| SignificanceHardenability is one of the most important parameters controlling the heat-treated properties of engineering steels. It affects the consistency of response for microstructure, hardness, strength, toughness, and dimensional chang. Master steel hardenability of the law and to be able to use the steel sector and mechanical designers, heat treatment of steel workers in the choice of species provide the important references. Therefore, the steel hardenability has become metallurgical, mechanical and heat treatment, manufacturing parts, choose steel production and heat treatment process to choose one of the most important, is a reasonable choice and the use of steel species must be considered essential. Objectives and contentRecognized by the world and the effective application of the test data based on the creation of new Jominy mathematical model not only to accurately describe all kinds of steel Jominy hardness and the relationship between the distance, and raise Jominy distance not only determine the parameters this parameter said steel hardenability named hardenability factor. Establish structural steel hardenability coefficient between the chemical composition and the relationship, so as to the basis of known chemical composition to predict steel hardenability value.A differential equation of the Jominy curves has been constructed according to the Jominy experimental data and change of derivative of the Jominy curve. The linear trial method was used to choose optimal type of function. An analytical function containing the undetermined parameter was used to calculate the Jominy hardness distributions. This undetermined parameter was defined as the hardenability coefficient of steel, which is different from the conventional element coefficient and depends on the descending velocity of the Jominy curve. Therefore, the problem predicting the Jominy curve changes to one calculating the hardenability coefficient. The model for calculating the hardness distributions has been described as the subsection functions consisting of both straight line and curve. The straight depicts the hardness of the martensite region where the martensite is entirely obtained and the hardness remains a constant maximum value. In addition, the hardness is continuously reduced in the region of the curve until the hardness approaches a minimum value. The hardenability of steels has been expressed as a coefficient that is equal to the whole distance of inflexion of Jominy curve in numerical value. The distance includes length of straight line in which martensite is entirely obtained, while it is not related to the Jominy distance. The value of the hardenability has been obtained by a method of the non-linear curve fitting to the Jominy test data. It was demonstrated that the hardenability coefficient depends on the chemical composition under the condition of the standard Jominy test. An empirical relationship between the hardenability coefficient and the chemical composition of structural steels has been established using nonlinear Simulation Program and multiple linear regression. Substituting the obtained hardenability coefficient into the distribution model of the hardness, the predicted Jominy curves exhibited very good agreements with the experimental data. Study steps First, according to published material manual steel Jominy test curve data from the derivative curve of the changing law proposed low - and middle-Steel Hardenability Jominy curve equation. Testing method using linear differential equations for the specific best form of a solution equation, hardness distribution function. The substitution tentative data carries on the confirmation to the obtained function.Second, low - and middle-Steel Hardenability Jominy model introduced in high school for low hardenability Steel unified mathematical model. The model selected an undetermined parameters, the parameters of both distance and Jominy has not changed significantly hardness curve shape. This parameter after the corresponding variable substitution, names as the hardened coefficient.Third, hardenability coefficient after the simulation steel hardenability coefficient and test. Hardness distribution function where a detachable parameters, Parameters of this size can significantly change the length of the straight line and curve of the decreasing speed of hardness, and it has nothing to do Jominy distance. It is not an ideal state of numerical has measurability. It directly description of hardened steel, that is, the ability of martensite. Into the test data, using mathematical software obtained origin of the kind of steel hardenability value. Hardenability relates to the chemical composition of steel and organization of the state, has nothing to do with the Jominy distance. Then simulate Jominy belt value and test.Fourth, the proposed standards Jominy test under the conditions of the steel hardenability coefficient depends on the chemical composition, nonlinear simulation technology, already into the Jominy test data obtained Steel jominy coefficient, then the establishment of the chemical composition and hardenability relationship between the coefficients. FindingsThe formula of Jominy curve hardness distribution based on distance from the x variable for the function, so it only applies to the end quenched samples. According Jominy test data and test derivative curve changes, the linear method to test the Jominy curve equation then a solution hardness distribution function, which has four parameters. The first parameter Jmax said the cold end to the maximum hardness, and the second parameter Jmin of the sample said that the minimum hardness. These two parameters can be derived directly from the experimental data. Third parameter a indicated the length of the straight-line and obtains the complete martensite. The fourth parameter h very important units to millimeters said. It Jominy distance irrelevant, numerical inflection point on the curve to the total distance is the full length of martensite regional and regional decline curve inflection point and the distance. Found that the size parameter values directly change the shape of the curve. When the parameters h become larger decline gentle curve and change-hour fast decline curve. H greater value, the better the hardenability. This shows that parameters can be used to express the steel hardenability, it describes the decline of martensite content size, and a pair of steel is the only species identified. Steel hardenability of a material nature, we will parameters h named hardenability factor. Steel species known hardenability coefficient test data can be simulated directly. With Jominy value h into the proposed mathematical model test. Simulation results show that the model was agreement with experimental values very well.From the establishment of the chemical composition and hardenability coefficient between-analysis: low-alloy structural steel hardenability coefficient with the carbon content increased. In the same Carbon content conditions, the alloying elements of the type and content of a significant impact on the value of hardenability coefficient. Mn, Cr, Mo, Ni alloy elements make Jominy increases the coefficient, which is fully consistent results. Jominy standard test conditions Steel Hardenability coefficient depends on the chemical composition, nonlinear simulation technology and multiple linear regression, Chemical ingredients will be used to calculate the coefficient of hardenability of hardness into the distribution model of Jominy curve of a forecast, The results showed that the predictions curve with the experimental values agree well.Finally, the mathematical model to simulate the h value obtained with the chemical ingredients for calculating the h value for comparison testing. Tested steel, chrome steel, chrome-manganese steel, Mn-Mo steel, Cr-Mn steel, Cr-Ni-Mo steel, Cr-Mn-Ni-Mo steel. Very good agreements have been obtained between the simulated h and predicted.This paper presents the Jominy curve mathematical model and hardenability coefficient prediction formula is only applicable to silicon, manganese, chromium, molybdenum, nickel alloy commonly used steel structure. Other alloying elements structural steel because the tentative data is insufficient has not been able to include the simulation category, therefore possibly brings a bigger error.
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