company news about UNS S32760 F55 SUPER DUPLEX STAINLESS STEEL

UNS S32760 is a high-performance duplex stainless steel, also known as super duplex stainless steel. It is widely used in marine, chemical, oil and gas industries due to its excellent corrosion resistance, high strength and good weldability.

UNS S32760 and F55 are different ways of expressing the same material.

• UNS S32760 is a superalloy designation, belonging to Super Duplex Stainless Steel. It has high chromium (24-26%), nickel (6-8%) and molybdenum (3-4%) content, and is particularly suitable for use in corrosive environments such as marine, chemical, oil and gas.
• F55 is a common designation for UNS S32760 in the ASTM A240 standard. F55 is mainly used to express the chemical composition and mechanical properties of the same alloy, so the two are essentially the same.

Both UNS S32760 and F55 are super duplex stainless steels, widely used in highly corrosive environments, and the material properties of the two are basically the same.

Chemical Composition

The typical chemical composition of UNS S32760 (Super Duplex Stainless Steel) is as follows:

• Chromium (Cr): 24.0-26.0%
• Nickel (Ni): 6.0-8.0%
• Molybdenum (Mo): 3.0-4.0%
• Manganese (Mn): ≤ 1.0%
• Silicon (Si): ≤ 1.0%
• Carbon (C): ≤ 0.03%
• Phosphorus (P): ≤ 0.03%
• Sulfur (S): ≤ 0.02%
• Nitrogen (N): 0.24-0.32%
• Iron (Fe): Balance

The alloy contains high levels of chromium, nickel and molybdenum, which give it excellent corrosion resistance in many corrosive environments.

Main Features and Properties

1. Excellent Corrosion Resistance:

• UNS S32760 has extremely high resistance to pitting, crevice corrosion and stress corrosion cracking (SCC), and is particularly suitable for harsh environments such as seawater and chemical processing.
• It can effectively resist corrosion caused by chlorides, so it is widely used in the marine and chemical fields.

2. High Strength:

• The duplex structure (mixture of austenite and ferrite phases) gives UNS S32760 a high yield strength, usually between 550-750 MPa.
• Even at high temperatures, the alloy's strength and toughness are still excellent, suitable for high-pressure applications.

3. Good Weldability:

• UNS S32760 has good welding properties and is suitable for various welding methods. However, heat treatment may be required after welding to ensure optimal mechanical properties.
• The addition of nitrogen enhances the alloy's strength and pitting resistance, even in the weld area.

4. Oxidation Resistance:

• The alloy has good oxidation resistance at high temperatures, especially in sulfur-containing gases, steam and high-temperature air. It can usually be used in the temperature range of 300°C to 350°C.

5. High toughness:

• UNS S32760 maintains high toughness at low temperatures and is suitable for applications in low temperature and freezing environments.

Mechanical properties

• Tensile strength: typically 800-1100 MPa
• Yield strength: typically 550-750 MPa
• Elongation: 25-35%
• Hardness: typically 250-300 HB
• Impact toughness: Excellent toughness at low temperatures, usually can withstand environments below -50°C.

Application areas

1. Marine industry:

• Due to its excellent corrosion resistance in seawater and chloride environments, UNS S32760 is widely used in offshore platforms and underwater equipment, such as seawater pipelines and heat exchangers.

2. Chemical and petrochemical industries:

• UNS S32760 is often used to manufacture chemical equipment exposed to strong acid and alkali environments, such as reactors, heat exchangers and storage tanks.

3. Oil and Gas Industry:

• The alloy is widely used in oil and gas production, especially in downhole equipment and pipelines in offshore oil fields.

4. ​Power Industry:

• Due to its excellent oxidation resistance, UNS S32760 is also used for high-temperature boiler tubes and heat exchangers.

5. Saltwater Environment Applications:

• Turbine blades, marine vessels and other marine application equipment.

6. Heat Treatment

• Solution Annealing: UNS S32760 is usually delivered in the solution annealing state. The solution annealing process involves heating the alloy to 1020-1100°C and then rapidly cooling.
• Heat treatment may be required after welding to relieve welding stress and ensure that the alloy maintains corrosion resistance and good mechanical properties in the weld area.

Welding

• The welding of UNS S32760 requires controlled welding parameters to avoid excessive heat input and cooling rates to prevent undesirable phase transformation or intergranular corrosion. Using suitable filler materials and controlling appropriate welding processes are essential to ensure quality.

Comparison with other alloys

S32760 VS. S31803 (F51):

• UNS S32760 has better resistance to chloride stress corrosion cracking than S31803 and is suitable for more severe environments, especially in seawater applications.

S32760 vs. Inconel 625:

• Inconel 625 offers excellent high temperature oxidation resistance, but may be more expensive and is not as corrosion resistant as S32760 in chloride environments. S32760 has better corrosion resistance in chloride environments than other alloys.

UNS S32760 (Super Duplex Stainless Steel) is a high chromium, high molybdenum duplex alloy designed for harsh environments in the marine, petrochemical, oil and gas industries. Its high strength, excellent corrosion resistance, oxidation resistance and good mechanical properties make it an important application value in these fields. Due to its unique chemical composition and properties, UNS S32760 has become an ideal material for extreme corrosive environments and high pressure applications.