Method of justification of machine parts hardening modes
2021
Pastukhov, A., Belgorod State Agricultural Univ. named after V. Gorin (Russian Federation) | Sharaya, O., Belgorod State Agricultural Univ. named after V. Gorin (Russian Federation) | Timashov, E., Belgorod State Agricultural Univ. named after V. Gorin (Russian Federation) | Bakharev, D., Belgorod State Agricultural Univ. named after V. Gorin (Russian Federation)
Based on an overview of methods for hardening and restoring parts of agricultural machines, it has been found that the methods currently used are highly labour intensive and are not well suited for hardening the cutting edge of tillage machine discs. A method of electromechanical hardening of ploughshare discs due to simultaneous thermal action and plastic deformation is disclosed. Electromechanical hardening modes are justified on the example of standard cylindrical samples. The developed technique contains the following stages: determining the steel grade of a part; planning of the experiment based on the plan of the full two-factor three-level experiment with selection of influences and response function; experimental hardening of laboratory samples at the installation; microstructural analysis of hardened samples; numerical processing of experiment results. Based on the optical emission analysis, it was found that the samples are made of steel 65G. The factors of influence are: current strength X1(Ir) = 800...1200 A on the reinforcing tool in the form of a roller and the pressing force X2(Fk) = 100...300 N of the tool to the part. The hardness of the surface layer Y(HRC) is adopted as the response function. Microstructural analysis showed that a layer consisting of several zones was formed on the hardened surface of the sample: white, light non-flowing and dark martensitic, passing into the ferrite-pearlite structure of the base. On the basis of multiple regression analysis, an empirical mathematical model is obtained and its graphical interpretation in the studied area of factors values is given. According to the criterion of providing wear resistance of working edges of disks, maximum hardness is achieved at current strength X1(Ir) = 1060 A and force X2(Fk) = 210 N in the contact zone. Developed technique and tested modes of electromechanical hardening are suitable for development of process of hardening of disk ploughshares of grain-grass seeders.
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