JPS5921488A - Exothermic material - Google Patents

Abstract

PURPOSE:To obtain an exothermic material of a compression molded body of a high density which has extremely good ignitability and reactivity and by which high temp. is easily obtd. in an exothermic material composed of alloy consisting essentially of Mg and ferric oxide, by specifying the grain sizes of both. CONSTITUTION:This exothermic material consists of the compression-molded body of a mixture composed of (A) powder of <=200 mesh grain size of an alloy consisting essentially of Mg and (B) pulverized ferric oxide of <=200 mesh grain size. Since it is difficult to obtain the powder A of desired grain sizes by direct grinding, H2 is caused to react with an Mg alloy to form hydride which is then ground. The powder obtd. in such a way is subjected to a heat treatment under a reduced pressure to dissociate hydrogen from the metal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat generating material made of a mixture of a magnesium alloy and ferric oxide.

Many types of exothermic agents have been known in the past, but among them there is one known as thermite, which has a large calorific value and can generate high temperatures. this is,
Ferric oxide is used as an oxidizing agent, and aluminum, magnesium, or an alloy thereof is used as a combustible agent.

This is used as an incinerator, heating agent, melting agent, heat transfer agent, etc., but when it is made into a high-density compression molded product to increase the calorific value per unit volume, its ignition reactivity becomes extremely poor. It has the following drawbacks.

Among the above-mentioned heat generating materials, ferric oxide-magnesium based ones react as shown in the following formula, and generate approximately 2000 ml/cm3.
It releases a lot of heat.

Fe2O3 + 3MgO → 3MgO + 2Fe Therefore, if this ferric oxide-magnesium-based heat generating material can be made to generate heat as a high-density compression molded body, the temperature during the reaction will be a high temperature that cannot be produced with normal materials. It is clear that However, with the current technology, a drug having a diameter of about 5 mm or less and compressed F-molded at a pressure of about 30 kg/cm2 does not react even if an attempt is made to ignite it.

The inventors have overcome the aforementioned drawbacks found in the prior art,
As a result of intensive research to develop a heat generating material made of a micro compression molded body that generates heat at high temperatures, the present invention was completed.

That is, according to the present invention, (A) a fine powder of an alloy containing magnesium as a main component and having a particle size of 200 mesh or less, and (B)
A heat generating agent is provided which is a compression molded product of a mixture with finely powdered ferric oxide having a particle size of 200 mesh or less.

One component (A) of the heat generating material components of the present invention is an alloy mainly composed of magnesium, which has a particle size of 200.
It is necessary to use it in the form of a fine powder of no more than 270 meshes, preferably no more than 270 meshes. According to the research conducted by the present inventors, alloys mainly composed of magnesium have a particle size of 2.
When the particle size becomes smaller than 00 mesh, the reactivity increases rapidly, and when mixed with fine ferric oxide powder, it can easily ignite even as a compact high-density compression molded product. There was found. In a ferric oxide-aluminum oxide heating element, no matter how fine the aluminum powder is made, its reactivity does not improve significantly, and the reactivity cannot be significantly improved by reducing the particle size to 200 mesh or less as described above. This is a unique phenomenon seen in magnesium-based materials. Magnesium alloys include, in addition to magnesium, one or more metals that can be alloyed with magnesium, such as nickel, manganese, zinc, iron, zirconium, calcium, aluminum, titanium, and chromium. It generally contains 70% by weight or more, preferably 85% by weight or more of magnesium.

Further, the particle size of the ferric oxide component (B) is a fine powder of 200 mesh or less, preferably 320 mesh or less. In the heat generating material of the present invention, this ferric oxide (B) has a weight ratio B/A of 87 to the magnesium alloy component (A).
．． It is used in a range of 5/12.5 to 75.0/25.0. Note that the mesh referred to in the present invention is based on a Taylor standard sieve.

The exothermic material of the present invention includes, as long as it does not impede the purpose of the present invention.
Various metal oxides, peroxides, chlorates, perchlorates, permanganates, sulfates, such as copper oxide, barium peroxide, barium sulfate, potassium permanganate, potassium perchlorate, etc. In addition, combustible agents such as silicon, zirconium, boron, magnesium, titanium, iron silicon, etc. can also be added.

In the present invention, the mixture of the magnesium alloy component (A) and the ferric oxide component (B) is used as a compression molded body in an appropriate shape. In this case, the shape may be arbitrary, such as a plate, a rod, or a cylinder. Compression molding is carried out by filling the mixture into an appropriately shaped mold and compressing the mixture. In this case, the pressure is usually 10k
g/cm2 to 500kg/cm2, preferably 200k
g/cm2 or more, and during compression molding, binders such as sodium stearate, paraffin, beeswax, etc. can also be used as auxiliary components to improve physical properties.

The heat generating material of the present invention usually has a density of 2.0 g/cm3 or more,
Preferably it has 2.9 g/cm3 to 3.10 g/cm3.

Since the magnenium alloy used in the present invention has high extensibility, it is difficult to directly crush it into a desired particle size. However, after a magnesium alloy is reacted with hydrogen to form a hydride, this is ground into a fine powder with a particle size of 200 mesh or less, preferably 270 to 320 mesh, and then this finely ground product is heat-treated under reduced pressure to form a hydride. Dissociate hydrogen from inside. In this way, a desired finely powdered magnesium alloy can be easily obtained. In the present invention, it is advantageous to use as the heating material component a magnesium alloy containing 2 to 5% by weight of the alloy component, which has been pulverized through such a metal hydride. The heat generating material of the present invention can not only be used for the same purposes as conventional heat generating materials, but also as a micro-compression molded product, it has extremely good ignition and reactivity, and has the ability to easily reach high temperatures. Not can be used in many fields. In the case of the present invention, it can be particularly advantageously used as a rod-shaped or linear molded product with a diameter of 5 mm or less, a plate-shaped molded product with a thickness of 3 mm or less, and the like.

For example, a rod-shaped molded body with a diameter of about 3 mm can be used as a minute welding rod for adhering small parts of metals together or for melting and cutting small parts of metal by utilizing its high-temperature exothermic property.

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

Example 1 An alloy powder consisting of 97% by weight of magnesium and 3% by weight of nickel with a particle size of approximately 100 mesh was reacted with hydrogen gas at a temperature of 350°C and a pressure of 50kg/cm2G.
We created a hydride of the magnesium-nickel alloy. Next, this hydride was pulverized to a particle size of 270 mesh or less, and then heated to about 200° C. under reduced pressure to obtain a fine magnesium-nickel alloy powder. Furthermore, since metallic magnesium and its alloy containing 2% by weight of nickel are very soft metals, it is difficult to reduce the particle size to less than 200 mesh as described above even if they are pulverized by ordinary pulverization methods. In this case, the limit is pulverization of about 100 meshes. Therefore, in the case of the present invention, the above-mentioned hydride-mediated pulverization method was used for pulverizing magnesium.

Next, 18.6% by weight of this magnesium nickel alloy fine powder and 81% of ferric oxide powder (particle size of 200 mesh or less)
．． 4% by weight, and this mixture was weighed 200 kg.
It was compression molded into a rod shape with a diameter of 3 mm and a length of 30 mm at a pressure of /cm2.

When this rod-shaped molded product was placed in a metal container, sealed tightly, and electrically ignited using a resistance wire at the top end, ignition was successful, and it was confirmed that the reaction progressed to the other end in an incandescent state. . In this case, the reaction temperature reaches about 3,000° C., and if air is present in the container, it will expand explosively. Since the volume of gas is proportional to its extreme temperature, in this case it expands explosively ten times. In other words, the pressure increases to 10 atmospheres.

Therefore, the compression-molded product should be highly dense and free of bubbles. That is, it has been found that it is preferable to compress the material to a density of 2.5 g/cm3 or more or to maintain the container under reduced pressure.

For comparison, rod-shaped compression molded products were obtained in the same manner as described above using magnesium-nickel alloy powder and pure magnesium metal powder with a particle size of about 100 mesh. I tried to ignite this thing in the same way as above, but it did not react at all.

Example 2 An alloy consisting of 90% by weight of magnesium metal and 10% by weight of nickel was pulverized into a fine powder with a particle size of 270 mesh or less, and 19.2% by weight of this pulverized product was mixed with 80.8% of ferric oxide with a particle size of 320 mesh or less. % by weight was mixed.

Next, this mixture was made into a rod shape with a diameter of 2 mm at a weight of 100 kg/cm.
After compression molding in a container at a pressure of m2 and sealing it,
When it was ignited and its combustion characteristics were examined, it was confirmed that it burned uniformly at a speed of 1.5 cm/sec.

In addition, in the above, the product formed into a rod shape with a diameter of 5 mm under the condition of a pressure of 100 kg/cm2 was placed in a closed metal container.
It was confirmed that it burns at a speed of cm/sec.

Furthermore, in the above, when the particle size of the magnesium alloy was varied and rod-shaped molded products with a diameter of 2 mm were made in the same way and the combustion characteristics were investigated, it was found that the particle size of the magnesium alloy was 200 mm.
It has been found that the combustion characteristics are rapidly improved when the particle size becomes smaller than the mesh area. In other words, it was found that compacts of magnesium alloy with a grain size of 200 mesh or less can be easily ignited, and the combustion reaction proceeds at a uniform rate without interruption, whereas with grain sizes larger than that, the ignition reaction is unfavorable. .

Note that since nickel in the magnesium alloy hardly reacts with ferric oxide, the higher the nickel content, the lower the calorific value of the molded article. If the nickel content exceeds 30%, the calorific value per unit weight decreases, and at the same time, the ignitability and combustibility become inferior. It is preferable to do so.

Example 3 Fe, Cr, Mn, Sn, C as magnesium alloy
Using an alloy containing various metals such as a or Zr, a heat-generating material manufactured under the same conditions as in Example 2 was made into a rod-shaped body with a diameter of 2 mm at a pressure of 300 kg/cm2, and its combustion characteristics were examined, and it was found to be similarly good. It was confirmed that the fuel had excellent combustion characteristics.

Claims (1)

[Claims] (1) (A) Particle size of alloy mainly composed of magnesium 2
A heat generating material comprising a compression-molded mixture of (B) fine powder of 00 mesh or less and (B) fine powder ferric oxide with particle size of 200 mesh or less.