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Stainless steel in the workplace
Stainless Steel
There are two main grades of stainless steel used: 304 and 316
Generally speaking 304 grade is used for product contact of dry components and 316 is used where liquid contact is involved.
Typical applications for 316 include boat fittings and structural members; architectural components particularly in marine, polluted or industrial environments; food and beverage processing equipment; hot water systems; and plant for chemical, petrochemical, mineral processing, photographic and other industries.
Corrosion Resistance
Grade 304 has excellent corrosion resistance in a wide range of media. It resists ordinary rusting in most applications. It is also resistant to most food processing environments, can be readily cleaned, and resists organic chemicals, dye stuffs and a wide variety of inorganic chemicals.
Grade 316 also has excellent corrosion resistance in a wide range of media. Its main advantage over grade 304 is its increased ability to resist pitting and crevice corrosion in warm chloride environments.
Neither 304 0r 316 should be cleaned with chlorine containing compounds.
What is stainless steel?
"Stainless" is a term coined early in the development of these steels for cutlery applications. It was adopted as a generic name for these steels and now covers a wide range of steel types and grades for corrosion or oxidation resistant applications.
Stainless steels are iron alloys with a minimum of 10.5% chromium. Other alloying elements are added to enhance their structure and properties such as formability, strength and cryogenic toughness. These include metals such as: Nickel, Molybdenum, Titanium and Copper
Non-metal additions are also made, the main ones being: Carbon and Nitrogen
The main requirement for stainless steels is that they should be corrosion resistant for a specified application or environment.
Making of stainless steel
Interestingly, the main source of raw material for making stainless steels is re-cycled scrap metal. This re-cycling route has been established for many years and the economics of the stainless steel making industry depend on recycling. Over 90% of new stainless steel is produced from recycled scrap.
As stainless steels are corrosion resistant alloys their life expectancy is usually long. A minimum of maintenance is needed and so, although more expensive initially, they offer attractive "life-cycle cost" benefits over alternatives such as carbon steels.
Stainless steels are easily cleanable and so an obvious choice for food and beverage manufacturing industries and catering equipment. There are no proven health risks from the normal use of stainless steels.
What makes stainless steel stainless ?
The one key element they all stainless steels share is a certain minimum percentage (by mass) of chromium: 10.5%. Although other elements, particularly nickel and molybdenum, are added to improve corrosion resistance, chromium is always the deciding factor
It is the better life cycle costs of stainless steel that make it attractive, both in terms of much longer service life, less maintenance costs, and high scrap value on de-commissioning.
Applications
Very large amounts of stainless steel are used in food production and storage. The most commonly used grades are 304 and 316. Very often in food production, stainless is used not because the food itself is corrosive but the use of stainless allows for faster and more efficient cleaning. One of the great advantages of stainless steel is that imparts no taste to the food with which it comes into contact.
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