| | 70% | | | | | | | GB/T 15109 1994 | | | | | | | | | | | 50 | | | | | | | | | | | | | GB/T20822 2007 | | | | | | | | 20 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |