How to determine whether it is 201 or 304 stainless steel？

To determine whether stainless steel is type 201 or 304, you can use the following methods:

1. Chemical Reagent Testing

• Manganese Test: 201 stainless steel contains a higher amount of manganese. Apply a manganese testing solution (e.g., "manganese test liquid") to the surface. If it turns red or reddish-brown quickly, it is likely 201 stainless steel. 304 stainless steel will show no significant change.

• Nickel Test: 304 stainless steel contains more nickel. Apply a nickel testing solution to the surface. If it turns red, it is likely 304 stainless steel. 201 stainless steel will show no significant change.

2. Spectroscopic Analysis

• Use a spectrometer to accurately analyze the elemental composition. 304 stainless steel typically contains about 8%-10.5% nickel and 18%-20% chromium, while 201 stainless steel contains about 1%-1.5% nickel and 16%-18% chromium.

3. Magnetic Test

• 304 stainless steel is usually non-magnetic or weakly magnetic, while 201 stainless steel is more magnetic. Use a magnet to test: if it sticks strongly, it is likely 201 stainless steel; if it sticks weakly or not at all, it is likely 304 stainless steel.

4. Surface Observation

• 201 stainless steel has a darker and less shiny surface, while 304 stainless steel has a brighter and more polished appearance.

5. Spark Test

• Grind the stainless steel with a grinding wheel. 201 stainless steel produces more and shorter sparks, while 304 stainless steel produces fewer and longer sparks.

6. Salt Spray Test

• 304 stainless steel has better corrosion resistance, while 201 stainless steel is less resistant. Place the sample in a salt spray environment, and 201 stainless steel will rust more easily.

7. Density Measurement

• The density of 304 stainless steel is about 7.93 g/cm³, while 201 stainless steel is about 7.80 g/cm³. Measuring the density can also help in identification.

Summary

• 201 Stainless Steel: High manganese content, magnetic, darker surface, and lower corrosion resistance.

• 304 Stainless Steel: High nickel content, non-magnetic or weakly magnetic, brighter surface, and higher corrosion resistance.

Choose the appropriate method based on your specific needs to determine the type of stainless steel.