RU2517632C1 - Increasing physical-mechanical properties of tool and structural steels by volumetric pulsed laser hardening - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: article is processed by pulse laser with efficient pulse energy of 60-500 J, pulse power density of 1.2·10¹⁰-4.3·10¹¹ W/m², wavelength of 1.064·10^-6 m, pulse duration of 0.8·10^-3 s, beam diameter of 1.2·10^-3-2.5·10^-3 m and distance fro irradiated point to surface being hardened of 12-30 mm.

EFFECT: higher physical-mechanical properties.

7 dwg

Description

The invention relates to the field of obtaining materials with new properties, in particular in the manufacture and repair of various machines and mechanisms.

A known method of hardening a cutting tool made of high speed steel by impact laser processing (A.S. No. 1078939 A (USSR)), which consists in the fact that after heat treatment produce impact laser treatment with an energy density of 5-30 J / mm ² .

This method can only be used for high speed tool steels.

There is also known a method of surface pulsed laser processing of materials (Kovalenko V.S. Hardening of parts with a laser beam. - Kiev: Technika, 1981. - 131 p .; SU 1752514 A1 07.08.1992; A.G. Grigoryants, A.N.Safonov. Fundamentals of laser thermal hardening of alloys. - Moscow: Vysshaya Shkola, 1988, book 3, pp. 98-102, 118-119, book 6, pp. 106-107, 124; Laser shot peening technology. Institute of Laser Physics (St. Petersburg)), which is a sequential hardening of the product material upon laser irradiation. The main disadvantages of surface pulsed laser processing of products are as follows:

- simultaneous hardening of several surfaces is unacceptable;

- adjacent surfaces after pulsed laser processing are weakened against the action of brittle fracture forces;

- the process is time-consuming (due to repeated irradiation of one product) and requires significant energy costs;

- when the product is worn or regrind, the hardened layer is removed.

Zones of material hardening by various laser methods are shown in FIG. 1, where 1 is shock and pulsed laser processing methods (1-3 mm); 2 - method of volumetric pulsed laser hardening (18-30 mm).

In the patent RU 2460811 C1 “Method for improving the performance of carbide cutting tools using pulsed laser processing” a method of volumetric pulsed laser hardening (hereinafter referred to as OILU) for hardening tools made of hard alloys is proposed. This patent discusses general approaches for using OILU for various materials. In addition, the term "pulsed laser treatment" is used to refer to surface heat treatment using a pulsed laser [Yaresko S.I. Physical and technological fundamentals of hardening of hard alloys. - Samara: publishing house of the Samara Scientific Center of the Russian Academy of Sciences, 2006. - 244 p.]. To eliminate possible misunderstandings, we propose the name of the developed method - “Volumetric pulsed laser hardening” [I. Pinakhin Volumetric pulsed laser hardening of cutting tools. Hard alloys. LAP LAMBERT Academic Publishing GmbH & Co. KG., 2012. - 122 p.].

The main task, the solution of which the claimed method is directed, is to increase the technical resource of products at the lowest energy and labor costs.

The technical result of the invention is to obtain materials with improved physico-mechanical properties, which after wear or regrinding are preserved.

The specified technical result is achieved by the fact that in the method of volumetric pulsed laser hardening of instrumental and structural materials, the product is laser-treated using a pulsed laser with a useful pulse energy of 60-500 J (pulse power density of 1.2 · 10 ¹⁰ -4.3 · 10 ¹¹ ), wavelength 1.064 · 10 ^-6 m, pulse duration 0.8 · 10 ^-3 s, beam diameter 1.2 · 10 ^-3 -2.5 · 10 ^-3 m, distance from the irradiation site to the hardened surface 12 -30 mm.

Hardening schemes of products according to the prototype and the claimed method are presented in figure 2, where 3 is a pulsed laser; 4 - hardenable product; 5 - a device for installing a hardened product.

The method of hardening carbide cutting tool is as follows. On the pulse laser 1, the pulse generation mode is set with an energy of 100 to 500 J (depending on the type and size of the cutting tool) and a duration of 0.8 · 10 ^-3 s. The light pulse is focused on the surface of the hardened product 2, which is fixed in the device 3. Irradiation is performed by a single pulse. The place of exposure depends on the material, shape and purpose of the hardened product. So, for example, for a cutting tool, irradiation is performed on the front surface for interchangeable plates or on the rear auxiliary surface for brazed plates.

As a result of irradiation, a change in the microstructure of the material due to the passage of the shock wave is observed, which is confirmed by the data of X-ray diffraction analysis. This leads to an increase in the physicomechanical properties of the hardened material. In FIG. 3 shows the mechanism of volumetric pulsed laser hardening.

The experimental tests of tool materials (hard alloys, high-speed steels) showed that volumetric pulsed laser hardening increases their strength by 1.2-1.3 times, abrasive wear resistance by 1.3-1.4 times and a decrease in the coefficient of variation of wear by 1 , 5 times, which leads to the following results of industrial tests:

- increase the resistance of cutting tools in 2.0-2.5 times;

- reducing the coefficient of variation of resistance by 1.3-3.1 times;

- increase gamma-percent resistance by 1.7-2.8 times;

- reduce the number of spalling, breakdowns in the running-in area of the cutting tool by 2.7 times;

- increase the value of the optimal feed in 1.2-1.3 times;

- increase productivity by 1.1-1.2 times.

It should also be noted that hardening is three-dimensional in nature, for example, with five regrindings, an increase in the resistance of the cutting tool by 5-7.5 times, an increase in processing productivity by 20-40% without additional time and money for hardening, are observed. In addition, increasing the stability of the properties of the cutting tool (coefficient of variation of resistance, gamma-percent resistance) allows it to be used in an automated production environment.

As a check of the proposed method in comparison with the prototype were tested through-cutters under the following conditions:

- processed material - gray special K-1 cast iron;

- tool material - hard alloy VK6;

- cutting tool - a through cutter with a soldered plate (γ = 10 °, α = 8 °, φ = 60 °),

- processing equipment - machine tool MK 6026;

- operation - boring-turning on a copy;

- the processed surface - a casting peel;

- the workpiece is a piston ring D = 150 ÷ 110 mm, δ = 3 ÷ 6 mm;

- cutting conditions: cutting speed ν = 42 m / min, feed S = 0.15 mm / rev, cutting depth t = 1.0 mm;

- hardening modes: radiation power density 1.25 · 10 ¹¹ W / m ² , wavelength: 1.064 · 10 ^-6 m, pulse duration: 0.8 · 10 ^-3 s, beam diameter: 2.0 · 10 ^-3 m, the distance from the main cutting edge to the irradiation site is 14.8 mm; place of exposure - auxiliary posterior surface; the number of pulses is 1.

The influence of volumetric pulsed laser hardening on the structure and properties of structural steels was also revealed. As an example, the effect of volumetric pulsed laser hardening on armco-iron is considered. An armco iron ingot measuring 10 × 10 × 100 millimeters was obtained by induction remelting in vacuum. Samples of 10 × 10 × 20 millimeters cut from this ingot were annealed in an oven at a temperature of 1050 ° C for an hour and cooled with an oven. The surface of the samples after annealing is etched in nitric acid to remove scale without introducing any distortion into the microstructure and surface properties (GOST 5639-82). Metallographic analysis carried out with an inVia Raman Microscope microscope at a magnification of × 200 and microhardness measurements using a PMT-3 hardness tester according to GOST 9450-76 showed that all samples have the same coarse-grained structure and allowable deviations of microhardness values (± 5%).

The samples were irradiated with a GOS 1001 laser under the following operating conditions: wavelength 1.064 · 10 ^-6 m, pulse duration 0.8 · 10 ^-3 s, laser beam diameter 1.2 · 10 ^-3 -2.5 · 10 ^-3 m, useful radiation energy of 50-150 J (radiation power density of 10 ¹⁰ -1.3 · 10 ¹¹ W / m ² ). After irradiation, a metallographic analysis of the samples and measurement of their microhardness were performed. The results made it possible to identify the extremum of changes in the structure and microhardness of the samples, which corresponds to a laser beam diameter of 1.4 · 10 ^-3 m, useful radiation energy of 80 J (radiation power density of 6.4 · 10 ¹⁰ W / m ² ).

In Fig. 4 (initial sample) and Fig. 5 (specimen that has passed OILA (the distance from the irradiation site is 15 millimeters)) it is shown that, for irradiated samples, crushing of the initial grains into smaller fragments is observed, which, as a rule, leads to a change in physic - mechanical properties of materials, the appearance of internal stresses, etc.

Figure 6 shows the dependence of the coefficient of change of microhardness on the distance from the irradiation site. The coefficient of change in microhardness was determined by the formula:

$$K_{HV}=\frac{H{V}_{\mathrm{ABOUT}\mathrm{AND}L\mathrm{At}}}{H{V}_{\mathrm{and}\mathrm{from}x}},(\mathrm{one})$$

where HV _ref and HV _OILU are, respectively, Vickers microhardness of unstrengthened and passed OILU samples.

As can be seen from Fig.6 (confidence interval: ΔK _HV = ± 0.0224) there is an increase in microhardness of Armco iron after OILU. In this case, the maximum increase in microhardness (10%) corresponds to a distance of 16 millimeters from the irradiation site.

A drawing of a cutting tool, which indicates the place of irradiation and the distance from the place of irradiation to the main cutting edge is shown in Fig.7.

Claims (1)

The method of volumetric pulsed laser hardening of products from instrumental and structural materials, which consists in the fact that the product is subjected to laser processing using a pulsed laser with a useful pulse energy of 60-500 J, pulse power density of 1.2 · 10 ¹⁰ -4.3 · 10 ¹¹ W / m ² , a wavelength of 1.064 · 10 ^-6 m and a pulse duration of 0.8 · 10 ^-3 s, while the beam diameter is 1.2 · 10 ^-3 -2.5 · 10 ^-3 m, and the distance from the place of irradiation to the hardened surface - 12-30 mm.

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