JP5593082B2 - Stainless steel with improved corrosion resistance - Google Patents

Description

  The present invention relates to a structure for improving the corrosion resistance of stainless steel.

  A silencer (muffler) is incorporated in the exhaust path of the vehicle internal combustion engine in order to reduce exhaust noise. The muffler includes an inner pipe in which an exhaust purification catalyst is incorporated and exhaust gas flows, an outer pipe that surrounds the inner pipe in the circumferential direction, and an outer circumferential surface of the inner pipe and an inner circumferential surface of the outer pipe. Sound-absorbing / heat-insulating material (see, for example, Patent Document 1). Stainless steel is mainly used as the material forming the inner tube (inner material) and outer tube (outer material), and glass wool is used as the material forming the sound absorbing and heat insulating material.

  In the inner material of the muffler, iron contained in stainless steel is diffused to the surface of the member under the influence of high-temperature exhaust, and the corrosion resistance is likely to deteriorate. In addition, when calcium chloride sprayed to melt snow and freeze on the road melts in water, water containing chlorine components scatters when the vehicle passes, and enters the inside through the drain hole of the outer material and is held by glass wool. The

  And if the state where glass wool holding water containing chlorine component continues to contact the inner material with reduced corrosion resistance, the chromium component breaks the passive film of chromium contained in the stainless steel, and the inner material has pores. Corrosion occurs and causes cracks and breaks. Such a corrosion phenomenon is called CUI (corrosion under insulation). The outer material is not directly affected by the high-temperature exhaust gas, so that corrosion hardly occurs.

  Conventionally, stainless steel containing a large amount of chromium and molybdenum having a high pitting corrosion index is used for the inner material, or a heat resistant paint is applied to the surface of the inner material to cope with the CUI.

JP 2002-195021 A

  However, there is a problem that either stainless steel containing a large amount of chromium or molybdenum or a heat-resistant paint is expensive.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to improve the corrosion resistance of stainless steel by an inexpensive and easy method.

In order to achieve the above object, an invention according to claim 1 is directed to an inner material made of stainless steel constituting a part of a muffler of an internal combustion engine, an aluminum foil that covers the inner material, and an aluminum foil that covers the inner foil. and glass wool, and a outer material covering the glass wool, between the glass wool and the inner member, the sacrificial protection effect of aluminum foil is interposed so as to cover the inner member, protecting the inner member It is characterized by doing.

The invention according to claim 2 comprises a cylindrical inner material that constitutes a part of the muffler of the internal combustion engine, is made of stainless steel, and in which exhaust gas flows, and an aluminum foil that covers the outer peripheral surface of the inner material. the glass wool surrounding the aluminum foil and glass wool surrounding the inner member circumferential direction, a tubular outer member surrounding the glass wool in the inner member circumferential direction, provided with, the inner member and the outer peripheral surface of the inner member in the circumferential direction The inner material is protected by the sacrificial anticorrosive action of the aluminum foil interposed so as to cover the outer peripheral surface of the inner material.

  According to the stainless steel corrosion resistance improving structure of the present invention, the following excellent effects can be obtained.

  (1) In the invention described in claim 1, since the inner material is protected by the sacrificial anticorrosive action of the aluminum foil interposed between the inner material and the glass wool, the corrosion resistance of the inner material can be easily improved at low cost. Can be made.

  (2) In the invention described in claim 2, the inner material is protected by the sacrificial anticorrosive action of the aluminum foil interposed between the outer peripheral surface of the cylindrical inner material and the glass wool surrounding the inner material in the circumferential direction. Therefore, the corrosion resistance of the inner material can be easily improved at a low cost.

It is a conceptual diagram which shows an example of the corrosion-resistance improvement structure of the stainless steel of this invention. It is a photograph which shows the state of the inner material after the salt spray test relevant to FIG. It is a conceptual diagram which shows the conventional structure compared with FIG. It is a photograph which shows the state of the inner material after the salt spray test relevant to FIG. It is sectional drawing of the muffler to which the corrosion resistance improvement structure of the stainless steel of this invention is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of the corrosion resistance improving structure of stainless steel according to the present invention. An inner material 1 made of stainless steel (SUS436L), an aluminum foil 2 covering the lower surface of the inner material 1, and the aluminum A glass wool layer 3 covering the lower surface of the foil 2 and an outer material 4 made of stainless steel (SUS436L) and covering the lower surface of the glass wool layer 3 are provided.

  FIG. 3 shows a conventional structure for comparison with FIG. 1, an inner material 1 made of stainless steel, a glass wool layer 3 covering the lower surface of the inner material 1, and a stainless steel and glass wool. And an outer material 4 covering the lower surface of the layer 3.

  The characteristic feature of the stainless steel corrosion resistance improving structure shown in FIG. 1 is that an aluminum foil 2 covering the inner material 1 is interposed between the inner material 1 and the glass wool layer 3.

  Hereinafter, a demonstration experiment using the test piece TP1 having the structure of FIG. 1 and the test piece TP2 having the structure of FIG. 3 will be described. In order to reproduce the state of the muffler of the actual machine, the inner material 1 is preliminarily heat treated at 500 ° C. for 6 hours, and the iron contained in the stainless steel diffuses to the surface of the inner material 1. ing.

  The test piece P1 and the test piece TP2 were subjected to an SST tester (salt spray test) for spraying 5% salt water for 120 hours. In the test piece TP1, the glass wool layer 3 holding water containing a chlorine component. When the glass wool layer 3 holding the water containing the chlorine component is kept in contact with the inner material 1 in the test piece TP2, the test results are as follows. was gotten.

  In the test piece TP1, the aluminum foil 2 mainly containing aluminum, which is a base metal having a high ionization tendency compared to iron, corrodes, so that iron, which is a noble metal having a low ionization tendency compared to the aluminum, is obtained. Since the sacrificial anticorrosive action to protect works, as shown in FIG. 2, the inner material 1 does not show remarkable red rust, and the corrosion of the inner material 1 due to the chlorine component breaking the passive film of chromium is recognized. There wasn't.

  In the test piece TP2 in which the aluminum foil 2 does not exist, as shown in FIG. 4, the iron diffused on the surface of the inner material 1 exhibits significant red rust, and the inner layer caused by the chlorine component breaking the passive film of chromium. Corrosion of material 1 was observed.

  In the test piece TP1 described above, the inner material 1 is protected by the sacrificial anticorrosive action of the aluminum foil 2 interposed between the inner material 1 and the glass wool layer 3, so that the corrosion resistance of the inner material 1 can be easily improved at low cost. be able to.

  FIG. 5 shows a muffler to which the structure for improving corrosion resistance of stainless steel according to the present invention is applied. A cylindrical inner material 5 made of stainless steel (SUS436L) through which exhaust flows, and an outer peripheral surface of the inner material 5 An aluminum foil 6 covering the inner foil 5, a glass wool layer 7 surrounding the aluminum foil 6 in the circumferential direction of the inner material 5, and a cylindrical outer made of the same material as the inner material 5 and surrounding the glass wool layer 7 in the circumferential direction of the inner material 5. Material 8 is provided.

  In this muffler, when the vehicle passes, water containing a chlorine component such as a snow melting material scatters, enters through the drain hole of the outer material 8 and is held in the glass wool layer 7, and the aluminum foil 6 contains the chlorine component. When the state where the glass wool layer 7 holding water is in contact continues, the aluminum foil 6 mainly composed of aluminum having a higher ionization tendency than iron corrodes, and iron having a lower ionization tendency than the aluminum is corroded. The sacrificial anticorrosive action to protect works and prevents corrosion of the inner material 5.

  In the above-described muffler, stainless steel containing a large amount of chromium and molybdenum and heat-resistant paint are not used, and are interposed between the outer peripheral surface of the cylindrical inner material 5 and the glass wool layer 7 surrounding the inner material 5 in the circumferential direction. Since the inner material 5 is protected by the sacrificial anticorrosive action of the aluminum foil 6, the corrosion resistance of the inner material 5 can be easily improved at low cost.

  It should be noted that the corrosion resistance improving structure of the stainless steel of the present invention is not limited to the above-described embodiment, and it is needless to say that changes can be made without departing from the gist of the present invention.

1 Inner Material 2 Aluminum Foil 3 Glass Wool Layer 4 Outer Material 5 Inner Material 6 Aluminum Foil 7 Glass Wool Layer 8 Outer Material

Claims (2)

Comprising an inner member made of stainless steel which constitutes a part of a muffler of an internal combustion engine, and an aluminum foil covering the inner member, and glass wool for covering the aluminum foil, and an outer material covering the glass wool, the,
A structure for improving the corrosion resistance of stainless steel , wherein the inner material is protected by a sacrificial anticorrosive action of an aluminum foil interposed so as to cover the inner material between the inner material and the glass wool . A cylindrical inner material that forms part of the muffler of the internal combustion engine and is made of stainless steel and in which exhaust flows, an aluminum foil that covers the outer peripheral surface of the inner material, and the aluminum foil in the inner material circumferential direction comprising a glass wool surrounding the, a tubular outer member surrounding the glass wool in the inner member circumferential direction, and
The inner material is protected by the sacrificial anticorrosive action of the aluminum foil interposed so as to cover the outer peripheral surface of the inner material between the outer peripheral surface of the inner material and the glass wool surrounding the inner material in the circumferential direction. A structure for improving the corrosion resistance of stainless steel.

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