JPS61176472A - Metal piercing method - Google Patents

Abstract

PURPOSE:To increase a piercing efficiency by spouting on arc part the jet water of high pressure and high speed through the circular aperture of the hollow rod as well as using the continuously fed metal hollow rod as an electrode. CONSTITUTION:A hollow metal rod 1 is used as consumable electrode and the voltage is impressed from a power source 9 to the space with the material 2 to be pierced. On the other hand the jet water 5 of high pressure and high speed is fed to the circular aperture of the electrode 1 by a water feeding pump 10 and sent directly into the arc part. The molten metal and generated gas are discharged through a gap 6 by an arc 7. All the jet water 5 is therefore utilized effectively in the discharge of metal chip and generated gas. With this method the flow velocity of the jet waterstream 5 becomes constant irrespective of the piercing depth, and the piercing efficiency of the arc 7 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for perforating any metal capable of carrying two currents. Traditionally, electric discharge machining has been used for precision machining of thin plates as a metal drilling method.

Ultrasonic processing, electron beam processing, laser processing, etc. have been developed, and plasma arc processing is also available for thick plates.

Oxygen lance machining, consumable electrode type arc machining, etc. have been developed. The present invention belongs to the consumable electrode type arc processing method among the above-mentioned drilling methods, and has high drilling speed and excellent characteristics as a drilling method for thick plate metals in particular.

Conventional technology FIG. 2(a) shows a conventional drilling method of this type.

This will be explained using (b). In Fig. 2(a), a solid wire (electrode wire) l is used as the processing electrode.
It is continuously fed by the M-pole feeding motor 8. A voltage is applied by WN2 between the electrode wire 1 and the workpiece 2 to generate an arc 7.

The electrode wire 1 and the workpiece 2 are melted at the same time, and high-pressure, high-speed jet water 5 is ejected from a slit 4 provided concentrically around the outer periphery of the current-carrying tip 3.

Drill holes by forcibly removing molten metal. However, according to this method, the jet water 5 is fed to the arc generation location, that is, the molten metal part, through the gap 6 between the electrode wire 1 and the drilled hole, so the jet water 5 is fed from the surface of the workpiece. When the direction of the metal flow and the generated gas flow discharged from the bottom of the hole toward the surface becomes opposite, and the drilling depth becomes deeper.

The molten metal flow, the generated gas flow, and the jet water flow collide within the gap 6, and the discharge of the molten metal is suppressed, making it impossible to perforate the thick plate.

FIG. 2(b) was developed as a means to solve the above problem. That is, a metal strip plate is used as the consumable electrode 1, and the gap 6 between the electrode 1 and the drilled hole is enlarged by continuously supplying it and by giving it rocking or repeated rotation of 180 degrees. , improving water circulation.

Also, by setting the jet water spout 4 of high pressure and high speed in one direction, the jet water passes through the gap 6 and reaches the arc generating part 7, and passes along with the molten metal through the gap 6a on the opposite side to the water inflow side. It flows in the opposite direction to the inflow direction and discharges the molten metal. With this method, the jet water flows in one direction, which solves the problem shown in FIG. 1(a).

Problems to be Solved by the Invention The drawbacks of the above-described drilling method are that the jet water outlet 4 is provided on the surface of the material 2 to be drilled.

Most of the jet water hits the surface and is reflected.

The ratio of the molten metal flowing through the gap 6 and contributing to the discharge is small. Second, as the drilling depth increases, the flow rate of the jet water decreases, and the ability to discharge molten metal decreases. Thirdly, even if rocking or repeated rotation of 180 degrees is performed, the gap 6 into which the jet water flows changes due to the movement of the electrode, and the amount of water flowing in changes, causing the flow velocity at the arc generation point to change. be. Fourthly, metal debris that is being discharged gets stuck between the perforated surface and the swinging or rotating electrode, causing a short circuit between them and generating an arc. For this reason, the surface where the holes were once perforated is melted again, and a portion of the electrode strip is also melted, resulting in irregular hole diameters. Fifth
At the arc generation point 7, water is decomposed by the arc heat to generate water vapor and gas. These gases are emitted in all directions around the electrodes, obstruct the inflow of jet water 5, and at the same time remain in the vicinity of the arc generating part. This gas is originally produced by the decomposition of water and has the property of combusting with an explosion. As the drilling depth increases, explosive combustion of the generated gas occurs frequently.

Regular drilling becomes impossible.

Means for Solving the Problems The present invention solves the above-mentioned problems and makes it possible to drill holes in planks. FIG. 1 shows two embodiments of the present invention. Using hollow rod 1 as a consumable electrode,
A voltage is applied between the drilled material 2 and the drilled material 2 by a power source 9. Feed the hollow electrode rod.

An arc 7 is generated by contact with the material to be drilled.

Melting the hollow electrode rod and the material to be drilled is similar to the conventional method. On the other hand, high-pressure, high-speed jet water 5 is fed by a water pump 10 through the inner hole 11 of the hollow rod, and is directly fed to the location where the arc occurs, and the arc 7 eliminates the molten metal and generated gas. Metal debris and generated gas are discharged through the gap 6 between the hollow electrode rod and the drilled hole. All of the supplied jet water is effectively used for removing and discharging metal debris and generated gas. Also.

By using a constant flow type water pump (for example, a plunger type water pump) as the water pump, a constant flow of water is supplied regardless of whether the length of the hollow rod is different or when drilling a deep hole. Metal debris and generated gas can be discharged by a constant velocity water stream.

Metal debris discharged with the water flow accumulates on the surface of the drilled material,
This will cause deterioration of drilling efficiency. In order to prevent this accumulation, it is effective to provide a water spout 12 approximately parallel to the surface of the material to be drilled, and to spray water from the water spout 12 to scatter the discharged metal debris.

Also, to keep the hole diameter constant and improve the hole surface.

It is important to prevent short circuits caused by metal debris during the discharge process, and an effective countermeasure to this is to form a thin insulating coating on the hollow rod. However, since power cannot be supplied by the two-current supply chip 3, the length of the hollow electrode is limited. When drilling deep holes, drilling can be continued by changing the rod.

Effect: Since the metal melted by the arc is quickly removed, the molten metal scraps become fine powder, and during the discharge process, they come into contact with both the hollow electrode rod and the material to be drilled within the gap 6, and an arc due to a short circuit occurs between them. Since this occurs infrequently, the perforation diameter remains relatively constant.

The accuracy of the drilling surface is also improved. Furthermore, since the generated gas is quickly exhausted, it does not stagnate and cause an explosive combustion phenomenon.

As described above, the main feature of the present invention is that water is directly supplied to the point where the arc occurs, and the flow velocity of the jet water flow near the arc is constant regardless of the drilling depth.

This is the first technology developed through repeated basic research to clarify the interaction between water jets and arcs.

In other words, an arc is generated due to a short circuit or dielectric breakdown between the consumable electrode and the workpiece, and the resulting heat melts both, but when a water flow acts on this arc.

The momentum of the water removes the molten metal, and at the same time the arc is extinguished by the increase in potential gradient.

By feeding the consumable electrode, the arc is re-ignited and the arc is extinguished in a similar manner, repeating the cycle as the drilling progresses. When the flow rate of the acting water is slow, the ability to remove molten metal decreases, and the duration of the arc increases (the amount of metal that is melted and removed in one arc occurrence also increases. Therefore, the cycle of arc generation decreases). As the arc becomes longer, the arc becomes unstable.

On the other hand, if the water flow rate is sufficiently high, the molten metal will be quickly removed, so the amount of metal melted in one arc will decrease, and the frequency of arc occurrence will increase. This is because the arc current is low and the two cycles are short.

The stability of the arc is also improved.

As mentioned above, in order to obtain a constant arc phenomenon during drilling regardless of the depth of the hole, it is important to always maintain the water flow acting on the arc under a constant condition.

It is clear that the most effective way to achieve this is to eject water from near the arc generation point.

The width of the gap 6 between the hollow electrode rod 1 and the perforated surface of the perforated material 2 can be adjusted by selecting the arc voltage.

That is, by increasing the arc voltage, the gap widens and the resistance to discharge water and metal debris becomes smaller, which is particularly effective when drilling deep holes.

As the power source 9, either a direct i* power source or an alternating current power source can be used, but the perforation efficiency with direct current reverse polarity is the best.

An example according to the final example method is shown in FIG. 3A. This has an outer diameter of 8φ,
A hollow rod with an inner diameter of 3φ was used as the consumable electrode, mild steel was used as the material to be drilled, and the arc current was 700A.

This figure shows the perforation characteristics when a jet water flow rate of 10 Jl/min is used. Even if the drilling depth increases, there is little decrease in drilling efficiency, and deep holes can be drilled.

For comparison of the effects of the invention, Figure B shows the results of drilling a mild steel strip electrode (10 mm x 2 mm) using the rocking method.

Although the same current and water flow as in A were used, the drilling efficiency was poor and there was a tendency for the drilling depth to saturate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. FIG. 2 is a schematic diagram showing a conventional consumable electrode drilling method. FIG. 3 is a diagram showing an example of the drilling performance of the present invention. In the figure, 1-- consumable electrode for drilling, 2-- workpiece material,
3... Current-carrying tip, 4... Slit for jet water flow, 5... Jet water, 6 - Gap between drilled hole and consumable electrode, 7... Arc, 8... Electrode feeding motor. 9...Power supply, 10...Water pump, 11...Inner hole of hollow rod, 12...Water spout 1-Total 21 tone (b)

Claims (1)

[Claims] 1. Using a continuously fed metal hollow rod as an electrode, an arc is continuously generated between the material to be perforated and the electrode, and the hollow rod electrode and the material to be perforated are melted, and the inner hole of the hollow rod is melted. A drilling method characterized by continuously drilling holes while eliminating molten metal and generated gas by jetting high-pressure, high-speed jet water from the tip of a hollow rod to an arc portion through a hollow rod. 2. The drilling method according to claim 1, wherein a water spout is provided for the purpose of preventing deposition of molten metal around the drilling opening on the surface of the material to be drilled. 3. The metal drilling method according to claim 1, using a hollow rod whose outer surface is coated with an insulating coating.