How To Detect Weld Quality After Welding

How to detect weld quality after welding

In Hebei Huayang Steel Pipe Company, after welding is completed, we will use various methods to detect the weld quality to ensure that the products meet the high quality requirements, as follows:

Visual observation: technicians will directly observe the weld surface with the naked eye to check whether there are defects such as undercut, blowhole, crack, incomplete fusion, flash, pit, etc., to see whether the weld is well formed, whether the weld width and height meet the design requirements, and whether the transition is smooth.

Measuring tool measurement: use tools such as weld inspection ruler to measure the size parameters such as the excess height, width and offset of weld to ensure that it is within the specified tolerance range.

Radiographic detection (RT)

Using X-ray or γ-ray to penetrate the weld, because the defects in the weld (such as porosity, slag inclusion, incomplete penetration, etc.) are different from the absorption and attenuation of the weld metal, different gray images will be formed on the X-ray film. By observing and analyzing the images on the film, whether there are defects in the weld and the types, sizes and positions of the defects can be judged.

It is mainly used to detect the volume defects in the weld, and has high sensitivity to detect defects such as porosity and slag inclusion.

The ultrasonic flaw detector emits ultrasonic wave into the weld. When the ultrasonic wave propagates in the weld, it will be reflected, refracted and scattered when it encounters defects. The detector receives the reflected ultrasonic signal, converts it into an electrical signal, and displays a waveform on the display screen. According to the characteristics and parameters of the waveform, it can judge whether there are defects in the weld and the location, size and nature of the defects.

It has high sensitivity to detect surface defects such as cracks, and the detection speed is fast and the cost is low, but the qualitative and quantitative analysis of defects is relatively complicated, which requires inspectors to have rich experience and professional knowledge.

It is suitable for detecting defects on the surface and near the surface of ferromagnetic materials. It has high detection sensitivity for cracks, hairlines, folds and other defects on or near the weld surface.

After cleaning the weld surface, apply magnetic powder or magnetic suspension on the surface. When there is a defect on the surface or near the surface, due to the change of permeability at the defect, a leakage magnetic field will be generated, and the magnetic powder will be adsorbed to form magnetic marks. The defect can be judged by observing the shape, size and distribution of the magnetic marks.

It is mainly used to detect surface opening defects of non-porous materials. The penetrant containing color dye or fluorescent agent is coated on the weld surface to make it penetrate into the defect, then the excess penetrant is removed, and then the developer is coated, so that the penetrant in the defect is adsorbed to the surface to form a display trace, and the existence and position of the defect can be judged by observing the display trace.

Defects such as cracks, pinholes and looseness on the weld surface can be detected, but internal defects cannot be detected, and the detection effect of weld with rough or oily surface may be affected.

Tensile test: the tensile sample is cut from the weld and tested on the tensile testing machine to determine the tensile strength, yield strength, elongation and other mechanical properties of the weld metal, and evaluate the performance of the weld under tension.

Bending test: by bending the weld sample, check whether there are cracks and other defects in the weld during bending, and assess the plasticity and toughness of the weld.

Impact test: the weld sample with notch is subjected to impact test on an impact testing machine to determine the impact absorption work of the weld metal, reflecting the fracture resistance of the weld under impact load.

metallographic analysis

The weld and heat affected zone were sectioned by metallography, and the metallographic structure, such as grain size, phase composition and microstructure, was observed by metallographic microscope, and the microstructure transformation of the weld during welding was analyzed to judge whether the welding process was reasonable and evaluate the performance and quality of the weld.

Chemical composition analysis

By means of spectral analysis, the chemical composition of weld metal is detected to ensure that the content of various alloy elements in weld meets the design requirements, thus ensuring the performance and quality of weld.