Production process of high strength black bolt:
Rack mounting → oil removal by boiling alkali solution → water cleaning → rust removal by hydrochloric acid solution → water cleaning → boiling water heating → oxidation → water cleaning → saponification → water cleaning → self drying → hot oil soaking → oil control → inspection → warehousing.
Quality inspection method of high strength black bolt
Place the high-strength black bolt under the fluorescent light source, 300 mm away from the naked eye, and observe its surface. If the color is uniform and there is no obvious spot and rust, it is good, and the color is black or blue black.
Loose test of oxide film: drop a few drops of 3% copper sulfate solution on the high-strength blackened bolt after degreasing, and it is qualified if there is no copper color within 30s.
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