Papers by Keyword: Gear Steel

Abstract: Based on the thermodynamic calculation, the conditions of calcium treatment to sulfur gear steel are analyzed and the samples of rolled steel are studied. Results show that Calcium treatment to melting steel after RH refining can make the sulfide inclusions and calcium aluminates bind together and form the spindle shaped low melting compound inclusions. In the meanwhile, controlling of w (O) in steel below 0.0012% before calcium treatment is more beneficial to modify the Al₂O₃ and sulfide by the added calcium and to form the oxide-sulfide compound inclusions only if w (Al_S) in steel is adjusted to 0.015%~0.025% before continuous casting. The Ca wire should also be fed at higher temperature.

Abstract: Problems of uncertainty for gear steel hardenability control in rolling process, this article will applied improved Quantum-behaved Particle Swarm Optimization algorithm to the uncertainty, using the optimization algorithm to train the neural network by improving quantum groups, build optimized gear steel quenching permeability control neural network model. Simulation results show that this algorithm is an effective solution to the problem of gear steel hardenability predictive control. Keywords: Quantum-behaved Particle Swarm Optimization, gear steel, Hardenability

Abstract: ShouQin Metallic Material Co., LTD developed the high grade gear steel SCM420H for car manufactured by electric furnace compact processing route process. With the process measures such as beneficiated material principle, making foamed slag in smelting process, over roll-protection casting and electromagnetic stirring in and control coolness velocity after rolling, the results show that steel reach to high quality level with high pureness, hardenability and malleability well cooperated.

Abstract: In order to make nonmetallic inclusions with low melting point and improve the fatigue resistance of gear steel, thermodynamic analysis on precipitation of nonmetallic inclusions CaO(MgO)-Al₂O₃ system was investigated in this paper. The complex deoxidation equilibria of strong deoxidizing elements such as aluminum, calcium, magnesium and so on were calculated accurately with the second order and middle term of the activity coefficient expression. Thermodynamic conditions for the precipitation of spinel inclusion (MgO•Al₂O₃) is sufficient as the acid-soluble aluminum content is 0.04% and magnesium content is less than 0.0005% in the tested gear steel 20CrMoH. The relationship between precipitation of spinel and calcium aluminate inclusions in gear steel and the composition of molten steel at 1873K indicates that, the compositions of inclusions before and after calcium treatment are C₁₂A₇ and C₃A respectively, while the reactions in ladle reach the equilibrium state.

Abstract: In this study, the temperature field distribution of 22CrMoH billet is first obtained by simulating continuous casting process using moving boundary method. On the basis of the above data, the microstructure of 22CrMoH gear steels billet was simulated based on CAFÉ (Cellular Automaton – Finite Element Analysis) method, together with the effects of alloying elements such as Cr, Mo, Si, Mn on the microstructure of this billet. The simulated result agrees reasonably well with that of the actual product. And it suggested that under the reasonable extend of current steel grade, the increased amount of Si and Mn can steadily widen the proportion of equiaxed grains, lead to the increase in equiaxed grain amount, hence the decrease in equiaxed grain average radius; The increase in Mo content is able to enhance the nucleation amount; Proper decrease in Cr content favors the increase in proportion of equiaxed grains, but little effects on grain’s amount and radius. Further, the composition of alloy elements under the specified scope of 22CrMoH grade was optimized and the simulated results showed that the microstructure has vastly improved, as the proportion of equiaxed grain rose nearly doubled, the grains amount has increased by 19.96%, and average radius has decreased by 9.20%.

Abstract: In the paper, the superiority-inferiority in various calculations of hardenability has been compared, and the method of nonlinear regression equation was chosen to establish a mathematical model. The model was modified through the actual production of the gear steel hardenability data. Based on the model, a prediction platform was developed with computer tools to calculate the hardenability of gear steel. The hardenability prediction software can calculate random Jominy distance hardness according to chemical composition and grain size. The forecast accuracy is better than that of unmodified nonlinear regression equation and multiple linear regression equation, but equal to that of artificial neural network.

Abstract: In this paper the fatigue life of spur gear was investigated by changing the shot peening condition. From bending fatigue test depending on various shot peening intensity, fatigue characteristics were investigated. The causes of reduction in fatigue life were analyzed by observing the surface of gear with Scanning Electron Microscope(SEM), and impact of residual stress to fatigue characteristics was identified by measuring compressive residual stress depending peening intensity by depth. The results show that the optimum shot ball velocity is 65 m/s and optimum peening time is 8 minutes. From SEM image, the micro-crack was observed at the surface in case of over peening. This seems to be the factor which reduces fatigue life by decreasing compressive residual stress of surface.