Let me list a few things I know.

1. Hardness problem Your shrapnel is too hard. According to you, the possibility is low.

2. The material reason is that your material is wrong or the 400 tempering hardness of 60SI2MN may be a little high.

3. the direction problem. You yourself explained the angle of the direction of the steel band roommate's suppression.

4. Inclusion of raw materials

5. Exceeding the service limit means excessive bending.

Hope useful to you