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When it comes to stainless steel, there is a lot to consider. In this article we cover:
What is stainless steel?
What are grades of stainless steel?
Stainless steel grades and stainless steel grade chart
Comparing stainless steel grades
First, let's look at what a stainless steel is. They’re iron-based alloys, containing at least 10.5% chromium. The chromium protects the iron and prevents rusting, a property known as passivation.
"Stainless” isn’t an entirely accurate description. It’s more stain resistant than stainless. The different grades of stainless steel will eventually break down. Stainless-steel tarnish, depending on the grade, can take years to develop, so stainless steel is still a great material if corrosion resistance is what you’re looking for. These are the factors which affect the stainless steel grade.
No. The alloys are melted into the steel itself. Stainless steels are comprised of different combinations of various metals. The next question might be, “What’s the best grade of stainless steel?” Stainless-steel grades and stainless steel applications go hand in hand. Choosing the right one comes down to determining which alloy will work best for your application.
Family
Weldability
Ductility
High-temp resistance
Austenitic stainless steel
High
High
High
Ferritic stainless steel
Low
Medium
High
Martensitic stainless steel
Low
Low
Low
Duplex stainless steel
High
Medium
Low
Precipitation hardening stainless steel
Low
Medium
Low
Family
Summary
Characteristics
Use
Austenitic stainless steels
-Contains a minimum of 16% chromium and 6% nickel
-Most widely used stainless steels in the world
-Excellent corrosion resistance
-Excellent performance at both high and low temperatures
-Non magnetic when annealed
-Superb hygienic qualities with outstanding cleanability
-Common to food and healthcare applications
-Popular for manufacturing outdoor enclosures
Ferritic stainless steels
-Amount of chromium ranges between 10.5% to 18%
-Low nickel content (up to 1%) makes it especially cost effective
- Lower thermal expansion coefficient and higher thermal conductivity than austenitic stainless steel
-Good corrosion resistance
-Magnetic
-Resists stress corrosion cracking
-Excellent for applications involving heat transfer, such as cooking utensils
-Also popular in the automotive industry for exhausts and fuel lines
Martensitic stainless steels
-Chromium content ranges between 10.5% and 18%, with 0.15% carbon and 0.1% manganese
- Carbon content enables tempering and hardening
-Corrosion resistance in mild environments
-Magnetic
-Inability to be cold formed
-Knife blades
-Surgical instruments
-Razor blades
Duplex stainless steels
-High chromium and low nickel content
-Combines the best of the austenitic and ferritic families
-Annealed structure is 50% austenitic and 50% ferritic
-Low nickel content means low cost
-Excellent pitting-and-crevices corrosion resistance
-High resistance to stress corrosion cracking
-High yield strength
-Poor formability and machinability
-Magnetic
-Heat exchangers
Also used in:
-Off-shore oil and gas installations
-Chemical and petrochemical plants
Precipitation hardening stainless steel
-Contains 17% chromium and 4% nickel
-Strength can be developed by adding titanium, aluminium and other alloys
-Good to excellent corrosion resistance
-Can develop high strength with simple heat treatments
-Welding can reduce corrosion resistance by over-aging and sensitisation
-Magnetic
-Nuclear waste casks
-Turbine blades
Also used in:
-Aerospace industry
-Pulp-and-paper industry equipment
What does 304 mean in stainless steel? It’s the grade. Within the families are grades, each with specific properties. The grades are not about stainless-steel quality – each is formulated for a purpose – and not all grades are right for every application. The best stainless steel for manufacturing kitchen appliances won’t be the best for ball bearings.
A word about standards: The American Iron and Steel Institute (AISI) and the Society of Automotive Engineers (SAE) each devised steel specifications for years, which were often interchangeable. Due to the similarities, they were combined into one, overlapping AISI/SAE system. The AISI designation is no longer officially used, but the name is still used informally. EN are the standard for European stainless-steel grades, though AISI/SAE is extremely popular.
Below includes the composition of stainless-steel grades.
Designations
Chemical Composition AISI-Type/SAE & EN Standards (Major elements only) % content is a maximum unless a range is indicated
AISI-type/ SAE
EN
C, ≤
Mn, ≤
P, ≤
S, ≤
Si, ≤
Cr
Ni
Mo
N, ≤
Other Elements
≤, UOS
Austenitic stainless steel
302
1.4324
0.15
2.00
0.045
0.03
0.75
17.0-19.0
8.0-10.0
–
0.10
–
303
1.4305
0.15
2.00
0.2
≥0.15
1.00
17.0-19.0
8.0-10.0
–
–
–
304
1.4301
0.08
2.00
0.045
0.03
1.00
18.0-20.0
8.0-11.0
–
–
–
304L
1.4307
0.03
2.00
0.045
0.03
1.00
18.0-20.0
8.0-11.0
–
–
–
308
1.4303
0.08
2.00
0.045
0.03
1.00
19.0-21.0
10.0-12.0
–
–
–
310
1.4845
0.25
2.00
0.045
0.03
1.5
24.0-26.0
19.0-22.0
–
–
–
316
1.4401
0.08
2.00
0.045
0.030
1.00
16.0-18.0
10.0-14.0
2.00-3.00
–
–
316L
1.4404
0.03
2.00
0.045
0.030
1.00
16.0-18.0
10.0-14.0
2.00-3.00
–
–
317
1.4449
0.08
2.00
0.045
0.03
1.00
18.0-20.0
11.0-15.0
3.0-4.0
0.1
–
321
1.4541
0.08
2.00
0.045
0.03
1.00
17.0-19.0
9.0-12.0
–
0.10
≥ Ti 5×(C+N), ≤ 0.70
347
1.4550
0.08
2.00
0.045
0.03
1.00
17.0-19.0
9.0-12.0
–
–
≥ Cb 10 × C, ≤ 1.00
904L
1.4539
0.02
2.00
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0.045
0.035
1.00
19.0-23.0
23.0-28.0
4.00-5.00
0.1
Cu 1.00-2.00
Martensitic stainless steels
409
1.4512
0.030
1.00
0.040
0.015
1.00
10.50-12.50
–
6 x (C+N) to 0.65
–
430
1.4016
0.12
1.00
0.04
0.03
1.00
16.0-18.0
–
–
–
–
430F
1.4105
0.12
1.25
0.06
≥0.15
1.00
16.0-18.0
–
–
–
–
444
1.4521
0.025
1.00
0.04
0.03
1.00
17.5-19.5
1.00
1.75-2.50
0.035
Ti+Cb 0.20+4 × (C+N)-0.80
Martensitic stainless steels
410
1.4006
0.08-0.15
1.00
0.04
0.03
1.00
11.5-13.5
–
–
–
–
416
1.4005
0.15
1.25
0.06
≥0.15
1.00
12.0-14.0
–
–
–
–
420
1.4021
0.15, ≥
1.00
0.04
0.03
1.00
12.0-14.0
–
–
–
–
431
1.4057
0.2
1.00
0.04
0.03
1.00
15.0-17.0
1.25-2.50
–
–
–
440A
1.4109
0.60-0.75
1.00
0.04
0.03
1.00
16.0-18.0
–
≤0.75
–
–
440B
1.4112
0.75-0.95
1.00
0.04
0.03
1.00
16.0-18.0
–
≤0.75
–
–
440C
1.4125
0.95-1.20
1.00
0.04
0.03
1.00
16.0-18.0
–
≤0.75
–
–
Duplex stainless steels
2205
1.4462
0.03
2.00
0.03
0.02
1.00
22.0-23.0
4.5-6.5
3.0-3.5
0.14-0.20
–
2304
1.4362
0.03
2.5
0.04
0.03
1.00
21.5-24.5
3.0-5.5
0.05-0.60
0.05-0.60
–
PH
15-5 PH / 631
1.4568
0.07
1
0.04
0.03
1
14.0-15.5
3.5-5.5
–
–
2.5-4.5 Cu; 0.15-0.45 Nb
17-4 PH / 630
1.4542
0.07
1
0.04
0.03
1
15.5-17.5
3.0-5.0
–
–
3.0-5.0 Cu; 0.15-0.45 Nb
Data is indicative only and not to be relied upon in place of full specification. Properties and values vary with temper, product and product dimensions. Consult with product manufacturer. No liability will be accepted.
Sometimes you’ll see 304 grade stainless steel referred to as 18/8. This refers to 304’s average composition of 18% chromium and 8% nickel. What is 18/10 stainless steel? Again, 18% chromium but this time, 10% nickel. This also meets the 304 stainless-steel standard.
But what about stainless-steel grades 18/10 vs. 18/8 when both fall within the 304 range?The additional nickel in 18/10 provides a bit more corrosion resistance and tolerance to heat.
Let’s look at some more comparisons, which will help you see how other alloys affect the grade.
These are the two most widely used stainless steels, with 304 grade stainless steel being the more popular. A large part of that has to do with economics. Stainless steel 304 is considered a medical stainless steel. Find out more in our guide, What is surgical steel?
The cost of stainless steel typically depends on the alloys involved, and a large proportion of those costs comes down to the chromium content. Now consider that 316 grade stainless steel contains a minimum 2.0% molybdenum. As good as 304 is at standing up to oxidation, 316 is more corrosion resistant, and better able to withstand harsh environments.
Molybdenum is also an expensive element, which makes 316 the more expensive grade. Whether you choose 304 or 316 stainless steel comes down to your application and budget.
Learn more about these two grades in our guide, 304 vs 316 stainless steel.
That minimum 2.0% molybdenum in grade 316 also gives it more strength than 304. Molybdenum strengthens and hardens steel, though its primary function is to stand up to corrosion from chlorides, such as salt.
These are also very similar. Stainless steel 304 has good oxidation resistance up to 1598˚F (870˚C) in intermittent service. In continuous service, it’s 1697˚F (925˚C). Fabrication methods, such as forging, require hot working. This occurs after uniform heating to 2100˚F - 2300˚F (1149 - 1260˚C).
Stainless steel 321 is essentially 304 stabilized by titanium additives. This reduces or prevents carbide precipitation during welding. It's also why stainless steel 321 is the preferred grade for applications when the range of temperatures doesn't exceed 1652˚F (900˚C). This combines high strength, scaling resistance and phase stability with corresponding aqueous corrosion resistance.
What is the difference between 304 and 430 stainless steels? They look very similar, except when it comes to the price tag. Stainless steel 430 costs less than 304 due to the composition. Whereas 304 stainless steel contains nickel, 430 stainless steel contains none. This not only makes 304 stainless steel more corrosion resistant, but also more expensive. If you're mulling over 304 stainless steel vs 430 stainless steel, then weigh the life span of your application against your budget to arrive at your decision.
Learn more about these two grades in our guide, 304 vs 430 stainless steel.
Grade 420 stainless steel has an extremely high tensile strength when hardened and stress relieved. Normally, 420 has a tensile strength of around 586 MPa. While this is high, it doesn't exceed that of 304, which is 621 MPa. However, when hardened and stress relieved, 420's tensile strength reaches 1,586 MPa – that's more than double 304 when annealed. Consequently, 420 is a better choice for heavy-duty applications. In fact, the 400 range includes the hardest grades.
Can you harden 304 stainless steel? These are austenitic steels, so none of these grades can be hardened by heat treatment. 304 stainless steel (or austenitic steels) hardness can be improved with work hardening, however. Also, a solution treatment or annealing can be done by rapid cooling after heating to 1850˚F - 2048˚F (1010°C - 1120°C).
These grades share 84% of their average alloy compositions. Grade 410 has 0% nickel, so it costs less than 304. It’s also popular for high-stressed parts and components, as they offer a combination of strength and corrosion resistance. Grade 304 is softer but has more corrosion resistance. Grade 410 is better, for instance, for making fasteners. Grade 304 is better, for example, for manufacturing a wider variety of products, from white goods to electrical cabinets.
To learn more about stainless steel for your enclosure design, you’ll also need to know about the components you’ll need. Check out our Quick Guide: Industrial Components for Outdoor Cabinets.
Download free CADs and request free samples, which are available for most of our solutions. It’s a great way to ensure you’ve chosen exactly what you need. If you’re not quite sure which product will work best for you, our experts are always happy to advise you. Whatever it is you need, you can depend on fast despatch.
Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.com or speak to one of our experts for further information on the ideal solution for your application 800-847-0486.
There are three things you have to consider when buying anything for your home: aesthetics, budget and lifestyle. Buying outdoor furniture is no exception. You want your outdoor furniture to fit your style and budget, and you need it to stand up to the elements and your family’s activities. Before you rush out on the next sunny Saturday to outfit your patio, back yard, deck or pool, here are some things to take into consideration.
● Buy outdoor furniture that is a natural extension of your indoor look and your house’s architectural style. If your house is modern, buy modern-style outdoor tables, chairs and chaises; if your house is like an English cottage, choose similar-styled outdoor furniture. Fortunately, there are myriad options that vary in color, shape, style and care. Whatever you do, always try out furniture before buying it: Comfort should be at the top of your criteria.
● Consider your budget. It is possible to find very inexpensive outdoor furniture, but realize that less-expensive furniture often does not wear as well. You will be better off buying the best-quality pieces you can afford. Like the major pieces inside your home, outdoor furniture is an investment.
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● Buy enough furniture to accommodate your family and guests. Also, supply enough shade for all, which might mean purchasing a few umbrellas with sturdy stands. (Look for weighted bases of at least 50 pounds.)
● Get cushions and pillows that are made with polyurethane foam, which, unlike polyester-filled cushions, allow water to literally flow through them. (Check out foamorder.com.) Also make sure cushions and pillows are covered in solution-dyed acrylic fabrics. These fabrics come in a huge variety of colors and patterns and are moisture-, mildew- and UV-protected so they won't fade (outdoorfabrics.com).
● If you don't have room to store your outdoor furniture in a garage or basement, buy proper covers now from either your furniture manufacturer or a company such as KoverRoos (koverroos.com). You will be happy to have them once the weather turns.
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● Make smart material decisions. Outdoor furniture tends to be made from three main materials: wood, synthetics and metal. The style of furniture you choose will partly determine the material you choose, but your lifestyle will as well. The different materials require varying degrees of maintenance and care. They also have ranging levels of mobility — some are quite heavy while others are dainty and easily moved. Read on to pick the best material for you.
Wood: If you are the busy type who likes low-maintenance home purchases, choose teak furniture. Historically used in boat building, teak, a rain-forest wood, is hardy and resilient. Left outside, it weathers from brown to silvery gray and can last for up to 100 years. (To maintain teak's original brown color, apply a teak protector such as Golden Care's Teak Protector once or twice a year.) When buying teak furniture, look for a Forest Stewardship Council stamp, which lets you know that it was responsibly harvested.
Alternatively, look for eucalyptus or cedar furniture. Eucalyptus is less expensive than teak and can last almost as long, but it needs to be treated several times a year with a water-based acrylic sealant. Cedar (think classic picnic table) is the least expensive, but it will last only about 20 years. Cedar should be coated annually with protective oil.
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When buying any wood furniture, look for mortise-and-tenon construction, stainless-steel screws (they don’t rust), and dowels and pegs. Never buy furniture that has been glued or stapled.
Synthetics: Plastic furniture is the least expensive, but it's usually not as attractive or comfortable as other materials. An exception is all-weather wicker, which is made of synthetic fibers that are woven around an aluminum frame. Whereas real wicker is not immune to moisture or sun damage, all-weather wicker can basically stay outdoors all year long. And it is easy to care for: Just hose it down with water and a mild soap. Look for pieces that are tightly woven — you should not be able to see through the weave.
Metal: The most common types of metal furniture are made from aluminum, wrought iron, stainless steel or powder-coated steel. There are varying qualities of aluminum furniture that determine weight, price and durability — tubular aluminum is the least expensive and lightest because it's hollow; cast aluminum is the most expensive and heaviest. Either, however, is a good pick because aluminum is rustproof. Look for furniture that has rustproof hardware, seamless welds and a powder-coated finish to prevent oxidation.
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Wrought iron, like cast aluminum, can be expensive and very heavy. Make sure that sets are powder-coated to prevent rusting, but watch out for scratches on the surface — they will rust. (If this happens, immediately sand the area and apply touch-up paint. ) Stainless or powder-coated steel sets are durable, moderately priced and easy to care for. One thing to remember: A glass top on any metal table should be tempered glass for safety.
Mayhew, a "Today" show style expert and former magazine editor, is the author of "Flip! for Decorating."
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If you want to learn more, please visit our website outdoor stainless steel bench.