JPS5911644B2 - Surface hardening equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface hardening apparatus for uniformly hardening the surface layer of a steel object by irradiating a laser beam onto the steel object having an oxide film formed on its surface.

A conventional surface hardening device is shown in FIG.

In the figure, 1 is a C02 laser oscillator, 3 is a condenser (parabolic 15 mirror), 4 is processed 5 is a steel product (for example, mild steel, low alloy steel containing nickel, chromium, etc.), 6 is alumina; carbon coating It is a material. To explain the hardening in the apparatus shown in FIG. 1, the wavelength 10.6 emitted from the CO2 laser oscillator 1 is
A laser beam 2 of 20 μm is focused by a condenser 3 onto the surface of a steel object physically coated with alumina or carbon.

Since alumina/carbon has an extremely high absorption rate for the C02 laser beam, most of the irradiated high power density laser beam is absorbed by the alumina/carbon 25 layer 6, and the optical energy is converted into thermal energy. This thermal energy is transmitted to the surface of the steel object 5, and only the surface layer of the steel object 5 is rapidly heated, and the metal structure of the surface layer of the steel object 5 is austenitized. The laser beam irradiation surface is currently heated 3
As the surface layer moves away from the zero point, the rapidly heated surface layer is rapidly cooled, and the austenitic structure of the surface layer is turned into martensite and hardened. This hardening characteristic depends on the thermal energy characteristic (power density of 35 degrees, total energy amount) transferred from the alumina/carbon layer 6 to the surface of the steel object 5. To explain the formation of the film 6, a colloidal solution made by dissolving fine powder of alumina and carbon in a liquid such as water is physically applied to the surface of the steel object 5, and then dried to form the film 6.
is formed. Since this alumina/carbon film 6 is physically applied, it is extremely difficult to control the thickness of this film 6. Regarding film thickness and hardening, when the film 6 is thin (1 μm or less), the amount of laser beam absorption in the film decreases, and the power density and total energy amount of thermal energy transmitted to the surface of the steel object 5 decreases. becomes lower, and the quenching depth becomes shallower. Moreover, if the thickness of the coating becomes too thick (5 μm or more), the power density of thermal energy transmitted to the surface of the steel object 5 decreases, and the quenching depth becomes shallow. However, it has the disadvantage that it is not possible to uniformly harden the surface of the steel product. In addition, the melting points of alumina and carbon in the coating material phase are 2048℃ and 2048℃, respectively.
Since 3500°C is higher than the melting point of iron, 1539°C, when the intensity of the laser beam irradiated to the physically applied coating 6 increases, the surface of the steel object 5 melts, and it melts into the liquid phase of the steel object. Alumina and carbon are mixed in as a solid phase and roughen the surface shape. Furthermore, it is difficult to separate the slag of alumina carbon and steel products from the base material 5. As described above, since conventional surface hardening equipment physically coats the surface of the steel product with an alumina/carbon film, it is difficult to form a film with a uniform thickness.

Therefore, there is a drawback that uniform surface hardening characteristics cannot be obtained. In addition, it is difficult to separate the slag made of the coating material and the steel from the base material, which has the disadvantage of roughening the surface. This invention was made to eliminate the drawbacks of the conventional equipment as described above, and by forming a dense and uniform iron oxide film on the surface of steel products using an oxide film former, uniform hardening can be achieved. The purpose is to provide a surface hardening device that can harden the surface of the surface. This invention will be explained below with reference to the drawings. FIG. 2 is an explanatory view showing an embodiment of the surface hardening apparatus of the present invention, and FIG. 3A and FIG. First, the formation of an oxide film on the steel surface will be explained.

Oxide film forming device 11 for forming an oxide film on the surface of steel products
As shown in Fig. 3, there are two types: a dry corrosion method and a wet corrosion method. In Fig. 3A, 13 is a surface heating device;
14 is an oxygen injector. Molecules such as oxygen-acetylene flame and plasma jet emitted from the surface heating device 13,
The atoms and ionized high temperature gas 15 collide with the surface of the steel object 5 attached to the processing jig 4, and the surface of the steel object 5 is heated. Oxygen molecules injected from the oxygen injector 14 collide with this heated surface, the heated surface of the steel object 5 is oxidized, and a dense iron oxide film 16 is formed. When the temperature is constant, the oxidation rate is inversely proportional to the thickness of the iron oxide film 16, and the thickness δ of the iron oxide film 16 is δ2Kp! i+C (Kp, C are constants, t is reaction time), and the thickness δ tends to be saturated with respect to time t. When the thickness of the iron oxide film 16 is constant, the oxidation rate increases as the temperature increases. Therefore, the thickness of the iron oxide film can be controlled by controlling the heating temperature and heating time of the surface of the steel article. However, since the oxidation rate is inversely proportional to the thickness of the iron oxide film, it is relatively easy to control the thickness of the oxide film 16. Steel products 5
The surface temperature of is controlled by a surface heating device 13. When the surface heating device 13 is composed of an oxygen-acetylene flame generator, the fluid characteristics (flow rate, flow rate) of the oxygen or acetylene gas injected from the nozzle or the steel object 5
The surface temperature of the steel article 5 can be controlled by controlling the distance between the steel body 5 and the oxygen-acetylene flame generator. Further, when the surface heating device 13 is composed of a plasma jet generator, the surface temperature of the steel object 5 can be controlled by controlling the electric power injected into the plasma gun. The heating time t can be controlled by controlling the feed rate of the processing jig 4. Therefore, the iron atoms of the steel object 5 and oxygen molecules are chemically reacted by the oxide film forming device 11 using a dry corrosion method consisting of a surface heating device 13 and an oxygen injector 14, and a dense layer is formed on the surface of the steel object 5. A uniform iron oxide film 16 can be formed. It is also possible to uniformly form an iron oxide film on the surface of a steel product by using a wet corrosion method as shown in FIG. 3.

In this figure, 17 is a mixed aqueous solution of sodium hydroxide and potassium nitrate, 18 is a bathtub containing this mixed aqueous solution, 19 is a heating device, and 20 is a carrying rod. A bathtub 18 contains a mixed aqueous solution 17 of sodium hydroxide and potassium nitrate having a predetermined mixing ratio. This mixed aqueous solution 17
is 50 to 150 depending on the heating device 19 such as a gas burner.
The temperature is controlled at a predetermined temperature between ℃. The steel object 5 is carried into the mixed aqueous solution 17 in the bath by the transport rod 20, and an iron oxide film 16 is formed on the surface of the steel object 5. Although the thickness δ of the iron oxide film 16 increases with time, its growth rate dδ/Dt tends to decrease with time. When the mixing ratio and temperature of the mixed aqueous solution 1r are constant, the thickness of the iron oxide film 16 can be controlled by controlling the time during which the steel article is introduced into the mixed aqueous solution 15. When the iron oxide film 16 of a predetermined thickness is formed, the steel object 5 is attached to the processing jig 4 by the carrying rod 20. The mixing ratio and temperature of the mixed aqueous solution 17 are controlled as shown in FIG.
By controlling the delivery time to the mixed aqueous solution 17, it is possible to chemically react the iron atoms of the steel object 5 with oxygen molecules and form a dense and uniform iron oxide film 16 on the surface of the steel object 5. . Next, hardening will be explained. In FIG. 2, 1 is a CO2 laser oscillator, 3 is a concentrator, 5 is a steel product, 11 is an oxide film former, and 12 is a gas injector.

As shown in Figure 2, from the CO2 laser oscillator 1 to the wavelength 10
．． A laser beam 2 of 6 μm is focused by a condenser 3 onto a steel object 5 on which a uniform iron oxide film 16 has been formed on the surface by an oxide film former 11 .

The power density of the laser beam on this laser beam irradiation surface is extremely high. Iron oxide film 1 for CO2 laser beam
Since the absorption rate of 6 is extremely high (more than 90%), the CO2 laser beam is efficiently absorbed by the iron oxide film 16, where the light energy is converted into thermal energy. The converted thermal energy is transferred to the surface of the steel object 5. The vicinity of the surface of the steel object 5 (to a depth of 0.3 to 0.7 Tm) is rapidly heated (800 to 1340°C) by the thermal energy transferred from the iron oxide film 16, and the metal structure is austenitized. . The CO2 laser beam irradiation surface moves at a predetermined speed on the surface of the steel object 5, and as the laser beam irradiation surface moves away from the vicinity of the heated surface, the heated surface vicinity is rapidly cooled. When the cooling rate is high as described above, the austenitized structure near the surface becomes martensite, and the near surface of the steel article 5 is hardened.
A shielding gas 21 such as nitrogen or argon is injected onto the CO2 laser beam irradiation surface and its vicinity by the gas injector 12, and oxygen in the air is cut off from the heated surface of the steel object 5. The oxidation reaction does not proceed.
By chemically forming a uniform iron oxide film 16 on the surface of the steel object 5 using the oxide film forming device 11 in this way, the characteristics of the heat source supplied to the steel object 5 can be maintained constant. Therefore, the surface of the steel product 5 can be hardened uniformly. The iron oxide film on the surface of the steel object 5 after being hardened may turn into steam or become brittle flakes depending on the power density of the laser beam irradiation surface, and is also peeled off under the action of the shielding gas jet 21. .

When the steel surface is peeled off and exposed, the steel surface reflects most of the CO2 laser beam (85-97%), so almost no thermal energy is further injected into the steel object 5.

Therefore, even if the power density of the laser beam irradiation surface becomes high, the surface of the steel object 5 can be uniformly hardened without melting (deforming and reducing hardening hardness) the surface of the steel object 5. When the output of the laser beam 2 emitted from the CO2 laser oscillator 1 fluctuates and the power density of the CO2 laser beam irradiation surface increases and the iron oxide film 16 melts, the melting point of the iron oxide (1350-1400°C) It is lower than the melting point of iron (1539°C), and molten iron oxide has extremely good fluidity, so the shielding gas jet 21
Peel off from the surface of the steel object 5.

As the experimental results of this invention, the thickness of the iron oxide film was 2 to 3 μm.
A 370W0C02 laser beam (spot diameter 3.5Tm) was focused on the formed test piece (carbon steel S45C), and the test piece was moved at a speed of 30 cm/min.
Uniformly quenched without melting the surface to a depth of Trtm (
Bitkers hardness of 500 to 600) was achieved.
As described above, according to the present invention, a uniform iron oxide film is formed on the surface of a steel object using an oxide film former, and a laser beam is irradiated onto the surface of the steel object through this iron oxide film.
A laser beam can be efficiently used as a hardening heat source, and the surface layer of a steel product can be hardened uniformly.

In addition, even when the power density of the laser beam irradiation surface increases, the energy input to the steel object can be kept almost constant, making it possible to uniformly harden the surface layer of the steel object without melting the surface. I can do it. Another advantage is that the iron oxide film can be easily peeled off after being irradiated with a laser beam.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional surface hardening device, FIG. 2 is an explanatory diagram showing an embodiment of the surface hardening device of the present invention, and FIG. 3 is an explanatory diagram of an oxide film forming device. In the figure, 1 is a laser oscillation screen, 3 is a condenser, 5 is steel wax, 11 is an oxide film former, 12 is a gas injector, and 16 is an iron oxide film.

Claims (1)

[Claims] 1. A device for hardening the surface of a steel product, an oxide film former that forms a dense and uniform iron oxide film on the surface of the steel product, and a laser that emits a laser beam that moves on the surface of the steel product. A surface hardening device comprising an oscillator and hardening the surface of the steel object by irradiating the surface of the steel object with the laser beam through the iron oxide film. 2. Claims characterized in that the oxide film forming device is comprised of a surface heating device that heats the surface of the steel object, and an oxygen injector that injects oxygen or oxygen mixed gas onto the heated surface of the steel object. The surface hardening device according to item 1. 3. An oxide film forming device is provided with a mixed aqueous solution of sodium hydroxide and potassium nitrate, a bath containing this mixed aqueous solution,
2. The surface hardening device according to claim 1, further comprising a heating device for heating the mixed aqueous solution to 50 to 150°C. 4. Claim 1, characterized in that the laser beam is irradiated onto the steel object by covering the irradiation surface of the steel object with the laser beam and its vicinity with an inert gas such as nitrogen or argon. The surface hardening device described in Section 1.