JPS5817368B2 - Kanamibana - Google Patents

Description

[Detailed Description of the Invention] Conventional infrared burners with an infrared radiation surface include ceramic burners in which a large number of circular holes are bored in a fireproof plate whose main component is aoto, and in which each hole in a wire mesh is made into a human hole. wire mesh burner,
Bunsen burners, which heat refractories to high temperatures, were used.

Ceramic burners have weak mechanical strength, take time to heat up, and have low infrared generation efficiency.

This is because the temperature around the hole is relatively high due to the poor thermal conductivity of the ceramic itself, but the temperature in the area away from the hole is low and the amount of radiation is small.

On the other hand, the method of heating refractories at high temperature using a Bunsen burner has the disadvantage that uniform red heat cannot be obtained and the amount of radiation is the lowest.

On the other hand, wire mesh burners are advantageous in terms of radiation efficiency because they use metal with excellent thermal conductivity. When used as such, there is a problem in that it is exposed to a corrosive environment such as steam, salt, soy sauce, oil, or seasonings, resulting in significant corrosion in a short period of time.

In particular, although the red-hot part and the gas supply side part have deteriorated in durability due to the difference in corrosive environment, the material traditionally used in this wire mesh burner is The same steel wire Fe
Since -Cr alloy and austenitic stainless steel have been used for the fixed frame portion, there has been the above-mentioned corrosion problem.

This problem can be solved in some ways by using very expensive corrosion-resistant materials, but this is impractical from an economic standpoint.

The present invention overcomes the drawbacks of the conventional technology and has an extremely high practical value by using a plurality of layers of heat-resistant metal materials of different steel types that are relatively economical and suitable for each corrosive environment, thereby significantly increasing corrosion resistance. The wire mesh burner is provided with the wire mesh burner removed.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

The figure shows a wire mesh burner constructed in the shape of a plate. 1 is a combustion plate constructed by overlapping a plurality of wire meshes 1' that are braided using plain weave, tatami weave, or other methods, and 2 and 3 are gas supply parts. 4 is a fixed frame that holds the combustion disk 1.

Air suction port 2. The gas mixed with air in the mixing tube 3 reaches the inside of the combustion plate 1, ejects from the wire mesh 1' and ignites at the same time, the surface temperature rises, red-hot to 800-900'C, and emits strong infrared rays. radiate.

When using a wire mesh burner for cooking utensils, etc., as mentioned above, water vapor, sulfur, carbon, soy sauce, salt, etc. are present, so
The red-hot wire mesh 1' undergoes intense high-temperature oxidation, carburization, and steam corrosion.

In addition, the gas supply side part is subjected to severe action under so-called wet conditions containing a large amount of salt, and when heat-resistant metal materials are subjected to carburizing action at high temperatures, carbides precipitate at grain boundaries, resulting in significant intergranular corrosion. Sensitivity increases and becomes unusable in a short period of time, and as mentioned above, under wet conditions, the entire surface corrodes (significant red rust occurs). Connect.

As wire mesh materials for wire mesh burners, Fe-Cr alloys and Ni-Cr alloys are generally used.
At ~600°C, 475°C embrittlement occurs, at 600-800°C precipitation of sigma phase, and at temperatures above 900°C, crystal grains become coarse (ASTM grain size number is approximately 1), etc., and embrittling acids especially at low temperatures cause grain boundaries. Corrosion susceptibility increases significantly.

The latter becomes sensitized by high-temperature heating (approximately 600° C.) and causes similar problems such as chromium carbide precipitation and embrittlement due to sigma phase precipitation depending on the steel type.

In conventional wire mesh burners, the combustion section is formed by stacking two or three layers of wire mesh material of the same steel type in order to prevent blowing out by gusts of wind or backfire and to ensure stable combustion. As it reaches the gas supply side, it is cooled by the supply gas 550
The temperature will be approximately 600°C.

Further, the temperature of the portion of the fixed frame 4 that holds the wire mesh 1' is approximately 550 to 600°C because it radiates heat.

Therefore, in a wire mesh burner, it is especially the gas supply side that is affected by corrosion, and problems such as 475°C brittleness, precipitation of sigma phase, and full-scale corrosion in the wet system due to salt that has entered between the meshes of the wire mesh occur. happen.

In the present invention, since the corrosive environment differs between the red-hot side of 600℃ or higher and the gas supply side of 6008C or lower, the combustion disk is formed by stacking a plurality of wire meshes that have excellent #f corrosion and durability in each environment. The purpose is to increase the durability of the burner.

In other words, on the red-hot side of 600°C or higher, heat-resistant alloys such as high N1-high Cr alloys, which have excellent durability against carburizing and high-temperature oxidation, are used, especially on the gas supply side of 600°C or lower. is an ASTM standard that prevents 475°C brittleness, sigma phase precipitation, and chromium carbide precipitation at grain boundaries.
It is proposed to use stable austenitic stainless steel with grain size number 7 or higher.

Using the wire mesh burner of the present invention, in repeated tests of burning for 15 minutes, extinguishing for 15 minutes, continuously burning for 8 hours, and extinguishing for 16 hours, the burner with this configuration showed almost no change with only slight discoloration even after 5000 hours had passed. It had excellent durability.

On the other hand, 2 layers. In the case of Fe-Cr heat-resistant alloy, which is the same steel type as the red-hot part, the gas supply side part such as the 3-layer part has 30
From around 0 hours, the effects of high temperature oxidation and carburization due to repeated use were observed, and when it reached 500 hours, abnormal oxidation due to salt action became so severe that it became unusable.

Table 1 shows the grain size number, mechanical properties, and corrosion resistance of austenitic stainless steel.

In Table 1, as the crystal grains become coarser and grow, the mechanical properties, corrosion resistance, occurrence of red rust, and susceptibility to intergranular corrosion decrease significantly.

This is because chromium carbide precipitates at grain boundaries due to heating, and this chromium carbide significantly lacks corrosion resistance.
Therefore, corrosion progresses along the grain boundaries, resulting in intergranular corrosion, and the Cr content in the steel, which is necessary for corrosion resistance, decreases by combining with C. This is thought to have led to a decrease in corrosion resistance, the occurrence of significant red rust, and an increase in corrosion weight loss.

As for the decline in mechanical properties, even if the AsTM grain size is around 2, the ductility will be almost gone and it will break easily.
Moreover, it has almost no resistance against twisting.

It is generally said that as the crystal grains become coarser, the impact value decreases, internal stress increases, and grain toughness decreases. This is in good agreement with the results for 7 and above.

For infrared wire mesh burners, under harsh operating environments,
It is exposed to high temperatures and undergoes frequent ON/OFF cycles.

In particular, the gas supply side is subject to severe action under wet conditions containing a large amount of salt, which affects the practicality of the wire mesh burner (a large amount of red rust can cause the mesh to become clogged or cut, etc.). As mentioned above, it is necessary to ensure sufficient corrosion resistance and durability.
From the above results, stable austenitic stainless steel with AsTM grain size number 7 or higher, which prevents brittleness, sigma phase precipitation, or chromium carbide precipitation at grain boundaries, is effective; This is also clear from the results of repeated tests using the wire mesh burner of the present invention.

In this way, the present invention has different corrosive environments on the high temperature side (red-hot part) and the low temperature side (gas supply section and fixed frame), so by using heat-resistant materials that have excellent corrosion resistance and durability in each corrosive environment, It has extremely high practical value, as it enables stable combustion and dramatically improves the durability and heat resistance of the burner.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a wire mesh burner showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA' in FIG. 1, and FIG. 3 is an enlarged sectional view of the combustion disk portion. 1... Combustion plate, 1... Wire mesh.

Claims (1)

[Claims] 1. A wire mesh burner in which a combustion disk is formed by stacking a plurality of wire meshes, and the gas supply side portion of these wire meshes is made of austenitic stainless steel with AsTM grain size number 7 or higher.