JPH0259190A - Method for cutting thick plate by laser beam - Google Patents

Abstract

PURPOSE:To cut a increased thick plate through laser beam at a high cutting speed by gouging part of a thick plate in the direction of plate thickness through a preceding coaxial nozzle and jetting supersonic speed assistant gas from a succeeding nozzle into the gouged groove. CONSTITUTION:Part of the thick plate 1a having a thickness H0 is gouged by laser light 5 coming from a preceding coaxial nozzle 3 and a condenser 4 and preceding assistant gas 6 at a gas pressure Pf at a depth Hg. Supersonic speed assistant gas 8 having a gas pressure Pr is jetted from a divergent nozzle 9 of a succeeding nozzle 7a for supersonic wave arranged tandem into a gouged groove of a gouged zone 2a by the nozzle 3 and a cutting zone 2b of a thick plate is cut by the jet gas flow through a rear nozzle 7a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for laser cutting a thick plate suitable for decommissioning a nuclear reactor, particularly for dismantling stainless steel thick plate members such as reactor internal structures.

[Conventional technology]

The principle of the conventional laser cutting method for thin steel plates using tandem nozzles is shown in the side view of Figure 3.A leading coaxial nozzle has a laser condensed irradiation axis and an assist gas injection axis of gas pressure Pf arranged coaxially. 3, the thin plate 1b with a thickness of several dragons is cut, and the dross remaining within the kerf width is removed by gas pressure P.
The trailing nozzle 7b injects only the assist gas r at an inclination angle θr, thereby reducing dross adhering to the back surface of the plate.

However, this tandem arrangement nozzle cutting method is
The purpose is to prevent highly viscous dross from remaining within the kerf width and adhering to the back surface of the plate when cutting a thin plate, especially stainless steel. The flow velocity is low due to atmospheric pressure, and the effect of preventing dross adhesion is determined by the target position δ of the trailing nozzle in the plate thickness direction.
When z = 0.35mm, the height of dross adhesion is 0.0
It is good at about 511.

However, when applying this tandem arrangement nozzle cutting method to cutting several tens of thick stainless steel plates, the low-speed assist gas flow diffuses within the width of the car when cutting the thick plate, and the distance from the nozzle end increases. As the flow rate increases, the flow rate decreases dramatically, making it impossible to cut the blade accurately.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
It is an object of the present invention to provide a method for laser cutting a thick plate, which improves the cutting speed and increases the thickness of the plate that can be cut.

[Means to solve the problem]

To this end, the present invention provides a method for laser cutting a thick plate by arranging trailing nozzles that inject only assist gas from behind the preceding coaxial nozzle that simultaneously performs laser irradiation and assist gas injection, and in order to laser cut a thick plate. The method is characterized in that a part of the thick plate in the thickness direction is gouged, and then supersonic assist gas is injected from the divergent-type trailing nozzle into the gouging groove.

[Effect]

In the method of the present invention, the supersonic assist gas flow of the trailing nozzle increases its jet reach, melts the remaining plate thickness in the groove gouged by the leading nozzle, and scatters it out of the underside of the plate. .

〔Example〕

An embodiment of the method of laser cutting a thick plate according to the present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the embodiment;
FIG. 2 is a diagram showing the relationship between plate thickness and cutting speed in a specific example.

In FIG. 1, using a leading coaxial nozzle 3, a laser beam 5 passes through a condensing lens 4, a leading assist gas 6 having a gas pressure Pf, and a plate thickness H.

A part of the thick plate 1a is gouged to a depth HG, and a supersonic jet of gas pressure Pr is applied from the divergent nozzle 9 of the supersonic trailing nozzle 7a arranged in tandem into the gouging groove of the gouging area 2a by the leading coaxial nozzle. The assist gas 8 is injected, and the thick plate cutting area 2b by the trailing nozzle is cut by the jet gas flow.

Figure 2 shows the relationship between plate thickness and cutting speed in a specific example of cutting 5IJS304 material using the method shown in Figure 1. From this figure, it can be seen that as the trailing nozzle gas pressure Pr increases, the cutting speed improves and It is clear that the reachable distance of the jet gas flow increases and the thickness of the plate that can be cut increases.

〔Effect of the invention〕

According to the present invention, when laser cutting a thick plate by arranging in tandem a trailing nozzle that injects only assist gas from behind a leading coaxial nozzle that simultaneously performs laser irradiation and assist gas injection, the preceding coaxial nozzle By gouging a part of the thick plate in the thickness direction, and then injecting supersonic assist gas from the trailing nozzle, which has a dipazent type inside the gouging groove, the cutting speed is increased and the thickness of the plate that can be cut is increased. The present invention is of great industrial benefit as it provides a method for laser cutting an increasing number of slabs.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the laser cutting method for a thick plate of the present invention, and FIG. 2 is a diagram showing the relationship between plate thickness and cutting speed in a specific example of the same method. FIG. 3 is a side view showing the principle of conventional tandem arrangement nozzle cutting, and FIG. 4 is a diagram showing the relationship between the cutting speed and the height of attached dross in conventional tandem arrangement nozzle cutting. 1a... Thick plate, 1b... Thin plate, 2a... Gouging area, 2b... Thick plate cutting area, 6... Leading coaxial nozzle, 4... Condensing lens, 5... Laser Light, 6...
Leading assist gas, 7a... supersonic trailing nozzle, 7b
... Trailing nozzle, 8... Supersonic assist gas, 9.
...Divergent nozzle. Agent: Patent Attorney Masa Tsukamoto Figure: ￥-S WCRer? Article chart

Claims (1)

[Scope of Claims] When laser cutting a thick plate by arranging in tandem a trailing nozzle that injects only assist gas from behind a leading coaxial nozzle that simultaneously performs laser irradiation and assist gas jetting, the preceding coaxial nozzle cuts the thickness as described above. A method for laser cutting a thick plate, characterized by gouging a part of the plate in the thickness direction, and then injecting supersonic assist gas from the divergent-type trailing nozzle into the gouging groove.