Method for analytical determination of machinability of carbon and low-alloy steels during turning

Abstract

FIELD: mechanical engineering.SUBSTANCE: invention relates to the turning of carbon and low-alloy steels. The machinability coefficient of other grades of steel in comparison with the reference sample is determined by the product of the difference in value ΔU*i between the critical density of internal energy U*, at which the shift of the chip elements occurs during turning of steel and the accumulated initial internal energy of the new material before mechanical processing Uoi by the value of the difference in tensile strength σve and physical yield strength σte of the reference sample, which is divided by the product of the quantity ΔU*e of the reference sample by the value of the difference in tensile strength σvi and the physical yield strength σti of a different grade of steel.EFFECT: determining the machinability coefficient of materials made from new carbon and low-alloy steels based on the energy and mechanical properties of these materials.1 cl

Description

[0001] The invention relates to the field of mechanical engineering technology, in particular the turning of carbon and low-alloy steels.

[0002] Currently, studies on the machinability coefficient of carbon and low-alloy steels are known. For example, the author of the work (Tashlitsky N.I., "The Effect of Mechanical Properties and Thermal Conductivity of Steels on Their Machinability." Moscow: Mashgiz, 1952. - 84 p.) conducted experimental studies on the effect of heat treatment and the thermophysical properties of steels on their machinability. In recent decades, publications related to the machinability of heat-resistant and corrosion-resistant steels and alloys have appeared. The results of these studies showed that the machinability coefficient of these materials is very low and can reach values ​​​​of 0.15 ... 0.20. Therefore, instrumental materials scientists still have much work to do in this area to resolve this issue.

[0003] The prototype should be considered an experimental method for determining the machinability coefficient of parts made of carbon and low-alloy steels [1].

[0004] A disadvantage of the experimental method for determining the machinability coefficient of carbon and low-alloy steel parts, especially in production conditions, is that when producing a new grade of metal from the base metal, its machinability must be determined again. This requires the use of a certain amount of metal for samples, tooling, time, and energy, thereby incurring certain financial costs.

[0005] The technical result of the filed application for an invention is a method for analytically determining the machinability coefficient of materials made from new carbon and low-alloy steels based on the energy and mechanical properties of these materials.

[0006] The technical result achieved is based on the scientific position of the work [2], which states that in the process of plastic deformation of solids, the density of internal energy U i (J / mm 3 ) in the slip planes of dislocations reaches a critical value U * , equal to the melting enthalpy Hs, upon reaching which the sample material is destroyed. For steel, Hs = 10 J / mm 3 In this case, the internal energy consists of two parts: the energy of various types of defects U e (vacancies, dislocations, etc.) and the thermal component of the internal energy U т , which is determined by the heating temperature of a solid. Based on these principles of the mechanical-energetic approach to the strength and fracture of solids, it was proposed to evaluate the machinability of the new material K обрwhen compared with the one used using the ratios of the intensity coefficients of accumulation of internal energy of defects in the cutting process, K i for new material and K э for the used (standard), when changing the voltage from the physical (MPa) to the ultimate strength These coefficients represent the ratio of the difference in magnitude between the critical density of internal energy U * , at which the shift of chip elements occurs, and the accumulated initial internal energy before turning U o to the size test and reference

[0007]

[0008]

[0009] Coefficient K обр will be equal

[0010]

[0011] After some mathematical operations, we obtain the final formula for the analytical determination of machinability Kобр new material

[0012] relative to the standard

[0013]

[0014] Here

[0015]

[0016]

[0017]

[0018]

[0019] where U oi, U тоi, U еоi - the initial level of internal energy and its components: thermal and energy of defects, of the test sample made of a new grade of steel; U oэ, U тоэ, U еоэ - the initial level of internal energy and its components: thermal and energy of defects, a reference rod sample made of steel 45, GOST 1050-88; TK оэ,оi - initial temperature in Kelvin of the reference and test sample made of another steel grade; HV оэ,оi - initial hardness in MPa of the reference and test sample made of another steel grade; Coefficients 0.0055 (J / mm3 deg) and 0.00089 (J / mm 3 MPa) were obtained by recalculation from reference literature. All energy components in formulas (4)…(8) have the dimension J / mm 3 .

[0020] The machinability coefficient for grade 15 steel, calculated using the proposed analytical method, was 1.37, while for grade 55 steel it was 0.85 relative to the standard grade 45 steel, which is qualitatively confirmed by experimental data from other specialists. It should be noted that the proposed analytical method also allows for determining the machinability coefficient of heat-resistant and corrosion-resistant steels and alloys, but this requires fairly accurate energy and mechanical properties of these materials from literary sources (see equation 4), which is a rather complex task for open publication.

[0021] The proposed analytical method allows determining the machinability coefficient of samples made from new steel grades without conducting materially and energy-consuming experiments, ensuring the presence of distinctive features from the prototype, which meets the criterion of novelty.

[0022] Sources of information:

[0023] 1. Tashlitsky N.I. Influence of mechanical properties and thermal conductivity of steels on their machinability. - M.: Mashgiz, 1952. 84 p.

[0024] 2. Fedorov V.V. Thermodynamic aspects of strength and fracture of solids. Tashkent: Fan Publishing House, UzSSR, 1979. 168 p.

Images