A Study On The Adaptability Of65Mn And38CrMoAlA’s Mechanical Property And High Temperature Structure

Steel material is an important kind of engineering materials for human survival and development, and also one of the important marks of social progress. The Experimental materials involved in this thesis are65Mn and38CrMoAlA, belonging to high-quality steel, which are the main materials of gas injection pipe string and packers. With high hardenability and elastic,65Mn is a kind of carbon steel, which is used in a variety of springs and accessories. While38CrMoAlA which is used in the manufacture of nitrided parts with high wear resistance and high fatigue strength is a kind of alloy structural steel, belonging to quenched and tempered steel with medium hardenability. There is no related research on the issue of the suitability of injecting the pipe and packers with superheated steam. Thus, this paper will analyze the mechanical properties and microstructure of65Mn and38CrMoAlA and on this basis, studying the high temperature heat treatment process performance and associated conditions. This thesis research has important significance in material selection and design of downhole tools and wellhead.Specific contents are as follows:(1) Designing the program of microstructure observation and mechanical properties experiments on65Mn and38CrMoAlA. In order to study the best performance when they are servicing, but also carry out the orthogonal experimental design related to heat treatment.(2) Doing experimental verification of65Mn’s chemical composition. I observe and analyze the microstructure of65Mn on the condition of different tempering temperature. As the temperature increased, it’s hardness degree, yield strength and tensile strength reduces while the values of AKU,δ and ΧΨ increases, meaning that tough and plastic are inhanced. At last, I obtain the best heat treatment of65Mn when it servces in400℃by four-factor and three-level orthogonal experiments and the inferential reasoning of variance analytic method about many times repeated trial.(3) Doing experimental verification of38CrMoAlA’s chemical composition. I observe and analyze the microstructure of38CrMoAlA on the condition of different tempering temperature. As the temperature increased, it’s hardness degree nearly maintains invariable, while yield strength and tensile strength reduces and the values of8and Ψ increases, meaning that tough and plastic are inhanced. What’s more, it occurs the first kind of temper brittleness in the temperature of300-400℃. At last, I obtain the best heat treatment of38CrMoAlA when it servces in400℃by four-factor and three-level orthogonal experiments and the inferential reasoning of variance analytic method about many times repeated trial.(4) Using the least squares method principle, I infer the tempering equation of38CrMoAlA on the atomic thermodiffusion rate equation named Arrhenius equation.