What aspects need to be paid attention to when using high frequency induction heating equipment to heat treat drill pipe joints?

When round steel is used to make drill pipe joints, due to the high content of alloy elements such as chromium, the brittle sensitivity of the drill pipe joints during tempering treatment is high, so it must be watered in time after tempering with high-frequency induction heating equipment. Cooling treatment is done in order to quickly avoid the temper brittle temperature zone. In addition, because the hardness of the drill pipe joint is high, it is necessary to control the hardness of the joint within an appropriate range for cost and efficiency.

Since the required temperature range of the joint is very narrow, the uniformity of the equipment should be controlled within 5°C during quenching and heating, and the temperature during tempering should be controlled at about 10°C, so that the hardness of the drill pipe joint will be uniform. During the conditioning process, in order to ensure that the mechanical properties of the joints of the drill pipe can meet the technical requirements, during the heating and cooling process, a distance must be kept between the joints, and the cooling medium circulates back and forth, so that the joints can be fully cooled and obtained. Required martensite or sorbite structure.

After the drill pipe joint is heat-treated by high-frequency induction heating equipment, if cracks appear on the surface and inside, it is necessary to find out the cause in time. In most cases, it is because the cooling rate of the cooling medium is too high. The alloy steel of the joint has high hardenability, so it is necessary to control the concentration of the cooling medium or reduce the cooling speed to reduce the quenching stress and prevent the occurrence of quenching cracks.

For welded drill pipe joints, fractures will still occur during heat treatment, because the tempering temperature is low and the time is short, and the welded parts are not fully tempered. There is still a lot of internal stress in the joint. Therefore, we will perform repeated forging or uniform annealing treatment on it to completely eliminate the defects of the banded structure, eliminate internal stress, homogenize the structure, prevent the occurrence of quenching cracks, and improve the cutting performance of the drill pipe joint. In addition, it is necessary to improve the heat treatment process in a timely manner to ensure that the high-frequency induction heating equipment can correctly execute the process parameters such as quenching heating temperature, tempering temperature and heating time, fully temper and eliminate the strip-distributed martensite.