... of seamless steel pipe GB / T8162-1999, grades: 10, 20, 35# # #, 45, #, specifications: 6-720* 1-70mm 10 Seamless steel pipes conveying ... fluid GB / T8163-1999, grades: 10,20, # #, specifications:6-720* 1-70mm ... 11 Low and medium pressure boiler pipe steel grade GB3087-1999, 10, 20: # #, specifications: 6-720* 1-70mm ...