The Ultimate Guide to Grade of Stainless Steel Pipe
Stainless steel is a type of metal alloy that is composed of a combination of iron, chromium, and other metals. Stainless steel pipes are used in many industries due to their superior properties such as corrosion resistance, strength, and durability. It is popularly used in the construction industry, automotive industry, and food processing industry.
This article will provide an overview of the different grades of stainless steel pipe, including 300 Series Austenitic, 400 Series Martensitic, 400 Series Ferritic, and Precipitation Hardening Stainless Steel.The most widely used grades of stainless steel pipes are 304 and 316, which contain chromium and nickel in varying amounts.
It will also discuss the different chemical compositions of these grades and provide guidance on how to choose the right grade for an application.
Austenitic （300 Series)
Austenitic stainless steel pipe is a grade of stainless steel pipe known for its corrosion resistance and weldability. It is made of elements like chromium, nickel, and molybdenum and is typically composed of 16-18% chromium, 8-10% nickel, and 2-3% molybdenum. It is suitable for a variety of applications and offers excellent corrosion resistance, weldability, and can be hardened through cold treatment.
The grade of austenitic stainless steel pipe
AISI 304/304L: This is the most widely used austenitic stainless steel grade. It contains 18-20% chromium and 8-10.5% nickel. AISI 304L is a low-carbon variation of AISI 304, which offers improved weldability.
AISI 316/316L: These grades contain 16-18% chromium, 10-14% nickel, and 2-3% molybdenum. AISI 316L is the low-carbon version of AISI 316, providing enhanced corrosion resistance, particularly against chlorides and acids.
AISI 321/321H: These grades contain 17-19% chromium and 9-12% nickel, with the addition of titanium. AISI 321H is the high-carbon version of AISI 321, suitable for high-temperature applications. They offer excellent resistance to intergranular corrosion.
AISI 904L: This grade contains 19-23% chromium, 23-28% nickel, and 4-5% molybdenum. It offers exceptional corrosion resistance, especially in harsh environments such as sulfuric acid.
Typical uses for austenitic stainless steel pipe
Austenitic stainless steel pipe is used in a wide variety of applications, including construction, automotive, and food processing. It is also used in structural applications and for heat exchangers
Ferritic （400 Series）
The chemical composition of ferritic stainless steel pipe typically includes 12-18% chromium, low carbon content, and is hardened by heat treatment. Ideal for those seeking a durable, reliable, and strong material for their construction projects.
The grades of ferrtic stainles steel pipe
AISI 409: This grade contains 11-12% chromium and is often used in applications requiring good corrosion resistance and high-temperature oxidation resistance.
AISI 430: With 16-18% chromium content, AISI 430 offers good corrosion resistance.
AISI 439: Similar to AISI 430, AISI 439 has higher chromium content (17-18%) and improved resistance to corrosion and oxidation at high temperatures.
AISI 446: This grade contains higher chromium content (23-30%) and offers excellent high-temperature oxidation resistance.
Typical uses for ferritic stainless steel pipe
Ferritic stainless steel pipe is commonly used in fasteners, machinery parts, and pump shafts. Its resistance to corrosion in mild atmospheres, steam, and mild chemical environments make it a suitable choice for industrial applications.
Duplex
Duplex stainless steels are a combination of austenitic and ferritic stainless steels, and are composed of chromium, molybdenum, nickel and other elements. Typical grades of duplex stainless steel pipe include 1Cr18Mn10Ni5Mo3N, 2101 and 2205.
The grades of duplex stainles steel pipe
UNS S31803 (SAF 2205): This is the most widely used duplex stainless steel grade. It contains approximately 22% chromium, 5-6% nickel, and 3% molybdenum. UNS S31803 offers excellent corrosion resistance, high strength, and good weldability.
UNS S32205 (SAF 2205): Similar to UNS S31803, UNS S32205 offers the same composition and properties. It provides high resistance to stress corrosion cracking, making it suitable for applications involving harsh environments and chloride-containing solutions.
UNS S32750 (SAF 2507): This grade, also known as super duplex stainless steel, contains approximately 25% chromium, 7% nickel, and 4% molybdenum. UNS S32750 offers exceptional corrosion resistance, high strength, and excellent resistance to pitting and crevice corrosion. It is commonly used in offshore and marine environments, chemical processing plants, and desalination systems.
UNS S32760 (Zeron 100): Another super duplex stainless steel grade, UNS S32760 contains higher amounts of chromium, nickel, and molybdenum compared to UNS S32750. It provides excellent corrosion resistance, high strength, and improved resistance to corrosion fatigue and erosion. UNS S32760 is often used in applications where superior corrosion resistance and mechanical properties are required.
Typical uses for duplex stainless steel pipe
This type of stainless steel is frequently employed in applications such as oil and gas exploration, chemical processing, heat exchangers, and wastewater treatment. Its superior properties make it an ideal choice for a variety of industries.
Martensitic
Martensitic stainless steel pipe is a type of stainless steel pipe which contains a high carbon content and is typically used for applications requiring high strength and hardness.
The grades of martensitic stainles steel pipe
AISI 410: This grade contains 11.5-13.5% chromium and is known for its high strength, hardness, and wear resistance.
AISI 420: With 12-14% chromium content, AISI 420 offers good corrosion resistance along with high hardness and moderate strength.
AISI 431: This grade contains 15-17% chromium and 1.25-2.5% nickel. AISI 431 provides good corrosion resistance along with high strength and hardness.
AISI 440C: This grade contains 16-18% chromium and 0.95-1.20% carbon, offering excellent hardness, wear resistance, and corrosion resistance.
Typical uses for martensitic stainless steel pipe
Due to its high tensile and yield strength, martensitic stainless steel is commonly used for a variety of applications including fasteners, machinery parts, and pump shafts.It is also widely used in the production of kitchen and medical equipment .
The following list will show you about all the chemical position of austenitic stainless steel , ferritic stainless steel and duplex stainless steel .
Chemical Content of Austenitic Stainless Steel |
Chemical Content | C | Si | Mn | P | S | Cr | Ni | Mo | Ti |
304（ASTM)/ 1.4301(EN) | ≤ 0.070 | ≤ 0.75 | ≤ 2.00 | ≤ 0.040 | ≤ 0.015 | 17.5-19.0 | 8.0 - 10.0 | / | |
304L (ASTM ) / 1.4307(EN) | ≤ 0.030 | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.015 | 18.0-20.0 | 8.0 - 12.0 | / | |
316l(ASTM)/ 1.4304(EN) | ≤ 0.030 | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.015 | 16.0-18.0 | 10.0 - 14.0 | 2.0 - 3.0 | |
321 (ASTM)/ 1.4541(EN) | ≤ 0.080 | ≤ 0.75 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 17.0-19.0 | 9.0- 12.0 | | ≥ 5(C+N) |
Chemical Content of Ferritic Stainless Steel |
Chemical Content | C | Si | Mn | P | S | Cr | Ni | Mo | Ti |
409（ASTM）/ 1.4512(EN) | ≤ 0.030 | ≤ 1.00 | ≤ 1.00 | ≤ 0.040 | ≤ 0.020 | 10.5-11.7 | / | / | ≥ 8(C+N) |
430 (ASTM )/ 1.4016(EN) | ≤ 0.120 | ≤ 1.00 | ≤ 1.00 | ≤ 0.040 | ≤ 0.030 | 16.0-18.0 | ≤ 0.75 | / | |
436(ASTM)/ 1.4513(EN) | ≤ 0.12 | ≤ 1.00 | ≤ 1.00 | ≤ 0.040 | ≤ 0.030 | 16.0-18.0 | 0.75 - 1.25 | / | ≥0.20+4 (C+N) |
Chemical Content of Duplex Stainless Steel |
Chemical Content | C | Si | Mn | P | S | Cr | Ni | Mo | N |
2205(ASTM) /1.4462 (EN) | ≤ 0.30 | ≤ 1.00 | ≤ 2.00 | ≤ 0.030 | ≤ 0.020 | 22.0-23.5 | 4.5 - 6.5 | 3.0 - 3.5 | 0.14 - 0.20 |
2304( ASTM) /1.4362(EN) | ≤ 0.30 | ≤ 1.00 | ≤ 2.50 | ≤ 0.040 | ≤ 0.030 | 21.5-24.5 | 3.0 - 5.5 | 0.05- 0.60 | 0.05 - 0.20 |
How to choose the right grade of stainless steel pipe?
When selecting stainless steel pipe for a particular application, it is important to consider the application's cost versus performance needs, as well as the environmental conditions in which the pipe will be used. In order to determine the best grade of stainless steel pipe for a specific application, consideration must be given to the cost versus performance needs of the application, as well as the environmental conditions in which the pipe will be used.
Conclusion
In essence, stainless steel pipes epitomize the marriage of innovation and functionality. From the corrosion-resistant Austenitic to the robust Martensitic grades, each category offers a distinct set of attributes catering to diverse industries. The Duplex variety bridges the gap with a harmonious blend of strengths, while the Ferritic types excel in reliability.
What’s more, grade of stainless steel pipe is an important factor to consider when selecting a pipe for a particular application. The grade of stainless steel pipe should be chosen based on the chemical composition of the metal, the desired properties of the pipe, and the requirements of the application.
