JPS62222017A - Heat treatment with laser - Google Patents

Abstract

PURPOSE:To enhance a cooling effect after heat treatment with a simple apparatus by forming a water film on the surface of a material, carrying out the irradiation or laser beams and the jetting of an inert gas and forming a water film again by the relative movement of a torch to cool the heat treated part. CONSTITUTION:A water film 5 is formed on the surface of a material 3 to be heat treated by retention or other method. Laser beams 1 are then irradiated on part of the surface of the material 3 from the concentric nozzle 4 of a torch. At the same time, an inert gas 6 such as Ar is jetted from the nozzle 4 to remove the water film 5 at the irradiated part. Since the torch is moving relatively to the material 3 at a prescribed speed, a water film is formed again immediately after the movement to cool the heat treated part. By this method, heat treatment with laser followed by forced cooling is carried out.

Description

[Detailed Description of the Invention] (Industrial Application Field) In recent years, the application of lasers to metal processing has been rapidly progressing.
The scope of application of laser processing is surface hardening, surface alloying, welding,
Among these, the present invention relates to laser heat treatment and laser hardening technology.

(Prior art) Conventionally, in laser hardening, a laser beam (1) is irradiated onto the surface of a material to be hardened (3) to rapidly raise the surface temperature, and then this beam is removed to heat the inside of the material. It is said that the heat treatment is carried out by cooling and hardening only by heat conduction, and as the heat treatment is performed by so-called self-cooling, a quenching liquid is not required and a clean heat treatment can be performed (Figure 6).

However, in the case of this self-cooling, there is a limit to the cooling rate. That is, if the thickness exceeds the limit for the amount of heat input by laser beam irradiation, the cooling rate will not increase. In addition, in the case of continuous irradiation, the temperature of the irradiated material rises with the irradiation, resulting in a preheated state of the material, and the cooling rate decreases.

In order to deal with this problem and increase the cooling capacity, a method was proposed (Japanese Patent Laid-Open No. 59-200718) in which a cooling liquid is sprayed onto the area after laser irradiation, as shown in Figure 7. However, this method also As the process continues, the temperature of the irradiated material (3) may rise and the material may be preheated, making it particularly ineffective for large materials.In addition, this method does not allow the cooling liquid to flow into the laser irradiation area. In order to prevent this, a device is required that blows gas toward the laser irradiation part from another position to prevent the liquid from flowing in, which makes the device complicated.

(Problems to be Solved by the Invention) In order to solve the above-mentioned problems, the present invention provides a laser beam from a torch equipped with a gas injection nozzle concentrically with the laser beam so that the surface of the material to be heat treated is covered with water of a predetermined thickness. The purpose of the present invention is to provide a laser heat treatment method in which beam irradiation and inert gas injection are performed, the laser beam is irradiated while removing water from the part, and the laser irradiated part is again covered with water and cooled by the relative movement of the laser beam. It is something to do.

(Means for Solving the Problems) That is, the present invention is a method of heating or melting a material surface for heat treatment using a laser, in which a water film is formed on the material surface and an inert gas is injected in the same direction as the laser beam. The gist is a laser heat treatment method in which laser irradiation is performed while eliminating a water film, and cooling is achieved by re-forming the water film by moving the irradiation position.

If the surface of the material is to be covered with water of a predetermined thickness, water may be allowed to remain on the surface of the material, but in order to prevent the water temperature from increasing due to irradiation and reducing the cooling capacity, the method shown in Figure 8 is used. It may also be flowed to form a surface laminar flow. The area covered by water is preferably the entire surface of the material, but if there are restrictions due to the shape of the material, it may be possible to submerge only the vicinity of the laser irradiation point.

Furthermore, when processing a round rod-shaped material, it is also possible to immerse the round rod in water and rotate the rod to move the laser irradiation point, as shown in FIG.

It is also possible to irradiate the material surface with the laser beam through a water film, but in that case the laser beam is absorbed by the water, reducing the efficiency of transmission to the material and increasing the water temperature. Therefore, an inert gas is flowed in the same direction as the laser beam, and the gas jet eliminates water from the irradiation point and its vicinity. Therefore, the laser beam will irradiate the area where the water film has been removed.

(Function) If the torch, which emits a gas flow concentrically with the laser beam, is moved relative to the material, a water film is again formed on the surface heated or melted by the laser beam, and the material is rapidly cooled.

If the thickness of the water film is too thin, there will be no cooling effect, so two or more dragons are required.

The gas to be used is preferably an inert gas such as Ar or Nt gas in order to prevent oxidation caused by the atmosphere in the heating part.The range in which the water film is removed by the gas jet varies depending on the area irradiated with the laser beam, but the laser beam directly hits the water film. In order to prevent this and to ensure the cooling effect of the water belly, a water film in an area enlarged by 1 to 10 degrees is removed around the laser beam irradiation area. If the temperature is less than 1, there is a risk that the laser beam will hit the water film, and if it exceeds 10, it will take time for the water film to re-form after heating, and rapid cooling will not be possible.

The laser irradiation part may be circular or may have another shape.

In the case of linear irradiation, rapid cooling can be similarly achieved by using a torch equipped with a slit-shaped nozzle and flowing the laser beam and gas flow.

(Example) Next, examples will be described based on the drawings.

Figure 1 is a schematic diagram showing an example of laser irradiation conditions using the final method.The laser (11 is a 4kW CO It was adjusted to 20fl on the surface of the irradiated material (3).The inner diameter of the gas injection nozzle (4) installed concentrically with the through hole of the laser beam was 4.
The tip position of the nozzle is 20 mm above the material surface. The torch was moved at a speed of 1 m/min.

FIG. 2 shows an example of forming a water film on the surface of the irradiated material (3). In this example, the water film (5) was formed in a stagnation manner so that it formed five layers on the material.

Figure 3 shows the concentric nozzle (4) at the same time as the laser (11 irradiation)
This is a schematic diagram showing a state in which gas (6) is injected from the irradiation position to remove a water film near the irradiation position.
The area where the water film was removed was approximately 10 mm for the laser irradiation area of 5 mm. Since the torch was moving relative to the material (3) at the above-mentioned movement speed, a water hole was formed immediately after the movement and the material was cooled.

(Effect of the invention) A laser beam is irradiated on the test steel plate shown in Table 1 under the above conditions, and the hardness of the center (x point) of the formed molten zone is measured using a Vickers hardness tester to determine the degree of hardening. We considered this (Fig. 4).

The width of the melted area is about 3 cages, and the depth is about 0.5 cages.

Table 1 and Figure 5 show the relationship between the Cl and the hardness of the molten zone for each sample in Table 1 as a result of the above test. ) indicates that the hardness increases and it is easy to burn. In the experimental example, the results were shown for the melted part, but the effect is similar when only heating is performed without melting.

As described above, the present invention allows easy laser heat treatment by forced cooling.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of laser irradiation conditions in the method of the present invention, FIG. 2 is a schematic diagram showing an example of forming a water film on the surface of the irradiated material, and FIG. 3 is a schematic diagram showing an example of the method of the present invention. A schematic diagram showing an example, FIG. 4 is an explanatory diagram of the measurement points of molten zone hardness, FIG. 5 is a comparison diagram of the relationship between (jl and hardness of the molten zone) of quenched samples in the method of the present invention and the conventional method, and FIG. 7 is a schematic explanatory diagram of the conventional laser hardening method using forced cooling. FIG. 8 is a perspective view showing partial water film formation by laminar flow. Figure 9 is a schematic diagram when processing a round bar-shaped material. 1: Laser beam 2: Lens 3: Irradiated material 4: Nozzle 5: Water film 6: Gas flow 2 Figure 3 Figure 4 C (%) C+n melting 8P Tatsuna's listening system Fig. 5 Fig. 6 Fig. 47

Claims (2)

[Claims] (1) In a method of heat treatment by heating or melting the surface of a material with a laser, a water film is formed on the material surface and the water film is removed by an inert gas ejected in the same direction as the laser beam, while the laser is irradiated. A laser heat treatment method characterized by cooling by re-forming a water film by moving the position. (2) A torch for laser heat treatment characterized by having a gas injection nozzle concentrically with the laser beam.