Stainless steel is one of the most widely used metals
Stainless steel is one of the most widely used metals for construction materials. Due to its strength, versatility, and recyclability, stainless steel is the go-to metal choice for a variety of projects including architecture, landscaping, interior construction, and engineering.
In this article, we’ll discuss what stainless steel is used for, what it’s made of, types of stainless steel (focusing on the 300 and 400-grade series), and the many cost benefits when choosing your construction materials.
WHAT IS STAINLESS STEEL USED FOR?
Stainless steel is used in hundreds of industries including domestic, architectural, transport, medical, food and drink, and pharmaceutical. Its durability and strength make it ideal for everything from surgical instruments to industrial piping.
There are few industries where you won’t find stainless steel, and it is by far the most popular non-magnetic material option in commercial construction.
WHAT IS STAINLESS STEEL MADE OF?
Stainless steel is a low-carbon steel alloy containing an average of 18% chromium along with varying amounts of silicon and manganese. Chromium gives the steel its durability by hardening and increasing its corrosion resistance in high-heat or oxygenated environments. In some grades, nickel and molybdenum are also present to further increase corrosion resistance.
WHAT ARE THE TYPES OF STAINLESS STEEL?
Stainless steel is divided into five primary categories — all of which come in a variety of grades. The most popular are the 300 and 400 series. The five basic types of stainless steel are:
• Ferritic: Chromium-based with less than 0.10% carbon. Limited in use.
• Austenitic: The most common type of stainless steel with the addition of nickel, manganese, and nitrogen to increase weldability and formability.
• Martensitic: Similar to ferritic, but with a higher carbon concentration. It has high strength but lacks the corrosion resistance of austenitic steel.
• Duplex: Approximately 50% ferritic and 50% austenitic. It’s known for its high strength and resistance but is fragile during welding.
• Precipitation Hardening (PH): Comparable to austenitic steels given extremely high strength, with the additions of copper, niobium, and aluminum over an ‘aging’ heat treatment.
THE 300 SERIES
The 300 series is made of austenitic steel and offers versatility, corrosion resistance, strength, and extreme temperature resistance.
The most popular grade of the 300 series is Grade 304. Grade 304 is also known as 18/8 due to its composition of 18% chromium and 8% nickel. In addition to the standard benefits of austenitic steel, Grade 304 also showcases recyclability, long life, aesthetic appeal, substantial hygiene, and low maintenance. It also has a low-carbon version known as 304L.
Common uses of Grade 304 include refrigerators, dishwashers, and food processing equipment. It’s also found in chemical containers, heat transfer plates, and construction tools.
THE 400 SERIES
The 400 series is made of ferritic and martensitic stainless steel, with the additions of carbon, chromium, and manganese. It also boasts high strength and wear resistance.
The most popular grade of the 400 series is Grade 410. Grade 410 contains 11.5% chromium which makes it extremely strong following heat treatment. This grade is also magnetic when hardened, making it suitable for certain jobs the 300 series cannot do. Grade 410 also tends to be cheaper than Grade 304 due to its low alloy content.
Grade 410 is primarily used in the automobile industry and in part making for refineries and gas and steam components.
WHAT ARE THE COST BENEFITS OF STAINLESS STEEL?
Stainless steel will have a larger initial cost than lesser quality material. However, it’s been shown to have a lower cost over time than other materials due to its superior durability, corrosion resistance, heat resistance, tensile strength, and hygienic benefits.
CORROSION RESISTANCE
When chromium is added to stainless steel during the manufacturing process, it combines with oxygen in the air to create a thin protective film over the metal. This film can repair itself if damaged and allows stainless steel to resist corrosion, rust, water stains, and general wear. Any item you construct with stainless steel will have a longer shelf life than items made with inferior, corroding material
TEMPERATURE RESISTANCE
Depending on the grade, certain types of stainless steel can resist scaling and maintain strength at extremely high temperatures. Other varieties of stainless steel are designed to survive long-term cryogenic temperatures.
While not all grades show the same temperature resistance, there is stainless steel to meet the needs of nearly any environment.
TENSILE STRENGTH
All grades of stainless steel have extreme tensile strength. Both cold-hardened and heat-treated stainless are relatively lightweight despite their strength and durability. All grades have high shock resistance and can endure heavy loads.
HYGIENIC BENEFITS
Thanks to its chemical makeup, stainless steel naturally rejects the growth of bacteria and other pathogens. It’s also extremely easy to clean with a basic wipe down and an all-purpose cleaner. If you’re looking to go the extra mile, you can follow it up with an optional polish too. All the methods above make stainless steel a long-term and low-maintenance solution for hospital-grade tools, cutlery, pharmaceuticals, and other sanitary purposes.
Use these basic tests to identify meatal
Different metals come in a selection of grades, and pure metals are typically combined with supplementary elements to create a variety of alloys. But grade refers not only to the composition of your metal (i.e., its chemical makeup) but also to how your metal was manufactured and its mechanical properties. Of course, if you’re ordering a metal, this information is on the packaging. But what if you’re working with metals you aren’t familiar with?
There are seven common testing methods for determining the alloy composition of a certain metal. These tests are a great way to gain insight into your metal when you don’t have access to higher-end tools.
Even if you have access to XRFs (X-ray Fluorescence Analyzers) or LIBS (Laser-Induced Breakdown Spectroscopy), we recommend starting with these basic tests to narrow down your options and make more informed testing decisions.
1. Surface Appearance Test: The surface appearance test looks at any colors and marks on the surface of the metal. This test is not the most specific, but it can narrow down your metal options so that you know which follow-up tests will be the most beneficial.
One of the easiest determinations you make with a surface appearance test is in the oxidation levels. If you have to scrape away rust to see the original color of the metal, you’ll be able to compare the color of the oxidation with the color of the original metal and gain insight into the level of iron.
2. Spark Test: The spark test creates sparks from the metal by grinding it against a wheel. The length, color, and form of the sparks can indicate the family of metal. We’ll go deeper into the spark test for steel alloys below.
3. Chip Test: The chip test looks at the fragility and structure of a metal by using a chisel to break off a small piece. The size of the chip, the texture of the edges, and the smoothness of the chip itself can give great insight into the type of metal you’re dealing with.
4. Magnet Test: Perhaps the simplest of the tests, the magnet test determines whether or not a metal is magnetic by holding it to a magnet. It’s worth noting, however, that some stainless steels are not magnetic, so it’s not always a foolproof test on its own.
5. Torch Test: The torch test looks at the consistency of a metal once it’s melted, in addition to how fast that melting occurred. Depending on what you’re constructing, this is a crucial test, as it determines whether your metal is safe to use for your project.
6. Chemical Test: The chemical test is not applicable to all metals, but it is very useful in identifying steels, magnesium, and aluminum. Small amounts of phosphoric acid will show bubbling on low-chromium stainless steels, and silver nitrate will leave a black residue on magnesium (but not on aluminum).
7. Hardness Test: The hardness test (commonly referred to as the Rockwell Hardness Test) looks at the strength of a metal against a material trying to imprint against it. Each metal has a specific hardness number assigned to it, which corresponds to the level of impression. This makes the hardness test one of the most accurate metal identifiers.
