P110 oil casing-Oil casing is a steel pipe used to support the well wall of oil and gas wells to ensure the normal operation of the entire oil well during the drilling process and after completion. Each well uses several layers of casing according to different drilling depths and geological conditions. After the casing is lowered into the well, cement is used for cementing. Unlike oil pipes and drill pipes, it cannot be reused and is a one-time consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes. The casing can be divided into: guide tube, surface casing, technical casing, and oil layer casing according to its use.

Oil casing is an important piece of equipment for oil drilling. Its main equipment also includes drill pipe, core tube and casing, drill collar, and small-diameter steel pipe for drilling. The domestic casing is made of geological drilling steel by hot rolling or cold drawing. The steel grade is indicated by "geology" (DZ). Commonly used casing steel grades are DZ40, DZ55, and DZ753.

According to the American Petroleum Institute standard API SPEC5CT 1988 1st edition, casing steel grades are divided into 10 types: H-40, J-55, K-55, N-80, C-75, L-80, C-90, C-95, P-110, and Q-125.

Oil casing should be supplied with threads and couplings, or supplied in any of the following pipe end forms:
Flat end, round thread without coupling or with coupling, trapezoidal thread with coupling or without coupling, direct connection thread, special end processing, sealing ring structure.

Industrial details about P110 oil casing
First, material composition and mechanical properties
Chemical composition design: Based on medium and low carbon steel, a small amount of chromium (Cr) and boron (B) elements are added to improve the hardenability and high-temperature stability of the material15.
Typical composition range: carbon (C) ≤ 0.28%, chromium (Cr) 0.8%~1.2%, trace amount of boron (B), supplemented by other alloying elements to optimize performance7.
Mechanical performance indicators:
Tensile strength: 925~975 MPa, some products can reach 935 MPa25.
Yield strength: 840~895 MPa, meeting the requirements of API SPEC 5CT for P110 steel grade 17.
Impact toughness: The transverse impact energy of the parent material and the weld at 0℃ reaches 77 J and 73 J respectively, achieving "equal toughness" matching, which is significantly better than traditional seamless pipes15.
Anti-collapse strength: an average of 43.5 MPa, exceeding the API 5C3 standard value by 26%, suitable for high-pressure formation environments57.

Second, manufacturing process and technological innovation
High-frequency resistance welding (HFW) combined with full pipe tempering
High-frequency welding: High-frequency resistance welding technology is used, the weld heat-affected zone is small, the welding efficiency is high, and it is suitable for the production of medium and large diameter casing (such as Φ244.48 mm×11.05 mm)15.
Heat treatment process: Full pipe tempering treatment (quenching + tempering) optimizes the microstructure, and improves uniformity and fatigue resistance17.
SEW process (HFW + thermal tension reduction)
Thermal tension reduction: By accurately controlling the reduction rate, the wall thickness uniformity is improved (the deviation is only -1.74%~1.31%), the ovality is <0.17% and the geometric accuracy is significantly better than seamless pipe24.
Weld optimization: Using special post-processing technology, the weld impact toughness reaches 66~78 J, close to the parent material level 24.

Third, application scenarios and performance advantages
Applicability for deep wells/ultra-deep wells
Internal pressure resistance: >60 MPa, external pressure collapse resistance of 43.5 MPa, meeting the complex formation pressure requirements of deep wells (>4500 meters)17.
Threaded connection strength: >6176 kN, ensuring the stability of the wellbore structure5.
Advantages compared with traditional seamless pipes
Cost-effectiveness: High-frequency welded pipes have high production efficiency and costs are 20%~30% lower than seamless pipes2.
Dimensional accuracy: Improved wall thickness uniformity, reducing downhole installation risks24.

Fourth, quality control and standard certification
Testing items
Non-destructive testing: Ultrasonic flaw detection (UT) and radiographic testing (RT) ensure that welds are defect-free15.
Mechanical testing: Covering tensile, impact, and hardness tests, in line with API SPEC 5CT and API TR 5C3 standards7.
Certification and standards
Certified by API (American Petroleum Institute), product performance fully meets or even exceeds P110 steel grade requirements25.