carbon steel pipe material: Q195,Q215,Q235,Q345,20#,30#,45# etc standard ... products include Square Stainless Steel Pipe,Stainless Steel Pipe,seamless stainless steel pipes,welded Stainless Steel Pipe and so on .carbon steel pipe: 1) Material: Q195,Q215,Q235, ... or black painted to prevent rust. 9) Application: square steel pipe can be used in construction structure machinery, container rall structure ...