Seamless steel pipe heat treatment process

Annealing is to heat the cold-rolled precision bright steel pipe to an appropriate temperature, adopt 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 an equilibrium state and obtain good process performance and usability. Or prepare the tissue for further quenching.

Normalizing is to heat the cold-rolled precision bright steel pipe to a suitable temperature and then cool it in the air. The effect of normalizing is similar to that of annealing, except that the obtained structure is finer. It is often used to improve the cutting performance of the material and is sometimes used to meet certain requirements. Not high parts as final heat treatment.

Quenching is to heat and insulate the cold-rolled precision bright steel pipe, and then quickly cool it in a quenching medium such as water, oil, or other inorganic salts, or organic aqueous solutions. After quenching, the cold-rolled precision bright steel pipe becomes hard but at the same time becomes brittle.

To reduce the brittleness of cold-rolled precision bright steel pipes, the quenched cold-rolled precision bright steel pipes are kept for a long time at an appropriate temperature above room temperature but below 650°C and then cooled. This process is called tempering.

Annealing, normalizing, quenching, and tempering are the "four fires" in overall heat treatment. Among them, quenching and tempering are closely related are often used together and are indispensable.

"Four Fires" have evolved different heat treatment processes with different heating temperatures and cooling methods. 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 temperature for a longer period to improve the hardness, strength, or electromagnetic properties of the alloy. This heat treatment process is called aging treatment.

The method of effectively and closely combining pressure processing deformation and heat treatment to obtain good strength and toughness of cold-rolled precision bright steel pipe is called deformation heat treatment; heat treatment performed in a negative pressure atmosphere or vacuum is called vacuum heat treatment. It not only prevents the cold-rolled precision bright steel pipe from oxidation and decarburization, keeps the surface of the cold-rolled precision bright steel pipe smooth and clean after treatment, and improves the performance of the workpiece, but it can also pass in a penetrating agent for chemical heat treatment.

Surface heat treatment is a metal heat treatment process that only heats the surface layer of cold-rolled precision bright steel pipes to change the mechanical properties of its surface layer. To only heat the surface layer of the cold-rolled precision bright steel pipe without transferring too much heat into the interior of the workpiece, the heat source used must have a high energy density, that is, a large amount of heat energy is given to the cold-rolled precision bright steel pipe per unit area so that the cold The surface or part of the rolled precision bright steel pipe can reach high temperatures for a short time or instantly. The main methods of surface heat treatment include flame quenching and induction heating heat treatment. Commonly used heat sources include oxygen acetylene or oxygen propane and other flames, induced 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 layer of cold-rolled precision bright steel pipes. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the surface layer of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, nitrogen, or other alloying elements, and keep it warm for a long time so that the surface of the workpiece can penetrate elements such as carbon, nitrogen, boron, and chromium. After the elements are infiltrated, other heat treatment processes such as quenching and tempering are sometimes performed. The main methods of chemical heat treatment include carburizing, nitriding, and metalizing.

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

For example, after long-term annealing treatment of white cast iron, malleable cast iron can be obtained to improve the plasticity; using the correct heat treatment process for gears, the service life can be doubled or dozens of times longer than that of gears without heat treatment; in addition, cheap carbon steel can be infiltrated into Certain alloy elements have certain properties of expensive alloy steel and can replace some heat-resistant steel and stainless steel; almost all tools and molds need to be heat treated before they can be used.