The concrete pump straight pipe is made of special alloy steel ( 45Mn2). The inner pipe wall is case hardened by CNC high-frequency induction hardening machine. The inner pipe wall becomes a wearable layer with high hardness. Material: High Manganese casted such as ST52, 37Mn5, 45Mn2 Size: Dia. 133, dia 140, dia. 159, dia 168