KR101873714B1 - Metal block for fluid transportation - Google Patents

Abstract

The purpose of the present invention is to provide a method for manufacturing a new metal block, and a metal block according to the same. It is possible to continuously maintain solid sealing even when repetitive assembling is performed on a metal block having a complicated shape. According to the purpose of the present invention, a metal block made of stainless steel having an oxidized chromium layer present therein is firstly electrolytically polished. Next, an ion nitriding process is performed to form an ion nitriding layer. While a part of the ion nitriding layer is efficiently removed by secondarily electrolytically polishing the same, high concentration surface N and C composite diffusion is induced, and thus the surface of a layer on which an educed phase is present is hardened. Accordingly, hardness of a sealing part of the metal block is increased to Hv400 or greater while corrosion resistance is maintained. Therefore, it is possible to effectively perform metal sealing.

Description

[0001] METAL BLOCK FOR FLUID TRANSPORTATION [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal block for fluid control applied to a semiconductor device, a power generation facility, an offshore plant, an aircraft, and the like, and more particularly to a surface treatment of a metal block.

In a fluid control system such as a gas or liquid, a metal block is a block connecting various valves, regulators, gaskets, and the like, and is a sealing part that is very important in equipment using a fluid having toxicity, corrosiveness, etc. ). Particularly, it is an important part connecting the control section of the valve package and the piping section for controlling the supply and shutdown of the reaction gas during the semiconductor process. In the case of the conventional product, the corrosion resistance is improved by increasing the proportion of the chromium oxide layer by the electrolytic polishing process of the metal block as shown in FIG. 1. Electrolytic polishing is performed on the SS316L metal base material to increase the CrO: FeO layer to 2: 1 or more .

The sealing part of the metal block having such a structure is controlled to about Hv300 after electrolytic polishing so that it can be repetitively fastened. However, corrosion can be caused by the nitrogen concentration gradient among the precipitates precipitated by the electrolytic polishing, There is a problem that leakage occurs at the sealing part. Particularly, due to the characteristics of the material, the crystal grains are stretched due to the precipitation of the material which has been severely treated by forging or drawing, resulting in localized corrosion resistance.

Finally, the metal sealing part is surface-hardened by a physical tool (burnishing tool) to maintain the degree of vacuum due to the rigidity of the sealing. However, there is a problem in implementing high vacuum sealing performance by repeated assembly.

As a conventional technique for solving this problem, ion nitriding is applied, but the above-mentioned problem can not be solved. This is because the nitriding process is performed on the base material of stainless steel at high temperature as shown in FIG. 2 to form an ion nitriding layer, . The surface must be further polished in the process, but it is difficult to apply when the shape of the sealing part in the metal block is complicated.

Japanese Patent Laid-Open No. 10-1237915 discloses a shot peening process after nitriding, but it can not be applied to a product that has been processed into a complicated shape as described above.

Accordingly, an object of the present invention is to provide a method of manufacturing a new metal block and a metal block according to the present invention, which can maintain stable sealing even when repeatedly assembled to a metal block having a complicated shape.

According to the above-mentioned object, the present invention provides a method for manufacturing a high-density surface N, C composite by efficiently performing an ion nitriding process on a stainless steel metal block having a chromium oxide layer and then performing electrolytic polishing to efficiently remove a part of the ion- By inducing diffusion and surface hardening treatment of the layer in which the precipitated phase is retained, the hardness of the sealing part of the metal block is increased to Hv 400 or more while the corrosion resistance is maintained, so that the metal sealing can be effectively performed.

The electrolytic polishing is performed before the formation of the ion nitriding layer as described above, so that the surface treatment with higher quality can be achieved.

According to the present invention, since the metal block is processed into a stainless steel material having excellent processability, it is possible to manufacture a precise and relatively easy shape, and it is possible to secure the surface cleanliness by primary electrolytic polishing, thereby forming an ion- The surface of the ion nitrided layer is slightly polished to remove precipitates which may cause corrosion to prevent galvanic corrosion and to make residual chromium (Cr) as a chromium oxide layer, thereby significantly improving corrosion resistance . Accordingly, the metal block of the present invention can maintain high reliability due to excellent corrosion resistance even when handling toxic gas or corrosive fluid, and even when various units are repeatedly assembled with respect to the metal block, the metal block has high hardness and high corrosion resistance Can still operate reliably and safely.

Figures 1 and 2 show layered structures formed as a result of surface treatment of metal blocks prepared according to the prior art.
3 is a cross-sectional view showing the structure of a chromium oxide layer formed by electrolytic polishing.
4 is a cross-sectional view showing a base material of a metal block and a layered structure surface-treated by the method of manufacturing a metal block according to the present invention.
5 is a flowchart showing a method of manufacturing a metal block according to the present invention and a surface treatment result thereof.
FIG. 6 is a cross-sectional view showing a sealing portion of the metal block and is for explanation of the burnishing process according to the present invention. FIG.
7 is a photograph of a metal block applied to a fluid control system.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The production of the metal block according to the present invention can be carried out by forming the metal block using stainless steel having good workability but lowering hardness as the base metal and then subjecting it to primary hardening and ion nitriding and secondary electrolytic polishing to obtain hardness and corrosion resistance All of them. In the electrolytic polishing (EP) treatment for stainless steel, as shown in FIG. 3, a surface layer of stainless steel having a chromium oxide layer on the surface layer is polished to thin the thickness of the chromium oxide layer to improve surface cleanliness. Electrolytic polishing of forged materials can cause corrosion due to S-phase precipitate phase. Particularly, due to the characteristics of the material, the material which has been severely treated by forging or drawing has crystal grains stretched out, resulting in a locally low corrosion resistance region.

Accordingly, the present invention relates to a method of manufacturing a high-strength stainless steel forging material by processing a metal block and then partially polishing the oxide layer using EP, followed by diffusion of carbon and nitride by an ion nitriding process to form a thick nitride layer even if carbon and nitrogen precipitates are partially diffused Then, the surface layer was electrolytically polished again. The secondary electrolytic polishing removes the surface layer on which the precipitate is formed and maintains the layer mixed with the diffusion hardened layer and makes it glossy.

That is, the chromium oxide layer of stainless steel is thinned through the primary electrolytic polishing, and the ion nitriding layer is thickened and hardened in the state, and the precipitates which are exposed on the surface by the ion nitriding process, And the chromium oxide remaining on the surface of the ion nitriding layer is made into chromium oxide to form a chromium oxide layer, thereby enhancing the corrosion resistance.

The metal block of the present invention has a surface hardness of Hv 400 to Hv 600 when the surface is measured with a load of 300 grams of Vickers hardness to ensure high vacuum sealing and even when a unit for carrying toxic gas or corrosive fluid is repeatedly assembled It does not cause corrosion by the fluid and the lifetime to maintain the sealing function becomes very long. That is, when the hardness is low, the portion pressurized by the gasket is deformed by the high vacuum sealing operation, and the high vacuum sealing function is lost to shorten the service life of the metal block. According to the present invention, This problem is solved.

In other words, FIG. 4 shows an example in which the ionic nitriding method is applied to the sealing part unlike the conventional product of FIG. 1, so that N and C are intruded into the stainless steel in the maximum concentration at a maximum concentration to keep the crystal lattice as much as possible, In which a chromium oxide layer is formed.

(Cr, Fe) xNy is precipitated by N and C which are high-concentration interstitial elements more than necessary in the ion nitriding process. The above process is characterized in that the thickness of the ion nitriding layer (N, C heavily doped diffusion layer) is thickly formed at a high concentration to forcibly maintain the high hardness retention life due to the thickness of the hard hard layer, (Cr, Fe) .sub.xNy precipitates are formed into a chromium oxide layer, and corrosion resistance is improved to the extent that the precipitated solid solution layer is removed by secondary electrolytic polishing.

 Since the metal block product thus obtained has excellent corrosion resistance and durability, it is possible to maintain the sealing function even by repeated assembly, thereby reducing the assembling time and cost of the semiconductor equipment, which leads to an increase in the life of the semiconductor equipment.

The following is a more detailed description of the process.

5 is a flowchart schematically illustrating the process of the present invention.

Metal block is processed with stainless steel base material.

The processed metal block is subjected to the first electrolytic polishing.

The conditions of the electrolytic polishing process are as follows.

A current density of 5 to 20 A / cm ² , an electrolytic solution temperature of 5 to 40 seconds, preferably 10 to 30 seconds, an electrolyte temperature of 40 to 80 ° C, preferably 60 to 70 ° C, 0.5 to 1 mm Maintain electrode spacing.

When the first electrolytic polishing is finished, the thickness of the chromium oxide layer of stainless steel is reduced and the surface cleanliness is improved.

Next, ion nitriding is performed. Ion nitridation is performed by an ion plasma process using a low temperature plasma. Nitrogen is injected at 400 to 800 sccm (600 sccm in this embodiment) at a low temperature of 300 to 600 캜, preferably 400 to 540 캜, to form a high concentration diffusion layer. The process vacuum degree is 0.1 to 1 Torr (0.4 Torr in the present embodiment) and the amount of electric power is 10 to 30 kW (18 kw in this embodiment).

In the ion nitriding process, hydrogen gas is flowed at a rate of 400 to 800 LPM at 100 to 350 DEG C for high-speed diffusion of nitrogen at a high concentration. At this time, the temperature is gradually increased and gradually increased, thereby gradually increasing the current flowing in the ion source in the range of 5 to 20A. As the temperature is raised to 400 ° C, hydrogen and nitrogen are simultaneously flowed and the flow rate of the two gases is made to be 400 to 800 LPM as a whole. The amount of current is increased to 20 to 25A. After maintaining the temperature for 200 to 400 minutes in this state, the temperature is raised to 500 ° C., hydrogen is flowed, and the amount of current is kept lowered for 60 to 100 minutes. Thereafter, nitrogen is flowed and the process is performed for 10 to 60 minutes, and the temperature is lowered to about 300 ° C and maintained for about 10 to 40 minutes. The final step of the process is to terminate by flowing the hydrogen and lowering the temperature from room temperature to about 80 ° C for about 40 to 80 minutes. In the above, the process temperature is controlled to be a positive correlation with the applied current amount, and the process is performed for the longest time in the step of simultaneously flowing hydrogen and nitrogen.

In order to improve the corrosion resistance after forming the ion-nitrided layer in the thickness of 10 to 40 um, a part of the ion-nitrided layer is formed of a chromium oxide layer by a secondary electrolytic polishing process, and the thickness of the chromium oxide layer is set to about 1 to 5 um Surface hardness and corrosion resistance. The conditions of the secondary electrolytic polishing process are the same as those in the above-mentioned primary electrolytic polishing.

Secondary electrolytic polishing improves corrosion resistance and achieves high gloss.

In the above, the primary electrolytic polishing may be omitted depending on the case. In addition, burnishing treatment can be performed before electrolytic polishing to improve the roughness and hardness. This can be applied both before the first electrolytic polishing and before the second electrolytic polishing. That is, the block sealing portion (see FIG. 6) of the metal block is subjected to burnishing treatment after physical processing to raise the roughness and hardness. At this time, it is preferable that the roughness is within Ra 0.15 and the hardness is within Hv300.

The above-described process can be applied to various metal parts which require high precision and corrosion resistance in addition to the metal block.

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

Claims (1)

Processing a sealing part of a predetermined shape with a stainless steel base material in which a chromium oxide layer is present;
Performing an ion nitriding process to form an ion nitriding layer; And
And forming a chromium oxide layer by electrolytically polishing the part having the ion nitriding layer formed thereon.

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