????? ???????? ?? ???? ????? ??? ?????? ??????? ????, ??? ????? ????? ???? ?????? ?? ?? (???? ????? ??????). ??????? ??? billets ?? ????? ????? ????? ?????. ??????? ?? ??? ?????? ?? 19.3 (20 ℃), ?? ?? ???? ???? ????. ???? ????????? ???????? ???, ???? ??????? ???? ???? ????? ???? ????? ????. ???? ????? ?????? ?? ?????, ?? ??????? 100% ???? ????. ?? "???????" ???? ??? ???? ????? ?????? ????? ??????? ?????? ????.
????? ?????? ???? billets dart ??????? ?? ??? ????? ????? ?????, ??????? 70 ~ 90% ??????? dart bartlets ?????? ????? ??? ??? ?? ???? ???? ??????? ???, ??? 14 ~ 18 ??? 18 ~ 40 ??? ??????, ???????, 65% ? 95 ~ 97% ??????? ?????? ?????? ???? ??????? ?? ???????.