First, heat treatment of seamless steel pipe – annealing
Annealing is to heat the cold-rolled precision bright steel pipe to an appropriate temperature, use different holding times 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 approach a state of equilibrium, obtain good process performance and performance, or prepare the organization for further quenching.

Second, heat treatment of seamless steel pipe – normalizing
Normalizing is to heat the cold-rolled precision bright steel pipe to an appropriate temperature and then cool it in the air. The effect of normalizing is similar to annealing, but the obtained organization is finer. It is often used to improve the cutting performance of the material and is sometimes used as the final heat treatment for some parts with low requirements.

Third, heat treatment of seamless steel pipe – quenching
Quenching is to heat and keep the cold-rolled precision bright steel pipe warm, and then quickly cool it in a quenching medium such as water, oil or other inorganic salts, organic aqueous solutions, etc. After quenching, the cold-rolled precision bright steel pipe becomes hard, but also brittle.

Fourth, seamless steel pipe heat treatment – tempering
In order to reduce the brittleness of cold-rolled precision bright steel pipes, the cold-rolled precision bright steel pipes after quenching are kept warm for a long time at a suitable temperature above room temperature and below 650℃, and then cooled. This process is called tempering.

Annealing, normalizing, quenching, and tempering are the “four fires” in the overall heat treatment. Among them, quenching and tempering are closely related and are often used in combination. They are indispensable.

“Four fires” have evolved into different heat treatment processes with different heating temperatures and cooling methods. In order to obtain a certain strength and toughness, the process of combining quenching and high-temperature tempering is called quenching and tempering. After some alloys are quenched to form a supersaturated solid solution, they are kept at room temperature or a slightly higher appropriate temperature for a long time to improve the hardness, strength, or electrical and magnetic properties of the alloy. Such a heat treatment process is called aging treatment.

The method of combining pressure processing deformation with heat treatment effectively and closely to make the cold-rolled precision bright steel tube obtain good strength and toughness is called deformation heat treatment; heat treatment in negative pressure atmosphere or vacuum is called vacuum heat treatment, which can not only prevent oxidation and decarburization of cold-rolled precision bright steel tubes, keep the surface of cold-rolled precision bright steel tubes smooth after treatment, improve the performance of workpieces, but also pass penetrants for chemical heat treatment.

Surface heat treatment is a metal heat treatment process that only heats the surface of cold-rolled precision bright steel tubes to change the mechanical properties of the surface. In order to heat only the surface of cold-rolled precision bright steel tubes without transferring too much heat into the interior of the workpiece, the heat source used must have a high energy density, that is, to give a large amount of heat energy to the unit area of ​​cold-rolled precision bright steel tubes, so that the surface or local part of the cold-rolled precision bright steel tube can reach a high temperature in a short time or instantaneously. The main methods of surface heat treatment are flame quenching and induction heating heat treatment. Commonly used heat sources include flames such as oxyacetylene or oxypropane, induction current, laser, and electron beam.

Chemical heat treatment is a metal heat treatment process that changes the chemical composition, structure, and properties of the surface of cold-rolled precision bright steel tubes. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the surface of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, nitrogen, or other alloy elements and keep it warm for a long time so that the surface of the workpiece is infiltrated with elements such as carbon, nitrogen, boron, and chromium. After the elements are infiltrated, other heat treatment processes such as quenching and tempering are sometimes required. The main methods of chemical heat treatment are carburizing, nitriding, and metalizing.

Heat treatment is one of the important processes in the manufacturing process of mechanical parts and tools. Generally speaking, it can guarantee and improve the various properties of cold-rolled precision bright steel tubes, such as wear resistance and corrosion resistance. It can also improve the structure and stress state of the blank to facilitate various cold and hot processing.

For example, white cast iron can be annealed for a long time to obtain malleable cast iron, which improves plasticity; if the correct heat treatment process is used for gears, the service life can be increased by several times or even dozens of times compared with gears that have not been heat treated; in addition, cheap carbon steel can have some of the properties of expensive alloy steels by infiltrating certain alloy elements, and can replace some heat-resistant steels and stainless steels; almost all tools and molds need to be heat treated before they can be used.