JPS6258828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in plasma cutting torches that use plasma arcs to cut materials.

As is well known, plasma cutting can cut non-ferrous metals that cannot be cut with gas, so it has become popular as a very convenient cutting method. In particular, the plasma jet cutting method disclosed in Japanese Patent Publication No. 47-9252 is effective because it injects water from around a plasma arc to the cut end of the material to be cut, improving the quality of the cut end and increasing the cutting speed. It is widely used as a cutting method. The cutting equipment to which this method is applied has a relatively large capacity (60 to 200 kW).
(class), is mainly suitable for cutting thick plates rather than thin plates, and can cut at high speed and with high quality.

As mentioned above, the plasma jet cutting method is fully suitable for preventing sagging of the cut end of the material to be cut and improving the quality of the cut surface, but the plasma jet cutting method installed in the plasma cutting equipment that uses this method is Cutting torches have various problems as listed below.

(i) Handling is inconvenient due to the large diameter of the torch;
It is particularly unsuitable for manual cutting.

(ii) Since a high-current plasma arc is generated, the electrodes and nozzles, which are subjected to high loads, must be directly cooled with water, and the shapes of these parts are complex and expensive.

(iii) In addition to a dedicated pump for forcibly circulating cooling water and a cooling water supply circulation path, a separate outflow path is required to jet water to the cut end of the material to be cut.

(iv) Since the cooling water outflow passage (small hole) provided around the nozzle hole is exposed facing the material to be cut, there is a risk of damage due to the effects of molten metal scattering during cutting. Therefore, it is necessary to protect the nozzle to prevent a decrease in cutting ability.

(v) A large-scale drainage facility is required to prevent the cutting phenomenon from becoming waterlogged due to the flow rate of cooling water injected to the cut end of the material to be cut.

On the other hand, in recent years, there has been a demand for a small-capacity (10 to 30 kW class) plasma cutting device that can easily cut thin plates with a thickness of about 1 to 25 mm by holding a torch. In this case, the main focus is on improving the quality of the cut surface, even if the cutting speed is somewhat reduced, and the torch used for cutting is required to be small, simple in structure, easy to use, and have excellent workability. .

The present invention not only satisfies the above requirements, but also
The purpose of this torch is to provide a plasma cutting torch that improves the environment at a cutting site, and includes a torch body provided with a cooling water passage, a nozzle attached to the tip of the torch body, and an internal structure inside the torch body and nozzle. In a torch consisting of an electrode inserted into the
A cooling water outflow path that communicates with the cooling water passage is provided between the nozzle and a nozzle cap arranged on the outer periphery of the nozzle, and the cooling water is directed inward from the cooling water outflow path toward the plasma arc and directed around the nozzle hole. is ejected into the atmosphere to cool the torch and the cut end of the material to be cut.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a torch body provided with a passage 8a through which cooling water 9 flows, 2 is an electrode inserted into the torch body 1 via an insulator 3, and 4 is an O-ring attached to the tip of the torch body 1. As shown in FIGS. 2a and 2b, the nozzle is attached through a nozzle 7b, and a small groove 4a serving as a cooling water outflow passage can be provided on the outer circumferential surface of the nozzle, as shown in FIGS. Instead, a chamfered surface 4b may be provided on the outer periphery of the nozzle 4 as shown in FIG. 2c. 5 is a nozzle hole provided in the nozzle 4 to face the electrode 2; 6 is a nozzle cap attached to the torch body 1 via an O-ring 7a so as to surround the outer periphery of the nozzle 4; 6 and the nozzle 4, a cooling water passage 8b communicating with the cooling water passage 8a,
8c is formed.

The cooling water outflow passage 8c is provided to be inclined inward with respect to the plasma arc 14 so that the cooling water 9 acts on the plasma arc 14 and the cut end 11a of the material to be cut 11. 10 is a working gas passage formed between the electrode 2 and the nozzle 4; 11 is a material to be cut; 11a is a cut end of the material to be cut 11; and 12 is a power source connected to the electrode 2 and the material to be cut 11.
13 is a working gas supplied into the torch body 1 and the nozzle 4, and this working gas may be Ar, for example.
(Argon) gas, Ar+H ₂ (Hydrogen), N ₂ (Nitrogen)
Gas, Ar+ _N2 , etc. are used.

Next, the operation of this embodiment configured as described above will be explained.

The material to be cut 11 is cut at a cut end 11a by a plasma arc 14 generated between the material to be cut 11 and the electrode 2 by a power source 12. At this time, the cooling water 9 flowing through the cooling water passage 8a provided in the torch body 1 passes through the cooling water outlet passages 8b and 8c formed between the nozzle 4 and the nozzle cap 6, and then enters the nozzle hole 5.
is released into the atmosphere around the torch, that is, both the nozzle 4, the nozzle cap 6, and the cut end 11a of the material to be cut 11 are cooled.

When the cooling water flows through the cooling water outlet paths 8b and 8c, a portion of the cooling water is vaporized to improve the cooling efficiency of the outer circumference of the nozzle 4, so that the nozzle 4 is sufficiently cooled. In addition, as the cooling water flows out from the cooling water outflow path 8c, a mixed fluid of water, steam, and spray acts to surround the plasma arc 14, increasing the energy density of the plasma arc 14, and causing the arc 14 to reach a high temperature. The vaporized fluid acts very effectively on the cut end 11a of the material to be cut 11, and a high-quality cut surface is obtained by preventing shoulder sagging of the cut end 11a, reducing heat effects, and preventing oxidation. Furthermore, the area around the cut portion is surrounded by the mixed fluid, thereby reducing the scattering of molten metal and the generation of gas and fume.

Another embodiment shown in FIG. 3 has the tip of the nozzle cap 6 protruding from the tip of the nozzle 4, and
An insulating fastening ring 16 is inserted into the nozzle cap 6 so as to surround the outer periphery of the tip of the torch body 1, and an insulating guide ring 17 surrounds the outer periphery of the tip of the nozzle cap 4. As shown in FIG.
This embodiment differs from the embodiment shown in FIG. 1 in that a small groove 17a is provided on the inner peripheral surface in contact with the outer peripheral surface of the cooling water outlet to form a cooling water outflow passage. The rest of the structure is the same as that in FIG. 1, so a description thereof will be omitted.

With this configuration, the tip of the torch, that is, the tip of the nozzle cap 6, can be cut with the tip of the nozzle cap 6 in contact with the material to be cut 11, making manual cutting easier. By keeping the length constant, a uniform and good cut surface can be obtained. Also nozzle 4
Since the nozzle cap 6 is located inside the nozzle cap 6, there is no risk of being affected by molten metal scattering or adhesion, and the nozzle cap 6 is covered with a film of a mixed fluid of water, spray, and steam and is sufficiently cooled. Therefore, there is no risk of damage from arc heat and molten metal.

The relationship between the plasma arc current and the cooling water flow rate in the above embodiment is as shown in FIG. In other words, with respect to increases and decreases in plasma arc current, A is the range where the cooling water flow rate is appropriate, B is the range where the amount of cooling water is too small and causes overheating of the torch, and C is the area where the amount of cooling water is too much than necessary. be. Although the torch is not excessively cooled in this region C, excessive cooling water is supplied to the cut end of the material to be cut, which may lead to a decrease in cutting ability and flooding of the cutting site.

Therefore, by flowing an appropriate flow rate of cooling water as shown in area A, the water and steam heated to high temperatures due to arc heat can be mixed from the cooling water outlet provided around the nozzle hole without impairing the cooling of the torch. The fluid can flow into the cut end of the material to be cut to effectively act and react.

FIG. 6 shows an example of the results of cutting stainless steel and aluminum plates using the torch of the present invention, and shows the relationship between plate thickness and cutting speed.

Ar+N ₂ gas and Ar+H ₂ gas, which generate higher energy density than Ar gas, were used as working gases (flow rate 30/min). The appropriate amount of cooling water is flowing according to the arc current value.

It goes without saying that increasing the arc current improves cutting ability, but especially for thin plates,
When cutting with a small-hole nozzle and a small current arc, the thermal effect was very small and a high-quality cut surface with no dross adhering to the cut surface was obtained.

As explained above, the present invention is very convenient because it has a simple structure, is easy to handle, and can easily perform cutting operations while keeping the tip of the torch in contact with the material to be cut.

In addition, not only does it require a small amount of cooling water, and there is no need for a cooling pump to forcefully circulate the cooling water.
A high-quality cut surface can be obtained by preventing sagging of the cut end of the material to be cut, reducing heat effects, and reducing oxidation.
Furthermore, the environment at the work site can be improved by reducing the scattering of molten metal due to cutting and by reducing the generation of gas and fume.

[Brief explanation of the drawing]

FIG. 1a is a longitudinal cross-sectional view showing an embodiment of the plasma cutting torch of the present invention, FIG. 1b is a view taken from the direction of the arrows in FIG. 1, and FIG. FIGS. 2b and 2c are bottom views and modified views of FIG. 2a, FIG. 3 is a vertical sectional view showing another embodiment of the present invention, and FIGS. FIG. 5 is a diagram showing the relationship between plasma arc current and cooling water flow rate in an embodiment of the present invention, and FIG. 6 is a diagram showing an embodiment of the present invention. be. 1... Torch body, 2... Electrode, 4... Nozzle, 5... Nozzle hole, 6... Nozzle cap, 8
a... Cooling water passage, 8b, 8c... Cooling water outflow path, 11... Material to be cut, 11a... Cut, 17
……Insulating material.

Claims (1)

[Scope of Claims] 1. A plasma cutting torch consisting of a torch body provided with a cooling water passage, a nozzle attached to the tip of the torch body, and an electrode inserted into the torch body and the nozzle, wherein the nozzle and the A cooling water outflow path that communicates with the cooling water passage is provided between the nozzle cap placed on the outer periphery of the nozzle, and the cooling water is directed from this cooling water outflow path toward the plasma arc, tilting inward and into the atmosphere around the nozzle hole. A plasma cutting torch characterized in that it is configured to emit a jet of water to cool the torch and the cut end of a material to be cut. 2. The plasma cutting torch according to claim 1, wherein the tip of the nozzle cap protrudes from the tip of the nozzle, and an insulating material is attached to the inner surface of the tip of the nozzle cap.