Welded steel pipe in the modern industry has a lot of applications and markets, welded steel pipe we know that it is required to seal the sealing. Sometimes in the pipeline installation and construction, often encounter the phenomenon of weld cracks, such as not timely detection and repair, there is a serious risk, especially in the transmission of flammable, explosive and toxic media pipeline, its harm is very serious. This requires the construction unit, in the steel pipe welding construction, must not neglect the welding quality.

Let's take a look at the types of common weld cracks in the construction.

The cracks in the welding operations are varied. Cracks are sometimes distributed in the heat affected zone; sometimes in the weld surface, sometimes in the weld, sometimes it can be seen, sometimes it must be seen under the microscope; there are transverse cracks and longitudinal cracks; sometimes it occurs when the arc is broken. Although there are many kinds of cracks, but the essence of the crack, there are three types of common:

1.1 hot cracking: it is produced at high temperature, and it is the main form of the crack along the austenite grain boundary. The weld in the crystallization process, in solid phase near due to contraction of the metal solidification and intergranular liquid films bear tensile force that cracking along grain boundaries.

1.2 cold cracking: it is in a very low temperature that the martensite transformation temperature in the vicinity of about 200e~300 degrees Celsius, due to the constraints of the stress, hardening of the structure and the role of hydrogen, welding joints of the crack, that is cold cracking.

1.3 brittle fracture (also known as brittle fracture): when the temperature drops sharply due to the metal and the weld becomes brittle and the phenomenon of the low stress damage, which is known as brittle fracture.