JP4875949B2 - Gas cutting method - Google Patents

Description

  The present invention relates to a gas cutting method for an iron-based alloy using oxygen.

Conventionally, as a cutting method using a material made of an iron-based alloy as a workpiece, the workpiece is preheated with a preheating flame, and high-pressure oxygen is allowed to flow so that the workpiece is burned and the combustion heat is used. Gas cutting for cutting an object to be cut is known. As the preheating gas that forms the preheating flame, a mixture of acetylene, propane, or the like, which is a fuel gas, and oxygen at a certain ratio is used.
For example, Patent Document 1 describes a gas cutting method in which propane or acetylene or the like and oxygen gas are mixed and ignited to form a preheating flame.
Patent Document 2 discloses propane, butane, and iron making, which are saturated hydrocarbon gases extracted from acetylene, ethylene, propylene, or a mixed gas or a liquefied petroleum gas when a preheating flame is formed. It is described that coke oven gas (COG) generated in a place or the like, or gas obtained by mixing COG with blast furnace gas, converter gas, or the like may be used.
JP-A-9-19765 (2nd page) JP 7-32142 A (page 3)

However, the conventional gas cutting method as described above has the following problems.
The preheating gas used for gas cutting is appropriately selected depending on workability, safety and economy.
For example, when acetylene is used as the preheating gas, oxygen is used as a combustion gas with a mixing ratio of 1.1 to 1.2 with respect to acetylene 1. When propane is used, oxygen is used as combustion gas with respect to propane 1 at a mixing ratio of 4.0 to 4.5.
Although acetylene is light specific gravity and excellent in workability, the explosive range is as wide as 2.5 to 100 vol%, so it is necessary to perform cutting work with great care in a work environment without fire to prevent ignition and explosion. Also, since it is expensive, there is a problem that it is not a cutting method that can be easily used for simple cutting applications.
In addition, acetylene has a problem in that it has a carbon-carbon bond, so it easily generates soot during combustion, pollutes the atmosphere and working environment, and darkens the base material and crater. Therefore, there is a problem that it is necessary to clean the crater at a high frequency, and it takes time and effort for maintenance.
Propane is often used because it is easily available and has a low risk of explosion, but has a problem that oxygen consumption is higher than acetylene. In addition, the amount of soot is smaller than that of acetylene, but it is easily generated because it has a bond between carbons.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a gas cutting method that facilitates maintenance of a crater and can maintain environmental cleanliness and safety. And

In order to solve the above-mentioned problems, in the invention described in claim 1, a preheating flame is formed by a preheating gas, the workpiece is preheated by the preheating flame, and cutting oxygen is added to the preheated workpiece. A gas cutting method for cutting the workpiece by injection, wherein the preheating gas is formed by mixing dimethyl ether as a fuel gas and preheating oxygen, and the mixing ratio of the preheating oxygen to the dimethyl ether is set. 1.5 or more and 1.9 or less .
According to this invention, the object to be cut is preheated by forming a preheating flame with a preheating gas in which dimethyl ether and preheating oxygen are mixed, and the object to be cut is burned with cutting oxygen to cut the object to be cut. be able to.
Dimethyl ether has a narrower explosion range than acetylene, and is less likely to catch fire or explode, so it is easy to handle and does not contain carbon bonds. Contamination due to can be reduced.

Moreover, according to this invention, the mixing ratio of the preheating oxygen with respect to dimethyl ether becomes favorable, and efficient cutting can be performed.

  According to the gas cutting method of the present invention, the preheated gas uses dimethyl ether which can suppress the occurrence of soot during combustion and has low risk of ignition and explosion. There is an effect that safety can be kept good.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
A gas cutting method according to an embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram of a gas cutting device for performing a gas cutting method according to an embodiment of the present invention.

As shown in FIG. 1, the gas cutting device 1 includes a crater 2, a cutting oxygen supply unit 7, a preheating oxygen supply unit 8, and a DME supply unit 9. The crater 2 is disposed so as to face a workpiece 10 (object to be cut) made of an iron-based alloy so as to be relatively movable in a cutting direction (horizontal arrow direction in FIG. 1).
The crater 2 is provided with a cutting oxygen flow path 3 for supplying cutting oxygen from the cutting oxygen supply unit 7 at the center thereof, and a high-pressure cutting oxygen flow 5 from the center of the end of the crater 2 facing the workpiece 10. Can be injected.
Further, in the present embodiment, in order to supply the preheating gas that forms the preheating flame 6, the preheating gas channel 4 formed in an annular shape on a concentric circle outside the cutting oxygen channel 3 is provided.
The preheating gas is a mixed gas of preheating oxygen supplied from the preheating oxygen supply unit 8 and dimethyl ether (hereinafter abbreviated as DME) supplied from the DME supply unit 9. The oxygen mixing ratio, which is the ratio of preheating oxygen to DME, can be adjusted as needed depending on the material of the workpiece 10 and the cutting conditions, but in this embodiment, the range of the oxygen mixing ratio that allows particularly good cutting. It is adjusted to the range of 1.5 or more and 1.9 or less.
The cutting oxygen and preheating oxygen supplied by the cutting oxygen supply unit 7 and the preheating oxygen supply unit 8 may use the same oxygen, or may use oxygen having different purities, for example.

Next, the gas cutting method of this embodiment by the gas cutting apparatus 1 will be described.
By adjusting the flow rates of the preheating oxygen supply unit 8 and the DME supply unit 9, a preheating gas whose oxygen mixing ratio is adjusted to 1.5 or more and 1.9 or less is supplied to the preheating gas channel 4, and the preheating flame is ignited. 6 is formed.
Then, cutting oxygen is supplied from the cutting oxygen supply unit 7 to the cutting oxygen flow path 3, and a cutting oxygen gas flow 5 is injected from the end of the crater 2 into a region surrounded by the preheating flame 6.
The preheating flame 6 shields the periphery of the cutting oxygen airflow 5 flowing inside from the outside air so that the flow velocity of the cutting oxygen airflow 5 does not decrease or the pressure does not decrease due to air entrainment. Is heated to about 900 ° C., which is the ignition temperature of the iron-based alloy. The preheating flame 6 also functions to remove impurities such as moisture, rust, and scale on the surface of the workpiece 10 that inhibit combustion.

The iron component on the surface of the workpiece 10 that has reached the ignition temperature is burned by the cutting oxygen, and the combustion is continued by continuously supplying the cutting oxygen. On the other hand, the workpiece 10 is melted by the combustion heat at that time, and the combustion product and the molten metal are blown away by the mechanical energy of the cutting oxygen injected at a high pressure, thereby promoting the cutting.
In this state, by moving the crater 2 relative to the workpiece 10 at an appropriate speed, the workpiece 10 can be cut along the movement trajectory.

The above steps are the same as gas cutting using general acetylene, propane or the like as the fuel gas, but in this embodiment, since DME is used as the fuel gas used for the preheating gas, the following features are provided.
As can be seen from the chemical formula (CH ₃ ) ₂ O, DME has no decomposability because it does not contain carbon-carbon bonds, and carbon hardly becomes soot during combustion. On the other hand, since acetylene (C ₂ H ₂ ) and propane (C ₃ H ₈ ) both contain carbon-carbon bonds, soot is easily generated during combustion.
If wrinkles occur at the time of cutting, they not only adhere to the cut surface and make the appearance unsightly, but also the surface on which wrinkles are attached cannot be welded or the welding strength decreases. Therefore, it is necessary to remove the wrinkles adhering to the workpiece 10 after cutting, which is troublesome. Similarly, since the soot adheres to the crater 2, it is necessary to clean the soot regularly. In addition, there is a problem that when the kite is scattered in the atmosphere, the environment is polluted.

By using DME, the amount of soot adhering to the cut surface of the workpiece 10 and the crater 2 can be reduced, so that the slag adhering to the cut surface is cleaned or the crater 2 is cleaned for maintenance. Time and effort can be reduced.
Although the amount of soot varies depending on the cutting conditions, for example, when compared with the cleaning frequency of the crater 2, the cleaning frequency of propane, which generates less soot than acetylene, is further ½ times to 1 / 3 times.
In addition, since DME contains oxygen atoms in the molecule, the oxygen mixing ratio can be kept lower than that of propane that has many carbon atoms and no oxygen atoms. Therefore, oxygen consumption can be reduced.

In terms of safety during work and storage, DME is stable at room temperature, has an explosion range in air of 3.4 to 27 vol%, and an ignition point of 350 ° C. Therefore, it is unstable at room temperature, has an explosion range in the air of 2.5 to 100 vol%, and has a safety characteristic compared to the case of acetylene having an ignition point of 305 ° C., and is extremely easy to handle. .
On the other hand, compared with propane, which has an explosion range in air of 2.1 to 9.5 vol%, the explosion range is somewhat wide, but the lower limit of the explosion range is large. Lower. For this reason, it is practically superior in safety and handleability compared to propane.

Next, specific examples of the gas cutting method of the present embodiment will be described together with comparative examples using acetylene and propane as the preheating gas.
FIG. 2 is a bar graph showing experimental results obtained by measuring the maximum cutting speed by changing the thickness of the workpiece and the kind of the preheating gas in the vertical cutting process. The horizontal axis indicates the cut plate thickness (mm) of the workpiece, and the vertical axis indicates the maximum cutting speed (mm / min). FIG. 3 is a bar graph showing experimental results of measuring the minimum piercing time by changing the crater height and the kind of the preheating gas in the piercing process. The horizontal axis indicates the crater height (mm), and the vertical axis indicates the minimum piercing time (s).

FIG. 2 shows an experimental result of vertical cutting.
In this experiment example, SS41 is used as the workpiece 10, and the sample in which the thickness of the workpiece 10 is changed from 6 mm to 40 mm is changed to DME, acetylene or propane as the preheating gas, and vertical cutting is performed by gas cutting. The maximum cutting speed was measured after processing.
As the oxygen mixing ratio of each preheating gas, a mixing ratio at which the processing efficiency of each gas is good is appropriately set and used. That is, 1.6 to 1.7 for DME, 1.2 to 1.4 for acetylene, and 3.3 to 3.7 for propane.
As can be seen from FIG. 2, the cutting speed tends to decrease as the cutting thickness increases, but the maximum cutting speed of DME and propane is the same at the same thickness. In comparison between DME and acetylene, DME was equal or faster at 32 mm or less, and only 40 mm was inferior to acetylene.

Among the experimental examples, when the cutting plate thickness is 9 mm and 25 mm, the following Table 1 shows the cutting conditions and the result of quality determination of the cut surface. “C ₂ H ₂ ” and “LPG” in the table represent acetylene and propane, respectively (the same applies to Table 2 below). The “mixing ratio” in the table means the oxygen mixing ratio described above.
The quality judgment evaluation of the cut surface is based on WES 2801 of the Japan Welding Association standard.
The gas flow rate (NL / h) represents a normal gas flow rate, that is, 1013.25 hPa (1 atm) 0 ° C. converted flow rate liter / hour.

From Table 1, it can be seen that DME (Examples 1 to 6) is first grade except that the flatness is second grade in Example 6, and good quality is obtained. This was equivalent to propane (Comparative Examples 1 to 6). In addition, acetylene (Comparative Examples 7 to 12) shows that the slags of Comparative Examples 8 and 12 are of the first grade other than the second grade, and the quality is substantially the same as that of DME and propane.
Further, comparing the oxygen mixing ratio, it can be seen that DME is less than half of propane, and the oxygen consumption is remarkably small.

Next, experimental results of groove cutting will be described with reference to Table 2.
In this experimental example, SS41 was used as the workpiece 10, V45 ° groove cutting with a cutting plate thickness of 9 mm and 25 mm was performed, and the quality evaluation of the cut surface was performed based on WES 2801.

  According to Table 2, DME and propane had notches that were out of class (Examples 7 and 8, Comparative Examples 13 and 14), but the others were all grades of the same quality. Compared with acetylene, in addition to the notch class, the slag of Comparative Example 18 is also in the second class, so that DME has a better result.

FIG. 3 shows the experimental results of the piercing process.
In this experimental example, SS41 was used as the workpiece 10, the thickness of the workpiece 10 was 9 mm, the fuel gas of the preheating gas was changed to DME, acetylene, and propane, piercing processing was performed by gas cutting, and the minimum piercing time was measured. Is. Experiments were conducted for 5 mm and 10 mm as conditions for the crater height.
Here, the piercing time is the time when the workpiece 10 has a hole after the workpiece 10 starts to be heated.
As the oxygen mixing ratio of each preheating gas, a mixing ratio at which the processing efficiency of each gas is good is appropriately set and used.
As can be seen from FIG. 3, the piercing process is slightly inferior to acetylene, but DME is equivalent to propane. Therefore, it turns out that it has sufficient performance practically.

Here, the oxygen mixing ratio of the preheating gas using DME will be described based on an experimental example of piercing processing.
FIG. 4 is a graph showing experimental results of the minimum piercing time when the oxygen mixing ratio is changed in piercing processing using DME. FIG. 5 is a graph showing an experimental result of the minimum piercing time when the oxygen mixing ratio is changed in the piercing process using propane. 4 and 5, the horizontal axis represents the oxygen mixing ratio, and the vertical axis represents the minimum piercing time (s). In any case, SS9 having a thickness of 9 mm is used as the workpiece 10.

When DME is used as the fuel gas for the preheating gas, as shown by a curve 100 in FIG. 4, a graph of the minimum piercing time with respect to the oxygen mixture ratio is The result was such that the oxygen mixing ratio was about 1.5 and the minimum piercing time was about 42 seconds.
For example, when the allowable value of the piercing time is 50 seconds, the curve 100 shows that the preferable range of the oxygen mixing ratio is 1 to 2.5.
Further, when the oxygen mixing ratio is set to a range near the minimum value, for example, 1.5 to 1.9, the piercing time is 42 seconds to 43 seconds, and rapid processing can be performed.

On the other hand, when propane is used as the fuel gas for the preheating gas, as shown by a curve 110 in FIG. A substantially V-shaped curve opened upward was obtained, and the result was such that the oxygen mixing ratio was about 3 and the minimum piercing time was about 47 seconds.
Compared to FIG. 4, the change in the minimum piercing time with respect to the oxygen mixture ratio is considerably gradual, but the minimum value of the minimum piercing time is 5 seconds longer than that of DME. For example, in DME, it is 4 seconds longer than when the oxygen mixing ratio is in the range of 1.5 to 1.9.
In other words, even with the shortest processing time of propane, the processing time increases by about 12% compared to the shortest processing time of DME, and even when a practical allowable range is provided for the oxygen mixing ratio of DME, the processing time increases by about 10%.
Further, when the allowable value of the piercing time is 50 seconds, the preferable range of the oxygen mixing ratio is 2.5 to 3.5 as shown by the curve 110, which is narrower than that in the case of DME.
On the other hand, according to the result of FIG. 4, in order to set the minimum piercing time to 47 seconds or less in DME, the oxygen mixing ratio may be set to 1.2 to 2.3. Therefore, according to the preheating gas using DME, the oxygen mixing ratio can be easily set so as to shorten the processing time as compared with the case of using propane, and efficient processing can be performed.

As described above, according to the gas cutting method of the present embodiment, since DME is used as the fuel gas for the preheating gas, generation of soot at the time of combustion can be suppressed, and the maintenance of the crater becomes easy. The cleanliness can be kept good.
In addition, DME has much higher safety such as ignition and explosion than acetylene, so that it can be easily handled at the time of cutting and storage.
Further, the processing performance by this method is equal to or better than that of propane, and the oxygen consumption can be remarkably reduced as compared with propane. Therefore, it is a gas cutting method that is extremely suitable for replacing propane, which is widely used in place of acetylene, for safety and ease of handling.

  In the above description, the preheating gas channel 4 of the crater 2 is described as an annular shape on the concentric circle of the cutting oxygen channel 3, but the structure of the crater is not limited to this. . For example, a structure in which a plurality of preheating gas channels 4 are provided at appropriate pitches on the concentric circles of the cutting oxygen channel 3 may be used.

It is a typical schematic structure figure of the gas cutting device for performing the gas cutting method concerning the embodiment of the present invention. It is a bar graph which shows the experimental result which changed the plate | board thickness of the to-be-cut object, and the kind of preheating gas, and measured the maximum cutting speed in the vertical cutting process. It is a bar graph which shows the experimental result which changed the crater height and the kind of preheating gas in the piercing process, and measured the minimum piercing time. It is a graph which shows the experimental result of the minimum piercing time when changing oxygen mixing ratio in the piercing process using DME. It is a graph which shows the experimental result of the minimum piercing time when changing the oxygen mixing ratio in the piercing process using propane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas cutting device 2 Tinder 3 Cutting oxygen flow path 4 Preheating gas flow path 5 Cutting oxygen air flow 6 Preheating flame 7 Cutting oxygen supply part 8 Preheating oxygen supply part 9 DME supply part 10 Workpiece (to-be-cut object)

Claims (1)

A gas cutting method of forming a preheating flame with a preheating gas, preheating a workpiece with the preheating flame, and injecting cutting oxygen into the preheated workpiece to cut the workpiece.
The preheating gas is formed by mixing dimethyl ether as fuel gas and preheating oxygen ,
A gas cutting method , wherein a mixing ratio of the preheating oxygen to the dimethyl ether is 1.5 or more and 1.9 or less .

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