Study on Properties of 80 Steel Expandable Tube for Oil and Gas Exploitation Service

The over-all properties of the 80 steel expandable tube as developed with the SEW process are analyzed，involving such properties as microstructure，hardness，residual stress，mechanical properties，and external pressure/internal pressure failure，etc.The results reveal the facts as follows.The microstructure of the said tube is composed of ferrite and tempered sorbite.After being deformed via expansion with expansion rate of 16.50%，the tube presents such mechanical properties as yield strength：640~650 MPa，tensile strength：725~735 MPa，elongation：18.5%~20.5%，transversal impact toughness of the weld（size：1/2 and temperature：0 ℃）：56~60 J，external pressure collapse strength：over the standard 18%as required by API RP 5C3，and hydrostatic pressure strength：over the standard 88%as specified by API Spec 5CT.All the above mentioned data demonstrate that the 80 steel expandable tube is in possession of excellent over-all mechanical properties.