The material can be termed as a mixture of substances to compose a thing.

Lots of definitions of material have spread to our surroundings. But we will be discussed here the materials, that are eligible and being used for piping and welding. Materials can be classified into four main groups:

  • metals
  • polymers
  • ceramics
  • composites
  • Thermo plastic

Selection of materials

Selection and identification of the right type of material are essential in piping as well as welding. For the selection of the right material, there are three important factors to consider in piping and welding, as they can have a major impact on the material’s physical properties.

  • Pressure
  • Temperature and
  • Fluids properties

The codes applicable for the selection of each type of material are mentioned and followed by the manufacturing industry to ensure the ratio of the alloying elements in the material can be accurately ascertained.

Many international research organizations are working to make the process of material selection transparent and accurate. The codes and standards made by these organizations are followed all over the world.

Some of these important institutions which are followed in the piping industry are American Standard, British Standard, and Indian Standard respectively.

ASTM codes for Materials

ASTM Code for material, used in Pressure / Power Piping Industries, and Refrigeration are as follows:

SME codes for materials

ASTM codes for materials

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ASME code for pressure piping

  • ASME B31.1 – Power Piping.
  • ASME B31.2 – Fuel Gas Piping.
  • ASME B31.3 – Process Piping.
  • ASME B31.4 – Pipeline Transportation system for liquid hydrocarbon & other liquid.
  • ASME B31.5 – Refrigeration Piping.
  • ASME B31.8 – Gas transmission & distribution piping system.
  • ASME B31.9 – Building services piping.
  • ASME B31.11 – Slurry transportation piping system.

Types of material

Materials can be classified into two main parts, metals and non-metals. There are also two types of metals, which are called ferrous metals and non-ferrous metals, respectively, their classification can be understood according to the diagram.

Material

A substance, that can have various properties such as electrical and thermal conductivity, ductility, ductility, reflectivity, etc.

Some common materials used in piping and welding are discussed here:

Steel

steel is the most frequently used metal in piping due to its various characteristic, such as the ability to withstand pressure, temperature, ability to resist corrosion and erosion, etc.

Type of steel

Steel can be classified into four main parts

  • Carbon steel
  • Alloy steel
  • Stainless steel
  • Tool steel

Carbon steel is the most utilized metal worldwide, due to its flexibility, weldability, and productivity, it can be divided into 3 main parts based on carbon content.

  • Low carbon steel (up to o.25% carbon)
  • Medium Carbon steel (0.25-0.60 % carbn)
  • High carbon steel (0.60-1.5% carbon)

Alloy steel

Alloy steel is med up by adding some particular element to achieve specific properties like to increase weldability, machinability, ductility, strength, hardness, etc.

manganesestrength/hardness increase but ductility and weldability will be decrease
Siliconsilicon works as a deoxidizer it used for steel killing purpose
Sulpherductility will be decrease but enough toughness and weldability will increase a little bit
Phosphorusstrength/hardness increase but weldability and ductility will decrease enough toughness will also decrease.
Copperthe resistance of corrosion increased
NickleHardenability and impact strength will be increased
MoHardenability will be increased and creep resistance will be improved
Some other elements also include in stainless steel like nickel, silicon for achieving various specific properties.

Stainless steel

When 11.5 % chromium is added to Iron, the surface of steel reacts with environmental oxygen and made a fine film of chromium oxide(Cr2O3).On the steel surface, that layer is called the passive layer, it makes the steel from corrosion. As this type of steel cannot be stained easily, it is called stainless steel.

Claffication of Stainless steel

Stainless steel can be classified as follows:

  • Ferritic stainless steel
  • Martensitic stainless steel
  • Austenitic stainless steel
  • Duplex stainless steel
  • PH  stainless steel

Ferritic stainless steel

The crystal structure of Ferritic stainless steel (BCC-Body centered cube). This type of steel is magnetic and has good ductility, it can not be hardened by heat treatment.it can be strengthened by cold working. The chemical composition of ferritic steel is as follows:

C0.08-0.20%
Mn1-1.5%
Si1%
Cr11-27%

Application of ferritic stainless steel

  • Interior decorative service
  • Screws and fittings
  • Parts of oil burner
  • Lining for petroleum industries.

Martensitic stainless steel

Martensitic stainless steel is extremely strong, tough, and machinable steel, is also corrosion-resistant. Due to the higher carbon to chromium ratio, this steel is the only type hardenable by heat treatment. Martensitic stainless steel is magnetic in all conditions and posses the best thermal conductivity. The chemical composition of Martensitic stainless steels are as follows:

C0.15-1.2%
Mn1%
Si1%
Cr11-18%

Application of Martensitic stainless steel

  • Rules and tapes
  • Pumps parts
  • Turbine buckets
  • Valve parts
  • Surgical instruments,etc.

Austenitic stainless steel

 The structure of Austenitic stainless steel face-centered cube (fcc), this type of steel is high corrosion resistance steel. this steel is nonmagnetic that mean, these type of steels can not be tested by mp(magnetic particle test). the weldability is high. The chemical composition of Austenitic stainless steel is as follows:

C0.03-0.25%
Mn2-10%
Si1-2%
Ni3.5-22%
Cr16-26%
P and SNormal

Application of Austenitic stainless steel

  • Engine parts of aircrafts
  • Heat exchengers
  • Food procesing tans
  • Cooking utensils,etc.

Duplex stainless steel

Duplex stainless steel has a two-phase microstructure that means both structures of ferritic and austenitic steels are mixed here thus duplex steel is a mixture of ferrite and austenite. so due to the mixture of both sheets of steel the duplex steel is merely two times stronger than both.

PH  stainless steel

Precipitation Hardening Stainless Steels are made up of alloying elements, chromium, and nickel. The strength of this type of steel is ultra-high.

Tool steels

Tool steels contain a high amount of carbon content(0.5-1.5%) thus the hardness and strength of this steel are high. The use of tool steel is usually to made dies and tools. like cutting and drilling tools.