I am a new student. The medium contains hydrogen sulfide. Can I choose 20#9948 ordinary steel pipe?

You can't. Basic requirements for hydrogen-resistant steel pipes:

1. chemical composition, the contents of P and S should be controlled below 0.020% and 0.0 15%;

2. The yield strength should be less than 345MPa；;

3. The material must be silicon killed steel.

4. It shall comply with the provisions of NACE MR0 175.

5. The carbon equivalent CE should be less than 0.42%.

6. The material surface shall not have sharp defects greater than 0.5mm..

7. Materials must be delivered by heat treatment.