JPS6053248B2 - Underwater gas cutting method for ultra-thick plates such as mild steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In underwater gas cutting, the thicker the plate, the more difficult it is for the cutting oxygen flow to reach the bottom surface, making it easier for water to enter the cut portion during cutting.

Needless to say, if water is mixed in, the temperature of the cutting section will drop and the cutting will be interrupted. This water contamination occurs from the surface of the cut section, the bottom surface, and the rear cut groove.

To prevent contamination from the surface, as shown in torch 1 in Figure 1, move the torch as close as possible to the base material and let air flow around the outer periphery to prevent water from entering, or use a water curtain for continuous trees to emit water in a conical shape. By filling the preheating section within the water curtain with combustion gas from the preheating flame and letting the gas out in the form of small bubbles, it is possible to prevent water from entering. However, these methods of preventing water from entering from the surface of the base material using gas, water, etc. are not new at all. The problematic water intrusion is from the bottom of the base material and from behind the cut section.

Intrusion from the bottom surface of the base material 5 or the cutting groove 9 rises along the rear surface of the oxygen jet 2 during cutting, when the cutting oxygen 2 turns backward and floats up, as shown in FIG. The flow is turbulent, entraining water, blowing the water up close to the cutting oxygen outlet, and mixing the water with the cutting oxygen in the water cutoff area. Water also enters the oxygen stream 2 directly from the cutting groove 9 .
This cools the preheating section and also mixes into the cutting oxygen, interrupting the cutting. This phenomenon becomes more pronounced as the plate thickness increases. The present invention focuses on the above-mentioned phenomenon in which water enters from the bottom side of the base material and from within the cutting groove during underwater gas cutting of ultra-thick plates such as mild steel, analyzes this phenomenon, and develops measures to prevent it. be.

Next, a detailed explanation will be given using the drawings. Note that mild steel and the like include gas-cuttable steel, such as high-strength steel, hard steel, and nodular cast iron. In contrast to the conventional method shown in FIG. 1, FIG. 2 shows an explanatory diagram of an embodiment of the present invention.

Underwater gas cutting torches that flow protective air or a water curtain around the cutting point are already well known, so torch 1 shows only the vicinity of its spout, but torch 7 in Fig. 2 similarly shows only the vicinity of its spout. shows. However, in the case of the present invention, the cutting oxygen, preheating Nagatsuki nozzle 2a, and the protective air flow nozzle 4a, which will be described later, are
Since these are integrated into one unit, oxygen and combustion gas are sent to both nozzles, but since this is also well known technology, a diagram of the torch body showing its structure has been omitted. The torch 7 used in this invention emits a protective air flow 4 that follows the cutting oxygen flow 2 and passes through the cutting groove 9 behind the cutting nozzle 2a of the underwater cutting torch, which surrounds the outer periphery of the heating part with a protective air or water curtain. This includes a nozzle 4a.

Although the cutting nozzle 2a and the protective air flow nozzle 4a may be independent and have separate gas supply sources, they are integrated as in this embodiment and have a common torch body (not shown). It is more practical. This is because the protective air flow 4 in this embodiment is an oxygen flow, and the nozzle 4a, like the nozzle 2a, utilizes a commercially available cutting nozzle. A cross section of the embodiment of the torch according to the invention shown in FIG. 2 is shown in FIG.

Two nozzles 2a and 4a are adjacent and fixed by a connecting member 10, and the outer periphery thereof serves as a protective air outflow nozzle 3a. A cutting oxygen stream 2 and a preheating flame (not shown) are emitted from the nozzle 2a, a protective air flow (in this example, an oxygen stream and a preheating gas (not shown) are emitted from the nozzle 4a, and protective air flows out from the nozzle 3a). Proceed in the direction of the arrow.

Although the explanation of the cutting phenomenon will be omitted, the cutting oxygen flow 2 cuts into the base material 5 of a very thick plate such as mild steel, and creates a cutting groove 9 behind it (
(See Figure 4). Conventionally, the protective air flow 4 was not located behind the cutting oxygen flow 2. As shown in FIG. The water in the cutting oxygen stream 2 is mixed in, becomes an upward flow A of bubbles, and also sends moisture to the upper part of the cutting oxygen stream 2. As a result, the purity of the cutting oxygen decreases (cutting ability decreases), and the base material near the passage is deprived of heat of evaporation. According to the present invention, as shown in FIG. The protective air flow 4 cannot pass through the conventional ascending path in which the raw flow 2 passes through the base material 5 and rises. Therefore, the protective airflow 4
It turns to the rear of the air and becomes an upward flow B that rises together with the protective airflow. The protective air flow 4 not only moves the floating flow of the cutting oxygen flow 2 to the rear, but also removes the water in the cutting groove 9! The infiltration of air is also blocked by the action of the airflow curtain. Therefore, the cutting oxygen flow 2 and the protective air flow 4
Almost no moisture can enter the cutting groove 9 between the cutting oxygen flow 2 and the base material in the vicinity, and the cutting oxygen stream 2 and the base material in the vicinity are protected from water penetration and cooling. The gas used for the protective airflow 4 may be air, but
When using air, nitrogen is mixed into the cutting oxygen stream 2 to reduce oxygen purity.

As a result, the cutting ability is reduced, so it is preferable to use oxygen as the protective air flow as in the above embodiment. Although only a cutting oxygen tip for penetrating the cutting groove 9 may be used as the protective airflow nozzle 4a, it is usually better to use a cutting oxygen nozzle that also has a preheating flame outlet.

This is because the volume covered by the protective air 3 that prevents water from entering from the surface of the base material 5 has increased due to the addition of the protective air nozzle 4a, so the amount of combustion gas in the protective atmosphere must also be increased. The embodiment torch 8 shown in FIG. 5 is for a case where the thickness of the base material 5 is further increased, and a cutting oxygen tip 6 is installed at an angle between the cutting oxygen nozzle 2a and the protective airflow nozzle 4a. ing.

Tip 6 toward the bottom of the base material where the preceding cutting oxygen flow 2 weakens.
It is possible to send in a fresh cutting oxygen flow 2" from the base material. It goes without saying that the protective air flow 4 is effective in this case as well. <Experimental results> Base material plate thickness 150 m Oxygen for preheating flame Flow rate 50e/min Propane + methyl acetylene flow rate 12e/min Cutting oxygen pressure
9kg/c! Under the common conditions above, when using the conventional cutting method (Fig. 1), cutting speed is 10 cm/min (oxygen flow rate 300 e/min), when cutting long lengths, there may be some uncut parts or notches (irregular cuts). is recognized.

O When using the cutting method of the present invention (Fig. 2), the cutting speed is 15
cm/min 7 (oxygen flow rate 50 to 150 e/min) No uncut parts or notches are observed even when cutting long pieces.

That is, the cutting efficiency and cutting quality were significantly increased by the present invention. Although the above description has been made using two embodiment torches, the embodiments of the present invention can be varied in various ways without changing the gist thereof.
Needless to say, it can be applied.

The plate thickness is 80jR1! Although it is intended for the above, it is also effective for less than that. Underwater cutting is performed in a special environment, and if cutting is interrupted, it is extremely difficult to restart from that point.

As a result, cutting is interrupted and work efficiency is significantly reduced. The present invention has revealed that the cause of interruptions that often occur during cutting of extremely thick plates such as mild steel is due to the intrusion of water into the bottom surface of the base material and into the cutting grooves.

As a preventive measure, we installed a through air flow following the cutting groove immediately after the cutting oxygen flow, so when the used oxygen floats up, water on the bottom of the base material is rolled up and given to the cutting oxygen flow, and the water inside the cutting groove is Direct contact with the cutting oxygen flow has been significantly reduced. As a result, not only the cutting interruption phenomenon has been drastically reduced, but also the above-mentioned efficiency has been achieved by protecting the cutting oxygen flow and preventing cooling of the passage base material.
This resulted in an improvement in quality.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of underwater cutting with a conventional torch, Figure 2
3 is a cross-sectional view of the torch shown in FIG. 2, FIG. 4 is an explanatory plan view, and FIG. 5 is an explanatory view of another embodiment of the present invention. 2... Cutting oxygen flow, 2a... Its nozzle, 3... Protective air, 4... Protective air flow, 4a... Its nozzle. .

Claims (1)

[Scope of Claims] 1. A nozzle is advanced behind the cutting nozzle of the underwater cutting torch to emit a protective air flow that follows the cutting oxygen flow and penetrates the cutting groove, and both of the nozzles are configured to prevent moisture from flowing between the cutting oxygen flow and the protective air flow. An underwater gas cutting method for ultra-thick plates such as mild steel, which is characterized by maintaining a gap where it is difficult for the metal to penetrate. 2. An underwater gas cutting method for ultra-thick plates such as mild steel, in which the protective air stream is an oxygen jet in the cutting method according to claim 1.