Phosphatization technology for hot rolling steel plate under normal temperature

Abstract

The invention discloses a phosphatization technology for a hot rolling steel plate under normal temperature, a phosphatization liquid employed in the technology comprises the following components: 34-38g / L of manganese dihydrogen phosphate, 44-48g / L of zinc nitrate, 5-7g / L of 85% of phosphoric acid, 3-4g / L of dibismuth trimolybdenum dodecaoxide, 5-7g / L of sodium tungstate, 1-3g / L of sodium chlorate, 4-6g / L of ammonium citrate, 24-28g / L of sodium nitrate, 2-4g / L of cupric nitrate, 8-10g / L of tartrate, 3-5g / L of ethylene diamine tetraacetic acid, 2-4g / L of urotropine and the balance of water. The phosphatization technology comprises the following steps: performing alkali washing to remove oil stain, flushing by clear water for 2-3 times after being removed from a lye tank, then placing in a phosphatization groove filled with the phosphatization liquid composed of the above components, controlling pH value of the phosphatization liquid at 3.5-4.5 and the temperature of 10-30 DEG C, immersing for 8-12 minutes; flushing for 2-3 times by clear water after being removed from the phosphatization groove, and then drying in air or naturally dying.

Description

technical field [0001] The invention relates to the technical field of surface treatment, in particular to a normal-temperature phosphating process for hot-rolled steel plates. Background technique [0002] The surface phosphating process before steel coating can be divided into zinc-based, zinc-calcium-based, manganese-based, ferrous phosphate-based and alkali metal phosphating. The above-mentioned phosphating systems are selected by different companies for their different advantages. in use. Among them, iron-based phosphating has the advantages of easy control of the solution, stable bath solution, fast phosphating speed, low solution temperature, less sediment, long service life of the solution, no harmful environmental pollutants, and lower cost than other types of phosphating solutions. Much cheaper, but its corrosion resistance is not satisfactory. Zinc phosphating is widely used by most enterprises because of its uniform and fine film layer, good decorative performa...

AI Technical Summary

Problems solved by technology

Among them, iron-based phosphating has the advantages of easy control of the solution, stable bath solution, fast phosphating speed, low solution temperature, less sediment, long service life of the solution, no harmful environmental pollutants, and lower cost than other types of phosphating solutions. Much cheaper, but unsatisfactory corrosion resistance

Zinc phosphating is widely used by most enterprises because of its uniform and fine film layer, good decorative performance, strong adhesion to the coating, relatively stable phosphating film layer, and good corrosion resistance. However, the operators of the factory are often at a loss. In addition, the steel surface conditions in the domestic steel market are different (the rolling oil used and its material are very different), and because the phosphating solution market currently has no unified management, the technical operation standardization is lacking. Due to the limited production conditions of enterprises, it is inevitable to cause a series of disadvantages such as inconsistent process specifications. Therefore, it is necessary to propose a more standardized phosphating operation process, production process, and select a phosphating solution with better performance. the basis of

Because in the past, people only emphasized the corrosion resistance of the phosphating film itself, while ignoring the supporting performance of the phosphating film and the coating, so that the thickness of the phosphating film layer was required one-sidedly. In fact, the phosphating film itself does not bear too much corrosion resistance. Corrosion effect, whether the matching performance between him and the coating is good is the key to affect the entire coating system. The medium and high temperature phosphating film is coarse and brittle, with high porosity and high resistance, which is not conducive to the uniform distribution of the electric field on the workpiece, so it is not suitable for Electrophoretic coating and electrostatic spraying

[0003] The room temperature phosphating technology is currently the most active research, the fastest technological progress, and the phosphating technology with broad development prospects. The normal temperature phosphating solution and phosphating process still have such and such defects, so it needs further improvement