RU2792101C1 - Method for hardening woodworking tools made of chromium and chromium-silicon steels - Google Patents

Abstract

FIELD: thermal hardening of metals; hardening woodworking tools.

SUBSTANCE: method stipulates for the imposing of continuous laser radiation along the back face of a woodworking tool with a CO₂ laser with a laser beam power density of 25-45 MW/m² and a linear speed of the laser beam of 10-15 mm/s in one pass, while the width of the formed track is the same with the diameter of the focused laser radiation. The proposed method can be used for woodworking tools with a thickness of 10 to 25 mm.

EFFECT: increased strength and service life of woodworking tools made of chromium and chromium-silicon steels.

2 cl, 2 dwg 1 tbl

Description

The invention relates to the field of thermal hardening of metals, in particular, to methods for hardening woodworking tools.

The prior art method of surface laser hardening processing of materials [Kovalenko V.S. Hardening of parts with a laser beam. - Kyiv: Technique, 1981. - 131 p.], which is a sequential hardening treatment of the cutting tool during laser irradiation. When using this method, the hardness and depth of the surface hardened layer are controlled.

This method has the following disadvantages:

- hardening is carried out along the front face, that is, when regrinding a woodworking tool, the hardened layer is removed directly;

- due to repeated overlapping, when scanning the hardened area, tempering zones appear (areas with reduced mechanical characteristics);

- long duration of the technological cycle due to multiple repetitions;

- the lack of consideration of the influence of the entire area subjected to laser impact on the strength of the tool and its durability period.

The closest method to the proposed is a method of laser processing of parts of bodies of revolution from tool steels [Patent RU 2734826 C1. IPC C21D 1/09. Application No. 2020120549 dated 06/22/2020, published: 10/23/2020, Bull. No. 30], which consists in the simultaneous rotation and axial movement of the part with the processing of its surface by a continuous laser beam with a degree of overlap of laser paths of 10÷15%, the power density of the laser beam is 80÷90 W/mm ² , the diameter of the laser beam spot is 3 mm and at a linear speed of the laser beam of 6 mm/s. When implementing this method, an increase in the wear resistance of the said rotating part under conditions of increased contact loads is provided, and the range of laser-hardened parts with increased dimensions of the working parts is also expanded.

However, this technical solution is not effective when used to harden a woodworking tool for the following reasons:

- formation of overlap zones with reduced mechanical characteristics;

- the impossibility of controlling the structural state and the level of mechanical properties in depth from the hardened surface;

- it is impossible to form a hardened layer in the zone of a woodworking tool directly involved in the cutting process.

The technical result of the proposed technical solution is to increase the strength and durability of woodworking tools made of chromium and chromium-silicon steels.

The technical result is achieved by processing with continuous laser radiation along the back face of a woodworking tool with a CO ₂ laser with a laser beam power density of 25-45 MW / m ² and a laser beam linear speed of 10-15 mm / s in one pass after hardening and high tempering, in this case, the width of the formed track coincides with the diameter of the focused laser radiation.

The proposed method can be used for woodworking tools with a thickness of 10 to 25 mm.

The width of the formed track can vary from 5 to 15 mm, depending on the requirements for the number of regrinds of the woodworking tool during its operation.

The method is carried out by forming on the front and back faces involved in the cutting process, the so-called self-sharpening effect, which consists in the fact that the parts of the woodworking tool that experience different degrees of wear have different mechanical characteristics, while it is the cutting edge that should have the greatest mechanical characteristics. .

It was noted (see Fig. 1) that when laser processing with continuous laser radiation with the formation of a track parallel to the cutting edge, chromium and chromium-silicon steels, the mechanical properties change smoothly deep into the surface layer. Processing is carried out in the following modes: laser beam power density 25 - 45 MW / m ² , laser beam linear displacement speed 10-15 mm / s, track width coincides with the diameter of the focused laser radiation (beam diameter 5-15 mm), processing is carried out in mode without surface melting.

In this case, on the example of steel 9XC, the microhardness varies from values of 800-900 kg/mm ² to the microhardness of the base material 400-500 kg/mm ² .

The method is carried out as follows.

The finished woodworking tool made of chromium and chromium-silicon steels, after hardening and high tempering, is processed by a single scanning with continuous laser radiation with a power density of 25 - 45 MW / m ² at a speed of 10-15 mm / s, with the formation of a track parallel to the cutting edge at a given distance from her. To reduce the negative effect of atmospheric oxygen during heating and cooling, the treatment area is protected with an inert gas - argon.

The choice of the power density of continuous laser radiation, the speed of linear movement, the width of the laser track and the distance from the track to the blade of the woodworking tool is based on the amount of allowance to be removed and the required number of regrinds to ensure a uniform decrease in mechanical characteristics on the front face of the woodworking tool in accordance with the matrix of the experiment ( see table).

Analyzing the table, it can be noted that the highest hardness is provided at a power density of continuous laser radiation of 40 MW/mm ² and regardless of the speed of the laser beam. The travel speed affects the depth of the hardened zone in the following way: as the processing speed increases, the processing depth decreases.

The choice of the main parameters of laser processing proposed in the method should ensure the formation of a hardened area on the cutting edge in accordance with figure 2.

In this case, the change in mechanical characteristics occurs from the cutting edge deep into the tool along the front edge. Due to this, a longer preservation of the geometry of the cutting edge during the operation of the tool is ensured, which means that there is an increase in the period of durability of the woodworking tool.

Table

Power density 15 mm/s 12.5 mm/s 10 mm/s Layer thickness total/middle (microhardness at point) Layer thickness total/middle (microhardness at point) Layer thickness total/middle (microhardness at point) 30.5 MW/ ^m2 - - 858 kg/ ^mm2 - - 154 µm/77 µm (794 kg/ ^mm2 ) 35.6 MW / m ² 762 kg/ ^mm2 - 824 kg/ ^mm2 190 µm/95 µm (752 kg/ ^mm2 ) - 339 µm/170 µm (752 kg/ ^mm2 ) 40.8 MW/ ^m2 894 kg/ ^mm2 - 894 kg/ ^mm2 313 µm/157 µm (752 kg/ ^mm2 ) - 273 µm/137 µm (752 kg/ ^mm2 ) 45 MW/ ^m2 824 kg/ ^mm2 - 824 kg/ ^mm2 475 µm/238 µm (795 kg/ ^mm2 ) - 653 µm/327 µm (841 kg/ ^mm2 ) 25 MW/ ^m2 - - 824 kg/ ^mm2 - - 958 µm/ 479 µm (841 kg/ ^mm2 )
At a depth of 0.75 mm - 713 kg / mm ² 32 MW/ ^m2 733 kg/ ^mm2 938 kg/ ^mm2 858 kg/ ^mm2 833 µm/417 µm (713 kg/ ^mm2 )
At a depth of 0.75 mm - 752 kg / mm ² 1091 µm/546 µm (795 kg/ ^mm2 )
At a depth of 0.75 mm - 795 kg / mm ² 1167 µm/584 µm (613 kg/ ^mm2 )
At a depth of 0.75 mm - 644 kg / mm ²

Claims (2)

1. A method for hardening a woodworking tool made of chromium and chromium-silicon steels, including hardening, high tempering and subsequent processing with continuous laser radiation, characterized in that the processing with continuous laser radiation is carried out along the rear face of the woodworking tool using a CO ₂ laser with a laser power density beam 25-45 MW/m ² and the linear speed of the laser beam 10-15 mm/s in one pass, while the width of the formed track coincides with the diameter of the focused laser radiation. 2. The method according to p. 1, characterized in that the woodworking tool with a thickness of 10 to 25 mm is strengthened.

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