Our company's drill collars are manufactured from 4145H Modified quenched and tempered steel. After the full length special heat-treatment, a hardness range of 285 to 341 BHN are guaranteed one inch below the surface at room temperature.
Connections are cold-rolled, phosphatized, coated and equipped with thread protectors. These are gauged to API standards.
Size: OD 31/2"~11", length: 10ft~31ft