Magnetic Particle Inspection For Forged Steel Parts
(1) Features Of Flaw Detection For Forged Steel Parts
Forging processing methods are generally divided into two categories: free forging and die forging.
The technological process is: blanking-heating-forging-(trimming)-flaw detection-machining-heat treatment-flaw detection-(surface heat treatment-flaw detection)-surface treatment-finished product delivery.
Among them, the forging process is prone to defects such as cracks, folding and white spots; heat treatment will produce quenching cracks; mechanical processing will produce grinding cracks and correction cracks; surface heat treatment will also produce cracks.
(2) Selection Of Inspection Methods
Generally, a fixed magnetic particle inspection machine is used for circumferential and longitudinal magnetization. If the remanence and coercivity of the material meet the requirements, the remanence method is recommended.
(3) Magnetic particle inspection of crankshaft
Flaw detection method: directly energize circumferential magnetization, check forging cracks, folding, grinding cracks, quenching cracks, and hair lines. The segmented coil is longitudinally magnetized, and the inspection for transverse cracks includes forging cracks, grinding cracks, correction cracks, quenching cracks, etc. Pay special attention to the corners and the edge of the oil injection hole during flaw detection.
Magnetic Particle Inspection Of steel Castings
(1) Features Of Magnetic Particle Inspection For Steel Castings
Steel castings are generally complex in shape, and the types and positions of defects are relatively regular. The main defects are casting cracks, porosity, shrinkage cavities, inclusions, pores and cold partitions.
(2) Selection Of Inspection Methods
Castings are generally small in size, which is convenient for flaw detection on a fixed flaw detector. All castings must undergo circumferential and longitudinal magnetization inspections. The continuous method is used for flaw detection before heat treatment, and the residual magnetism method is generally used for flaw detection after heat treatment. Check for pores and inclusions under the surface, and DC flaw detection should be used. For network cracks, it is best to use fluorescent magnetic particle inspection.
(3) Cam Magnetic Particle Inspection
Flaw detection method: use continuous method to detect the blank, and use the residual magnetism method after heat treatment. The wheel part is inspected by the rod-through method, and the shaft part is magnetized circumferentially by the direct energization method and then longitudinally magnetized by the coil. Focus on checking the cracks at the root.
Magnetic Particle Inspection Of In-service And Maintenance Parts Of Special Equipment
(1) Features Of Magnetic Particle Inspection For In-service And Maintenance Parts
Fatigue cracks and stress corrosion cracks are mainly found. The location of the crack is directly related to the force. The flaw detection conditions of in-service and maintenance parts are poor, and the fatigue cracks are small. If conditions permit, try to use fluorescent magnetic particle detection. For bolt holes, the rod-through method should be used, and technologies such as endoscopes should be borrowed. Small bolt holes can also be inspected by rubber casting method.
(2) Bolt Magnetic Particle Inspection
Bolts are fasteners, which are subject to tension and are prone to transverse fatigue cracks. Therefore, longitudinal magnetization of the coil should be used, and the remanence method and the lower concentration of fluorescent magnetic powder have the best flaw detection effect.
Magnetic Particle Inspection For Special Workpieces
(1) Compression Spring Flaw Detection
First, directly power on to check the longitudinal defects on the steel wire; then use the rod-through method to check the lateral defects on the steel wire. Note: The spring should be turned continuously when demagnetizing.
(2) Flaw Detection Of Extension Spring
First, pull the spring apart (using a tensile machine if necessary) and support it with an insulating rod, so that the spring coils are separated from each other, and then directly energize to check the longitudinal defects on the steel wire. Then insulate each circle of the spring (remove the support rod), and use the rod-through method to detect the lateral defects on the steel wire.
Eternal Bliss Alloy Casting & Forging Co, Ltd.
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