Here at Metal By The Metre we get a lot of questions about stainless steel and one of the most common inquiries is what the difference between 304 and 316 grades. We get it – it’s confusing at first. So let’s set you on the path to enlightenment and illuminate what these numbers mean for your building project.
There are three different categories of stainless steel:
Austenitic, Ferritic and Martensitic.
304 and 316 are grades of stainless steel that fall under the austenitic umbrella.
Chances are if you have worked with stainless steel before you have used austenitic steel. It is the most commonly used variety of stainless steel. It is set apart due to it’s high chromium and nickel content that affords it with high resistance to corrosion. Austenitic stainless also has the tendency to be non-magnetic, or at least it can’t become magnetic easily.
What is 304 Grade?
The most common of all stainless steels, 304 has had its share of the limelight because of high tensile strength, measuring in approximately 621MPa. It also is super heat resistant with a usefulness up to 870℃. The grade of 304 is given when the steel has a balance of 18 – 20% chromium and 8 – 10.5% nickel.
304 stainless is frequently used in the production of appliances such as dishwashers, kitchen and laundry sinks, refrigerators, commercial food processing equipment, fasteners (screws, washers, and balustrade fittings to name a few), wire rope, pipes, and a plethora of building material materials were strength and resistance to corrosion and temperature is desired.
The combination of strength and resistance to corrosion and ability withstand high and low temperatures makes the 304 grade very versatile. It also has very good weldability for joining pieces of steel and is easier to mold than 316 stainless.
While the steel has distinguished corrosion resistance, when exposed to chloride environments, such as salty sea water, it can deteriorate with pitting and crevices.
What is 316 Grade?
316 grade stainless steel is the closely related cousin of 304 and has much of the same characteristics. They are both super popular but if you had to decide a second place it would fall to 316 solely due to it being slightly less common. In fact, though they share tensile strength and resistance to high temperatures but is the tougher of the two when it comes to corrosion. The main difference is that 316 has an additional component of 2 – 3% Molybdenum which improves it’s resistance to corrosion.
Because it is not easily corroded by sea water, 316 stainless is the more suitable choice for marine applications, such as anchors, balustrade fittings, rope wire for main stays and rigging, handrails and other boating accessories. It is also the prefered grade for chemical processing and storage equipment, refinery equipment, and medical devices.
Like 304, 316 grade is also durable, resistant to high temperatures, easy to fabricate, clean and weld, making it very versatile. It performs well in marine environments
Due to its components, 316 is less malleable than 304 (which can be a pro in some instances) and it is much more expensive.
Metal By The Metre like to keep things simple for their Central Coast customers. So when you come into your favourite steel supplies store in Gosford to pick up a marine grade stainless steel hooks and turnbuckles for your new shade sail, or a box of stainless steel screws for your deck, keep this in mind:
Use 304 when price is more important than corrosion resistance or the environment isn’t salty.
Use 316 when high resistance to corrosion (particularly marine environments) is a more important factor than cost.