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Steel has been used for making pipe fittings since years for its durability and strength. Moreover, steel offers high resistance to heat. Steel pipe fittings are widely used in industrial purposes and houses for carrying water, flammable gases, fire sprinkler systems, etc.

As steel pipes tend to rust, they are often mixed with other materials to add to its durability and make it rust resistant.

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Common materials used in pipe fittings:

Pipe fittings are made of various types of steel like Carbon Steel, Alloy Steel, Stainless Steel, Duplex/ Super Duplex, Nickel Alloy, etc.


Carbon Steel:

Carbon steel is much more durable and stronger than other varieties of steel, which makes it suitable for making pipe fittings. Also known as plain carbon steel, carbon steel is a malleable and iron-based metal, made by combining iron with between 0.02%-1.7% and small amounts of manganese and other elements. Steel is subjected to various processes and can either be cast to shape or wrought into various mill forms from which finished parts are formed, forged, stamped, machined or otherwise shaped. Carbon is the main hardening and strengthening element present in steel, which offers maximum hardness and strength; and decreased ductility and weld-ability.

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Based on carbon %, steel can further classify as

• Low carbon steel: in which Carbon is in range from 0.05% to 0.25%

• Medium Carbon Steel: in which Carbon is in range from 0.25% to 0.5%

• High Carbon Steel it is in range from 0.5% to less than 2%

Application of Carbon steel:

Fittings made of carbon steel are used in pipe systems that carry liquids or gases, such as oil, water, natural gas, or steam. Apart from that, carbon steel fittings are highly demanded in construction and maintenance activity in the residential construction, commercial construction, electric-power generation, petroleum refining, shipbuilding and other industrial-use sectors.

Galvanized Steel:

In order to protect steel from rust and corrosion, steel is coated in layers of zinc through a chemical process. Galvanized steel offers resistance to rust and corrosion and is highly preferred for making pipe fittings and pipe. Galvanized steel also increase the longevity of pipe fittings.

Fittings made of galvanized steel are available in standard sizes ranging from 8mm to 150mm.

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Application of Galvanized Steel:

Galvanized steel pipe fittings are for all types of piping inside a building. They are also used in water supply lines, but not in gas pipelines.

Low-alloy Steels

Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.

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For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.

As with steels in general, low-alloy steels can be classified according to:

• Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels

• Heat treatment, such as quenched and tempered, normalized and tempered, annealed

High-Strength Low-Alloy Steels

High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition

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The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce adequate formability and weld-ability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium and zirconium are used in various combinations.

Stainless steel:

Stainless steel is widely used for making pipe fittings because of the fact that it is highly resistant to oxidation and corrosion in various natural and man-made environments. Stainless steel is actually a ferrous alloy containing minimum 10% chromium. Selection of right grade of stainless steel for a particular application is really important. A range of pipe fittings like tees, unions, elbows, etc are made of stainless steel. Stainless steel fittings are usually used for household pipelines.

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Duplex Stainless Steel

Austenitic-Ferritic stainless steels, also called duplex stainless steels, were developed more than 70 years ago in Sweden for the paper industry in order to combat corrosion problems caused by chloride-bearing cooling waters and other aggressive chemical process fluids.

Due to the high content of chromium, nitrogen, and molybdenum, these steels offer good resistance to localized and uniform corrosion. The duplex microstructure contributes to the high mechanical strength, good abrasion, erosion and fatigue resistance. Duplex steels also possesses good weld-ability properties.

Typical applications of duplex stainless steel are:

• Pulp and paper industry

• Components for structural design

• Storage tanks

• Cargo tanks and pipe systems in chemical tankers

• Water heaters

• Flue-gas cleaning

• Heat exchangers

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Super Duplex Stainless Steel

First used in the 1980s, Super- Duplex refers to highly alloyed, high performance Duplex stainless steel with an improved pitting and crevice corrosion resistance.

Super duplex steels were designed for specific applications where both high mechanical strength and good corrosion resistance are required. Super Duplex Stainless Steel is noted for its high level of chromium, which gives the alloy excellent resistance to acid chlorides, acids, caustic solutions and other harsh environments.

Typical applications of duplex stainless steel are:

• Desalination plants • Heat exchangers

• Pollution control

• Pulp and Paper industry

• Tube & Pipe systems for petrochemical refineries

• Downhole

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Selection criteria for pipe fittings:

The pipe fittings “bodies” are most often of the same base material as the pipe or tube in which they are to be connected, e.g., steel, polyvinyl chloride (PVC), copper or other plastic or metal. Besides this, any material that is allowed by a code or a standard can also be used. For example, a pipe fitting made of brass is common in otherwise copper piping and plumbing systems. The materials of construction of pipe fittings must satisfy certain criteria like as follows:

• The material of construction must be compatible with the other materials in the system.

• It must be compatible with the fluids or solids being transported.

• It should withstand fluctuating temperatures inside and outside of the system.

• It should also be compatible with different pressure levels.

• Fire hazards, earthquakes, and other unforeseen factors also influence pipe fitting materials.

• Pipe fitting material specifications and construction are application-dependent.

• For optimization of component selection, user consultation with fitting suppliers is a must.

• The materials of construction should also conform to certain standards like BSP, NPT, ASME, ASTM, DIN, JIS etc.

• Surface finish is equally important. It is to be noted that all pipe fittings should have a proper finish as pipe fittings are constantly in harsh environments. Corrosion resistant property of the materials is an essential requirement.

ASTM International: American Society for Testing and Materials

This is one of the largest voluntary standards development organizations in the world. ASTM standards define the specific manufacturing process of the material and determine the exact chemical composition of pipe fittings, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by "Grade". This is a reputed scientific and technical organization that develops and publishes voluntary standards on the basis of materials, products, systems and services. This is a trusted name for standards. The standards covered by this organization covers various types of pipes, tubes and fittings, especially made of metal, for high-temperature service, ordinary use and special applications like fire protection. The ASTM standards are published in 16 sections consisting of 67 volumes.

UNS: Unified Numbering System

The Unified Numbering System (UNS) for identifying various alloys is also quoted. This is not a specification, but in most cases, it can be cross-referenced to a specific ASTM specification.

Alloy numbering systems vary greatly from one alloy group to the next. To avoid confusion, the UNS for metals and alloys was developed.

The UNS number is not a specification, because it does not refer to the method of manufacturing in which the material is supplied. The UNS indicates the chemical composition of the material. An outline of the organization of UNS designations follows:

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Some ASTM materials are compatible with specifications from other countries, such as BS (Britain), AFNOR (France), DIN (Germany), and JIS (Japan). If a specification from one of these other countries either meets or is superior to the ASTM specification, then it is considered a suitable alternative, if the project certifications are met.

Material Standard for Forged Fittings


A350 Gr.(LF1, LF2, LF3)

ASTM A182 Gr. (304, 304H, 309, 310, 316, 316L, 317L, 321, 347, 904L)

ASTM A182 Gr.(F 5, F 9, F 11, F 12, F 22, F 91)

ASTM A694 Gr.(F42, F46, F56, F52, F60, F65, F70)

ASTM A182 Gr.(F51, F52, F53, F54, F55, F57, F59, F60, F61),

UNS S31803, S32205, S32760, S32750

ASTM SB 336, ASTM SB 564 / 160 / 163 / 164 / 166 / 472, UNS 2200 (NICKEL 200) , UNS 2201 (NICKEL 201 ) , UNS 4400 (MONEL 400 ) , UNS 8020 ( ALLOY 20 / 20 CB 3 ) , UNS 8825 INCONEL (825) , UNS 6600 (INCONEL 600 ) , UNS 6601 (INCONEL 601) , UNS 6625 (INCONEL 625), UNS 10276 (HASTELLOY C 276)

ASTM SB 111 UNS No. C10100 , C10200 , C10300 , C10800 , C12000, C12200, C70600, C71500,

ASTM SB 466 UNS No. C70600 ( CU -NI- 90/10) , C71500 ( CU -NI- 70/30)

Material Standard for Butt-Welding Fittings


ASTM A420 Gr.(WPL3 , WPL6)

ASTM A403 WP( 304, 304H, 304L, 309, 310, 316, 316L, 317L, 321, 347, 904L)

ASTM A234 Gr. (WP1, WP5, WP9, WP11, WP12, WP22, WP91(

ASTM A860 Gr.(WPHY 42 - WPHY 46 - WPHY 52 - WPHY 56 - WPHY 60 - WPHY 65 - WPHY 70 - WPHY 80 only as per MSS-SP75)

ASTM A815 Gr.(UNS S31803, S32205, S32760, S32750)

ASTM SB336, UNS10276 (HASTELLOY C276), UNS2200 (NICKEL 200), UNS2201 (NICKEL 201), UNS4400 (MONEL 400), UNS8020 (ALLOY 20), UNS8825 (INCONEL 825), UNS6600 (INCONEL 600), UNS6601 (INCONEL 601), UNS6625 (INCONEL 625), UNS5500 (MONEL K500), UNS8800 (INCONEL 800), UNS8810 (INCONEL 800H)

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