Oil drill collar

Drill collars are an important part of the drill string during oil drilling. Drill collars are located in the lower part of the drill string and are connected to the drill bit. In addition to transmitting torque, the weight on bit is also stroked to allow the bit to penetrate. During use, the drill collar is subject to environmental stress corrosion and alternating bending fatigue stress are the main factors causing failure and damage. In recent years, due to the continuous occurrence of fracture events of oil drill collars, it has attracted great attention from relevant parties.

The raw material of the drill collar is 42CrMo steel smelted by electric arc, and it is delivered in the hot-rolled state. The manufacturer straightens the drill collar in the hot-rolled state, roughs it, and then quenches and tempers it (normalizing at 860 °C ± 10 °C, quenching at 790 °C -800 °C , Tempering at 520 ℃ -525 ℃), straightening, stress relief and tempering at 520 ℃ for 6 hours, leaving the furnace for air cooling, testing the mechanical properties, and handing over to the Ministry of Petroleum for use after finishing.

Ⅰ、AISI4145H Drill Collar Steel Supply Specifications

1. The size, shape, weight and allowable deviation of the steel
It should meet the requirements of Group 2 of GB/T702 "Size, Shape, Weight and Permissible Deviation of Hot-rolled Round Steel and Square Steel".

2. Smelting method:
It is smelted by electric arc furnace + refining outside the furnace + vacuum degassing.

3. Chemical composition of AISI4145H steel

Table 1 The unit is %

●3.1 Harmful elements should meet the requirements in Table 2
Table 2 The unit is %

●3.2 The allowable deviation of the chemical composition of finished steel products shall comply with the provisions in Table 2 of GB/T222.

4. Delivery status:
The steel is delivered in an annealed state according to the contract requirements, and the Brinell hardness of the steel in the delivery state is 187-229HBS.

5. Mechanical properties
The mechanical properties of steel Φ25 mm heat-treated blanks should meet the requirements in Table 3.

table 3

Table 4 Φ25 ㎜ heat treatment blank process

850±15 oil 600±15

●5.1 Requirements for inspection

●5.1.1 Impact test: Charpy V-type impact energy, three longitudinal impact samples are used as a group. Impact sample size: 10×10×55㎜.

●5.1.2 Tensile test is for longitudinal blank.

6. End hardenability

The end hardenability of the steel is tested according to GB225, and the heat treatment process and the hardenability value of the steel should meet the requirements in Table 5.

table 5

7. Non-metallic inclusions

Steel products shall be inspected for non-metallic inclusions according to GB/T 10561, and shall comply with the provisions in Table 5.

Table 5 Unit: Grade

8. Low-magnification tissue

●8.1 The transverse acid leached low-magnification structure of the steel must not have defects such as shrinkage cavities, cracks, delamination, white spots, air bubbles, skin turning and inclusions that are visible to the naked eye.
●8.2 Requirements for transverse acid leaching low-magnification structure of steel:
General porosity ≤2.0 level; central porosity ≤2.0 level; segregation ≤2.0 level.

9. Non-destructive testing

The steel is subjected to ultrasonic flaw detection one by one, the flaw detection standard is GB/T4162－91, and the precision is A grade.

10. Surface quality

The surface quality of the steel shall be in accordance with the steel for pressure processing in Article 6.6 of GB/T3077-99.

Ⅱ、 Technical Documentation Requirements
The trial production of this product must draft a new product trial production process plan. The trial production process plan should include electric furnace smelting, continuous casting process key points, rolling process key points, product inspection, judgment, packaging, quality certificate, etc., control of non-metallic inclusions, Hydrogen content control, continuous casting process control, slab slow cooling, finished product strip temperature annealing, etc. should be specified in detail.

Ⅲ、Equipment and inspection requirements
1. Equipment
All kinds of production equipment should be in good condition, and should be maintained and tested according to the requirements of the company, and can only be used after passing the test.
2. Inspection requirements
All kinds of inspection equipment should be in good condition, and should be maintained and verified according to the requirements of the company, and can only be used after passing the test. Must have the ability to inspect various indicators in the supply technical indicators of AISI4145H steel for drill collars, such as end hardenability inspection, etc. All inspection items are available.