When the joint is rocked during severe vibration, cracks occur at the first thread of the external thread. It shows that:

(1) the Mn content of the alloy steel material for the drill pipe transformation joint is too low, which affects hardenability and has serious band segregation.

(2) the impact toughness of drill pipe is too low, resulting in cracks at the maximum stress when subjected to impact.

(3) the basic reason for the failure of the drill pipe transition joint is that the tempering process is improper, resulting in high temperature temper brittleness.

Factors that affect the speed of mechanical drilling:

(1) drilling pressure, rotational speed and drilling fluid displacement; (2) drilling fluid properties; (3) drill bit hydraulic power; (4) rock drillability and bit type.

Core drilling tool composition (1) core drill: Core Drill: for drilling core; (2) external core barrel: Bear drilling pressure, transfer torque; (3) core core: storage and protection of core; (4) core claws: cut, take, remove core; (5) there are suspension bearings, water head, back pressure van, centralizer and so on.

In order to prolong the service life of drill collar, several tungsten carbide wear belts are usually welded on the surface of the drill pipe joint, and the tungsten carbide wear-resistant belt has achieved good protection for the drill rod joint. But the drill rod joint, which has welded the sharp and granular tungsten carbide wear-resistant belt material, is very serious about the wear of the casing wall during the rotation and lifting of the drill string. At present, many oil companies do not allow the wear belt to be used because of the protection of the casing. Many drilling companies take some measures to carbonization on the drill pipe. In addition, in the process of wear-resistant belt welding, because of some reasons, the quality of the wear-resistant belt welding is not qualified, and the re application is needed to remove the welding. The original method is to use portable sand turbine for grinding, time consuming, laborious and inefficient.