When manufacturers build or expand process piping systems, they have a universe of material options to choose from.
Stainless steel—and particularly 300-series formulas—are a popular choice for a wide variety of piping applications. The 304, 316 and 316L stainless steel formulas are the most commonly specified. They feature the right mix of strength, weldability, corrosion resistance and economical cost.
But which of these is the right choice for your application? As we describe below, piping systems perform best when the materials they’re made of match the processes they support.
304, 316 and 316L stainless steel formulas are austenitic, a term classifying the steel’s crystalline structure. This structure is achieved via heat treatment at very high temperatures followed by quenching—a rapid cooling process locking the structural characteristics in place. Austenitic formulas are stronger than martensitic or ferritic steels. Ferritic steels are magnetic, have a low carbon content and are less corrosion-resistant.
304 stainless steel is the most common stainless formula across industrial and consumer applications. With chromium and nickel alloys, 304 is resistant to many corrosion attacks. It’s also popular in a wide range of applications because no post-weld anneal (a reheating and slow cooling process that relieves stress in metals after exposure to high heat) is required.
316 stainless steel is similar in chemistry to 304 but also includes molybdenum. That addition makes it much more corrosion resistant. Like 304, the 316 formula does not require post-weld annealing.
316L stainless steel is almost identical to 316. The only difference is the carbon content. 316L’s lower carbon content imparts even better corrosion resistance than 316. 316L does not require post-weld annealing.