JPH062955A - Stainless steel boiler - Google Patents

Abstract

PURPOSE:To protect to suppress stress corrosion cracking, pitting, a clearance corrosion of a material metal of an austenite series stainless steel material and to provide a boiler having high reliability in a stainless steel boiler for a hot water supplying apparatus and a room heater. CONSTITUTION:Metal 5 such as copper, copper alloy, aluminum, tin, zinc, etc., is interposed to be held between a processed part of a stainless steel boiler 1 welded at 6 to a stainless steel bottom 2. The metal is buried in a clearance generated at the processed part to suppress stress corrosion cracking, pitting, a clearance corrosion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel can body made of a stainless material, which is used for hot water supply equipment, heating equipment and the like.

[0002]

Boiler cans used in conventional hot-water supply equipment, heating equipment, etc. are made of austenitic stainless steel, ferritic stainless steel, or copper. In order to improve corrosion resistance, sacrificial anodes made of aluminum or magnesium and , Cathodic protection was used.

[0003]

However, with the above-mentioned structure, the boiler can for a water heater such as a water heater or a heater has a problem in corrosion resistance and the like.

This is because, in the case of austenitic stainless steel materials, stress corrosion cracking or cracking occurs due to the attack of chlorine ions or residual chlorine contained in water in the accumulated portion of residual stress during processing or thermal stress due to repetition. Pitting corrosion and crevice corrosion (crevice corrosion easily occurs in a gap of about 0.2 to 1.0 mm).

In the case of ferritic stainless steel material,
Pitting corrosion and crevice corrosion occur due to the effects of chlorine ions, residual chlorine, sulfate ions, nitrate ions and dissolved oxygen.

In the case of a copper material, pitting corrosion and general corrosion occur due to the effects of chlorine ion, sulfate ion, nitrate ion, iron ion, free carbonic acid, dissolved oxygen and the like.

The present invention solves the above-mentioned problems of the prior art, and provides a stainless steel can body for hot water supply equipment and heating equipment in which stress corrosion cracking, pitting corrosion and crevice corrosion, which are likely to occur in stainless steel materials, are suppressed. To do.

[0008]

In order to solve the above-mentioned problems, the stainless steel can of the present invention has copper, copper alloy, aluminum, aluminum alloy, zinc,
It is a stainless steel can body in which any one metal of zinc alloy, tin, and tin alloy is brought into contact.

[0009]

With the above-described structure, the present invention can suppress stress corrosion cracking, pitting corrosion and crevice corrosion of stainless steel materials.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, SUS-304, which is an austenitic stainless steel having a plate thickness of 0.5 mm, is processed into a boiler can body 1 and a boiler bottom can body 2, and then a copper plate 5 is provided around the machined peripheral portion 4. Attachment, as shown in FIG. 2, it was sandwiched and the periphery thereof was welded 6. 3 is an electric heater.

In Example 2, instead of the copper plate 5 of Example 1, a brass plate (copper: zinc ratio of about 6: 4) was sandwiched in the same manner as in FIG. 2 and the periphery thereof was welded.

In the third embodiment, instead of the copper plate 5 of the first embodiment, an aluminum plate is sandwiched in the same manner as in FIG. 2 and its periphery is welded.

Further, in Example 4, instead of the copper plate 5 of Example 1, a tin plate was sandwiched in the same manner as in FIG. 2 and the periphery thereof was welded. In the case of a tin plate, welding may partially dissolve the tin.

Further, in Example 5, instead of the copper plate 5 of Example 1, a zinc plate was sandwiched and the periphery thereof was welded as shown in FIG.

Further, in Example 6, instead of SUS-304, which is the material for the boiler can 1 and the boiler bottom can 2 of Example 1, SUS-321, which is austenitic stainless steel having a plate thickness of 0.5 mm, is used. Other than that, it is the same as that of the above-mentioned Example 1.

Further, in Example 7, in place of SUS-304, which is the material for the boiler can body 1 and the boiler bottom can body 2 of the above-mentioned Example 1, ferritic stainless steel having a plate thickness of 0.5 mm, YUS190 made by Nippon Steel Co., Ltd. Is the same as in Example 1 above.

Further, in Example 8, SUS-304, which is an austenitic stainless steel having a plate thickness of 0.5 mm, was processed into a boiler can body 1 and a boiler bottom can body 2, and then a copper wire 7 was formed on the periphery of the machining as shown in FIG. So that it is sandwiched and welded around it 6
did.

As described above, in order to compare the corrosion resistance of the processed water heater boiler can body, the boiler can body and the boiler bottom can body, which have been processed in the related art, are used for the water heater boiler (material: SUS-304). Compared with.

As a comparative test of corrosion resistance, a stress cracking test by boiling a 42% magnesium chloride solution, a pitting corrosion and a crevice corrosion test of 4% ferric chloride + 1% sodium chloride aqueous solution at 60 ° C., 100 mg copper sulfate + 100 ml sulfuric acid aqueous solution An intergranular corrosion test was carried out. The test results are shown in (Table 1).

[0021]

[Table 1]

* The occurrence time of pitting corrosion is the time when the plate penetrates due to pitting corrosion. * In the conventional grain boundary test product, a structural change (presumed to be chromium carbide precipitation) was observed in the surface layer of the plate of about 0.1 mm.

The pitting corrosion and crevice corrosion test in the examples of the present invention caused pitting corrosion at a position slightly apart from the heat-affected zone of welding.

The pitting corrosion and crevice corrosion test of the conventional products cause pitting corrosion in the crevice near the welded portion, and pitting corrosion just before penetration even at a place far from the heat affected zone of welding. Admitted.

[0025]

As described above, the can body of the present invention has the following effects. (1) Suppression of stress corrosion cracking caused by the attack of chlorine ions contained in water, residual chlorine, etc. in the accumulated portion of residual stress during processing and thermal stress due to repeated use. (2) There is no risk of crevice corrosion because no gap is created by sandwiching any one metal of copper, copper alloy, aluminum, tin and zinc in the welded portion. (3) The natural potential of the stainless steel can is changed by metals such as copper, copper alloy, aluminum, tin and zinc to improve corrosion resistance.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric heater type can body for a water heater according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the main part of the can body.

FIG. 3 is an enlarged cross-sectional view of a main part of a can according to another embodiment of the present invention.

[Explanation of symbols]

 1 Can body 2 Can body bottom part 5 Insert material 6 Welding

Claims (1)

[Claims] 1. A metal of any one of copper, copper alloy, aluminum, aluminum alloy, magnesium, magnesium alloy, zinc, zinc alloy, tin and tin alloy is brought into contact with a welded portion or a working gap portion of a stainless steel can. Made stainless steel can body.