Papers by Keyword: 40Cr

Abstract: The effects of different zero-holding quenching temperatures on the tempering microstructure, mechanical properties and wear resistance of 40Cr were studied. The results showed that the microstructure of 40Cr was tempered sorbite and a small amount of unmelted ferrite after quenching at 850 °C and tempering at 550 °C for 2 h. Tempered sorbite was obtained after quenching at 880 °C～910 °C and tempering at 550 °C for 2 h. With the increasing of quenching temperature at zero holding temperature, the tensile strength and yield strength of 40Cr increased, while the elongation and impact toughness decreased. With the decreasing of impact test temperature, the ballistic work of 40Cr decreased gradually, and decreased fastest between 0 °C～-20 °C. 40Cr had the best impact performance after quenching at 850 °C and tempering at 550 °C for 2 h. 40Cr had the smallest wear loss after quenching at 880 °C and tempering at 550 °C for 2 h. Its wear marks were smooth, and had the shallowest furrows and ridges.

Abstract: The laser alloy cladding technology is used to treat the surface of 40Cr, and the two alloy powders are used separately. The process parameters are different, such as laser power, feed rate and scanning speed etc. The microstructure and hardness of cladding layers are analyzed by using scanning electron microscope and hardness tester. Generally, the surface quality is improved apparently. Under the similar laser power and powder quantity, the thickness of Ni60 cladding layer is much larger than Fe60. The hardness of Ni60 layer and Fe60 layer are all higher than substrate. There are more cracks in Ni60 layer than in Fe60 layer. The parameters of sample No.1 is optimal.

Abstract: As one of the quenched and tempered steels, 40Cr steel is often used to manufacture the shaft in heavy-duty trucks. To adjust the working environment of the heavy-duty machines, 40Cr steel should have high impact property. In this study, different tempering cooling mediums were treated as critical influence on improving impact property of the steel. After heated under 520°C tempering temperature, the samples of 40Cr were cooled in air, oil and water, respectively. The experiments were carried out through charpy impact, metallographical and SEM analysis. The results has shown that 40Cr steel of high impact property and fine microstructure can be obtained when water is used for the tempering cooling medium.

Abstract: For revealing the forming mechanism in micro level and for establishing the relationship between macroscopic deformation and microscopic changes, impact experiment of material property is conducted under the high speed cold roll-beating condition based on the plastic deformation mechanism of metal material, Based on the Zener-Hollomon constitutive relation, the macro change model is established, and the parameters of the 40 Cr are obtained according to the experimental data. Based on the model of microstructure evolution of dislocation density, the relation between macroscopic change and microscopic change is established, which provides the theoretical support for the forming process in micro level and revels the relationship between macro deformation and micro changes in the forming process of high speed cold roll-beating.

Abstract: 40Cr is a kind of steel that is often used for semiaxis in heavy duty trucks, therefore high impact property of 40Cr steel is requested to adjust the heavy-duty machines working environment. In this study, the samples of 40Cr steel were heated under normal tempering temperature and quenched in air, water and oil, respectively. The experiments were carried out through charpy impact and microhardness analysis. It was indicated by experiments that water was more helpful to receive higher impact toughness as the tempering cooling medium than air and oil. At the same time, the intensity and hardness of 40Cr steel were enough to meet the heavy-duty machine semiaxis requirements.

Abstract: The research object is 40Cr shaft parts after quenched and tempered. Optimize the main process parameters working pressure, frequency and amplitude of ultrasonic finishing. It is obtained that the various parameters influence the surface roughness of the machining samples and the optimum technological parameters combination which is consistent with experimental results. Using the SPSS software to analyze the results, obtained the process parameters impact trend of the postprocessing roughness. Contrast groups of test data, the best result was reduced by 98.4% compared with the initial roughness , reached the Ra0.04μm.

Abstract: Cutting tooth especially due to the poor quality of the shearer brazing, caused enormous economic losses each year in our country, which caused great pick consumption and delayed hours, and then resulting in reduced efficiency. The tooth body wear of the whole shearer picks accounts for half of its overall failure. In this experiment, the heat treatment which included heating temperature, soaking time, and cooling, etc. was designed by service conditions and performance requirements of the body material 40Cr. The change of microstrcture and mechanical property was analysed by quenching and tempering treatment, thus prolong the service life of shearer picks by improving the comprehensive performance of the tooth body material.

Abstract: The cutting pick is primarily used in footing excavation such as coal mining and roadway excavation, so the performance of cutting tooth directly affect the mining capacity, the driving efficiency, and the service life of the tool. The quality of domestic mining pick is lower than that abroad, especially the tooth body wear of the whole shearer picks accounts for half of its overall failure. Thus tooth body 40Cr was treated by various heat treatment processes in this experiment, so as to improve the hardness and wear resistance of cutting tooth, analysis the surface wear scar of morphology, research the wear mechanism, that made for reducing the consumption of cutting tooth, improving work efficiency, and easing the labor intensity of workers undergound.

Abstract: This paper has studied the formation mechanism of frame-shaped segregation in 40Cr wire rod rolled from bloom by means of the composition measurement, the electron microscopic observation and the energy spectrum analysis method. The results show that the frame-shaped segregation in wire rod originated from the positive segregation in columnar-to-equiaxed grain transition zone of bloom. The main influence factors are the solidification behavior of liquid steel in columnar-to-equiaxed grain transition zone, the temperature gradient of different solidification regions in bloom, the diffusion rate of the solute and inclusions in transition zone and so on. It may reduce the frame-shaped segregation by improving the purity of liquid steel, adopting the electromagnetic stirring in secondary cooling zone and enhancing the cooling intensity of the secondary cooling zone.

Abstract: This paper has analyzed the solidification structure and thermodynamic state of bloom by means of the electron microscopy observation and heat transfer model, and studied the cracking mechanism and influence factors in the cogging process of 40Cr bloom. The results show that the main cracking reasons are the unreasonable secondary cooling scheme, the high reheating temperature in the bloom surface, the coarser grain and widmanstatten structure of the bloom subsurface. When the bloom is conveyed from the steel mill to rolling mill, the bloom may crack for the phase transition stress and thermal stress, some micro-cracks occur in the bloom surface, furthermore, the crack will expand when it is heated in the heating furnace and rolled in the cogging mill, the cracking occurs in bloom eventually. In order to reduce the bloom cracking in the cogging process, it must optimize the secondary cooling system, reduce the cooling intensity, and adopt the thermal insulation, hot delivery and hot charge process. If the bloom can not be conveyed in the hot delivery and hot charge mode, it should be conveyed to the slow cooling pit.