JP3242573B2 - Stainless steel wire and fiber excellent in high temperature oxidation resistance and heat deformation resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Al-containing ferritic stainless steel wire and fiber used for heat-resistant applications such as exhaust system parts for automobiles, and in particular, to prevent transmission of engine vibration to a rear exhaust pipe. The present invention relates to a wire and a fiber used as a material for an inner blade in a flexible tube and a sound absorbing material in a muffler.

[0002]

2. Description of the Related Art Heat-resistant wires and fiber materials in exhaust system parts for automobiles, such as inner bladders in flexible tubes and sound-absorbing materials in mufflers, are 700 to 8 depending on exhaust gas.
Stainless steel wires such as SUS430 and SUS304 have been used because they are exposed to a high temperature environment of 00 ° C. However, in recent years, emission regulations for automobiles have become stricter from the perspective of preventing global warming and pollution,
Exhaust gas temperature tends to rise with the advancement of engine performance, and the temperature at which these members are used is approaching 900 ° C. Therefore, existing materials have insufficient oxidation resistance and high-temperature strength. Does not stand use.

[0003] As materials that can withstand such severe conditions, there are super heat-resistant alloys such as Incoloy and Hastelloy, but these are not practical because they are very expensive. On the other hand, as a relatively inexpensive material, there is a high Al-containing ferritic stainless steel (Fe-Cr-Al steel, Japanese Patent Application Laid-Open No. 48-102022, etc.) which has been widely used as a heating appliance and an electric heating material since ancient times. However, it cannot be used for automobile exhaust system parts because the oxidation resistance and high-temperature strength are insufficient. Therefore, recently, as a base material for a catalyst carrier in an automobile exhaust gas purifying apparatus, a material has been developed in which a rare earth element or the like is further added to a conventional high-Al-containing ferritic stainless steel to improve heat resistance (Japanese Patent Application Laid-Open No. Hei 4 (1994)). 354850, JP-A-6-172932
No. JP-A-6-172933).

[0004]

2. Description of the Related Art In order to improve the oxidation resistance of ferritic stainless steels at high temperatures, including ferritic stainless steels containing high Al, which are used as base materials for catalyst carriers in exhaust gas purification systems for automobiles. Is Cr, A
It is known that addition of l, Si, rare earth element, Y, and the like and increase of the addition amount are effective. However, the addition of a large amount of these elements not only increases the cost of raw materials,
The cold workability is remarkably deteriorated, and it becomes a significant obstacle to wire drawing, which is a process from two directions, as compared with plate rolling, which is a process from one direction. In other words, although it is possible to roll to a foil (plate thickness of about 50 μm) for use as a catalyst carrier, it has a thinner and fibrous form that satisfies the application to inner braiders in flexible tubes and sound absorbing materials in mufflers. It is extremely difficult to do so.

[0005]

The stainless steel wires and fibers used in automobile exhaust systems are usually cold drawn to a diameter of 1 mm or less and cold drawn to a diameter of usually 5 mm or less. After processing, it is further processed into a fibrous form and used. The present invention relates to a ferritic stainless steel and a ferritic stainless steel used for an automobile exhaust system component having improved oxidation resistance and heat deformation resistance at high temperatures without causing a reduction in cold drawing to a small diameter. The aim is to provide stainless steel fibers.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a high Al-containing ferritic stainless steel wire and fiber used for exhaust system parts for automobiles by optimizing the amounts of Mo, Al and Si added. The oxidation resistance and the heat deformation resistance in the temperature range of 800 to 900 ° C. are further improved without impairing the cold drawing workability at the stage.

That is, the first aspect of the present invention is that
C: 0.10% or less, Si: 0.3 to 1.5%, M
n: 1.0% or less, Cr: 17.0 to 26.0%, N
i; 0.60% or less, Al; 2.0 to 6.0%, Mo;
A stainless steel wire and fiber characterized by a component comprising 0.5 to 1.5%, the balance being Fe and unavoidable impurities.
Hereinafter, the components of the present invention and the contents thereof will be described.

[0008] With regard to the influence of C on the corrosion resistance, as the C content increases, the oxidation resistance decreases and abnormal oxidation tends to occur. In addition, an increase in the C content in a high Al-containing ferritic stainless steel greatly deteriorates the toughness of a slab or a hot coil in a material production stage, and also lowers the workability in a cold state. Therefore, in the present invention, C
The upper limit of the content was set to 0.10% by weight.

[0009] Si is an element that significantly improves the oxidation resistance of ferritic stainless steel at high temperatures. To obtain the effect, it is necessary to add 0.3% by weight or more.
On the other hand, excessive Si addition significantly reduces the cold workability of steel. The stainless steel wire according to the present invention is usually produced by cold drawing, but if the Si content exceeds 1.5% by weight, the toughness of the matrix is reduced and SiO
_{The number of 2} system inclusions increases, and the frequency of breakage during wire drawing due to a decrease in toughness as a steel wire significantly increases. Therefore,
The Si content was in the range of 0.3 to 1.5% by weight.

Mn is an effective element for improving hot workability at high temperatures, but the upper limit of the Mn content is set to 1.0% by weight or less for the same reason as that of C. Cr is a basic element necessary for securing oxidation resistance and corrosion resistance at high temperatures,
In order to exert the effect, it is necessary to add 17.0% by weight or more of Cr. However, if the Cr content is too large, it becomes particularly sensitive to σ brittleness and 475 ° C. brittleness, and the manufacturability is remarkably reduced due to the deterioration of the toughness of the slab and the hot coil and the reduction of the cold workability in the material production stage. Therefore, the Cr content is set in the range of 17.0 to 26.0% by weight.

Ni not only causes instability of the ferrite structure, but an excessive addition adversely affects the oxidation resistance at high temperatures. In particular, in the stainless steel according to the invention, N
When the content of i exceeds 0.60% by weight, 800 to 900
It has been found that the oxidation resistance in the temperature range of ° C. is significantly reduced. Therefore, the content of Ni is set to 0.60% by weight or less.

Al, like Cr, is an important element for improving corrosion resistance, and when added, Al ₂ O ₃ is formed on the steel surface to obtain excellent corrosion resistance. However, if the content is less than 2.0% by weight, the effect is insufficient. On the other hand, as the content increases, the toughness rapidly decreases. Manufacturability deteriorates due to a decrease in workability. Therefore, in the present invention, the Al content is set in the range of 2.0 to 6.0% by weight.

Mo, like Al, is an important element for improving corrosion resistance, and is also an element for improving high-temperature strength. To achieve this effect, at least 0.5
Although the addition of Mo by weight% or more is necessary, the addition of a large amount not only causes deterioration of the toughness of the steel, but also unnecessarily increases the raw material cost. Therefore, the Mo content is 0.5
１．５1.5% by weight.

Although these components can be sufficiently provided for those which can be formed by relatively easy processing, members which require more workability at the time of forming can be processed without impairing the heat resistance. It has been found that in order to further improve the properties, the amount of each element added is further limited to an appropriate range, thereby exhibiting a very excellent effect. That is, the second steel of the present invention is different from the first steel according to the first invention.
Further, the content of Cr is 0.08% or less and the content of Si is 0.1% by weight.
3 to 1.0%, the Mn content is 1.0% or less, and the Cr content is 18.
By limiting the amount of Ni to 0.60% or less, the amount of Al to 3.0 to 4.0%, and the amount of Mo to 0.7 to 1.3% without impairing the heat resistance. Further, the workability can be improved.

The stainless steel wire and fiber of the present invention having excellent high-temperature oxidation resistance and heat deformation resistance have the above-mentioned composition.
The steel wire and the fiber may be long fibers or short fibers. The diameter of the steel wire is usually about 0.1 to 1 mmφ. Steel wire and fiber are usually cold drawn to a diameter of 5 mm or less, and then processed to a smaller diameter. Further, a bar-shaped steel material can be made into a fiber by cutting. The diameter of the fiber is about 0.01 to 0.5 mm.

The stainless steel wire and fiber of the present invention can be used for exhaust parts for automobiles, especially for parts that come into direct contact with exhaust gas. Specifically, it can be used as a stainless steel wire for an inner blade of a flexible tube provided between an exhaust manifold of an automobile exhaust system and an exhaust gas catalyst. As shown in FIG. 1, the cross section of the flexible tube is composed of three layers of an inner blade assembly 1, a bellows tube 2, and an outer blade 3 from the inside, and both ends are coaxially laminated. And are integrally fixed. The inner blade assembly 1 is composed of two short cylindrical inner pipes 11 forming both ends.
The inner end of each inner pipe 11 is inserted into each of the inner pipes 11, and the stainless steel wire of the present invention is knitted into a cylindrical inner blade 12 and each end of the inner blade 12 is connected to each inner pipe 11. It comprises two inner rings 13 to be clamped. In addition, the inner pipe 11,
The inner blade 12 and the inner ring 13 are integrally joined by spot welding at a portion where the three members are coaxially stacked.

The bellows tube 2 is formed in a tubular shape with both end portions having a short cylindrical shape, and has a bellows-shaped central portion in which a small-diameter portion and a large-diameter portion alternate in the axial direction. Usually, this bellows tube 2 is formed of austenitic stainless steel. The outer blade 3 covers the bellows tube 2 and protects it mechanically, and is usually a tubular body woven from austenitic stainless steel fiber.

The stainless steel wire and fiber of the present invention can be optimally used for the inner tube 12 of this flexible tube. In addition, the stainless steel wire and fiber of the present invention can be used for a noise-reducing component provided in an exhaust passage in which exhaust gas flows, in addition to the inner blade 12. This sound-absorbing part is a fiber integrated body in which the stainless steel wire and the fiber of the present invention are accumulated, and when the sound wave passes through a gap formed between adjacent fibers, the sound waves are dispersed and interfere with each other to muffle the sound. You.

The stainless steel wire and fiber of the present invention can be optimally used for a wire mesh for holding a ceramic catalyst, a heating appliance, an electric heating material (heating element) and the like.

[0020]

【Example】

(Example 1) A stainless steel having the composition shown in No. 1 was melted and hot-rolled to a diameter of 5.5 mm, and thereafter, refining and cold drawing were repeated to produce a wire having a diameter of 0.4 mm (inventive steel). In addition, as a comparative material, No. 1 in Table 1 was used. 2, No.
3, No. A line having a diameter of 0.4 mm of the component shown in FIG. 4 was manufactured in the same process. No. No. 2 is an Fe-Cr-Al alloy obtained by adding Al to ferritic stainless steel; 3, N
o. No. 4 is currently used for a flexible tube braider. No. 3 is a ferritic stainless steel obtained by adding Mo to SUS430. 4 is austenitic stainless steel SUS304.

These are treated at 800 ° C., 900 ° C.
Under three conditions of 1000 ° C., a cycle of heating for 20 hours and then cooling for 4 hours was repeated 10 times, and the rate of mass increase due to oxidation was determined. In addition, after processing into the shape of an inner blade of a flexible tube of an exhaust system part for an automobile, and holding at 900 ° C. for 5 minutes in an exhaust gas atmosphere, 1000 cycles of a cooling / heating cycle test of holding at 100 ° C. or lower for 5 minutes were performed. The shape change of the test material after the test was examined. Table 1 shows the results.

[0022]

[Table 1]

No. 2 having a chemical component to which Al was added. 1,
No. The line of No. 2 is No. 3, No. The oxidation was less at any temperature than the line of No. 4, and No. 4 in which Mo was added in addition to Al. The line of No. 1 (material of the present invention) is No. 1. The oxidation is further reduced in the temperature range of 800 ° C. and 900 ° C. as compared with the line No. 2. In the cooling / heating cycle test, any of the comparative materials was deformed in shape.
No. added with The wire No. 1 (material of the present invention) is not deformed and has excellent heat deformation resistance. (Embodiment 2) The stainless steel shown in No. 5 was melted, hot-rolled to a diameter of 5.5 mm, then sintered, and a wire having a diameter of 3.0 mm was produced by cold drawing. Further, a metal fiber having an average thickness of about 0.075 mm was produced by a wire cutting method of cutting the surface of the wire with a cutting tool while running the wire (material of the present invention). In addition, the average thickness is obtained by measuring and averaging 50 major diameters of the fiber because the cross-sectional shape of the fiber is half-moon-shaped. In addition, as a comparative material,
o. No. 6 is a Fe-Cr-Al alloy wire, 7 is S
No. US430 was obtained by wire cutting from a ferritic steel wire with Mo added. This is a metal fiber manufactured to a size equivalent to 5. These are heated at 700 ° C. and 800
A cycle of heating for 20 hours and then cooling for 4 hours was repeated 10 times under four conditions of ° C, 900 ° C, and 1000 ° C, and the mass increase rate due to oxidation was determined. Table 2 shows the results.

[0024]

[Table 2]

Since the sample is thinner and has a larger surface area per unit mass as compared with the wire rod of Example 1, the rate of mass increase due to oxidation of the surface is larger than that of Example 1. Similarly, it can be seen that the material of the present invention (No. 5) is less oxidized in the temperature range of 800 ° C. and 900 ° C. than the others. (Example 3) No. 3 in Table 3 8, no. A stainless steel having the composition shown in No. 9 was melted and hot-rolled to a diameter of 5.5 mm, and thereafter, refining and cold drawing were repeated to produce a wire having a diameter of 1.0 mm (material of the present invention). In addition, as a comparative material,
o. 10, No. 11, No. A wire having a diameter of 1.0 mm and a component shown in FIG. After the five types of 1.0 mm wires were refined, they were each cold-drawn to a diameter of 0.4 mm using a 9-die continuous wire drawing machine, and the number of wire breaks during processing per 1 ton of processed amount was determined. Table 3 shows the results.

[0026]

[Table 3] Inventive material No. 8, no. 9 is the currently used S
No. US430 containing ferritic stainless steel No. Although the number of disconnections can be considered to be equivalent to 10, the number of Si added is large in No. 10. 11. N with a large amount of Al added
o. In No. 12, it can be seen that the number of disconnections is large, and that cold wire drawing workability is deteriorated due to the addition of excessive Si or Al.

[0027]

According to the present invention, by optimizing the amounts of Mo, Al, and Si added to a high Al-containing ferritic stainless steel wire and fiber, 800-800 can be obtained without impairing the cold drawability in the material production stage. It has been found that oxidation resistance and heat deformation resistance in a temperature range of 900 ° C. can be further improved.

Therefore, by using the material of the present invention for the heat-resistant stainless steel wire and the stainless steel fiber used for the exhaust system parts for automobiles, the durability reliability of the exhaust system parts can be improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of a flexible tube having an inner blade made of stainless steel wire and fiber of the present invention. DESCRIPTION OF SYMBOLS 1 ... Inner blade assembly 2 ... Bellows tube 3 ... Outer blade 12 ... Inner blade

Continuation of front page (72) Inventor Yoshio Yoshimura 1-1-1, Koyokita, Itami-shi, Itami-shi, Hyogo Itami Works, Sumitomo Electric Industries, Ltd. (56) References JP-A-8-20847 (JP, A) JP-A-7-207462 (JP, A) JP-A-6-1288693 (JP, A) JP-A-4-354850 (JP, A) JP-A-2-243743 (JP, A) JP-A-63-317561 (JP) JP-A-48-102022 (JP, A) JP-A-10-1751 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00-38/60

Claims (5)

(57) [Claims] (1) C: 0.10% or less by weight, Si:
16. 0.3 to 1.5%, Mn; 1.0% or less, Cr;
0-26.0%, Ni; 0.60% or less, Al; 2.0
0.5% to 1.5%, Mo: 0.5% to 1.5%, with the balance being Fe and unavoidable impurities, stainless steel wires and fibers excellent in high-temperature oxidation resistance and heat deformation resistance. 2. C: 0.08% or less, Si: 0.3-1.
0%, Cr; 18.0 to 21.0% Al;
2. The stainless steel wire and fiber according to claim 1, which has a high-temperature oxidation resistance and a heat-resistant deformation resistance of 4.0%, Mo: 0.7 to 1.3%. 3. An exhaust system for an automobile, wherein the exhaust system is used for an inner blade in a flexible tube.
The stainless steel wire described in. 4. The stainless steel wire and fiber according to claim 1, which is used as a sound absorbing material in a muffler of an exhaust system part for an automobile. 5. The stainless steel wire and fiber according to claim 4, wherein the metal fiber is a metal fiber produced by cutting.