JPH01133687A - Plasma cutting torch - Google Patents

Abstract

PURPOSE:To cut a thick plate at a small cone angle with a large amount of current by injecting cutting gas supplied from a tip opening of an electrode as an axial-flow plasma arc from a bottleneck nozzle and cooling these via a cooling electrode base. CONSTITUTION:The electrode 40 made of Hf, etc., is held by a cylindrical body 48 and the cooling electrode base 42 and inert gas such as oxygen from a cutting gas supply pipe 44 is injected from a through hole on its center. Further the bottleneck nozzle 52 surrounding the electrode 40 is provided via the electrode base 42 and a gap via an insulator 50 and a nozzle cap 54 is provided to its periphery via space. A pilot arc with a small amount of current generated between the above-mentioned electrode 40 and bottleneck nozzle 52 by a power source 58 is pushed out from the bottleneck nozzle 52 by the cutting gas. Hereby, the axial-flow plasma arc with the large amount of current is generated between the electrode 40 and a material 20 to be cut by a main power source 60. During that time, a cooling medium is passed through the periphery of the cutting gas supply pipe 44, the indentation of the upper part of the cooling electrode base 42, said space, etc., to maintain application of said large amount of current and the material 20 to be cut of the thick plate can be cut.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plasma cutting torch improved to be able to cut thick steel plates [Prior Art] A plasma torch for cutting plate materials is shown in Figs. There is one with the structure shown in Figure 3. Figure 2 (Special Publick Showa 6O-247491
), an electrode 18 made of a material such as hafnium or zirconium that is less likely to be damaged even in high-temperature active gases is attached to the center of the bottom surface of the cooling stand II tz to which cooling water is supplied, and the narrowing nozzle 14 is installed with a gap around these electrodes. Active gas (oxygen gas or air) is placed in the gap and descends while swirling.
is supplied to create a plasma arc flame 16, and the material to be cut 20 is cut with this plasma arc flame.

When the active gas is swirled, the center becomes low pressure, and the electrode 18
Since it is located in the center, arcs are likely to be generated from the electrodes, and arcs will not be generated from the bottom surface of the electrode stand 12, which is made of metal (W4), and damage to the lower part of the electrode stand can be avoided. The advantages include being able to fix the arc at the center.

However, when the gas flow is swirling, the downward ejection force becomes weaker, and the cutting force becomes weaker, resulting in a steel plate (30 to 4011 or more).
The problem is that it is difficult to cut. In addition, as shown in Figure 2(b), the cut part has a tapered shape that widens at the top (
θ is large), and the shoulder portion 20a has a rounded shape.

In the plasma torch 10 of FIG.
A second nozzle 26 is disposed around the nozzle 24, and an inert gas such as hair argon or nitrogen is supplied to the first nozzle 24, and an active gas is supplied to the second nozzle 26 to generate a plasma arc 32. This plasma arc 34 is an axial flow and does not swirl, so it has a strong ejection force and is suitable for cutting thick plates. It cannot generate a large current (more than 150A is difficult, but 250A is possible in Figure 2), so it is not suitable for cutting thick plates.

As shown in FIG. 3 (bl), the cut portion becomes a deep groove type with no widening (θ is small), and the shoulder portion also maintains a right angle state.

However, there is a problem in that an inert gas is also required in addition to the active gas. Electrode 2 uses tungsten as an inert gas
This is to protect 2. If tungsten is wrapped in an inert gas, its melting point will be 3360°, and 2 when wrapped in an active gas.
It becomes much hotter than 300°.

However, the use of inert gases also creates other problems. That is, when argon is used as the inert gas, dross 35 is likely to be generated at the cut portion, and when nitrogen is used, nitrides are generated on the cut surface, resulting in welding defects when welding is performed later.

Plasma torches commonly used are those shown in Figures 2 and 3, but the one shown in Figure 2 is more widely used.

[Problem that the invention seeks to solve]

In this way, with conventional plasma torches, the cutting force is weak because the plasma arc flame is rotating, the shape of the cutting part is not good, or the cutting force is still low because the plasma arc flame is an axial flow but cannot be made with a large current. There are problems such as being weak and requiring inert gas.

The object of the present invention is to improve these points and provide a plasma torch that has a large cutting force, can cut thick plates, has a good cut shape, and does not require an inert gas.

[Means for solving problems]

FIG. 1 shows a plasma cutting torch of the present invention.

Reference numeral 40 denotes an electrode made of hafnium or zirconium, which is shaped like a truncated cone and has a hundred holes in the center, through which cutting gas (active gas such as oxygen or air) is supplied.

42 is a cooled electrode stand, and the electrode 4 is placed in the recess at the bottom of this electrode stand.
0 is inserted. The electrode stand 42 is also provided with a hole aligned with the hole of the electrode 40, and a cutting gas 46 is supplied to this hole from a cutting gas supply pipe 44. 48 is a cylindrical body that surrounds the supply pipe 44 and supplies cooling water to the electrode stand 42 . 50 is an insulating material, 52 is a narrowing nozzle, 54 is a nozzle cap, 56
is an insulating collar. Further, 58 and 60 are power sources, 62 is a cooling water inlet pipe, 64 is a cooling water outlet pipe, and 66 is a nozzle stand.

[Effect]

In this plasma cutting 1.-ch, a voltage is applied by the pilot power source 58 to the electrode 40 via the cylindrical body 48 and the electrode stand 42, and to the constriction nozzle 52 via the nozzle cap 54. A pilot arc is generated between the nozzles 52.

The pilot arc has a small current of about 30A.

The cutting gas 46 passes through the supply pipe 44 and the electrode stand 42 to the electrode 40.
is supplied to the electrode, passes through the through hole of the electrode, and further passes through the narrowing nozzle 5.
2 and ejects downward. When the cutting gas 46 blows out of the electrode 40, it forces the pilot arc between the electrode 40 and the constriction nozzle 52 downward, thereby causing the main power supply 60
As a result, a plasma arc is generated between the electrode 40 and the material to be cut 20, and this becomes a plasma arc flame that cuts the material to be cut 20.

This plasma arc flame 68 is an axial flow and does not rotate.

In addition, the arc current from the main power supply 60 can be as large as 250A, and together with the fact that the frame is an axial flow, it is possible to cut steel plates such as 70mm thick with a small taper angle. Can be done.

The cooling water is supplied to the inlet vibro 2, the space between the cylindrical body 48 and the supply pipe 44, the recess of the electrode stand 42, the space between the narrowing nozzle 52 and the nozzle cap 7 54, the outlet vibro 4, etc. and cools the electrode 40, constriction nozzle 52, etc. Since the electrode 40, the constriction nozzle 52, etc. are sufficiently cooled, a large current can be applied, and the cutting ability can also be improved in this respect.

〔Example〕

Output current 250A, 02 gas 601/min, cutting speed 100w/min, main power voltage 210mm, nozzle diameter 2.5mm, standoff 10++n, it was possible to cut a 701 mm thick steel plate, and the cut surface was also good. .

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to cut steel plates as thick as 30mm to 700mm by plasma cutting.
There are also advantages such as no need for inert gas.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a plasma torch of the present invention, and FIGS. 2 and 3 are explanatory views of a conventional plasma torch. In FIG. 1, 40 is an electrode, 42 is a cooling electrode stand, 44 is a cutting gas supply pipe, 50 is an insulating material, 52 is a constriction nozzle, and 54 is a nozzle cap. Applicant Nippon Steel Welding Industry Co., Ltd. Representative Patent Attorney Minoru Aoyagi-1 Figure 1

Claims (1)

[Claims] An electrode (40) having a through hole in the center, a hole aligned with the through hole, and a recess on the top surface,
A cooled electrode stand (42) that holds the electrode on the lower surface, a cutting gas supply pipe (44) that supplies cutting gas to the through hole of the electrode through the hole of the cooled electrode stand, and an insulating material (50). a constriction nozzle (52) that surrounds the cooled electrode stand and the electrode via a gap; and a nozzle cap (54) that surrounds the constriction nozzle so that a space is formed.
and a cooling mechanism (62, 48, 64) for flowing a cooling medium through the cutting gas supply pipe, the recess in the upper part of the cooled electrode stand, and the space between the constriction nozzle and the nozzle cap. torch.