JPS58213092A - Fuel gas for metal working - Google Patents

Abstract

PURPOSE:To provide the titled fuel gas consisting of hydrogen, acetylene and LP gas in specified proportions, which forms high temperature flame, is excellent in safety and econmy and is suitable for welding and fusion cutting operations. CONSTITUTION:The fuel gas is prepared by blending 5-60vol% hydrogen, 20- 90vol% acetylene and 5-50vol% at least one LP gas selected from among 3- 4C paraffinic and olefinic hydrocarbons. EFFECT:Self-decomposition of acetylene is controlled and there is no danger of back fire. The fuel gas shows good diffusion and does not stay in low spots, for it has a specific gravity of 0.87-0.97 and is lighter than air. It has high combustion rate and good flame concentration and makes flame control easy because of its ability to form neutral flame.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel gas suitable for economical metal processing, particularly for welding and cutting.

Acetylene has traditionally been commonly used as a fuel gas for metal processing. This acetylene has a high flame temperature,
It exhibits excellent welding and fusing performance due to its good flame concentration.

On the other hand, acetylene easily flashbacks, and its decomposition limit pressure is low at 1.4 kg/aJ (absolute pressure), but its explosion limit is 2.5-80.0% (volume %, or less) in air. There is a safety problem because it covers a wide range (similar to the same), and there is also an economical problem because it is expensive compared to other fuel gases.

For this reason, recently, regas, which is available at low cost, has come to be used as a fuel gas for metal processing in place of acetylene. However, LP gas requires about four times the amount of oxygen for combustion as acetylene, and the flame concentration is poor, making it difficult to control the flame, making it difficult to weld.
It cannot be said that it is sufficient in terms of fusing performance. Moreover, the specific gravity of LP gas (air is 1, the same applies hereafter) is <(1.4
5 to 2.01) If it leaks, it will stay in low places such as floors, so there is a problem that it can only be used in places with good ventilation.

The present inventors have conducted intensive research to solve the problems of acetylene and LP gas, and have found that when using a fuel gas containing hydrogen, acetylene, and LP gas in a specific volume ratio, the superior properties of acetylene can be found. The present invention has been completed based on the discovery that the safety defects of acetylene and LP gas can be improved while maintaining the same properties as the fuel gas, and that the fuel gas can be provided at a relatively low cost.

That is, the fuel gas for metal processing of the present invention contains 5 to 60% hydrogen.
%, preferably 10-25%, acetylene 20-90%
, preferably 40-65% and LP gas 5-50%,
It is characterized by preferably consisting of 25 to 65%.

The LP gas in the present invention has 6 to 4 carbon atoms.
One or more of these paraffinic and olefinic hydrocarbons may be used.

Specific examples thereof include propane, propane, propane, propane, n-butane, butene-1, isobutyne, 1,4-butadiene, 1,6-butadiene, and the like.

The fuel gas for metal processing of the present invention having the above-mentioned specific composition has the following excellent effects in terms of safety, economy and workability.

First of all, regarding safety, (1) Since hydrogen and LP gas are blended, the self-decomposition of acetylene is suppressed, and backfire is less likely to occur, and burnout of the fuel gas pressure regulator can be avoided. (2) ) The explosive limit of LP gas is narrow (approximately 1.86 to 11
．． 1%), the explosion limit of the entire fuel gas is also that of acetylene (
(3) The specific gravity is approximately 0.87 to 0.97, which is lighter than air, so it has good diffusivity, and LP gas It has an excellent property of not staying in low places like .

In terms of economy, since it contains inexpensive gases such as hydrogen and LP gas, the overall price can be halved.

Furthermore, in terms of workability, (1) the self-decomposition of acetylene is suppressed, making it difficult to cause backfire, and the combustion speed is almost the same as that of acetylene, so the flame is stable and difficult to blow out; (2) the combustion speed is low. It is large, has good concentration, and easily forms a neutral flame, so the flame can be easily adjusted.
It is higher at approximately 3,000°0 compared to 520°0), and can be used for overlaying and thermal spraying, which require high temperatures that are difficult to use with LP gas, and can be processed in a short time. 4) It has excellent effects such as a clean processed surface.

The above-mentioned various and practical effects in terms of safety, economy, and workability can only be obtained by keeping the composition ratios of hydrogen, acetylene, and LP gas within the specified ranges, and any one component can be achieved within the specified range. If the range is exceeded, problems will arise in safety, economy, and workability, or in any or all of them.

That is, when the hydrogen content exceeds 60%, the calorific value decreases and the flame strength becomes weak, resulting in a significant decrease in the effect on workability. Moreover, when it is less than 5%, the drawbacks due to the blending of LP gas cannot be sufficiently compensated for, and the effect is greatly reduced in this respect.

Regarding acetylene, when the proportion exceeds 90%, the effects of hydrogen and LP gas are lost, and the same safety and economical problems remain as in the case of acetylene alone.

If it is less than 20%, the flame temperature will drop and the flame strength will become weak, causing problems in workability.

Further, when the T and P gases exceed 50%, the specific gravity becomes large and the combustion speed becomes slow, resulting in a significant decrease in the effectiveness in terms of safety and workability. If it is less than 5%, it will not be possible to compensate for the decrease in calorific value due to the addition of hydrogen, and the effect will be greatly reduced in this respect.

Although it is essential that the fuel gas for metal processing of the present invention contains hydrogen, acetylene, and LP gas within the above-mentioned specific ranges, other gases such as methane, ethane, ethylene, and carbon oxide may also be contained in the fuel gas of the present invention. It may be included to the extent that the effect is not impaired.

The fuel gas for metal processing of the present invention contains hydrocarbons,
It can be obtained by decomposing LP gas with heat or high-energy radiation to obtain a mixed gas of hydrogen, acetylene and LP gas, and adjusting this to a specific ratio according to the present invention, if necessary. Alternatively, it may be prepared by blending hydrogen, acetylene and two gases in the above proportions.

Next, Examples 1 to 5 will explain the fuel gas for metal processing of the present invention by giving examples and comparative examples. Commercially available hydrogen, acetylene and LP gas (composition: 92% propane, 8% isobutane) are shown in Table 1. The fuel gases of the present invention were prepared by mixing them in the proportions (volumes) shown.

Welding/fusion tests and bending tests of welded pieces were conducted using each of the prepared fuel gases and oxygen. The results are shown in Table 1.

Welding test The time required to weld a steel plate (SS41) with a thickness of '5' over a length of 25 cm and the degree of difficulty were investigated. In addition, the welding rod is GE35 (test piece: SR55kp/am2) specified in J Engineering 5Z3201.
(7) No. 1 was used.

Fusing test A steel plate (SS41) with a thickness of 25 mm was cut at a speed of 500 m.
The cut surface was melt-cut at mA+''n, and the flatness, roughness, straightness, and drag of the cut surface were examined.

J
A mold bending test of the welded joint was conducted in accordance with Engineering S.Z.6122, and the surface protrusion was investigated.

Comparative Examples 1 to 3 Using acetylene alone, LP gas alone, and comparative fuel gas prepared in the same manner as in Example 1 and having the composition shown in Table 1, welding/fusing tests and molding were carried out in the same manner as in Example 1. A bending test was conducted.

In the fusing test in Comparative Example 2, the flame strength was insufficient under the same conditions as in the example, and good cutting was achieved only when the cutting speed was increased to 300 mm/min and the gas flow rate was increased by 50%.

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Claims (1)

[Claims] 1 Hydrogen 5-60%, acetylene 20-90% by volume
% and 5 to 50% LP gas.