What Are The Heat Treatment Processes For Welded Pipes?

There are many processes in the processing of welded pipes, and we need to pay attention to every detail. Welded pipes need to go through various processes before application. Heat treatment of welded steel pipes is a very important link in the processing of welded steel pipes. Thermal processing is a metal thermal processing process in which metal materials are heated, kept warm, and cooled in a certain medium, and the metallographic structure of the material surface or interior is changed to control its metal properties.

During the heating and cooling process of the structural welded pipe workpiece, due to the inconsistency of the cooling rate and time between the surface layer and the core, a temperature difference is formed, which will lead to uneven volume expansion and contraction and stress, that is, thermal stress. Under the action of thermal stress, since the temperature of the surface layer is lower than that of the core, the contraction is also greater than that of the core so the core is pulled. pull. That is, under the action of thermal stress, the surface of the workpiece is compressed and the core is pulled.

This phenomenon is affected by factors such as cooling rate, material composition, and heat treatment process. When the cooling rate is faster, the carbon content and alloy composition are higher, the uneven plastic deformation generated under the action of thermal stress during the cooling process is greater, and the residual stress formed is greater.

On the other hand, during the heat treatment process of steel, due to the change of the structure, that is, when the austenite transforms into martensite, the increase of the specific volume will be accompanied by the expansion of the volume of the workpiece, and the phase transformation of each part of the workpiece will cause the volume to grow inconsistently and produce the structure. stress. The result of tissue stress changes is that the surface is subjected to tensile stress and the heart is subjected to compressive stress, which is just the opposite of thermal stress. The size of the organizational stress is related to the cooling rate, shape, chemical composition of the material, and other factors of the workpiece in the martensitic transformation zone.

In order to make the welded pipe have the required mechanical properties, physical properties, and chemical properties, in addition to the reasonable selection of materials and forming processes, the heat treatment process is often essential. In addition, aluminum, copper, magnesium, titanium, etc., and their alloys can also change their mechanical, physical, and chemical properties through heat treatment to obtain different performances.