Induction heating quenching and tempering process is an ideal method for producing high-strength small-diameter steel pipes

Induction heating annealing and tempering treatment of high-strength small-diameter seamless steel pipes

High-strength small-diameter seamless steel pipe refers to a medium-carbon low-alloy steel pipe with a diameter of 40 to 70mm and a tensile strength greater than 900MPa. This type of steel pipe is mainly used in geological drilling, oil well mining, construction engineering, coal mining, etc. In order to obtain steel pipes with high strength and good toughness, the traditional normalizing treatment and quenching and tempering treatment processes can no longer meet the requirements, and a new heat treatment process must be adopted. The induction heating annealing quenching and tempering process is an ideal method for producing high-strength small-diameter steel pipes. It has been widely used recently and has achieved good results.

(1) Steel pipes for geological drilling. Steel pipes used in core drilling can be divided into drill pipes, drill collars, casings, core pipes, sedimentation pipes and other drilling pipes. According to different drilling depths and rock formation structures, my country divides seamless steel pipes for geological drilling into different levels according to yield strength. The steel grade standards do not stipulate the steel grade to be used, and appropriate low-alloy structural steel pipes can be selected. Steel pipes of D2-75 steel grade and above (including D2-75) are usually called high-strength grade steel pipes. This type of steel pipe is mainly used for drilling holes with a depth of more than a thousand meters and in super-hard rock formations. It is difficult to meet the requirements using traditional normalizing steel pipes. When induction heating quenching and tempering is used, 35CrMo, 40Mn2Mo, 45MnMoB, 40Mn2MoVNb, etc. can all reach high strength levels. The main problem currently existing in steel pipes for geological drilling is to improve the heat treatment process. , from the commonly used normalizing treatment process to the induction heating quenching and tempering process, the mechanical properties and surface quality of the improved steel pipe will be significantly improved.

(2) High-strength steel pipes are used in oil exploration. After the oil and gas drilling is completed, the underground oil and gas layer is closed by the oil pipe and cannot supply oil or gas to the surface. When formally collecting oil and gas, high-energy armor-piercing projectiles are used to penetrate the oil well pipes in the oil layer through perforation technology, and only then can the oil and gas flow enter the surface collection pipeline. The carrier carrying high-energy armor-piercing projectiles is a perforator made of high-strength steel pipes, also known as a perforating gun. A certain number of armor-piercing projectiles are installed in the gun body. When extracting oil and gas, the gun body is put into the oil and gas layer of the oil and gas well from the surface wellhead, and the oil gas flow is detonated from the ground into the oil pipe and rises into the collection pipeline. The material of the perforating gun body should have high strength, high toughness, and small deformation. After blasting, it should be smoothly lifted from the oil and gas well to the ground. The expansion of the gun body formed at the blind hole during blasting should not exceed 3mm. This kind of high-strength, high-toughness seamless steel pipes are all imported. After research by the author, the 35CrMo steel pipes produced by the induction heating quenching and tempering process have completely replaced the imported steel pipes. Perforators made of 35CrMo steel pipes are used on land. It has been applied in oil and gas wells and offshore oil and gas wells.

(3) High-strength steel pipes for static penetration testing of construction engineering foundations. In the construction of high-rise buildings, large bridges, port projects, etc., it is necessary to detect their basic geological properties and structures. The detection of these deep pile foundations requires the use of stronger drilling tools in order to drill smoothly into the rock formations. The penetration strength and tensile strength of 40Cr and other steel pipes that have been quenched and tempered by induction heating are higher than those of normalized steel pipes.