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What is ASTM A312?

ASTM A312 is an American standard specification that covers seamless, longitudinally welded and re-cold processed austenitic stainless steel pipes used in high temperature and general corrosive environments.

In this article, we will explain the chemical and mechanical properties of the A312 specification.

stainless steel

ASTM A312 Stainless Steel Pipe

Stainless Steel Pipe for Corrosive High-Temperature Applications Stainless steel was developed to meet the growing demand for more durable steel that can withstand harsh working conditions in many industries.

Stainless steel is considered an evolution of standard carbon steel and is obtained by adding alloying elements such as nickel and chromium to the base iron.

Adding such alloying elements can improve the corrosion resistance of steel in severe applications. Before understanding the different grades, let us first review the types and classifications of stainless steel available on the market.


A312 steel Types of stainless steel

Generally speaking, any alloy steel containing at least 10.5% chromium can be regarded as stainless steel.

However, according to the mixing of alloying elements (Chrome, nickel), there are a variety of grades to choose from. Chromium, molybdenum, titanium, copper, nitrogen, etc.)

Each alloy has a specific chemical and mechanical structure and properties

The general properties of stainless steel are due to the outer layer of chromium oxide, which shows corrosion resistance.

This oxide acts as a microscopic protective layer that reacts with oxygen and prevents corrosion.

In addition, stainless steel alloys have better toughness, better strength and toughness, better ductility, and lower maintenance costs than carbon steel in low-temperature applications.

Stainless steel can be divided into several series,

Stainless steel piping

Austenitic stainless steel (300 series)

These are the most common stainless steel grades. The microstructure of austenitic stainless steel is obtained by adding nickel, manganese, and nitrogen, which impart weldability and formability to the alloy.

By increasing the percentage of chromium, molybdenum and nitrogen in the base alloy, the corrosion resistance can be further improved.

However, basic austenitic grades are prone to stress corrosion cracking (a higher percentage of nickel is required to improve stress corrosion cracking).

Austenitic stainless steel cannot be hardened by heat treatment, but it can be work hardened to high strength while maintaining reasonable strength and ductility.

Even though austenitic steels are generally non-magnetic, they can show some magnetism according to actual conditions. The alloy composition and work hardening given during the production process.


Austenitic stainless steel is divided into 200 series (chromium-manganese nickel alloy) and 300 series (304, 309, 316, 321, 347 and other chromium-nickel alloys).

304 stainless steel pipe is the most common austenitic stainless steel and is suitable for most corrosive applications. Any other grade in the 300 series improves the basic characteristics of SS304.

Martensitic stainless steels (400 series)

Martensitic stainless steels are similar to ferritic steels in that they both have a significant chromium content; however, martensitic steels have a higher carbon content, up to 1%.

The high carbon content allows martensitic steels to harden and reharden like standard carbon-chromium alloy steels (but generally exhibit low weldability and ductility).

This type of stainless steel is dedicated to high strength and medium corrosion resistance requirements. Unlike standard austenitic stainless steel, martensitic stainless steel is magnetic. Common martensite grades are 410, 420 ​​ , and 440C.


Ferritic stainless steel (SS430)

Ferritic stainless steel has a significant chromium content but low carbon addition (usually less than 0.1%).

The name of this series of stainless steel comes from the fact that its microstructure is very similar to carbon steel and low alloy steel. These steels have a wide range of applications, except for thin surfaces, because they have low corrosion resistance.

Welding or those that require formability application. (Ferritic steel has low formability and ductility). Ferritic stainless steel cannot be hardened by heat treatment.

By adding molybdenum to the ferrite grade, the steel can be used in highly corrosive applications such as desalination plants and seawater.

These steels also exhibit excellent resistance to stress corrosion cracking. Like martensitic steel, ferrite SS is magnetic.

The most common ferrite grades are 430 (17% chromium) and 409 (11% chromium), which are mainly used in the automotive industry.

astm a312 pipe welded

Due to the addition of elements such as copper, niobium, and aluminum to the alloy, precipitation hardening PH steel (PH 17-4) can show extraordinary strength.

Before the final aging treatment, these steels can be processed into very special shapes with high tolerance requirements. This is different from conventional quenching and tempering in which martensitic steel is deformed during processing.

The corrosion resistance of precipitation hardening steel is equivalent to that of standard austenitic steels such as SS304.  The most common precipitation hardening stainless steel is 17-4PH, which is 17% chromium and 4% nickel.

a312 ss tube

ASTM A312 pipe size

The standard stainless steel pipe size is defined by the ANSI ASME B36.19 specification.

The size range of seamless stainless steel pipes is 1/8 inch to 24 inches, and the manufacturing size of welded stainless steel pipes ranges from 2 inches to 36 inches

Is ASTM A312 pipe seamless?

ASTM A312 pipe, that is, austenitic-nickel austenitic stainless steel electrofusion welding, or A312 Is the pipe a seamless pipe? Pipe Specification A312 (grades 304/L and 316/L


This specification covers seamless, welded stainless steel straight welded pipes and heavy cold-processed pipes for general and high-temperature corrosion services. Or heavy cold-processed heat treatment of all pipes

Heat treatment

The heat treatment temperature of 304/L and 316/L must be provided under heat treatment conditions at a minimum of 1900°F (1040°C), then water cooling or rapid cooling.

Static pressure or non-destructive electrical test

Each pipe should be subjected to a non-destructive electrical test Or test.

The type of test used in hydrostatics will be selected by the manufacturer unless otherwise specified in the purchase order.

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