304 stainless steel: 0Cr18Ni9 Chemical composition mass fraction% | C: ≤ 0.07
316L stainless steel: 0Cr17Ni12Mo2 Chemical composition mass fraction% | C: ≤ 0.08
If it is the hardness of the raw material, then according to the design criteria, 316 is relatively hard. After heat treatment, due to the high carbon content of 316, it will achieve higher hardness, in short, 316L is hard.
But the only difference from 304 is the issue of corrosion: 316 stainless steel contains Mo, which has better corrosion resistance than 304 stainless steel in high temperature environments. Therefore, in high temperature environments, engineers generally choose components made of 316 material.
From the perspective of raw materials, there is no difference in the mechanical properties between 304 stainless steel and 316 stainless steel. The difference between these two materials lies in the fact that 316 material is an austenitic stainless steel containing molybdenum, which is more resistant to halogen elements, such as local corrosion caused by chloride ions in seawater - pitting corrosion and crevice corrosion.
Strictly speaking, the strength of 316L stainless steel is slightly lower than that of 304 and 316. The main reason is that 316L has a low carbon content. L represents Low Carbon. Due to the low hardness of austenitic stainless steel itself and the inability to undergo quenching, this strength is mainly manifested in tensile strength and yield strength.
There are also differences between the two in terms of brand names; 304 stainless steel corresponds to Chinese grade 0Cr18Ni9; 316 stainless steel corresponds to Chinese grade 0Cr17Ni12Mo2.
316 mainly reduces Cr content, increases Ni content, and increases Mo2%~3%. Therefore, its corrosion resistance is stronger than 304, making it suitable for use in chemical, seawater and other environments. Similarly, the cost of 316 is higher than 304. Generally, 316 is used in places with higher requirements to replace 304.