and 960?,respectively.Under the experimental conditions that the hardening heat is 960?and water-cooling with heat preservation lasts for 60 min,and that the temper temperature is 760?with heat preservation lasts for 90 min,the main microstructure of 10Cr9Mo V and 10Cr9Mo VRE is the martensite.Compared with 10Cr9Mo V,the longitudinal impact of 10Cr9Mo VRE at the temperature of 0?improves by around 10%.Besides,the content of inclusions of10Cr9Mo VRE are low,small in size and round in shape.Therefore,various mechanical performance indexes of 10Cr9Mo VRE can better satisfy technical specifications of L80-9Cr experimental steel design.High-temperature tensile test of 10Cr9Mo VRE reveals that,when the test temperature is 1,225?and 1,250?,respectively,the experimental steel demonstrates a low strength and good ductility.This means that the temperature interval from 1,225?to 1,250?is the suitable perforated temperature.Meanwhile,corrosion-resistant test of 10Cr9Mo VRE shows that the average corrosion rate of 10Cr9Mo VRE drops along with the increase of the experimental period,solution p H value,and Cl^-concentration;increases along with the increase of the experiment temperature and flow rate;first increases and then decreases as the CO₂ partial pressure rises;and first drops and then increases as the H₂S partial pressure rises.The corrosion product of 10Cr9Mo VRE samples are the membrane,which are smooth and compact,and experience light and medium corrosion.However,34Mn6 samples of the same strength undergo medium,serious and extremely serious corrosion.So the corrosion resistance of 10Cr9Mo VRE can generally satisfy the use needs.The experimental steel,10Cr9Mo VRE,demonstrates favorable corrosion-resistant performance under the premise of meeting the mechanical property requirements of API SPEC 5CT standard.