KR101204509B1 - Titanium or zirconium displacement Nitriding Heat Treatment - Google Patents

Abstract

PURPOSE: A titanium or zirconium displacement nitriding heat-treatment method is provided to manufacture a nitride product at low costs by using anatase-based titanium dioxide and zirconium dioxide finally plasticized at low temperatures. CONSTITUTION: A titanium or zirconium displacement nitriding heat-treatment method comprises the steps of: selecting a metal base material from a group comprising iron and alloys including iron, preparing a salt bath including one or more salts selected from a group comprising sodium cyanide and potassium cyanide, dispersing either titanium dioxide or zirconia in the salt bath, heating the salt bath to a temperature of 563.7-851°C, and dipping the metal base material in the salt bath for 10 minutes to 10 hours.

Description

Titanium or zirconium displacement Nitriding Heat Treatment}

This technology relates to a titanium or zirconium substituted salt bath thermal treatment method.

Attempts to use titanium in nitriding heat treatment, particularly in salt baths, have been a long time in the making.

Korean Patent Application No. 10-1984-0004403 discloses the production of a hardened string characterized in that nitriding treatment is carried out for 3 to 6 hours in a salt bath at 500 to 580 ° C. to which 0.005-0.01% by weight of an electrically refined metal titanium powder is added. Here's how.

According to the contents of this patent, this technique is desirable to form a thick nitride layer of 100 microns or more in a short time in a sintered compound salt and a third carbonic acid mixed salt in which the plated material is added with re-sintered Ti powder as a catalyst. It illustrates the obtaining of a high hardness stainless steel file.

The patent claims that titanium is catalyzed to ensure higher strength, durability, and corrosion resistance in the process of heating cyanide compounds and other salts to form molten metal and depositing ferrous alloys that require heat treatment on the molten metal. It was a technology used as.

This technology is further developed into a patent called a method for nitriding heat treatment of a metal base material in the presence of titanium patent No. 10-2003-0026285 in Korea. In this patent, the inventor uses electrolytic metal titanium as a catalyst, but does not give a clear description of the material of electrolytic metal titanium.

However, the contents disclosed in US Pat. No. 4,332,653 in the patent states that the patent requiring high temperature electrolysis in the presence of a titanium catalyst is a patent using a titanium catalyst, and the inventor's patent does not provide electrolysis during salt bath heat treatment in using such a catalyst. It quotes electrolytic metal titanium, claiming that there is a difference between the metal base and the non-existing difference.

That is, while US Patent No. 4,332,653 applies electricity of 10-100 A / dm ² in the presence of a titanium catalyst, the inventor's patent does not apply such electricity and has the advantage of performing salt bath nitriding heat treatment at a relatively low temperature. will be.

This patent appears to be based on US Pat. No. 6,645,660, which shows that the titanium used is metallic titanium formed by the electrolysis of titanium compounds and is powder in terms of dispersing. Rather than presenting a method for obtaining decomposed metal titanium, it is described by citing US Patent No. 4,332,653.

In addition, U.S. Patent No. 7,438,769, which was invented by the same inventor, also disperses metallic titanium formed by electrolysis of titanium compound, but does not explain how to obtain metallic titanium formed by electrolysis of titanium compound. not.

In addition, US Patent No. 7,732,014, which was invented by the same inventor, has a more specific aspect of the above invention, and also has a more diversified base material, nano coating, ceramic coating, physical vapor deposition (PVD), and chemical vapor deposition (CVD). And heat treatment of the surface-formed product by ion assisted coating (IAC), etc., but this patent also does not describe how metallic titanium formed by electrolysis of titanium compounds is obtained.

As well as. U.S. Patents 7,438,769 and 7,732,014 also claim the diffusion of titanium.

U.S. Patent No. 4,332,653, first cited in a patent using titanium for heat treatment, claims a high temperature electrolytic nitriding heat treatment by applying electricity in molten cyanide molten metal containing low grade zirconium or titanium oxide.

In other words, the inventors claim that the addition of electrorefined titanium metal powder or zirconium metal powder into molten cyanide molten metal turns into low grade titanium or zirconium oxide in the molten metal.

The patent is a technique invented by Shinzoh Satoh, which is 1dm ² at a temperature of 760-850 ° C. It is an electrolytic salt bath heat treatment patent applying a current of 10 to 100 A per sugar.

In this process, inventor Shinzo Sato describes a titanium compound which is a material for electrorefining used for the formation of low grade oxides of titanium or zirconium. It specifies that it can be obtained from the electrolysis of aqueous solutions of titanium dichloride or zirconium dichloride as described in the examples of US Pat. No. 3,074,860.

In addition, a low grade oxide is claimed to be an oxide in the form of TiO rather than TiO ₂ when metal titanium or zirconium obtained from the titanium dichloride or zirconium dichloride is put into molten cyanide molten metal.

In this regard, the inventors intend to explain this by the following formula.

Ti + 1 / 2O ₂ = TiO

That is, the inventors thought that when titanium titanium or zirconium dichloride is produced in a constant aqueous solution using electrolysis to produce metal titanium or metal zirconium, and the metal titanium and metal zirconium are put into molten cyanide molten metal, it becomes TiO or ZrO. It is believed that this is a low grade oxide.

This claim is similarly claimed in Korean Patent Application No. 10-1984-0004403, wherein the Ti powder added in the salt bath is an electrorefined metal powder that is present in the bath as TiO (titanium monoxide) in contact with air at the surface of the salt bath. It is claimed to promote nitriding by highly catalyzing the nitriding process.

That is, the use of titanium nitride salt heat treatment-related titanium claims to use a consistently refined titanium metal powder, the source of the prior art associated with this electro-refined titanium metal powder is consistently US Patent No. 4,332,653, The use of the electrorefined titanium metal powder in the patent indicates that it is again due to US Pat. No. 3,074,860.

However, there is no possibility that the titanium metal powder electrorefined in the salt bath will change into TiO, which is called a low grade titanium oxide.

Formula TiO. Titanium monoxide having a formula weight of 63.9 g is a yellowish black equiaxed crystal system with a melting point of 1,750 ° C and a boiling point of 3,000 ° C or higher and a specific gravity of 4.93.

Titanium (Ⅳ) oxide that is, inde black crystals generated upon heating the titanium metal to TiO ₂ and 1,550 ~ 1,750 ℃ in vacuo to obtain a composition of TiO precisely is difficult.

The reason why it is difficult to obtain TiO composition accurately is that titanium forms O ₂ film, which is the most stable film on the surface when it comes into contact with air or moisture. This is because it is difficult to accurately measure TiO ₂ and metal Ti in a vacuum and prevent the formation of some O ₂ film on the surface of the metal Ti. Titanium forms an O ₂ film on the surface in the air without any action.

Titanium monoxide (TiO) is difficult to make in this way, therefore, the heat treatment temperature of the salt bath does not reach the temperature for forming titanium monoxide, and it is unreasonable to expect the formation of TiO in contact with the surface air. There is.

That is, when titanium or zirconium metal powder is added to the salt bath, TiO or ZrO claimed in the patent as a low grade titanium zirconium oxide is physically impossible to be produced in the salt bath.

The patent also cites US Pat. No. 3,074,860 to describe the electrorefined titanium metal powder. This patent was filed by Shinzoh Satoh in 1960 and is a patent for the electrolytic process for the production of metallic titanium from aqueous solutions of titanium compounds. There is no explanation.

This inventor appears to be the same as the inventor of U.S. Patent No. 4,332,653, which claims that titanium can be plated in aqueous solution with a single metal, and commercially available formaldehyde or hydrazine solutions in aqueous solution. It is claimed to use a combination of and Pyrogallic acid.

Implementing as claimed in this patent means that titanium can be electroplated into a single metal in an aqueous solution, but it has not been realized that titanium is electroplated into a single metal in an aqueous solution.

Dissolve 35 g of Titanium dichloride in an aqueous formaldehyde solution (37%) stock solution according to the composition of Example 1, a representative example of this patent, or add Ti ions obtained from TiCl ₄ and add pyrogallic acid (CAS No. 87-66- 1) When 10g was added, the liquid became dark brown, and pyrogallic acid was decomposed. When ammonia was added to the alkaline solution, most of the organic acid was decomposed and aggregated on the surface of the solution. Nevertheless, 7A / dm ² of electricity was applied to confirm the result, but the pure titanium plating claimed by the patent holder did not occur.

In other words, titanium plating in the aqueous solution of U.S. Patent No. 3,074,860 appears to be a non-realized patent, and attempted to re-titanium by this method, but could not be reproduced.

Therefore, titanium metal powder by electrorefining in the aqueous solution of US Pat. No. 4,332,653 citing this patent cannot be present. Even if titanium is plated, it will come out as a metal mass and not as a powder.

In addition, even if titanium is precipitated, it is inevitably precipitated in the form of TiO (OH) ₂ in an alkaline solution, which is unlikely to be plated on the surface of the cathode as the inventors claim.

However, the electrolytic reduction technique of titanium metal powder is not without much.

Research Report of the Korea Atomic Energy Research Institute February 2007 Development of tantalum metal powder manufacturing technology using electrolytic reduction technology After 50 pages of {Preparation of Tantalum Metal Powder by Electrolytic Reduction Technology in High Temperature Molten Salt} It has been tested and described in detail to determine whether it is applicable to the manufacture of high value metal powders.

According to the report, the electrolytic reduction of titanium is carried out in Ca salt bath or LiCl salt bath environment and not in aqueous solution. Under aqueous environment it is because it is not possible to suppress the generation of O ₂ film on the surface of Ti.

Therefore, it can be seen that the electrolytic reduction experiment of titanium should be performed under an inert gas atmosphere and a salt bath environment.

In the report, however, there was no misunderstanding of the fact that manufactured titanium should be handled at temperatures below 200 ° C in air to prevent reoxidation. Titanium forms a stable oxide film in the atmosphere even if it is left in the air even below 200 ° C.

This is why titanium has good corrosion resistance.

Although there was a patent on titanium plating single metal in aqueous solution in 1960, the patent on electrolytic reduction of titanium metal powder is applied in 2007 under salt bath environment, not aqueous solution. You can guess.

Therefore, U.S. Patent No. 3,074,860, filed by Shinto Sato, appears to be an infeasible patent, and since it is impossible to produce an electrorefined titanium metal powder in an aqueous solution, which is the source material of U.S. Patent No. 4,332,653, which is also cited, this also is not feasible. It can be seen as a patent.

In addition, US Patents [6,645,566], [7,438,769], and [7,732,014] in which three patents were invented by other inventors, 6,645,566 cited 4,332,653, but specifically for titanium electrolysis in aqueous solution. All other patents, including the remaining two patents and Korean patents, are characterized by the use of metallic titanium formed by electrolysis of a titanium compound.

However, disagreements continue to this day with respect to the electro-refined metallic titanium powder which has been used in the above patents. That is, it is not yet known how the titanium metal powder was produced by the electrorefining method in the process of producing the titanium metal powder.

In addition, the important point of the invention is that the use of electricity during heat treatment was only a technique already described in US Patent 3,639,641. In this patent, all of the examples were heat-treated without any electricity at a temperature of 600 ° C. in the presence of titanium.

This US Pat. No. 3,639,641 contains significant material. This gives clues as to how the titanium metal powder was formed in the salt bath.

The inventor explains as follows.

[In the method of (US Pat. No. 3,074,860), activated pure titanium manufactured by electrolysis of an aqueous solution of a water soluble compound is made to be present, in which electroplated articles are dipped several times and in a considerable quantity into a salt bath of 550 ～ 600 ° C until the desired contant is obtained. In US Pat. No. 3,074,860, activated pure titanium, drawn by electrolysis of an aqueous solution of an aqueous mixture, is presented several times in a salt bath at 550-600 ° C. several times until a desired contant is obtained for the electroplated product.]

That is, the titanium metal can enter the salt bath by immersing the plated product several times in the salt bath. In addition, the product is demonstrated as follows.

[numerous iron products having pure titanium metal which has been electroplated by the water-soluble electrolytic process (U.S. patent No. 3,074,860) are charged into this and then removed. Numerous steel products with pure titanium metal electroplated by a water soluble electrolysis process (US Pat. No. 3,074,860) are introduced into and subsequently disappeared.]

In the U.S. Patent No. 3,074,860, the inventors used copper plated specimens in the cathode, but in order to allow the titanium metal powder to be present on the salt bath in the salt bath heat treatment, the encased products were not so plated. Claim that it is a steel product.

This is the only patent that describes how to add electrorefined titanium to metal salts in a salt bath.

U.S. Patents 7,438,769 and 7,732,014 also claim titanium diffusion. In other words, it claims that titanium and nitrogen dissipate and fill voids and fill the voids simultaneously.

In general, diffusion is different from diffusion between metals and diffusion of gases. The diffusion of gases such as hydrogen, oxygen, and nitrogen includes carburization and nitriding, which is called single diffusion. In addition, carbon is a nonmetallic solid and diffuses in an invasive diffusion like nitrogen.

However, a method of mutual diffusion or impurity diffusion is applied to diffusion of metals.

A diffusion method called interdiffusion or impurity diffusion refers to a phenomenon in which metal atoms are diffused into each other metal. In general, atomic diffusion between two metals is required for such diffusion to occur.

The fact that this atomic contact is necessary is very important, and in order to elicit an atomic contact, this can be solved by plating or welding (a part of the metal melts and seizures on the other side). In addition, if the temperature is high, even though the atoms do not contact, the metal invading may evaporate and be deposited to cause intrusion diffusion, but it is difficult to expect it in the present invention. This is because iron, the metal used, has a melting point of 1,538 ° C and titanium has a higher 1,675 ° C.

In addition, the inventor of the prior art is face to face with the claims of patent application No. 10-1984-0004403 filed July 21, 1984 to the Republic of Korea. In the patent, the inventors added the Ti powder in the salt bath in contact with air at the surface of the bath, and is present in the bath as TiO (titanium monoxide), which catalyzes the nitriding treatment highly and promotes nitriding. Claimed. However, if the Ti metal powder is present as TiO, oxygen is present between the metal base material and Ti and titanium diffusion cannot be made.

Salt bath heat treatment is a method of surface treatment aimed at surface modification of metals by nitriding and carburizing, which are penetration diffusion of nitrogen and carbon.

Thus, as claimed in US Pat. Nos. 7,438,769 and 7,732,014, nitrogen or carbon do not play a role in releasing and filling voids.

If we insist on diffusion using these voids, we need to be able to explain how atomic contact between metals occurs. Clear evidence should be given, for example, Calorizing (aluminum penetrating) or Shearding (zinc diffusion).

Looking at the patents related to the salt bath heat treatment method using titanium so far as shown in Table 1.

Filing year Country Registration Number Main Content problem 1960 us 3074860 Titanium wet plating Reproducibility 1965 us 3639641 Electroless Salt Bath Heat Treatment
600-750 Cited 3074860.
This electrolytically precipitated activated pure titanium gasifies readily at above 550. and is contained in the salt bath. (Claim to vaporize) 1981 us 4332653 Electrolytic Salt Bath Heat Treatment Cited 3074860.
TiO creation claim. 1984 kor 10-1984-0004403 Electroless Salt Bath Heat Treatment 4332653 citations
TiO creation claim. 2002 us 6645566 Electroless Salt Bath Heat Treatment
430-670 Cited 4332653.
Almost similar to U.S. Patent 3,639,641 2003 kor 10-1984-0026285 Electroless Salt Bath Heat Treatment
430-670 Cited 4332653.
Almost similar to US Pat. No. 3,639,641. 2006 us 7438769 Titanium Diffusion Titanium diffusion claims no theoretical background. 2006 us 7732014 Carbide Titanium Diffusion Titanium diffusion claims no theoretical background.

As such, titanium is currently being used in salt bath heat treatment, but there are problems such as insisting on the formation of TiO, which is based on physical theory, insisting extraction of metal titanium in aqueous solution, or citing non-reproducible patents. This means that the current technology is not being reproduced on the correct physical theory of heat treatment using titanium.

Due to this problem, it was not possible to know whether only titanium metal powder by electrorefining could be used for the titanium nitride heat treatment, and it was wanted to know whether a more easily and cheaper titanium material could be used. Due to this, even this is not easy to understand, and because of this has prevented the development of heat treatment technology using titanium easily and inexpensively, it has been difficult to use in a variety of industries, there has been a problem that a high price is formed.

It is an object of the present invention to solve this problem, and to provide an easy and inexpensive titanium and zirconium compound that can be used in the titanium or zirconium-nitride salt bath heat treatment method.

Another object of the present invention is to provide a titanium or zirconium-nitride type salt bath heat treatment method on a base material using the provided easy-to-use titanium compound and zirconium compound.

In the present invention, the titanium or zirconium-substituted nitriding salt bath heat treatment method and the nitride heat treatment product prepared by the method use anatase titanium dioxide or zirconium dioxide, which are easy to obtain or inexpensive.

In particular, by using anatase titanium dioxide and zirconium dioxide, which have been fired at the lowest firing temperature as low as possible, anyone can implement a titanium or zirconium-substituted nitriding salt bath heat treatment method at low cost.

This makes it possible to implement titanium nitride heat treatment products that have been expensive for a long time without using electro-refined titanium metal powder, and can be easily and inexpensively manufactured using titanium or zirconium-substituted nitride heat treatment products in various industries. It is.

In order to achieve the above object, the present invention provides a titanium compound and a zirconium compound which are easy to obtain and inexpensive to be used for titanium or zirconium-nitride salt bath heat treatment.

In addition, the present invention using the titanium compound,

(a) providing a metal base material selected from the group consisting of iron or an alloy comprising iron;

(b) providing a salt bath comprising a salt selected from the group consisting of sodium cyanide and potassium cyanide;

(c) dispersing one of the titanium compound and the zirconium compound in the salt bath;

(d) heating the salt bath to a temperature of 563.7 to 851 ° C .; And

(e) it provides a titanium or zirconium-nitride type salt bath heat treatment method comprising the step of immersing the metal base material in the salt bath for 10 minutes to 10 hours.

In another aspect, the present invention provides a product produced by the titanium or zirconium-substituted nitride salt bath heat treatment method.

Hereinafter, the present invention will be described in detail with reference to the action and preferred embodiments of the constituent means of the present invention.

The inventors invented titanium and zirconium electroless substitution plating with Korean Patent Application Nos. 10-2011-0019777 and 10-2011-0022924, and reached the present invention knowing that iron is substituted with these two metal ions. However, this patent could be referred to as pure titanium or zirconium plating in an aqueous solution in which titanium or zirconium meets iron or iron alloy material in an aqueous solution and ion exchanges with iron on the surface to cause a substitution reaction. Did not have a deep relationship.

However, it has been confirmed that the substitution relationship between iron, titanium, and zirconium occurs in all ranges of acidic, neutral, and alkaline, and the present invention has been reached. That is, in the heat treatment of the nitriding salt bath, if titanium and zirconium can exist in an ionic state even in a salt bath rather than in an aqueous solution, a substitution reaction is formed on the iron surface to form a thin plated film. Will be explained.

Pure metal titanium prevents corrosion by forming a stable oxide film at room temperature, but it is very reactive at high temperatures of 600 or higher, so it is 'contaminated' with elements such as O ₂ , N ₂ , H _2, and so on, reducing corrosion resistance and losing all mechanical properties.

At this time, when elements such as O ₂ , N ₂ , H _2, etc., in which titanium, which is a metal, meet, meet inside the hot container, the O ₂ film, which is a passivation film on the titanium surface, is removed and the film is suppressed to reduce corrosion resistance of the metal itself. Eroded. Erosion means that titanium is ionized. In this case N ₂ will do its job.

The same phenomenon occurs even when the element meets in the form of a gas in this container or as an additive in an aqueous solution, and thus, carbon and nitrogen compounds such as NaCN and KCN are contained even in a salt bath. Since Na) is dissolved, anatase TiO ₂ loses the O ₂ film more easily than the aqueous solution and exists in an ionic state.

However, if the O ₂ film is lost only with nitrogen ions, it is not possible to remove the passivation film of anatase titanium dioxide from the salt bath with nitrogen ions, as the phenomena of the phenomena remain consistent even if the film is removed by nitric acid in aqueous solution. This prevents the film from regenerating.

The removal of the passivation film actually generated can be performed by adding chlorine compounds containing chlorine ions and sulfate compounds containing sulfate ions used in the smelting of titanium dioxide or titanium metal. Sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate, calcium sulfate and the like can be used for such compounds.

However, sodium sulfate, potassium sulfate, and calcium sulfate have a melting point of 884 ° C, 1069 ° C, 1450 ° C, etc., and are inconvenient to use as compounds that are relatively higher than sodium chloride (800.4 ° C), potassium chloride (770 ° C), and calcium chloride (772 ° C). However, it can be used as an additive.

In addition to the addition of acidic acid to further utilize the carbon may include sodium carbonate (melting point 851 ℃). This is because pure cyan salt bath is a weak alkali.

Anatase titanium dioxide is the smallest and simplest form of O ₂ film on the surface in Ti ion state. Electrorefined metallic titanium powder, however small, cannot be smaller than TiO ₂ with the O ₂ film removed, so it can be ionized more easily than using conventional titanium metal powder, so using titanium or zirconium It may be more suitable for the salt bath heat treatment.

Therefore, it is more preferable to use anatase titanium dioxide and zirconium dioxide in the present invention than to use the prior art electrorefined titanium metal powder.

In addition, anatase dioxide produced by firing at a temperature lower than the heat treatment temperature used in a salt bath, rather than using titanium electrolytically formed metal titanium (TiO (OH) ₂ ) or zirconium hydroxide (Zr (OH) ₄ ). More preferably, titanium or zirconium dioxide powder is used.

Titanium hydroxide or zirconium hydroxide may be used directly, but water may form in the salt bath in the process and may act as an impurity.

However, in the case of titanium dioxide, there are three types of oxides such as anatase, brookite, and rutile, which can be selectively made by changing the manufacturing method such as firing temperature in the manufacturing process, and the effect of firing temperature on the oxide is very large. . Among them, anatase titanium dioxide, which is the softest form of surface texture, is suitable, and it is suitable to be fired at low temperature where it is not much resistant to heat.

In addition, in the case of zirconium, unlike titanium, the passivation film does not occur at room temperature, but it is appropriate to use an oxide that does not add much temperature as much as possible as the metal forming the O ₂ film only after 800 ° C.

The anatase titanium dioxide or zirconium dioxide fired at such a low temperature is the passivation film of titanium eroded by removing the O ₂ film by the chlorine compound contained in the salt bath when the N component of the NaCN forming the salt bath rises to a temperature close to 600 ° C. When the product of iron or iron alloy is put into the salt bath, it causes substitution plating reaction on the surface to form a thin Ti or Zr metal film. The atomic contact causes Ti or Zr to Atomic contact with the material meets the basic conditions that can lead to the diffusion of interdiffusion methods.

However, if titanium and zirconium compounds are added at the same time, the titanium film is formed according to the ionization tendency, so there is no need to mix the two compounds.

At this time, it is preferable to use the anatase titanium dioxide fired at 600 degrees C or less as possible, More preferably, it bakes at the temperature below 563.7 degreeC which is the melting point of NaCN which is a main component of a salt bath. In fact, the firing temperature at which TiO (OH) ₂ is divided into TiO ₂ and H ₂ O is sufficient at 500 ° C.

In the present invention, this substitution relationship allows explanation of many parts that have not been explained in the salt bath heat treatment using titanium. That is, titanium or zirconium causes atomic contact through substitution plating reaction on the surface of iron or iron alloy in addition to nitrogen and carbon invasive diffusion, and the plating layer thus formed solves the atomic contact problem for mutual diffusion. The principle of forming the diffusion layer in the above is explained. The description of this principle overcomes the conventional technical limitation of using electropolished or electrorefined titanium metal powder.

In addition, the heat treatment temperature is not only good at low temperatures. Considering the melting point of added salts such as NaCN, KCN, NaCl, and Na ₂ CO ₃ used in the composition of the salt bath, a temperature range of 563.7 ° C to 851 ° C, which is a temperature within the melting and boiling points of NaCN, is used. This is because it is preferable. In other words, the salt must be used above the melting point so that the added salt is sufficiently dissolved and flows well.

In addition, since interdiffusion between dissimilar metals is advantageous for diffusion at higher temperatures, it may not be argued that salt bath heat treatment is performed at low temperatures as in the conventional patents.

Therefore, it is preferable to perform a salt bath heat treatment at a temperature of 563.7 ° C. or higher, which is the melting point of NaCN, and a salt bath heat treatment at a temperature of at least 600 ° C. because anatase titanium dioxide or zirconium dioxide loses O ₂ film and is suitable for ionization. It is more preferable to carry out.

Therefore, the titanium layer is plated by substitution reaction on the surface of the base material layer separately from the conventional carburization and nitriding of nitrogen or carbon, thereby causing mutual contact and mutual diffusion, and simultaneous intrusion-type nitriding heat treatment of nitrogen and carbon. You can explain all of them.

Hereinafter, the present invention will be described through preferred embodiments.

Example 1 Preparation of Low Temperature Calcined Anatase Titanium Dioxide.

Most commercially available anatase titanium dioxide products do not have precise control of the firing temperature for mass production. Thus, anatase titanium dioxide was prepared by the following method.

(1) 200 g of anatase titanium dioxide was dispersed in 1 liter of sulfuric acid, dissolved by heating, and stabilized by addition of 10 ml of nitric acid, followed by cooling.

(2) 1 liter of water was added to the stable solution to suppress exothermic reaction, and cooled again.

(3) 12.5% NaOH solution was slowly added while changing the temperature of the solution to adjust the pH to 8-9 to induce titanium hydroxide precipitation.

(4) The precipitated titanium hydroxide was collected, washed twice, and calcined at 500 ° C. or lower to prepare low temperature calcined anatase titanium dioxide.

Example 2 Preparation of Low Temperature Calcined Zirconium Dioxide.

Commercially available zirconium dioxide is more difficult to separate than titanium dioxide. In particular, as much as titanium is not studied, some oxides do not dissolve in sulfuric acid at all, and some oxides are easily dissolved. For clear experimental results, zirconium dioxide was prepared as follows.

(1) 200 g of zirconium sulfate was dissolved in 1 liter of water.

(2) 25% NaOH solution was slowly added while changing the temperature of the solution to adjust the pH to 8-9 to induce zirconium hydroxide precipitation.

(4) The precipitated zirconium hydroxide was collected, washed twice, and calcined at 500 ° C. or less to prepare zirconium dioxide.

Example 3 Titanium Substituted Nitride Salt Bath Heat Treatment Test.

Take 80 to 90% by weight from sodium cyanide or potassium cyanide group, add 8% to 19% by weight of sodium chloride or sodium carbonate to form a salt bath, wherein 1% by weight of anatase titanium dioxide prepared in Example 1 above To 2% by weight was added, and the salt bath was slowly heated to 600 ° C.

(Practical composition: NaCN 500g, KCN 300g, NaCl 100g, Na ₂ CO ₃ 80g, TiO ₂ 20g)

The amount of anatase titanium dioxide is not merely a catalyst but is consumed by substitution plating, so if it is insufficient, it must be supplemented additionally.

A 10 cm long 20 cm specimen was deposited in the salt made of carbon steel, which is an iron alloy, and subjected to titanium substitution type nitriding heat treatment for 2 hours. The Vickers hardness of the surface was 1,200 HV, and the surface was determined to have a titanium layer firmly formed.

The material that can be used for the titanium zirconium-substituted nitriding heat treatment of the present invention is applicable to various iron and iron alloys such as carbon steel of iron and carbon, stainless steel of iron and nickel chromium alloys, iron and chromium alloys, and high speed steel and tool steel.

Example 4 Zirconium Substituted Salt Bath Heat Treatment Test.

Take 80 to 90% by weight from sodium cyanide or potassium cyanide group, and choose from sodium chloride or sodium carbonate to put a salt bath by adding 8% to 19% by weight, and from 1% by weight of zirconium dioxide prepared in Example 2 2 weight% was added and it heated gradually so that the salt bath might be 600 degreeC.

(Practical composition: NaCN 800g, KCl 100g, Na ₂ CO ₃ 80g, ZrO ₂ 20g)

Zirconium dioxide, like titanium, is not simply a catalyst but is consumed by substitution plating, so it must be supplemented later if it is insufficient.

A 10 cm long 20 cm specimen was deposited in the salt made of carbon steel, an iron alloy, and zirconium-substituted nitriding heat treatment was performed for 2 hours. The Vickers hardness of the surface was 1,100 HV, and it was determined that a zirconium layer was firmly formed on the surface.

Example 5 Photocatalytic Test of Titanium Substituted Nitride Heat Treated Products.

In order to confirm the formation of the titanium layer of the sample of Example 3, a methylene blue 20PPM indicator reaction test was performed.

The methylene blue solution was placed in a glass test vessel and irradiated with ultraviolet light with a black light fluorescent lamp of PHLIPS TUV 8W to examine the discoloration reaction of the methylene blue indicator, and water and dye were separated from the liquid phase. .

Claims (8)

As a method of nitriding heat treatment of a metal base material at the same time as the substitution plating,
(a) providing a metal base material selected from the group consisting of iron or an alloy comprising iron;
(b) providing a salt bath comprising at least one salt selected from the group of sodium cyanide or potassium cyanide;
(c) dispersing either titanium dioxide or zirconium dioxide in the salt bath;
(d) heating the salt bath to a temperature of 563.7 to 851 ° C .; And
(e) titanium or zirconium-nitride salt bath heat treatment method comprising the step of immersing the metal base material in the salt bath for 10 minutes to 10 hours.
The method of claim 1, wherein the dispersion in step (c) further comprises at least one salt selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate, calcium sulfate, sodium carbonate,
Sodium chloride, potassium chloride, calcium chloride, sodium sulfate, potassium sulfate Titanium or zirconium-substituted nitride salt bath heat treatment method characterized by further comprising 8 to 19% by weight of at least one salt selected from the group consisting of calcium sulfate, sodium carbonate.
The method of claim 2,
The anatase titanium dioxide or zirconium dioxide is titanium or zirconium-substituted nitride salt bath heat treatment method characterized in that it is continuously added as much as the amount consumed.
The method of claim 1,
Titanium or zirconium-substituted nitrile salt bath heat treatment method characterized in that the titanium dioxide of step (c) is anatase titanium dioxide.
The method of claim 1,
Titanium or zirconium substituted nitrile salt bath heat treatment method characterized in that the titanium dioxide or zirconium dioxide of step (c) is calcined at a temperature of 500 to 600 ℃.
The method of claim 1,
Titanium or zirconium-substituted salt bath heat treatment method characterized in that the titanium dioxide or zirconium dioxide of step (c) is calcined at a temperature of 500 ℃ or less.
The method of claim 1,
The immersion temperature of step (e) is 563.7 to 851 ° C titanium or zirconium nitride salt bath heat treatment method.
The method of claim 1,
The immersion temperature of step (e) is a titanium or zirconium nitride salt bath heat treatment method, characterized in that 600 to 851 ℃.