Stainless steel comes in more than 100 grades and is preferred because of its strength, resistance to corrosion as well as hygiene. But before you buy 316 stainless steel tube which is usually recommended for different applications, there are some considerations you may need to make.
For many, it can be a challenge keeping in mind the different properties of the grades of steel available so when they find one that works, they choose to stick with it. That is why many people will buy 316 stainless steel tube since it usually works in most applications. If you are thinking of exploring other options, these are some things to keep in mind.
Exposure to Corrosion
Stainless steel has varied ranges of resistance to corrosion. Some grades can withstand much more than others so you need to consider how corrosive the environment they will be applied will be.
Austenitic grades like 316 have a high amount of chromium which makes them more corrosion resistant. However, some people may opt for 304 in areas where the corrosion will not be very intense and then 316 where the corrosion needs extra resistance. Because of the presence of Molybdenum in 316, it has a higher resistance than its close substitute 304.
If you are trying to save money, then a more affordable grade of corrosion-resistant steel would be ferritic stainless steel. They have lower amounts of chromium and nickel and this means the resistance is lower than Austenitic grades. Duplex grades are also an option in cases where cracking may occur if you use 316.
Will Heat be Applied
Different applications will require the use of heat or exposure to heat. For example, if welding has to be done, you need to be sure that the composition of the steel will make it suitable for that process. Alternatively, you should know the best way to apply heat to it. Austenitic steel like 304 has good weldability in comparison to ferritic steel which is more likely to crack in the process of welding. The best choice for welding would be duplex stainless steel grades like 407 or 430. Before you choose any grade for welding, get to know if it is susceptible to hot cracking. Such stainless steel grades cannot be welded.
In applications that may involve exposure to heat like in industries where hot substances will be passed through the tubes, 316 would be a good option since it can withstand high temperatures. This grade can also be used in vehicle engines that will operate at high temperatures.
Mechanical Ability
This is simply its strength. Consider how much stress it is going to be put under and whether it will withstand the pressure. While you might consider the presence of nickel when judging the mechanical ability of stainless steel, it is equally important to know how it was processed. The strength of an alloy will be determined by its processing. This means you need to consider the manufacturer of steel. Some manufacturers may not follow the best process for making good mechanical grade steel.
When dealing with austenitic steel like 316, you should know that it is hardened through cold working unlike steel with a high carbon component which is hardened by applying heat. The cold working process however should only be used when the steel is going to be used in mechanical applications because this process compromises impact resistance.
Magnetism
The elements that make up an alloy will determine its magnetic properties. This is why different grades of steel have varying magnetic abilities. The presence of chromium can make steel magnetic, this however will not apply to every alloy because other compositions can change that feature.
Austenitic grade steel has chromium added to it however it is not magnetic because nickel is also added to it which removes the magnetic property. The amount of nickel varies in austenitic steel so some may have low magnetic properties while 316 and 310 are both non-magnetic because of the high amount of nickel added to it. This is one way of testing to see if it is genuine 316. If you bring a magnet close to 316, there should be no attraction.
So, if you need to apply stainless steel in a non-magnetic process, then 316 would be a good choice however if you need magnetic steel, ferritic steel is the better option.
Conclusion
There are several grades of stainless steel with varying properties. The best strategy to choose a grade would be to list down the properties you need in the application then search for the steel that has that property. Many of them have close substitutes that may cost less but note that sometimes this means you have to compromise certain properties if you choose a lower grade. Be sure that the choice you make will not negatively impact the application.
