JPS5919991B2 - Two-stage pickling method for pure silicon steel materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stage pickling method for removing oxide scale produced after magnetic annealing of pure silicon steel materials.

Armatures and cores made of 10% silicon pure steel plates used in wire spring relays and the like produce oxide scale (silicic acid, iron silicate, iron sesquioxide, iron oxide, etc.) after magnetic annealing.

This oxidized scale is removed in the pickling step of the plating pretreatment step, and a two-stage pickling method is adopted as the pickling method in this case. This two-stage pickling is conventionally performed as follows. (1) First stage pickling: sulfuric acid 150-250θ/l
) Acidic ammonium fluoride 50-759/l) Iron content in liquid 50y
/l of etching solution is heated to a temperature of 60±5°C, and a 1% pure silicon steel plate, which is the material to be treated, is heated to a temperature of 30 to 60°C.
Soak for seconds, then rinse with water for activation.

(2) Post-stage pickling: Electrolytic pickling is performed as post-stage pickling.

This electrolytic pickling uses sulfuric acid 300 to 5009 as the pickling liquid.
/l) Sodium sulfate 100-2001/l) Acidic ammonium fluoride 30-609/l, and the amount of iron in the liquid is 5
This is a method in which electrolysis is performed in a state of 01/n or less, and the applied voltage is 5V.
Above, current density 15A/d77Z', temperature 25-35
Electrolyze for 100 to 200 seconds at ℃. However, according to this conventional method, electrolytic pickling is used for the subsequent pickling process, so the end wash tip of the hooking jig (which is also used in the subsequent plating process) that secures the parts is electrolytically pickled. There is a problem that it dissolves when washed.

As a means for preventing this dissolution, there is a method of using a titanium wire for the tip portion, but since titanium material is expensive, the cost of the jig increases. Furthermore, the conventional method described above has the disadvantage that etch bits are generated on the surface of the material to be treated. In other words, the etching by electrolytic energy and the dissolution mechanism under oxygen gas pressure vary greatly depending on the crystal plane of the material.
When the crystal grains in the surface layer become very small, there are a large number of grain boundaries, and these grain boundaries are partially and selectively etched, resulting in etch pits. If these etch pits occur, the inside of these etch pits will not be cleaned during cleaning after pickling, and the pickling solution will remain. Although the pickling solution remaining in the etch pit does not pose a problem when plating is performed afterwards, it does cause welding defects (in the Beering peel test) during resistance welding of nickel silver sheets after plating. (There is no remaining diameter and it is defective).
This means that microscopically, the fitting and adhesion between the material and the material are poor. Therefore, it is necessary to adopt a pickling method that does not cause etch pits even on the surface of such materials, and one possible countermeasure to this is to increase the viscosity of the pickling solution during electrolytic pickling. This is the second cause of high discharge sludge, so this method of increasing viscosity cannot be adopted. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to be able to completely remove oxidation scale from pure silicon steel materials, to obtain high plating quality without causing etch pits even in the case of unique materials, and to It is an object of the present invention to provide a two-stage pickling method that can greatly reduce wear and tear on jigs.

In order to achieve this object, the present invention is characterized in that a chemical polishing liquid containing hydrogen peroxide and acidic ammonium fluoride as main components is used for the latter stage pickling.

Next, an embodiment of the present invention will be described using scale removal of 1% silicate pure iron and steel material.

Example 1 Example 2 (First-stage pickling) Only NH4F-HF in the pickling solution used in the first-stage pickling in Example 1 above was changed to NaF-HF, and this was used at a concentration of 60 to 809/l. Included.

(Later pickling) Same as Example 1 above.

In addition, the pickling liquid used for the latter stage pickling in the above example was as follows:
This is a chemical polishing liquid made by Mitsubishi Gas Chemical.

In Examples 1 and 2, the following etching characteristics were obtained. (1) The surface becomes specularly glossy and Hmax(
The maximum unevenness depth was approximately 2 to 4 μm, and no etch pits were generated.

(2) The etching amount was 3.8 to 7.6 η/d, and the dimensional reduction was 10 to 30 μ.

(3) After removing the oxide scale, copper-nickel chrome plating was applied, and electrical resistance welding of the nickel silver thin plate was performed, and in the peeling residual diameter test of this weld, it showed very good welding strength. Ta.

(4) In the salt spray test, pinhole test, and adhesion test of the plated product after scale removal, better test results than conventional ones were obtained. Etching was also attempted using only the chemical polishing liquid used in the latter stage pickling of each of the above examples, but uniform etching was not possible, and etch pots were formed on the surface, giving an appearance similar to a semi-glossy or matte surface.

Further, treatment with only hot sulfuric acid, hydrochloric acid, etc. did not provide a glossy surface with a uniform surface finish. As described above, according to the present invention, it is possible to completely remove scale from pure silicon steel materials and eliminate the occurrence of etch pits, so that the adhesion strength or welding strength can be improved in the subsequent plating or welding process. can be obtained.

Claims (1)

[Claims] 1. To remove oxidized scale that occurs after magnetic annealing of pure silicon steel materials, an initial pickling process is performed under heating using an etching solution containing fluoride and sulfuric acid as main components, and then hydrogen peroxide and acidic fluoride are used. A two-stage pickling method for silicon pure iron and steel materials, which is characterized in that a second-stage pickling is performed with a chemical polishing solution containing ammonium chloride as a main component.