As demand increases, the requirements for bearing steel wire rods continue to increase. For high-quality bearing steel wire rods, it can further improve its energy consumption. It can be upgraded by phosphating process. When high-quality bearing steel wire rods are phosphating, the following eight major matters should be noted to avoid damage to the wire rod. .
1, pickling can not be acid washed. After pickling, the surface roughness of the wire rod is increased, and coarse crystals are formed during phosphating, which is not firmly bonded to the substrate, and it is difficult to achieve multi-pass continuous drawing.
2. After the activation treatment, the wire rod should be kept in the air as much as possible. It should be rinsed with overflow water, that is, the residual acid is washed away, and the wire rod can be separated from the air, which is beneficial for the next treatment.
3. Control of acid ratio. The acid ratio is preferably controlled at 5.5-7.5. Below 5.5, the free acidity in the phosphating solution is too high, which will aggravate the dissolution of the metal matrix; above 7.5, the phosphoric acid has a low phosphoric acid content, and the reaction is slow, making it difficult to form a complete phosphate film.
4. Utilization of accelerators. When NaNO2 is used, it will eliminate the cathodic polarization and facilitate the reaction; Ni2+ will form Ni3(PO4)2, which will provide more active sites, form more crystal nucleus, form fine crystal form, and improve the corrosion resistance of the phosphating film. Sex.
5. Phosphating temperature. The phosphating temperature is controlled at 70-80 ° C, the temperature is lower than 70 ° C, due to the low temperature of the wire rod, the liquid around the wire rod will turn black when entering the pickling tank; the temperature is higher than 80 ° C, the soluble phosphoric acid in the phosphating solution The degree of salt dissociation is increased, and the dissolution of the metal matrix is ​​also accelerated, resulting in an increase in the amount of slag, and the formed phosphating film is coarsely crystallized and ashed.
6. Saponification. The saponification time is critical. The saponification time is 5-15 min, and the non-reactive film shows an increasing trend. After saponification for 20 min, the non-reactive film changes irregularly.
7. The phosphatized and saponified wire rods are fully dried at 80-120 ° C to remove moisture, which is good for rust prevention and drawing.
8. Lightly pull the GCr15 steel wire (section deformation ≤ 20%). The method of increasing the concentration of the saponification solution or lowering the temperature can make the non-reactive film thicker, and the drawing is not using the lubricant, and the produced steel wire has better cleanliness.
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