... / B/ C/ D, 27SiMn, 40Cr, 40CrMn, 20CrMn, 30Mn good quality seamless pipe Size: dia 10mm-630mm Material: 10#-45#, Q345A/ B ... ) ,GB3087-99 ( boiler pipe ) , GB5310-95 ( boiler pipe for high pressure ) , GB6479-2000 ( fertilizer special pipe ) , GB9948-88 ( petroleum cracked pipe ...