Технические науки 8. Обработка материалов в машиностроении

Malafeev Yu.М., Grebenyuk V.V.

The National Technical University of Ukraine «Kyiv Polytechnic Institute», Kyiv.

EXPLOITATION CHARACTERISTICS OF PARTS

FROM ALLOY 50N

Technological processes of parts manufacture from permalloy alloys have a significant impact on the product exploitation characteristics [1, 2, 3, 4]. They are include the magnetic properties of material. Qualitative characteristics of product are changed too. These include roughness of machined surface [5, 6, 7, 8, 9].

In our research, we consider the process of thin turning of permalloy 50N using cutting tool, which was better recommended on the first phase of the study. It is the representative of tungstenfree carbide KNT16. It was used by us to determine the optimal tool geometry. Thanks to its low coefficient of rubbing the roughness of machined surface is decreasing [10], and the value of the fall of the maximum magnetic permeability is reducing Δμ_max,%.

Preliminary experiments of thin turning with using sharpening tool with a small slice thickness are revealed that the main cutters deterioration is going on the back surface. In the literature, there are no any recommendations for technological parameter of permalloy machining. In ongoing research, we replaced the final polishing operation of permalloy 50N with the thin turning process. This replacement is improves technological heredity of the alloy processing and prevents the annealing operation after machining to the magnetic properties restore.

Creating a new process of manufacturing parts from alloy 50N with finish turning is related with the definition of geometry of the tool cutting part. The form copied of cutting tool blade is going on the treated surface at thin turning [11]. The experiment results are obtained the mathematical model influence of geometric factors on the surface machined roughness and the fall amount of the maximum magnetic permeability, which are as follows:

R_a, mkm=0,59+0,32γ+0,13α–1,37r–0,014γα+0,007φ (1)

Δμ_max,% =17,47+9,17γ+0,35α–15,99r–0,15γα+0,28φ (2)

The researches and subsequent processing of the experimental data [12], are allowed to establish a number of mathematical models of the influence of cutting conditions and tool wear on the studied parameters of the turning process of alloy 50N. After statistical analysis of the experimental data there was obtained a mathematical model, describing the effect of cutting conditions and wear on the fall amount of the maximum magnetic permeability Δμ_max, %. To simplify the formula using, that takes into account the complex interactions of studied technological factors, correlation analysis was conducted. It made possible to establish the relationship to determine the loss Δμ_max, %. at the microhardness of the machined surface H. This makes possible to estimate the magnetic characteristics at the real samples without no sample preparation - "witnesses", using the following formula:

Δμ_max, % = – 47,1+0,67Н (3)

The experimental results lead to the following conclusions:

1. The resulting models (1, 2, 3) adequately describe the thin turning process of the alloy 50H. They allows to calculate the value of formed exploitation characteristics.

2. In the researches, we replaced the final polishing operation of the permalloy 50N at thin turning process. This replacement is obtained to improve the technological heredity processing of the alloy and increase the performance of the cutting process by 2,5 times and reduce the of treatment cost to 3 times.

3. The optimal tool geometry was determined using the steep ascent. This made possible to obtain the blade geometry, that is close to the optimal values.

4. The regularity of the evaluation criteria Δμ_max, %, changes of the investigated technological factors, was established. This allows to technological process control and to predict the specified exploitation characteristics of products from permalloy 50N.

5. Practical recommendations for cutting conditions was developed. Using LP_τ method - search area optimum was refined. Cutting conditions, that are close to the optimal values, were defined according to the obtained mathematical models.

6. The correlation analysis revealed the dependence of the losses amount Δμ_max, % determining using the microhardness of the machined surface H. This allows to evaluate the magnetic characteristics on the real samples without no sample preparation - "witnesses." Significantly reduced the time required for parts manufacturing from permalloy 50N.

7. Thin turning of the permalloy is favorably sanding alone from polish with the fact, that the residual strain compression and strain tension, that is balancing it, are formed in the product surface layer. With this assignment, it can be possible to keep the blade treatment almost without no loss of magnetic properties at optimal condition. This allows to eliminates lengthy and expensive annealing operation on the last stage of product manufacture, carried out in order to magnetic properties reсover.

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