JP2914736B2 - Heat resistant stainless steel foil for combustion exhaust gas purification catalyst carrier with heat fatigue resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-resistant stainless steel foil used as a catalyst carrier for a combustion exhaust gas purification device. More specifically, it is not only excellent in oxidation resistance and manufacturability, but also excellent in strength at high temperature, so it is related to heat-resistant stainless steel foil which has a large effect of improving the structural durability when used for a honeycomb body of a catalyst. .

[Conventional technology]

Conventionally, ceramic honeycombs have been used in combustion exhaust gas purification devices for automobiles and the like.However, by replacing these with heat-resistant stainless steel, it is possible to reduce the thickness of the honeycomb wall and reduce the ventilation resistance and heat capacity. Since the reduction can improve the engine performance and save expensive catalyst precious metals, for example, JP-A-50-92286, JP-A-51-48473,
As disclosed in JP-A-57-71898 and JP-A-57-71898, a technique has been proposed in which this honeycomb body is made of a Fe-Cr-Al-based heat-resistant metal foil. In this case, oxidation resistance and film adhesion are attracting attention as properties required for the alloy. Therefore, since the material is generally excellent in oxidation resistance and film adhesion, a heating wire and a heating wire have been conventionally used. Based on Fe-Cr-Al-based alloy, which has been widely used as a high-temperature member for heating appliances, its oxidation resistance or adhesion to the active alumina (γ-Al ₂ O ₃ ) coat layer, which is a direct carrier for the catalyst Is used. Each of the techniques disclosed in the above publications uses Y as a means for improving the oxidation resistance of the material.

On the other hand, JP-A-58-177437 discloses a Fe-Cr-Al-based alloy mainly containing 0.002 to 0.0
Containing 5% by weight of rare earth elements of the group consisting of La, Ce, Pr, Nd;
Alloys with rare earth elements added up to a total amount of 0.06% by weight, and Zr for stabilizing the alloys, and Nb for securing creep strength at high temperatures, respectively, within a specific relationship with the C and N contents. Added alloys have been proposed. According to these publications, in an alloy in which the total of the rare earth elements exceeds 0.06% by weight, not only the oxidation resistance is hardly improved as compared with the case where the total is less than 0.06% by weight, but it is impossible to work at a normal hot working temperature. There is.

Japanese Patent Application Laid-Open No. 63-45351 discloses that the addition of Y is also expensive in an alloy based on the Fe-Cr-Al system, so that only Ln or La excluding Ce is added in an amount of 0.05 to 0.2% by weight. It is proposed to add in the range. This is because the presence of Ce is the cause of the decrease in hot workability due to the addition of Ln, and Ce also has the effect of reducing the oxidation resistance.Therefore, if Ln excluding only Ce is added, He states that it is based on the finding that hot working becomes possible and oxidation resistance is also improved. However, Ln is a chemically active element, and the separation of individual elements is not easy due to similar chemical properties of each other. Would be very expensive. Similarly, separation and removal of Ce alone cannot avoid a rise in price. Further, Japanese Patent Application Laid-Open No. 63-42356 by the same applicant discloses Ce, La, Pr as a Fe-Cr-Al-based alloy having excellent oxidation resistance and oxidation scale peeling resistance.
An alloy containing 0.01% or more and 0.30% or less of Nd in total is disclosed, but no study has been made on the hot workability of this alloy.

In addition, although these prior arts have been mainly studied on the adhesion and oxidation resistance of an oxide film, they are practically important required characteristics as a foil constituting a honeycomb body of a catalyst.
The effect of the foil material on the structural durability of the honeycomb body has not been sufficiently studied.

[Problems to be solved by the invention]

However, for example, in the case of a catalyst carrier for an automobile, the life of the catalyst carrier rarely reaches its life due to insufficient oxidation resistance of the foil in a normal use environment. In most cases, it is damaged by the thermal fatigue due to the repetition of the above and the life is reached. That is, at the time of heating, the honeycomb body is rapidly heated from the inside by the high-temperature and high-speed exhaust gas flow, and is forcibly cooled from the outside by the traveling wind. Distortion occurs. This thermal strain is not uniformly distributed in the radial direction of the honeycomb body but is concentrated several layers inside from the outermost periphery. This is due to the fact that the temperature gradient in the honeycomb body radial direction is greatly different between the outer layer side and the inner layer side, and that the rate of change of the proof strength of the foil material with respect to the temperature is greatly different depending on the temperature range. This is because the temperature range in which the proof stress of the ferritic stainless steel foil constituting remarkably decreases and the temperature range in which the temperature gradient is most steeply generated in the radial direction of the honeycomb body coincide with several layers from the outermost periphery. In addition, even when the vehicle is traveling at a constant speed, the degree of occurrence of thermal distortion is reduced due to cooling by traveling wind from the outer periphery, but the state where thermal distortion is still concentrated on several layers from the outermost periphery continues. Furthermore, when decelerating or idling, relatively low-temperature gas flows, so that the honeycomb body is cooled from the outside as well as from the inside, and the portion inside the outermost layer several layers inside has the highest temperature. Distortion concentrates.

That is, in many cases, the honeycomb body of the catalyst carrier reaches the structural life such as crushing of the cell or extreme deformation of the carrier due to accumulation of thermal strain generated inside the honeycomb body due to repeated heating and cooling. . In such a case, the strength at high temperature of the foil is important, and especially, as described above, the temperature region that matches the steep temperature gradient generation portion in the honeycomb body, that is, 600 to 850 according to the measurement by the present inventors.
The fact that the yield strength of the foil material in the temperature range of ℃ is as high as possible and the degree of decrease in the proof stress caused by the temperature above 600 ℃ is as small as possible is effective to improve the structural life of the honeycomb body. Clearly came.

Furthermore, for example, in general use such as automobiles, it is desirable to be cheap and stable in the first place. Therefore, not only the material cost is low, but also a large amount of conventional stainless steel is used. It is important to be able to manufacture relatively easily in the production process and to keep the production cost low.

In addition, since the foil is exposed to high-temperature exhaust gas, which is a true foil having an extremely large surface area with respect to the volume, the foil must naturally have excellent oxidation resistance.

The present inventors have conducted various studies to develop a constituent foil of a catalyst carrier having all of the above-described characteristics in view of such current problems, and have reached the present invention.

[Means for solving the problem]

That is, first, to improve the oxidation resistance of the foil,
It has been found that the addition of Y exceeding 0.01% is effective, and that the oxidation resistance is dramatically improved as compared with the case of Ln (Ce, La, Pr, and Nd).

Further, as described above, in order to improve the structural durability of the catalyst carrier due to heating and cooling, the foil constituting the honeycomb body is used.
It is necessary to improve the proof stress at 600 to 850 ° C. From this purpose, various investigations have shown that the addition of Nd and / or Ta or Mo
And / or W is effective. Of these, in particular, the addition of Ta is effective. In addition, when Mo and / or W is added simultaneously with the addition of Ta and / or Nd, particularly 800 ° C. or more It has been found that the proof stress on the high temperature side is further improved.

Furthermore, as a result of investigating the toughness of the hot-rolled sheet, which is a problem in the production of this type of ferritic stainless steel, it is possible to significantly improve the toughness by adding Ta or Nb. It has been clarified that the properties can be raised to a level that allows sufficient mass production in the manufacturing process.

In these various studies, the effects of Ti, Zr and V were also investigated, but it was found that Ti hardly increased the proof stress at high temperatures and that excessive addition reduced the toughness of the hot-rolled sheet. Although Zr increases the high-temperature proof stress once with a relatively small amount of addition,
It has been found that the oxidation resistance of the foil is significantly reduced and the toughness of the hot rolled sheet is also impaired. Further, it was revealed that V had neither the effect of improving the proof stress at high temperature nor the effect of improving the toughness of the hot-rolled sheet.

That is, the present invention is based on the above study results,
Naturally, even in high-temperature exhaust gas, the oxidation resistance of the foil and the adhesion of the film are excellent, and this is further improved, and it has the effect of improving the structural durability of the catalyst carrier,
In addition, the present invention has been achieved for the purpose of providing an inexpensive heat-resistant stainless steel foil having excellent workability such as hot workability and toughness of a hot-rolled sheet.

The specific means are as follows.

By weight% Y: more than 0.01% and 0.5% or less Al: 4.5% or more and 6.5% or less Cr: 13% or more and 25% or less C: 0.025% or less N: 0.02% or less C + N: 0.03% or less and Mo: 1% or more A heat-resistant stainless steel for a combustion exhaust gas purifying catalyst carrier, characterized by containing at least one of 4% or less or W: 1% or more and 4% or less within a range of Mo + W: 4% or less, and the balance being Fe and unavoidable impurities. It is a foil, or Y: over 0.01% and 0.5% or less by weight. Al: 4.4% or more and 6.5% or less. Cr: 13% or more and 25% or less. C: 0.025% or less. N: 0.02% or less. C + N: 0.03% or less. , Ta: (181 · C% / 12 + 181 · N% / 14) × 1.5 or more and 3% or less, or Nb: (93 · C% / 12 + 93 · N% / 14) × 0.8 or more and 3% or less, Ta + Nb : A heat-resistant stainless steel foil for a catalyst for purifying a combustion exhaust gas, which is contained in a range of not more than 3% and the balance is Fe and inevitable impurities. And if necessary, Mo: 4% or less or W: 4% by weight.
%, The proof stress especially on the high temperature side can be further improved.

[Action]

Next, the reasons for limiting the components in the present invention and the effects thereof will be described in detail. All chemical compositions in this specification are% by weight.

(1) Y: Y has an effect of improving the resistance of the foil against abnormal oxidation, and the life until the occurrence of abnormal oxidation of the foil is remarkably improved when Y exceeds 0.01%, as compared with the case where Y is less than 0.01%. 0.
When it exceeds 5%, it starts to decrease again. Therefore, the range is limited to more than 0.01% and 0.5% or less.

(2) Al: Al is a basic element for ensuring oxidation resistance in the present invention. If the content is less than 4.5%, in the case of foil, the protection of the oxide film in the exhaust gas is poor, and abnormal oxidation is easily caused. To occur,
Does not withstand its use as a catalyst carrier. On the other hand, if the content exceeds 6.5%, the toughness of the hot-rolled sheet is extremely reduced and the productivity is impaired, and the thermal expansion coefficient of the foil increases. The thermal fatigue due to the repetition of is increased. Therefore, in the present invention, the range of Al is 4.5% or more and 6.5% or less.

(3) Cr: Cr is a basic element for ensuring the corrosion resistance of stainless steel. In the present invention, the oxidation resistance mainly consists of the Al203 film. However, if Cr is insufficient, the adhesion and the protection are reduced. On the other hand, if the Cr content is excessive, the toughness of the hot-rolled sheet decreases, so the range is 13% or more and 25% or less.

(4) Ta: In the present invention, Ta improves the proof stress of the foil at high temperatures,
It is an important additive element for improving the structural durability of the catalyst support. The effect of Ta combines with C and N in steel to form carbonitrides, which, in addition to exerting a so-called precipitation strengthening effect, further surplus solid solution in the base material to exert a solid solution strengthening effect. Thus, the proof stress at high temperatures is improved.
At this time, the precipitation strengthening effect has a large effect, but for example, during long-time use in a temperature range exceeding 750 ℃, precipitates gradually become agglomerated and coarse, resulting in a change in the metal structure and the effect is reduced May be. On the other hand, the solid solution strengthening effect is not as effective as the precipitation strengthening effect, but there is almost no decrease in the above-mentioned effect caused by a change in the metal structure even during long-time use. Therefore, even if the precipitation strengthening action is lost due to the phenomenon described above, Ta needs to be added in a slightly excessive amount with respect to the amounts of C and N in order to maintain the solid solution strengthening action. From the above point of view, the present inventors have studied (181 · C
% / 12 + 181 · N% / 14) × 1.5 or more must be added.

However, when the amount of Ta becomes excessively large, the Laves phase precipitates, the steel ingot after casting becomes easily cracked, and the proof stress at high temperatures starts to decrease. In the range of the amounts of C and N of the present invention, the amount is 3
%. Under such circumstances, the range of addition of Ta is as follows.

Ta: (181 · C% / 12 + 181 · N% / 14) × 1.5 or more and 3% or less Further, Ta has an effect of improving the toughness of the hot-rolled sheet because it fixes C and N, but it is not limited to the above addition range. The effect of cigarettes can be fully achieved.

(5) Nb: In the present invention, Nb, like Ta, is an important additive element for improving the proof stress of the foil at high temperatures and improving the structural durability of the catalyst carrier. The action of Nb improves the high-temperature proof stress by both the precipitation strengthening action and the solid solution strengthening action for the same reason as Ta. In this case as well, as in the case of Ta, the addition range is limited in terms of the quantitative relationship with C and N, and it is necessary to add at least (93 · C% / 12 + 93 · N% / 14) × 0.8 or more. is there.

On the other hand, Nb, like Ta, is
An s phase is formed, causing the same adverse effects as in the case of Ta. Therefore, the upper limit value is limited from this point, and is 3% or less according to the study of the present inventors. Under such circumstances, the addition range of Nb is as follows.

Nb: (93 · C% / 12 + 93 · N% / 14) × 0.8 or more and 3% or less Further, Nb has an effect of greatly improving the toughness of a hot-rolled sheet, but this effect is sufficient if it is in the above addition range. It is brought. In the case of Ta + Nb, the upper limit is set to 3% for the same reason.

(6) Mo, W: In the present invention, Mo and W are important additional elements for improving the proof stress particularly at high temperatures and improving the structural durability of the catalyst carrier. The function of Mo and W is to improve the high temperature proof stress by forming a solid solution in the base material in the steel and strengthening the solid solution. At that time, Mo and W do not form a harmful precipitation phase to a considerable extent and form a solid solution, and a great strengthening action is obtained. Further, even when heating at a high temperature for a long time, there is almost no change in the metal structure, so that there is almost no change over time in the strengthening action.

On the other hand, as described above, in the present invention, the proof stress at high temperatures can be improved by adding an appropriate amount of Ta and / or Nb. In some cases, the content may gradually decrease, and excessive addition decreases the high-temperature yield strength. However, Mo and / or W do not dissolve in the presence of Ta and / or Nb, and, in addition, do not form a harmful precipitate phase in a considerable amount, and A large solid solution strengthening effect is obtained. That is,
By adding Mo and / or W to the alloy whose high-temperature strength has been improved by adding Ta and / or Nb, it is possible to further improve the proof stress at high temperatures.

From these viewpoints, the addition amount of Mo and / or W is determined. According to the study results of the present inventors, (1) when Nb and / or Ta is not added, in order to obtain a sufficient solid solution strengthening action, Mo must be added in an amount of 1% or more.
In the case of, the lower limit is also 1%, and (2) Nb and / or
When Ta is added, it is necessary to obtain sufficient solid solution strengthening action.
There is no lower limit for Mo and / or W addition.

On the other hand, since most of Mo and W are dissolved in solid form, the metal base is strengthened as the added amount increases. However, when added in excess, the toughness decreases. Therefore, the addition amounts of Mo and W are restricted from this point, and the upper limit values are both 4%. The same effect can be obtained by simultaneously adding Mo and W at the same time.
% Is desirable.

(7) C, N: Both C and N significantly reduce the toughness of the hot-rolled sheet in the present invention. This adverse effect can be suppressed by the action of Ta or Nb, but when C exceeds 0.025%, when N exceeds 0.02%, or when the total amount of C + N is 0.1%.
If it exceeds 03%, it will be difficult to restore toughness. Therefore, from this point, C: 0.025% or less, N: 0.02% or less, and C + N: 0.03% or less fall within the range.

In addition, C and N precipitate as carbonitrides, which also have the desired effect of improving the high-temperature yield strength by the precipitation strengthening effect. However, as described above, this effect is obtained when the precipitates are coarsened. Decrease. When a large amount of C and N is contained, even if Ta and / or Nb is added to the above lower limit or more, the coarsening of the precipitate is promoted and the reduction rate of the strengthening effect is increased. That is, when a large amount of C and N is contained, the average particle size of the carbonitride becomes large, and it is difficult to obtain a uniform and fine precipitation form effective for precipitation strengthening. From this point, the contents of C and N are limited, and in the present invention, C: 0.025% or less, N: 0.0
2% or less and C + N: about 0.03% or less.

 Due to the above circumstances, the range of C and N is eventually C: 0.025% or less, N: 0.02% or less, and C + N: 0.03% or less.

(8) Other impurities: Mn: In the present invention, Mn is particularly concentrated in the oxide film at the very early stage, adversely affects the formation of the subsequent Al ₂ O ₃ film, and leaves structural defects in the film. Because it contributes, it is desirable to limit it to 0.3% or less.

Si: Si is an element that improves the oxidation resistance and greatly reduces the toughness of the hot-rolled sheet. Since a high Al ferritic stainless steel as in the present invention is inherently excellent in oxidation resistance, it is desirable to suppress Si in a small amount from the viewpoint of toughness, and the upper limit is 0.5%.

P: Since P has the effect of reducing the toughness of ferritic stainless steel, Fe-Cr is inherently inferior in toughness.
In this respect, the addition amount of the -Al stainless steel is limited, and in the present invention, the addition amount is 0.1%. Further, addition of P in such a range does not adversely affect oxidation resistance.

S: S reduces the oxidation resistance, so in the present invention, S is 0.1%.
It is desirable to keep it below 003%.

The Fe-Cr-Al-based alloy of the present invention having such a configuration is subjected to the same melting, hot rolling, and cold rolling processes as in the ordinary mass production process of a normal ferritic stainless steel, and an appropriate annealing process if necessary. By combining them, a foil up to about 50 μm can be manufactured. In addition, the foil produced in this manner, and the exhaust gas purifying catalyst carrier and the catalyst device constituted by using this foil not only have a remarkably high resistance to the occurrence of abnormal oxidation even in a high-temperature combustion exhaust gas atmosphere, but also have a high temperature at a high temperature of the foil. Because of its high proof stress, the honeycomb body has high resistance to thermal fatigue, and has excellent structural durability even under conditions of repeated heating and cooling.

〔Example〕

Next, the effects of the present invention will be described in more detail with reference to examples.

Example 1 Table 1 shows the chemical components of the alloys of Examples of the present invention and Comparative Examples. Each of these steels was melted in a vacuum high-frequency induction furnace in an amount of 25 kg and cast into ingots.
Immediately after the time was fixed, hot rolling was started, and after rolling to a thickness of 4 mm, the material was naturally cooled.

At this time, occurrence of cracks during rolling was observed in B10, and when finished slabs were observed in B6 and B8, edge cracks and surface cracks were observed, although they were relatively minor. With respect to other steels, there is no particular problem in the hot rolling in Examples and Comparative Examples. These results are shown in Table 2 in the column of hot rollability in which hot-rolled sheets cracked are indicated by x, and those which did not cause any problem are indicated by o.

Next, the toughness of these hot rolled sheets was examined. Evaluation of toughness is based on a sub-size (thickness: 2.5 mm) V
A notch Charpy test piece was sampled in parallel with the rolling direction and subjected to an impact test, and evaluated at a temperature at which the average value of three points of impact absorption energy at one test temperature exceeded 3 kgm / cm ² (vT ₂ : ° C). Table 2 shows the results of these hot-rolled sheet investigations in the column of hot-rolled sheet toughness. Here, those having a vT ₂ of less than 100 ° C. are indicated by a circle, and those having a vT ₂ of 100 ° C. or more are indicated by a cross. In addition, ○
The mark indicates that mass production is possible in the normal stainless steel plate factory production process, while the mark indicates that the manufacturing cost is substantially increased even if production is difficult or possible. Is what causes. All of the alloys of the examples have good manufacturability.

Furthermore, after annealing these hot rolled sheets at 1200 ° C for 15 minutes,
Tensile test pieces having a thickness of 3 mm, a width of 30 mm and a length of 100 mm were processed and subjected to tensile tests in the temperature ranges of 600 ° C, 700 ° C and 800 ° C. The results are shown in Table 2 in the column of tensile test. The criteria for achieving high-temperature strength were as follows. That is, 60
0 Strength at ° C. is the yield strength at a and 700 ℃ 20kgf / mm ² or more 11k
Those having a gf / mm ² or more and a proof stress at 800 ° C. of 4.5 kgf / mm ² were indicated by a circle, and the others were indicated by a cross. The proof stress was an average of three experimental values. All the alloys of the examples show good high-temperature yield strength.

About A5-8 among Examples, and B5-10 among Comparative Examples,
In order to investigate whether the strength has decreased over time during long-term use at high temperature, that is, the stability at high temperature, the plate-shaped tensile test prepared in the same manner as above was held at 850 ° C for 1000 hours and then subjected to a tensile test. did. Table 3 summarizes the obtained results. The criteria for achieving the high temperature proof stress are the same as described above. It can be seen that the alloys of A5 to A8, which have been strengthened at a high temperature by the addition of Mo and / or W, have excellent high-temperature structural stability.

Examples and Comparative Examples B1-5, B7 and B9 have good toughness, and after hot rolling, repeated descaling, cold rolling (some alloys were warm-rolled), and annealing were repeated to obtain a sheet thickness of about 50 μm. Of foil. Since Comparative Examples B6, B8 and B10 had poor toughness, they were carefully rolled during the above steps in the warm state.

Test pieces having a size of 50 μm, a width of 20 μm, and a length of 25 mm were collected from these foil materials, and subjected to an oxidation test at 1150 ° C. in the atmosphere. At this time, a test of heating at this temperature for 25 hours and then allowing it to cool was performed until abnormal oxidation occurred in each foil material. These results are shown in Table 2 in the column of abnormal oxidation life. A foil material having an abnormal oxidation life of 200 hours or more is indicated by a circle, and a foil material having an abnormal oxidation life of less than 200 hours is indicated by a cross. Each steel foil of this example has a long life of 200 hours or more.

Example 2 In Table 1, a total of five kinds of foils having a thickness of 50 μm, A3, A6 and A23 as examples of the present invention and B1 and B5 as comparative examples, were prepared.
A 97mm steel strip, which was additionally processed in a sine wave shape with a period of 3.5mm and an amplitude of 3.2mm (corrugated sheet), was superimposed on this unprocessed foil (flat plate) band, and was rolled into an apparent diameter of 42mm.
A honeycomb cylindrical body having a length of about 97 mm and having a commercially available Ni-based brazing material powder adhered to the corrugated / plate joint is heated in a vacuum of about 3 × 10 ^-4 Torr. And brazed.

The thus-obtained honeycomb structure after brazing was installed in a horizontal furnace heating furnace having an inner diameter of a furnace core tube of 45 mm, and an engine exhaust gas was introduced from one end of the furnace core tube at a flow rate of 1100 l / min while introducing 100 l / min.
The operation of heating to 25 ° C. and taking out every 25 hours and visually inspecting the occurrence of troubles such as cell deformation and foil breakage of the honeycomb body was repeated eight times (corresponding to 200 hours).

At this time, engine exhaust gas was generated in a 4-cylinder gasoline engine with a displacement of 2000 cc at an air-fuel ratio of 13 under an operating condition of a rotation speed of 1500 rpm and a load of 5 kg · m at an air-fuel ratio of 13 and introduced into a heating furnace through a conduit kept at 150 ° C. Table 4 shows the obtained results. After the test, a honeycomb body in which abnormal oxidation did not occur is indicated by a circle, and a honeycomb body in which the above oxidation occurred is indicated by a cross. Further, those having no defect on the honeycomb structure after the test are indicated by a circle, and those having a defect are indicated by a cross. Abnormal oxidation and failure of the honeycomb body did not occur in the honeycomb body of the embodiment. Therefore, it can be seen that all the honeycomb bodies of the examples are excellent not only in resistance to occurrence of abnormal oxidation but also in structural durability.

Example 3 A 100 kg foil of the components shown in Table 5 was melted and cast in a vacuum high-frequency furnace, heated to 1200 ° C., rolled 30% while hot, air-cooled, and further hot-rolled at 1150 ° C. A hot-rolled sheet having a thickness of 2.5 mm was obtained.

Furthermore, this is shot blasting, pickling, cold rolling,
Annealing, degreasing, pickling, foil rolling, degreasing, slitting, foil rolling,
A foil coil having a thickness of 50 μm and a width of 97 mm was produced by the procedure of vacuum annealing.

This foil was treated with a diameter of about 10 by the same method as described above.
A cylindrical honeycomb of 0 mm and length of 97 mm is mounted on a ferrite stainless steel cylindrical outer cylinder with an inner diameter of 100 mm, length of 97 mm and a thickness of 1.5 mm, and brazing is performed between the foils and between the foil and the outer cylinder. This was used as a honeycomb catalyst carrier. Next, the engine was mounted on the exhaust gas path of the engine and subjected to an engine bench test. In the engine test, the temperature of the catalyst carrier was set to 100 ° C. or less by stopping the engine and forcibly cooling it after operating the engine for 9 minutes with the gas temperature on the catalyst carrier side at 900 ° C. The heating / cooling cycle of cooling until the temperature became was repeated 1000 times. Table 6 shows the obtained results. After the test, the cells on the gas-filled end face of the honeycomb body which did not have any troubles such as crushing of the cell, the breakage of the foil, and the displacement of the end faces in the gas flow direction were indicated by ○, and those having troubles were indicated by ×. Shown by a mark. In the honeycomb body of the example, slight cell deformation occurred, but other severe damage did not occur, whereas in the comparative example, the cell was crushed, the foil was broken, and a part of the end face in the gas flow direction was used. Had serious damage such as jumping out. Therefore, it can be seen that all the honeycomb bodies of the foil materials of the examples have excellent structural durability.

[Effects of the Invention] As is clear from the examples, the Fe-Cr-
Al-based alloys have good workability in hot work and toughness of hot-rolled sheet and are excellent in manufacturability of foils, etc., so that manufacturing costs can be kept lower and oxidation resistance is excellent. In addition to being excellent in resistance to abnormal oxidation, it has excellent resistance to high temperatures, and thus has excellent thermal fatigue resistance.Furthermore, the honeycomb structure obtained by brazing alloy foil is resistant to oxidation resistance and shape change in exhaust gas. Excellent structural durability.

Therefore, the Fe-Cr-Al-based alloy of the present invention is suitable as a foil for purifying exhaust gas, and is particularly suitable as a catalyst support for an exhaust gas purifying apparatus for an automobile.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mikio Yamanaka 5-10-1 Fuchinobe, Sagamihara-shi, Kanagawa Prefecture New Nippon Steel Corporation 2nd Technical Research Institute (72) Inventor Tomio Sadaken 3434 Shimada, Oaza, Hikari-shi, Yamaguchi Prefecture No. Nippon Steel Corporation Hikari Works (72) Inventor Hidehiko Sumitomo 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Nippon Steel Corporation Hikari Works (56) References JP-A-63-266044 (JP, A) JP-A-1-159384 (JP, A) JP-A-3-166337 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00-38/60

Claims (3)

(57) [Claims] (1) In weight%, Y: more than 0.01% and 0.5% or less Al: 4.5% or more and 6.5% or less Cr: 13% or more and 25% or less C: 0.025% or less N: 0.02 or less C + N: 0.03% or less Ta: (181 · C% / 12 + 181 · N% / 14) × 1.5 or more and 3% or less Nb: (93 · C% / 12 + 93 · N% / 14) × 0.8 or more and 3% or less Ta + Nb: 3 %, And the balance consists of Fe and inevitable impurities. 2. In% by weight, Y: more than 0.01% and 0.5% or less Al: 4.5% or more and 6.5% or less Cr: 13% or more and 25% or less C: 0.025% or less N: 0.02 or less C + N: 0.03% or less Mo: 1% or more and 4% or less or W: 1% or more and 4% or less, Mo + W: 4% or less, and the balance is composed of Fe and inevitable impurities. Heat resistant stainless steel foil for catalyst carrier. (3) Mo + W: 4% by weight at least one of Mo: 4% or less or W: 4% or less.
The heat-resistant stainless steel foil for a combustion exhaust gas purifying catalyst carrier according to claim 1, which is contained in the following range.