What is the strength of 304 stainless steel sheet?

It is clearly stated in Table 4-1 of Steel Pressure Vessels (GB150-1998).

The tensile strength of 304 steel plate is 520 N/mm2.

Differences between stainless steel 304 and 304L: 1. Material standards 　Currently, the common imported stainless steel standards include SA240 under the American ASME standard, A240 under the ASTM standard, and SUS under the Japanese JIS standard； The commonly used grades are 304, 304L, 316L, etc. As an example, 304 will be used to illustrate how they are denoted: In the JIS standard, the designation for materials is quite simple, expressed as SUS304 ； There are several notations for ASME and ASTM: SA240-304, SA240TP304, A240-304, A240TP304. In fact, the use of a hyphen versus TP has the same meaning. There is 304L material ahead of us; the “L” in this designation indicates a lower carbon content ； Another symbol that is often seen is H, which indicates a higher carbon content and is mainly used in environments with high temperatures ； Another common one is N, which indicates the addition of element N to increase strength. Sometimes, we can also see suffixes such as 2B, No.1, etc. later on; these suffixes indicate the surface condition of the material ； 2B refers to steel plates that, after hot rolling and cold rolling, have a good surface quality meeting the requirements for a mirror finish ； 2D refers to steel plates with an ordinary surface after hot rolling and cold rolling ； No.1 indicates the hot-rolled surface. 　　2. Regarding the substitution of materials In the minds of many of us, it is taken for granted that higher-grade or thicker materials can be used in place of lower-grade or thinner ones, and no further action is needed. In fact, this view is incorrect. Let’s use 304, 304L, and 304H as examples to illustrate this point: generally speaking, 304 has a lower carbon content than 304L and better corrosion resistance, so it can be used as a substitute for 304 material. First, let’s take a look at the chemical composition and mechanical properties of these three materials. (Quoted from ASME Sec.II, Div.A, A99) Table 1 Chemical composition % of 304, 304L, and 304H Type C Mn P S Si Cr Ni N 304 0.08 2.00 0.045 0.030 0.75 18.00–20.00 8.00–10.50 0.10 304L 0.030 2.00 0.045 0.030 0.75 18.00–20.00 8.00–12.00 0.10 304H 0.04–0.10 2.00 0.045 0.030 0.75 18.00–20.00 8.00–10.50 Note: Values without a specified range indicate values that are less than or equal to the stated value. 　　Table 2 Mechanical properties of 304, 304L, and 304H. Type: Tensile strength, Yield strength, Elongation at 50 mm, Hardness, Cold bending. (MPa) (MPa) % Brinell Rockwell 304 ≥515 ≥205 ≥40 ≥201 ≥92 Not required 304L ≥485 ≥170 ≥40 ≥201 ≥92 Not required 304H ≥515 ≥205 ≥40 ≥201 ≥92 Not required Note: Yield strength refers to the 0.2% yield strength. 　　As can be seen from Table 1, 304L indeed meets the requirements of 304 and is even better than it; it seems to be able to replace 304 automatically. However, according to the mechanical properties shown in Table 2, 304 has higher strength than 304L, and using 304L as a substitute when designing for 304 will result in insufficient strength ； Furthermore, clause 4.1.6 of China’s pressure vessel standard GB150-1998 stipulates that when austenitic stainless steel is used at temperatures above 525°C, its carbon content must be at least 0.04%. As can be seen from Table 1, most materials of type 304 can be used, but type 304L cannot. Therefore, the idea that 304L can be used as a substitute for 304 is incorrect. Whether it can be used depends on the application scenario, and according to the relevant regulations, none of us have the authority to make material substitutions; only the original design department is authorized to do so. Please keep this in mind at all times.