The Purpose Of Heat Treatment Of Precision Cold Drawn Seamless Steel Tubes

Precision cold drawn seamless steel pipe is a kind of high precision seamless steel pipe material after cold drawing or hot rolling. Because the inner and outer walls of the cold-drawn precision seamless steel pipe have no oxide layer, high pressure and no leakage, high precision, high smoothness, no deformation of cold bending, flaring, flattening and cracking, etc., it is mainly used to produce pneumatic or hydraulic components. For example, a cylinder or a cylinder, which may be a lsaw steel pipe,spiral submerged arc pipe or a seamless steel pipe.

Annealing is to heat the steel pipe to a suitable temperature, using different holding time according to the material and the workpiece size, and then slowly cooling, in order to make the internal structure of the metal reach or close to equilibrium, obtain good process performance and performance, or further quench Prepare for organization. Normalizing is to cool the precision cold drawn seamless steel pipe to a suitable temperature and then cool it in the air. The effect of normalizing is similar to annealing, but the obtained microstructure is finer, which is often used to improve the cutting performance of materials, and sometimes used for some Parts that are not required are used as the final heat treatment.

Quenching is the rapid cooling of steel pipes after heating and holding them in quenching media such as water, oil or other inorganic salts or organic aqueous solutions. After quenching, the precision cold drawn seamless steel pipe becomes hard, but at the same time becomes brittle. In order to reduce the brittleness of the precision cold drawn seamless steel pipe, the precision cold drawn seamless steel pipe after quenching is higher than room temperature and lower than 650 ° C. The temperature is kept for a long time and then cooled. This process is called tempering.

“Annealing, normalizing, quenching, tempering” is the “four fires” in the overall heat treatment. The quenching and tempering are closely related, and often used together, they are indispensable. The “four fires” evolved 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 seamless steel pipe quenching and tempering.

After quenching some alloys to form a supersaturated solid solution, it is kept at room temperature or a slightly higher temperature for a longer period of time to increase the hardness, strength or electrical magnetic properties of the alloy. Such a heat treatment process is called aging treatment.

The method of combining the pressure processing deformation and the heat treatment effectively and closely, so that the precision cold-drawn seamless steel pipe obtains a good strength and toughness is called a deformation heat treatment; the heat treatment in a vacuum atmosphere or vacuum is called vacuum heat treatment. It can not only make the precision cold drawn seamless steel pipe not oxidize, not decarburize, maintain the surface of the precision cold drawn seamless steel pipe after treatment, improve the performance of the workpiece, and can also pass the infiltration agent for chemical heat treatment.
 
The surface heat treatment is a metal heat treatment process in which only the surface layer of the steel pipe is heated to change the mechanical properties of the surface layer. In order to heat only the surface of the precision cold drawn seamless steel pipe without excessive heat being introduced into the interior of the workpiece, the heat source used must have a high energy density, that is, to give a large heat energy on a precision cold drawn seamless steel pipe per unit area, The surface layer or local part of the precision cold drawn seamless steel pipe can reach a high temperature in a short time or instantaneously. The main methods of surface heat treatment include flame quenching and induction heating heat treatment, commonly used heat sources such as aerobic acetylene 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 precision cold drawn seamless steel tubes. 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 for a long time, so that the surface of the workpiece penetrates into carbon, nitrogen, boron and chromium. After infiltration of the elements, other heat treatment processes such as quenching and tempering are sometimes performed. The main methods of chemical heat treatment are carburizing, nitriding and metalizing.

Heat treatment is one of the important processes in the machining of mechanical parts and tooling. In general, it can guarantee and improve the performance of precision cold drawn seamless steel tubes, such as wear resistance and corrosion resistance. It also improves the microstructure and stress state of the blank to facilitate various cold and hot processing. Next, we will do a lot of “there are policies and countermeasures”; the reason is that there is a lack of supervision and enforcement of the relevant rule of law.