JPS59153801A - Calcium base metal and its production - Google Patents

Abstract

PURPOSE:To obtain a Ca base metal having excellent weatherability by subjecting Ca powdery and granular particles to a heating treatment in an atmosphere contg. gaseous fluorine and forming a protective layer consisting of CaF2 on the particle surface. CONSTITUTION:Ca powdery and granular particles are subjected to a heating treatment in a temp. range of 100-500 deg.C in an atmosphere consisting of 5- 100% gaseous fluorine and 95-0% inert gas. The conditions and type of reaction are selected in this stage to form uniformly the dense layer of CaF2 on the particle surface of the Ca powder and granules. The thickness of the layer is satisfactory at about 1-20mum and the Ca base metal that provides a substantial protective function at 2-5% fluorination is obtd. with Ca particles having about several mm. diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcium metal, which is known for its weather resistance in the air, and a method for producing the same.

Although metallic calcium is an abundant resource and has useful properties, it is difficult to handle.

The main reason for this is that metallic calcium has high activity and is extremely easily oxidized in the air. This tendency is more pronounced in powder particles with a large surface area, which may lead to safety problems, and needless to say, packaging, transportation, and storage costs increase. These points are restrictions on its use, and the reality is that it cannot be used very often, even though it has great utility value.

The main uses of calcium include as a reducing smelting agent for refractory metal compounds such as U%Th and REM, as a refining agent for molten metals such as steel and aluminum, as lead-calcium alloys for maintenance-free batteries, and as pharmaceuticals. be.

Calcium addition to molten steel reduces ultra-low sulfidation and removes harmful non-metallic inclusions from MnS, Al1203 to Cab, 12ca.
O*7Aff120. In recent years, this method has been actively used to produce high-grade steel as a means of so-called shape control.

When adding calcium to molten steel, in order to suppress calcium activity, calcium alloys such as Ca-8i and Ca-41 are used, or metallic calcium is coated with iron or aluminum and processed into clad wire. They use complicated methods such as swiping.

For this reason, the applicable steel types are limited, the use of grain sizes with high reaction efficiency is restricted, and the actual situation is that the use of steel in applications where fine grains are required, such as injection refining, is abandoned. .

The present invention has been made to solve these problems. The feature of the present invention is that -1> Gold suppresses the activity of calcium powder without inhibiting the reactivity during use, making it easy to handle.

The calcium metal according to the present invention is a calcium powder whose particle surface is covered with a protective layer consisting essentially of calcium fluoride.

In addition, in the method for producing a calcium metal according to the present invention, calcium powder particles are heated to a temperature of 100 to 500 h in an atmosphere consisting of 5 to 100 h of fluorine gas and 95 to 0 h of inert gas.
C. to form a protective layer substantially consisting of calcium fluoride on the surface of the particles.

Calcium in the present invention is not a commercially available pure metal calcium scale, but may be an alloy containing calcium such as a calcium-aluminum alloy or a calcium-magnesium alloy. Although there is no particular restriction on the calcium content in the alloy, the effect of the protective layer is exhibited when the alloy has a Ca2O concentration or higher, which exhibits strong oxidizing properties.

There is no particular restriction on the particle size of calcium, and it can be used from granules on the order of m to granules on the order of μm, but especially particles with a particle size of about 5% or less exhibit remarkable weather resistance effects.

The surface of the calcium metal particles of the present invention is substantially covered with a calcium fluoride layer. Since calcium fluoride is extremely stable, the protective layer should have a thickness of at least 1 μm or more to provide weather resistance.

Even if the protective layer contains a calcium alloy element such as M%Mg%Mn, the effect will not deteriorate.

Calcium metal powder having a protective layer made of calcium fluoride has the advantage of being extremely easy to handle because it has weather resistance in the air without impeding the properties of calcium. has.

Calcium fluoride, which coexists with calcium, is UF6 and T.
Calcium fluoride is not a harmful component even in reduction smelting such as h02, and when used as a refining agent for molten metals such as iron and steel, calcium fluoride is a preferable component because it acts as an effective component in promoting the refining reaction. It is.

Particularly when calcium is added to molten metal, the calcium-based metal powder having such a calcium fluoride protective layer exhibits a remarkable improvement effect.

In other words, injection refining, which conventionally could only be carried out using powder alloyed with calcium, is now possible with just calcium.On the other hand, in the production of clad wire, granular calcium metal can be directly clad with iron or aluminum tape. It becomes possible to put it into practical use with a simple method.

Next, the manufacturing method will be explained.

Generally speaking, coating by spraying or the like is an easy method for protecting active particles, but calcium cannot be used because it reacts with the binder. Maft
, binderless coatings have a fragile film and have very little protective effect.

As a means to solve the above problems all at once, we have come up with a method in which Ca and F2 are reacted by fluorine gas treatment to form a protective layer made of calcium fluoride. According to the method of the present invention, the CaF2 layer can be formed extremely easily, and the formed calcium fluoride layer is extremely stable and has the effect of protecting the calcium inside from oxidation in the atmosphere. It turned out to be excellent.

The raw material calcium used in the present invention may be metallic calcium or a calcium alloy. There is no particular restriction on the shape, and it may be rod-like, lump-like, granular, powder-like, etc., and can be used regardless of size.

Oxygen and nitrogen are gases that form the protective layer.

Carbon dioxide is a possible choice, but it is not a good choice as it inhibits the reaction of calcium.

These problems do not occur if fluorine gas is used. Fluorine gas is commercially available pure fluorine gas (purity: 99).
may be any unpurified fluorine gas (containing about 10% hydrogen fluoride) generated by electrolysis of anhydrous hydrofluoric acid.

Furthermore, these fluorine gases may be diluted with an inert gas such as helium or argon, or a gas that does not react with calcium or fluorine at a temperature of 500°C. In order to carry out the fluorination treatment within an industrially meaningful time, if the reaction gas contains at least vol% or more fluorine, calcium fluoride must be formed by selecting the reaction temperature and reaction time. is possible.

When nitrogen is used as a diluent gas, depending on the conditions, the desired calcium fluoride layer may not be formed, but calcium and nitrogen may react to form calcium nitride, resulting in a porous and unstable film layer, which improves weather resistance. may not occur.

The reaction temperature is in the range of 100 to 500°C, preferably 200°C.
~400°C is suitable. If the reaction temperature is low, it takes time to generate calcium fluoride, and the resulting calcium fluoride layer has poor uniformity and density. If the reaction temperature exceeds 500'C, the fluorination reaction will proceed rapidly and the formed calcium fluoride layer will not be dense, so the weather resistance effect will be reduced.

The reaction time may generally be several minutes to one hour. The reaction time is related to the reaction temperature and fluorine gas concentration and may be selected so as to provide the desired amount of calcium fluoride produced.

The reaction pressure can be normal pressure, reduced pressure, or increased pressure, but normal pressure systems are easier to operate.

The reaction format may be either continuous or batch. The reaction conditions and reaction format are selected so as to uniformize the gas-solid contact between the fluorine gas and the calcium powder to uniformly form a dense calcium fluoride layer over the entire surface of the calcium powder. In order to effectively utilize expensive fluorine gas, it is preferable to select an apparatus that circulates the reaction gas.

The thickness of the calcium fluoride layer should be 1 to 20 μm as long as the calcium fluoride layer is dense and uniformly formed, and a fluorination rate of 2 to 5 μm provides sufficient protection for calcium particles with a diameter of several μm. do.

Calcium metals with a fluorinated protective layer manufactured as described above are stable without undergoing rapid oxidation even when left in the atmosphere, and are extremely easy to handle during storage and processing. ′ is useful for expanding ′.

The calcium metal according to the present invention is extremely useful as a calumium metal refining agent mainly used for deoxidizing, desulfurizing, dephosphorizing, etc. molten steel.

Next, the present invention will be explained with reference to Examples.

As raw materials Ca: 99.7%, Mg: 0.1%, A
7: Calcium metal with a particle size of 3 to 6 mm with a composition of 0.1% is used, and the reaction device is a nickel rotary reactor (inner diameter 27.6 M x length 300 mm) equipped with a heating device. used. The reaction conditions were as shown in Table 1. In Examples 1 to 7 and Example 10, about 5 grams of metallic calcium particles were placed in a reactor, the inside of each reactor was replaced with helium gas, and then heated to a predetermined temperature. After reaching the predetermined temperature, 50% of the reaction gas containing fluorine gas shown in Table 1 was added.
It is introduced into the reactor at a ratio of cc/Mn and reacted for a predetermined time. After the reaction, the reaction gas is stopped, the inside of the reactor is replaced with helium gas, and the reactor is cooled.

Example 81 In the case of Examples 9 and 11, a 3-liter container was filled with the reaction gas having the composition shown in Table 1, and the pressure was 0.1 K.
9Cr/cni), and the reaction gas container and circulation pump were connected to the same reactor as above. Approximately 5 grams of metal carunium particles are placed in a reactor, and the interior of the reactor is replaced with helium gas and then evacuated. Introduce the reaction gas from the reaction gas container into the reactor at step 1, and operate the circulation pump to circulate the gas in the reactor.

The amount of gas to be circulated was 200 cc/=. At the same time, the reactor was heated, the temperature was raised to a predetermined temperature in about 30 minutes, and the reaction was continued at this temperature for 20 hours. After the reaction was completed, the gas circulation was stopped, and the inside of the reactor was replaced with nitrogen gas to cool it.

The reaction product treated as described above was taken out from the reactor, kept in a dry atmosphere with as little contact with air as possible, and its weight was measured.

The surface of the reaction product was gray, but the interior had a calcium metallic luster. Analysis of the reaction products other than Example 10 did not confirm that calcium fluoride was produced. Therefore, the weight increase due to the reaction was assumed to be due to the production of calcium fluoride, and the calcium fluoride production rate was calculated. These results are shown in Table 1.

The surface of the reaction product in Example 10 was yellowish brown, and the interior had a calcium metallic luster.

As a result of analyzing this reaction product, calcium fluoride was identified. Furthermore, by dissolving this reaction product in water and detecting ammonium ion/(NH)'i with a Nescar reagent, the formation of calcium nitride on the surface of the 2 was confirmed.

Next, the calcium particles subjected to the above-mentioned fluorine gas treatment and the metal calcium particles not subjected to any treatment were left standing in air at a temperature of 35±2°C and a humidity of approximately 80%, and the change in percent weight over time was measured. . The results are illustrated in FIG.

As is clear from Figure 1, calcium particles and calcium nitride that are not subjected to fluorine gas treatment are rapidly oxidized in the atmosphere, absorb moisture, turn into oxides or hydroxides, turn white, and increase in weight. is large (
G in Figure 1).

Calcium nitride is unstable, and although calcium particles are formed, they are not dense and have poor oxidation resistance (F in Figure 1).

On the other hand, calcium particles coated with a strong calcium fluoride layer are stable for a long time, and their weight increases gradually and the rate of increase is small (A to E in Figure 1). If this protective layer is destroyed, calcium exhibits the same tendency as untreated calcium.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in weight over time in an exposure test of calcium particles. A: Example 11 Example 2, Example 4, Example 6% Example 7. B: Example B. C: Example 9. D: Example 3. E: Example 5. F: Example 11. G: Untreated calcium granules and those of Example 10. Patent applicant Sei Kikuchi, patent attorney representing Showa Denko Co., Ltd.

Claims (2)

[Claims] (1) A calcium metal characterized in that the particle surface of calcium powder is covered with a protective layer consisting essentially of calcium fluoride. (2) Calcium powder particles are treated with 5 to io of fluorine gas.
o%, inert gas at a temperature range of 100 to 500°C in an atmosphere containing 95 to 0% of inert gas to form a protective layer substantially consisting of calcium fluoride on the particle surface of the granular material. A method for producing calcium metal.