304 and 316 are Austenitic stainless steel, there is no difference in appearance. If there is no word block identification, we cannot distinguish it with eyes. Both 304 and 316 after heat resistance, corrosion resistance and strength, so, what’s the really different between them?
First, let’s check the difference between the element content of 304 and 316 in ASTM standards. Open the website of JINSON Fittings and click the technical sheet in the download section, here we go!
In practice, there is no molybdenum element in grade 304. Therefore, the biggest difference between 304 and 316 is the content of nickel and molybdenum.
Grade 316 has higher content of nickel and molybdenum elements, which increases corrosion resistance in some environments.
316 stainless steel has a higher resistance to pitting and corrosion when exposed to chlorides and non oxidizing acids. This mean it is the best option to use when exposed to saltwater or harsh environments.
This does not mean that 304 is not have corrosion resistance, just lower than 316. In fact, 304 is suitable for use in any general applications, For instance, most of the stainless steel thermos cups we use in our daily life are made of food grade 304 material.
At this time, there will be a lot of friends ask, I often see 304L and 316L, with and without “L” what is the difference? In fact, many of our clients have the same question. So what does “L” stand for? Is it “Long”? Or “Line”?
Obviously, the first term, the amount of carbon, big gap. That means 316L is a low carbon version of 316, and L means low carbon.
The low carbon “L” grades are useful where welding or other high temperature exposure will occur, particularly welding of medium or heavy sections. The low carbon is one way of delaying or preventing grain boundary chromium carbide precipitation (often referred to as “sensitisation”) which can result in intergranular corrosion in many service environments. The time for damaging precipitation to occur is highly dependent upon the amount of carbon present in the steel, so low carbon content increases resistance to this problem.
By the way, it’s also worthwhile to note that the tensile strength is slightly lower compared to 304 and 316 because of low carbon.