Blackening of fasteners of Su Magnetic portable magnetic particle inspection machine

The blackening problem caused by fasteners in the phosphating of wire is manifested as too thick phosphating film, which will cause flake off and affect the adhesion of the blackening film layer in serious cases. The portable magnetic particle inspection machine displays some welded surface and internal defects on parts and parts to assess the quality of the workpiece. Shows the location, shape, and size of the discontinuities. It can detect some minor cracks, hairlines, white spots, folds, inclusions and other defects on the surface of the material, with high detection sensitivity, and can intuitively show the location, shape, size and severity of the defect, and check the repeatability of the defect. It has been widely used in the inspection of pipes, bars, profiles, welding parts, machine workpieces and forgings, especially in the inspection of pressure vessels and bearings. When the workpiece is magnetized, if there is a defect on the surface of the workpiece, magnetic leakage is generated due to the increase of the magnetic resistance at the defect, forming a local magnetic field, and the magnetic powder shows the shape and position of the defect here, so as to determine the existence of the defect.

The magnetic particle flaw detector can be divided into DC magnetization method, half-wave DC magnetization method and AC magnetization method according to the different magnetization current. After tempering in the heat treatment process, the surface of the heating element of the instrument will produce red and rust. When the workpiece is magnetized, if there is a defect on the surface of the workpiece, magnetic leakage is generated due to the increase of the magnetic resistance at the defect, forming a local magnetic field, and the magnetic powder shows the shape and position of the defect here, so as to determine the existence of the defect. The magnetic particle flaw detector can be divided into DC magnetization method, half-wave DC magnetization method, and AC magnetization method according to the different magnetization current. The solution to this problem, such as pre-treatment of fasteners before feeding into heat treatment, that is, cleaning by alkali or acid method to remove the phosphating film on the surface of the workpiece.

How to load a removable solenoid:

Removable electromagnetic coil according to the length of the steel castings, the magnetic particle flaw detection machine can be added to one or two removable electromagnetic coils as necessary, so when to match one and when to match both ends?

Condition with a removable magnetized electromagnetic coil: when the steel part is very short within 600mm, the magnetic particle flaw detection machine has a removable magnetized electromagnetic coil that can be magnetized on the steel part as a whole, and when the steel part is very long beyond 1500mm, the magnetic particle flaw detection machine can choose a removable magnetized electromagnetic coil to carry out vertical magnetization on the steel part.

With two movable magnetized electromagnetic coils: when the steel is within 1500mm, two movable magnetized electromagnetic coils can be used to carry out a vertical magnetization on the steel; When the steel parts are within 2000mm, two movable magnetized electromagnetic coils can be selected, but the fixed magnetized electromagnetic coils must be added on both sides of the electrical level of the magnetic particle detection machine to ensure the overall vertical magnetization of the steel parts.

The difference between the identification of magnetic marks on electrification and welding seam of Su Magnetic particle inspection machine

First, power:

1, the use of continuous magnetization to clear the power time to ensure that the magnetic powder can be used in the case of power;

2, the use of remanent magnetization method, the magnetization time is generally 0.2-1s, the use of impulse current should be more than 10ms, more than two consecutive power. If the Su magnetic portable magnetic particle flaw detector can have sufficient magnetic potential when detecting the flaw, it can not be restricted in accordance with this regulation.

Second, weld:

1, one is to implement heat treatment of the weld after welding, it is necessary to implement flaw detection after the final hot processing.

2. For the crack detection of the gap and pressure vessel after hot processing, the magnetization method should not use the direct current method.

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Some characteristics that are often shown in the inspection of welds:

① Cracks: For the use of steel to build structures and pressure special equipment, there may be welding cracks and heat treatment cracks that are not found and eliminated in time during the manufacturing process, and there will be stress corrosion cracks, fatigue cracks and brittle cracks caused by complex conditions during use. Most of the cracks in the pressure vessel exist in the weld and heat affected zone, but also in other parts where the stress is concentrated and the base material is damaged. When the magnetic particle flaw detector is used for detection, the magnetic marks are generally clear and dense, some are linear, some are curved, some are dendritic, and the welding arc cracks are mostly reflective.

(2) Non-fusion and non-welding: non-fusion is a dangerous defect, second only to cracks, and its magnetic marks are generally wide, shallow and round. In the process of manufacturing and maintenance of pressure vessels, magnetic particle flaw detection machines are easy to find such defects.

③ Slag: the streaks or spots that often occur in slag. The point slag usually exists in the welding metal, the position is not fixed; Strip slag inclusion and molten slag between discontinuous layers or melting lines. Such derogation often coexists with non-fusion, whose magnetic stripe or point-like marking is.

For some magnetic marks proved by the magnetic particle inspection machine, if it is very difficult to judge their authenticity, it is necessary to demagnetize the inspected workpiece.

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