316 Seamless stainless steel pipe, 316 / 316L Stainless steel

What is 316 seamless stainless steel pipe?

316 Seamless stainless steel pipe refers to seamless pipe made of stainless steel 304 material. It is a stainless steel material with excellent corrosion resistance and high strength. "Seamless" refers to its seamless production process. Seamless stainless steel pipes are resistant to corrosion by weakly corrosive media such as air, steam, and water, as well as chemically corrosive media such as acids, alkali, and salts. They are also called stainless acid-resistant steel pipes.

The corrosion resistance of seamless stainless steel pipes depends on the alloy elements contained in the steel. Chromium is the basic element that makes stainless steel corrosion resistant. When the chromium content in steel reaches about 12%, chromium interacts with the oxygen in the corrosive medium to form a thin oxide film (self-passivation film) on the surface of the steel. , which can prevent further corrosion of the steel matrix. In addition to chromium, commonly used alloy elements for stainless steel seamless pipes include nickel, molybdenum, titanium, niobium, copper, nitrogen, etc. to meet the requirements for the structure and performance of stainless steel for various purposes.

316 stainless steel material:

316 stainless steel is a brand of stainless steel produced in accordance with American ASTM standards (ASTM A312). 316 is equivalent to China's 0Cr17Ni12Mo2 stainless steel. Japan also quoted the name of the United States and called it: SUS316.

Because 316 stainless steel is added with 2%-3% Mo, its corrosion resistance, atmospheric corrosion resistance and high temperature strength are particularly good. The high temperature resistance can reach 1200-1300 degrees and can be used under harsh conditions; it has excellent work hardening properties. (Non-magnetic); excellent high-temperature strength; non-magnetic in solid solution state; cold-rolled products have good gloss and beautiful appearance; compared with 304 stainless steel, 316 is more expensive.

Specifications of 316 stainless steel pipes:

The specifications of 316 stainless steel pipes are a series of codes composed of factors such as size, pipe type, surface treatment, etc. The following are some common specifications of 316 stainless steel pipes:

316L-TP316L-SMLS-10S-6M
316L-TP316L-WELD-10S-3M
316L-TP316L-SMLS-40S-4M
316L-TP316L-WELD-80S-5M

In the above codes, "L" stands for low carbon content, "TP" stands for pipe material, "SMLS" stands for seamless pipe, "WELD" stands for welded pipe, "10S, 40S, 80S" stands for thickness grade, and "6M, 4M, 5M" stands for length grade.

Chemical composition of 316 stainless steel:

Carbon C≤0.08,
ManganeseMn≤1.5,
SiliconSi≤1.5,
Phosphorus P≤0.04,
Sulfur S≤0.04,
Chromium Cr 18.00-21.00
Nickel Ni 9.00-12.00,
Molybdenum 2.00-3.00

Heat treatment:
Melting point: 1375~1450℃
Solid solution treatment: 1010~1150℃

Metallographic structure: The structure is characterized by austenitic structure

Usage: 

SUS316 stainless steel is suitable for use in seawater equipment, chemical, dye, papermaking, oxalic acid, fertilizer and other production equipment; photography, food industry, coastal area facilities, ropes, CD rods, bolts, nuts, etc.

316 seamless stainless steel pipe production process:
316 seamless stainless steel pipes are made from steel ingots or solid tube blanks that are perforated into capillary tubes, and then hot rolled, cold rolled or cold drawn. The production process mainly includes smelting, rolling, piercing, straightening, cutting and other links. Each link has its specific requirements and operating specifications. Only by strictly following the requirements can high-quality 316 stainless steel seamless pipes be produced.

316 stainless steel vs 316L stainless steel:

1. Different ingredients
316l is ultra-low carbon, and l means low carbon, so the carbon content of 316l material is lower than that of 316 material. 316 stainless steel contains 0.08% carbon, while 316l stainless steel only contains up to 0.03% carbon.

Secondly, the contents of other alloying elements in 316 and 316l are also different. 316l stainless steel contains higher molybdenum and nickel elements than 316 stainless steel, while 316 stainless steel contains higher chromium elements.

2. Different heat resistance
316 material can be used intermittently below 1600 degrees, and continuously used below 1700 degrees, but it is best not to use 316 stainless steel in the range of 800-1575 degrees. However, when 316 stainless steel is used continuously outside this temperature range, the stainless steel has good heat resistance.

The resistance to carbide precipitation of 316l stainless steel is better than that of 316 stainless steel, and it can also be used in the temperature range of 800-1575 degrees.

3. Different corrosion resistance
The Mo content of 316l makes this steel type have excellent corrosion resistance and can be safely used in environments containing halogen ions such as chloride ions. Therefore, 316l stainless steel has excellent corrosion resistance. 316 stainless steel is resistant to corrosion from the ocean and corrosive industrial atmosphere.

4. Different welding methods
The welded section of 316 stainless steel requires post-weld annealing treatment to improve its corrosion resistance. But if 316l stainless steel is used, there is no need for post-weld annealing.

5. Different application scopes
In the industrial field, 316l stainless steel is suitable for petroleum, chemical industry, shipbuilding and other fields under high temperature and strong corrosion environment. 316 stainless steel is mostly used in general corrosive environments such as tableware, construction, and chemical industries.

Features and advantages of 316 seamless stainless steel pipe:

‌316 austenitic seamless stainless steel pipe has the following significant features compared with traditional iron pipes and ordinary stainless steel materials:

1.‌ Corrosion resistance‌
‌316 seamless stainless steel pipe contains molybdenum element,‌which makes it have better corrosion resistance,‌especially in highly corrosive environments such as marine environment, industrial waste gas and chemical media. ‌The addition of molybdenum improves the corrosion resistance of stainless steel in seawater and other chloride solutions, ‌ making it resistant to chloride ion erosion, ‌ avoiding the occurrence of pitting corrosion and crevice corrosion. ‌This is mainly due to the formation of a stable passivation film on its surface, which can effectively prevent oxidation from proceeding.

2. Welding performance‌
316 seamless stainless steel pipe has good welding performance and can maintain good mechanical properties even without annealing after welding. This is especially important for applications that require frequent welding. ‌

3. Mechanical strength‌
‌316 seamless stainless steel pipe has high mechanical strength, ‌ can withstand high pressure and heavy load, ‌ is not easy to deform and break, and is suitable for applications that require high-strength materials. ‌ Its high strength and corrosion resistance make 316 stainless steel seamless pipe widely used in petroleum, ‌ chemical, ‌ medical, ‌ food processing and other industries. ‌

4. Beautiful and durable
‌316 seamless stainless steel pipe also has excellent surface treatment properties and can be polished, ‌drawn or sandblasted as needed to improve its aesthetics and corrosion resistance. 316 stainless steel pipes are not easy to rust or discolor after long-term use, and maintain long-lasting luster and good appearance. ‌These characteristics make 316 stainless steel seamless pipe a high-quality metal material with wide application prospects.

5. Environmentally friendly
316 stainless steel pipes can be recycled and reused, which is conducive to environmental protection and sustainable development.

Application fields of 316 seamless stainless steel pipe:

Due to its excellent performance, 316 seamless stainless steel pipe is widely used in the following fields:

1. Oil and gas industry: used to manufacture pipelines, storage tanks and valves, etc., with high strength and good corrosion resistance.
2. Chemical industry: used to manufacture reactors, heat exchangers and pipelines, etc., and can withstand corrosion from various chemical media.
3. Marine engineering: used to manufacture ship pipelines, seawater desalination equipment and offshore platform structures, etc., which can work stably in the marine environment for a long time.
4. Food industry: used to manufacture fluid delivery pipes, storage tanks and containers, etc., meeting food hygiene requirements.
5. Other fields: such as construction, medical and aerospace, etc., applied according to specific needs.

In short, 316 seamless stainless steel pipe, as a high-quality metal material, has wide application prospects. Understanding its characteristics, applications and production processes will help to better promote and use this excellent stainless steel product.

Read more: Carbon steel vs Stainless steel or 304 Seamless stainless steel pipe