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Quality testing of aluminum die castings

A.Size testing:Inspect the physical dimensions of investment castings according to drawings with inspectionways like line test, three coordinates test,etc.

B.Chemical composition detection:chemical analysis and spectrum analysis to check chemical composition of aluminum die castings.

C.Inspection of mechanical properties:tensile,hardness,impact,ect.

D.Surface quality inspection:

  D1.Visual check:most widely testing way at present.We could find various surface defects of aluminum die castings,like air hole,shrinkage depression,bubble forming,cold insulation,crack,ect.General visual inspection under sunlight or lamplight.Special circumstances with 5 ~ 10 times the magnifying glass to check.

  D2.Dye Penetrant Inspection:Is one of the commonly used methods of checking casting surface defects.It is the nondestructive testing method to find tiny and discontinuous defects.This method is to infiltrate colorant into casting surface defects and remove redundant colorant.After painting eikonogen to castings,due to the effect of capillary,the colorant will be suck out from the castings and made eikonogen coloured.Thus we could judge the postion,size and shape of defects from the image of colour changing.The advanges of this way are like good contrast,clear image,high sensitivity,simple equipment and easy operation.

E.Internal quality inspection:

  E1.Destructive inspection:It is a way to test internal defects by breaking aluminun die castings,which is effective when companied do not have non-destructive flaw detection conditions.We often spot check aluminun die castings and cut the inside to check if there is internal defcts by visual inspection.

  E2.Metallographic examination:This test is usually by checking the microstructure structure of casting alloy.It is often used when determining the casting performance and difficult to determine the nature of defects.Metallographic examination can correctly identify the casting defect is porosity or shrinkage cavity.And could also analysis the reasons for damage castings, etc.

  E3.Ultrasonic inspection:It is a nondestructive testing way rapidly testing out internal defects of aluminum die castings. 

  E4.X-ray nondestructive flaw detection:A method Using X-ray penetrating castings directly casting internal defects by receiving amplifier device or X-ray film.Its disadvantage is that the X-ray is harm to human body,so protective measures must be done.

  E5.Confined compression test:A way used to test the compactness of aluminun die castings.Normally we press water with certain pressure or compressed air into the sealed casting cavity.If there are defects like penetrating cracks cold insulation, porosity and shrinkage in the aluminum die castings,then the air or water will come out by casting wall leakage.Thus to discover the existence and location of defects.Tested pressure usually works over 30~50% than the pressure casting itself.Normally leaked air is hard to find for air pressure testing, therefore,we could put the casting into water and casting can be put in water so that leaked gas could be easily found by rising of air bubbles.