A.δ=±1° B.δ=±3° C.δ=±5° D.δ=±10°
A.0.05%~0.1% B.0.1%~0.3% C.0.2%~0.5% D.0.5%~1%
A.3%~5% B.5%~10% C.10%~15% D.l5%~20%