N80Q casing is a standard oil casing commonly used in the oil industry, produced from seamless steel pipe. The manufacturing process includes a quenching and tempering heat treatment as per standard requirements. Here's a detailed overview of the N80Q casing production process and associated quality control measures.
Production Process of N80Q Casing
Furnace Refining: The initial refining of the steel in the furnace.
Continuous Casting: The refined steel is cast continuously to form billets.
Annular Furnace Heating: The billets are heated in an annular furnace for about 2.5 hours.
Perforation: At approximately 1250°C, the billets are perforated to form hollow tubes.
Continuous Rolling: The perforated billets undergo continuous rolling.
Stepping Furnace: The steel is heated in a stepping furnace.
Sizing: The tubes are sized to the desired dimensions.
Sawing: The tubes are cut to the required length.
Tempering Treatment: The tubes undergo tempering heat treatment.
Straightening: The tubes are straightened to ensure uniformity.
Physical and Chemical Testing: The tubes undergo rigorous testing to check their physical and chemical properties.
Thread Processing: Threads are processed on the tube ends.
Coupling Tightening: Couplings are tightly secured.
Hydrostatic Testing: Each tube undergoes a hydrostatic pressure test.
Measuring, Weighing, and Marking: Tubes are measured, weighed, marked for identification.
Packaging and Storage: The final product is packaged and stored.
Key Considerations in Production of N80Q Casing
Heating and Rolling Temperatures: The billets are perforated at about 1250°C, with sintering at 950°C and finish rolling at 900°C.
Chemical Composition Analysis: The chemical composition is analyzed to ensure that it is not the cause of any defects.
Metallographic and EDS Analysis: These analyses reveal that iron oxide inclusions at the crack tip and middle part cause cracks, which are non-quenching cracks formed before heat treatment, likely due to perforation and hot rolling.
Issues in Perforation and Rolling of N80Q Casing
Temperature Non-uniformity: Uneven temperature distribution can cause additional stress, leading to cracks.
High Heating Temperature: Reduces intergranular binding force, causing cracks.
Low Heating Temperature: Increases deformation resistance and deterioration of perforation conditions, also leading to cracks.
Additional Deformation Stresses: The presence of longitudinal and transverse shear stresses during perforation and rolling contributes to crack formation.
Recommendations for Improved Quality Control
Monitor Perforation Temperature: Ensure the perforation temperature is controlled within ±20°C to prevent cracks.
Control Sizing and Finishing Temperatures: Maintain consistent temperatures during sizing and finishing to prevent stress-induced cracks.
Increase Testing at Pipe Ends: Strengthen testing at the ends of the tubes, including increasing the cut length if necessary.
Conclusion
N80Q casing pipe cracks typically occur during the perforation and rolling process due to uneven heating and the presence of additional stresses. By adjusting the process parameters for perforation and hot rolling, and maintaining stringent control over heating temperatures, the formation of cracks can be minimized. These measures ensure the production of high-quality, reliable N80Q casing pipes for use in the oil industry.
United Steel Industry As the most important steel pipe manufacturer and exporter in China, in the past 20 years, we have completed more than 100 projects, with partners in more than 100 countries, and established relationships with oil and gas and EPC companies in many countries business relationship.
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