Papers by Author: Yong Jun Zhang

Abstract: The paper mainly studied the corrosion properties of refractory weathering steel under chloride ion erosion environment. The full immersion tests on refractory weathering steel and carbon steel Q235 were conducted; and then a comparative analysis from the perspective of the corrosion weightlessness, the macro and micro morphology of rust layers have been made. Results indicated that refractory weathering steel and carbon steel corrosion weightlessness is relatively close to the early stage of corrosion, but the trend is reversed in the mid to late; refractory weathering steel corrosion weightlessness gradually decline, but the carbon steel’s is first increase then decrease. The carbon steel is mainly pitting corrosion, while refractory weathering steel develops general corrosion under chloride ion erosion environment. Rust layers of carbon steel are loose, hollow, and uneven. As the corrosion time goes on, the thickness of refractory weathering steel’s rust layers continuously thickening and the rust layers’ integrity are gradually increasing. The corrosion depth of refractory weathering steel is less than carbon steel’s; so does the longitudinal corrosion. This is because the microstructure of carbon steel is coarse pearlite and ferrite while the refractory weathering steel is granular bainite; the grain boundaries of carbon steel have more inclusions, especially MnS that is easily dissolved in chloride ion erosion environment. It is found that alloying elements Cr, Cu are enriched in the rust layers of refractory weathering steel by means of energy dispersive X-ray spectroscopy (EDS). The enrichment of these alloy elements in the rust layers improves the rust layer density, so that the uniform, dense, smooth rust layers formed on the surface of refractory weathering steel play a significant protective film to improve the substrate resistance corrosion.

Abstract: In refractory weathering steel cold-rolled sheet production process, the grains are elongated along the rolling direction, which will lead to the change of mechanical properties of sheets. Recrystallization annealing is an important process in the production of cold-rolled sheets. Therefore, research on recrystallization temperature and determining the recrystallization annealing time are important for the production of cold-rolled sheets. By measuring the hardness at different annealing temperatures and metallographic structure observation, obtained the refractory weathering steel of reduction rate of 66.7% recrystallization temperature is 650°C; By measuring the temperature of 700°C hardness under different annealing time and metallographic structure analysis, when recrystallization annealing time is 1 hour plasticity and strength of cold rolled sheet fits well, with excellent comprehensive mechanical properties.

Abstract: In hot rolling process of 2205 duplex stainless steel, it was found that bright line defects are mainly located at where is about distance of 200 mm from two sides of hot rolled plate. The forming reason of bright line defects is studied by means of metallographic microscope, scanning electron microscope (SEM) combined with energy dispersive spectrometer (EDS). It is concluded that the formation of bright line defects has associated with sticking and that the temperature reduction on the edge of hot rolling plate causes a high percentage of austenite phase which is network structure. In order to prevent or avoid the happening of the sticking phenomenon, it is necessary to uniformly distribute the oxide on the strip surface by controlled rolling process.

Abstract: Horizontal V – shaped anvil forging method is introduced to control fibrous tissue flow direction through changing shape of anvil, to improve the anisotropy of mechanical properties of forgings. This method can provide effectively drawing out technology for heavy axial forgings with requirements on the transverse mechanical properties. In this paper pilot production for rectangular billet by the forging method with horizontal V - shaped anvil were carried out. The results show that the forging method with horizontal V-shape anvil can improve transverse mechanical properties, realize uniform forging for heavy axial forgings, the ratio between transverse and longitudinal mechanical property is about 1.0 in the same position for heavy axial forgings, and uniformity degree of mechanical properties is better.

Abstract: Modern composite armor plate is generally composed of faceplate with high hardness and backplate with good toughness. 45 steel/60Si2CrA multilayer composite casting blank with 11 layers, containing 60Si2CrA steel as faceplate and 45 steel as backplate, was fabricated by composite casting. The deformation and heat treatment process of 45steel/60Si2CrA multilayer composite plate were studied. The results show that the interfaces between faceplate and backplate have good combination and the thickness of each layer is basic uniform by reasonable deformation distribution. Yield and tensile strength of the composite plate reaches 956MPa and 1018MPa, the hardness of 45 steel layer and 60Si2CrA layer is 448HV and 536HV respectively after the heat treatment of 860°C water quenching+ high temperature tempering. The mechanical properties meet the qualification of armor plate. The bulletproof test displays that 45 steel/60Si2CrA multilayer composite armor plate can prevent the breakthrough of DAP51B type bullet with the velocity of 500m/s.

Abstract: The forging method with horizontal V – shaped anvil is introduced to control fibrous tissue flow direction through changing shape of anvil, its working face is composed of four projecting cone, it can realize no transverse tensile stress forging. For this, in the paper qualitative physical simulation was carried out. The results show that there was no crack between the hole and the pin in deformation zone of rectangular billet by horizontal V – shaped anvil forging method, therefore, the authors think that there no transverse tensile stress in deformation zone of billet in the forging process of horizontal V – shaped anvil.

Abstract: The CCT (Continuous Cooling Transformation) curve of hot deformation austenite in 55SiCr steel was measured on Gleeble-1500 thermal simulation machine, the microstructure and hardness of transformation products under different cooling velocities were observed. The microstructure transformation regularity with being cooled continuously were emphatically researched at the cooling rate form 0.1°C/s to 15 °C/s. The results can provide a instruction for producing 55SiCr steel.

Abstract: The cold-roll-formed profiles usually defects such as bow, camber, twist, edge wave, corner buckling as well as edge cracking, and splitting. Straightening is used as the later part of working procedure in order to eliminate these defects and improve the quality of the final profile. A drawing straightening machine is designed to achieve the purposes of the U-shaped steel straightening. In the design coefficient of friction, forming speed, roll speed, methods to minimize defects.

Abstract: At present, bimetal tube has been used wildly in industry and there are many methods for preparation these kinds of tubes. In consideration of deficiencies of available methods, a new technique of bimetal tube preparation was presented in this paper. With appropriate design and manufacture of facility and design of experiment, copper clad steel tube was prepared. Feasibility and practicability of this process was verified by conclusion of research. At last, the following study was discussed.

Abstract: Development of low-sulfur and Pb-free hypoeutectoid graphitized free cutting steel is significant because the use of S or Pb free-cutting steel can result in serious pollution. Due to graphitization process in hypoeutectoid steel is very slowly, so it is crucial to accelerate the graphitization process. The tested steel is prepared based on that graphitization can be accelerated by increasing nuclei of graphite. On the base of indirect observation on graphite particles in the sample by OM and quantitative metallography for different graphitization times, the kinetic curve was drawn the graphitization process of tested sample, it matches the Avrami eqution well.