Petroleum casing pipes are steel pipes used to support the walls of oil and gas wells to ensure the normal operation of the entire oil well after drilling and completion. Each well uses several layers of casing according to different drilling depths and geological conditions. Cement is used to cement the casing after the casing is down. It is different from the tubing and drill pipe and cannot be reused. It is a one-time consumable material. Therefore, casing consumption accounts for more than 70% of all oil well pipes.
There are roughly 4 basic processes for heat treatment of oil casing, namely annealing, normalizing, quenching and tempering, commonly known as the “four fires” of metal heat treatment.
1. Annealing
Annealing is to heat the workpiece to an appropriate temperature, use different holding time according to the material and workpiece size, and then slowly cool it, the purpose is to make the internal structure of the metal reach or close to the equilibrium state, obtain good process performance and use performance, or for further quenching Prepare for organization.
2. Normalizing
Normalizing is to heat the workpiece to a suitable temperature and then cool it in the air. The effect of normalizing is similar to annealing, except that the resulting structure is finer. It is often used to improve the cutting performance of materials, and sometimes used for parts that are not demanding. As the final heat treatment.
3. Quenching
Quenching is to quickly cool the workpiece in a quenching medium such as water, oil, other inorganic salts, and organic aqueous solutions after heating and holding the workpiece. After quenching, the steel parts become hard and brittle. At the same time, low-temperature quenching is lower than the conventional temperature, which reduces the stress of quenching, thereby reducing the deformation of quenching, which ensures the smooth operation of heat treatment production, and provides good raw materials for subsequent wire processing.
4. Tempering
Tempering In order to reduce the brittleness of steel parts, the quenched steel parts are kept at an appropriate temperature higher than room temperature but lower than 750°C for a long time, and then cooled. This process is called tempering.
The heat treatment process of the existing steel-grade petroleum casing pipe is poor in hardenability of the heat-treated product during processing, the mechanical properties of the steel pipe are not good enough, and the protective bending effect is not good, and it is easy to break.
The heat treatment of oil casing pipe needs to be strictly implemented. The produced oil casing has good product quality, exhibits good use value and performance during use, and can maintain high strength and toughness.