Quenching steps
The steps for quenching drill pipe generally include preheating, heating, heat preservation, quenching, tempering and other stages. The specific steps are as follows:
1. Preheating: Put the drill pipe to be quenched into the furnace, raise the temperature to 200℃~400℃, and keep it for 1~2 hours to heat the drill pipe evenly and reduce the temperature gradient during quenching.
2. Heating: Put the preheated drill pipe into the quenching furnace and heat it to a suitable temperature, which is generally about 50℃~100℃ above the critical temperature of steel. The duration depends on the diameter and wall thickness of the drill pipe.
3. Heat preservation: Keep the drill pipe at the heating temperature for a certain period of time to make the inside of the drill pipe fully heated.
4. Quenching: Quickly put the drill pipe into the quenching medium (such as water, oil, brine, etc.) to quickly cool the surface of the drill pipe and form martensite.
5. Tempering: Heat the quenched drill pipe to a suitable temperature and keep it warm for a certain period of time to transform the martensite into a more stable structure and improve the toughness and plasticity of the drill pipe.

Notes
1. The quenching medium should be selected correctly. Different quenching media should be selected for drill pipes of different materials to ensure the quenching quality.
2. The heating temperature should be controlled well. Too high or too low will affect the quenching effect of the drill pipe.
3. Pay attention to controlling the quenching time and speed during quenching. Too short quenching time or too fast speed will affect the quenching effect.
4. The tempering temperature should be appropriate. Too high or too low will affect the tempering effect. It is recommended to select an appropriate tempering temperature according to the specific material.

Common problems
1. Cracks appear on the drill pipe after quenching: It may be that the quenching temperature is too high or the quenching medium is not selected properly. The quenching temperature can be appropriately reduced or the quenching medium can be replaced.
2. The hardness of the drill pipe is not enough after quenching: It may be that the quenching temperature is too low or the quenching time is too short. The quenching temperature can be appropriately increased or the quenching time can be extended.
3. Oxide scale appears on the surface of the drill pipe after quenching: It may be that the quenching medium contains oxides. The quenching medium can be replaced or inhibitors can be added.

Summary
In short, drill pipe quenching is an important process to improve the strength and wear resistance of drill pipes. It is necessary to master the correct quenching techniques and precautions to ensure the quenching quality.