How to identify 304 stainless steel plate?

To accurately determine whether a stainless steel plate is made of 304 grade, you can employ several methods as follows. Read on to learn more.

Chemical Testing

Utilize a solution specifically designed for testing stainless steel types. When applied, the solution should not alter its color within 1 to 3 minutes for genuine 304 stainless steel. In contrast, a 201 stainless steel plate will quickly turn a dark brown-red, while a 202 plate will turn light brown-red within 5 seconds, and a 301 plate will show a light brick red within 1 to 2 minutes.

Magnetic Attraction Test

Employ a specialized magnet to test for 304 stainless steel. Due to its low magnetic properties, a 304 plate will exhibit minimal attraction. If the magnetism is strong, the plate is likely made of 202 stainless steel.

Professional Inspection

Consult with industry professionals who can assess the plate's authenticity based on its surface characteristics, such as color and smoothness.

Distinguishing 304 from 304L Stainless Steel:

- Chemical Composition

Both 304 and 304L stainless steels primarily consist of 18% chromium and 8% nickel. The key difference is the carbon content; 304L is a low-carbon variant with less than 0.03% carbon, whereas 304 contains less than 0.08% carbon. The "L" in 304L signifies ultra-low carbon, making it more resistant to corrosion.

- Welding and Corrosion Resistance

While 304L and 304 stainless steels have similar corrosion resistance under normal conditions, 304L exhibits superior resistance to intergranular corrosion after welding or stress relief. It maintains good corrosion resistance without the need for heat treatment, with a useable temperature range of -196°C to 800°C. 304 stainless steel is widely used for its excellent corrosion resistance, heat resistance, low-temperature strength, and mechanical properties. It is also easy to work with hot processes like stamping and bending, and it does not harden after heat treatment (non-magnetic, with a use temperature range of -196°C to 800°C).

- Cost

The cost of 304L stainless steel is generally higher than that of 304 stainless steel due to its lower carbon content and enhanced corrosion resistance.

- Hardness

In terms of hardness, 304 stainless steel is superior to 304L because carbon content directly influences the hardness of stainless steel. There is also a 304H series, where "H" indicates a higher carbon content, resulting in greater hardness.