KR20190055659A - Surface coating method of the metal seat ball valve using pack cementation and the metal seat ball valve having the coating layer using the same - Google Patents

Abstract

The present invention relates to a surface coating method of a metal seat ball valve for a slurry line which has high corrosion resistance, high hardness, wear resistance and excellent resistance to abrasion by forming a chromium coating film by performing a pack cementation process on a surface of a material using a pack mixture having a predetermined content ratio. To this end, the present invention provides the surface coating method of a metal seat ball valve, comprising: a step of preparing a pack mixture; a step of inputting an iron-based metal and a pack mixture powder in a pack; a step in which the pack inputted with the iron-based metal and the pack mixture powder is immersed in a vacuum chamber; a step of operating the vacuum chamber; a step of raising the temperature inside the vacuum chamber to a process temperature; and, a step of heating at the raised process temperature for a predetermined time and forming a coating layer, wherein the pack mixture powder includes chromium, an activator, and an inactivator.

Description

TECHNICAL FIELD [0001] The present invention relates to a surface coating method of a metal sheet ball valve using packing and a metal sheet ball valve having a coating film formed by the same method the same}

The present invention relates to a surface coating method of a metal sheet ball valve using pack cementation, and more particularly, to a surface coating method of a metal sheet ball valve for a slurry line using packing. More specifically, a packed mixture having a predetermined content ratio is used to perform a packing process on a surface of a material to form a chromium-coated film, whereby a slurry line having excellent resistance to high corrosion resistance, high hardness, To a surface coating method of a metal sheet ball valve.

Ball valves are widely and frequently applied to industrial installations.

The ball valves used in petrochemical plants, fluid supply systems of nuclear power plants and thermal power plants, and various drive control devices are mostly made of copper, brass and stainless steel.

The petrochemical plant market is steadily growing. Therefore, the importance of pipeline operation reliability in the petrochemical plant process is continuously increasing. The problem of the ball valve, which is one of the main components of pipelines, It also leads to a lot of economic losses.

Therefore, it is recognized that it is a very important problem to secure a stable life along with the rapid replacement of parts such as ball valves. Parts used in petrochemical plant equipment are used in high temperature, high pressure and high oxidizing atmosphere and require excellent mechanical properties Most depend on imports.

In particular, the ball valve used in the slurry line is made of a lime compound used as a neutralizing agent to remove sulfur (S) component of the boiler exhaust gas and forms a high-hardness slurry formed by coalescence with the minerals contained in coal ash Chemical reactions and surface wear are both extreme and lead to losses.

In the case of the metal seat ball valve, steam and scratch are generated in the seat and ball of the valve, and the steam is frequently leaked.

In case of these parts, it is difficult for domestic procurement to make a purchase request to an overseas production company. Since it is necessary to always have a spare part in preparation for emergency maintenance, an excessive maintenance fee is incurred, There is a problem, and a technology for improving corrosion and abrasion resistance as well as domestic design / manufacture technology must be developed at the same time.

In order to solve these problems, a coating method using CVD has been carried out. However, this method is not only a very expensive method but also has a disadvantage that it can be applied to only a limited part requiring high temperature resistance.

Korean Patent Registration No. 10-1558308

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art as described above, and it is an object of the technical composition of the present invention to provide a high- And a method of coating a surface of a metal sheet ball valve with improved resistance to abrasion.

To this end, the present invention provides a method for preparing a packed product, Charging an iron base material and a pack mixture powder into a pack; A step in which the pack into which the iron base material and the pack mixture powder are injected is infiltrated into the vacuum chamber; Operating a vacuum chamber; Heating the inside of the vacuum chamber to a process temperature; And heating the mixture at an elevated temperature for a predetermined period of time to form a coating layer, wherein the pack mixture powder comprises chromium, an activator and an inactivating agent.

Further, the iron base material may be a stainless steel material.

The chrome (Cr) content is 16.0 to 18.0 wt%, the nickel (Ni) content is 10.0 to 14.0 wt%, and the molybdenum (Mo) content is 0.02 wt% or less. 2.0 to 3.0% by weight.

In addition, the pack mixture powder may contain 5 to 15% by weight of the chromium powder, 0.05 to 5% by weight of the activator, and 80 to 90% by weight of the deactivator.

The process temperature may be in the range of 1055 ° C to 1060 ° C.

The predetermined time may be 9 hours to 11 hours, preferably 10 hours.

In addition, the pack mixture powder may contain chromium powder and deactivator in a weight ratio of 1: 8 to 1:15.

In addition, the step of operating the vacuum chamber may include evacuating the interior of the vacuum chamber to a vacuum degree of 0.5 to 1.5 mTorr; And purging the interior of the vacuum chamber with an inert gas supplied thereto.

In addition, the inert gas may be argon (Ar) gas or helium (He) gas.

Also, the metal sheet ball valve may be a metal sheet ball valve for slurry.

As described above, according to the present invention, a chromium coating is formed on the surface of a material by packing using a pack mixture containing a constant composition by a thermochemical method, so that not only the adhesion is excellent, but also the hardness, , The corrosion resistance, and the like can be manufactured.

In addition, in the case of stainless steel parts, the surface layer having hardness of 1,200 Hv or more on the surface can be uniformly applied throughout the product, thereby increasing the service life and reliability of the product.

In addition, in the case of the surface treatment for forming chromium carbide (C-Cr) through the pack chroming process, reproducibility and easy process control become possible, and a product of excellent quality with a small scattering degree can be stably supplied.

Further, the manufacturing method according to the present invention is not affected by the shape of the product, and can be applied to all parts of the power generation part because the surface treatment can be performed on all the iron-based materials.

1 is a view showing a process of a surface coating method of a metal sheet ball valve using packing according to the present invention.
FIG. 2 is a view showing a state where a ball valve and a valve seat are charged into a vacuum chamber in a coating step according to the present invention. FIG.
3 is a cross-sectional view of a chromium compound layer formed on the surface of a ball valve according to the present invention.
FIG. 4 is a graph showing the hardness of the ball valve according to the present invention measured by the depth of the coating layer.
FIG. 5 is a graph showing a result of measurement of a friction coefficient of a ball valve manufactured according to the present invention.
6 is a graph showing the results of a salt water spray test of a ball valve manufactured according to the present invention.
7 is a view showing the results of an acid resistance test of a ball valve manufactured according to the present invention.
8 is a graph showing the results of the alkali resistance test on the ball valve manufactured according to the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

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

1 is a view showing a surface coating method of a metal sheet ball valve according to the present invention, specifically, a surface coating process through packing.

Referring to FIG. 1, the surface coating method of a metal sheet ball valve according to the present invention includes a step (step 1) of preparing a pack mixture, a step (step 2) of charging an iron- A step of infiltrating the pack into which the base material and the pack mixture powder are injected into the vacuum chamber (third step), a step of operating the vacuum chamber (fourth step), a step of raising the temperature inside the vacuum chamber to the process temperature And forming a chromium compound coating layer by heating at a process temperature raised in the fifth step for a predetermined period of time.

According to the above-described manufacturing method, the surface of the ball valve is subjected to a pack chromizing process, which is a type of pack cementation, to form a chromium compound coating layer having high hardness, abrasion resistance and high corrosion resistance.

Packing is a simple and economical coating technology that applies mechanical properties such as oxidation resistance to an iron base material by coating an iron base material. Further, the packing is advantageous in that a uniform coating film can be formed over the entire surface of a three-dimensional iron base material as compared with other general coating techniques.

Generally, a step of charging an iron base material, a reaction metal (Cr, Al, Si, etc.), an activator and an inert material into a pack, and a step of forming a coating film on the base material by heating the pack . The activator reacts with the reactive metal to help form a coating film. The deactivator functions to prevent the sintering of the cast iron base material from being coated.

The packing can be divided into Chromizing, Aluminizing and Siliconizing depending on the type of the reaction metal, and the present invention relates to chromiuming.

The method of manufacturing a metal-sheet ball valve according to the present invention is characterized by forming a chromium-coated film on an iron-based base material by using packing (chromating). Hereinafter, a method of manufacturing a coating film will be described step by step.

The first step is preparing the pack mixture powder. At this time, the pack mixture powder contains chromium (Cr), an activator and an inactivating agent.

The chromium powder may be contained in an amount of 5 to 15% by weight, and preferably 5 to 10% by weight. If the amount is less than 5% by weight, the coating film is too thin or the hardness of the coating film is difficult to achieve as desired. On the other hand, if the content exceeds 15% by weight, chromium powder is aggregated with the inert powder, There is a possibility that the porous structure will be added and the coating layer will become unnecessarily thick, which may result in poor economical efficiency.

The activator reacts with chromium to form a coating film, and plays a role in contributing to the formation of a coating film. The activator may be a known halide salt, and is not limited to any particular substance. The active agent may be included in an amount of 0.05 to 5% by weight. If it is less than 0.05 wt% or more than 5 wt%, it may be difficult to form a coating layer having a desired mechanical property because a non-uniform coating film is formed or unevenness occurs in the coating layer.

The deactivator prevents the sintering of the iron base material in the process of forming the coating film. As the inert gas, a known inert gas may be used and is not limited to any particular substance. The deactivator may be contained in an amount of 80 to 90% by weight, and preferably 85 to 90% by weight. If it is less than 80% by weight, penetration and diffusion of metal components to be formed into a coating film may not be achieved as desired, and if it exceeds 90% by weight, formation of a coating film may be delayed.

On the other hand, the pack mixture contains the chromium powder and the deactivator in a weight ratio of 1: 8 to 1:15, preferably 1: 8.5 to 1:10, more preferably 1: 8.5 to 1: 9.5 . At this time, if the mixing ratio of the chromium powder and the deactivator is out of the range of 1: 8 to 1:15, there is a fear that the coating layer is defective, decarburization occurs, or the surface of the coating layer is uneven.

The second step is the step of charging the iron base material and the pack mixture powder into the pack. The iron-based base material may be, but is not limited to, an alloy including iron, solid solution, or steel. According to the second step, the iron base material is completely embedded in the pack mixture powder in the pack. In the present invention, stainless steel SUS316 is used as the iron base material, and SUS316 contains 0.08 wt% or less of carbon (C). SUS316 may contain 16.0 to 18.0 wt% of chromium (Cr), 10.0 to 14.0 wt% of nickel (Ni), and 2.00 to 3.00 wt% of molybdenum (Mo) in addition to carbon (C).

The third step is a step in which the pack containing the iron base material and the pack mixture powder is charged into the vacuum chamber.

The fourth step is to operate the vacuum chamber. By setting the degree of vacuum inside the vacuum chamber by operating the vacuum chamber, moisture, oxygen, and other impurities, which are substances that hinder the reaction contained in the vacuum chamber, can be discharged out of the vacuum chamber. At this time, the degree of vacuum may be 0.5 to 1.5 mTorr. If the vacuum degree exceeds 1.5 mTorr, an unnecessary reaction, for example, an oxidation reaction of the iron base material, may occur due to moisture, oxygen, etc. remaining in the vacuum chamber during the coating film formation process. In addition, the reaction rate of reactions occurring during the coating film formation process may also be lowered. However, even if the degree of vacuum is set to less than 0.5 mTorr, the mechanical characteristics of the coating film are not significantly different from those when the degree of vacuum is 0.5 mTorr or more.

An inert gas may be supplied into the vacuum chamber. The inert gas may be, but is not limited to, argon (Ar) gas or helium (He) gas. After the inside of the vacuum chamber is evacuated to a predetermined degree of vacuum, an inert gas may be supplied into the vacuum chamber. The inert gas is discharged into the vacuum chamber while discharging moisture and air remaining in the vacuum chamber while being filled in the vacuum chamber. This is referred to as purging. The inert gas is supplied to the inside of the vacuum chamber several times at a high flow rate, thereby effectively performing purging.

The fifth step is a step of raising the temperature inside the vacuum chamber. Such a temperature elevation step may be performed after the aforementioned vacuuming and inert gas supply. At this time, the partial pressure of the inert gas may be kept constant to prevent damage such as shrinkage of the vacuum chamber during the heating process.

The temperature elevating temperature may be between 1055 ° C and 1060 ° C, which is the process temperature. The temperature at which the temperature is raised, that is, the process temperature, is determined depending on the iron base material. According to the present invention, stainless steel, more specifically, SUS316 is used as the iron base material. On the other hand, if it exceeds 1060 ° C, there is a risk of deformation of the iron base metal.

In the sixth step, the chromium compound coating layer is formed by heating at the set process temperature for a predetermined time. In this case, the predetermined time is preferably 9 to 11 hours, more preferably 10 hours. The predetermined time may be determined according to the thickness of the chromium compound coating layer. If the time is less than 9 hours, it is difficult to form a coating layer having an appropriate thickness. If the time exceeds 11 hours, the coating layer becomes too thick.

While the process temperature is maintained, the metal components constituting the coating film among the components constituting the pack mixture powder may be reacted with the activator to become metal halide gases. Next, metal halide gases can be adsorbed on the surface of the iron base metal. Next, as the metal components of the metal halide gases adsorbed on the surface of the iron base metal become solid phase, the metal components can penetrate and diffuse into the inside of the iron base metal. As the penetration and diffusion of the metal components are performed, a coating film is formed. At this time, a coating film containing chromium as a main component is formed on the coating film, and a coating film of iron and chromium can be formed when the coating film further contains iron.

The manufacturing process of the coating film using the packing (chroming) has been described above, and the parts not described above can be understood through the known packing technique.

[Example]

SUS316 was prepared as an iron base material and a pack mixture powder was prepared so as to satisfy 5 to 15% by weight of chromium powder, 0.05 to 5% by weight of ammonium chloride as an activator, and 80 to 90% by weight of alumina as an inerting agent. 2, the vacuum chamber was purged with argon gas as an inert gas, and the temperature was raised to 1055 to 1060 占 폚 and heated for 10 hours to form a chromium compound coating layer . As a result, a chromium compound coating layer having a thickness of 22 mu m was formed as shown in Fig.

Material C Cr Ni Mo SUS316 ≤0.08 16.0 to 18.0 10.0 to 14.0 2.00 to 3.00

Chemical composition of SUS316 material

[Evaluation of mechanical properties]

As shown in FIG. 4, the chromium compound coating layer had a hardness of 1,200 Hv, and a hardened layer having a thickness of 25 μm was formed.

In addition, as shown in FIG. 5, the chromium compound coating layer exhibits a low friction characteristic with a frictional coefficient of 0.3 to 0.4 in all processes as a result of measuring the friction coefficient. This shows that the lubricity is excellent.

[Salt spray test]

The salt water spray test was carried out according to the method described in KS D 9502. As shown in FIG. 6, the test conditions were a temperature of 35 ° C and a salt concentration of 5% for 100 hours at 500 hours, It was confirmed that no corrosion occurred on the surface of the substrate.

[Acid resistance test]

In the acid resistance test, as shown in FIG. 7, the test piece was immersed in a 5% sulfuric acid aqueous solution, and the surface was wiped after 100 hours passed. After 24 hours, the discoloration of the surface state and other abnormalities were visually observed. It was confirmed that there was no discoloration or abnormality on the surface.

[Alkali resistance test]

In the alkali resistance test, as shown in FIG. 8, the test piece was immersed in a 5% aqueous solution of sodium hydroxide. After 100 hours had elapsed, the surface of the test piece was wiped off and after 24 hours, the discoloration of the surface state and other abnormalities were visually observed. It was confirmed that there was no discoloration or abnormality on the surface of the test piece.

That is, as in the above test results, the ball valve manufactured by the method of manufacturing a metal-sheet ball valve of the present invention improves the surface hardness through the corrosion-resistant and anti-wear coating treatment, It is possible to prevent damage due to friction and improve corrosion resistance and acid resistance, thereby imparting an anti-corrosive property by the sulfur (S) component, thereby having excellent performance and a long service life.

The technical idea of the surface coating method of the metal sheet ball valve using the packing according to the present invention is that the same result can be repeatedly practiced. Particularly, by implementing the present invention as described above, It is worth protecting.

Claims (12)

A surface coating method of a metal sheet ball valve using packing,
Preparing a pack mixture (first step);
(Step 2) of charging the iron base material and the pack mixture powder into the pack;
A step in which the pack into which the iron base material and the pack mixture powder are injected is infiltrated into the vacuum chamber (third step);
Operating the vacuum chamber (fourth step);
Heating the inside of the vacuum chamber to the process temperature (fifth step); And
Forming a coating layer by heating at a process temperature elevated in the fifth step for a predetermined time,
Wherein the packed mixture powder comprises chromium, an activator and an inactivating agent. ≪ RTI ID = 0.0 > 11. < / RTI > The method according to claim 1,
Wherein the iron base material is stainless steel. ≪ RTI ID = 0.0 > 11. < / RTI > 3. The method of claim 2,
The iron base material is SUS316,
, Carbon (C) contains 0.08 or less by weight, chromium (Cr) is 16.0 to 18.0 wt%, nickel (Ni) is 10.0 to 14.0 wt%, and molybdenum (Mo) is 2.0 to 3.0 wt% A surface coating method of a metal sheet ball valve using pack cationization. The method according to claim 1,
Wherein the packed mixture powder comprises 5 to 15% by weight of chromium powder, 0.05 to 5% by weight of an activator, and 80 to 90% by weight of an inert material. The method according to claim 1,
Wherein the process temperature is between 1055 ° C and 1060 ° C. The method according to claim 1,
Wherein the preset time is from 9 hours to 11 hours. The method according to claim 6,
Wherein the predetermined time is 10 hours. ≪ RTI ID = 0.0 > 11. < / RTI > 5. The method of claim 4,
Wherein the pack mixture powder comprises chromium powder and deactivator in a weight ratio of 1: 8 to 1:15. The method according to claim 1,
The step of operating the vacuum chamber (fourth step)
Evacuating the interior of the vacuum chamber to a vacuum degree of 0.5 to 1.5 mTorr; And
Wherein the inert gas is supplied to the inside of the vacuum chamber to purge the metal sheet. 10. The method of claim 9,
Wherein the inert gas is argon (Ar) gas or helium (He) gas. 11. The method according to any one of claims 1 to 10,
Wherein the metal sheet ball valve is a metal sheet ball valve for slurry. A metal sheet ball valve having a coating film formed by the method of any one of claims 1 to 10.

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