Stainless Steel Chemical Properties

Austenitic stainless steels are the most common type of stainless steel, primarily composed of iron, chromium, and nickel. They have a face-centered cubic (FCC) structure, which makes them highly corrosion-resistant and easily formable.

• Typical Grades: 304, 316, 310, 321
• Chemical Composition:
  
  • Chromium (Cr): 16-26%
  • Nickel (Ni): 6-22%
  • Manganese (Mn): 2-10%
  • Carbon (C): < 0.08% (for 304), varies for others
  • Silicon (Si): 0.5-1.0%
  • Iron (Fe): Balance
  • Molybdenum (Mo): 2-3% (for 316, 316L)
  • Nitrogen (N): 0.1-0.2%
• Key Properties:
  
  • Excellent corrosion resistance, especially to pitting and crevice corrosion.
  • Good strength at both high and low temperatures.
  • Non-magnetic (except when cold worked).
  • Poor in terms of wear resistance compared to other stainless steel types.
  • Excellent weldability and formability.

Ferritic stainless steels have a body-centered cubic (BCC) structure and are primarily made of iron, chromium, and little to no nickel. These grades offer good corrosion resistance but are generally not as resistant as austenitic steels.

• Typical Grades: 410, 430, 446
• Chemical Composition:
  
  • Chromium (Cr): 10.5-30%
  • Nickel (Ni): < 1%
  • Manganese (Mn): 1-2%
  • Carbon (C): < 0.15%
  • Iron (Fe): Balance
  • Silicon (Si): 0.5-1.0%
• Key Properties:
  
  • Moderate corrosion resistance, good in mildly corrosive environments.
  • Magnetic in nature.
  • Good formability, but not as good as austenitic grades.
  • Resistant to stress corrosion cracking.
  • Poor low-temperature toughness.

Martensitic stainless steels have a higher carbon content and a body-centered tetragonal (BCT) structure, making them hardenable by heat treatment. These steels offer high strength and hardness, but their corrosion resistance is lower compared to austenitic and ferritic types.

• Typical Grades: 410, 420, 440C
• Chemical Composition:
  
  • Chromium (Cr): 11.5-18%
  • Nickel (Ni): < 1%
  • Manganese (Mn): 0.5-1.0%
  • Carbon (C): 0.15-1.2% (varies by grade)
  • Iron (Fe): Balance
  • Silicon (Si): 1.0%
• Key Properties:
  
  • High strength and hardness (after heat treatment).
  • Moderate to poor corrosion resistance.
  • Magnetic in nature.
  • Poor weldability and formability compared to austenitic types.
  • Excellent wear resistance and strength at high temperatures.

Martensitic stainless steels have a higher carbon content and a body-centered tetragonal (BCT) structure, making them hardenable by heat treatment. These steels offer high strength and hardness, but their corrosion resistance is lower compared to austenitic and ferritic types.

• Typical Grades: 410, 420, 440C
• Chemical Composition:
  
  • Chromium (Cr): 11.5-18%
  • Nickel (Ni): < 1%
  • Manganese (Mn): 0.5-1.0%
  • Carbon (C): 0.15-1.2% (varies by grade)
  • Iron (Fe): Balance
  • Silicon (Si): 1.0%
• Key Properties:
  
  • High strength and hardness (after heat treatment).
  • Moderate to poor corrosion resistance.
  • Magnetic in nature.
  • Poor weldability and formability compared to austenitic types.
  • Excellent wear resistance and strength at high temperatures.

Duplex stainless steels are a combination of austenitic and ferritic phases, giving them a good balance of strength, corrosion resistance, and formability. They are generally used in applications where high strength and resistance to stress corrosion cracking are required.

• Typical Grades: 2205, 2507
• Chemical Composition:
  
  • Chromium (Cr): 18-25%
  • Nickel (Ni): 4.5-8%
  • Manganese (Mn): 1-3%
  • Molybdenum (Mo): 2.5-4%
  • Nitrogen (N): 0.1-0.3%
  • Iron (Fe): Balance
  • Silicon (Si): 0.5%
• Key Properties:
  
  • Excellent combination of strength and corrosion resistance.
  • Good resistance to pitting and crevice corrosion.
  • Resistant to stress corrosion cracking in chloride environments.
  • Magnetic (due to the ferritic phase).
  • Good weldability and formability.

These steels are high-strength materials that can be hardened by a heat treatment process called precipitation hardening. They offer a combination of good corrosion resistance and high strength.

• Typical Grades: 630 (17-4 PH), 660, 675
• Chemical Composition:
  
  • Chromium (Cr): 15-17%
  • Nickel (Ni): 3-7%
  • Manganese (Mn): 1.0-2.0%
  • Copper (Cu): 3-5% (for 17-4 PH)
  • Carbon (C): 0.07-0.15%
  • Iron (Fe): Balance
  • Silicon (Si): 0.5%
  • Aluminum (Al): Small amount (for age hardening)
• Key Properties:
  
  • Excellent strength and hardness.
  • Moderate to good corrosion resistance.
  • Can be heat treated to very high strength.
  • Magnetic.
  • Fairly poor weldability compared to other stainless steels.

• Inconel 600:
  
  • Ni (58-63%), Cr (14-17%), Fe (balance), and small amounts of other elements.
  • Known for its resistance to oxidation, carburization, and its ability to withstand high temperatures.
• Inconel 625:
  
  • Ni (58-67%), Cr (20-23%), Mo (8-10%), Fe (5%), Nb (3-4%), and small amounts of Ti and Al.
  • Exceptional resistance to oxidation and corrosion, particularly in marine environments. It's widely used in chemical processing and aerospace applications.
• Inconel 718:
  
  • Ni (50-55%), Cr (17-21%), Fe (balance), Mo (2.8-3.3%), Nb (4.75-5.5%), Ti (0.65-1.15%).
  • Known for its high strength and resistance to creep and fatigue at elevated temperatures, commonly used in gas turbines and rocket engines.
• Inconel X-750:
  
  • Ni (70-75%), Cr (14-17%), Fe (balance), Mo (0.9-1.3%), Ti (0.5-1.5%), Al (0.2-0.4%)

• Nimonic 80A:
  
• Nickel (Ni) – 78-80%
• Chromium (Cr) – 15-17%
• Cobalt (Co) – 7-9%
• Titanium (Ti) – 2.5-3.5%
• Aluminum (Al) – 1.4-2.0%
• Molybdenum (Mo) – 2.5-3.0%
• Iron (Fe) – 1.0% max
• Carbon (C) – 0.1% max
• Silicon (Si) – 0.5% max

Nimonic 263:

• Nickel (Ni) – 63-72%
• Chromium (Cr) – 22-24%
• Cobalt (Co) – 10-12%
• Titanium (Ti) – 2.5-3.5%
• Aluminum (Al) – 1.5-2.0%
• Molybdenum (Mo) – 2.0-3.0%
• Iron (Fe) – 2.0% max
• Carbon (C) – 0.1% max

Chemical Composition:

• Nickel (Ni): 57.0-63.0%
• Molybdenum (Mo): 15.0-17.0%
• Chromium (Cr): 14.5-16.5%
• Iron (Fe): 4.0-7.0%
• Tungsten (W): 3.0-4.5%
• Cobalt (Co): Max. 2.5%
• Manganese (Mn): Max. 1.0%
• Silicon (Si): Max. 0.08%
• Carbon (C): Max. 0.010%
• Phosphorus (P): Max. 0.02%
• Sulfur (S): Max. 0.02%

Properties:

• Excellent resistance to pitting, stress-corrosion cracking, and general corrosion in a wide range of aggressive environments, including sulfuric acid, hydrochloric acid, and seawater.
• Ideal for use in industries like chemical processing, pulp and paper, and marine environments.
• High resistance to high-temperature oxidation.

Chemical Composition:

• Nickel (Ni): 56.0-63.0%
• Molybdenum (Mo): 12.5-14.5%
• Chromium (Cr): 20.0-22.0%
• Iron (Fe): Max. 5.0%
• Tungsten (W): Max. 3.0%
• Cobalt (Co): Max. 2.0%
• Manganese (Mn): Max. 1.0%
• Silicon (Si): Max. 0.08%
• Carbon (C): Max. 0.015%
• Phosphorus (P): Max. 0.02%
• Sulfur (S): Max. 0.02%

Properties:

• Exceptional resistance to pitting, crevice corrosion, and stress-corrosion cracking, particularly in environments containing chlorides.
• Widely used in the chemical processing, pharmaceutical, and aerospace industries.
• Provides superior resistance to a broader range of acids, including hydrochloric and sulfuric acids.

Chemical Composition:

• Nickel (Ni): 65.0-70.0%
• Molybdenum (Mo): 26.0-30.0%
• Iron (Fe): Max. 2.5%
• Chromium (Cr): Max. 0.5%
• Cobalt (Co): Max. 2.5%
• Manganese (Mn): Max. 1.0%
• Silicon (Si): Max. 0.08%
• Carbon (C): Max. 0.010%
• Phosphorus (P): Max. 0.02%
• Sulfur (S): Max. 0.02%

Properties:

• Superior resistance to hydrochloric acid, both at high concentrations and at elevated temperatures.
• Excellent performance in reducing environments, particularly in acid processing applications.
• Not as resistant to oxidizing environments as other Hastelloy grades, making it less versatile for certain applications.

Chemical Composition:

• Nickel (Ni): 47.0-50.0%
• Molybdenum (Mo): 15.0-17.0%
• Chromium (Cr): 15.0-17.0%
• Iron (Fe): 10.0-13.0%
• Tungsten (W): 3.0-4.5%
• Cobalt (Co): Max. 2.5%
• Manganese (Mn): Max. 1.0%
• Silicon (Si): Max. 0.08%
• Carbon (C): Max. 0.010%
• Phosphorus (P): Max. 0.02%
• Sulfur (S): Max. 0.02%

Properties:

• Excellent resistance to oxidation and many aggressive environments, including sulfuric acid and acetic acid.
• Higher resistance to carburization and high-temperature oxidation compared to some other Hastelloy grades.
• Suitable for high-temperature applications and can handle corrosive conditions in industries such as chemical processing and power generation.