API drill collar blank

ZYTGS Drill Collars are manufactured from 4145H modified alloy steel . The full length of heat treatment adopts the original medium frequency inductance heating method. Strict metallurgical specifications are followed to insure that full length heat treating produces a consistent maximum depth of hardness. After this, a hardness range of 285 to 341 BHN are guaranteed one inch below the surface at room temperature. The bores are held to close tolerances by trepanning and are drifted to API specifications. The minimum external surface finish is hot-rolled and mill-finished. Connections are machined to API specifications and monogrammed with the API symbol. Connections are also machined to prevent galling. Thread roots are cold rolled to provide longer fatigue life. Ordering Instructions: When ordering or requesting quotations on drill collars, please specify: 1. Drill collar OD 2. Drill collar ID 3. Overall length 4. Connections required (size and type) 5. Indicate preference for pressed or cast steel thread protectors 6. Special features desired, for example:Slick or Spiral; Stress Relief Features;Slip and/or Elevator Recess;Hardbanding