Low⁃carbon alloy steel is widely used in industrial design such as pressure vessels, vehicles, bridges, etc.By studying the influence of high pressure abrasive water jet on the cutting of low carbon alloy steel, the influence of water jet cutting characteristics on the cutting effect is analyzed, which has certain reference significance for improving cutting efficiency and reducing cutting cost.In the experiment, the five⁃axis linkage NC water cutter cutting machine is used，take Q345B as an example and the effects of cutting pressure, target distance and transverse speed on cutting depth and width are analyzed. The experimental results show that: with the increase of cutting pressure, the depth of cutting increases greatly. but the effect on cutting width is not obvious. Under certain conditions, there is an optimum target distance to maximize the cutting depth, the cutting depth decreases with increasing mobile speed. The target distance has a great effect on the cutting width, but the moving speed has little effect on the cutting width.

The effect of temperature on corrosion behavior of 316L stainless steel (316L SS) in 3.5% NaCl solution was studied by potentiodynamic polarization and electrochemical impedance，the semiconductor properties of the passivated film were analyzed by Mott⁃Schottky curve. The surface morphology of 316L SS after corrosion was observed by metallographic microscope.The results show that in the NaCl solution with a mass fraction of 3.5%, the open circuit potential and corrosion potential of 316L SS gradually decrease with the gradual increase of temperature, and the self⁃corrosion current density increases gradually.And the pitting potential is also gradually reduced. The results of surface corrosion morphology observation showed that the number and diameter of corrosion pits on the surface of 316L SS increased as the temperature increased.This is mainly because the temperature decreased the density of the passivation film and increased the dissolution rate of the passivation film, and decreases the corrosion resistance.

The theoretical analysis of the stress concentration factor K of three types of tubes with three different types of unfused defects is very complicated. In this paper, the finite element numerical analysis software is used to be established the finite element model of the three⁃way pipe with defects under the action of internal pressure. After calculation, the stress concentration factor K and its variation law under the four influencing factors are obtained. The results show that the stress concentration factor K of the three⁃way tube with three different unfused defects is relatively large in the shoulder and collar region, and the stress concentration is serious. The stress concentration factor K increased slowly with the increase of the axial length and depth of the defect, and decreased rapidly with the increase of the circumferential length of the defect.

Water in oil emulsion was prepared under different water volume fraction,stirring speed and temperature.By simulating the different situations encountered in the process of mixed transportation,the particle size distribution of the emulsion droplets and its relationship with viscosity were analyzed.The results show that when the volume fraction of water is less than 60% in the emulsion,the average particle size of the dispersed phase of the emulsion becomes smaller as the stirring speed is increased,and the viscosity becomes larger.With the increase of temperature,the average particle size of the dispersed phase of the emulsion is larger and the viscosity gradually decreases.As the volume fraction of water increases,the average particle size of the dispersed phase droplets becomes larger,and the viscosity shows a clear upward trend.However,when the water volume fraction is greater than 60%,the viscosity of the emulsion decreases drastically as the volume fraction of water increases,and the flow pattern of emulsion changes.The research results have certain guiding significance for the safe operation of pipelines and the study of gathering and transportation technology.

Fracture height control is a key factor for the development of low permeability reservoir, especially for the thin and poor quality zones. Aiming at the challenges of poor capping rock and ample muddy interbedding of formation of block Lu44 in Huabei Oilfield, secondary sanding fracturing technology are conducted as a way of stimulation. The secondary sanding fracturing technology can make a contribution to fracture height control has been proved by using the fracture height migration model. Through FracproPT software, the fracture height is compared between secondary sanding fracturing and conventional fracturing. At the same time, based on the result of numerical simulation, the reasonable fracturing parameters, including second sand volume, second preflush ratio, pump off time and delivery rate, are optimized. The secondary sanding fracturing has a good adptability in Huabei Oilfeild and better production in other wells.

Yumen oil sands were chosen as the experimental material to separated oil from oil sands through wet-grinding by light oil and washing treatment by washing agent. The tailing sands were characterized by XRD. The factors includingamount of light oil, amount of washing agent, concentration of washing agent, reaction temperature were also studied. The results showed under the reaction conditions of mass ratio of naphtha to oil sands 0.15, mass ratio of washing agent to oil sands 1.5, concentration of washing agent 8%,reaction temperature 80 ℃, the oil recovery could be up to 96.5%.

The ternary phase diagrams of diesel oil, water, cosurfactant and surfactant system were plotted. The effect of various parameters, such as HydrophileLipophile Balance( HLB) value, the mass ratio of cosurfactant to surfactant and other parameters, on the stability of emulsifying diesel oil, was studied by using the phase change of the ternary phase diagram. It was shown that the compound of different HLB value, weak base of additive, mass ratio of cosurfactant to surfactant had a great influence on the ternary phase diagram of emulsified diesel. The largest emulsion region of the ternary phase diagram was obtained when HLB value was 5.8 for the compound of Span 80 and Tween 60 and the mass ratio of cosurfactant to surfactant was 0.3 in alkaline environment. The experimental results show that the effect of emulsifying diesel oil was best during the minimum dosage of mixed emulsifier.