铜合金 C7025 K55 C7035 K57 C18070 K88 C19900 K75 C19210 YCUT C19400 DT-S C19210 C18400 C68800 C17000 C17200 C17500 C17300 C17400 NTK322 NKC388 NTKS-4 C50715 C5240