Materials - Coupling Information

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Couplings come in many types of materials including plastics, soft alloys, hardened alloys, stainless steels and rubber. The following is a brief description of some of the more common materials used in coupling manufacture.

12L14 Cold Rolled Steel

Also known as Lead Steel, it is easily machinable. Not weldable due to high sulphur content. Unhardened.

17-4 PH Stainless Steel 

Also known as 630 Stainless Steel containing 17% chromium and 4% nickel. Precipitation-hardening martensitic stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation-hardened to even higher strengths than the other martensitic grades.

303 Stainless Steel (A1)

303 is a free-machining stainless steel. The free-machining characteristics are provided by adding sulphur and/or selenium. Using 303 stainless steel can be more cost effective than using other stainless steels since 303 takes less time to machine, machine tool bits will last longer. 303 is similar to 304 grade (A2 or 18/8) but is easier to machine. 

304 Stainless Steel (A2, 18-8)

304 stainless steel is easy to machine and very widely used. Due to the wide usage, 304 stainless steel is usually cheaper than other grades when purchased in the unmachined form. It should always be remembered though, that finished machined parts have their own input costs. It can't be assumed that two similar sized components will be cheaper in 304 stainless than in 316 stainless simply because the base material cost is cheaper.

316 Stainless Steel (A4)

316 Stainless Steel is used when the product will be exposed to a highly corrosive environment. 316 stainless steel contains molybdenum. The nickel content is 10%. Molybdenum, in conjunction with chromium, provides superior resistance to corrosion due to chlorides. 316 stainless steel is subject to attack if very high levels of chlorine are used for extended periods of time.

316 stainless steel is non-magnetic. Its machinability is similar to 304 stainless steel, and its material cost is usually much higher than 303 or 304 stainless steel. 316 steel is used in the manufacture and handling of food and pharmaceutical products where it is often required in order to Minimise metallic contamination. It is also known as "marine grade" stainless steel due to its increased resistance to chloride corrosion compared to type 304.

400 Grades of Stainless Steel

Martensitic stainless steels, with lower chromium levels, no nickel, and high carbon content, these steels may be heat-treated to have favourable characteristics of high strength and toughness. Some common 400 grades include 416 and 440C. The material is magnetic and corrosion resistance is not as great as 300 grades.

416 Grade Stainless Steel

A magnetic mid grade alloy used for it's strength, durability and magnetic properties. It can be hardened, and is easy to machine due to additional sulphur.

440C Grade Stainless Steel

Contains more carbon which allows for much better edge retention when the steel is heat treated properly. It can be hardened to Rockwell 58 hardness, making it one of the hardest stainless steels. 440C grade is most often used in precision ball bearings, giving them hardness characteristics close to that of chrome steel and better corrosion resistance.

Aluminium

Light weight and easy to machine. It is relatively soft and is not recommended for supporting heavy loads.

Silver Steel

Nickel Plated Steel

Standard unhardened steel with a nickel plating for corrosion resistance and a shiny appearance.

Composition of Various Materials

The main component of these steels is Fe (Iron) with the addition of the elements shown in the following chart.

• C - Carbon
• Si - Silicon
• Mn - Manganese
• P - Phosphorous
• S - Sulphur
• Ni - Nickel
• Cr - Chromium
• Mo - Molybdenum

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