Manufacturing Process of API 11B Sucker Rod

1. Raw material preparation and inspection

Raw material selection: Alloy steel bars that comply with the API SPEC 11B standard are selected.

Material inspection: When entering the warehouse, it is necessary to verify the correspondence between the material report and the batch number of the furnace. Use a spectrometer to recheck the content of elements such as C, Cr, and Mn to ensure that the carbon equivalent is controlled below 0.45%.

Surface defect detection: Magnetic particle inspection is adopted to detect surface defects. Billets with longitudinal crack depth exceeding 0.2mm need to be returned to the warehouse.

2. Pretreatment

Straightening: Use a fully automatic hydraulic straightening machine to straighten the billet to ensure that the straightness deviation is controlled within 0.8mm/m.

Peeling: Perform peeling processing to remove the surface oxide layer. The single-sided cutting allowance shall not be less than 0.5mm, and the roughness Ra value shall be maintained below 3.2μm. The processed billets are stored in the constant-temperature workshop for no more than 48 hours.

3. Heating and forming

Heating: The billet is heated to 1150±20℃ using a medium-frequency induction heating furnace. The holding time is calculated at 1.2 minutes per millimeter of diameter.

Upsetting forming: Upsetting forming is carried out using a 6300kN die forging press, and the preheating temperature of the die should not be lower than 250℃.

Residual heat normalizing treatment: Residual heat normalizing treatment should be carried out immediately after forging, and the air cooling rate should be controlled at 30℃/min.

4. Quenching and tempering treatment

Quenching: Select No. 32 mechanical oil as the quenching medium, maintain the oil temperature at 60-80℃, and calculate the cooling time at 6 seconds per millimeter of the rod body thickness.

Tempering: Tempering treatment is carried out using a continuous production line with a mesh belt, with the temperature set at 560±10℃ and the holding time at 90 minutes. The hardness of the processed rod body needs to reach HRC28-32.

5. Fine processing

CNC lathe processing: The fine processing of the rod body is completed in three passes. The rough turning allowance is 1.5mm, and the semi-finish turning allowance is 0.3mm. The cutting tool selected is the hard alloy blade of model WNMG080408. The cutting speed is set at 180m/min and the feed rate is 0.2mm/r.

Thread processing: Thread processing is carried out using comb tool forming technology, with the tooth profile Angle tolerance controlled within ±0.5°.

Cylindrical grinding: Cylindrical grinding machines are divided into two processes: rough grinding and fine grinding. The grit size of the coarse grinding wheel is 60#, and the removal amount is 0.15mm. The WA80K grinding wheel was selected for fine grinding, with a removal rate of 0.03mm. The surface roughness Ra after processing is ≤0.8μm, and the cylindricity error does not exceed 0.01mm.

6. Surface treatment

Shot peening: Cast steel shot medium is used, with a diameter of 0.8mm, shot peening strength of 0.45mmA, and coverage rate of 200%. The residual compressive stress value of the treated surface needs to reach above -650 mpa.

Phosphating treatment: Zinc-based phosphating solution was used for treatment, with a total acidity of 28 points, a free acidity of 3.5 points, a treatment temperature of 75℃, and a duration of 12 minutes. The phosphating film thickness is 6-8μm and it needs to pass the copper sulfate drop test (>3 minutes).

7. Inspection and Testing

Mechanical property test: Randomly select 3% of samples from each batch for tensile test, with a yield strength of ≥860MPa and a reduction in area of ≥45%.

Fatigue test: The fatigue test was conducted using the three-point bending method, with the loading stress amplitude at 370MPa and the number of cycles >2×10^6 times.

Non-destructive testing: Ultrasonic flaw detection is carried out in accordance with the ASTM E317 standard. A 5MHz straight probe is used. Defects with an equivalent diameter exceeding 1.2mm are judged as non-conforming. Magnetic particle detection uses fluorescent magnetic suspension, and the crack display is observed under a black light lamp.