Views: 2 Author: Site Editor Publish Time: 2025-08-27 Origin: Site
ASTM A403 is a stainless steel material standard developed by the American Society for Testing and Materials (ASTM), which specifies the material composition, manufacturing process, mechanical properties, and inspection requirements of stainless steel butt welded pipe fittings, ensuring the stable operation of ASTM A403 butt weld fittings in harsh scenarios such as high pressure and corrosion resistance.
Material: ASTM A403 / ASME SA403
Standard: ASME/ANSI B16.9, ASME B16.28, MSS-SP-43
Size: NPS 1/8″ to 48″ . (Seamless & 100% X-Ray Welded, Fabricated)
Type: Seamless / Welded / Fabricated
Thickness: Sch 5s, Sch 10s, Sch 40s, Sch 80s, Sch 160s, Sch XXS
Dimension: ASTM A403 butt weld fittings cover nominal diameters ranging from DN15 (1/2 inch) to DN1200 (48 inches), meeting the size requirements of various piping systems;
Wall thickness: Designed in accordance with ANSI B16.9 standard, including commonly used stainless steel wall thickness specifications such as SCH 10S, SCH 40S, SCH 80S, as well as wall thickness specifications for high-pressure environment testing, to ensure that the pressure bearing capacity of the fittings matches the pipeline.
The ASTM A403 standard also provides clear requirements for the welding quality, surface treatment (such as pickling and passivation), non-destructive testing (such as X-ray inspection and hydrostatic testing), and other aspects of stainless steel butt welded pipe fittings to avoid safety hazards caused by pipe defects.
The ASTM A403 standard for stainless steel butt weld fittings is divided into multiple "WP grades" based on the composition and performance differences of the materials. Different grades correspond to different corrosion and high temperature resistance capabilities, meeting diverse industrial needs. The common types of materials are as follows:
WP304/304L: The most commonly used austenitic stainless steel, containing 18% chromium and 8% nickel, has excellent resistance to neutral corrosion (such as fresh water and steam) and room temperature oxidation resistance. Among them, 304L has a carbon content of ≤ 0.03%, which is more suitable for welding scenarios than 304 and can reduce the risk of intergranular corrosion in the welding area. It is suitable for industries with lower corrosion requirements such as food processing and municipal water supply.
Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr |
| ASTM A403 WP304 | MIN | 8.0 | 18.0 | |||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 11.0 | 20.0 | |
| ASTM A403 WP304L | MIN | 8.0 | 18.0 | |||||
| MAX | 0.03 | 2.00 | 0.045 | 0.030 | 1.00 | 11.0 | 20.0 |
Mechanical Properties
| MATERIAL | ASTM A403 WP304 | ASTM A403 WP304L |
| T.S (MPA) | 515 min | 485 min |
| Y.S (MPA) | 205 min | 170 min |
| EL % | 28 min | 28 min |
WP316/316L: Adding 2% -3% molybdenum element on the basis of 304 significantly improves its corrosion resistance, especially able to resist strong corrosive media such as seawater, hydrochloric acid, sulfuric acid, etc. At the same time, its high temperature resistance (870 ℃) is better than the 304 series. 316L is a low-carbon version (carbon content ≤ 0.03%) with better welding performance. It is a major material in the petrochemical, marine engineering, and pharmaceutical industries, and can cope with harsh working conditions such as high salt and high acid.
Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo |
| ASTM A403 WP316 | MIN | 10.00 | 16.00 | 2.00 | |||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 14.00 | 18.00 | 3.00 | |
| ASTM A403 WP316L | MIN | 10.00 | 16.00 | 2.00 | |||||
| MAX | 0.03 | 2.00 | 0.045 | 0.030 | 1.00 | 14.00 | 18.00 | 3.00 |
Mechanical Properties
| MATERIAL | ASTM A403 WP316 | ASTM A403 WP316L |
| T.S (MPA) | 515 min | 485 min |
| Y.S (MPA) | 205 min | 170 min |
| EL % | 28 min | 28 min |
WP321/347: It belongs to stabilized austenitic stainless steel, with the addition of titanium (Ti) and niobium (Nb) elements, which can effectively suppress the formation of chromium carbide by the combination of carbon and chromium in high-temperature environments (400-800 ℃), avoiding intergranular corrosion. Among them, WP321 is suitable for high-temperature scenarios such as aerospace and boiler pipelines, while WP347 is more suitable for pipeline systems that are subject to long-term fluctuating temperatures (such as auxiliary pipelines in nuclear power plants) due to the stability of niobium elements.
Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Ti | Nb |
| ASTM A403 WP321 | MIN | 9.00 | 17.00 | 5*(C+N) | ||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 12.00 | 19.00 | 0.70 | ||
| ASTM A403 WP347 | MIN | 9.00 | 17.00 | 8*C | ||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 12.00 | 19.00 | 1.10 |
Mechanical Properties
| MATERIAL | ASTM A403 WP321 | ASTM A403 WP347 |
| T.S (MPA) | 515 min | 515 min |
| Y.S (MPA) | 205 min | 205 min |
| EL % | 28 min | 28 min |
In addition, ASTM A403 butt weld fittings also include high-temperature resistant stainless steel materials such as WP309S and WP310S, which can be adapted to high temperature industrial scenarios above 1000 ℃ (such as metallurgy and incinerator pipelines), providing professional solutions for special working conditions.
Chemical Composition
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr |
| ASTM A403 WP309 | MIN | 12.00 | 22.00 | |||||
| MAX | 0.20 | 2.00 | 0.045 | 0.030 | 1.00 | 15.00 | 24.00 | |
| ASTM A403 WP310S | MIN | 19.00 | 24.00 | |||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 22.00 | 26.00 |
Mechanical Properties
| MATERIAL | ASTM A403 WP309 | ASTM A403 WP310S |
| T.S (MPA) | 515 min | 515 min |
| Y.S (MPA) | 205 min | 205 min |
| EL % | 28 min | 28 min |
ASTM A403 butt weld fittings can be classified into butt welded elbows, tees,cross, reducers, and caps according to their structure and function. Each type of pipe fitting needs to be connected to the pipeline through butt welding process to ensure interface strength and sealing.
Used to change the flow direction of pipelines, common angles are 45 °, 90 °, and 180 °. According to the curvature radius, it can be divided into long radius elbows (R=1.5D, D is the nominal diameter) and short radius elbows (R=1.0D). Long radius elbows have low fluid resistance; Short radius elbows take up less space.
Used for pipeline branching or fluid distribution, it is divided into equal diameter tees and reducing tees. ASTM A403 stainless steel tees are manufactured using integral forging or pressing processes, with smooth transitions between branch and main pipes, reducing fluid impact and avoiding excessive local pressure.
Used to connect pipes of different diameters, it is divided into concentric reducers and eccentric reducers. Concentric reducers are suitable for vertical pipelines or scenarios that require high fluid stability; Eccentric reducers can prevent gas accumulation at the top or liquid accumulation at the bottom of the pipeline.
Used for sealing at the end of pipelines to prevent fluid leakage or external contamination inside the pipeline, it can be divided into elliptical pipe caps, circular pipe caps, and conical pipe caps according to their shapes.
In the procurement of industrial pipe fittings, ASTM A403 and ASTM A234 are often compared. Although both are standards for butt welded pipe fittings, they also have essential differences.
Different applicable materials: This is the most crucial difference - ASTM A403 is only applicable to stainless steel materials, covering austenitic stainless steels such as 304, 316, 321, 310, etc; ASTM A234 is mainly applicable to carbon steel and alloy steel, such as WPC, WPB carbon steel, WP91, WP92 alloy steel.
Different application scenarios: Due to differences in material properties, ASTM A403 fittings focus on corrosion resistance and high cleanliness scenarios, such as food and pharmaceutical, marine engineering, and chemical anti-corrosion pipelines; ASTM A234 fittings focus on high-pressure and high-temperature conventional industrial scenarios, such as thermal power generation, oil transportation (non corrosive crude oil), and steam pipelines. Due to the high strength advantage of its carbon steel/alloy steel material, it is more suitable for withstanding high-pressure loads.
Different performance requirements: ASTM A403 has stricter requirements for the corrosion resistance of stainless steel, which requires passing intergranular corrosion tests, pitting corrosion tests, etc; ASTM A234 focuses more on the mechanical properties of carbon steel/alloy steel, such as tensile strength, yield strength, and impact toughness, and has lower requirements for corrosion resistance testing.
Compared to ordinary carbon steel pipe fittings, ASTM A403 butt weld fittings have five core advantages:
Super corrosion resistance and longer service life: relying on strict control of material composition according to ASTM A403 standard, the pipe fittings can resist various corrosive media such as acid, alkali, salt spray, seawater, etc. The service life in chemical and marine environments can reach 15-20 years, which is 3-5 times that of ordinary carbon steel pipe fittings, greatly reducing the cost of pipeline replacement.
Excellent welding performance and more reliable interface: The standard clearly requires pipe fittings to use "butt welding connection", and the groove needs to be precision machined before welding. After welding, the interface strength is consistent with the pipe body, and can withstand high pressure, vibration and other working conditions, avoiding production losses caused by interface leakage.
High cleanliness and adaptability to strict industry standards: The surface treatment of ASTM A403 butt weld fittings must comply with food grade and pharmaceutical grade standards (such as electrolytic polishing and passivation treatment), with smooth inner walls and no burrs, which are not easy to breed bacteria or accumulate impurities. It can meet the high cleanliness requirements of industries such as food processing (such as dairy product transportation), pharmaceuticals (such as liquid medicine pipelines), semiconductors (ultra pure water transportation), etc.
High temperature/low temperature resistance, wide adaptability to working conditions: Different WP grade materials cover a temperature range of -270 ℃ (such as 304L low temperature working condition) to 1200 ℃ (such as 310S high temperature working condition), which can adapt to various scenarios from liquid natural gas (LNG) transportation to high-temperature incinerator pipelines, solving the pain points of "low-temperature brittleness and high-temperature deformation" of ordinary pipe fittings.
Standardized production and controllable quality: ASTM A403 standard has clear requirements for dimensional tolerances, wall thickness uniformity, and non-destructive testing (such as UT ultrasonic testing and RT radiographic testing) of pipe fittings. Each batch of pipe fittings must provide a material certificate (MTC) to ensure performance traceability, avoid "dimensional deviation and unstable performance" problems of non-standard pipe fittings, and reduce safety hazards in pipeline systems.
With excellent performance, ASTM A403 butt weld fittings have been widely used in multiple core industrial fields, becoming a key component to ensure the stable operation of pipeline systems:
Petrochemical industry
Food and pharmaceutical industry
Ocean engineering industry
water treatment industry
Energy and power industry
Aerospace and Semiconductor Industry
ASTM A403 butt weld fittings have become an indispensable core component in modern industrial pipeline systems due to their strict standard specifications, diverse material selection, and excellent performance advantages.
