The grade of stainless steel pipe is governed by several established systems.
The Society of Automotive Engineers (SAE) employs a three-digit nomenclature that highlights the primary alloying elements and carbon content.
Alternatively, the American Society for Testing and Materials (ASTM) utilizes a six-digit system, which begins with 'A' to denote ferrous materials and incorporates additional specifications for various grades.
Understanding these grading systems is crucial for ensuring compliance and selecting appropriate stainless steel for specific applications.
Established by the Society of Automotive Engineers (SAE), the three-digit grading system classifies stainless steel based on its primary alloying elements and carbon content, facilitating standardized identification and specification across various applications. The SAE standards overview provides a clear framework for understanding the composition and performance characteristics of various grape of stainless steel pipe , particularly relevant in the automotive industry usage.
Each grade number begins with a digit representing the primary alloying element—typically chromium or nickel—followed by two digits indicating the carbon percentage. This system allows for precise grade selection criteria, ensuring that engineers choose materials that meet specific corrosion resistance factors and mechanical performance requirements for their applications.
For instance, austenitic grade of stainless steel pipe like 304 and 316 are favored for their excellent corrosion resistance, making them suitable for parts exposed to harsh environments. Conversely, martensitic grade of stainless steel pipe may be selected for applications requiring higher strength and wear resistance.
Understanding the SAE three-digit system is essential for professionals in the field, enabling informed decisions about stainless steel applications across diverse sectors, including automotive, aerospace, and medical industries.
Utilizing a six-digit grading system developed by the American Society for Testing and Materials (ASTM) facilitates a comprehensive classification of stainless steel, beginning with an 'A' to denote ferrous materials and followed by specific numerical codes that indicate the stainless steel tube material's composition and properties.
This ASTM standards overview is vital for ensuring consistency across various applications in the industry.
The first two digits of the grade signify the primary alloying elements, while the subsequent digits detail additional elements and specific characteristics, aligning with robust stainless steel specifications.
Adhering to material compliance guidelines, stainles steel pipe manufacturers can ensure their products meet industry requirements, ultimately enhancing safety and performance.
Testing procedures explained in ASTM standards include mechanical, chemical, and corrosion resistance tests, which are critical for validating the integrity of stainless steel grades.
Furthermore, grade selection criteria are essential for engineers and designers to make informed decisions based on environmental conditions and mechanical demands.
This systematic approach fosters a sense of belonging within the engineering community, as professionals can rely on standardized classifications to communicate effectively and achieve optimal outcomes in their projects.
Adopting a six-digit grading system, the American Society for Testing and Materials (ASTM) provides a standardized method for classifying stainless steel, beginning with an 'A' to denote ferrous materials. This ASTM standards overview is crucial, as it defines compliance guidelines that ensure materials meet specific performance criteria.
The six-digit system enhances the grading system's importance by allowing for precise identification of alloy compositions and properties, essential for stainless steel applications across various industries, including construction, automotive, and medical.
Each grade within this system is formulated based on rigorous testing methodologies explained in ASTM documents, which outline how materials are evaluated for strength, corrosion resistance, and other critical properties. This systematic approach fosters consistency and reliability in material selection, ensuring that engineers and manufacturers can make informed choices aligned with industry standards.
Moreover, the six-digit classification aids in maintaining regulatory compliance, which is increasingly vital in a global market driven by quality assurance. Thus, the ASTM 6-digit system serves as a cornerstone for the effective utilization and application of stainless steel, reinforcing the need for standardized practices within the industry.
Austenitic stainless steel exhibits non-magnetic properties and boasts exceptional resistance against corrosion. It excels in weldability, formability, fabricability, and ductility. This stainless steel variant upholds its corrosion resistance even in extreme temperatures, reaching as high as 1500°F. Its versatility makes it invaluable for applications requiring both low and high-temperature service. The following content are several type grade of stainless steel pipe and the chemical component and application of all kind of austentic stainless steel
Type 301: Offers high ductility for shaped products and quick hardening during mechanical work, boasting good weldability. Exhibits superior wear resistance and fatigue strength compared to 304.
Type 302: Shares the corrosion resistance of 304 but holds slightly higher strength due to added carbon content.
Type 303: Recognized as an easier-to-machine version of 304 by incorporating sulfur and phosphorus. Referred to as "A1" as per ISO 3506 standards.
Type 304/304L :The most common grade; the classic 18/8 stainless steel. Also referred to as "A2" in accordance with International Organization for Standardization ISO 3506.
Type 309: Demonstrates improved temperature resistance compared to 304.
Type 316/316L: The second most prevalent grade, particularly suitable for food and surgical stainless steel applications. The addition of molybdenum prevents specific types of corrosion. Known as "marine grade" due to heightened resistance to chloride corrosion in contrast to type 304. Commonly used in constructing nuclear reprocessing plants and prevalent in many stainless steel watches.
Type 321: Shares similarities with 304 but lowers the risk of weld decay by including titanium. Also, consider type 347, which incorporates niobium for desensitization during welding.
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Grade | Alloy Component | Characteristics & Application |
303 | 18Cr-8Ni-S | Free cutting steel |
304 | 18Cr-8Ni | Basic steel grade. Use for general purpose steel for many applications in many fields |
304L | 18Cr-8Ni-Low C | |
309 | 22Cr-12Ni | Oxidation resistance. Use in Chemical plant pipes and tubes, Radiant tubes, Thermocouple protection tubes |
309S | 22Cr-12Ni | |
310 | 25Cr-20Ni | |
310S | 25Cr-20Ni | |
312L | 20Cr-18Ni-6Mo-0.2N | Seawater resistance. Use in Seawater desalination plant pipes |
316 | 18Cr-12Ni-2Mo | Corrosion resistance. Use in LNG plant pipes, Boilers, nuclear power and chemical industry pipes and tubes |
316H | 18Cr-12Ni-2Mo-High C | |
316L | 18Cr-12Ni-2Mo-Low C | |
316Ti | 18Cr-12Ni-Mo-Ti | lntergranular corrosion resistance |
317 | 18Cr-12Ni-3Mo | Pitting corrosion resistance. Use in Chemical tanker pipes |
317L | 18Cr-12Ni-3Mo-Low C | |
321 | 18Cr-9Ni-Ti | Intergranular corrosion resistance. Use in Chemical plant pipes |
321H | 18Cr-9Ni-Ti-High C | High-temperature strength. Use in Boiler heater tubes and reheater tubes |
347 | 18Cr-9Ni-Nb | lntergranular corrosion resistance. Use in Chemical plant pipes and tubes |
347H | 18Cr-9Ni-Nb-Low C | High-temperature strength. Use in Boiler heater tubes and reheater tubes |
310MoLN | 25Cr-22Ni-2Mo-N | lntergranular corrosion resistance. Use in Urea reactor tubes |
The cost of stainless steel largely depends on the alloys present in its composition. All stainless steels require a minimum of 10.5% chromium and are primarily alloyed with iron, which constitutes a significant portion of their final makeup. However, the other elements present affect the properties and characteristics, ultimately influencing the cost.
316 stainless steel contains at least 2.0% molybdenum, making it much more corrosion-resistant than 304. Due to molybdenum being a more expensive element, 316 is generally a more expensive grade of metal.
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| Grade | C | Si | Mn | P | S | N | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|---|
| 304 | 0.07 | 1.00 | 2.00 | 0.045 | 0.015 | 0.10 | 17.5 - 19.5 | 8.0 - 10.5 | - |
| 316 | 0.07 | 1.00 | 2.00 | 0.045 | 0.015 | 0.10 | 16.5 - 18.5 | 10.0 - 13.0 | 2.0 - 2.5 |
Both grades are austenitic, meaning they do not possess magnetic properties. However, cold working can affect this. When stainless steel is formed or cut, there is a slight increase in its magnetic properties, although this increase is minor.
Stainless steel, as a family of metals, is highly corrosion-resistant. The addition of molybdenum in 316 increases its ability to withstand harsh environments, often earning it the designation of marine grade. 316 is suitable for use in more aggressive environments than ambient ones, though regular cleaning is still recommended to prolong its service life.
The high concentration of chromium in stainless steel 304 gives it excellent corrosion resistance, making it suitable for various applications, including:
Generally, stainless steel is used in applications where standard carbon steel would corrode.
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Originally developed for use in paper mills, stainless steel 316 is now commonly used in various applications, including:
316 stainless steel offers better corrosion resistance than 304 and often exhibits greater strength at high temperatures.
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Ferritic stainless steel, being magnetic and high in carbon content, tends to be brittle and exhibits relatively lower corrosion resistance when compared to austenitic stainless steel. It remains non-hardenable through heat treatment but showcases robust resistance against chloride stress corrosion cracking.
Type 408:
Heat-resistant but exhibits poor corrosion resistance with 11% Chromium and 8% Nickel content.
Type 409:
Economical variant primarily used in automobile exhausts; ferritic in nature, composed of iron and chromium.
Type 416:
Notable for its ease of machining due to additional sulfur content.
Type 430:
Mainly used for decorative purposes such as automotive trim; a ferritic stainless steel featuring good formability but exhibiting reduced temperature and corrosion resistance.
Grade | Alloy Component | Characteristics & Application |
409 | 10.5-11.7 Cr 0.5 Ni | Automotive Exhaust Systems |
430 | 18Cr | Chloride corrosion resistance and stress corrosion crack resistance. Use in water heater pipes |
444 | 19Cr-2Mo-Ti/Nb | |
446 | 25Cr-N |
Type 309 - Exhibits better temperature resistance compared to Type 304.
Type 316 - This grade of stainless steel pipe ranks as the second most common after Type 304. It is widely used in food processing and surgical stainless steel applications. The addition of molybdenum enhances its resistance to specific types of corrosion, making it ideal for marine environments and earning it the nickname "marine grade stainless steel." Type 316 is also commonly used in the construction of nuclear reprocessing plants. Most stainless steel watches are made with this grade, except for Rolex, which uses a different quality.
Type 904L - Known as 18/10 stainless steel, this grade is also referred to as “A4” according to the International Organization for Standardization ISO 3506.
Type 321 - Similar to Type 304, but with a lower risk of weld decay due to the addition of titanium.
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.
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.
Grade | Alloy Component | Characteristics | Applications |
UNS S31803 (SAF 2205) | 22% chromium, 5-6% nickel, 3% molybdenum | Excellent corrosion resistance, high strength, good weldability | Chemical processing, oil and gas, pulp and paper, desalination |
UNS S32205 (SAF 2205) | Similar to UNS S31803 | High resistance to stress corrosion cracking, suitable for harsh environments and chloride-containing solutions | Similar applications as UNS S31803 |
UNS S32750 (SAF 2507) | 25% chromium, 7% nickel, 4% molybdenum | Exceptional corrosion resistance, high strength, excellent resistance to pitting and crevice corrosion | Offshore, marine environments, chemical processing, desalination |
UNS S32760 (Zeron 100) | Higher chromium, nickel, molybdenum than S32750 | Excellent corrosion resistance, high strength, improved resistance to corrosion fatigue and erosion | Applications requiring superior corrosion resistance, better mechanical prop |
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.
Grade | Alloy Component | Characteristics | Applications |
Type 410 | 11.5-13.5% chromium | High strength, hardness, and wear resistance | Valve components, pump parts, shafts |
Type 420 | 12-14% chromium | Good corrosion resistance, high hardness, moderate strength | Surgical instruments, cutlery, molds |
Type 431 | 15-17% chromium, 1.25-2.5% nickel | Good corrosion resistance, high strength, hardness | Aircraft components, fasteners, pump shafts |
Type 440C | 16-18% chromium, 0.95-1.20% carbon | Excellent hardness, wear resistance, corrosion resistance | Bearings, surgical instruments, cutting tools |
To determine the most suitable grade of stainless steel pipe for a specific environment, assess the conditions your final product will endure. Factors like extremely low pH, high stress, elevated temperatures, and crevice corrosion can detrimentally affect the performance of stainless steel. Austenitic series steels, such as the commonly used 316 and 304 alloys, maintain their strength, toughness, and corrosion resistance across a wide temperature spectrum.
The primary consideration for selecting austenitic grade pf stainless steel pipe is their corrosion resistance. Type 316, fortified with molybdenum, even combats chloride ions commonly found in marine and chemical processing settings. Irrespective of the grade of stainless steel pipe , a well-designed structure is the best defense against corrosion.
Stainless steel, containing 10–30% chromium as an alloying element, resists corrosion. The inclusion of nickel in austenitic grades provides superior toughness and ductility among stainless grades. Alloys rich in chromium, molybdenum, and nickel exhibit the highest corrosion resistance.
Apart from alloy content, consider the material's processing, which impacts its mechanical properties. Cooling duration at various temperatures and the overall cooling rate during steel production affect its overall quality.
While heat treatment increases the hardness of carbon steels, cold working operations like rolling, bending, or drawing at lower temperatures harden austenitic stainless steel. However, note that increased hardness due to cold working may decrease properties like elongation and impact resistance.
Austenitic stainless steel is available in various forms such as bar, wire, tube, pipe, sheet, and plate. Most products require additional shaping or machining for specific applications.
For instance, stainless steel tubing might need bending, coiling, machining, welding, or end forming. When machining processes like CNC machining are involved, select a machining rate that mitigates work hardening or opt for a "free-machining" grade containing sulfur.
During welding, embrittlement in the weld area is a concern. Opt for lower carbon grades like 304, 304L, or 316L to minimize carbide formation.
Designers often select stainless steel for its aesthetic appeal—be it a shiny, electropolished "bright" finish, a dull "pickled" finish, a specific RMS polished matte surface, or a light-absorbing black oxide coating. Austenitic stainless steel grades can adopt these finishes and commonly undergo passivation.
Customers might also require certification for application-specific specifications, such as ASTM standards for different industrial uses. These standards ensure compliance with technical specifications for chemical composition, heat treatment, and other attributes.
While high-performing austenitic stainless steels are initially more expensive, they prove worthwhile due to their corrosion resistance. Choosing a corrosion-resistant material suited to the application minimizes maintenance, downtime, and replacement expenses. Life-cycle costing methods enable a comprehensive comparison of different materials in terms of current and future costs.
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The table displays only the most up-to-date standards, as ASTM standards undergo annual review and status updates, regardless of whether changes have been made. Therefore, the original and current years of issue are not included in the table. To locate a specific standard, use the ‘Ctrl’ and ‘F’ keys.
| Std Number | Title |
|---|---|
| General | |
| ASTM A450 | Specification for General Requirements for Carbon, Ferritic Alloy, and Austenitic Alloy Steel Tubes |
| ASTM A480 | Specification for General Requirements for Flat-Rolled Stainless And Heat-Resisting Steel Plate, Sheet and Strip |
| ASTM A484 | Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings |
| ASTM A555 | Specification for General Requirements for Stainless Steel Wire and Wire Rods |
| ASTM A999 | Specification for General Requirements for Alloy and Stainless Steel Pipe |
| ASTM A1016 | Specification for General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel and Stainless Steel Tubes |
| Flat Products | |
| ASTM A167 | Specification for Stainless and Heat-Resisting Chromium-Nickel Steel Plate, Sheet and Strip |
| ASTM A176 | Specification for Stainless and Heat-Resisting Chromium Steel Plate, Sheet, and Strip |
| ASTM A666 | Specification For Annealed or Cold-Worked Austenitic Stainless Steel Sheet, Strip, Plate and Flat Bar |
| ASTM A693 | Specification for Precipitation-Hardening Stainless And Heat-Resisting Steel Plate, Sheet and Strip |
| Long Products | |
| ASTM A276 | Specification for Stainless Steel Bars and Shapes |
| ASTM A314 | Specification for Stainless Steel Billets and Bars for Forging |
| ASTM A493 | Specification for Stainless Steel Wire and Wire Rods for Cold Heading and Cold Forging |
| ASTM A564 | Specification for Hot-Rolled And Cold-Finished Age-Hardening Stainless Steel Bars and Shapes |
| ASTM A565 | Specification for Martensitic Stainless Steel Bars, Forgings, and Forging Stock for High Temperature Service |
| ASTM A582 | Specification for Free Machining Stainless Steel Bars |
| Tubes & Pipes | |
| ASTM A182 | Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service |
| ASTM A268 | Specification for Seamless and Welded Ferritic Stainless Steel Tubing for General Service |
| ASTM A269 | Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service |
| ASTM A312 | Seamless and Welded Austenitic Stainless Steel Pipe |
| ASTM A358 | Electric Fusion Welded Austenitic Chromium Nickel Alloy Steel Pipe for High Temperature Service |
| ASTM A403 | Specification for Wrought Austenitic Stainless Steel Piping Fittings |
| ASTM A409 | Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High Temperature Service |
| ASTM A511 | Specification for Seamless Stainless Steel Mechanical Tubing |
| ASTM A554 | Specification for Welded Stainless Steel Mechanical Tubing |
| ASTM A632 | Specification for Seamless and Welded Austenitic Stainless Steel Tubing (Small-Diameter) for General Service |
| ASTM A731 | Specification for Seamless and Welded Ferritic Stainless Steel Pipe |
| ASTM A789 | Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Tubing for General Service |
| ASTM A790 | Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe |
| ASTM A813 | Specification for Single or Double Welded Austenitic Stainless Steel Pipe |
| ASTM A814 | Specification for Cold Worked Welded Austenitic Stainless Steel Pipe |
| Forgings | |
| ASTM A473 | Specification for Stainless Steel Forgings |
| ASTM A705 | Specification for Age Hardening Stainless and Heat Resisting Steel Forgings |
| Castings | |
| ASTM A297 | Specification for Steel Castings, Iron-Chromium and Iron-Chromium-Nickel, Heat-Resistant for General Application |
| ASTM A743 | Standard Specification for Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application |
| ASTM A744 | Standard Specification for Castings, Iron-Chromium-Nickel, Corrosion Resistant, for Severe Service |
| ASTM A890 | Standard Specification for castings, iron-chromium-nickel-molybdenum corrosion-resistant, duplex (austenitic/ferritic) for general application |
The above table originating from :
https://bssa.org.uk/bssa_articles/american-astm-standards-for-stainless-steels-for-general-applications/
In essence, grade of 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.
It is of utmost importance to seek the guidance of a professional expert when considering the selection of the appropriate grade of stainless steel pipe, particularly for new entrants in the stainless steel market. Foshan Vinmay Stainless Steel Co., Ltd. is your reliable source for expert advice and solutions regarding stainless steel pipes. Contact us today for your planing.
