JP2010000511A - Gas cutting method and device for steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a gas cutting device for steel plates which is faster in the cutting speed and piercing time of a thick plate, smaller in the sticking of slag and thermal strain and can expect the reduction of running cost as compared with a conventional cutting device using acetylene gas. <P>SOLUTION: Gaseous mixture in which hydrogen is essential and oxygen and propane gas are added to it, and low-pressure oxygen are jetted from a plurality of preheating holes which are formed on the outer periphery of a nozzle of a cutting torch and the cutting place of the steel plate is preheated until it is heated to glow with a flame which is formed by igniting that gaseous mixture and the low-pressure oxygen. Cutting is performed by jetting high-pressure oxygen from a jetting hole formed in the center of the nozzle of the cutting torch to the cutting place of the red-heated steel plate, oxidizing the steel plate by the flame formed by igniting that high-pressure oxygen and blowing off the cutting place of the steel plate which is molten by oxidation heat with the jet stream of the flame igniting the high-pressure oxygen and cutting along the moving route of the cutting torch is performed by moving the cutting torch in the desired direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steel sheet gas cutting method and apparatus mainly using, for example, hydrogen gas.

An NC gas cutting machine using acetylene gas as a fuel has been used for conventional cutting work of flat steel materials.
Cutting with an NC gas cutting machine using acetylene gas as a fuel has not been put to practical use due to cutting accuracy due to distortion caused by preheating, difficulty in handling due to thermal deformation of the cutting piece, high cost and environmental pollution.
In recent years, the problem of environmental problems due to the increase in the price of carbides used as a raw material for acetylene gas and the debris of carbide called mud generated during refining has become serious.
Therefore, as a substitute for acetylene gas, generally, a low-priced fuel such as LNG, propane, or a mixed gas thereof is used.
For example, in the case of LNG and propane, the unit price of gas is very low, such as about 480 yen / kg for acetylene gas and about 50 yen / kg for LNG and propane, compared to acetylene.
In addition, although the prior literature of this invention was investigated, it was not found.

However, in the cutting with an NC gas cutting machine using LNG or propane gas as a fuel, the cutting speed is about 10% slower than acetylene gas, the piercing time is long, and when the gas leaks heavier than air, the gas accumulates downward. In addition, there are disadvantages in that a gas detector and inspection costs are generated, and the amount of preheated oxygen used at the time of cutting increases.
In addition, plasma cutting, which is currently the mainstream of cutting work, has a problem that it is difficult to apply because flat steel materials are intended for cutting thick plates, and cutting by semi-automatic machine or manual work is still being performed. It was the current situation.
The present invention has been made to solve such problems. Compared to a conventional cutting device using acetylene gas, the cutting speed and piercing time of a thick plate are faster, adhesion of heat and thermal distortion are less, and the running cost is lower. It aims at obtaining the gas cutting method and apparatus of the steel plate mainly using hydrogen gas which is a new fuel which can be expected to be reduced.

  The gas cutting method for a steel sheet according to the present invention is characterized in that hydrogen is mainly used, and a mixed gas obtained by adding oxygen and propane gas and low-pressure oxygen are ejected from a plurality of preheating holes formed in the outer periphery of the crater of the cutting torch. Preheat the cut part of the steel sheet until it is red hot with a flame formed by igniting the mixed gas and low-pressure oxygen, and press the high pressure from the ejection hole formed in the center of the cutting torch at the cut part of the red hot steel sheet The steel sheet is oxidized by a flame formed by igniting the high-pressure oxygen that has been ejected, and the molten steel is blown off by a jet of flame ignited by the high-pressure oxygen. Cutting is performed, the cutting torch is moved in a desired direction, and cutting along the moving path of the cutting torch is performed.

  In the hydrogen gas cutting method for a steel sheet according to the present invention, hydrogen is mainly used, and a mixed gas obtained by adding oxygen and propane gas and low-pressure oxygen are ejected from a plurality of preheating holes formed in the outer periphery of the crater of the cutting torch, Preheat the cut portion of the steel plate with a flame formed by igniting the jetted gas mixture and low-pressure oxygen until it is red hot, and then from the jet hole formed at the center of the crater of the cutting torch at the red hot plate High pressure oxygen is ejected, the steel sheet is oxidized by a flame formed by igniting the ejected high pressure oxygen, and the cut portion of the molten steel sheet is blown off by the jet of flame ignited by the high pressure oxygen. The cutting torch is moved in a desired direction, and cutting is performed along the movement path of the cutting torch. Therefore, hydrogen gas occupying the main body of the mixed gas is changed to acetylene gas. Base and has high convergence rate of combustion or thermal energy, will faster cutting speed and piercing time of the steel sheet, less adhesion or thermal distortion of the slag, and reduction in running costs there is an effect that can be expected.

FIG. 1 is a configuration diagram showing a gas cutting device for carrying out the steel sheet gas cutting method according to the present invention, and FIG. 2 is an explanatory diagram showing a configuration of a crater of a cutting torch of the same cutting device.
In FIG. 1, a seawater electrolyzer 1 that generates hydrogen and oxygen from seawater and a propane gas tank 2 are connected to a gas mixer 3 that mixes hydrogen, oxygen, and propane gas at a predetermined ratio. The mixed gas mixed in the gas mixer 3 is stored in a mixed gas tank 4 which is a so-called surge tank. 5 is an oxygen tank for storing pure water oxygen.

The mixed gas tank 4 and the oxygen tank 5 are opened by cutting the gas operation panel 6 for performing gas supply operation, the electromagnetic valve unit 7 for opening and closing various electromagnetic valves according to the cutting conditions, and various valves before starting the cutting. It is connected to the cutting torch 9 via a safety valve unit 8 that is closed after the end.
A seed fire unit 10 is further connected to the electromagnetic valve unit 7, and the seed fire unit 10 is ignited by an ignition device 11.
The solenoid valve unit 7, the safety valve unit 8, and the ignition device 11 are driven and controlled by a drive signal from the interface panel 13 that receives a drive command from the robot control panel 12.

  The gas control panel 6 includes a manual on-off valve 20 provided in the middle of a mixed gas supply hose 16 connected to the mixed gas tank 4, and two mixed gas supply hoses branched from the mixed gas supply hose 16. Branches from a pressure regulating valve 21 and a pressure meter 22 provided in 17a and 17b, a manual on-off valve 23 provided in the middle of the oxygen supply hose 18 connected to the oxygen tank 5, and an oxygen supply hose 18, respectively. A pressure regulating valve 24 and a pressure meter 25 provided on the two oxygen supply branch hoses 18a and 18b, respectively, are provided on the panel surface.

The two mixed gas supply hoses 17a and 17b and the two oxygen supply branch hoses 18a and 18b are mainly connected to the cutting torch 9 via the solenoid valve unit 7 and the safety valve unit 8 provided in the middle. It is connected.
The electromagnetic valve unit 7 is provided with four electromagnetic valves 7a to 7d, of which three electromagnetic valves 7a to 7c are connected to a cutting torch 9 through a safety valve unit 8, one of which is a seeding unit 10 It is connected to the.

As shown in FIG. 2, the cutting torch 9 has a plurality of high-pressure cutting oxygen injection holes 9a formed in the center, a plurality of gas mixtures formed on the outer periphery of the injection holes 9a and low-pressure preheating oxygen. The preheating hole 9b is provided.
The oxygen supply branch hose 18b is connected to the ejection hole 9a of the cutting torch 9, and half of the plurality of preheating holes 9b of the cutting torch 9 is connected to the oxygen supply branch hose 18a. The other half of the hole 9b is connected to a mixed gas supply branch hose 17a.

Next, the case where the steel plate gas cutting method is implemented using the steel plate gas cutting device according to the present invention will be described.
In this case, the steel sheet to be cut has a thickness of 10 mm to 20 mm.
First, preparations before cutting a steel sheet will be described.
First, hydrogen and oxygen generated by electrolyzing water in the seawater electrolyzer 1 and the propane gas from the propane gas tank 2 are sent to the gas mixer 3, and the so-called ternary gas is mixed in the gas mixer 3. Generate. Then, the mixed gas generated by the gas mixer 3 is stored in the mixed gas tank 4.
The ratio of hydrogen, oxygen, and propane gas constituting this mixed gas is, for example, 52% for hydrogen, 26% for oxygen, and 22% for propane gas, but various ratios depending on the thickness of the steel sheet to be cut Can be.

Next, the manual on-off valve 20 and the manual on-off valve 23 of the operation panel 6 are opened by manual operation.
After that, when a power switch (not shown) of the robot control panel 12 is turned on to bring the robot control panel 12 into an operating state, the robot control panel 12 issues an opening command to the interface panel 13 for the electromagnetic valve unit and the safety valve unit. The interface board 13 that has received these opening commands outputs an opening signal to the solenoid valve unit 7 and the safety valve unit 8, respectively, and the solenoid valve unit 7 that has received the opening signal has four solenoid valves 7a to 7d. The safety valve unit 8 receiving the opening signal opens the three valves 8a to 8c.
In this way, the preheating oxygen is ejected from the plurality of preheating holes 9b in advance, and the pressure is adjusted by the pressure adjusting valve 24 while observing the pressure meter 25 provided in the oxygen supply branch hose 18a. It sets so that oxygen for preheating of the low pressure of 0.5 MPa, for example may be ejected from the hole 9b. This pressure can be variously set according to the thickness of the steel plate to be cut.

Further, oxygen is ejected from the ejection hole 9a in advance, and the pressure is adjusted by the pressure regulating valve 24 while observing the pressure meter 25 provided in the oxygen supply branch hose 18b, so that, for example, 5 MPa from the ejection hole 9a of the cutting torch 9 The high-pressure cutting oxygen is set to be ejected.
This pressure can be variously set according to the thickness of the steel plate to be cut.
In addition, the mixed gas is ejected from the plurality of preheating holes 9b in advance, and the pressure is adjusted by the pressure adjusting valve 21 while observing the pressure meter 22 provided in the mixed gas supply branch hose 17a. The preheating hole 9b is set to eject a preheating mixed gas having a predetermined pressure.

Further, the mixed gas is ejected from the seed fire unit 10, and the pressure is adjusted by the pressure adjusting valve 21 while looking at the pressure meter 22 provided in the branch hose 17 b for supplying the mixed gas. Set so that the preheating gas mixture is ejected.
In this way, the pressure adjustment of the cutting oxygen ejected from the ejection hole 9a of the cutting torch 9, the preheating oxygen ejected from the plurality of preheating holes 9b, the preheating mixed gas, and the preheating mixed gas ejected from the seeding unit 10 is performed. Is completed, the robot control panel 12 outputs a closing command for the solenoid valve unit to the interface panel 13, and the interface panel 13 receiving the opening command outputs a closing signal to the solenoid valve unit 7 and receives the closing signal. The electromagnetic valve unit 7 closes the four electromagnetic valves 7a to 7c.
In this way, preparations before cutting the steel sheet are completed.

As described above, when the preparations before the steel sheet cutting operation are completed, the steel sheet cutting operation is started.
First, the robot control panel 12 outputs an ignition command to the interface panel 13 in accordance with a preset cutting program, and the interface panel 13 receiving the ignition command outputs an ignition signal to operate the ignition device 11 and the electromagnetic valve unit. 7 outputs an open signal to the electromagnetic valve 7d to open the electromagnetic valve 7d to eject the mixed gas from the seeding unit 10 and to ignite the seeding unit 10.
Next, the robot control panel 12 outputs an opening command for the electromagnetic valves 7a and 7c to the electromagnetic valve unit 7 to the interface panel 13, and the interface panel 13 that has received the opening command sends the electromagnetic valve unit 7 to the electromagnetic valves 7a and 7c. The electromagnetic valve unit 7 which outputs the opening signal and receives the opening signal opens the two electromagnetic valves 7a and 7c.
When the two solenoid valves 7a and 7c are opened, the seed fire unit 10 is ignited. Therefore, among the plurality of preheat holes 9b of the cutting torch 9, half of the preheat holes 9b While the gas flame is ejected, a low-pressure preheating oxygen flame is ejected from the half preheating hole 9b, and these flames are preheated (piercing) until the cut portion of the steel plate becomes red hot.
The preheating time in this case is about 10 seconds when the thickness of the steel plate is 13 mm, for example. In the case of acetylene, it took about 28 seconds.

When preheating is completed in this way, the robot control panel 12 then outputs a closing command for the electromagnetic valves 7a and 7c to the electromagnetic valve unit 7 to the interface board 13, and the interface board 13 that has received the closing command outputs to the electromagnetic valve unit 7. The electromagnetic valve unit 7 that outputs the closing signal to the electromagnetic valves 7a and 7c and receives the closing signal closes the two electromagnetic valves 7a and 7c.
At the same time, the robot control panel 12 outputs an opening command for the electromagnetic valve 7 b to the electromagnetic valve unit 7 to the interface panel 13, and the interface panel 13 receiving the opening command outputs an opening signal to the electromagnetic valve 7 b to the electromagnetic valve unit 7. The electromagnetic valve unit 7 that has received the opening signal opens one electromagnetic valve 7b.

When one solenoid valve 7b is opened, since the seed fire unit 10 is ignited, a high-pressure cutting oxygen flame is ejected from the ejection hole 9a of the cutting torch 9, and the steel plate is oxidized and oxidized. Grooves are formed by removing combustion products from the steel sheet at the cutting location of the steel sheet melted by heat by the energy of the high-pressure cutting oxygen jet.
Then, by moving the cutting torch 9 in a desired direction while continuing the combustion reaction and the combustion product elimination reaction, a continuous groove is formed along the moving path to cut the steel plate into a desired shape. It is to do.
The cutting speed in this case is, for example, 510 mm / min when the thickness of the steel sheet is 13 mm. In the case of acetylene, it is 430 mm / min.
In addition, the steel plate cut | disconnected by the gas cutting method of the steel plate which concerns on Embodiment 1 of this invention is said to be a flat steel with a thickness of 10 mm to 20 mm, and supplements the intensity | strength of an outer plate, a cutting material, and an inner construction material. Therefore, the steel plate is an elongated steel plate having a maximum length of 14 m and a width of 0.45 m or less. Cutting about 1 m from the flat steel is called flat steel cutting.

Next, when the gas cutting method of the steel sheet according to the present invention is carried out, about the verification result of the experiment to what extent it is superior to acetylene gas with respect to cutting speed, piercing time, strain amount and slag adhesion state explain.
FIG. 3 is a graph showing a comparison of cutting speeds of acetylene gas and hydrogen gas, FIG. 4 is a graph showing comparison of piercing times of cutting of acetylene gas and hydrogen gas, and FIG. 5 is a graph showing slag adhesion of cutting of acetylene gas and hydrogen gas. It is a graph which shows a comparison.
(1) Cutting speed In the experiment, for each plate thickness of the steel plate, one side is cut with acetylene gas on the same steel plate, then the other side is cut with hydrogen gas, the cutting speed is increased at a pitch of 500 mm, and cutting becomes impossible. Based on the WES2801 gas cut surface standard edition, obtain the maximum cutting speed at which WSE1 grade quality is cut for roughness, slag, flatness, melting of the upper edge, straightness of bevel accuracy, and notch It was.
As a result of setting this value as the cutting speed, in the case of the mixed gas of the present invention, the cutting speed is 28.8 m / H, whereas in the case of acetylene gas, it is 24.0 m / H, which is higher than that of acetylene gas. In the case of gas, it can be seen that the cutting speed is faster and the effect is greater as the plate thickness is thicker than other gases.
Furthermore, since the speed was about 10-15% faster, it was confirmed that the work period could be shortened by about 1.5 days in the case of two shift work (see FIG. 3).

Thus, the cutting speed of the mixed gas of the present invention is faster than that of acetylene gas. First, the combustion speed of hydrogen gas, which is mainly mixed gas, is 11 m / sec, which is higher than that of acetylene. It is very fast and takes a long time to burn out, resulting in a small thin flame compared to acetylene.
Secondly, since the hydrogen flame of the hydrogen gas in the mixed gas becomes a thin flame, energy can be transmitted to the workpiece material in small dots (pinpoints), and saying that it becomes a small point increases the energy density. This is because the concentration of thermal energy at the cutting point exceeds that of acetylene gas, which promotes the preheating effect of the workpiece material.

(2) Piercing time (preheating time)
A piercing penetration test using the mixed gas of the present invention was performed, and the time required for comparison with the acetylene gas was compared. It is verified that acetylene gas takes 45 seconds per time in the range of sheet thickness (shot material) 9mm to 22mm, which is generally used as a steel material for shipbuilding, but 10 seconds per time in mixed gas cutting. (See FIG. 4).
Since the number of times of piercing in the NC gas cutting per VLCC is 1000 times, if the piercing time is shortened from 45 seconds to 10 seconds, the work period can be shortened by about one day.
As described above, the piercing time of the mixed gas of the present invention is shorter than that of acetylene gas. First, as in the case described above, the combustion speed of hydrogen gas mainly composed of mixed gas is much lower than that of acetylene. Secondly, the concentration of thermal energy is higher in the mixed gas than in the acetylene gas.

(3) Distortion amount When cutting the cut material with acetylene gas, distortion occurs as the distortion is visually recognized at the start of cutting, but in the case of the mixed gas cutting of the present invention, only a distortion with a cutting width of about 2 mm occurred. The small amount of distortion could be verified.
Thus, the amount of distortion in the mixed gas of the present invention is smaller than that in the acetylene gas because the concentration of thermal energy is higher in the mixed gas than in the acetylene gas. This is probably because the amount of heat is small.
This can be seen from the fact that the change in cutting temperature was examined with a temperature sensor every minute, but it was found that the temperature (heat input) of the mixed gas cutting was much lower than that of the acetylene gas cutting. .

(4) Slag adhesion state Although the slag produced by the mixed gas cutting of the present invention adheres to the steel plate, about 70% is naturally dropped and removed without manual intervention (see FIG. 5).
Therefore, it is about the first grade in slag adhesion, and is a good level.
Further, it was confirmed that the remaining 30% could be removed (equivalent to WES2 grade) by tapping lightly.
(5) Running cost Combustion gas consumes oxygen according to chemical reaction at the time of combustion. Hydrogen gas in the mixed gas is characterized by complete combustion with a smaller amount of oxygen than acetylene gas.
This means that the amount of preheated oxygen necessary for cutting is smaller than that of acetylene gas, so that the consumption cost of oxygen gas can be kept low. From this point, the mixed gas of the present invention keeps the running cost lower. Can do.
Further, in terms of cutting speed and piercing time, the mixed gas has a higher cutting speed and shorter piercing time than the acetylene gas, so that the running cost can be kept low.

Furthermore, the safety | security at the time of implementing the gas cutting method of the steel plate which concerns on this invention is demonstrated.
(1) Explosive limit of combustible gas Explosion occurs when there is an ignition source and the combustible gas is within a certain concentration range with air or oxygen. Within this range, the lean limit of flammable gas concentration is called the lower limit, and the limit with higher concentration is called the upper limit.
Therefore, an explosive mixed gas is more likely to be generated when the lower limit is leaked, so that it can be said to be a highly dangerous gas.
1) Lower limit of propane gas explosion: 2.2%
2) Lower limit of acetylene gas explosion: 2.5%
3) Lower limit of hydrogen gas explosion: 4.0%
From the above, the danger from the explosive limit is
Propane gas> acetylene gas> hydrogen gas. Hydrogen is the least dangerous gas.

(2) Ignition point Since a flammable gas with a lower ignition point is more likely to explode, it can be said to be a highly dangerous gas.
1) Ignition point of propane gas: 458 ° C
2) The ignition point of acetylene gas: 305 ° C
3) Fire point of elementary gas: 574 ° C
Therefore, the danger from the ignition point is
Acetylene gas> propane gas> hydrogen gas The hydrogen gas is the least dangerous gas.

(3) Specific gravity Since a flammable gas having a small specific gravity is likely to diffuse into the air, it can be said to be a gas with low risk.
1) Specific gravity of propane gas: 1.56
2) Specific gravity of acetylene gas: 0.906
3) Specific gravity of hydrogen gas: 0.07
Hydrogen is a very light gas compared to air. For this reason, even if it leaks, it diffuses immediately and falls below the explosion limit concentration. Therefore, the danger in terms of specific gravity is propane gas> acetylene gas> hydrogen gas, and hydrogen gas is the least dangerous gas.
As described above, the mixed gas mainly composed of hydrogen gas can also be said to be a low risk gas in terms of the lower explosion limit, ignition point, and specific gravity.

Further, the influence on the environment when the steel sheet gas cutting method according to the present invention is implemented will be described.
(1) Stage dioxide (CO2)
The fuel gas reacts with oxygen during combustion to cause the following chemical reaction.
1) Hydrogen: H2 + 1 / 2O2 = H2O
2) Propane: C3H8 + 5O2 = 3CO2 + 4H2O
3) Acetylene: C2H2 + 5 / 2O2 = 2CO2 + H2O
Propane and acetylene each have a carbon atom in the composition, and when they burn, they combine with oxygen to generate carbon dioxide.
This carbon dioxide is also a gas that causes a global warming phenomenon, and has recently been called for reduction on a global scale. In addition, carbon dioxide generated during combustion causes an effect of extinguishing the flame and adversely affects the oxidation reaction of iron during cutting.
Reducing the carbon dioxide concentration in the combustion flame using hydrogen as a fuel has the advantages that the oxidation reaction of iron is promoted, the cutting speed is increased, and the cut surface is clean.
Similarly, it can be said that it is desirable to reduce the carbon dioxide concentration in the combustion flame for the mixed gas mainly composed of hydrogen gas from the influence on the environment.

(2) Improvement of working environment Carbon-based combustion gases such as acetylene and propane are harmful to the human eye because they burn when burned, producing a high-luminance flame called “carbon bright”.
On the other hand, since the hydrogen flame does not emit light (the flame cannot be seen), the brightness is lowered and the working environment is improved. It can be said that it is “friendly to the eyes”. However, since it is a colorless flame and there is a risk of burns, propane is mixed to create a faint visible flame.
(3) Nitrogen compounds Not only carbon dioxide but also nitrogen compounds are regulated as air pollutants. Nitrogen compounds are produced when nitrogen in the air reacts with oxygen during combustion.
In the case of a gas that requires a large amount of air during combustion, a large amount of nitrogen compounds are also generated. Hydrogen flames consume less theoretical oxygen. That is, since it burns out with a small amount of air, it has the property of reducing nitrogen compounds compared to acetylene gas and propane gas.
The mixed gas mainly composed of hydrogen gas also has the property of reducing nitrogen compounds compared to acetylene gas and propane gas, and has a considerable impact on the environment.

The block diagram which shows the gas cutting apparatus which enforces the gas cutting method of the steel plate which concerns on this invention. Explanatory drawing which shows the structure of the crater of the cutting torch of the cutting device. The graph which shows the comparison of the cutting speed of acetylene gas and hydrogen gas. The graph which shows the comparison of the piercing time of cutting | disconnection of acetylene gas and hydrogen gas. The graph which shows the comparison of the slag adhesion of the cutting | disconnection of acetylene gas and hydrogen gas.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Seawater electrolyzer, 2 Propane gas tank, 3 Gas mixer, 4 Mixed gas tank, 5 Oxygen tank, 6 Gas operation panel, 7 Solenoid valve unit, 7a-7d Solenoid valve, 8 Safety valve unit, 8a-8c valve, 9 cutting torch, 9a ejection hole, 9b preheating hole, 10 type fire unit, 11 ignition device, 12 cutting robot control panel, 13 interface panel, 16 mixed gas supply hose, 17a to 17b mixed gas supply branch hose, 18 oxygen Supply hose, 18a-18b Oxygen supply branch hose, 20 Manual on-off valve, 21 Pressure adjustment valve, 22 Pressure meter, 23 Manual on-off valve, 24 Pressure adjustment valve, 25 Pressure meter.

Claims (4)

  A gas mixture mainly composed of hydrogen, oxygen and propane gas added thereto, and low-pressure oxygen are ejected from a plurality of preheating holes formed in the outer periphery of the crater of the cutting torch, and the mixed gas and low-pressure oxygen are ejected. Preheat the cut part of the steel sheet with a flame formed by ignition until it is red hot, and eject high pressure oxygen from the injection hole formed in the center of the crater of the cutting torch at the cut part of the red hot steel sheet. The steel plate is oxidized by a flame formed by igniting oxygen, and the cutting portion of the steel plate melted by the oxidation heat is blown off by a jet of flame ignited by the high-pressure oxygen to cut the cutting torch in a desired direction A gas cutting method for a steel sheet, wherein the cutting is performed along the moving path of the cutting torch.    2. The steel sheet gas cutting method according to claim 1, wherein the mixed gas is a mixture of 48 to 56% hydrogen, 24 to 28% oxygen, and 20 to 24% propane gas. . A mixed gas tank that mainly stores hydrogen and stores a mixed gas obtained by adding oxygen and propane gas thereto;
An oxygen tank for storing oxygen;
A cutting torch having a high-pressure cutting oxygen injection hole formed at the center, and a plurality of preheating holes for discharging mixed gas and low-pressure preheating oxygen formed on the outer periphery;
A seeding unit for igniting cutting oxygen ejected from the ejection hole of the cutting torch or preheating oxygen ejected from the preheating hole and a mixed gas;
An ignition device for igniting the mixed gas ejected from the seeding unit;
A mixed gas supply hose connected to the mixed gas tank;
A branch hose for supplying a mixed gas that connects the hose for supplying a mixed gas and a pilot fire unit;
A mixed gas supply branch hose connecting the mixed gas supply hose and the plurality of preheating holes of the cutting torch;
An oxygen gas supply hose connected to the oxygen tank;
An oxygen supply branch hose connecting the oxygen gas supply hose and the plurality of preheating holes of the cutting torch;
An oxygen supply branch hose connecting the oxygen gas supply hose and the plurality of ejection holes of the cutting torch;
A manual on-off valve provided on the mixed gas supply hose;
A manual on-off valve provided on the oxygen supply hose;
A pressure regulating valve provided in each of two oxygen supply branch hoses;
Electromagnetic valves provided respectively for two mixed gas supply branch hoses and two oxygen supply branch hoses;
A control unit that operates the ignition device and controls to open and close these solenoid valves;
A gas cutting device for a steel sheet, comprising: Adjusting the pressure regulating valve provided in the branch hose for oxygen supply connected to the plurality of preheating holes of the cutting torch so that low-pressure oxygen flows in the branch hose for oxygen supply;
Adjusting the pressure regulating valve provided in the branch hose for oxygen supply connected to the ejection hole of the cutting torch so that high-pressure oxygen flows in the branch hose for oxygen supply;
The control unit operates the ignition device to ignite a seed igniting unit, and in a state where the cutting torch is set at a cutting portion of a steel plate, a solenoid valve provided in the mixed gas supply branch hose; The solenoid valve provided in the branch hose for oxygen supply through which low-pressure oxygen flows is opened for a predetermined time, low-pressure oxygen and mixed gas are ejected from a plurality of preheating holes of the cutting torch, and ignited by the seeding unit. A predetermined time until the end of cutting of the steel plate of the electromagnetic valve provided in the branch hose for supplying oxygen through which high-pressure oxygen flows is controlled to form a flame and close these solenoid valves after a predetermined time. 2. A steel sheet gas cutting device according to claim 1, wherein the gas cutting device is opened, high pressure oxygen is jetted from a blow hole of a cutting torch, and a flame is formed by igniting the seed fire unit.

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