Vanadium, Niobium, Nitrogen N80 Grade Non-quenched And Oil Casing Organization And Performance

Non-tempered steel is adding micro-alloy elements to medium carbon manganese steel, such as vanadium, niobium, and nitrogen etc. Control the precipitation of micro-alloy compounds by using the hyperthermia deformation and then cooling in the control rolling process, to get the grain refining then strengthen the steel. The property of this steel under rolling can achieve the property level of ordinary tempered steel. So using this non-tempered steel can omits the temper process. It can shorten the production cycle, converse the energy and reduce the production cost.This passage described the development and research status of micro-alloy non-tempered steel and oil well pipe in domestic and abroad, and discussed the strengthen and toughen way of micro-alloy non-tempered steel and the effect of vanadium, niobium, nitrogen in the non-tempered steel. Process the samples according to making steel, forging steel in the library. Analyzing the samples can get the influence rule that the affection of vanadium, niobium, nitrogen to the structure and property of N80 non-tempered oil sleeve.According to the analysis, vanadium, niobiums, nitrogen can simultaneous improve the strength and toughness. So designing four N80 non-tempered steel with different components, analyze the influence rule of vanadium, niobium, nitrogen to the structure and property of N80 non-tempered oil sleeve. And design four different thermal simulation processes according to the dynamic CCT curve of the N80 steel, to analyze the influence of thermal simulation process to the structure and property of N80 non-tempered oil sleeve. The main conclusions are as follow:(1) Elements vanadium, niobium, nitrogen all can refine the ferrite grain, increase the volume percentage of pearlite in the N80 non-tempered oil sleeve.(2) Adding the vanadium, niobium, nitrogen to the N80 non-tempered oil sleeve separately, the impact-toughness decrease and strength increase with the increase of the vanadium, niobium, and nitrogen percentage.(3) Adding the vanadium, niobium, nitrogen at the same time, can greatly improve the strength of N80 non-tempered oil sleeve without reducing the toughness and plasticity.(4) According to the thermal simulation test, the best control cooling ending temperature is 550℃, the austenite can completely translate to ferrite and pearlite at this temperature. Choosing the process which using higher temperature at thethird pass, can improve the hardness of the N80 non-tempered oil sleeve.