Weld defects and weld quality titaium pipe inspection

Hot cracking in the weld metal titanium cn is produced by the process of crystallization of liquid to solid, mostly produced in the weld metal.Its original
For mainly existed in the weld low melting point material, it weakens the connection between the grain, when welding stress is large, it is easy to cause fracture between the grain. Weldment and the electrode containing impurities such as S, Cu, is easy to produce hot crack.
(2) cold crack
Cold crack was produced in the process of cooling after welding, mostly produced in the base metal and weld metal or substrate fusion along the border
Online.The main reason is because of the heat affected zone or inside weld forming quenching organization, in the role of high stress, cause break within the grain Cracking, the welding carbon content is higher or more easily quenching steel alloy elements, the most easily produce cold crack.In the weld fusion into the excess hydrogen, can also cause Crack is one of the most dangerous defect, it besides reducing bearing section, also can produce serious stress concentration, cracks in use will be one by one Gradually expand, finally can lead to the destruction of the component.So the general does not allow this kind of defect of the welding structure, once found to be shoveled to welding.
The necessary inspection of the welding joint is one of the important measures to ensure welding quality.Therefore, after the workpiece welding butt welding should according to the product technology requirement. Seam inspection accordingly, that do not conform to the requirements of the technology allowed by the defects, repair should be carried out in a timely manner.The welding quality inspection, including appearance inspection,NDT and mechanical performance test in three aspects.All three are complementary to each other, and give priority to with NDT.
(a) visual inspection
Appearance inspection general is given priority to with macroscopic observation, sometimes 5 to 20 times a magnifying glass to observe.Through visual inspection, can be found on the surface of weld.
(2) the NDT
Hidden in the inside of the weld slag, porosity, cracks and other defects inspection.At present the most commonly used is to use
X-ray inspection and ultrasonic inspection and magnetic testing.X-ray inspection is the use of x-rays to weld,
According to the negative images to determine how much internal defects, defect and types.According to the product technical requirements for evaluation of weld again whether qualified.
Ultrasound beam, issued by the probe to the metal, when ultrasound beam to the metal and the air interface, it is refracted through the weld.If the weld Have defects in ultrasonic beam reflection to probe and is accepted, the screen will appear the reflected wave.According to the reflection wave and waves than normal A, identification, can determine the size and location of defects.Ultrasonic testing than X light phase is much more convenient and widely used.But ultrasonic testing is often only with operation experience to judge, and I can't leave according to the test.For from the surface of the weld is not deep internal defects and surface tiny crack, also can use magnetic inspection.
(3) the water pressure test and pressure test
(4) on the mechanical properties of the welding test plate test