carbon steel pipe material: Q195,Q215,Q235,Q345,20#,30#,45# ... stainless steel pipes,welded Stainless Steel Pipe and so on .carbon steel pipe: 1) Material: Q195,Q215,Q235,Q345,20#,30 ... : +/-0.03mm, Thickness tolerance:=/-0.02mm. 8) Surface: oiled or black painted to prevent rust. 9) Application: square steel pipe can ...