ステンレス鋼はクロム含有量により腐食に強い, 保護酸化層を形成する. It comes in families and grades with different strength, 被削性, and corrosion behavior. This guide covers the key properties, popular grades, and where each one fits.
ステンレス鋼とは何ですか?
Stainless steel is an iron alloy that contains at least about 10.5% クロム.
The chromium forms a thin, self-healing oxide layer that blocks corrosion. This is why stainless steel resists rust. It is not rustproof in every environment, but the right grade resists most industrial and everyday conditions.
What Gives Stainless Steel Its Properties?
Properties come from the alloying elements added to iron.
| 要素 | Main Role |
| クロム | Forms the passive film; について 10.5% minimum defines stainless steel |
| ニッケル | Stabilizes austenite and adds toughness and formability |
| モリブデン | Improves resistance to pitting and crevice corrosion in chlorides |
| 炭素 | Adds strength, but too much can cause sensitization when welded |
| Manganese and nitrogen | Strengthen and help stabilize austenite |
| 硫黄 | Improves machinability in grades such as 303, but can lower corrosion resistance |
These elements explain why 303, 304, 316, 410, そして 2205 behave differently.
Key Physical And Mechanical Properties
Chromium provides the passive film. Molybdenum can improve resistance to pitting and crevice corrosion, while nickel stabilizes austenite and contributes to toughness, 成形性, and corrosion performance in selected environments.
The table below gives typical room-temperature values. They depend on product form and condition, so verify them against the standard and the mill certificate.
| 財産 (典型的な) | 304 | 316 | 303 | 17-4 PH (H900) |
| 密度 (g/cm3) | 7.9 | 8.0 | 7.9 | 7.8 |
| Elastic modulus (GPa) | 193 | 193 | 193 | 196 |
| 降伏強さ (MPa) | 205 | 205 | 205 | 1170 |
| 抗張力 (MPa) | 515 | 515 | 620 | 1310 |
| 硬度 | について 92 HRB | について 95 HRB | について 92 HRB | について 44 HRC |
| Magnetic when annealed | いいえ | いいえ | いいえ | はい |
Austenitic grades also conduct heat less effectively than aluminum or carbon steel, and they expand more with temperature. This matters in machining and in assemblies that see temperature changes.
Five Stainless Steel Families
| Family | Typical Grades | Key Traits | 一般的な用途 |
| オーステナイト系 | 304, 316, 303, 321 | Non-magnetic when annealed, 成形可能, 溶接可能 | 食べ物, 医学, 化学薬品, 海洋 |
| フェライト系 | 430, 409 | 一般に磁性, 低コスト, 適度な耐食性 | Trim, automotive exhaust |
| マルテンサイト系 | 410, 420, 440 | 一般に磁性, hardenable by heat treatment | Cutlery, シャフト, バルブ |
| デュプレックス | 2205 | 高強度, chloride resistant | マリン, 化学薬品, 石油とガス |
| Precipitation hardening | 17-4 PH | Very high strength with good corrosion resistance | 航空宇宙, 医療器具 |
Popular Stainless Steel Grades Compared
| 学年 | Family | 耐食性 | 被削性 | 強さ | 典型的な使用 |
| 304 | オーステナイト系 | 良い | 適度 | 良い | 一般産業用, 食べ物 |
| 316 | オーステナイト系 | Better chloride resistance than 304 | 適度 | 良い | マリン, 化学薬品 |
| 303 | オーステナイト系 | 良い | 素晴らしい | 良い | 精密機械加工部品 |
| 430 | フェライト系 | 適度 | 良い | 適度 | Trim, 家電製品 |
| 410 | マルテンサイト系 | 適度 | 公平 | High after hardening | バルブ, シャフト |
| 17-4 PH | Precipitation hardening | 良い | 公平 | Very high after aging | 航空宇宙, 医学 |
| 2205 | デュプレックス | Better chloride resistance than 316 in many conditions | 公平 | 高い | マリン, 石油とガス |
Ratings are relative. They depend on heat treatment, surface condition, と環境.
304 対 316 対 303 対 17-4 PH
- 304 is the general-purpose grade for industrial and food contact.
- 316 adds molybdenum, giving better resistance to chlorides than 304.
- 303 is optimized for machining and cuts more easily, but with reduced corrosion resistance and poorer weldability in many applications.
- 17-4 PH gives very high strength after aging, but only when the condition is specified. 17-4 PH H900 and H1150 do not have the same strength, 硬度, or machining behavior.
For welded assemblies, the lower-carbon 304L and 316L grades are common choices. They reduce susceptibility to sensitization and related corrosion problems. See 316 vs 316L for the detail.
How Can Stainless Steel Corrode?
Stainless steel can still corrode under the wrong conditions.
- Pitting: localized attack, often from chlorides.
- Crevice corrosion: attack under gaskets, ファスナー, or deposits.
- Galvanic corrosion: contact with a dissimilar metal in a conductive environment.
- Intergranular corrosion: can follow sensitization from welding if carbon content is high.
- Stress-corrosion cracking: cracking under tensile stress in hot chloride environments.
The grade, 表面仕上げ, and environment decide the risk. See different types of stainless steel for more.
ステンレス鋼の用途
| 業界 | Typical Grades | なぜ |
| Food and beverage | 304, 316 | Cleanable, corrosion-resistant surfaces |
| 医療機器 | 316L, 17-4 PH | Corrosion resistance and strength |
| マリン | 316, 2205 | 耐塩化物性 |
| 化学処理 | 316, 2205 | Chemical and corrosion resistance |
| 航空宇宙 | 17-4 PH, 321 | Strength and temperature resistance |
| 建築 | 304, 316 | Appearance and weather resistance |
| 自動車 | 409, 430 | Exhaust and trim parts |
Medical suitability depends on the device, applicable material specification, surface condition, トレーサビリティ, および規制要件. A grade alone does not qualify a part for medical use.
How To Choose A Stainless Steel Grade
Choose by environment, mechanical requirement, fabrication method, そしてコスト.
- Identify the environment. 塩化物, food contact, and chemicals each point to a family.
- Set the strength and hardness you need. Hardening after fabrication points to martensitic or PH grades.
- Decide how the part is made. Machining-heavy parts favor 303. Welded assemblies favor 304L or 316L.
- Compare cost and availability. Higher-alloy grades cost more.
- Verify the grade, temper, and condition against the standard and material certificate.
Stainless Steel Machining Considerations
Machining stainless requires controlling heat, 加工硬化, and chips.
- Stainless conducts heat away from the cut less effectively than aluminum.
- Austenitic grades produce long, stringy chips that need good chip control.
- 303 is the easiest stainless grade to machine.
- 304 そして 316 work-harden, so use sharp carbide tooling and consistent feeds.
- Avoid dwelling or repeated light rubbing cuts, which can work-harden the surface.
- Use coolant to control heat at the cutting edge.
For practical details, see how to cut stainless steel そして私たちの stainless steel machining service.
Surface Treatment And Passivation
機械加工後, clean the part thoroughly and specify passivation where required to remove free-iron contamination and support a clean passive surface.
Heat tint, 規模, or chromium-depleted surface layers from machining, 溶接, or heating may require pickling or other appropriate treatment. Passivation alone does not necessarily remove those conditions.
When Stainless Steel Is Not The Best Choice
Stainless steel can still corrode and is not always the best material.
- Wrong grade plus chlorides can still pit or crack.
- Carbon steel costs less when corrosion is not a risk.
- Threads and fasteners can gall. Use anti-seize or compatible grades.
- Austenitic grades are not reliably magnetic. Magnetic response depends on composition and processing.
- Electrical and thermal conductivity are lower than copper or aluminum.
If you need high strength without stainless properties, 比較する alloy steel vs stainless steel.
よくある質問
What are the most common stainless steel grades?
304 そして 316 are the most common. 303 is common for machined parts.
違いは何ですか 304 そして 316 ステンレス鋼?
316 adds molybdenum, which improves resistance to pitting and crevice corrosion in chloride environments.
違いは何ですか 303 そして 304 ステンレス鋼?
303 is optimized for machining and generally cuts more easily than 304, but it has reduced corrosion resistance and poorer weldability in many applications. 使用 304 when corrosion resistance and fabrication matter more than machining speed.
ステンレス鋼の磁気です?
It depends on the family. Austenitic grades are largely non-magnetic when annealed. フェライト系, マルテンサイト系, and duplex grades are generally magnetic.
Which stainless steel is best for food contact?
304 そして 316 are common because they are cleanable and corrosion-resistant.
Which stainless steel is best for marine use?
316 is commonly used for many marine and coastal applications. Duplex grades such as 2205 may be selected when greater strength and chloride resistance are required. Actual selection depends on temperature, chloride concentration, crevices, and exposure.
違いは何ですか 304 and 304L, または 316 and 316L?
The L grades have lower carbon. They reduce sensitization risk and are common for welded assemblies.
ステンレス鋼をCNC加工できますか?
はい. 303 machines most easily, その間 304 そして 316 need sharper tooling and controlled cutting.
Get Help Selecting A Stainless Steel Grade
Tell us the grade, condition, 環境, mechanical requirement, と量. Our engineers will confirm the specification, review machining and finish, and quote the part with material certification.
12 』への思いステンレス鋼: プロパティ, グレード, そしてアプリケーション”