Welding quality inspection methods and national standards

Date：2022-01-24 16:30:13 Views：3079

Welding quality refers to the degree to which the welding products meet the design and technical requirements. Welding quality not only affects the service performance and service life of welding products, but also affects personal and property safety. In welding, due to the different thickness, structure and service conditions of weldment, its joint type and groove form are also different. The types of welded joints include butt joints, T-joints, corner joints and lap joints.

There are many welding inspection methods, which can be generally classified according to the following methods:

（1） By welding inspection quantity

1. When the welding quality is relatively stable, such as automatic welding, friction welding, argon arc welding, etc., after the process parameters are adjusted, the quality changes little and is relatively stable in the welding process. The quality of welded joints can be sampled and tested.

2. Full inspection 100% of all welds or products.

（2） According to welding inspection method

1. Destructive testing

(1) Mechanical property tests include tensile test, hardness test, bending test, fatigue test, impact test, etc;

(2) Chemical analysis test includes chemical composition analysis, corrosion test, etc;

(3) Metallographic examination includes macroscopic examination, microscopic examination, etc.

2. Non destructive testing

(1) Appearance inspection includes dimension inspection, geometry inspection, appearance scar inspection, etc;

(2) Pressure test includes hydraulic test and pneumatic test;

(3) The tightness test includes air tightness test, water carrying test, ammonia test, submerged test, kerosene leakage test, ammonia leakage test, etc.

(4) Magnetic particle inspection

(5) Colouring test

(6) Ultrasonic flaw detection

(7) Radiographic inspection

3. NDT

Nondestructive testing includes radiographic testing, ultrasonic testing, magnetic testing, penetrant testing, etc.

The conventional methods of nondestructive testing include macro inspection with direct visual inspection and detection with radiographic flaw detection, ultrasonic flaw detector, magnetic particle flaw detector, penetrant flaw detection, eddy current flaw detection and other instruments. No instrument and equipment can be used for macroscopic inspection by naked eye, but the naked eye can not penetrate the workpiece to check the internal defects of the workpiece, while radiography and other methods can be detected through a variety of instruments or equipment, which can not only check the internal defects of the workpiece that cannot be checked by naked eye, but also greatly improve the accuracy and reliability of detection.

quality testing

Appearance inspection

Use the naked eye or magnifying glass to observe whether there are defects, such as undercut, burn through, incomplete penetration and crack, and check whether the overall dimension of the weld meets the requirements.

Tightness inspection

Vessels or pressure vessels such as boilers and pipes shall be subject to weld tightness test. Sealing test includes hydraulic test, pneumatic test and kerosene test.

Hydrostatic test: hydrostatic test is used to check the tightness of welds. It is the most commonly used sealing test method in welded vessels.

Pneumatic test: pneumatic test is more sensitive and rapid than hydraulic test. It is mostly used to check the tightness of low-pressure vessels and pipelines. Pass compressed air into the container and apply soapy water on the weld surface. If the soap bubble appears, it is the defect.

Kerosene test: apply white paint on one side of the weld and kerosene on the other side after drying. If there are slight cracks or penetrating pores and other defects in the weld, kerosene will penetrate through, showing obvious oil spots on one side of the paint and showing the defect position.

Nondestructive testing of Weld Internal Defects

Penetrant inspection: penetrant inspection is a nondestructive inspection method that uses the penetration of penetrant with fluorescent dye or red dye to show defect traces. Fluorescent flaw detection and dye flaw detection are commonly used. Spray the cleaned weldment surface with red colorant with good permeability. Wipe the weldment surface until it penetrates into the defects on the weld surface. Then apply a layer of white display liquid. After drying, the colorant infiltrated into the weldment defect is adsorbed by the white display agent due to capillarity, showing the red trace of the defect on the surface. Penetrant inspection can be used for any material with smooth surface.

Magnetic particle inspection: magnetic particle inspection is to magnetize the weldment in a strong magnetic field to make the magnetic line of force pass through the weld. When encountering defects on or near the weld surface, magnetic leakage will occur and attract magnetic iron oxide powder scattered on the weld surface. The location and size of the defect can be determined according to the trace of iron powder adsorbed. Magnetic particle inspection is only applicable to the inspection of defects on or near the surface of ferromagnetic materials.

Radiographic examination: radiographic inspection includes X-ray and y-ray inspection. When the ray passes through the inspected weld, if there is a defect, the attenuation degree of the ray passing through the defect is small. Therefore, the sensitivity on the negative film on the back of the weld is strong. After the negative film is washed, black spots or stripes will be displayed at the defect part. The X-ray irradiation time is short and the speed is fast, but the equipment is complex, the cost is large, the penetration ability is smaller than that of y-ray, and the thickness of the tested weldment shall be less than 30mm. The y-ray inspection equipment has the advantages of light weight, simple operation and strong penetration ability, and can cast 300mm steel plate. There is no need for power supply during transillumination, which is convenient for field operation. However, when detecting welds less than 50mm, the sensitivity is not high.

Ultrasonic examination: ultrasonic inspection uses the principle that ultrasonic can propagate in the metal and reflect and refract when encountering the interface of two media to inspect the internal defects of weld. When the ultrasonic wave enters the interior from the surface of the weldment through the probe and encounters defects and the bottom surface of the weldment, it will be reflected. After being received by the probe, the pulse waveform will be displayed on the screen. According to the waveform, whether there is a defect and the defect position can be judged. However, the type and size of defects cannot be judged. Since there is a reflecting surface between the probe and the test piece, the coupling agent shall be applied on the surface of the weldment during ultrasonic inspection.

Post weld treatment

Post weld treatment includes correction of workpiece deformation after welding, grinding of reinforcement, joint cleaning, local or overall heat treatment of components after welding, etc.

National welding standards include:

1. Welding quality gb6416-1986: technical factors affecting the quality of steel fusion welded joints: this standard is applicable to rigid fusion welded joints of pressure vessels, steel structures, crane lifting equipment, ships, construction machinery, transportation equipment, etc. The listed technical factors are used as review items. However, for a specific product, it is not necessary to consider all technical factors.

2. Welding quality gb6417-1986 classification and description of weld defects in metal fusion welding: this standard is applicable to metal fusion welding. This standard is equivalent to ISO 6520-1982 description of weld defect classification of metal fusion welding.

3. Welding quality cb999-1982 inspection method of hull weld surface quality: this standard is applicable to the inspection of hull weld surface quality of civil ships made of low carbon steel and low alloy structural steel. Other ship welding structures can be implemented by reference.

4. Welding quality jb3223-1983 welding rod quality management procedure: this procedure is applicable to all types of manual arc welding flux covered electrodes. The electrode manufacturer, supply department and user department must strictly follow this procedure.

5. Welding quality JB / zq3680 weld appearance quality: this procedure is applicable to the weld appearance quality inspection of all metal welding welds. Relevant welding plants and sellers shall follow this procedure according to the color.

The above contents are related to the welding quality inspection compiled by the core testing team. I hope they can help you. Chuangxin testing is a professional testing organization for electronic components. At present, it mainly provides integrated circuit testing services such as capacitance, resistance, connector, MCU, CPLD, FPGA, DSP and so on. Specializing in functional testing of electronic components, incoming appearance testing of electronic components, anatomical testing of electronic components, acetone testing, X-ray scanning testing of electronic components and RoHS component analysis testing. Welcome to call, we will serve you wholeheartedly!