优质碳素弹簧钢含炭量百分之0。65怎么用英文翻译

You should mark the standard and designation, using AISI, ASTM or DIN or others.
some steels with GB can not meet a kind of steel under a standard of overseas.

C1065 AISI is enough.

you need not translate it as high quality /carbon steel for spring/carbon content 0.65 % GBXXX.XXXX