JPS5950469B2 - Method for making electrolytic grinding wheels conductive - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for making an electrolytic grinding wheel conductive. In particular, it prevents premature aging of a chemical plating solution, allows chemical plating to be performed in a relatively short period of time, and makes conductive treatment industrialized. This invention relates to an industrially advantageous conductive treatment method that can be carried out through a consistent manufacturing process.

Generally, an electrolytic grinding wheel includes a conductive part for electrolytically processing a workpiece and an abrasive part for mechanically grinding.

Conventionally, graphite grinding wheels, metal bond grinding wheels, etc. that have been used as grinding wheels for electrolytic grinding have disadvantages such as weak mechanical grinding properties or the inability to dress or true the external shape of the grinding wheel. there were.

On the other hand, vitrified bond grinding wheels allow dressing and truing and have excellent mechanical grinding properties, but because the vitrified bond that binds the abrasive grains is an insulator, this vitrified bond grinding wheel is used for electrolytic grinding. In order to use it as a grindstone, it is necessary to apply a conductive material such as metal or graphite as a film or particles to the surface of the grindstone or the walls of the pores to form a conductive path.

As a means for forming this conductive metal film, for example, silver,
A grindstone is impregnated with a suspension containing fine nickel particles,
A known method is to heat the grindstone at a high temperature of about 1000°C and use a reduction method to burn silver and nickel onto the surface and inside the pores of the grindstone to form a coating. Therefore, in the above method, it is necessary to perform preheating and slow cooling over a long period of time, which is not only unsuitable as an industrial manufacturing method, but also does not provide satisfactory quality characteristics as an electrolytic grinding wheel. Ta.

Furthermore, in methods that require high-temperature heat treatment,
Conductive treatment cannot be performed with a resinoid bond grindstone or a rubber bond grindstone, which has lower heat resistance than a vitrified bond grindstone.

On the other hand, in recent years, chemical plating methods that do not require electrical equipment have been adopted on a small scale in various fields, replacing the electrolytic plating method that is most commonly used as a plating method. Plating solutions have also become commercially available.

As an example, the composition of a chemical copper plating solution is as follows: Solution A contains copper sulfate as a metal source, Rochelle's salt as a buffer, sodium hydroxide as a conditioner, and Solution B is a formalin solution as a reducing agent. There are others that consist of two liquid compositions.

Conventionally, chemical plating is carried out by mixing and preparing the compositions of the two liquids A and B and storing the mixture, and immersing the object to be plated in the prepared chemical plating liquid, or circulating the liquid by passing it through a grindstone or the like.

As is well known, the plating action at this time is that the copper ions in the A solution are
It is reduced by the reducing agent in the solution and becomes metallic copper, which is deposited and plated on the object to be plated. However, unlike electrolytic plating, this chemical plating solution ages and reduces the plating speed. , as the capacity decreases, it is necessary to replenish and replace with new fluid.

In this case, the plating ability when using already prepared chemical plating as the new solution is as shown in FIG.

In the figure, the characteristic line 0. I, II, and III indicate the plating properties immediately after preparing the chemical plating solution, after leaving it for one day, and after leaving it for two days and three days, and the plating ability decreases as time passes after preparation.

This is because the reducing agent naturally decomposes in the preparation solution over time and copper precipitates before use.

This fact also applies to chemical plating solutions of various compositions in which the above or other metal salts, buffering agents, reducing agents, and the like are appropriately combined.

For this reason, even in the past, during actual plating work, A.
Although we try to use the B2 liquid as soon as possible after preparing it, if we prepare it each time, the efficiency of plating will naturally decrease.

As mentioned above, in the past, there was no process for preparing and supplying chemical plating solutions that could be used continuously in a consistent industrial plating process, and chemical plating solutions were used with low work efficiency and poor plating performance. The current situation is that

In addition, even if chemical metal plating is applied directly to a grinding wheel made of a non-conductive material, the metal cannot be deposited on the surface of the grinding wheel. It is necessary to deposit a substance that will

In view of the above-mentioned conventional problems, an object of the present invention is to solve these problems, prevent premature aging of a chemical plating solution, and perform conductive chemical plating in a relatively short time. It is an object of the present invention to provide a conductive treatment method that can be carried out efficiently and continuously in an industrial manufacturing process.

In the method of the present invention, which achieves the above object, a non-conductive and porous grinding wheel, such as a vitrified bond grinding wheel, is first housed in a pretreatment container, and in the pretreatment step, it is degreased, pickled, and washed with water. Pre-purification treatment, and pre-sensitization treatment with tin chloride, for example, to increase the adhesion of the chemical plating and coat the entire surface of the grinding wheel pore wall with the substance that will serve as the core of the plating, and tin, for example. After performing activation pretreatment to replace palladium, the grinding wheel is placed in a plating treatment container, and a liquid containing a metal salt as a metal source for imparting conductivity and a reducing agent are separated and stored in separate tanks. A predetermined proportion of the plating solution is sucked from each tank into a piston-type liquid feeding device through a regulating valve, etc., and then the mixed plating solution is pumped into the plating processing container by pushing out the piston of the piston-type liquid feeding device. By supplying under pressure to the plating processing container, the entire surface of the porous grinding wheel, including the inner wall surface of the pores, is mixed with the liquid containing the metal salt and the reducing agent. The gist is that a conductive metal is deposited and plated on the surface.

Next, an embodiment of the present invention will be described below with reference to the illustrated device.

In FIG. 2, 1 is a pre-processing process device, 2 is a conductive process device, 3 is a used liquid processing device, 4 is a drying device, and the grinding wheel 5 before the conductive process is indicated by dotted lines. The finished product 5' is produced by passing between the process devices 1 and 2 and the drying device 4 as shown in FIG.

The pretreatment process apparatus 1 includes a pretreatment container 6, a pretreatment liquid supply tank 7, a heating tank 8, and the like, which are connected to each other by piping as shown.

The conductivity treatment process apparatus 2 includes a plating treatment container 9, a tank 10 for liquid A containing separate and independent metal salts, a tank 11 for liquid B containing reduction. It includes a mixing ratio adjustment valve 12, a piston cylinder 13a of a piston-type liquid feeding device 13 interposed between each tank 10.11 and the plating processing container 9, and an operation control section 13b for the piston cylinder 13a.

The used liquid processing device 3 includes a storage tank 14, a neutralization device 16 for discharging the liquid to the outside through a neutralization tank 15 into which a neutralizing agent is added, and a plating liquid recovery device 19 consisting of a plating liquid storage tank 17 and a recovery reaction tank 18. We carry out pollution prevention treatment and recover chemical plating solution that can be reused.

In the pretreatment process device, pretreatment is performed as follows.

First, the grinding wheel housed in the pretreatment container 6 is washed with water from the water source and supply tank 7, degreased with a 10% NaOH degreasing solution C, rinsed with water, and acidified with a 3.5% HCI pickling solution. Perform pre-purification treatment of washing, rinsing with water, and drying.

Subsequently, a sensitizing solution E having a composition of 210 g of SnCl and 20 to 50 g of HCl is supplied to impregnate the surface of the grinding wheel 5 to coat the surface with tin, followed by light washing with water.

Additionally, PdCl20.5g/1 and pH 3-4
The activation solution F containing the conditioning agent HCI is heated to 50° C. in a heating tank 8 and supplied to replace tin with palladium, and the material that will become the core of plating during the next chemical plating treatment is applied to the pore walls of the grinding wheel 5. Activation treatment is applied to the entire surface of the surface.

After the washing liquid grindstone 5 is completely dried in the drying oven 4 as shown in II, it is placed in the plating processing container 9 of the next conductive processing process apparatus 2 as shown in III.

An example of the composition of the steel chemical plating solution used in this conductive treatment step is as follows.

Copper sulfate CuSO470g/1 (metal source metal salt) A solution......℃ Tsusiel salt R350g/l
(Buffer) Sodium hydroxide NaOH 100g/1 (pH adjuster) Solution B... Formalin HCHO (37%)
(Reducing agent) These A and B liquids are each separated and independent tank 10.11
is housed within.

The regulating valve 12 is set so that liquid B has a volume of 175 to 1/10 of liquid A, and liquids A and B are mixed in the piston cylinder 13a at the above ratio during the piston suction process of the piston type liquid feeding device 13. Inhaled.

The amount of liquid sent at one time is adjusted and set by the operation control section 13b.

In the next piston extrusion process, the mixed liquids A and B in the piston cylinder 13a are supplied under pressure into the plating processing container 9.
The whetstone 5 is forcibly impregnated with pressure.

This operation depends on the type of plating metal, but in the case of copper, it is usually carried out at room temperature, and by the plating treatment in which this impregnated state is kept in contact for a predetermined period of time, copper is precipitated and plated on the entire surface of the grinding wheel 5, such as the pore walls. A conductive film is applied.

This liquid plating process is repeated several times, and then washed with water and dried in a drying oven 4 as shown in IV to complete the finished product 5'.
becomes.

The used chemical plating solution is collected in the recovery processing device 19 by switching the valve 28 to the extent that it can be reused, and recycled as chemical plating solution. The rinsing liquid is treated by a neutralizer 16 or the like together with each used liquid in the pre-treatment process, the rinsing liquid in the container 6, etc., and discharged to the outside.

The liquid feeding of this liquid feeding device 13 is controlled by switching, for example, as shown in FIG.

That is, the grinding wheel 5 is centrally supported in the container 9 via the packing 20, and the spindle shaft hole of the grinding wheel 5 is connected to the cover plate 2.
It is blocked by 1.

Inlet pipes 22a, 22b and delivery pipes 23a, 23b are connected to the upper and lower spaces of the container 9, respectively.

An electromagnetic switching valve 24 is interposed between each inlet and delivery pipe and the piston cylinder 13a, and the switching valve 24 is disposed between each inlet and delivery pipe and the piston cylinder 13a.
4 to the right, the chemical plating solution is introduced under pressure from the introduction pipe 22a, passes through the porous grindstone 5, and is impregnated therewith.

By maintaining this impregnated state for a predetermined period of time, the metal ions in the impregnating chemical plating solution are reduced and most of them are deposited as metal on the adhesion core material on the inner wall surface of the pores of the grinding wheel 5.

Next, when the vacuum pump 26 is activated to evacuate the inside of the container 27, the used liquid impregnated in the grindstone 5 is led out to the container 26 from the delivery pipe 23b.

Also, by switching to the left, it is introduced from the introduction pipe 22b,
It is sent out from the delivery pipe 23a.

By supplying plating from both sides of the grindstone 5 in this manner, the wall surfaces of the pores of the grindstone 5 can be coated with a plating layer having a uniform thickness throughout.

In particular, for grinding wheels with high liquid permeability, the plating solution can be passed through or impregnated with a relatively low liquid feeding pressure, but for grinding wheels with fine grain size and low liquid permeability, the liquid feeding pressure must be set high. There is a need.

This liquid feeding pressure is set by the operation control section 13b.

As the plating progresses, the coating layer of deposited copper becomes thicker, so that the liquid permeability decreases.

Therefore, if the flow of the plating solution decreases with respect to the set liquid feeding pressure, it can be determined that the plating process is almost completed.
The end point of the process is determined from the weight measurement.

The container 9, the piston cylinder 13a, and other liquid-feeding piping are made of a metal material that has been subjected to a passivation treatment for the chemical plating solution, or one that has been coated with a resin.

As described above, according to the present invention, a grinding wheel made of a non-conductive material at room temperature is subjected to conductive treatment to coat the entire surface with a conductive metal film, thereby producing an electrolytic grinding wheel. Therefore, even vitrified grindstones, resinoid bonded grindstones with low heat resistance, etc. can be safely subjected to conductive treatment.

Furthermore, the pretreatment process and the plating process are carried out separately and housed in separate processing containers, so that the work can be carried out continuously and consistently, which is advantageous for industrial production.

Furthermore, the liquid containing the metal salt and the liquid containing the reducing agent are stored in separate and independent tanks in advance, and are automatically mixed and prepared only when the plating process liquid is sent, so the mixed preparation liquid of the two liquids remains unused. This eliminates the condition of being left unused and prevents the chemical plating solution from aging unused.

Moreover, since a piston-type device is used as the liquid feeding device, the amount of liquid fed and the liquid feeding pressure can be easily adjusted.

Therefore, a new plating solution with high plating ability is always supplied to the plating processing container in a predetermined amount and at a predetermined liquid pressure.
The conductivity treatment can be carried out efficiently and in a relatively short time, and the plating solution can be easily stored and managed, making it extremely advantageous as an industrial treatment method.

As described above, this invention makes it possible to provide an industrial conductive treatment method that is advantageous in each treatment process and storage management of plating solutions, and to provide electrolytic grinding and other conductive grinding wheels with excellent conductivity and grindability. Can be manufactured.

The present invention is also an effective method for conducting conductive treatment by chemical plating of nickel, and the chemical plating solution for copper or nickel is not limited to the above-mentioned example. Various known metal salts as metal sources, buffering agents, tone-enhancing and controlling agents used as needed, and reducing agents are used in known combinations and compositions. In addition, as a method of separating and storing one or more of these mixed liquids into two liquids A and B as in the above embodiment, an aqueous solution containing a metal salt as a metal source and a liquid containing a reducing agent may be separated as described above. As long as they are separated, there will be no particular problem even if other buffering agents, Tachoku Kaikai, etc. are mixed in any liquid.

In addition, as a reprocessing method for reusing chemical plating solutions for copper, nickel, etc. using formalin as a reducing agent, the method of Japanese Patent Application No. 50-25397, which was previously proposed by the present inventors,
That is, the used chemical plating solution is brought into contact with metallic copper to decompose the formalin, and then copper or nickel is replenished by electrodialysis, and a portion of the metal salt, buffering agent, and rice cracking are reused as they are. When used for chemical plating, formalin is added as a reducing agent to replenish it, and most of the chemical plating solutions other than the reducing agent can be reused by simply replenishing metal ions as described above. It can be provided to

[Brief explanation of the drawing]

FIG. 1 shows a plating characteristic diagram of a mixed and prepared plating solution, FIG. 2 shows an overall process layout of an apparatus according to an embodiment of the present invention, and FIG. 3 shows a detailed structural layout of the apparatus in a conductive treatment process. 1... Pre-treatment process device, 2... Conductivity treatment device, 5... Grinding wheel, 5'...
Finished product, 6... Pre-treatment container, 9... Plating processing container, 10... Plating solution tank, 11
...Reducing agent tank, 12...Mixing ratio adjustment valve, 13...Piston type liquid feeding device, A...
...Plating solution, B...Reducing agent, C, D, E
, F...Pretreatment liquid.

Claims (1)

[Claims] 1. A grinding wheel made of non-conductive material is housed in a pre-treatment container, and in the pre-treatment process, it is subjected to pre-purification treatment, and further sensitization and activation treatment to remove the substance that will become the core during chemical plating. After adhering the grinding wheel to the pore wall surface of the grinding wheel, the grinding wheel was placed in a plating treatment container, and a liquid containing a metal salt and a reducing agent as a source of conductive metal were housed in separate and independent tanks. and a predetermined ratio from each tank to a pressure-feeding type liquid-feeding device, which is then supplied under pressure into a plating processing container to impregnate the grinding wheel and maintain the impregnated state for a desired period of time. The method is characterized in that conductive metal is precipitated and plated on the walls of the pores, and then the grinding wheel impregnation liquid is discharged, and the process after mixing and suction to the front pressure distribution and liquid feeding device is repeated a desired number of times, followed by washing with water and drying. Method for making electrolytic grinding wheels conductive.