WO2021085846A1 - Electropolishing apparatus - Google Patents

Abstract

The present invention relates an electropolishing apparatus and, more specifically, to an electropolishing apparatus which is used when the inner surface of a stainless tube is subjected to surface treatment, the electropolishing apparatus comprising: an electrolysis tank having an inner receiving space in which a workpiece to be electropolished and an electrolyte are received; an anode jig provided at one end of the workpiece to fix the workpiece; an electrode rod spaced a predetermined distance apart from the workpiece; a cathode jig provided at one end of the electrode rod to allow the electrode rod to be fixed while being spaced apart from the workpiece; and a rectifier supplying current to the anode jig and the cathode jig.

Description

Electrolytic polishing device

The present invention relates to an electrolytic polishing apparatus, and more particularly, to an electrolytic polishing apparatus used for surface treatment of an inner surface of a stainless steel tube.

Recently, in the field of ultra-precision processing, various research results and the development of new processes are constantly being made. Also, with mass production as the main purpose, various mechanical production and processing methods are being used.

Surface treatment technologies such as mechanical processing or electropolishing processing are technologies that physically or chemically attach metals and non-metals or change surface properties in order to improve the aesthetics and durability of materials and parts, or to impart functionality.

In recent years, the rapid growth of related markets and the application of complex multifunctional surface functions have enabled the creation of various markets, resulting in high-efficiency, high-value-added and future-oriented new technologies convergence, and future products such as miniaturization, complex functionalization, eco-friendly energy saving and high productivity. In addition, new concept of surface treatment technology demand and industrialization are in progress through convergence of micro-ization, greening, and IT grafting for countermeasures to the industry.

Meanwhile, as a mechanical processing method, since the tool is processed by contacting the surface of a material or part, the tool is worn, and after processing, a processing trace in the form of fine irregularities remains on the surface, so that impurities may remain in the trace.

These impurities are not suitable for fields that require high quality and high degree of cleanliness, such as the semiconductor industry, medical and pharmaceutical industries, high-tech new material industries, and food hygiene and cleaning industries, which are rapidly growing in recent years.

Particularly, in the case of tubes and fittings for supplying high-purity gas in the semiconductor industry, extremely clean and high-precision conditions are required to prevent corrosion and gas pollution.

In addition, in the case of tubes used in medical/pharmaceutical and food hygiene fields, microscopic defects on the surface can cause corrosion and bacterial growth on the surface, so that the final product has a fatal adverse effect.

Therefore, electro-polishing (EP) is required, which is a non-contact polishing method that has escaped from the contact method's inner and outer surface polishing machining method. Electrolytic polishing is applied to various industrial fields that require both surface precision and cleanliness, such as semiconductor manufacturing equipment, food hygiene equipment, medical equipment, ultrapure water manufacturing equipment, high purity gas containers, precision molds and nuclear equipment.

Electrolytic polishing is a polishing method using an electro-chemical reaction, and is a polishing method that improves surface smoothness, glossiness, corrosion resistance, etc. by using metal elution from the surface of the anode by using the workpiece as the anode and the electrode as the cathode.

When the work as the positive electrode and the electrode as the negative electrode are put in an appropriate electrolyte and a current is applied, a trace amount of oxygen is generated on the positive electrode side and the metal is dissolved, and a large amount of hydrogen is generated on the negative electrode side by the dissolution action. This takes advantage of the phenomenon that when electricity is applied to a metal of a certain shape, current is concentrated in corners, sharp parts, and irregular parts. Electrolytic polishing is basically a processing method that utilizes the elution of metal, and when this method is used, current is concentrated in the protruding portion of the anodized layer, so that the polishing through metal melting proceeds rapidly.

On the other hand, stainless steel tubes containing about 10 to 11% chromium have characteristics such as corrosion resistance, high hardness, low maintenance cost, low cost, and high gloss, so they are suitable to be applied as Bio Processing Equipment (BPE) standard stainless steel tubes. It can be used in various industrial fields such as semiconductors, food and beverages, and automobiles.

Therefore, in order to manufacture a stainless steel tube as described above, an electrolytic polishing method is more suitable than mechanical polishing, and it is necessary to develop a non-contact surface-treated metal electrode for this.

Conventional Korean Patent Publication No. 10-2014-0002964 relates to an electrode for electrolytic polishing of tubes and pipes, and provides a front electrode, middle electrode, rear electrode, and guide to reduce defects caused by electrode during electrolytic polishing. However, it was difficult to form an optimal oxide thin film through fine separation.

An object of the present invention is to provide a non-contact surface treatment electrolytic polishing apparatus having excellent electrical conductivity capable of forming an optimal chromium oxide thin film upon surface treatment of a stainless steel tube.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems to be solved by the present invention not mentioned here are those of ordinary skill in the technical field to which the present invention belongs from the following description. Will be clearly understood.

An electrolytic polishing apparatus according to an embodiment of the present invention for solving the above problem includes an electrolytic cell in which a workpiece to be electropolished and an accommodation space for receiving an electrolyte are provided therein, and the workpiece is fixed at one end of the workpiece. A positive electrode jig provided so as to be provided, an electrode rod disposed spaced apart from the work piece at a predetermined interval, a negative electrode jig provided at one end of the electrode rod so that the electrode rod may be spaced apart from the work piece, and a current in the positive electrode jig and the negative electrode jig It is configured to include a rectifier to supply.

Preferably, the electrolyte is characterized in that it is a mixture of sulfuric acid, phosphoric acid and ultrapure water.

Preferably, a circulation pump for circulating the electrolyte in the electrolytic cell is further provided.

The electrolytic polishing apparatus according to the present invention has an effect of providing a non-contact surface treatment electrolytic polishing apparatus having excellent electrical conductivity through an electrolyte solution, an electrolytic bath, a negative electrode jig, a positive electrode jig, an electrode, and a power supply unit.

1 shows a conceptual diagram according to an embodiment of an electrolytic polishing apparatus according to the present invention.

2 is a conceptual diagram showing a stainless tube polishing step according to an embodiment of the electrolytic polishing apparatus according to the present invention.

3 shows the surface roughness of the stainless steel tube according to the current density during electropolishing, and shows that the surface roughness decreases as the current density increases.

4 shows the surface roughness according to the processing time during electropolishing, and shows that the surface roughness decreases as the processing time increases.

5 shows the surface roughness according to the temperature of the surface treatment solution during electropolishing, and shows a trend of decreasing the surface roughness as the temperature increases, but shows that the surface roughness increases at a temperature of the surface treatment solution above a certain temperature. will be.

Specific matters, including the problems to be solved, means for solving the problems, and effects of the present invention as described above, are included in the following examples and drawings. Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings.

The electrolytic polishing apparatus according to the present invention, as shown in FIG. 1, includes an electrolytic cell 1 in which a receiving space for receiving an electrolytic polishing object (A) and an electrolyte solution 2 is provided therein, and the work ( A positive electrode jig provided to fix the work (A) at one end of A), an electrode (3) spaced apart from the work (A) at a predetermined interval, and the electrode (3) is the work (A) A negative electrode jig provided at one end of the electrode rod 3 so as to be spaced apart from the electrode 3 may include a rectifier supplying current to the positive electrode jig and the negative electrode jig.

First, the electrolyzer 1 may be configured with an accommodation space in which the work A and the electrolyte 2 are accommodated.

In electrolytic polishing, the workpiece (A) is placed on the positive electrode using an electrochemical reaction, and the low electrode rod is placed on the negative electrode to improve surface smoothness, gloss, and corrosion resistance by using metal elution from the surface of the positive electrode. It's magic.

Preferably, the work piece (A) may be provided with a stainless steel tube.

In more detail, stainless steel tubes containing about 10 to 11% chromium have properties such as corrosion resistance, high hardness, low maintenance cost, low cost manufacturing and high gloss, so they are used in various industrial fields such as pharmaceuticals, semiconductors, food and beverages, and automobiles. Can be.

The stainless steel tube used as the work piece (A) may have an outer diameter of 1 to 4 inches and a length of 1 to 6 m.

Next, the electrolyte solution 2 may be composed of a mixture _{of sulfuric acid (H 2} SO ₄ ), phosphoric acid (H ₃ PO ₄ ), and ultrapure water (H _{2 O).}

In a preferred embodiment, the ratio of sulfuric acid, phosphoric acid, and ultrapure water in the electrolyte solution 2 is preferably 3:6:1, but may vary depending on the use environment.

In addition, it is preferable that the temperature of the electrolyte solution 2 is 60 to 80°C when surface treatment of the work piece (A).

Next, the anode jig may be provided to fix the work A at one end of the work A.

In addition, the anode jig is electrically connected to the rectifier.

Next, the electrode 3 is characterized in that it is spaced apart from the work (A) at a predetermined interval.

Specifically, the electrode 3 may be made of any one material selected from copper, silver, or platinum.

This is because if copper, silver or platinum has excellent electrical conductivity, stable current supply is possible.

In general, in order to perform surface treatment through electrolytic polishing, the electrode 3 is located on the cathode, the work A is located on the anode where metal melting occurs, and between the electrode 3 and the work A The gap of, the structure and material of the electrode 3, and the size of the work A are important factors.

In a preferred embodiment, the electrode 3 may be formed to have a length of 300 to 500 mm, and may be surface-treated 5 to 10 mm apart from the stainless tube provided as the work (A).

2 is a conceptual diagram showing a step of polishing a stainless steel tube according to an embodiment of the electrolytic polishing apparatus according to the present invention, showing that the stainless steel tube is gradually etched and smoothed, and a chromium oxide thin film is formed.

Next, the cathode jig may be provided at one end of the electrode 3 so that the electrode 3 may be spaced apart from the electrolytic polishing object.

Specifically, the cathode jig is required to prevent electric shock between the work (A) and the electrode (3) during the electrolytic polishing process, and at the same time, it is required to be fixed by maintaining an optimum separation distance.

In addition, the positive electrode jig and the negative electrode jig may be made of an insulating material having strong corrosion resistance and no electrical conductivity.

More specifically, the positive electrode jig and the negative electrode jig may be made of Teflon or insulating rubber.

In the conventional case, the processing distance between the electrode and the object is mainly in the range of 0.1 to 0.7 mm, and the electrolyte solution 2 is flowed at a high speed of about 10 m/s or more at a high current density of ^{50 to 500 A/cm 2.}

This is because electrolytic polishing is not performed properly when the current density is low and the electrode gap is large.

However, when the electrode gap is very close, a spark occurs due to the occurrence of a discharge phenomenon, and a phenomenon in which grooves are formed on the surface of the workpiece (A) becomes a problem.

That is, due to such a problem, a fine jig is required to maintain a fine separation between the electrode 3 and the work A, and in the present invention, the cathode jig may play a role.

Next, the rectifier may supply current to the cathode jig and the anode jig.

Specifically, the rectifier is a configuration provided to stably supply power to the electrode 3 and the work (A).

Specifically, the rectifier may include an input circuit, an inrush current prevention circuit, and a power factor improvement circuit.

In a preferred embodiment, the specifications of the rectifier for stable current supply are shown in Table 1 below.

Primary power	AC 220V ~ 380V
frequency	50Hz, 60Hz
Output voltage	DC 0V ~ 30V
Output current	DC 0A ~ 5000A
Stability	Constant voltage, constant current 1% or less

In addition, the optimized current for each size of the stainless steel tube used as the work piece (A) is shown in Table 2 below.

PIPE SIZE (inch)	Current used
	Ieast	maximum
One	70A	150A
1.5	70A	150A
2	90A	150A
2.5	150A		200A
3	180A		250A
4	350A	600A

Next, a circulation pump for circulating the electrolyte solution 2 in the electrolytic cell 1 may be further provided.

Specifically, the circulation pump may further include a driving unit, a driving motor, and a controller for controlling the speed of electropolishing surface treatment.

In one embodiment, the circulation pump may adjust the temperature of the electrolyte solution 2 from room temperature to 100°C.

In addition, it may be configured to include a cooling function as well as a heating function of the electrolyte solution 2. In this case, when electrolytic polishing is continuously performed over a long period of time, the temperature of the electrolytic solution 2 may gradually increase to exceed a preset value. If the temperature of the electrolyte 2 is 40°C or higher, the processing efficiency may decrease and the processing condition may deteriorate. In such a case, it is necessary to install the cooling device for the electrolyte 2 to manage the temperature of the electrolyte 2.

Hereinafter, the surface roughness of the work piece A according to an embodiment of the electrolytic polishing apparatus according to the present invention will be described with reference to the drawings.

3 shows the surface roughness of the stainless steel tube according to the current density during electropolishing, and it can be seen that the surface roughness decreases as the current density increases.

4 shows the surface roughness according to the processing time during electropolishing, and it can be seen that the surface roughness decreases as the processing time increases.

5 shows the surface roughness according to the temperature of the electrolyte solution 2 during electrolytic polishing. As the temperature increases, the surface roughness decreases, but at the temperature of the surface treatment solution above a certain temperature, the surface roughness increases. , The appropriate temperature can be selected according to the user.

Features of the electrolytic polishing process according to an embodiment of the electrolytic polishing apparatus according to the present invention can be expressed as follows.

An anode electrode (stainless steel tube inner surface), the main reaction: Fe → Fe ²⁺ + 2e ^-

A cathode electrode (metal electrode, 3) the main _{reaction: 2H 2 O + 2e- → H} 2 + 2OH -

According to the reaction as described above, it is possible to process high-speed processing and complex shapes in one process regardless of the hardness and toughness of the stainless steel tube, which is the work piece (A).

In terms of processing speed, in the electrolytic polishing method, current flows by the electrolyte (2) flowing through the stainless steel tube, and the resistance between the anodes is proportional to the gap g between the inner surface of the stainless steel tube and the surface of the electrode (3). It is inversely proportional to the electrode area S and the conductivity of the electrolyte. Therefore, if the current efficiency is 100%, the elution rate of the metal by the electropolishing process is as follows.

dV = S dg

In addition, the electrolytic polishing processing method using the electrolytic polishing apparatus according to the present invention can be performed while maintaining a constant average space gap between the inner surface of the stainless steel tube and the electrode 3, so that the processing completion can be improved.

As described above, it will be appreciated that the above-described technical configuration of the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention by those skilled in the art.

Therefore, the embodiments described above should be understood as illustrative and non-limiting in all respects, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and the All changes or modifications derived from the equivalent concept should be construed as being included in the scope of the present invention.

A: Workpiece

1: electrolyzer

2: electrolyte

3: electrode

Claims (3)

1. An electrolytic cell in which a receiving space for receiving an electrolytic solution and a workpiece to be electrolytically polished is provided therein;

   An anode jig provided to fix the work at one end of the work;

   An electrode disposed spaced apart from the workpiece at a predetermined interval;

   A negative electrode jig provided at one end of the electrode rod so that the electrode rod is spaced and fixed to the work piece; And

   And a rectifier for supplying current to the anode jig and the cathode jig.
2. The method of claim 1,

   The electrolytic polishing apparatus, characterized in that the electrolyte is a mixture of sulfuric acid, phosphoric acid and ultrapure water.
3. The method of claim 1,

   Electrolytic polishing apparatus comprising a; circulation pump for circulating the electrolyte in the electrolyzer; further provided.

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