JP2002302792A - Method for partially repairing hard chromium plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for partially repairing hard chromium plating in which only the surrounding of the required part of plated layer is repaired when the hard chromium plating on the surface of press die for automobile is broken, a cost-saving and a time-saving are enabled in the repairing of the die. SOLUTION: The part which requires replanting is subjected to alkali electrolytic degreasing by using an alkaline aqueous solution. Subsequently, the surface is activated by electrolysis, the chromium of substrate part is dissolved and, at the same time, the surface is chemically activated. Subsequently, the plated surface is is electrolyzed as an anode for 10-60 sec by using an electrolyte tank. Subsequently, the plated surface acts as a cathode, the current density is gradually increased by a low current density and finally, the electric current is applied for a required time at a required voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromium plating method for partially repairing a press die.

[0002]

2. Description of the Related Art Hard chromium plating of a press die is a known reprocessing method in which a plating film is partially destroyed by a press due to the use of a plating film, thereby necessitating replating. In general, a method is used in which the whole or a part of the plating surface is peeled off and replating is performed thereon. There are chemical methods (immersion in aqueous hydrochloric acid), electrochemical methods (electrolysis using the plating surface as an anode), and mechanical methods (grinding with a grinder, etc.). And time-consuming disadvantages. In the partial repair method, as a method of machining without confining the electroplating in the frame of the electrolytic cell, a carbon electrode is used for the anode, and electrodeposition is performed while applying a chromic acid solution to the base material to be the cathode. There is a method to perform, but the desired hardness cannot be obtained. In addition, when the partial repair was performed, the step was not sufficiently dissolved by the electrolysis, resulting in a clear step, and the entire surface was peeled off and re-plated.

[0003]

Many press dies are provided with hard chromium plating for the purpose of abrasion resistance and slippery releasability. However, there is a huge press die for an automobile having a weight of about 10 Ton. If a huge press die is plated with hard chrome,
Hard chrome plating may be destroyed due to wear and dust. The prior art has required a great deal of expense for mold maintenance. The purpose of the present invention is to repair only the necessary part of the plating layer that was destroyed by pressing. It is a partially repaired hard chrome plating method that solves the problems of cost reduction and short delivery time by obtaining (in terms of hardness and wear resistance).

[0004]

Means for Solving the Problems Fine irregularities are physically formed on the old chromium layer and the exposed underlying portion to increase the adhesion of the hard chromium plating to be repaired, and then the alkaline electrolytic degreasing is performed, and the surface is electrolyzed. When activated, the chromium in the base portion dissolves and the surface is chemically activated. For FCD (spheroidal graphite cast iron), a decarburization treatment is performed. The anode is an iron anode using a plating electrolytic cell. Electrolyze for 10 to 60 seconds in a bath using the plated surface as an anode. By this operation, the surface to be plated is completely degreased and further activated chemically, thereby forming a base material for obtaining a strong adhesion between the surface material and the electrodeposited chromium. Next, the plating surface is used as a cathode, the density is gradually increased from a low current density, and finally, a current is applied at a required voltage for a required time. When the partial repair is performed, the old chromium layer may be peeled off, but is limited to the case where the adhesion between the old chromium layer and the base is complete.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The hardness of a partially plated surface according to the present invention is as follows. The hardness of the plated surface of the plating processed by the current method and the plating of the partially repaired plating are equivalent, and are superior to the partial plating method, which is a known technique of machining. Measurement of hardness of hard chromium plating under normal operating conditions HV966 Hardness of hard chromium plating obtained by the above-mentioned method of partial repair of hard chrome plating HV979 The hardness of plating obtained by a known partial repair plating method Hardness HV 484

[0006]

Embodiment An embodiment according to the present invention will be described. Dimension width 1
A test die of 200 mm in length, 2100 mm in height, 650 mm in height, 3.5 Ton in weight and material FC250 was used as an object of the experiment. The portion where the hard chrome plating is broken is a portion where pressure is relatively applied, and is a portion where the panel slips. The area destroyed is 5mm wide and 100mm long
About three places were destroyed. The area destroyed with respect to the area provided with the hard chrome plating is 1/300 or less. A partially repaired hard chromium plating using hard chromium plating was attempted around the three broken locations.

[0007]

According to the present invention, the press was performed on the basis that it was judged that there was no influence on the press although some irregularities were felt. As a result, there is no problem. Panel scratches have also been reduced. The same panel was obtained as before the hard chrome plating was destroyed. From the above, according to the present invention, a hard chrome plating is applied to a press mold, and the hard chromium plating of a part of the mold is partially repaired by the hard chrome plating without being peeled off and re-plated even if it is broken. It is possible to do. Although an aqueous hydrochloric acid solution is used in the step of removing old chromium by re-plating, the present invention eliminates the need for immersion in an aqueous hydrochloric acid solution and eliminates corrosion of the mold. Also, subtle changes in the panel due to re-plating can be prevented. According to the present invention, hard chromium plating can be performed only on peripheral portions where abrasion resistance and slippage are required, so that significant cost reduction can be achieved. The present invention is extremely useful industrially.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating steps of a partially repaired hard chromium plating method of the present invention.

Claims (4)

[Claims] A partially repaired hard chromium plating method characterized in that only a part of a broken hard chromium plating layer of a press die is partially repaired by hard chromium plating. 2. The method according to claim 1, wherein fine irregularities are physically formed on the old hard chromium plating layer to enhance the adhesion between the old hard chromium plating layer and the partially repaired hard chromium plating layer. Partially repaired hard chrome plating method. 3. The partially repaired hard chromium plating method according to claim 1, wherein no step is formed at an end point of the partially repaired hard chromium plating layer. 4. A hard chromium plating method according to claim 1, wherein the step of the hard chrome plating which has been broken is dissolved by electrolysis to smooth the step and partially repair the step.