The appearance of the hardware screws we generally look at with the naked eye, see the electroplated black zinc of the screws is not beautiful, there is no spot or something.
2. Density detection of metal screws. Clean the surface oil layer of the fastener with gasoline or cleaning agent, soak it in 3% neutral copper sulfate water for 40-60s, and observe it with the naked eye after the surface is free of water.
3. Corrosion resistance test of metal screws. The surface oil layer of the fastener is cleaned with gasoline or a cleaning agent, and immersed in a 0.17% aqueous solution of sulfuric acid for 20-40 s. After the surface is free of water, it is observed with the naked eye.
4. Test of wear resistance of metal screws. Use gasoline or cleaning agent to remove the surface oil layer of the fastener. The glass tube with the inner diameter of 10mm and the length of 500mm is suspended vertically above the tested fastener. The inspection surface of the fastener is 45° with the glass tube and the distance is 30mm. A funnel is placed above the tube, and 100g of quartz sand with a sharpness of 0.5-1.0mm is placed. The sand is free to fall and impact the surface of the firmware. After the sand is finished, gently wipe the surface of the fastener and soak it in a neutral 0.5%. The aqueous solution of copper sulfate was taken for 30 s, and it was taken out and rinsed with running water, and observed with the naked eye.
5, hardware screw black film cleaning quality inspection. After the blackening of the fastener, before the saponification and oil immersion, 1-2 drops of 10% phenolphthalein alcohol solution on the surface, such as the solution is pink, indicating that the cleaning is not clean.
6, geometric size inspection. According to the structural shape of the fastener and the design of the drawings and process documents, the corresponding work, card and gauge are used for inspection.
7, the number of metal screws inspection.
In the case of batch production, the important appearance should be fully inspected; the appearance of general fasteners is not less than 10 pieces. The density and cleaning quality inspection shall be no less than 1-3 pieces per batch.
2 One-piece batch production or fasteners with special requirements shall be inspected; or according to the sampling of the process documents.
3 If any item in the sampling inspection is unqualified, it shall be doubled for re-inspection. If the re-inspection is still unqualified, it shall be returned for repair or scrapped.