black wood screws

black wood screws

What is black wood screws, and Why should screws be blackened? Blackening is to prevent rust. Screws are not only the blackened surface treatment but also galvanized, hot-dip galvanized and Dacromet treated.

We supply black wood screws with all kind of sizes, Please refer to DIN 7981 and DIN 7982 for specific specifications and detailed description

Black wood screws surface treatment

The normal temperature blackening process of screws is to put the screws in a normal atmospheric temperature without heating or cooling. After soaking the screws in a blackened physical pool for two minutes, the screw surface will produce black. This is a chemical reaction process, which is completely different from the normal oxide blackening of screws. It is only an emergency measure. In the short run, the quality is relatively stable, the operation is simple, the cost is low, with a little bit of pollution, which is acceptable under the system at that time.

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Before blackening, the surface of the screw should be cleaned. If there are too many stains, it is easy to have color difference after blackening. Moreover, the protection time is not long, which will lead to corrosion. Moreover, the Chemical Blackening itself does not have good rust resistance.

Screw blackening at room temperature can theoretically save some energy consumption, which is also the value of its existence. Normal screw oxidation blackening takes at least one hour or more, while this Chemical Blackening only takes less than five minutes, greatly improving the production efficiency. Blackening is only the chemical reaction on the surface of the screw and has no effect on the screw thread tolerance. After blackening, the screw thread can be removed There is no problem with the no-goes gauge inspection.

black wood screws din 7982

Screws surface steps completed:

1. Cleaning: clean the black parts to be sent out on the medium temperature cleaning machine;

2.  Degreasing: put the cleaned workpiece into the basket, and put the basket together with the workpiece into the degreasing tank with the crane, and the workpiece must be completely immersed in the degreasing solution; the degreasing solution concentration pH value is 12-14, the processing time is 10-30min, and the fluctuation is several times every 3-5 minutes, and the degreasing powder is added when the concentration of the solution is lower than pH12;

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3. Water washing: lift the degreased workpieces, blow out the liquid with an air gun, and then put them into the first clean water tank to clean up and down several times. The water in the pool should be kept flowing during cleaning, and the clean water should be replaced in case of turbidity;

4. Pickling: lift the washed workpiece and blow out the accumulated water and put it into the pickling bath. The workpiece must be completely immersed in the pickling solution. The pH value of the pickling solution is 2-4, the treatment time is 5-10min, and the upper and lower shakes once in the middle;

5. Water washing: lift the pickled workpieces to stay for 1.5-3 minutes and then put them into the second cleaning tank for several times. The water in the pool should be kept flowing during cleaning, and the clean water should be replaced when turbidity occurs;

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6. blackening: lift the washed workpieces, blow out the accumulated water, and put them into the blackening treatment tank. The workpieces must be completely immersed in the blackening liquor; the pH value of the pool solution is 2.5-3.5, and the treatment time is 10-12 minutes;

7.  Water washing: lift the blackened workpiece and stop for 1.5-2 minutes, blow the accumulated liquid with the air gun, and put it into the third cleaning tank for several times. The water in the pool should be kept flowing during cleaning, and the water should be replaced when turbidity occurs;

8. Water washing: lift the workpiece and put it into the fourth cleaning tank, and then clean it up and down several times. The water in the pool should be kept flowing during cleaning, and the water should be replaced when turbidity occurs;

9.  blow dry: lift the workpiece, blow the accumulated liquid with the air gun, and then dry it in the air for 5min;

10. Oiling: put the workpiece into the dehydrated antirust oil and put it into the material box after soaking, and treat it up and down for 3-4 times.

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