Part I: An Introduction to the World’s Most Popular Metal
“Stainless” steel is actually a generic term referring to a variety of steel types. Like all other kinds of steel, stainless steel is made primarily from iron and carbon in a two-step process. What makes stainless steel different is the addition of chromium (Cr) and other alloying elements such as nickel (Ni) to create a corrosion-resistant product.
Steel corrodes because iron, the metal used to make steel, occurs in nature in combination with other elements. When iron ore is artificially manipulated into a pure form to make steel, it becomes unstable and will readily recombine with oxygen.
When chromium is added to steel, it forms chromium oxide, which acts as a protective surface to prevent air and moisture from causing rust, as happens with ordinary steel. Chromium is added in quantities ranging from 10.5 to 30%, depending on the application or environment in which the steel is to be used. There are more than 100 different grades of stainless steel but they can be grouped into five major types:
Austenitic is the most widely used type of stainless steel. It has excellent corrosion and heat resistance with good mechanical properties over a wide range of temperatures. Austenitic steel is used in housewares, industrial piping and vessels, construction, and architectural facades.
Ferritic stainless steel has similar properties to mild steel (the most common steel), but better corrosion, heat, and cracking resistance. Ferritic steel is commonly used in washing machines, boilers and indoor architecture.
Martensitic stainless steel is very hard and strong, though it is not as resistant to corrosion as austenitic or ferritic grades. It contains approximately 13% chromium and is used to make knives and turbine blades.
Duplex stainless steel is a composite of austenitic and ferritic steels, making it both strong and flexible. Duplex steels are used in the paper, pulp, shipbuilding, and petrochemical industries. Newer duplex grades are being developed for a broader range of applications.
Martensitic or semi-austenitic steels can also be classified as precipitation hardening stainless steels. These steels are made to be extremely strong with the addition of elements such as aluminum, copper and niobium.
Corrosion resistance is the main advantage of stainless steel, but it certainly isn’t the only one. Stainless steel is also:
- High and low temperature resistant
- Easily fabricated
- Strong and durable
- Easy cleaned and maintained
- Long lasting, with a low lifecycle cost
- Aesthetically attractive
- Environmentally friendly and recyclable.
In addition to chromium, stainless steels are made with alloys of silicon, nickel, carbon, nitrogen, and manganese. Nitrogen, for example, improves tensile properties like ductility. Nickel is added to austenitic steel to improve flexibility. These alloys are added in varying amounts and combinations to meet specific end-use applications, which is why it’s very important for stainless steel manufacturers to verify that the correct percentages of each alloy are being used. There are two technologies that provide the elemental analysis needed to produce high quality stainless steel: X-Ray Fluorescence (XRF) and Optical Emission Spectroscopy (OES).
Handheld XRF and LIBS are highly valuable technologies in the scrap metal market. Stainless steel is 100% recyclable and therefore a huge amount of stainless steel must be evaluated at the scrap yard. Handheld XRF analyzers bring immense value to scrap metal recyclers because it is a highly accurate, nondestructive testing technique that can analyze a metal sample in seconds with little to no need for sample preparation. With XRF, stainless steel scrap can be quickly analyzed and sorted according to grade and type. Laser Induced Breakdown Spectroscopy (LIBS) is better for carbon analysis for metals and alloys.
OES is a robust, reliable, and widely-used technology for the analysis of metals and alloys in the lab. Compared with traditional combustion analyzers, OES provides faster elemental analysis with high precision and accuracy in iron and steel, aluminum, copper, magnesium, precious metals and other specialty metals/alloys. OES has demonstrated its capability to provide more efficient control of steel production by providing accurate sample analysis during the manufacturing process.
- Download our free eBook: A Practical Guide to Improving Steel Manufacturing Processes and Production Methods
- Read more about how the multitude of stainless steel grades are grouped into five primary classifications in our blog article: What is Stainless Steel? Part II
- Visit our center for Improving Steel Manufacturing Processes and Production
Editor’s Note: This article was previously published but has been refreshed and links updated.
Steel and Site says
Good information about stainless steel. It is an informative blog post for professionals in the steel industry.
Shaylee Packer says
I didn’t realize that stainless steel was created as a steel option that wouldn’t rust. We are looking to put some steel beams in the backyard. It seems like, as you mentioned, it would be best for us to get stainless steel. This way, it will last longer and stay looking nice.
Al Mutqan says
Great introduction about stainless steel metal fabrication.
Stainless steel is one of the material that is being used by all the industry for their equipment manufacturing.
Thanks for sharing the information.
Dorothy Marie Wood says
I must find out what alloy is possibly used in medical operations … stainless steel made with what alloys? Is it an industrial secret involving a patient allergic to Chromium and Nickel and possibly other metals specifically used in medical insertions into the body, securing bone breakage with screws. It should not be propietary under the circumstances a life is in jeopardy for a relatively simple break. .
sandeep singh says
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Rosie Beckett says
My little sister is competing in her first go-cart race in a few months, and one of the requirements to enter is to build your own car. She is thinking about using stainless steel fasteners to help keep the parts together, and I didn’t realize that steel has so many benefits! I really appreciate you explaining that stainless steel is strong and durable, so it won’t bend to the weight of large loads.
Great Point Rosie. We are huge fans of Stainless Steel, especially since we are located in the Florida Panhandle where humidity and saltwater is an issue for rust and corrosion.
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*Many people which are not from industrial backgrounds believe that stainless steel can’t get rusty and that stainless steel is completely rust-proof. In fact, although stainless steel is a metal that contains chromium and other elements offering a certain amount of resistance to corrosion the base material is virtually as active as ordinary carbon steel.
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Tuan Nguyen Huu says
Great! Thanks for sharing.
Great info Chris Burnett.
Hope your sister has a great experience there Rose. Stainless Steel is a great option for many uses, but for heavy duty parts (keeping the wheels on), you still might want to look at traditional steel bolts as they can have drastically different strengths.
Thanks for sharing. Lots of info and things to think about.
Well written article by Chris Burnett. Thank you. I keep forgetting about the benefits of Stainless Steel recycling and semi environmentally friendly. Great reminder.
Jeff Beeblebrox says
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