Stainless steel is a type of versatile engineering material and is well known because of its corrosion and heat resistance. Among the stainless steel alloy family, 304 and 316 are commonly used in various applications. Here we’ll compare different types of stainless steel grades: 304 vs 304L vs 316 vs 316L. All of them contain principally iron but differ in chemical composition and properties.
304, 304L, 316, 316L are all austenitic stainless steel. The L in 304L and 316L means the low content of carbon in the steel. Junying is specialized in stainless steel CNC machining and provides 304/316 stainless steel CNC parts with high quality.
1. Stainless Steel 304
Stainless steel 304 is the most common austenitic stainless steel, containing a high nickel content that is typically between 8 and 10.5% by weight and a high amount of chromium at approximately 18 to 20% by weight. SS304 has good corrosion resistance, heat resistance, and good mechanical properties; it has good hot workability such as stamping and bending, and no heat treatment hardening phenomenon.
Typical Applications of Alloy 304
– Household products such as tableware, cabinets, and water heaters
– Appliances such as refrigerators and dishwashers
– Auto parts such as windshield wipers
– Medical equipment
– Structures and building materials
2. Stainless Steel 304L
It is a variant of stainless steel 304, comes with lower carbon content. The lower carbon content reduces the precipitation of carbide in the heat-affected zone near the sewing to the minimum, and the precipitation of carbon elements may cause welding corrosion in some environments. As a low-carbon 304 steel, its corrosion resistance is similar to that of 304 under normal conditions, but after welding or stress relief, its resistance to intergranular corrosion is excellent; it can also maintain good corrosion resistance without heat treatment.
Typical Applications of Alloy 304L
– Food processing equipment
– Kitchen benches, sinks, and appliances
– Architectural trim and molding
3. Stainless Steel 316
316 stainless steel also contains high amounts of chromium and nickel, with the majority of the composition being iron. Due to the addition of molybdenum, stainless steel 316 has excellent corrosion resistance, atmosphere corrosion resistance, and high-temperature strength, and can be used under tough conditions; it has excellent work hardening ability.
Typical Applications of Alloy 316
– Equipment used in seawater, chemical, dye, etc.
– Medical devices
– Marine parts
– Refinery equipment
4. Stainless Steel 316L
As a low-carbon series of alloy316, in addition to having the same characteristics as alloy 316, it has excellent intergranular corrosion resistance.
Typical Applications of Alloy 316L
– Chemical and petrochemical industry
– Food processing
– Pharmaceutical equipment
– Medical devices
– Marine applications near the seashore
1. Chemical Composition
The key difference between 304 and 304L, as well as, 316 and 316L is the carbon content. Put the steel in a temperature range of 450 to 850°C for periods of several minutes, if the carbon level is below 0.030% then this intercrystalline corrosion does not take place following exposure to these temperatures. Both stainless steel 304L and stainless steel 316L have low carbon content. Because the carbon content is reduced, chromium carbide will not be produced, and intergranular corrosion will not occur. The low carbon type may be easier to shape and form as well.
2. Properties Comparison
– Mechanical Capacity
– Corrosion Resistance. The corrosion resistance of stainless steel 316 is better than that of 304, stainless steel 316 is also resistant to the erosion of the ocean and the corrosive industrial gas.
– Heat Resistance. The melting range of 316 SS is 1371 °C to 1399 °C, and the 304 stainless steel reaches its melting point at the 1399 °C to1454 °C range. 304 stainless steel possesses good oxidation resistance in intermittent service to 870 °C and in continuous service to 925 °C. In intermittent use below 1600 ℃ and continuous use below 1700 ℃, stainless steel 316 has good oxidation resistance.
– Heat Treatment. 316 stainless steel cannot be hardened by heat treatment. The recommended annealing temperature for 316L wrought steel is 1400 °C
– Welding. The welding of 316L stainless steel is better than SS 316. AISI 316 may lead to stress-corrosion cracking or dimensional instability after welding, to heat treatment post welding is needed. Type 304 stainless steel has good forming and welding properties, lower carbon content in 304L minimizes deleterious or harmful carbide precipitation as a result of welding.