JP2021147689A - Ferritic stainless steel material and method for producing the same, and vibration damping member - Google Patents

Abstract

To provide a ferritic stainless steel material that has excellent toughness and vibration damping property.SOLUTION: A ferritic stainless steel material has a composition containing C: 0.05 mass% or less, Mn: 2.0 mass% or less, Ni: 0.60 mass% or less, P: 0.05 mass% or less, S: 0.03 mass% or less, Cr: 10.0 to 24.0 mass%, N: 0.03 mass% or less, Cu: 0.60 mass% or less, Mo: 2.5 mass% or less, Si: 1.0 mass% or less, Al: 0.5 mass% or less, Nb: 0.50 mass% or less, Ti: 0.50 mass% or less, the total contained amount of Nb and Ti being 6(C+N) mass% or more (C and N represent the contained amounts of C and N, respectively), and the balance composed of Fe and impurities. This ferritic stainless steel material has a number density of precipitates having an average crystal grain size of 100 to 500 μm and a major axis of 5 μm or more of 5 pieces/mm2 or less.SELECTED DRAWING: None

Description

The present invention relates to a ferritic stainless steel material, a method for producing the same, and a vibration damping member.

With the electrification of automobiles, the noise and vibration caused by the engine are reduced, and the quietness of the passenger compartment is improved. As a result, noise that has been buried in engine noise and high-frequency noise that is peculiar to electrification are more likely to be perceived by passengers as abnormal noise, and are used in automobiles (especially exhaust gas members such as mufflers). The level of vibration damping for the material is high.

Further, in recent years, electronic devices such as hard disks (hereinafter, abbreviated as "HDD") have increased the amount of heat generated per unit volume as the capacity has increased. In particular, in places such as data centers where a large number of HDDs are densely installed, the amount of heat generated is large, so cooling is performed using a high-output fan. However, in a high output fan, the resonance of the hard disk is likely to occur due to the vibration caused by the wind pressure. In electronic devices such as HDDs, vibration causes malfunctions and failures, so that materials used in electronic devices are also required to have high vibration damping properties.

Rubber and resin are typical examples of materials having vibration damping properties, but it is often difficult to use them for the above-mentioned applications from the viewpoint of strength and heat dissipation. Therefore, there is a demand for a metal material having vibration damping properties that can be used for the above-mentioned applications.
The metal material having vibration damping properties is roughly classified into a composite type, a ferromagnetic type, a dislocation type and a twin type according to the damping mechanism of vibration energy. Among them, the ferritic stainless steel material is a ferromagnet and has a ferromagnetic damping mechanism. In the ferromagnetic type, the magnetic domains are rearranged in one direction when an external force such as vibration is applied, and the magnetic domains are randomly rearranged when the load is removed. The residual strain at this time absorbs the vibration energy and attenuates the vibration.

As the ferrite-based stainless steel material having excellent vibration damping properties, C: 0.001 to 0.03% by mass, Si: 0.1 to 1.0% by mass, Mn: 0.1 to 2.0% by mass, Ni: 0.01 to 0.6% by mass, Cr: 10.5 to 24.0% by mass, N: 0.001 to 0.03% by mass, Nb: 0 to 0.8% by mass, Ti: 0 to 0. 5% by mass, Cu: 0 to 2.0% by mass, Mo: 0 to 2.5% by mass, V: 0 to 1.0% by mass, Al: 0 to 0.3% by mass, Zr: 0 to 0. The matrix has a chemical composition of 3% by mass, Co: 0 to 0.6% by mass, REM: 0 to 0.1% by mass, Ca: 0 to 0.1% by mass, the balance Fe and unavoidable impurities. A vibration-damping ferrite-based stainless steel material which is a ferrite single phase, has a metal structure in which the average crystal grain size of ferrite crystal grains is 0.3 to 3.0 mm, and has a residual magnetic flux density of 45 mT or less has been proposed. (Patent Document 1). In this ferritic stainless steel material, the crystal grains are coarsened in order to ensure vibration damping properties, and examples are shown in which the average crystal grain size of the crystal grains is increased to 1.52 mm and 0.94 mm. ing.

JP-A-2017-39955

Most of the ferritic stainless steel materials used for exhaust gas members such as automobile mufflers have a thickness of 1.0 mm or less, and ferritic stainless steel materials having a thickness of about 0.5 mm may be used. Further, many ferrite-based stainless steel materials used in electronic devices such as HDDs have a thickness of 1.0 mm or less, and ferrite-based stainless steel materials having a thickness of about 0.2 mm are often used. When the crystal grains are coarsened as in Patent Document 1 for such a ferritic stainless steel material having a small thickness, there are many places where only one crystal grain exists in the thickness direction, and the toughness There is a problem that

The present invention has been made to solve the above problems, and an object of the present invention is to provide a ferritic stainless steel material having excellent toughness and vibration damping properties, a method for producing the same, and a vibration damping member.

As a result of diligent research to solve the above problems, the present inventors have controlled the composition of the ferritic stainless steel material, the average crystal grain size, and the number density of precipitates having a major axis of 5 μm or more. , It has been found that the vibration damping property can be improved while suppressing the decrease in toughness, and the present invention has been completed.

That is, in the present invention, C: 0.05% by mass or less, Mn: 2.0% by mass or less, Ni: 0.60% by mass or less, P: 0.05% by mass or less, S: 0.03% by mass or less. , Cr: 10.0 to 24.0% by mass, N: 0.03% by mass or less, Cu: 0.60% by mass or less, Mo: 2.5% by mass or less, Si: 1.0% by mass or less, Al : 0.5% by mass or less, Nb: 0.50% by mass or less, Ti: 0.50% by mass or less, and the total content of Nb and Ti is 6 (C + N) mass% or more (C and N are C). And N content, respectively), and the balance has a composition of Fe and impurities.
It is a ferritic stainless steel material having an average crystal grain size of 100 to 500 μm and a number density of precipitates having a major axis of 5 μm or more and 5 pieces / mm ^{2 or less.}

Further, in the present invention, C: 0.05% by mass or less, Mn: 2.0% by mass or less, Ni: 0.60% by mass or less, P: 0.05% by mass or less, S: 0.03% by mass or less. , Cr: 10.0 to 24.0% by mass, N: 0.03% by mass or less, Cu: 0.60% by mass or less, Mo: 2.5% by mass or less, Si: 1.0% by mass or less, Al : 0.5% by mass or less, Nb: 0.50% by mass or less, Ti: 0.50% by mass or less, and the total content of Nb and Ti is 6 (C + N) mass% or more (C and N are C). And N content respectively), and after heating a stainless steel plate having a composition of Fe and impurities in the balance at 950 to 1200 ° C. for 10 to 120 minutes, the cooling rate to 700 ° C. is 20 ° C./min or more. This is a method for producing a ferrite-based stainless steel material, which cools at a cooling rate of 30 ° C./min or more from 700 ° C. to 400 ° C.

Further, the present invention is a vibration damping member containing the above-mentioned ferritic stainless steel material.

According to the present invention, it is possible to provide a ferrite-based stainless steel material having excellent toughness and vibration damping properties, a method for producing the same, and a vibration damping member.

It is the top view and the side view of the adhesive body used for the corrosion resistance test.

Hereinafter, embodiments of the present invention will be specifically described. The present invention is not limited to the following embodiments, and changes, improvements, etc. have been appropriately added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that things also fall within the scope of the present invention.

The ferrite-based stainless steel material according to the embodiment of the present invention has C: 0.05% by mass or less, Mn: 2.0% by mass or less, Ni: 0.60% by mass or less, P: 0.05% by mass or less, S. : 0.03% by mass or less, Cr: 10.0 to 24.0% by mass, N: 0.03% by mass or less, Cu: 0.60% by mass or less, Mo: 2.5% by mass or less, Si: 1 .0 mass% or less, Al: 0.5 mass% or less, Nb: 0.50 mass% or less, Ti: 0.50 mass% or less, and the total content of Nb and Ti is 6 (C + N) mass% or more. (C and N represent the contents of C and N, respectively), and the balance has a composition of Fe and impurities.
Here, the term "impurity" as used herein refers to a component mixed with raw materials such as ore and scrap, and various factors in the manufacturing process when industrially manufacturing a ferritic stainless steel material, and is defined in the present invention. It means something that is acceptable as long as it does not adversely affect it. For example, impurities also include unavoidable impurities.

Further, the ferritic stainless steel material according to the embodiment of the present invention has Zr: 1.0% by mass or less, Co: 1.0% by mass or less, V: 1.0% by mass or less, and W: 1.0% by mass or less. It may further contain at least one selected from.
Further, the ferrite-based stainless steel material according to the embodiment of the present invention may further contain at least one selected from REM: 0.10% by mass or less and Ca: 0.10% by mass or less.
Further, the ferrite-based stainless steel material according to the embodiment of the present invention may further contain at least one selected from Sn: 0.10% by mass or less and B: 0.01% by mass or less.

(C: 0.05% by mass or less)
C is an element that affects the properties such as intergranular corrosion resistance (sensitization suppressing action) and workability of ferritic stainless steel materials. If the C content is too large, the processability and intergranular corrosion resistance of the ferritic stainless steel material will deteriorate. Therefore, the upper limit of the C content is 0.05% by mass, preferably 0.045% by mass, and more preferably 0.04% by mass. On the other hand, the lower limit of the C content is not particularly limited, but reducing the C content leads to an increase in the refining cost. Therefore, the lower limit of the C content is preferably 0.0005% by mass, preferably 0.001% by mass.

(Mn: 2.0% by mass or less)
Mn is a useful element as a deoxidizing element. If the Mn content is too large, MnS, which is the starting point of corrosion, is likely to be generated, and the ferrite phase is destabilized. Therefore, the upper limit of the Mn content is 2.0% by mass, preferably 1.9% by mass, and more preferably 1.8% by mass. On the other hand, the lower limit of the Mn content is not particularly limited, but is preferably 0.01% by mass, more preferably 0.05% by mass.

(Ni: 0.60% by mass or less)
Ni is an element effective for improving the corrosion resistance and toughness of ferritic stainless steel materials. If the Ni content is too high, the ferrite phase becomes unstable and the manufacturing cost increases. Therefore, the upper limit of the Ni content is 0.60% by mass, preferably 0.58% by mass, and more preferably 0.55% by mass. On the other hand, the lower limit of the Ni content is not particularly limited, but is preferably 0.01% by mass, more preferably 0.05% by mass from the viewpoint of obtaining the above effects.

(P: 0.05% by mass or less)
P is an element that affects the properties such as weldability and workability of ferritic stainless steel materials. If the content of P is too high, the above characteristics may be deteriorated. Therefore, the upper limit of the P content is 0.05% by mass, preferably 0.045% by mass, and more preferably 0.04% by mass. On the other hand, the lower limit of the P content is not particularly limited, but reducing the P content leads to an increase in the refining cost. Therefore, the lower limit of the P content is preferably 0.001% by mass, more preferably 0.01% by mass.

(S: 0.03% by mass or less)
S is an element that produces MnS, which is the starting point of corrosion, and affects the toughness and other characteristics of ferritic stainless steel. If the S content is too high, the above characteristics may deteriorate. Therefore, the upper limit of the S content is 0.03% by mass, preferably 0.025% by mass, and more preferably 0.02% by mass. On the other hand, the lower limit of the S content is not particularly limited, but reducing the S content leads to an increase in the refining cost. Therefore, the lower limit of the S content is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more.

(Cr: 10.0 to 24.0% by mass)
Cr is an element effective for improving the corrosion resistance and oxidation resistance of ferritic stainless steel materials. If the Cr content is too high, the toughness of the ferritic stainless steel material will decrease, and the manufacturing cost will increase. Therefore, the upper limit of the Cr content is 24.0% by mass, preferably 23.5% by mass, and more preferably 23.0% by mass. On the other hand, if the Cr content is too small, the above effect may not be sufficiently obtained. Therefore, the lower limit of the Cr content is 10.0% by mass, preferably 10.5% by mass. In particular, by setting the Cr content to 16% by mass or more, the corrosion resistance of the ferritic stainless steel material can be effectively improved.

(N: 0.03% by mass or less)
N is an element that affects properties such as intergranular corrosion resistance (sensitization inhibitory action) and workability. If the N content is too large, the processability and intergranular corrosion resistance of the ferritic stainless steel material will deteriorate. Therefore, the upper limit of the N content is 0.03% by mass, preferably 0.028% by mass, and more preferably 0.025% by mass. On the other hand, the lower limit of the N content is not particularly limited, but reducing the N content leads to an increase in the refining cost. Therefore, the lower limit of the N content is preferably 0.0005% by mass, preferably 0.001% by mass.

(Cu: 0.60% by mass or less)
Cu is an element effective for improving the corrosion resistance of ferritic stainless steel materials. If the Cu content is too high, the ferrite phase becomes unstable and the manufacturing cost increases. Therefore, the upper limit of the Cu content is 0.60% by mass, preferably 0.55% by mass, and more preferably 0.50% by mass. On the other hand, the lower limit of the Cu content is not particularly limited, but is preferably 0.001% by mass, preferably 0.01% by mass.

(Mo: 2.5% by mass or less)
Mo is an element effective for improving the corrosion resistance and oxidation resistance of ferritic stainless steel materials. If the Mo content is too high, the processability of the ferritic stainless steel material will decrease and the manufacturing cost will increase. Therefore, the upper limit of the Mo content is 2.5% by mass, preferably 2.3% by mass, and more preferably 2.0% by mass. On the other hand, the lower limit of the Mo content is not particularly limited, but is preferably 0.001% by mass, preferably 0.01% by mass.

(Si: 1.0% by mass or less)
Si is an element that improves the scale peeling resistance and high temperature oxidation resistance of ferritic stainless steel materials. If the Si content is too high, workability and toughness will decrease. Therefore, the upper limit of the Si content is 1.0% by mass, preferably 0.9% by mass, and more preferably 0.8% by mass. On the other hand, the lower limit of the Si content is not particularly limited, but is preferably 0.05% by mass, more preferably 0.10% by mass, from the viewpoint of suppressing deterioration of surface quality due to scale peeling during the production of ferritic stainless steel. %, More preferably 0.15% by mass.

(Al: 0.5% by mass or less)
Al is an element that improves oxidation resistance by forming a dense protective oxide film on the surface of a ferritic stainless steel material. If the Al content is too high, the toughness of the ferritic stainless steel material will decrease. Therefore, the upper limit of the Al content is 0.5% by mass, preferably 0.45% by mass, and more preferably 0.40% by mass. On the other hand, the lower limit of the Al content is not particularly limited, but is preferably 0.001% by mass, preferably 0.01% by mass.

(Nb: 0.50% by mass or less, Ti: 0.50% by mass or less, total content of Nb and Ti: 6 (C + N) mass% or more)
Nb and Ti are elements that affect properties such as intergranular corrosion resistance (sensitization inhibitory action).
If the Nb content is too high, the processability and toughness of the ferritic stainless steel material will decrease. Therefore, the upper limit of the Nb content is 0.50% by mass, preferably 0.48% by mass, and more preferably 0.45% by mass.
Further, if the Ti content is too large, the processability and surface quality of the ferritic stainless steel material deteriorate. Therefore, the upper limit of the Ti content is 0.50% by mass, preferably 0.48% by mass, and more preferably 0.45% by mass.
On the other hand, the lower limit of the contents of Nb and Ti is controlled from the relationship with the contents of C and N, which lower the intergranular corrosion resistance. Specifically, the lower limit of the total content of Nb and Ti is 6 (C + N) mass%, preferably 7 (C + N) mass%. Here, C and N represent the contents of C and N, respectively.

(Zr: 1.0% by mass or less, Co: 1.0% by mass or less, V: 1.0% by mass or less, W: 1.0% by mass or less)
Zr, Co, V and W are elements effective for improving the oxidation resistance of ferritic stainless steel materials. If the contents of Zr, Co, V and W are too large, the processability and toughness of the ferritic stainless steel material will decrease, and the manufacturing cost will increase. Therefore, the upper limit of the contents of Zr, Co, V and W is 1.0% by mass, preferably 0.8% by mass, and more preferably 0.5% by mass. On the other hand, the lower limit of the contents of Zr, Co, V and W is not particularly limited, but is preferably 0.001% by mass, more preferably 0.01% by mass.

(REM: 0.10% by mass or less, Ca: 0.10% by mass or less)
REM and Ca are elements effective for improving the oxidation resistance of ferritic stainless steel materials. If the contents of REM and Ca are too high, the production cost of ferritic stainless steel will increase. Therefore, the upper limit of the contents of REM and Ca is 0.10% by mass, preferably 0.08% by mass, and more preferably 0.05% by mass. On the other hand, the lower limit values of REM and Ca are not particularly limited, but are preferably 0.0001% by mass, more preferably 0.003% by mass.

(Sn: 0.10% by mass or less)
Sn is an element effective for improving the corrosion resistance of ferritic stainless steel materials. If the Sn content is too high, Sn will segregate and the manufacturability will decrease. Therefore, the upper limit of the Sn content is 0.10% by mass, preferably 0.08% by mass, and more preferably 0.05% by mass. On the other hand, the lower limit of the Sn content is not particularly limited, but is preferably 0.001% by mass, more preferably 0.005% by mass.

(B: 0.01% by mass or less)
B is an element effective for improving the secondary workability of the ferritic stainless steel material. If the B content is too high, the fatigue strength of the ferritic stainless steel will decrease. Therefore, the upper limit of the content of B is 0.01% by mass, preferably 0.008% by mass, and more preferably 0.005% by mass. On the other hand, the lower limit of the content of B is not particularly limited, but is preferably 0.0001% by mass, more preferably 0.0005% by mass.

The ferrite-based stainless steel material according to the embodiment of the present invention has an average crystal grain size of 100 to 500 μm, preferably 110 to 400 μm, and more preferably 120 μm or more and less than 300 μm. By setting the average crystal grain size to 100 μm or more, it is possible to reduce the grain boundaries that hinder the movement of magnetic domains that are effective for the development of vibration damping properties, so that the vibration damping properties are improved. Further, by setting the average crystal grain size to 500 μm or less, it is possible to suppress a decrease in toughness due to extreme coarsening of the crystal grains.
Here, the average crystal grain size in the present specification means what is measured using an optical microscope described later.

The ferrite stainless steel material according to the embodiment of the present invention has a number density of deposits having a major axis of 5 μm or more of 5 pieces / mm ² or less, preferably 4 pieces / mm ² or less, and more preferably 3 pieces / mm ² or less. be.
Precipitates having a major axis of 5 μm or more in a ferritic stainless steel material hinder the movement of magnetic domains as well as grain boundaries. Therefore, the vibration damping property can be improved by controlling the number density of precipitates having a major axis of 5 μm or more within the above range.
Further, since the crystal grain boundary is small in the structure in which the crystal grains are coarsened, stress is concentrated around the precipitate when an impact is applied, and it is easy to function as a crack starting point or a propagation path. Therefore, the amount of precipitates in the ferritic stainless steel material greatly affects the toughness. In particular, among the precipitates, the carbides of Ti, Nb and Cr are larger than the oxides formed during melting, and therefore have a large effect on toughness. In addition, Cr carbides cause sensitization of ferritic stainless steel materials, which also causes a decrease in corrosion resistance. Therefore, by controlling the number density of precipitates having a major axis of 5 μm or more within the above range, it is possible to suppress the above-mentioned decrease in toughness and corrosion resistance.
Here, in the present specification, the number density of precipitates having a major axis of 5 μm or more means those measured by using an SEM (scanning electron microscope) described later. However, the number density of precipitates having a major axis of 5 μm or more may be measured using an existing measuring device such as an automatic precipitate measuring device.

The ferrite-based stainless steel material according to the embodiment of the present invention has a loss coefficient η of preferably 5 × 10 ^-4 or more, more preferably 5.3 × 10 ^-4 or more, and further preferably 5.5 × 10 ^-4 or more. Is. By setting the loss coefficient η in such a range, the desired vibration damping property can be ensured.
The upper limit of the loss coefficient η is not particularly limited, but is generally 20 × 10 ^-4 , preferably 15 × 10 ^-4 .
Here, the loss coefficient η in the present specification means what is measured by the “central excitation method” described later.

The ferrite-based stainless steel material according to the embodiment of the present invention has an absorption energy of Charpy impact test at 0 ° C. (hereinafter referred to as “Charpy impact value”) of preferably 20 J / cm ² or more, more preferably 25 J / cm ² or more. Is. By setting the Charpy impact value in such a range, the desired toughness can be ensured.
The upper limit of the Charpy impact value is not particularly limited, generally 300 J / cm ^2, preferably 200 J / cm ^2.
Here, the Charpy impact value in the present specification means a value measured by a method described later.

The thickness of the ferritic stainless steel material according to the embodiment of the present invention is not particularly limited, but is preferably 1.0 mm or less.
In a structure in which the crystal grains are coarsened, the toughness tends to decrease when the thickness of the ferritic stainless steel material is 1.0 mm or less, but the ferritic stainless steel material according to the embodiment of the present invention has a thickness of 1.0 mm or less. Even so, toughness can be ensured.
The lower limit of the thickness of the ferritic stainless steel material according to the embodiment of the present invention is not particularly limited, but is preferably twice or more, preferably three times or more the average crystal grain size.

The ferrite-based stainless steel material according to the embodiment of the present invention can be produced by using a stainless steel plate having the above composition according to a method known in the art. For example, in the ferritic stainless steel material according to the embodiment of the present invention, a stainless steel sheet having the above composition is heated at 950 to 1200 ° C. for 10 to 120 minutes, and then cooled to 700 ° C. at a cooling rate of 20 ° C./min or more, 700. It can be produced by cooling at a cooling rate of 30 ° C./min or higher from ° C. to 400 ° C.

Here, the stainless steel sheet having the above composition can be produced by a conventional method. Specifically, first, stainless steel having the above composition is melted, forged or cast, and then hot-rolled to obtain a hot-rolled plate. Next, the hot-rolled plate is annealed, pickled, and cold-rolled in that order to obtain a cold-rolled plate. Next, the cold-rolled plate is annealed and pickled in sequence to obtain a cold-rolled annealed plate. The conditions in each step may be appropriately adjusted according to the composition of the stainless steel and the like, and are not particularly limited. A hot-rolled plate, a cold-rolled plate, or a cold-rolled annealed plate produced by such a method can be used as a stainless steel plate. Among them, the stainless steel sheet is preferably a cold-spread annealed sheet.

The stainless steel sheet may be processed into a predetermined member before the heat treatment (recrystallization treatment), or may be heat-treated in the form of a plate or a coil. Examples of the processing method include various press processing using a die, bending processing, welding processing, and the like.

The heat treatment (recrystallization treatment) of the stainless steel sheet is performed by heating at 950 to 1200 ° C. for 10 to 120 minutes. By performing the heat treatment under such conditions, the crystal grains can be grown so that the average crystal grain size is 100 to 500 μm. Here, the atmosphere of the heat treatment may be an atmospheric atmosphere, a non-oxidizing atmosphere, or the like.

For cooling after the heat treatment (recrystallization treatment), the cooling rate from the heat treatment temperature (950 to 1200 ° C.) to 700 ° C. is 20 ° C./min or more, and the cooling rate from 700 ° C. to 400 ° C. is 30 ° C./min. This is done by cooling as described above.
Since the temperature range from the heat treatment temperature to 700 ° C. is the temperature range in which Ti and Nb carbides are precipitated, the cooling rate in this temperature range is 20 ° C./min or more, preferably 22 ° C./min or more, more preferably. By setting the temperature to 25 ° C./min or higher, precipitation of Ti and Nb carbides can be effectively suppressed. The upper limit of the cooling rate in this temperature range is not particularly limited, but is generally 300 ° C./min or less, preferably 250 ° C./min or less, and more preferably 200 ° C./min or less.
Further, since the temperature range from 700 ° C. to 400 ° C. is the temperature range in which Cr carbides are precipitated, the cooling rate in this temperature range is 30 ° C./min or more, preferably 32 ° C./min or more, more preferably 35 ° C. By setting the temperature to / min or more, precipitation of Cr carbide can be effectively suppressed. The upper limit of the cooling rate in this temperature range is not particularly limited, but is generally 300 ° C./min or less, preferably 250 ° C./min or less, and more preferably 200 ° C./min or less.
Therefore, by cooling under the above conditions, the amount of precipitates (Ti carbides, Nb carbides and Cr carbides) deposited in the stainless steel plate can be reduced (that is, precipitates having a major axis of 5 μm or more). Since the number density of 5 pieces / mm ² or less can be controlled), a ferritic stainless steel material having excellent toughness can be obtained.

In the ferritic stainless steel material according to the embodiment of the present invention, the composition, the average crystal grain size, and the number density of precipitates having a major axis of 5 μm or more are controlled within a predetermined range, so that the decrease in toughness is suppressed and controlled. The vibration property can be increased. Therefore, this ferritic stainless steel material is suitable for use as a vibration damping member. The vibration damping member is not particularly limited, and examples thereof include various members required to have vibration damping properties in automobiles (particularly, exhaust gas members such as mufflers), electronic devices such as HDDs, and the like.

Hereinafter, the contents of the present invention will be described in detail with reference to examples, but the present invention is not construed as being limited thereto.

(Examples 1 to 8 and Comparative Examples 1 to 11)
A ferritic stainless steel material was produced according to the following procedure.
Stainless steel having the composition shown in Table 1 is melted and hot-rolled to obtain a hot-rolled plate with a thickness of 3.0 mm, which is then annealed at 1050 ° C and pickled to be hot-rolled. An annealed plate was obtained. Next, the hot-rolled annealed sheet is cold-rolled to obtain a cold-rolled sheet having a thickness of 1.0 mm, and then the cold-rolled sheet is finished-annealed at 950 to 1050 ° C. and pickled to obtain the cold-rolled annealed sheet. Obtained. Next, a test piece having a width direction of 100 mm and a rolling direction of 200 mm was cut out from the cold-rolled annealed plate by cutting. Next, the test piece was heat-treated (recrystallized) under the heating conditions shown in Table 2 under a hydrogen atmosphere, and then cooled at the cooling rate shown in Table 2. The cooling rate was adjusted by controlling the amount of nitrogen gas introduced. No heat treatment was performed on Comparative Examples 7 and 8.

The test pieces (ferritic stainless steel materials) obtained above were evaluated as follows.

(Average crystal grain size)
A 10 mm × 10 mm measurement test piece was cut out from the above test piece by cutting, and then resin-filled so that the surface of the plate thickness parallel to the rolling direction and orthogonal to the width direction was the observation surface. Next, the resin-embedded measurement test piece was mirror-treated by wet polishing, and then the metallographic structure exposed by etching with fluorinated nitric acid was observed with an optical microscope. For observation with an optical microscope, a straight line was drawn at an arbitrary position on the optical microscope image, the number of intersections between the straight line and the grain boundary was measured, and the average section length was taken as the crystal grain size in accordance with JIS G0551: 2013. .. The crystal grain size was measured by drawing 20 or more straight lines in a plurality of fields of view, and the average value thereof was taken as the average crystal grain size.

(Number density of precipitates)
A 20 mm × 20 mm measurement test piece was cut out from the above test piece by cutting, and then resin-filled so that a surface orthogonal to the plate thickness direction and parallel to the steel material surface was the observation surface. Next, the resin-filled measurement test piece is roughly polished to about 0.25 mm, which is about a quarter of the plate thickness, until the plate thickness becomes 0.7 mm to 0.8 mm by wet polishing. Mirror processed. ^{For the mirror-treated surface, the number of precipitates with a major axis of 5 μm or more existing in an area of 100 mm 2} is measured using an SEM (scanning electron microscope), and the number density (unit area) of the precipitates with a major axis of 5 μm or more. The number of precipitates having a major axis of 5 μm or more per hit) was calculated.

(Toughness)
A measurement test piece having a width of 10 mm and a length of 55 mm was collected from the above test piece so that the longitudinal direction was perpendicular to the rolling direction, and a V notch (notch angle 45 °, notch depth 2 mm, notch) was formed at the center of the longitudinal direction. Bottom radius (0.25 mm) was applied by cutting. Using this measurement test piece, a Charpy impact test was conducted at a test temperature of 0 ° C. according to JIS Z2242: 2018. In this evaluation, when the absorbed energy (Charpy impact value) of the Charpy impact test per unit area is 20 J / cm ² or more, it is ○ (excellent toughness), ^{and when it is less than 20 J / cm 2} , it is × (insufficient toughness). Was judged.

(Vibration damping)
A measurement test piece having a width direction of 10 mm and a rolling direction of 250 mm was cut out from the above test piece by cutting. Using this measurement test piece, the loss coefficient η was measured according to the “central excitation method” defined in JIS K7391: 2008. Specifically, the test piece with the central portion fixed was vibrated by the impedance head, and the mechanical impedance was derived from the output force signal and acceleration vibration. Then, the loss coefficient η was derived based on the anti-resonance frequency that is the peak of the mechanical impedance and the frequency at which the amplitude drops by 3 dB from the peak. In this evaluation, when the loss coefficient η is 5 × 10 ^-4 or more, it is judged as ○ (excellent damping property), and when the loss coefficient η is ^{less than 5 × 10 -4} , it is judged as × (insufficient damping property). bottom.

(Corrosion resistance)
A measurement test piece having a width direction of 50 mm and a rolling direction of 100 mm was cut out from the above test piece by shearing. The adhesive shown in FIG. 1 was prepared using this measurement test piece as follows. 1 (a) is a top view of the adhesive body, and FIG. 1 (b) is a side view. First, of the four cut end faces of the measurement test piece 10, the cut end faces of three sides excluding one short side were coated with rubber 20 (one-component condensation type RTV rubber KE44 manufactured by Shin-Etsu Silicone Co., Ltd.). .. Next, two 20 mmφ × 10 mm polyethylene tubes 40 were arranged and adhered on a 70 mm × 150 mm bakelite plate 30, and a measurement test piece 10 coated with rubber 20 was adhered thereto. Using the adhesive thus obtained, the corrosion resistance was evaluated according to the composite cycle test specified in JASO M609. Specifically, after installing the adhesive in the composite cycle tester so that the test piece for measurement is at an angle of 75 degrees to the horizontal plane and the uncoated short side is on the lower side, 5% salt spray (5% salt spray) ( 5 cycles were performed with 1 cycle of 35 ° C., 2 hours), drying (60 ° C., 25% RH, 4 hours), and wetting (50 ° C., 95% RH, 2 hours). After the composite cycle test, the adhesive is washed with water and dried to evaluate the rusting rate on the surface of the adhesive according to JIS G0595: 2004, and the rating number (RN) is 7 or more (rust area ratio ≤ 0.41). %) Was evaluated as ◯ (excellent in corrosion resistance), and the rating number (RN) was evaluated as × (insufficient corrosion resistance) when the rating number (RN) was less than 7 (corrosion area ratio> 0.41%).
The results of each of the above evaluations are shown in Table 2.

As shown in Table 2, Examples 1 to 8 in which the composition, the average crystal grain size, and the number density of precipitates having a major axis of 5 μm or more satisfy the predetermined ranges had good toughness and vibration damping properties. In addition, Examples 1 to 7 having a high Cr content (16% by mass or more) also had good corrosion resistance.
On the other hand, in Comparative Example 1, since the cooling rate at the heating temperature (1050 ° C.) to 700 ° C. was too slow, the number density of precipitates (particularly Ti and Nb carbides) having a major axis of 5 μm or more became high, and the toughness and toughness were increased. The damping property was not sufficient.
In Comparative Example 2, since the cooling rate at 700 to 400 ° C. was too slow, the number density of precipitates (particularly Cr carbides) having a major axis of 5 μm or more was high, and the toughness and corrosion resistance were not sufficient.
In Comparative Example 3, the toughness was not sufficient because the average crystal grain size was too large.
In Comparative Example 4, since the cooling rate at the heating temperature (1100 ° C.) to 700 ° C. was too slow, the number density of precipitates (particularly Ti and Nb carbides) having a major axis of 5 μm or more was high, and the toughness was not sufficient. ..
In Comparative Example 5, the Nb content was too high and the cooling rate at the heating temperature (1200 ° C.) to 700 ° C. was too slow, so that the number density of precipitates (particularly Ti and Nb carbides) having a major axis of 5 μm or more was high. It became high and the toughness was not enough.

In Comparative Example 6, since the Nb content was too high and the cooling rate at the heating temperature (1200 ° C.) to 700 ° C. was too slow, the number density of precipitates (particularly Ti and Nb carbides) having a major axis of 5 μm or more was high. The toughness was not sufficient because it was high and the average grain size was too large.
In Comparative Examples 7 and 8, since the heat treatment (recrystallization treatment) was not performed, the average crystal grain size was small and the vibration damping property was not sufficient.
In Comparative Example 9, since the content of C was too high and the total content of Ti and Nb was too small, the number density of precipitates having a major axis of 5 μm or more was high, and all of toughness, vibration damping and corrosion resistance were sufficient. It wasn't.
In Comparative Example 10, the toughness and vibration damping property were not sufficient because the content of Cr was too large.
In Comparative Example 11, the toughness and vibration damping properties were not sufficient because the contents of Cr and Mo were too large.

As can be seen from the above results, according to the present invention, it is possible to provide a ferritic stainless steel material having excellent toughness and vibration damping properties, a method for producing the same, and a vibration damping member.

Claims (14)

C: 0.05% by mass or less, Mn: 2.0% by mass or less, Ni: 0.60% by mass or less, P: 0.05% by mass or less, S: 0.03% by mass or less, Cr: 10.0 ~ 24.0% by mass, N: 0.03% by mass or less, Cu: 0.60% by mass or less, Mo: 2.5% by mass or less, Si: 1.0% by mass or less, Al: 0.5% by mass Hereinafter, Nb: 0.50% by mass or less, Ti: 0.50% by mass or less, and the total content of Nb and Ti is 6 (C + N) mass% or more (C and N are the contents of C and N). Each has a composition in which the balance is composed of Fe and impurities.
A ferritic stainless steel material having an average crystal grain size of 100 to 500 μm and a number density of precipitates having a major axis of 5 μm or more and a density of 5 pieces / mm ^{2 or less.} The first aspect of the present invention further comprises at least one selected from Zr: 1.0% by mass or less, Co: 1.0% by mass or less, V: 1.0% by mass or less, and W: 1.0% by mass or less. The ferritic stainless steel material described. The ferrite-based stainless steel material according to claim 1 or 2, further comprising at least one selected from REM: 0.10% by mass or less and Ca: 0.10% by mass or less. The ferrite-based stainless steel material according to any one of claims 1 to 3, further comprising at least one selected from Sn: 0.10% by mass or less and B: 0.01% by mass or less. The ferrite-based stainless steel material according to any one of claims 1 to 4, wherein the loss coefficient η is 5 × 10 ^{-4 or more.} The ferrite-based stainless steel material according to any one of claims 1 to 5, wherein the Charpy impact value at 0 ° C. is 20 J / cm ^{2 or more.} The ferrite-based stainless steel material according to any one of claims 1 to 6, wherein the average crystal grain size is 100 μm or more and less than 300 μm. The ferrite-based stainless steel material according to any one of claims 1 to 7, which has a thickness of 1.0 mm or less. The ferrite-based stainless steel material according to any one of claims 1 to 8, which is used for a vibration damping member. C: 0.05% by mass or less, Mn: 2.0% by mass or less, Ni: 0.60% by mass or less, P: 0.05% by mass or less, S: 0.03% by mass or less, Cr: 10.0 ~ 24.0% by mass, N: 0.03% by mass or less, Cu: 0.60% by mass or less, Mo: 2.5% by mass or less, Si: 1.0% by mass or less, Al: 0.5% by mass Hereinafter, Nb: 0.50% by mass or less, Ti: 0.50% by mass or less, and the total content of Nb and Ti is 6 (C + N) mass% or more (C and N are the contents of C and N). After heating a stainless steel plate having a composition in which the balance is Fe and impurities for 10 to 120 minutes at 950 to 1200 ° C., the cooling rate to 700 ° C. is 20 ° C./min or more and 700 ° C. to 400 ° C. A method for producing a ferrite-based stainless steel material, which cools the product at a cooling rate of 30 ° C./min or higher. 10. The claim 10 further comprises at least one selected from Zr: 1.0% by mass or less, Co: 1.0% by mass or less, V: 1.0% by mass or less, and W: 1.0% by mass or less. The method for manufacturing a ferritic stainless steel material described above. The method for producing a ferritic stainless steel material according to claim 10 or 11, further comprising at least one selected from REM: 0.10% by mass or less and Ca: 0.10% by mass or less. The method for producing a ferrite-based stainless steel material according to any one of claims 10 to 12, further comprising at least one selected from Sn: 0.10% by mass or less and B: 0.01% by mass or less. A vibration damping member containing the ferrite-based stainless steel material according to any one of claims 1 to 9.

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