Understanding Stainless Steel Grades - Microsoft

1 Understanding Stainless Steel Grades Westlock Controls manufactures a number of control transmitters, network systems, control and position monitors in Stainless Steel to provide enhanced corrosion or oxidation-resistance in tough industrial environments. Stainless Steel derives its properties from its chemical composition, of which there are three key elements: Chromium: Stainless Steel contains a minimum of chromium because this level causes the spontaneous formation of a stable, transparent, passive, protective film. Increasing the level of chromium enhances corrosion resistance. Nickel: Adding nickel improves toughness, ductility and, where appropriate, weldability. Nickel increases resistance to oxidation, carburization, nitriding, thermal fatigue and strong acids. Molybdenum: Improves resistance to pitting and crevice corrosion in environments containing chloride and corrosion by sulfuric, phosphoric and hydrochloric acids. It also improves mechanical properties at elevated temperatures.

2 Stainless Steel designations There is a broad variety of designations for Stainless Steel Grades by different international testing and standards organisations worldwide. Each is based on the material's chemical composition and the most widely used is ASTM (American Society for Testing and Materials International). There are different designations for materials to be used for castings, such as enclosures, than those for components manufactured from bar/forged material, typically shafts and fasteners. Although the cast and bar versions are commonly used in combination because they provide similar performance, there are some chemistry differences, primarily to improve castability and soundness. Therefore, when specifying material for cast components it is inappropriate to use a designation such as type 316', when the correct specification would be type CF8M'. The table below shows the comparative designations for the most commonly used Stainless steels. Typical Stainless Steel Grades Key Castings Bar/Forging ASTM: American Society for Testing and Generic Description ASTM DIN UNS JIS ASTM DIN UNS JIS Materials International 18Cr - 8Ni A351 CF8 J92600 SCS13A A276 304 S30400 SUS 304 DIN: Deutsches Institut f r Normung UNS: Unified Numbering System 18Cr - 8 Ni - LC * A351 CF3 J92500 SCS19A A276 304L S30403 SUS304L.

3 JIS: Japanese Industrial Standards 18Cr - 9Ni - 2Mo A351 CF8M J92900 SCS14A A276 316 S31600 SUS316. 18Cr - 9Ni - 2Mo - LC* A351 CF3M J92800 SCS16A A274 316L S31603 SUS 316L. * Carbon less than Stainless Steel in Westlock Controls Type CF8M is the most widely used for Westlock Controls' enclosures as, with its bar equivalent type 316, it provides a good balance of corrosion resistance, availability, strength and cost. It also has excellent corrosion resistance in normal atmospheric conditions, including coastal exposure. It resists most water and brines at ambient temperature although seawater may cause pitting corrosion. Other variations of Stainless Steel are used for certain applications where a small compositional difference gives better performance to meet specific needs. Material with a low carbon content is generally used to avoid corrosion problems caused by welding and so is not relevant to cast components. Stainless Steel has several properties that can affect the application of the material, specifically: Fasteners Westlock Controls use fasteners made from various Stainless Steel materials with 304 being the most common and 316 being used to complement the CF8M Stainless Steel versions of our products.

4 Magnetism Although Stainless Steel 304, 316 and CF8M Grades are normally viewed as non-magnetic, they will all experience some degree of magnetism as a result of cold working or machining of the various components. Copyright Westlock. All rights reserved WESBUL-09080-US-1302.