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JP-7854590-B2 - Ferritic stainless steel material and its manufacturing method, ferritic stainless steel material for vibration damping heat treatment, and vibration damping member

JP7854590B2JP 7854590 B2JP7854590 B2JP 7854590B2JP-7854590-B2

Inventors

  • 田井 善一
  • 安部 雅俊

Assignees

  • 日本製鉄株式会社

Dates

Publication Date
20260507
Application Date
20220801

Claims (16)

  1. A ferritic stainless steel material having an oxide film on the surface of the base material, The aforementioned substrate has a composition, by mass, consisting of 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%, with 1.8Cr + 2.8Mo: 40.00% or more, and the remainder consisting of Fe and impurities. The oxide film has a lightness index L * of 70.0 or higher in the L * a * b * color system, a * of ±1.0 or less, a b * of ±5.0 or less, and an 85-degree specular gloss Gs (85°) of 50.0% or higher. A ferritic stainless steel material having a loss factor η of 4.0 × 10⁻⁴ or greater.
  2. A ferritic stainless steel material having an oxide film on the surface of the base material, The aforementioned substrate, by mass, contains 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%, and further contains one or more selected from the following groups A and B, with a composition of 1.8Cr + 2.8Mo: 40.00% or more, and the remainder consisting of Fe and impurities. The oxide film has a lightness index L * of 70.0 or higher in the L * a * b * color system, a * of ±1.0 or less, a b * of ±5.0 or less, and an 85-degree specular gloss Gs (85°) of 50.0% or higher. A ferritic stainless steel material having a loss factor η of 4.0 × 10⁻⁴ or greater. [Group A] One or more selected from Al: 0.10% or less and Ti: 0.10% or less. [Group B] One or more selected from 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.
  3. The aforementioned substrate has a composition including the aforementioned group A, as described in claim 2.
  4. The aforementioned substrate has a composition including the aforementioned group B, as described in claim 2.
  5. The ferritic stainless steel material according to any one of claims 1 to 4, wherein the thickness of the oxide film is 50 nm or less.
  6. The aforementioned substrate is (a) and (b) below: A ferritic stainless steel material according to any one of claims 1 to 4, satisfying one or more of the following conditions: (a) the average grain size is 100 to 1000 μm, and (b) the number density of precipitates with a diameter of 0.5 μm or more and less than 5.0 μm is 300 particles/ mm² or less.
  7. The aforementioned substrate is (a) and (b) below: The ferritic stainless steel material according to claim 5, satisfying one or more of the following conditions: (a) the average grain size is 100 to 1000 μm, and (b) the number density of precipitates with a diameter of 0.5 μm or more and less than 5.0 μm is 300 particles/mm² or less.
  8. A ferritic stainless steel material for vibration-damping heat treatment, having a composition based on mass, containing 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, and Nb: 0.20 to 1.00%, with 1.8Cr + 2.8Mo: 40.00% or more, and the remainder consisting of Fe and impurities.
  9. A ferritic stainless steel material for vibration-damping heat treatment having a composition, on a mass basis, containing 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, and Nb: 0.20 to 1.00%, further containing one or more selected from the following groups A and B, with a composition of 1.8Cr + 2.8Mo: 40.00% or more, and the remainder 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] One or more selected from 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.
  10. A ferritic stainless steel material for vibration-damping heat treatment according to claim 9, having a composition including the aforementioned group A.
  11. A ferritic stainless steel material for vibration-damping heat treatment according to claim 9, having a composition including the aforementioned group B.
  12. A method for manufacturing a ferritic stainless steel material having an oxide film on the surface of the base material in which the lightness index L * in the L * a * b * color system is 70.0 or more, the Chromanetics index a * is within ±1.0, the Chromanetics index b * is within ±5.0, and the 85-degree specular gloss Gs (85°) is 50.0% or more, and the loss factor η is 4.0 × 10⁻⁴ or more, A method for manufacturing a ferritic stainless steel material, comprising heat-treating a vibration-damping heat-treated ferritic stainless steel material according to any one of claims 8 to 11 at 1000 to 1200°C in an oxygen partial pressure atmosphere of 1.0 × 10⁻² Pa or less, and then cooling it to 800°C at a cooling rate of 30°C/min or more.
  13. A vibration damping member comprising a ferritic stainless steel material as described in any one of claims 1 to 4.
  14. A vibration damping member comprising the ferritic stainless steel material described in claim 5.
  15. A vibration damping member comprising the ferritic stainless steel material described in claim 6.
  16. A vibration damping member comprising the ferritic stainless steel material described in claim 7.

Description

This invention relates to ferritic stainless steel materials, methods for manufacturing the same, ferritic stainless steel materials for vibration-damping heat treatment, and vibration-damping members. With the electrification of automobiles, engine noise and vibration have decreased, improving the quietness of the cabin. As a result, noises previously masked by engine noise, as well as high-frequency sounds specific to electrification, are more easily perceived as unwanted noises by passengers. Therefore, the level of vibration damping required for materials used in automobiles is increasing. Furthermore, vibration damping is also required for components such as sliding door rails, from the perspective of suppressing vibrations caused by opening and closing the doors. Furthermore, in recent years, electronic devices such as hard disk drives (hereinafter abbreviated as "HDDs") have seen an increase in heat generation per unit volume due to the advancement of storage capacity. In particular, in locations where numerous HDDs are densely installed, such as data centers, heat generation becomes significant, leading to the use of high-powered fans for cooling. However, high-powered fans are prone to causing resonance in hard disks due to vibrations caused by air pressure. Since vibrations can cause malfunctions and failures in electronic devices such as HDDs, high vibration damping properties are required for components used in electronic devices (e.g., case materials). While rubber and resin are typical examples of materials with vibration-damping properties, their generally low thermal conductivity makes them unsuitable for applications requiring cooling, such as electronic equipment. Therefore, metal materials with high thermal conductivity and vibration-damping properties are needed. Furthermore, when used in applications where loads are applied, such as sliding door rails, and at least a portion is exposed to the outdoor environment, rubber and resin often lack sufficient strength, corrosion resistance, and other properties. Additionally, because these parts are highly visible, the silvery-white surface appearance characteristic of stainless steel is also preferred. Vibration-damping metal materials are broadly classified into composite, ferromagnetic, dislocation, and twinning types based on their vibration energy damping mechanisms. Each type has its own advantages and disadvantages, but the ferromagnetic type, which offers high strength and good vibration damping, is preferred. In the ferromagnetic type, when an external force such as vibration is applied, the magnetic domains rearrange in one direction, and when the load is removed, the magnetic domains rearrange randomly. The residual strain at this time absorbs vibration energy, thereby damping the vibration. Examples of ferromagnetic metallic materials include, by mass%, C: 0.001-0.03%, Si: 0.1-1.0%, Mn: 0.1-2.0%, 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- A ferritic stainless steel material is known that has a chemical composition of 0.3%, Co: 0-0.6%, REM (rare earth elements): 0-0.1%, Ca: 0-0.1%, with the remainder being Fe and unavoidable impurities; has a ferrite single-phase matrix; a metallic structure with an average grain size of ferrite grains of 0.3-3.0 mm; and a remanent magnetic flux density of 45 mT or less (Patent Document 1). Also, in mass%, C: 0.001-0.04%, Si: 0.1-2.0%, Mn: 0.1-1.0%, Ni: 0.01-0.6%, 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%, C A ferritic stainless steel material is also known that has a chemical composition of o: 0-0.6%, REM (rare earth elements): 0-0.1%, Ca: 0-0.1%, with the remainder being Fe and unavoidable impurities, a matrix that is a single phase of ferrite, a metallic structure with an average grain size of ferrite crystal grains of 0.3-3.0 mm, and a remanent magnetic flux density of 45 mT or less (Patent Document 2). Japanese Patent Publication No. 2017-39955Japanese Patent Publication No. 2017-39956 The vibration damping properties of ferromagnetic ferritic stainless steel materials are determined by the magnitude of deformation (magnetostriction) when magnetic domains move. While Al (alkaline aluminum) can increase magnetostriction, it is an easily oxidized element, leading to discoloration of the oxide film (interference coloration) during vibration damping heat treatment, thus degrading the surface appearance. Similarly, Ti (tin) is also easily oxidized, leading to discoloration of the oxide film during vibration damping heat treatment, further degrading the surface appearance. Therefore, to improve the surface appearance, a composition system was adopted that either does not contain Al or Ti, or has reduced levels of Al and Ti. On the other hand, to increase magnetostriction, Cr (chromium) was added in combination with Mo (metallium), and their conten