JP2024020009A - Ferritic stainless steel material and its manufacturing method, ferritic stainless steel material for vibration damping heat treatment, and vibration damping member - Google Patents

Abstract

To provide a ferritic stainless steel that is superior in vibration-damping properties and surface appearance.SOLUTION: A ferritic stainless steel has an oxide film on the surface of the base material. The base material comprises, in mass, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00-35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50-4.00%, N: 0.100% or less, Nb: 0.20-1.00%, with 1.8Cr+2.8Mo: 40.00% or more, and with the balance being Fe and impurities. The oxide film has a brightness index L* of 70.0 or more in the L*a*b*color system, a chromatic index a* of within ±1.0, a chromatic index b* of within ±5.0, and a 85-degree specular gloss Gs (85°) of 50.0% or more. The ferritic stainless steel has a loss factor η of 4.0×10-4 or more.SELECTED DRAWING: None

Description

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

2. Description of the Related Art As automobiles become more electric, the noise and vibrations generated by engines are becoming smaller, and the interior of the vehicle is becoming quieter. As a result, noise that was previously buried under engine noise and high-frequency sounds unique to electrification are now more easily perceived by passengers as abnormal noises, and the materials used in automobiles have a higher level of vibration damping. It has become. Furthermore, parts such as sliding door rails are required to have vibration damping properties in order to suppress vibrations caused by opening and closing doors.

Furthermore, in recent years, as electronic devices such as hard disks (hereinafter abbreviated as "HDD") have become larger in capacity, the amount of heat generated per unit volume has increased. Particularly, in places such as data centers where a large number of HDDs are installed closely, the amount of heat generated is large, so high-output fans are used for cooling. However, high-output fans tend to cause hard disk resonance due to vibrations caused by wind pressure. In electronic devices such as HDDs, vibrations can cause malfunctions and failures, so parts used in electronic devices (for example, case materials) are also required to have high vibration damping properties.

Typical examples of materials with vibration damping properties include rubber and resin, but since rubber and resin generally have low thermal conductivity, they are difficult to use in applications that require cooling, such as electronic devices. Therefore, a metal material with high thermal conductivity and vibration damping properties is needed. Further, when rubber and resin are used in applications such as sliding door rails that are subject to loads and at least a portion of which is exposed to the outdoor environment, properties such as strength and corrosion resistance are often insufficient. Furthermore, since these parts are easily visible to people, their surface appearance, such as the silvery white color characteristic of stainless steel, is also preferred.

Metal materials having vibration damping properties are broadly classified into composite type, ferromagnetic type, dislocation type, and twin type based on the vibration energy damping mechanism. Each type of these has advantages and disadvantages, but ferromagnetic types are preferred because they have high strength and good vibration damping properties. In the ferromagnetic type, the magnetic domains rearrange in one direction when an external force such as vibration is applied, and when the load is removed, the magnetic domains rearrange randomly. The residual strain at this time can absorb vibration energy and damp vibration.

Examples of ferromagnetic metal materials include, in mass %, C: 0.001 to 0.03%, Si: 0.1 to 1.0%, Mn: 0.1 to 2.0%, Ni: 0.01-0.6%, Cr: 10.5-24.0%, N: 0.001-0.03%, Nb: 0-0.8%, Ti: 0-0.5%, Cu : 0-2.0%, Mo: 0-2.5%, V: 0-1.0%, Al: 0-0.3%, Zr: 0-0.3%, Co: 0-0. 6%, REM (rare earth element): 0 to 0.1%, Ca: 0 to 0.1%, the balance being Fe and unavoidable impurities, the matrix is a single ferrite phase, and the ferrite crystal grains A ferritic stainless steel material is known that has a metal structure with an average grain size of 0.3 to 3.0 mm and a residual magnetic flux density of 45 mT or less (Patent Document 1).

In addition, in mass%, C: 0.001 to 0.04%, Si: 0.1 to 2.0%, Mn: 0.1 to 1.0%, Ni: 0.01 to 0.6%, Cr: 10.5-20.0%, Al: 0.5-5.0%, N: 0.001-0.03%, Nb: 0-0.8%, Ti: 0-0.5% , Cu: 0-0.3%, Mo: 0-0.3%, V: 0-0.3%, Zr: 0-0.3%, Co: 0-0.6%, REM (rare earth element ): 0 to 0.1%, Ca: 0 to 0.1%, the balance is Fe and unavoidable impurities, the matrix is a single ferrite phase, and the average crystal grain size of ferrite crystal grains is 0. A ferritic stainless steel material is also known that has a metal structure of .3 to 3.0 mm and a residual magnetic flux density of 45 mT or less (Patent Document 2).

JP 2017-39955 Publication JP2017-39956A

Since the composition of the ferritic stainless steel material described in Patent Document 1 has not been studied in detail, it is difficult to obtain desired vibration damping properties when the contents of Cr and Mo are low. In addition, since the vibration damping heat treatment is performed at high temperatures for a long time, the ferritic stainless steel material of Patent Document 1 may have a thick oxide film and become colored (interference color occurs) during the vibration damping heat treatment, and the surface appearance may be insufficient. I can't say that.
In addition, although the damping properties of the ferritic stainless steel material described in Patent Document 2 are improved by increasing the Al content, since Al is an element that is very easily oxidized, an oxide film forms during vibration damping heat treatment. It tends to become thick.

As vibration damping heat treatment is carried out at high temperatures for a long period of time as described above, the oxide film grows to a thickness of several tens of nanometers or more, which interferes with light in the visible light range and produces colors such as yellow and purple (interference colors). Can be seen. Since this interference color sensitively reflects the thickness of the oxide film, it is difficult to achieve a uniform color tone over the entire surface, which impairs the aesthetic appearance.
On the other hand, it is conceivable to remove the oxide film that causes deterioration of the surface appearance by polishing, pickling, or the like. However, polishing adds strain to the ferritic stainless steel material, resulting in a decrease in vibration damping properties. Furthermore, it is very difficult to remove the oxide film (particularly Al ₂ O ₃ ) by pickling, and even if it is removed, the gloss is likely to decrease and the surface will become rough.
Therefore, it has been difficult to provide high vibration damping properties while maintaining the silvery white appearance characteristic of ferritic stainless steel materials.

The present invention was made in order to solve the above problems, and aims to provide a ferritic stainless steel material with excellent vibration damping properties and surface appearance, a method for manufacturing the same, and a vibration damping member. .
Another object of the present invention is to provide a ferritic stainless steel material for vibration damping heat treatment that can produce a ferritic stainless steel material with excellent vibration damping properties and surface appearance.

The present inventors conducted extensive research to solve the above-mentioned problems, and found that in ferritic stainless steel materials having an oxide film on the surface of the base material, the composition of the base material, the lightness index L ^* of the oxide film, and the chromaticity It has been found that vibration damping properties and surface appearance can be improved by controlling the Ticks indices a ^* and b ^* , the 85 degree specular gloss Gs (85 degrees), and the loss coefficient η. In addition, the present inventors have discovered that a ferritic stainless steel material having such characteristics can be obtained by performing vibration damping heat treatment under predetermined conditions using a material with a predetermined composition (ferritic stainless steel material for vibration damping heat treatment). I also found that I could get it. The present invention has been completed based on these findings.

That is, the present invention provides a ferritic stainless steel material having an oxide film on the surface of the base material,
The base material has, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00-35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50-4.00%, N: 0.100% or less, Nb: 0.20- 1.00%, 1.8Cr + 2.8Mo: 40.00% or more, and the remainder is Fe and impurities,
The oxide film has a brightness index L ^* of 70.0 or more in the L ^* a ^* b ^* color system, a chromatic index a ^* of within ±1.0, and a chromatic index b ^* of within ±5.0. and the 85 degree specular gloss Gs (85°) is 50.0% or more,
The ferritic stainless steel material has a loss coefficient η of 4.0×10 ⁻⁴ or more.

The present invention also provides a ferritic stainless steel material having an oxide film on the surface of the base material,
The base material has, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00-35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50-4.00%, N: 0.100% or less, Nb: 0.20- 1.00%, further contains one or more selected from the following groups A and B, and has a composition of 1.8Cr + 2.8Mo: 40.00% or more, with the balance consisting of Fe and impurities. ,
The oxide film has a brightness index L ^* of 70.0 or more in the L ^* a ^* b ^* color system, a chromatic index a ^* of within ±1.0, and a chromatic index b ^* of within ±5.0. and the 85 degree specular gloss Gs (85°) is 50.0% or more,
The ferritic stainless steel material has a loss coefficient η of 4.0×10 ⁻⁴ or more.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less.

The present invention also provides, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00 to 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0.100% or less, Nb: 0. This is a ferritic stainless steel material for damping heat treatment having a composition of 20 to 1.00%, 1.8Cr+2.8Mo: 40.00% or more, and the balance consisting of Fe and impurities.

The present invention also provides, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00 to 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0.100% or less, Nb: 0. 1.8Cr+2.8Mo: 40.00% or more, and the remainder is Fe and impurities. This is a ferritic stainless steel material for vibration damping heat treatment.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less.

Further, the present invention heat-treats the ferritic stainless steel material for vibration damping heat treatment at 1000 to 1200°C in an oxygen partial pressure atmosphere of 1.0 × 10 ^-2 Pa or less, and then reduces the cooling rate to 800°C by 30°C. This is a method for manufacturing a ferritic stainless steel material, which is cooled at a temperature of at least ℃/min.

Furthermore, the present invention is a vibration damping member including the ferritic stainless steel material.

According to the present invention, it is possible to provide a ferritic stainless steel material with excellent vibration damping properties and surface appearance, a method for manufacturing the same, and a vibration damping member.
Further, according to the present invention, it is possible to provide a ferritic stainless steel material for vibration damping heat treatment that can produce a ferritic stainless steel material with excellent vibration damping properties and surface appearance.

The vibration damping properties of ferromagnetic ferritic stainless steel materials are determined by the amount of deformation (magnetostriction) when the magnetic domains move. Although Al can increase magnetostriction, it is an element that is easily oxidized, and therefore becomes a factor in coloring the oxide film (generating interference color) during vibration damping heat treatment and deteriorating the surface appearance. Further, like Al, Ti is an element that is easily oxidized, and therefore becomes a factor in coloring the oxide film during vibration damping heat treatment and deteriorating the surface appearance. Therefore, in order to improve the surface appearance, a composition system was adopted that did not contain Al and Ti or had a reduced amount of Al and Ti. On the other hand, in order to increase magnetostriction, Cr was added in combination with Mo, and their contents were optimized.

In addition, in order for ferritic stainless steel materials to exhibit vibration damping properties, it is necessary for magnetic domains to be able to move freely, but strains (dislocations), precipitates, and grain boundaries in ferritic stainless steel materials impede the movement of magnetic domains. . Heat treatment is necessary to reduce strain (dislocations), precipitates, and grain boundaries in ferritic stainless steel materials, but precipitates (especially Nb carbonitrides) that precipitate during melting can be removed by heat treatment. Hard to disappear. Therefore, in order to reduce the amount of precipitates, a composition system containing no Nb or with a reduced Nb content was adopted.

Furthermore, when the amount of solid solution of C and N in the ferritic stainless steel material is large, they combine with Cr to precipitate Cr carbide and Cr nitride. These precipitates take away surrounding Cr and cause sensitization that reduces corrosion resistance. Therefore, in order to reduce the solid solution amount of C and N and suppress sensitization, Nb was added to fix C and N as precipitates. Nb carbonitrides (precipitates) precipitate at temperatures above 800°C and below 1000°C and dissolve into solid solution at temperatures above 1000°C, so damping heat treatment was performed at 1000 to 1200°C to dissolve Ti carbonitrides into solid solution. Thereafter, the precipitates were made fine by increasing the cooling rate to 800°C.
Furthermore, in order to suppress the oxidation of elements such as Cr, Fe, and Mn, and to form an oxide film that is less likely to be colored (generate interference color), the atmosphere during the damping heat treatment was controlled.

Embodiments of the present invention completed based on the above viewpoints will be specifically described below. The present invention is not limited to the following embodiments, and modifications and improvements may be made to the following embodiments as appropriate based on the common knowledge of those skilled in the art without departing from the spirit of the present invention. It is to be understood that such materials also fall within the scope of the present invention.
In this specification, the expression "%" regarding components means "mass %" unless otherwise specified.

(1) Ferritic stainless steel material The ferritic stainless steel material according to the embodiment of the present invention has an oxide film on the surface of the base material.
Here, in this specification, "stainless steel material" means a material formed from stainless steel, and the shape of the material is not particularly limited. Examples of the material shape include plate shape (including band shape), rod shape, and tube shape. Further, various types of steel sections having a T-shape or I-shape in cross-section may be used.
Moreover, in this specification, "ferritic type" means that the metal structure is mainly a ferrite phase at room temperature. Therefore, "ferritic" includes those containing a small amount of phase other than ferrite phase (for example, austenite phase, martensite phase, etc.).

The base material is C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00 to 35 .00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0.100% or less, Nb: 0.20 to 1.00%. 1.8Cr+2.8Mo: 40.00% or more, with the remainder consisting of Fe and impurities.

Here, in this specification, "impurities" are components that are mixed in due to raw materials such as ores and scraps and various factors in the manufacturing process when ferritic stainless steel materials are manufactured industrially, and are included in the present invention. It means something that is permissible as long as it does not cause any adverse effects. For example, impurities include unavoidable impurities. Examples of impurities include O.
Regarding the content of each element, "containing xx% or less" means containing an amount of not more than xx% but more than 0% (particularly more than the impurity level).

Further, the base material can further include one or more selected from Group A and Group B below.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less. Each component will be explained in detail below.

(C: 0.100% or less)
C is an element that affects characteristics such as intergranular corrosion resistance (sensitization suppression effect) and workability of ferritic stainless steel materials. If the content of C is too large, the workability and intergranular corrosion resistance of the ferritic stainless steel material will decrease. Therefore, the upper limit of the C content is 0.100%, preferably 0.080%, and more preferably 0.050%. 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 scouring cost. Therefore, the lower limit of the C content is preferably 0.001%, more preferably 0.002%.

(Si: 1.00% or less)
Si is an effective element for improving the oxidation resistance of ferritic stainless steel materials. If the Si content is too high, the workability and toughness of the ferritic stainless steel material will decrease. Therefore, the upper limit of the Si content is 1.00%, preferably 0.90%, and more preferably 0.80%. On the other hand, the lower limit of the Si content is not particularly limited, but from the viewpoint of ensuring the effect of Si, it is preferably 0.01%, more preferably 0.03%, and still more preferably 0.05%.

(Mn: 1.00% or less)
Mn is an element useful as a deoxidizing element. If the Mn content is too high, MnS, which becomes a corrosion starting point, is likely to be generated and the ferrite phase is destabilized. Therefore, the upper limit of the Mn content is 1.00%, preferably 0.90%, and more preferably 0.80%. On the other hand, the lower limit of the Mn content is not particularly limited, but from the viewpoint of ensuring the effect of Mn, it is preferably 0.01%, more preferably 0.03%, and still more preferably 0.05%.

(P: 0.100% or less)
P is an element that affects properties such as weldability and workability of ferritic stainless steel materials. If the content of P is too large, the above characteristics may deteriorate. Therefore, the upper limit of the P content is 0.100%, preferably 0.080%, and more preferably 0.050%. 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 scouring cost. Therefore, the lower limit of the P content is preferably 0.010%, more preferably 0.012%.

(S: 0.100% or less)
S is an element that generates MnS, which becomes a starting point for corrosion, and affects properties such as toughness of ferritic stainless steel materials. If the content of S is too large, the above characteristics may deteriorate. Therefore, the upper limit of the S content is 0.100%, preferably 0.080%, and more preferably 0.050%. 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 scouring cost. Therefore, the lower limit of the S content is preferably 0.0001%, more preferably 0.0005%.

(Cr: 20.00-35.00%)
Cr is an effective element for improving the corrosion resistance and vibration damping properties (increase in magnetostriction) 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 35.00%, preferably 34.50%, and more preferably 34.00%. On the other hand, if the Cr content is too low, the above effects cannot be sufficiently obtained. Therefore, the lower limit of the Cr content is 20.00%, preferably 20.50%, and more preferably 21.00%.

(Ni: 1.00% or less)
Ni is an effective element 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 1.00%, preferably 0.80%, and more preferably 0.60%. On the other hand, the lower limit of the Ni content is not particularly limited, but from the viewpoint of ensuring the effect of Ni, it is preferably 0.01%, more preferably 0.03%.

(Cu: 1.00% or less)
Cu is an effective element 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 1.00%, preferably 0.70%, and more preferably 0.30%. On the other hand, the lower limit of the Cu content is not particularly limited, but from the viewpoint of ensuring the effect of Cu, it is preferably 0.001%, more preferably 0.01%.

(Mo: 0.50-4.00%)
Mo is an effective element for improving the corrosion resistance and vibration damping properties (increase in magnetostriction) of ferritic stainless steel materials. If the content of Mo is too high, the workability of the ferritic stainless steel material will decrease and the manufacturing cost will increase. Therefore, the upper limit of the Mo content is 4.00%, preferably 3.80%, and more preferably 3.60%. On the other hand, if the content of Mo is too small, the above effects cannot be sufficiently obtained. Therefore, the lower limit of the Mo content is 0.50%, preferably 0.60%, and more preferably 0.80%.

(N: 0.100% or less)
N is an element that affects characteristics such as intergranular corrosion resistance (sensitization suppressing effect) and workability of ferritic stainless steel materials. If the N content is too high, the workability and intergranular corrosion resistance of the ferritic stainless steel material will decrease. Therefore, the upper limit of the N content is 0.100%, preferably 0.080%, and more preferably 0.050%. 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 scouring cost. Therefore, the lower limit of the N content is preferably 0.001%, more preferably 0.003%, and still more preferably 0.005%.

(Nb: 0.20-1.00%)
Nb is a component that suppresses sensitization of ferritic stainless steel materials by forming carbonitrides (precipitates) of C and N. If the Nb content is too high, the amount of precipitates in the ferritic stainless steel material will increase, resulting in a decrease in vibration damping properties. Therefore, the upper limit of the Nb content is 1.00%, preferably 0.80%, and more preferably 0.50%. On the other hand, if the Nb content is too low, sensitization of the ferritic stainless steel material cannot be suppressed, resulting in a decrease in corrosion resistance. Therefore, the lower limit of the Nb content is 0.20%, preferably 0.23%, and more preferably 0.25%.

(1.8Cr+2.8Mo: 40.00% or more)
As described above, Cr and Mo are effective elements for improving the damping properties (increase in magnetostriction) and corrosion resistance of ferritic stainless steel materials. In order to effectively obtain these effects, the balance between Cr and Mo is essential, and 1.8Cr+2.8Mo should be at least 40.00%, preferably at least 40.50%, more preferably at least 41.00%. Control. On the other hand, the upper limit of 1.8Cr+2.8Mo is not particularly limited, but is preferably 74.00%, more preferably 73.00%, and still more preferably 72.00%.

(Al: 0.10% or less)
Al is an element effective in improving the damping properties (increase in magnetostriction) of ferritic stainless steel materials. However, if the Al content is too large, the oxide film will be colored (interference color will occur) during the vibration damping heat treatment, resulting in poor surface appearance. Therefore, the upper limit of the Al content is 0.10%, preferably 0.09%, and more preferably 0.08%. On the other hand, the lower limit of the Al content is not particularly limited, but from the viewpoint of ensuring the effect of Al, it is preferably 0.001%, more preferably 0.005%, and still more preferably 0.01%.

(Ti: 0.10% or less)
Ti is an element that affects characteristics such as intergranular corrosion resistance (sensitization suppressing effect) of ferritic stainless steel materials. If the Ti content is too high, the workability of the ferritic stainless steel material will decrease. Further, like Al, Ti is an element that easily oxidizes, so the oxide film is colored (generates interference color) during vibration damping heat treatment, resulting in a deterioration of the surface appearance. Therefore, the upper limit of the Ti content is 0.10%, preferably 0.09%, and more preferably 0.08%. On the other hand, the lower limit of the Ti content is not particularly limited, but from the viewpoint of ensuring the effect of Ti, it is preferably 0.001%, more preferably 0.005%, and even more preferably 0.01%.

(Zr: 1.00% or less, Co: 1.00% or less, V: 1.00% or less, W: 1.00% or less)
Zr, Co, V, and W are elements effective in improving the oxidation resistance of ferritic stainless steel materials. If the content of Zr, Co, V, and W is too large, the workability and toughness of the ferritic stainless steel material will decrease, and the manufacturing cost will increase. Therefore, the upper limits of the contents of Zr, Co, V, and W are all 1.00%, preferably 0.80%, and more preferably 0.60%. On the other hand, the lower limits of the contents of Zr, Co, V, and W are not particularly limited, but are preferably 0.001%, more preferably 0.01%.

(REM: 0.100% or less, Ca: 0.100% or less)
REM (rare earth element) and Ca are elements effective in improving the oxidation resistance of ferritic stainless steel materials. If the contents of REM and Ca are too high, it will lead to an increase in the manufacturing cost of the ferritic stainless steel material. Therefore, the upper limits of the contents of REM and Ca are both 0.100%, preferably 0.080%, and more preferably 0.050%. On the other hand, the lower limits of the REM and Ca contents are not particularly limited, but are preferably 0.0001%, more preferably 0.003%.
Note that REM is a general term for two elements, scandium (Sc) and yttrium (Y), and 15 elements (lanthanoids) from lanthanum (La) to lutetium (Lu). These may be used alone or as a mixture.

(Sn: 0.100% or less)
Sn is an element effective in improving the corrosion resistance of ferritic stainless steel materials. If the content of Sn is too high, Sn will segregate and the productivity will decrease. Therefore, the upper limit of the Sn content is 0.100%, preferably 0.080%, and more preferably 0.050%. On the other hand, the lower limit of the Sn content is not particularly limited, but is preferably 0.001%, more preferably 0.005%.

(B: 0.0100% or less)
B is an element effective in improving the secondary workability of ferritic stainless steel materials. If the content of B is too large, the fatigue strength of the ferritic stainless steel material will decrease. Therefore, the upper limit of the content of B is 0.0100%, preferably 0.0080%, and more preferably 0.0050%. On the other hand, the lower limit of the B content is not particularly limited, but is preferably 0.0001%, more preferably 0.0005%.

The average crystal grain size of the base material is preferably 100 to 1000 μm. By controlling the average crystal grain size to 100 μm or more, the number of grain boundaries that impede the movement of magnetic domains, which are effective for exhibiting vibration damping properties, is reduced, so that vibration damping properties can be improved. From the viewpoint of stably obtaining this effect, the average crystal grain size is more preferably 120 μm or more, still more preferably 150 μm or more, still more preferably 180 μm or more, and particularly preferably 190 μm or more. Furthermore, by controlling the average crystal grain size to 1000 μm or less, it is possible to stably suppress a decrease in toughness due to extreme coarsening of crystal grains. From the viewpoint of stably obtaining this effect, the average crystal grain size is more preferably 800 μm or less, still more preferably 600 μm or less, and still more preferably 500 μm or less.
Here, in this specification, the average crystal grain size means that measured using an optical microscope described below.

The base material preferably has a number density of precipitates having a diameter of 0.5 μm or more and less than 5.0 μm of 300 pieces/mm ² or less. Since precipitates having a diameter of 0.5 μm or more and less than 5.0 μm hinder movement of the magnetic domain, damping properties can be improved by controlling the number density of these precipitates to 300 pieces/mm ² or less. From the viewpoint of stably obtaining this effect, the number density of the precipitates is more preferably 290 pieces/mm ² or less, and even more preferably 280 pieces/mm ² or less. Note that the lower the number of these precipitates is, the better from the viewpoint of damping properties, so the lower limit is not particularly limited, but is preferably 100 pieces/mm ² , more preferably 120 pieces/mm ² , and even more preferably 130 pieces/mm 2 . ^mm2 .
Here, in this specification, the diameter and number density of precipitates mean those measured using a SEM (scanning electron microscope), which will be described later. In addition, the diameter of the precipitate is a value calculated by (length of long side x length of short side) ^1/2 .

The oxide film has a brightness index L ^* of 70.0 or more in the L ^* a ^* b ^* color system, a chromatic index a ^* of within ±1.0, and a chromatic index b ^* of within ±5.0. be. If the lightness index L ^* and chromatic index a ^* and b ^* are within the above ranges, it can be said that the desired color tone (silver white) has been obtained, improving the surface appearance of the ferritic stainless steel material. do.
The lightness index L ^* is preferably 72.0 or more, more preferably 75.0 or more, from the viewpoint of stably securing a desired color tone. Note that the upper limit of the lightness index L ^* is generally 90.0, although it is not particularly limited.
The chromatic index a ^* is preferably within ±0.8, more preferably within ±0.6, from the viewpoint of stably securing a desired color tone. Further, the chromatic index b ^* is preferably within ±4.8, preferably within ±4.6, from the viewpoint of stably obtaining a desired color tone.
Here, in this specification, "lightness index L ^* " and "chromanetics index a ^* and b ^* " can be measured based on JIS Z8722:2009.

The oxide film has an 85 degree specular gloss Gs (85 degrees) of 50.0% or more. If Gs (85°) is within the above range, it can be said that the desired gloss is obtained, and the surface appearance of the ferritic stainless steel material is improved.
Gs (85°) is preferably 60.0% or more, more preferably 70.0% or more from the viewpoint of stably securing the desired gloss. Note that the upper limit of Gs (85°) is not particularly limited, but is generally 90.0%.
Here, in this specification, "85 degree specular gloss Gs (85 degrees)" can be measured based on JIS Z8741:1997.

The thickness of the oxide film affects the color tone and gloss of the oxide film, that is, the surface appearance of the ferritic stainless steel material. From the viewpoint of imparting desired color tone and gloss to the oxide film, the thickness of the oxide film is preferably 50 nm or less, more preferably 48 nm or less, and still more preferably 45 nm or less. Note that the lower limit of the thickness of the oxide film is not particularly limited, but is preferably 5 nm, more preferably 7 nm.
Here, in this specification, the thickness of the oxide film is 1/1/2 of the maximum value of O (oxygen) from the surface in the component concentration profile in the depth direction obtained using glow discharge optical emission spectroscopy (GD-OES). The depth shall be up to the point 4.

The ferritic stainless steel material according to the embodiment of the present invention has a loss coefficient η of 4.0×10 ⁻⁴ or more. By setting the loss coefficient η within such a range, desired vibration damping properties can be ensured.
The loss coefficient η is preferably 4.1×10 ⁻⁴ or more, more preferably 4.2×10 ⁻⁴ or more, from the viewpoint of stably ensuring desired vibration damping properties. Note that the upper limit value of the loss coefficient η is not particularly limited, but is generally 2.0×10 ⁻³ , preferably 1.0×10 ⁻³ .
Here, in this specification, the loss coefficient η means what is measured by the "central vibration 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 3.0 mm or less, more preferably 2.8 mm or less, and still more preferably 2.5 mm or less. Further, the thickness of this ferritic stainless steel material is preferably 0.2 mm or more, more preferably 0.3 mm or more.

(2) Ferritic stainless steel material for vibration damping heat treatment The ferritic stainless steel material for vibration damping heat treatment according to the embodiment of the present invention is a material before vibration damping heat treatment is performed. This ferritic stainless steel material for vibration damping heat treatment has the same composition as the base material of the above-mentioned ferritic stainless steel material.

Therefore, the ferritic stainless steel material for damping heat treatment according to the embodiment of the present invention has C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, and P: 0.100% or less. , S: 0.100% or less, Cr: 20.00 to 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0 .100% or less, Nb: 0.20 to 1.00%, 1.8Cr+2.8Mo: 40.00% or more, and the balance is Fe and impurities.

Further, the ferritic stainless steel material for vibration damping heat treatment according to the embodiment of the present invention has C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less. , S: 0.100% or less, Cr: 20.00 to 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0 .100% or less, Nb: 0.20 to 1.00%, further containing one or more selected from the following groups A and B, 1.8Cr + 2.8Mo: 40.00% or more, The remainder has a composition consisting of Fe and impurities.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less. In addition, since the details of each component are as described above, the explanation thereof will be omitted.

The ferritic stainless steel material for damping heat treatment according to the embodiment of the present invention may be either a hot-rolled material or a cold-rolled material, and can be manufactured by a conventional method. Specifically, a hot rolled material can be obtained by first melting stainless steel having the above composition, forging or casting, and then hot rolling. Moreover, a cold-rolled material can be obtained by sequentially performing annealing, pickling, and cold rolling on a hot-rolled material. The cold-rolled material may be annealed and pickled sequentially, if necessary. Note that the conditions in each step may be adjusted as appropriate depending on the composition of the stainless steel, etc., and are not particularly limited.

The ferritic stainless steel material for damping heat treatment according to the embodiment of the present invention may be processed into a predetermined member, or may remain in the form of a plate or coil. Examples of processing methods include various press working using a mold, bending, welding, and the like.

(3) Method for manufacturing ferritic stainless steel materials The method for manufacturing ferritic stainless steel materials according to the embodiments of the present invention is not particularly limited as long as it is a method that can manufacture ferritic stainless steel materials having the above characteristics. For example, the method for manufacturing a ferritic stainless steel material according to an embodiment of the present invention includes subjecting the ferritic stainless steel material for vibration damping heat treatment to vibration damping heat treatment. In the damping heat treatment, the ferritic stainless steel material for vibration damping heat treatment is heat treated at 1000 to 1200°C in an oxygen partial pressure atmosphere of 1.0 x 10 ^-2 Pa or less, and then the cooling rate is 30°C/min to 800°C. The above is performed by cooling.

By heat-treating ferritic stainless steel materials for vibration damping heat treatment in an oxygen partial pressure atmosphere of 1.0 x 10 ^-2 Pa or less, oxidation of elements such as Cr, Fe, and Mn is suppressed, and the oxide film is less likely to become thick. . As a result, the desired color tone and gloss can be ensured, and the surface appearance of the ferritic stainless steel material can be improved. The oxygen partial pressure is preferably 0.5 x 10 ^-2 Pa (5.0 x 10 ^-3 Pa), more preferably 0.3 x 10 ^-2 Pa (3 .0×10 ^-3 Pa). Note that the lower limit of the oxygen partial pressure is generally 1.0×10 ⁻⁶ Pa, although it is not particularly limited.

Furthermore, by heat-treating the ferritic stainless steel material for damping heat treatment at 1000 to 1200°C, crystal grains can be grown to have an average crystal grain size of 100 to 1000 μm. Here, the atmosphere for the heat treatment may be an air atmosphere or a non-oxidizing atmosphere. Note that the heat treatment time is not particularly limited, but is preferably 10 to 120 minutes.

In addition, since the temperature range from the heat treatment temperature of 1000 to 1200°C to 800°C is the temperature range in which Nb carbonitrides precipitate, the cooling rate in this temperature range is set to 30°C/min or more, preferably 35°C/min. As described above, by more preferably setting the heating rate to 40° C./min or higher, precipitation of Nb carbonitrides can be effectively suppressed. As a result, the number density of precipitates having a diameter of 0.5 μm or more and less than 5.0 μm is controlled to 300 pieces/mm ² or less. 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.

(4) Vibration damping member The vibration damping member according to the embodiment of the present invention includes the above-mentioned ferritic stainless steel material. Since the above-mentioned ferritic stainless steel material has excellent vibration damping properties and surface appearance, this vibration damping member also has excellent vibration damping properties and surface appearance.
Examples of vibration damping members include, but are not limited to, exhaust system members such as exhaust pipes and mufflers, automobile parts such as sliding door rails and battery cases, electronic parts such as hard disk covers, and acoustic parts.

EXAMPLES The present invention will be explained in detail below with reference to examples, but the present invention is not to be construed as being limited to these examples.

(Examples 1 to 8 and Comparative Examples 1 to 10)
A ferritic stainless steel plate 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 4.0 mm, and then the hot-rolled plate is annealed at 1050°C and pickled. An annealed plate was obtained. Next, the hot rolled annealed plate was cold rolled to obtain a cold rolled plate having a thickness of 1.0 mm. Next, a test piece measuring 100 mm in the width direction x 300 mm in the rolling direction was cut out from the cold-rolled plate, and the surface was polished using SiC abrasive paper (#400) so that the polished lines were parallel to the rolling direction. Ta.

The above test piece was placed in an electric furnace and heat treated for 60 minutes at the temperature shown in Table 2 in the oxygen partial pressure atmosphere shown in Table 2, and then cooled from the heat treatment temperature to 800°C at the rate shown in Table 2. . Note that the oxygen partial pressure was controlled by adjusting the introduction ratio of oxygen gas and argon gas. Furthermore, the cooling rate of the test piece was controlled by adjusting the flow rate of cooling gas introduced into the electric furnace.

The test pieces subjected to the above heat treatment (damping heat treatment) were evaluated as follows.

(Average crystal grain size of base material)
After cutting a 10 mm x 10 mm measurement test piece from the above test piece (at least 20 mm away from the edge in the width direction), the cross section in the thickness direction parallel to the rolling direction was the observation surface. I filled it with resin to make it look like this. Next, the resin-filled measurement test piece was wet-polished to a mirror finish, and then etched with fluoronitric acid to reveal the metallographic structure, which was observed using an optical microscope. Observation with an optical microscope was conducted in accordance with JIS G0551:2013, by drawing a straight line at an arbitrary position on the optical microscope image, measuring the number of intersections between the straight line and the grain boundary, and taking the average intercept length as the grain size. . The crystal grain size was measured by drawing 20 or more straight lines in multiple fields of view, and the average value thereof was taken as the average crystal grain size.

(Number density of precipitates with a diameter of 0.5 μm or more and less than 5.0 μm in the substrate)
After cutting out a 10 mm x 10 mm measurement test piece from the above test piece (at least 20 mm away from the edge in the width direction), it was filled with resin so that the rolled surface became the observation surface. provided. Next, the resin-filled measurement test piece was wet-polished to a mirror finish. Using FE-SEM (SU5000 manufactured by Hitachi High-Tech Corporation) on the mirror-treated surface, precipitates were detected using the automatic analysis function (precipitates larger than 0.47 μm can be detected), and the composition of the precipitates was determined by EDX point analysis. was identified. In this analysis, the measurement area was 5 mm ² (2.0 mm x 2.5 mm), the observation magnification was 200 times (18 fields of view were measured with 5% wrapping of one field of view range of 0.48 mm x 0.64 mm), and the EDX analysis beam The diameter was set to 0.05 μm. Then, the number of precipitates having a diameter of 0.5 μm or more and less than 5.0 μm and containing 1% or more of Nb or Ti in EDX point analysis was determined. The diameter of the precipitate was calculated by (long side length x short side length) ^1/2 . Next, the number density of precipitates was calculated by dividing the number of precipitates by the observation area.

(Thickness of oxide film)
A 50 mm square measurement test piece was cut out from the above test piece, and the surface was degreased with acetone. Next, the oxide film was analyzed using glow discharge optical emission spectroscopy (GD-OES) in accordance with JIS K0144:2018.
In GD-OES, the depth from the surface to the point where O (oxygen) becomes 1/4 of the maximum value in the obtained depth direction component concentration profile was defined as the thickness of the oxide film.

(color tone of oxide film)
Color tone measurements are performed at five arbitrary locations on the oxide film using a spectrophotometer with a measurement diameter of 3 mm in accordance with JIS Z8722:2009, and the average value is determined by CIELAB (L ^* a ^*) in accordance with JIS Z8781-4:2013. b ^* color system), the lightness index L ^* , and the chromatic indexes a ^* and b ^* .

The measurement conditions for the above color tone were as follows.
Equipment: Konica Minolta spectrophotometer CM-700d
Light source: Pulsed xenon lamp Light receiving element: Dual 36 element silicon photodiode array Target mask: φ3mm
Measurement: 10° field of view Auxiliary illuminant: D65 daylight, color temperature 6504K
Specular reflection processing mode: SCI

(Glossiness of oxide film)
The 85 degree specular gloss Gs (85 degrees) was measured at five arbitrary locations on the oxide film using a gloss meter PG-1M manufactured by Nippon Denshoku Kogyo in accordance with JIS Z8741:1997, and the average value was evaluated as the evaluation result. And so. In addition, the distance between each measurement position was 5 mm or more.

(Vibration damping property: loss coefficient)
A test piece for measurement measuring 10 mm in the width direction x 250 mm in the rolling direction was cut out from the above test piece. Using this measurement test piece, the loss coefficient η was measured according to the "central vibration method" specified in JIS K7391:2008. Specifically, a test piece with its central portion fixed was vibrated by an impedance head, and mechanical impedance was derived from the output force signal and acceleration vibration. Then, the loss coefficient η was derived based on the antiresonance frequency at which the mechanical impedance peaks and the frequency at which the amplitude decreases by 3 dB from the peak.

The above evaluation results are shown in Table 3.

As shown in Table 3, in Examples 1 to 8, the brightness index L ^* , chromatic index a ^* and b ^* , 85 degree specular gloss Gs (85 degrees), and loss coefficient η of the oxide film were within the predetermined ranges. It was confirmed that the material satisfies the requirements and has excellent vibration damping properties and surface appearance.
On the other hand, in Comparative Example 1, the heat treatment temperature and cooling rate were not appropriate, so the average crystal grain size was small and the number density of precipitates was high, resulting in insufficient vibration damping properties.
In Comparative Example 2, the cooling rate after heat treatment was not appropriate, and as a result, the number density of precipitates increased, resulting in insufficient vibration damping properties.
In Comparative Example 3, the surface appearance was not sufficient because the oxygen partial pressure during the heat treatment was not appropriate.
In Comparative Example 4, the Nb content was low and the Ti content was high, so the surface appearance was not sufficient.
Comparative Example 5 had an insufficient surface appearance due to the high Al content.
Comparative Examples 6 to 8 have low Cr and Mo contents, an inappropriate balance of Cr and Mo (1.8Cr+2.8Mo is too low), and do not contain Nb, and have low Ti and Al contents. The surface appearance and vibration damping properties were not sufficient.
In Comparative Example 9, the Mn content was high, the Cr content was low, and the balance between Cr and Mo was not appropriate (1.8Cr+2.8Mo was too low), so the damping properties were not sufficient.
In Comparative Example 10, the Mo content was low and the balance between Cr and Mo was not appropriate (1.8Cr+2.8Mo was too low), so the damping properties were not sufficient.

As can be seen from the above results, according to the present invention, it is possible to provide a ferritic stainless steel material with excellent vibration damping properties and surface appearance, a method for manufacturing the same, and a vibration damping member. Further, according to the present invention, it is possible to provide a ferritic stainless steel material for vibration damping heat treatment that can produce a ferritic stainless steel material with excellent vibration damping properties and surface appearance.

Claims (16)

A ferritic stainless steel material having an oxide film on the surface of the base material,
The base material has, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00-35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50-4.00%, N: 0.100% or less, Nb: 0.20- 1.00%, 1.8Cr + 2.8Mo: 40.00% or more, and the remainder is Fe and impurities,
The oxide film has a brightness index L ^* of 70.0 or more in the L ^* a ^* b ^* color system, a chromatic index a ^* of within ±1.0, and a chromatic index b ^* of within ±5.0. and the 85 degree specular gloss Gs (85°) is 50.0% or more,
The ferritic stainless steel material has a loss coefficient η of 4.0×10 ^-4 or more. A ferritic stainless steel material having an oxide film on the surface of the base material,
The base material has, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00-35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50-4.00%, N: 0.100% or less, Nb: 0.20- 1.00%, further contains one or more selected from the following groups A and B, and has a composition of 1.8Cr + 2.8Mo: 40.00% or more, with the balance consisting of Fe and impurities. ,
The oxide film has a brightness index L ^* of 70.0 or more in the L ^* a ^* b ^* color system, a chromatic index a ^* of within ±1.0, and a chromatic index b ^* of within ±5.0. and the 85 degree specular gloss Gs (85°) is 50.0% or more,
The ferritic stainless steel material has a loss coefficient η of 4.0×10 ^-4 or more.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less. The ferritic stainless steel material according to claim 2, wherein the base material has a composition including the A group. The ferritic stainless steel material according to claim 2, wherein the base material has a composition containing the B group. The ferritic stainless steel material according to any one of claims 1 to 4, wherein the oxide film has a thickness of 50 nm or less. The substrate has the following (a) and (b):
A claim that satisfies one or more of the following: (a) the average crystal grain size is 100 to 1000 μm; (b) the number density of precipitates with a diameter of 0.5 μm or more and less than 5.0 μm is 300 pieces/mm ² or less The ferritic stainless steel material according to any one of 1 to 4. The substrate has the following (a) and (b):
A claim that satisfies one or more of the following: (a) the average crystal grain size is 100 to 1000 μm; (b) the number density of precipitates with a diameter of 0.5 μm or more and less than 5.0 μm is 300 pieces/mm ² or less 5. The ferritic stainless steel material described in 5. Based on mass, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00~ 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0.100% or less, Nb: 0.20 to 1.00% 1.8Cr+2.8Mo: 40.00% or more, with the balance consisting of Fe and impurities. A ferritic stainless steel material for damping heat treatment. Based on mass, C: 0.100% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.100% or less, S: 0.100% or less, Cr: 20.00~ 35.00%, Ni: 1.00% or less, Cu: 1.00% or less, Mo: 0.50 to 4.00%, N: 0.100% or less, Nb: 0.20 to 1.00% 1.8Cr+2.8Mo: 40.00% or more, and the balance is Fe and impurities. Stainless steel material.
[Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less [Group B] Zr: 1.00% or less, Co: 1.00% or less, V: 1. 00% or less, W: 1.00% or less, REM: 0.100% or less, Ca: 0.100% or less, Sn: 0.100% or less, and B: 0.0100% or less. The ferritic stainless steel material for vibration damping heat treatment according to claim 9, having a composition including the group A. The ferritic stainless steel material for vibration damping heat treatment according to claim 9, having a composition containing the B group. The ferritic stainless steel material for damping heat treatment according to any one of claims 9 to 11 is heat treated at 1000 to 1200°C in an oxygen partial pressure atmosphere of 1.0 × 10 ^-2 Pa or less, and then heated to 800°C. A method for manufacturing ferritic stainless steel material, which comprises cooling at a cooling rate of 30°C/min or higher. A vibration damping member comprising the ferritic stainless steel material according to any one of claims 1 to 4. A vibration damping member comprising the ferritic stainless steel material according to claim 5. A vibration damping member comprising the ferritic stainless steel material according to claim 6. A damping member comprising the ferritic stainless steel material according to claim 7.