How is the process and time of Kunshan social security refund stipulated?

There is no specified time. I can't return it anyway. Just buy it. Social security is neither a bank nor a commodity. There is no such thing as getting it back or returning it. You can only return it when you reach your legal retirement age. You can only return the part of your personal account, which only accounts for about 1/3 of your total insured amount, and the other 2/3 has been integrated into the labor insurance fund and will not be refunded.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.