6% Moly Alloy

6% Moly from Special Piping Materials

6% Moly is a less widely known metal that has proved itself to be indispensable in heavy industries such as the chemical processing industry and oil & gas market.

However, for those in the know, 6% Moly is relied upon time and time again for its unique set of advantageous properties such as its super strength and ability to withstand extremely high temperatures.

As an overview, 6% Moly is a superaustenitic stainless steel which contain at least 6% molybdenum. Different Moly alloys will have different metallurgic compositions. For example, Alloy 6HN (UNS N08367) contains 6 weight percent more nickel (Ni) than alloy 254 (UNS S31254) and the increased nickel content means that the resultant allow has better corrosion resistance and added stability.

In general, 6% Moly alloys have exemplary resistance to a number of chemicals and are particularly appropriate for environments such as brackish water, seawater, pulp mill bleach plants that present a high chloride condition.

There are several typical manufacturing specifications including ASTM A213, ASTM A269, ASTM A312 and EN 10216.

History of 6% Moly

The element Molybdenum – which has the symbol Mo in the periodic table and the atomic number 42 – was discovered by Swedish Chemist Peter Jacob Hjelm. It was named after the Greek word ‘molybdos’ which means ‘lead’ and according to the Royal Society of Chemistry, was first announced in 1781.

Interestingly, it is not a naturally occurring free metal but when it is in this state it has the sixth-highest melting point of any element. Understandably then, one of the earliest practical applications of Molybdenum was in incandescent lamps.

The group of 6% Moly alloys was first created in the early 1970s because of a market demand for a cost-effective metal that was also able to be used in corrosive brackish water and seawater environments.

Why did 6% Moly originate?

‘Moly’ is an abbreviation of Molybdenum and a 6% Moly Alloy is a metal consisting of two or more metallic elements. Alloys are usually bonded in order to create a material that has heightened properties and benefits.

Molybdenum – which is a silver colour – is popular as a choice of alloying partner because it has a very high melting point. This means that it is regularly utilised in scenarios where the temperature is very high because it can withstand the heat and still perform as required.

When combined with another metal to create an alloy, molybdenum is stereotypically chosen due to its ability to increase strength, electrical conductivity and hardness as well as its capacity to defy wear and corrosion.

6% Moly Alloys are often found to have high levels of chromium and nitrogen which makes it even be able to withstand corrosion and stress cracking. They are part of the austenitic steel group which is one of the most widely used grade of stainless steel and is known for its good formability and resistance to corrosion.

Benefits of 6% Moly

Molybdenum has many helpful properties, notably high strength and mechanical stability. Even better than this it manages to keep those properties when the temperature gets hot.

Molybdenum has some attractive properties, particularly excellent strength and mechanical stability. It retains those credentials at extremely high temperatures, and it is both ductile and tough.

Specifically, 6% Moly is known for the following benefits and characteristics:

• Excellent thermal conductivity
• Excellent electrical conductivity
• Ability to bond with glass
• High density
• High melting point
• Very high resistance to chloride stress corrosion cracking (CSCC)
• Its material yield strength is 50% greater than 300-series austenitic stainless steels
• Very high melting point
• Highly resistant to chloride pitting, crevice and general corrosion
• Excellent impact toughness
• Excellent workability
• Excellent weldability

These properties mean that 6% Moly products, such a pipes, fittings and flanges, are in very high demand in industrialised, engineering and manufacturing markets. Indeed, specialist Mills around the world are high sought-after for the ability to produce this valuable material.

Applications of 6% Moly

A whole variety of different metals are required in the oil & gas, nuclear, desalination, LNG and energy markets. These metals have to be high-performing and are relied upon to be able to withstand harsh environments where there is often a high chance they will be exposed to toxic chemicals, corrosive sea salt and high temperatures and pressures.

Consequently, the need for high-performing materials that arises from these heavy industries have caused for new metals and alloys to be developed.

A whole suite of carefully balanced and blended high-quality metals has been created that have the necessary properties needed to cope in demanding environments.

Nickel alloy is particularly popular in the LNG market for its ability to keep natural gas at liquefaction temperatures, whereas 6% Moly is chosen for its ability to better resist crevice corrosion. This is because molybdenum is able to add resistance against localised pitting attacks means that the metal is able to resist the detrimental effects of chlorides.

Alongside the long list of benefits of 6% Moly comes an equally long list of applications. Understandably it is used frequently in corrosive and extremely hot environments but where exactly is it used? Here is an extensive list of applications where we have been aware of its use:

• Desalination Plants and equipment
• Paper and pulp Mill Bleach Systems; drums, vats and press rolls.
• Sea and Brackish Water pipelines
• Chemical process plants
• Seawater handling equipment such as heat exchangers and cooling water pipes
• Food processing equipment
• Flue gas desulphurization scrubbers
• Tall oil distillation columns and equipment
• Oil and gas production equipment
• Tanks and pipelines for various chemicals with high halide levels
• Flue gas desulphurisation units in power plants
• Tall oil distillation columns and equipment

6% Moly and Special Piping Materials

SPM can source and supply a whole variety of high-quality products in a range of industry specifications. For example:

• FLANGES – ASTM / ASME / A182 / SA182 / F44 / 6Mo / 1.4547 / 254SMO
• SMLS PIPE – ASTM / ASME / A312 / SA312 / UNS S31254 / 6Mo / 254SMO
• WELDED PIPE – ASTM / ASME / A358 / SA358 / UNS S31254 / 6Mo / 254SMO
• FITTINGS – ASTM / ASME / A403 / SA403 / UNS S31254 / 6Mo / 254SMO / F44
• BAR – ASTM / ASME / A182 / SA182 / F44 / 6Mo / 1.4547 / 254SMO
• PLATE – ASTM / ASME / A240 / SA240 / UNS S31254 / 6Mo / 254SMO

Be sure to contact your regional Special Piping Materials office today either in Aberdeen, Manchester, Dubai, Brazil, Texas, Perth or Singapore and speak to our knowledgeable sales teams about your requirement for specialised 6% Moly products.