JPH059664A - Fe-Cr-Al quenching alloy foil with excellent oxidation resistance - Google Patents

Abstract

(57) [Summary] [Objective] Fe-Cr-Al, which can be used in the honeycomb material for converters for automobile exhaust gas, can be manufactured stably without quenching nozzles using the quenching method, and has excellent oxidation resistance. Proposal of series alloy ribbon. [Composition] Cr: 5-30 (wt)%, Al: 2-15%, Si:
1.5-3%, REM (Y, Ce, La, Pr, Nd): 0.07-2.
A Fe-Cr-Al-based quenched alloy foil containing 0%, the balance being substantially Fe, and having a crystal grain size of 10 µm or less and excellent in oxidation resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Fe-Cr-Al alloy foil suitable for applications requiring high-temperature oxidation resistance such as honeycomb materials, high-temperature heating elements, and resistance materials used in automobile exhaust gas converters. .

[0002]

2. Description of the Related Art Fe-Cr-Al alloys have been used for a long time in heating wires and the like, and various proposals have been made for them. For example, in JP-A-58-177437,
Cr: 8 to 25 wt%, Al: 3 to 8 wt%, and further contains all rare earth elements
It has been proposed to add 0.002 to 0.05 wt% Ce, La, Nd, etc. up to 0.06 wt% to improve the scale releasability. However, such Fe-Cr-Al-REM alloys are used in automobile exhaust gas converters, resistance heating elements, radiation heating element support materials, etc. in a relatively thick plate state. However, for example, when it is used in an engine direct type (exhaust manifold type) whose ambient temperature is higher than usual in a catalytic converter for purifying exhaust gas of automobiles with a plate width of 50 mm or more,
Each time the vehicle is started, accelerated, or stopped, it is subjected to severe high temperature repeated oxidation, which causes abnormal oxidation and cannot be used. Also,
It is difficult to manufacture a high-Cr, Al foil that can withstand this environment by rolling normally, and further heat treatment and cold rolling are required repeatedly, resulting in an increase in cost.

Therefore, the present inventors have paid attention to the rapid cooling ribbon method which has already omitted the rolling step, and have proposed to increase the addition of rare earth elements in order to improve the oxidation resistance. The rapid cooling ribbon method facilitates thinning of high-Cr, Al difficult-to-machine materials, and is expected to bring significant cost reductions and dramatic improvements in oxidation resistance. For example, Japanese Laid-Open Patent Publication No. 63-42347 proposes to add REM in a large amount of 0.06 to 0.30 wt% to improve the peeling property of an oxide film and directly produce a foil by a quenching method. Further, in Japanese Patent Laid-Open No. 63-42356, in order to improve the oxidation resistance, Al
Is 8 to 15 wt% and a quenching method is proposed because it is difficult to produce foil in the usual process of rolling.

However, the large amount of REM as described above
In the laboratory, for example, a heat size of 10 to 100 g and a plate width of 10 are used for thinning a plate by using an additive or high Al-based component alloy system by a quenching method.
mm, 50 μm thick ribbon plate is no problem, but the above exhaust gas converter material for automobiles has a plate width of 50 mm or more, heat size
In the manufacturing process of process materials of 10 kg or more, there are problems such as nozzle clogging, REM yield, internal defects, etc., and it has not yet been put to practical use.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to propose a Fe-Cr-Al alloy ribbon having excellent oxidation resistance, which can be stably manufactured by using a quenching method without nozzle clogging. It is a thing.

[0006]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that Fe-Cr is added by adding 0.07 wt% or more of REM (usually added in a larger amount than in a rolled material).
-In order to improve the oxidation resistance of the Al alloy foil and reduce nozzle clogging, ribbon surface properties and internal defects in the quenching method, Si is added in excess of the conventional level, and quenching is performed at a specified cooling rate or higher. We have found that coagulation is extremely effective.

The present invention is based on the above findings,
The composition of the present invention is as follows: Cr: 5-30 wt%, Al: 2-15 wt%, S
i: 1.5 to 3 wt%, REM (Y, Ce, La, Pr, Nd): 0.0
7-2.0 wt%, and if necessary, Ti, Nb, Zr,
0.001 to 0.5 wt% of 1 or 2 or more kinds of V is contained, the balance is Fe and unavoidable impurities, and the grain size is 10μ.
Fe-Cr with excellent oxidation resistance characterized by being less than m
-Al-based quenched alloy ribbon, preferably a quenched alloy ribbon having a plate thickness of 20 to 200 µm.

[0008]

[Operation] First, the reasons for limiting the component composition of the present invention will be described. Cr: 5-30 wt% If Cr is less than 5%, it is difficult to obtain the expected oxidation resistance even if Si is added by 1.5 wt% or more and rare earth element is added by 0.07 wt% or more, while if it is more than 30 wt%, it is rapidly cooled. When the nozzle is clogged, it becomes brittle and the workability deteriorates.
° Bending becomes impossible. Therefore, Cr is limited to the range of 5 to 30 wt%.

Al: 2 to 15 wt% Even if Si is added in an amount of 1.5 wt% or more and rare earth element is added in an amount of 0.07 wt% or more, if Al is less than 2 wt%, the oxidation resistance cannot be secured, while Al in excess of 15 wt% is not added. It is limited to the range of 2 to 15 wt% because it lowers the workability and easily causes nozzle clogging. Especially when the thickness of the exhaust gas converter foil is 20-80 μm, 2
It is desirable to add Al of about 8 wt%. On the other hand, for a foil having a plate thickness of 80 μm or more for a heating resistor, a nozzle having a large slit interval can be used by the single roll method, and since nozzle clogging does not occur, 8 to 15 wt% of Al can be added.

Si: 1.5 to 3 wt% In the present invention, nozzle clogging during rapid solidification of a conventional Fe-Cr-Al alloy is improved by adding Si. 1.5
If it is less than wt%, even if the plate thickness is 200 μm or less, sufficient oxidation resistance cannot be obtained even if REM: 0.07 wt% or more is added, and nozzle clogging tends to occur during rapid solidification. On the other hand, if it exceeds 3 wt%, a large amount of oxidation resistance can be expected, but even if it is rapidly solidified at a high cooling rate with a plate thickness of 20 μm or less and a crystal grain size of 10 μm or less, the workability cannot be improved, and the workability of the foil (180 ° Bending) is limited. On the other hand, it is known that the grain size of the ordinary rolled material becomes coarse by adding Si (1 wt% or more),
Although workability is deteriorated and oxide scale is exfoliated, in the present invention, since the cooling rate is high and the crystal grain size is small, the processability is also improved and the exfoliation resistance of the oxide scale is also improved. FIG. 1 is a graph showing a part of Examples described later from the viewpoints of the amount of increase in oxidation and time, and a significant improvement in oxidation resistance life is observed in the proper range of Si content. Further, the melting point of the Fe-Cr-Al alloy is lowered by the addition of Si, but if it exceeds 3 wt%, no significant effect is seen and 1.5 to 3 wt% is effective for nozzle clogging. Further, the yield of REM, which will be described later, is dramatically improved by adding Si in an amount of 1.5 wt% or more due to the exothermic reaction of Si.

REM (Y, Ce, La, Pr, Nd): 0.07 to 2.
0 wt% In the present invention, any one or more of Y, Ce, La, Pr and Nd can be added as a rare earth element. If the thickness is less than 0.07 wt% and the plate thickness is 200 μm or less, sufficient oxidation resistance cannot be obtained even if Si is added in an amount of 1.5 wt% or more. Further, even if it exceeds 2.0 wt%, the oxidation resistance is not improved, and the nozzle is likely to be clogged during rapid cooling.

Ti, Nb, Zr, V: 0.001 to 0.5 wt% One or more of these elements can be added, if necessary, within the above ranges, respectively. It is effective for peeling resistance of the oxide film. However, if less than 0.001% of each, the effect does not appear
If it exceeds 0.5wt%, the oxidation rate will increase, so 0.001〜
Limited to 0.5 wt%.

Next, the reasons for limiting the crystal grain size will be described.
The crystal grain size is set to 10 μm or less in order to compensate the toughness deteriorated by the addition of Si from the viewpoint of the workability of the foil. That is, when the crystal grain size exceeds 10 μm in the case of the composition of the present invention, 1
The 80 ° bending test makes it easier for the foil to bend. The grain size of the ribbon can be controlled by the cooling rate during rapid solidification.
For example, a single roll method with a plate thickness of about 50 μm and a crystal grain size of 10 μm
In order to produce a foil having excellent surface properties with few internal defects, for example, a roll peripheral speed of 18 m / sec or more and a roll-nozzle gap of 0.3 mm or less are desirable. Also,
Even if the plate thickness is as thick as about 200 μm, the crystal grain size can be reduced to 10 μm or less by appropriately selecting the roll peripheral speed and the roll-nozzle gap. Also, when the plate thickness is 100 to 200 μm, the crystal grain size is 10 μm by the twin roll method and the melt drag method.
It is possible to produce foils of m or less.

In the single roll method, the gap between the pouring nozzle and the cooling roll is made extremely small (for example, 0.1 to 1.5).
mm), and since a nozzle having a slit shape is used, nozzle clogging is likely to occur, but the Fe-Cr-Al alloy of the present invention can exert its effect sufficiently even in the single roll method described above, and continuous without nozzle clogging. Can produce long and wide foils.

Further, as a main application of the alloy foil of the present invention, there is a honeycomb material used for an automobile exhaust gas converter.
If the plate thickness is less than 20 μm, the oxidation resistance required for use in the engine direct catalytic converter cannot be obtained even with the component system of the present invention, while if the plate thickness exceeds 80 μm, exhaust resistance increases and engine characteristics deteriorate. Therefore, preferably 20
It is preferable that the thickness is in the range of μm to 80 μm. In addition, in the case of ordinary catalytic converters (underfloor type), resistance heating elements (electrothermal heaters), radiant heating element supports, etc., a maximum of 200 μm is possible in consideration of workability. The alloy foil thickness of the present invention depends on the application. It is desirable that the thickness be 20 μm or more and 200 μm or less.

[0016]

【Example】

Example A Alloys having the compositions shown in Tables 1, 2, and 3 were all finished into foils with a plate thickness of 50 μm by the production methods shown in Tables 1, 2, and 3 to obtain crystal grain size, workability, oxidation resistance, and nozzle clogging. Examined.

As for workability, a foil having a thickness of 50 μm is R = 0.2 mm.
Bending was performed at 180 °, and those that cracked were marked as ×, and those that did not crack were marked as ○. The oxidation resistance was determined by heating a 50 μm-thick foil in the air at 1200 ° C., and taking the time when the oxidation weight increase was 2.0 mg / cm ² or less as the oxidation resistance life. The 1200 ° C atmospheric oxidation test is a high oxidation resistance accelerated test.

Specimen Nos. 1 to 7 and No. 11 are widths obtained by injecting the molten master alloy into a single roll having a diameter of 500 mm rotating at a roll peripheral speed of 20 m / sec in an argon atmosphere and rapidly solidifying.
It is a 100 mm sample. Sample Nos. 12 and 13 are also single rolls with peripheral speeds of 18 m / sec and 15 m / sec, respectively. Sample Nos. 14 and 15 were subjected to single roll cooling under the same conditions as those of Samples Nos. 1 to 7, but nozzle clogging occurred and no plate was formed. By the way, No. 14 has a high Cr of 35 wt%,
No. 15 has a high La of 3.0 wt%.

Next, Nos. 8 to 10 are diameters of 200 m in which a molten mother alloy is rotated at a roll peripheral speed of 30 m / sec in an argon atmosphere.
It was performed at a roll peripheral speed of 10 m / sec by the twin roll method of m. Similar to No. 12, No. 17 had nozzle clogging because the Si content was less than 1.5 wt%, and the foil became dulled. Also
No. 18 was sprayed onto twin rolls with a diameter of 550 mm rotating at a roll peripheral speed of 3 m / sec, and was rapidly solidified to a thickness of 0.3 mm and a width of 500.
mm steel strip was made, and then cold and warm rolling were performed.
Plate cracking occurred during rolling, and it could not be rolled to a thickness of 100 μm or less.

Further, Nos. 19 and 20 were alloy melted in a vacuum melting furnace in a conventional process, and an ingot was made into a hot coil in a hot rolling process. In No. 19, since a large amount of Si and La were added, a sound hot coil could not be obtained due to ear cracking, etc., and subsequent processing and testing were not performed. No. 20 can be rolled, but has a short oxidation life, and there is a problem in use, for example, in the engine direct type.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

Example B Further, as a resistance heating element, a quenched alloy foil having a plate thickness of 100 μm and having the following compositions, respectively, was used to examine the oxidation life.
No. 1: 30wt% Cr, 15wt% Al, 3wt% Si, 0.1wt% La composition system with a crystal grain size of 5μm and a ribbon width of 10mm has a life of 1150.
It was 600 hours in the air atmosphere at ℃ (invention).

No. 2: 20 wt% Cr, 12 wt% Al, 1.5 wt% S
The life of a ribbon having a plate width of 10 mm and a crystal grain size of 7 μm in the Y component system of 0.08 wt% was 500 hours in an air atmosphere of 1150 ° C. (the present invention). No. 3: 10wt% Cr, 1.5wt% Al, 1wt% S
i, 0.06 wt% La component system, a ribbon having a grain size of 10 μm and a plate width of 10 mm had a life of 100 hours in an atmosphere of 1150 ° C. (comparative example).

No. 4: 20 wt% Cr, 5 wt% Al, 0.2 wt% S
The life of a ribbon having a plate width of 10 mm and a crystal grain size of 5 μm was 200 hours in an air atmosphere of 1150 ° C. (comparative example).

[0027]

EFFECTS OF THE INVENTION By limiting the composition as in the present invention and forming a quenched ribbon having a crystal grain size of 10 μm or less, a material which can be used for an exhaust gas catalytic converter having excellent workability and oxidation resistance. Can now be provided.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in an accelerated oxidation test.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Shimizu             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Corporate Technology Research Division

Claims (3)

[Claims] 1. Cr: 5-30 wt%, Al: 2-15 wt%, Si:
1.5 to 3 wt%, REM (Y, Ce, La, Pr, Nd): 0.07 to
A Fe-Cr-Al-based quenched alloy foil having excellent oxidation resistance, containing 2.0 wt%, the balance being Fe and unavoidable impurities, and having a crystal grain size of 10 µm or less. 2. Cr: 5-30 wt%, Al: 2-15 wt%, Si:
1.5 to 3 wt%, REM (Y, Ce, La, Pr, Nd): 0.07 to
2.0 wt%, 1 or 2 or more of Ti, Nb, Zr, V: 0.001
A Fe-Cr-Al-based quenched alloy foil having excellent oxidation resistance, characterized in that it contains ˜0.5 wt%, the balance being Fe and inevitable impurities, and having a crystal grain size of 10 μm or less. 3. The rapidly-quenched alloy foil having excellent oxidation resistance according to claim 1, wherein the rapidly-quenched alloy foil has a plate thickness of 20 to 200 μm.