Abstract
The object of research is the process of 30ХНМЛ steel melting in two electric arc furnaces with a capacity of 6 tons. Technological audit of the process is carried out on existing furnaces in the steel foundry of a machine-building enterprise specializing in the manufacture of large shaped castings for products of transport engineering. The audit is aimed at analyzing the compliance of the performed main technological melting operations with the required regulated technological instructions.On the basis of carrying out serial meltings, a sample of experimental and industrial data is obtained to determine the tensile strength of steel samples 30KhNML. It has been established that according to the actual production data of serial heats it is impossible to postulate the distribution law, in particular, to speak of a normal distribution. Therefore, the use of statistical sampling functions to assess the melting stability is not advisable. It is proposed to use the stability coefficient (η), based on the calculation of entropy (H), as a criterion for assessing the melting stability. It is proposed to use a fuzzy description of these values for practical use in assessing the melting stability. In this case, it can be assumed that the calculated values of entropy and melting stability coefficient for each sample separately and the total sample form the left (αjp) and right (βjp) fuzziness boundary. It is proposed in the fuzzy description to use the membership function of (L–R) type. In a specific case, it can be assumed that αjp=2.63, βjp=2.71 (for a fuzzy number H) and αjp=0.22, βjp=0.24 (for a fuzzy number η).Thanks to the proposed method for assessing the melting stability, it is possible to obtain objective data without relying on the assumption of a normal distribution law. The proposed method is invariant to the type of technological process in the blank production. These can be metal forming, heat treatment and other metallurgical processes. The importance of the proposed method is related to the fact that the quality of further technological operations for the production of finished parts depends on the inheritance of the quality of blank production as the previous technological stages of production.
Highlights
Steel melting in electric arc furnaces is one of the processes that have significant uncertainty, which mani fests itself in relation to both input and output process variables
The strength of this research is the justi fication of the method for assessing the stability of the electric melting of 30ХНМЛ steel. This is due to the im portance of the quality issues of finished products, on which the competitiveness of the manufacturing company fully depends
It should be noted that the proposed method of assessing the stability indicators is invariant to the type of technological process in the blank production
Summary
Steel melting in electric arc furnaces is one of the processes that have significant uncertainty, which mani fests itself in relation to both input and output process variables. It is important to set the left and right boundaries of fuzziness, regarding the choice of which expert opinions may differ. The values of these limits can be determined only on the basis of real data, which are available in the mode of carrying out serial heats. It is possible to obtain a sample of real data for further evaluation of the inac curacy of the description of technological parameters of melting in electric arc furnaces and to assess the stability of this process
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