JPH04128344A - Heat resisting stainless steel foil used for catalyst support for combustion exhaust gas cleaning and having thermal fatigue resistance - Google Patents

Abstract

PURPOSE:To improve yield strength on the high temp. side and also to improve toughness after hot rolling by adding specific amounts of Ta and Nb together with Y in a heat resisting stainless steel foil used for catalyst support for combustion exhaust gas cleaning and consisting of an Fe-Cr-Al alloy having a specific composition. CONSTITUTION:This stainless steel foil has a composition which consists of, by weight, >0.01-0.5% Y, 4.5-6.5% Al, 13-25% Cr, <=0.025% C, <=0.02% N, (181.C%/12+181.N%/14)X1.5 to 3% of Ta and/or (93.C%/12+93.N%/14)x0.8 to 3% of Nb, and the balance iron and in which C+N<=0.03% and Ta+Nb<=3% are satisfied. Because Y content is regulated to the above value in order to improve oxidation resistance and also yield strength on the high temp. side can be controlled by the addition of Ta and Nb, the foil having high durability can be obtained. Further, because the toughness of a hot rolled plate can be remarkably improved by the addition of Ta and Nb, this foil can be mass-produced by the ordinary stainless steel producing process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 relates to heat-resistant stainless steel foil, which not only has excellent oxidation resistance and manufacturability, but also has excellent strength at high temperatures, so when used in the honeycomb body of the catalyst, it has a great effect on improving the structural durability of the honeycomb body. .

[Conventional technology]

Ceramic honeycombs have traditionally been used in combustion exhaust gas purification devices for automobiles, etc., but by replacing them with heat-resistant stainless steel, it is possible to reduce the thickness of the honeycomb walls, reducing ventilation resistance and heat capacity. Since engine performance can be improved and expensive catalyst precious metals can be saved by reducing the amount of
As disclosed in the publications No. 8473 and No. 57-71898, this honeycomb body is made of Fe-Cr.
- A technique has been proposed in which the foil is made of an Al-based heat-resistant metal foil.

In this case, oxidation resistance and film adhesion are attracting attention as properties required of the alloy. Based on the Fe-Cr-Aj2 alloy, which has been widely used as a high-temperature component in heating appliances, we have improved its oxidation resistance and its adhesion to the activated alumina (T-A I2.03) coating layer, which is a direct support for the catalyst. Foil with improved properties is used. All of the techniques disclosed in the above-mentioned publications utilize Y as a means to improve the oxidation resistance of the material.

On the other hand, in JP-A-58-177437, Fe-C
0.002 to 0.05% by weight of La, Ce, mainly to prevent peeling of the oxide film of the r-/l alloy.
An alloy containing a rare earth element of the group consisting of Pr, Nd, to which a total amount of up to 0.06 wt. An alloy has been proposed in which Nb is added within specific relationship ranges with the amounts of C and N, respectively. These publications state that alloys in which the total amount of rare earth elements exceeds 0.06% by weight not only show little improvement in oxidation resistance compared to alloys containing less than 0.06% by weight, but also cannot be processed at normal hot working temperatures. states that it is possible.

In JP-A-63-45351, the same <Fe-C
Since adding Y to rAl-based alloys would be expensive, it has been proposed to add only Ln or La excluding Ce in a range of 0.05 to 0.2% by weight. This is because the presence of Ce is the cause of the decrease in hot workability due to the addition of Ln, and furthermore, Ce has the effect of decreasing oxidation resistance.
It states that this is based on the knowledge that adding Ln excluding only Ln makes hot working possible and improves oxidation resistance.

However, Ln is a chemically active element,
Moreover, since their chemical properties are similar, it is not easy to separate the individual elements, and it is very expensive for Mitsume metal, which is a general mixture of Ln. Similarly, separating and removing only Ce also inevitably increases the price. Furthermore, JP-A-63 by the same applicant
Publication No. 42356 discloses Ce,
La, Pr and Nd total 0.01% or more 0.30
% or less has been disclosed, but no studies have been conducted on the hot workability of this alloy.

In addition, these conventional techniques mainly examine the adhesion and oxidation resistance of the oxide film, but the structural durability of the honeycomb body, which is a practically important property required for the foil that constitutes the honeycomb body of the catalyst, has been studied. The influence of foil materials on performance has not been sufficiently investigated.

(Problem to be Solved by the Invention) However, for example, in the case of catalyst carriers for automobiles, the oxidation resistance of the foil is insufficient in the normal usage environment, so it is rare for the catalyst carrier to reach the end of its service life. Rather, in most cases, the honeycomb body reaches the end of its service life due to thermal fatigue due to repeated heating and cooling linked to driving conditions.In other words, during heating, the honeycomb body is rapidly heated from the inside by the high-temperature and high-speed exhaust gas flow. On the other hand, since the traveling wind is forced to cool the honeycomb from the outside, a sharp temperature gradient occurs in the radial direction inside the honeycomb, causing large thermal strain.This thermal strain is not evenly distributed in the radial direction of the honeycomb body, but is This is because the temperature gradient in the radial direction of the honeycomb body differs greatly between the outer layer and the inner layer, and the rate of change in the proof stress of the foil material with respect to temperature differs greatly depending on the temperature range. In other words, the temperature range where the yield strength of the ferritic stainless steel foil that makes up the honeycomb begins to drop significantly, the temperature range where the steepest temperature gradient occurs in the radial direction of the honeycomb body, and the area several layers from the outermost periphery. Also, even when running at a constant speed, there is cooling from the running wind from the outer periphery, so the degree of thermal distortion is alleviated, but the thermal distortion is still concentrated in a few layers from the outermost periphery. Furthermore, when decelerating or running idle, relatively low-temperature gas flows, so the honeycomb body is cooled from the inside as well as the outside, and the area several layers inside from the outermost periphery is at its highest temperature. Thermal distortion is concentrated in the second part.

In other words, due to repeated heating and cooling, the honeycomb body of the catalyst carrier almost always reaches the end of its structural life, resulting in cell collapse and extreme deformation of the carrier due to the accumulation of thermal strain that occurs inside the honeycomb body. . In such cases, the yield strength of the foil at high temperatures is important, and in particular, as mentioned above, the temperature range coincides with the part where a steep temperature gradient occurs in the honeycomb body, that is, according to the measurements by the present inventors, the yield strength of the foil at high temperatures is 600~800.
The foil material has high yield strength in the temperature range of 50°C, and
It has become clear that minimizing the degree of decrease in yield strength due to temperatures above C is effective in improving the structural life of the honeycomb body.

Furthermore, for example, in order to provide products to the general public such as automobiles, it is first desired that the materials be inexpensive and stably supplied. It is important that the manufacturing process can be manufactured to a relatively small size and that the manufacturing cost can be kept low.

Furthermore, since the foil itself has a significantly large surface area relative to its volume and is exposed to high-temperature exhaust gas, it must naturally have excellent oxidation resistance.

In view of these current problems, the present inventors conducted various studies to develop a constituent foil for a catalyst carrier that has all of the above-mentioned characteristics, and arrived at the present invention.

[Means to solve the problem]

That is, in order to improve the oxidation resistance of the foil, 0
．． It is effective to add more than 0.01% Y, and Ln(Ce,
It has been found that the oxidation resistance is dramatically improved compared to that of La, Pr, and Nd.

Furthermore, as mentioned above, in order to improve the structural durability of the catalyst carrier due to heating and cooling, it is necessary to
It is necessary to improve the yield strength at temperatures of 00 to 850°C, and as a result of various studies for this purpose, the addition of Nb and/or Ta or the addition of Mo and/or W is effective, and among these, the addition of Ta is particularly effective. In addition to being effective, it has been found that adding Mo and/or W at the same time as Ta and/or Nb further improves the yield strength, particularly at high temperatures of 800° C. or higher.

Furthermore, as a result of investigating the toughness of hot-rolled sheets, which is a problem in the production of this type of ferritic stainless steel, it was found that the toughness can be significantly improved by adding Ta or Nb. It has become clear that the manufacturing process can improve its properties to a level that allows for mass production.

In addition, during these various studies, Ti, Zr and V
We also investigated the effects of Ti, and found that Ti hardly increases the yield strength at high temperatures, and that excessive addition actually reduces the toughness of hot-rolled sheets. Although it slightly increased the high temperature yield strength, it was found that it significantly reduced the oxidation resistance of the foil and also impaired the toughness of the hot rolled sheet. Furthermore, it became clear that in case (2), neither the high-temperature yield strength improvement effect nor the hot-rolled sheet toughness improvement effect was observed.

In other words, based on the above study results, the present invention not only improves the oxidation resistance of the foil and the adhesion of the film even in high-temperature exhaust gases, but also improves this. This was achieved with the aim of providing a heat-resistant stainless steel foil that is effective in improving the structural durability of steel sheets, has excellent manufacturability in terms of hot workability and toughness of hot-rolled sheets, and can be supplied at a low cost. It is something.

However, the specific means are as follows.

In weight% Y: more than 0.01% and less than 0.5% Al: 4.5% and more and less than 6.5% Cr: 13% and more and less than 25% C: less than 0.025% N: less than 0.02% C+N : In addition to 0.03% or less, it contains at least one of Mai 1% to 4% or W: 1% to 4% within the range of Mo + W: 4% or less, and the balance consists of Fe and inevitable impurities. It is a heat-resistant stainless steel foil for combustion exhaust gas purification catalyst carrier, which is characterized by weight percentage: Y: more than 0.01% but not more than 0.5% Aj2: 4.4% or more and 6.5% or less Cr: 13% or more 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) xl, 5 or more and 3% or less, or Nb: (93・C%/12+93・N%/14)
A heat-resistant stainless steel foil for a combustion exhaust gas purification catalyst carrier, characterized in that it contains at least one of ×0.8 or more and 3% or less in the range of Ta+Nb: 3% or less, and the balance consists of Fe and inevitable impurities.

Furthermore, if necessary, by adding at least one of MO=4% or less or W: 4% or less in weight percent, the yield strength, especially on the high temperature side, can be further improved.

[For production]

Next, the reasons for limiting the components in the present invention and their effects will be explained in detail. In addition, all chemical compositions in this specification are weight %.

(1) Y: Y has the effect of improving the foil's resistance to abnormal oxidation, and the life of the foil until abnormal oxidation occurs is 0.01%.
Exceeding this will significantly improve the performance compared to less than that, but
When it falls below 0.5%, it starts to decrease again. Therefore, the range is limited to more than 0.01% and less than 0.5%.

(2), 6/! : Al is a basic element that ensures oxidation resistance in the present invention, and if it is less than 4.5%, the protection of the oxide film in the exhaust gas is poor in the case of foil, and abnormal oxidation easily occurs. Therefore, it cannot be used as a catalyst carrier. On the other hand, 6.5
If the content exceeds %, the toughness of the hot-rolled sheet will be extremely reduced and manufacturability will be impaired, and the coefficient of thermal expansion of the foil will increase, and when used as a catalyst carrier, the foil will suffer from repeated heating and cooling. Heat fatigue increases. 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 that ensures the corrosion resistance of stainless steel. In the present invention, the main component of oxidation resistance is A f 203
Although it is present in the film, if Cr is insufficient, its adhesion and protective properties will decrease. On the other hand, when Cr becomes 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 yield strength of the foil at high temperatures,
It is an important additive element for improving the structural durability of the catalyst carrier. The action of Ta is to combine with C and N in the steel to form carbonitrides, which exert a so-called precipitation strengthening effect, and in addition, the excess dissolves in the base material and exerts a solid solution strengthening effect. This results in improved high-temperature yield strength. In this case, although the precipitation strengthening effect is very effective, for example, during long-term use in a temperature range exceeding 750°C, the precipitates gradually aggregate and coarsen, causing changes in the metal structure and reducing its effectiveness. There are cases where On the other hand, solid solution strengthening is not as effective as precipitation strengthening, but
Even during long-term use, there is almost no decline in the above-mentioned effects due to changes in the metal structure. Therefore, Ta
Even if the precipitation strengthening effect is lost due to the phenomenon described above, in order to maintain the solid solution strengthening effect, C
, N needs to be added in somewhat excess amount relative to the amount of N. From this perspective, the inventors investigated (1
81・C%/12+ 181・N%/14) ×1.
It is necessary to add 5 or more.

However, when the amount of Ta becomes extremely excessive, the Laves phase precipitates, making the steel ingot after casting easy to crack, and the yield strength at high temperatures begins to decrease. In the range of the amount of C and H according to the present invention, the amount is 3%. Due to these circumstances, the range of addition of Ta is as follows.

Ta: (181・C%/12+ 181・N%
/14) X 1.5 or more and 3% or less Furthermore, since Ta fixes C and N, it has the effect of improving the toughness of the hot-rolled sheet, and this effect is sufficiently brought about within the above addition range.

(5) Nb: In the present invention, like Ta, Nb is an important additive element for improving the yield strength of the foil at high temperatures and improving the structural durability of the catalyst carrier. Nb improves high-temperature yield strength through both precipitation strengthening and solid solution strengthening for the same reason as Ta.

In this case, as in the case of Ta, the addition range is limited due to the quantitative relationship with C and N, and at least the addition of (93・C%/12+93・N%/14)×0.8 or more is limited. is necessary.

On the other hand, like Ta, if Nb is added in extremely excess, L
Aves phase is formed, causing the same problems as in the case of Ta. Therefore, the upper limit value is limited from this point of view, and according to studies by the present inventors, is 3% or less. Due to these circumstances, the range of addition of Nb is as follows.

Nb: (93・C%/12+93・N%/14
) x 0.8 or more and 3% or less Furthermore, Nb has the effect of significantly improving the toughness of the hot-rolled sheet, and this effect is sufficiently brought about if it is added within the above range. In the case of Ta + Nb, the upper limit is set to 3% for the same reason.

(6) Mo, W: Mo and W are important additive elements in the present invention, particularly for improving the high-temperature proof stress and improving the structural durability of the catalyst carrier. The action of Mo and W is to form a solid solution in the base material of the steel and improve high-temperature yield strength through solid solution strengthening action. At that time M.

A considerable amount of W is dissolved in solid solution without forming harmful precipitated phases, and a large strengthening effect can be obtained. In addition, there is almost no change in the metallographic structure even when heated at high temperatures and for long periods of time.
There is almost no change in the reinforcing effect over time.

On the other hand, as mentioned above, in the present invention, the high-temperature yield strength can be improved by adding an appropriate amount of Ta and/or Nb, but among the strengthening effects of Ta and Nb, the effect of precipitation strengthening is limited by use at high temperatures. In some cases, the content may gradually decrease, and excessive addition may conversely reduce the high-temperature proof strength. However, M.

and/or W is not affected in any way by the presence of Ta and/or Nb;
It dissolves in solid solution in the base material without forming a harmful precipitate phase to a considerable extent, and a large solid solution strengthening effect can be obtained. That is, Ta
And/or M is added to the alloy whose high temperature strength has been improved by adding Nb.

By adding and/or W, the yield strength at high temperatures can be further improved.

From this point of view, the amount of Mo and/or W to be added was determined, and according to the results of the study by the present inventors, (1) When Nb and/or Ta are not added, in order to obtain a sufficient solid solution strengthening effect, The amount of Mo added is required to be 1% or more,
Also, in the case of W, the lower limit is 1%, and (2) when Nb and/or Ta are added, there is no lower limit for the addition of Mo and/or W to obtain a sufficient solid solution strengthening effect.

On the other hand, since most of both Mo and W form a solid solution, the metal base is strengthened as the amount added increases, but when added in excess, the toughness decreases. Therefore, M
The amounts of O and W added are restricted from this point, and the upper limit values for both are 4%.

Further, similar effects can be obtained by adding Mo and W in combination at the same time, but the upper limit in this case is preferably 4% or less for Mo+W.

(7) C, N: In the present invention, both C and N significantly reduce the toughness of the hot rolled sheet. This adverse effect can be suppressed by the action of Ta or Nb, but if C exceeds 0.025%, or N exceeds 0.02%, or C+N
If the total amount exceeds 0.03%, it becomes difficult to restore toughness. Therefore, from this point of view, the range is C: 0.025% or less, N: 0.02% or less, and C+N: 0.03% or less.

In addition, C and N precipitate as carbonitrides, which have the desirable effect of improving high-temperature yield strength through precipitation strengthening, but as mentioned above, this effect decreases as the precipitates become coarser. decreases. When large amounts of C and N are contained, even if Ta and/or Nb are added above the above lower limit, coarsening of the precipitates is promoted and the rate of decrease in the strengthening effect increases. That is,
When large amounts of C and N are contained, the average particle size of carbonitrides becomes large, and it is difficult to obtain a uniform and fine precipitation form that is effective for precipitation strengthening. From this point, C,
The content of N is limited, and in the present invention, C: 0.
0.025% or less, N: 0.02% or less, and C+N
: About 0.03% or less.

Due to the above circumstances, the range of C and N is C: 0.0
25% 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 very early stage of the oxide film, harming the subsequent formation of the AltCh film, and causing structural defects to remain in the film. Therefore, it is desirable to limit the content to 0.3% or less.

Si: St is an element that increases (decreases) the toughness of hot-rolled sheets while improving oxidation resistance.High A! ferritic stainless steels like those of the present invention inherently have excellent oxidation resistance.
From the viewpoint of toughness, it is desirable to suppress Si to a small amount, and its upper limit is 0.5%.

P: Since P has the effect of reducing the toughness of ferritic stainless steel, Fe − which inherently has poor toughness
For Cr-An stainless steel, the amount added is limited from this point of view, and in the present invention, the amount is 0.1%. Further, addition of P in such a range does not have an adverse effect on oxidation resistance.

S: S reduces oxidation resistance, so in the present invention, 0.
It is desirable to suppress it to 0.003% or less.

The Fe-Cr-Al alloy of the present invention having such a structure can be produced by melting, hot rolling, and cold rolling processes similar to the mass production process of ordinary ferritic stainless steels, as well as an appropriate annealing process as necessary. By combining them, it is possible to manufacture up to about 504 foils.

In addition, the foil produced in this way, the exhaust gas purification catalyst carrier and the catalyst device constructed using this foil not only have a significantly high resistance to abnormal oxidation even in a high-temperature combustion exhaust gas atmosphere, but also have a high resistance to abnormal oxidation even in a high-temperature combustion exhaust gas atmosphere. Because of its high yield strength, it has a high resistance to thermal fatigue as a honeycomb body, and is resistant to heating and
It has excellent structural durability even under usage conditions that require repeated cooling.

[Example] Next, the effects of the present invention will be explained in more detail with reference to Examples.

Example 1 Table 1 shows the chemical compositions of the alloys of Examples and Comparative Examples of the present invention. 25 kg of these steels were melted in a vacuum high-frequency induction furnace, cast into ingots, and heated to 1200°C.
Immediately after holding for 1 hour, hot rolling was started and the product was rolled to a thickness of 4 cm, and then allowed to cool naturally.

At this time, cracking was observed in BIO during rolling, and B6
When the finished board of B8 was observed, edge cracks and surface cracks were observed, although they were relatively minor. For the other steels, no particular problem occurred during hot rolling in both the Examples and Comparative Examples. These results are shown in the hot rolling property column of Table 2. Those in which cracks occurred in the hot rolled sheets are marked with an X. Items with no problems are indicated with an O mark.

Next, the toughness of these hot rolled sheets was investigated. The evaluation of toughness is
A V-notch Charpy specimen of sub-size (thickness: 2.5 mm) in accordance with the JIS standard was taken parallel to the rolling direction and subjected to an impact test. d (vTz: ”C
). The hot rolled sheet investigation results are shown in the column of hot rolled sheet toughness in Table 2. Here, vT is 10
Those whose vTz is less than 0°C are marked with a circle, and those whose vTz is 100°C or higher are marked with an x.

Note that items marked with an O can be mass-produced using normal stainless steel sheet factory production processes, while items marked with an X are practically difficult to manufacture, or even if they can be manufactured, there is a significant manufacturing process. This causes an increase in costs. All the alloys of the examples have good manufacturability.

Furthermore, after annealing these hot-rolled sheets at 1200°C for 15 minutes, tensile test specimens with a thickness of 3 mm, a width of 30 mm, and a length of 100 mm were processed and tested in the temperature range of 600°C, 700°C, and 800°C. A tensile test was conducted. The results are shown in the tensile test column of Table 2, and the criteria for determining the achievement of high temperature strength were as follows. In other words, the yield strength at 600℃ is 20kgf/m
Items with a yield strength of 11 kgf/■2 or higher at 700°C and a yield strength of 4.5 kgf/2 at 800°C are marked O, and other items are marked with an X. was taken as the average value of each three experimental values.

All of the alloys in the Examples exhibit good high-temperature yield strength.

For A5 to 8 of the Examples and B5-10 of the Comparative Examples, presence or absence of a decrease in strength over time during long-term use at high temperatures;
That is, in order to investigate high-temperature structural stability, a plate-shaped plate prepared in the same manner as above was subjected to a tensile test at 850°C for 1000°C.
After holding for a period of time, a tensile test was performed. The results obtained in the third
It is summarized in the table. The achievement criteria for high temperature proof strength are the same as above. A5 strengthened at high temperature by adding Mo and/or W
It can be seen that alloys No. 8 to 8 have excellent high-temperature structural stability.

Examples and Comparative Examples B1-5. B7 and B9 had good toughness, and after hot rolling, descaling, cold rolling (some alloys were warm rolled), and annealing were repeated to obtain foils with a thickness of approximately 50 mm. Comparative Example B6° Since B8 and BIO had poor toughness, they were carefully rolled in a warm manner during the above steps.

Test pieces measuring 50 m long and 20 mm wide and 25 cm long were taken from these foil materials and subjected to an oxidation test at 1150 DEG C. in the atmosphere. At this time, a test was conducted in which each foil material was heated for 25 hours and then allowed to cool until abnormal oxidation occurred in each foil material. These results are shown in the column of abnormal oxidation life in Table 2. A foil material with an abnormal oxidation life of 200 hours or more is marked with an ○, and a foil material with no droplets for 200 hours is marked with an X. Each of the steel foils of this example has a long life of 200 hours or more.

The following is a margin table (continued) The following is a margin table (continued) The following is a margin table Example 2 In Table 1, A3. A total of 5 types of thickness 50, A6 and A23, and Bl and B5 as comparative examples.
A piece of PSA foil with a width of 97m and a sinusoidal waveform with a period of 3.5cm and an amplitude of 3.2cm (corrugated plate).
was overlapped with this unprocessed foil (flat plate) band and rolled up to create a honeycomb-shaped cylinder with an apparent diameter of about 42 m + and a length of about 97 wm, and a commercially available Ni-based brazing material was added to the corrugated plate/flat plate joint as appropriate. 3 Xl0
It was heated in a vacuum of about -' Torr and subjected to brazing treatment.

The thus obtained honeycomb structure after brazing was installed in a horizontal furnace-like heating furnace with a core tube having an inner diameter of 45 am+, and engine exhaust gas was introduced from one end of the furnace core tube at an amount of 10 mm. /sin was introduced and heated to 1100°C, and at the same time, the honeycomb body was removed every 25 hours and visually inspected for defects such as cell deformation, foil breakage, etc. 8 times (equivalent to 200 hours) repeated.

At this time, the engine exhaust gas is a 4-cylinder gasoline engine with a displacement of 2000 cc at a rotation speed of 150 rpm and a load of 5 kg.
It was generated at an air-fuel ratio of 13 under operating conditions of 100 m and introduced into the heating furnace through a conduit kept at 150°C. The obtained results are shown in Table 4. Honeycomb structures in which abnormal oxidation did not occur after the test are indicated by O marks, and those in which oxidation occurred are indicated by X marks. Items with no defects are marked with an ○, and items with defects are marked with an x. Abnormal oxidation and defects in the honeycomb body did not occur in the honeycomb bodies of Examples. Therefore, it can be seen that all the honeycomb bodies of Examples not only have excellent resistance to occurrence of abnormal oxidation but also have excellent structural durability.

Table 4 Example 3 100 kg of foil with the ingredients shown in Table 5 was melted and cast in a vacuum high-frequency furnace, heated to 1200°C, hot rolled to 30%, air cooled, and further heated to 1150″C. Rolled to a thickness of 2
．． We obtained hot-rolled sheets of 5 pieces.

Furthermore, a foil coil with a thickness of 50 μm and a width of 97 mm was produced using the steps of shot blasting, pickling, cold rolling, annealing, degreasing, pickling, foil rolling, degreasing, slitting, foil rolling, and vacuum annealing. .

This foil was prepared using a method similar to that described above, with a diameter of 10 mm.
A cylindrical honeycomb with a length of 0 m and a length of 97 cm was made, and this was installed inside a ferritic stainless steel cylindrical outer cylinder with an inner diameter of 100 cm, a length of 97 cm, and a plate thickness of 1.5 cm. A honeycomb catalyst carrier was formed by joining the catalyst carrier with brazing, and then it was installed in the exhaust gas path of the engine and subjected to an engine bench test.

In the engine test, the engine of Example 2 was operated with the gas temperature on the side entering the catalyst carrier at 900°C for 9 minutes, and then the engine was stopped and forced to cool down.
Heating/cooling until the catalyst carrier temperature is below 100℃
The cooling cycle was repeated 1000 times. The obtained results are shown in Table 6. After the test, honeycomb bodies with no defects such as cell collapse, foil breakage, or misalignment of the end face in the gas flow direction are marked O. Although slight cell deformation occurred in the honeycomb body of the example, which is shown with an X mark for those in which defects occurred, no other severe damage occurred, whereas in the comparative example, the cell deformation occurred. There was significant damage such as crushing, broken foil, and part of the end face protruding in the direction of gas flow. Therefore, it can be seen that all of the honeycomb bodies made of foil materials of Examples have excellent structural durability.

Below is a blank table [Effects of the invention] As is clear from the examples, Fe-C according to the present invention
r-Al alloys have good hot workability and hot-rolled plate toughness, and are excellent in manufacturing foils, etc., so manufacturing costs can be kept lower, and they also have excellent oxidation resistance. It has excellent resistance to abnormal oxidation, as well as excellent thermal fatigue resistance due to its high yield strength in high temperature ranges.It also has excellent oxidation resistance in exhaust gas and shape as a honeycomb structure made by brazing alloy foil. Excellent structural durability against changes, etc.

Therefore, Fe-Cr-,64! of the present invention! The alloy is suitable as a foil for exhaust gas purification, and is particularly suitable as a catalyst support for an automobile exhaust gas purification device.

Claims (1)

[Claims] 1. Y: more than 0.01% but not more than 0.5% Al: 4.5% to 6.5% Cr: 13% to 25% C: 0.025% or less N: 0.02% or less C+N: 0.03% or less, plus Ta: (181・C%/12+181・N%/14)×
1.5 or more and 3% or less or Nb: (93・C%/12+93・N%/14)×0.
1. A heat-resistant stainless steel foil for use as a combustion exhaust gas purification catalyst carrier, characterized in that it contains at least one of Ta+Nb in an amount of 8 to 3% in a range of 3% or less, and the balance consists of Fe and unavoidable impurities. 2. In weight% Y: more than 0.01% and less than 0.5% Al: 4.5% and more and less than 6.5% Cr: 13% and more and less than 25% C: less than 0.025% N: 0.02% In addition to the following C + N: 0.03% or less, at least one of Mo: 1% to 4% or W: 1% to 4% is included within the range of Mo + W: 4% or less, and the balance is Fe and unavoidable A heat-resistant stainless steel foil for combustion exhaust gas purification catalyst carrier, which is characterized by being composed of impurities. 3. Furthermore, at least one type of M with a weight percentage of Mo: 4% or less or W: 4% or less
The heat-resistant stainless steel foil for a combustion exhaust gas purification catalyst carrier according to claim 1, which contains o+W within a range of 4% or less.