JP5542088B2 - Iron-based metal desulfurization agent, its production method and desulfurization method - Google Patents

Description

  The present invention relates to a desulfurizing agent for iron-based metals, and more particularly to a desulfurizing agent used for removing sulfur from molten iron and molten steel.

  In general, when iron contains sulfur, the quality of iron decreases. Pig iron obtained from the blast furnace contains sulfur derived from iron ore and coke. Therefore, pig iron is required to remove sulfur. For this purpose, desulfurization agent is added to molten pig iron and stirred to remove sulfur as slag. In particular, in order to obtain high-grade steel, it is necessary to reduce the sulfur content to an extremely low value. Therefore, a desulfurizing agent having high performance is required.

Various desulfurization agents have been used so far, but recently, lime, soda ash, metallic magnesium and the like are used. However, these desulfurization agents have merits and demerits as described below, and none of them is satisfactory.
Lime can be used as a desulfurization agent in the form of calcium carbonate CaCO ₃ , but calcium carbonate is only calcined to form quick lime CaO to act as a desulfurization agent. Therefore, when added to pig iron in the form of calcium carbonate, a large amount of heat is required until it becomes quick lime, and it is not advantageous because it takes time.

  Therefore, recently, calcium carbonate is calcined in advance to form quicklime CaO and is used as a desulfurization agent. However, quicklime must be desulfurized at a high temperature because of its high melting point. Desulfurization at high temperatures is not advantageous. In addition, it is inherently difficult to reduce the sulfur content particularly by desulfurization with quicklime.

  Soda ash is chemically anhydrous sodium carbonate and has a lower melting point than quick lime. Therefore, when soda ash is used, desulfurization can be performed at a relatively low temperature. However, soda ash produces white smoke when added, which makes it difficult to observe the surface of the molten iron and causes white smoke to damage the device.

  Metal magnesium also has the advantage that it can be desulfurized at low temperatures. However, since magnesium magnesium has a low boiling point, it is dangerous because the molten iron boils vigorously when added, and the loss due to vaporization is large, and the produced magnesium sulfide is reversibly decomposed into sulfur, so it can be removed quickly. I'm jealous of problems such as having to.

It has long been known that metallic calcium is effective as a desulfurizing agent. However, metallic calcium reacts with moisture in the air to generate hydrogen, and if the generated hydrogen is accumulated, there is a risk of explosion. Therefore, although calcium metal is used as an alloy with silicon, using it as an alloy is expensive and not advantageous.
In addition, in order to prevent the calcium metal from reacting with moisture, the metal calcium is made into particles and packed in an iron pipe and sealed, and this is used for desulfurization. However, if it is packed in an iron pipe, the weight increases and handling is not easy.

  In addition, it is also known that metallic calcium is produced in molten metal and the molten metal is refined by the produced metallic calcium. This is described in JP-A-6-322429. In this attempt, a powder mixture of quicklime and aluminum was formed into a briquette, which was sealed in a metal container and the container was evacuated. The container was placed in a pan and heated, and then placed in a ladle. Molten metal is injected to react aluminum and lime to produce metallic calcium. However, it is cumbersome and not easy to put a briquette in a metal container and create a vacuum.

JP-A-6-322429

  The present invention provides a new iron-based metal desulfurization agent that eliminates the above-mentioned drawbacks. That is, the present invention provides an iron-based metal desulfurization agent that can be easily manufactured, handled easily, and can be easily and efficiently desulfurized at a low temperature.

The inventor previously invented a method for stably storing metallic calcium in the atmosphere, and filed this as Japanese Patent Application No. 2010-093883.
The main point of the method is to prevent the metallic calcium from reacting with moisture in the atmosphere by forming an organic or inorganic film on the surface of the metallic calcium. A synthetic resin or the like can be used as the organic substance, and sodium silicate or the like can be used as the inorganic substance.

As a result of further research with the above invention as the beginning, the present inventors have formed a layer in which organic or inorganic powders are densely arranged on the surface of metallic calcium so that it is not continuous as a film. However, it has been found that metal calcium can be sufficiently protected for practical use.
The inventor of the present invention, when the surface of the metal calcium thus protected is put into the molten metal, the protective coating or layer is easily broken, the metal calcium is exposed, and the exposed metal calcium is molten metal. It has been found that it exhibits a strong desulfurization power. The present invention has been completed based on such knowledge.

The present invention provides an iron-based metal desulfurization agent characterized in that a film or layer made of an organic substance and / or an inorganic substance is formed on the surface of metallic calcium.
The present invention also provides a method for producing the iron-based metal desulfurization agent.
Furthermore, the present invention also provides a method for desulfurizing an iron-based metal, characterized in that a desulfurizing agent in which a film or layer made of an organic or inorganic substance is formed on the surface of metallic calcium is added to molten iron. .

  According to the present invention, the desulfurizing agent can be manufactured very easily because the iron-based metal desulfurizing agent can be obtained by simply forming a film or layer made of an organic substance and / or an inorganic substance on the surface of metallic calcium. Since the surface of metallic calcium is protected by a film or layer, the desulfurizing agent thus prepared can be safely stored because metallic calcium does not react with moisture even when left in the atmosphere.

  Moreover, according to this invention, a molten metal can be desulfurized only by throwing a desulfurization agent in a molten metal and stirring. When this desulfurizing agent is put into the molten metal, the organic matter is immediately incinerated, and the inorganic matter is also decomposed or broken down, so that the calcium metal is exposed in the molten metal. To be desulfurized. At the same time, it is deoxidized by the deoxidizing power of metallic calcium. Therefore, according to the present invention, the iron-based metal can be easily refined.

In this invention, a substantial part of the desulfurizing agent is metallic calcium. Metallic calcium is an element having an atomic number of 20 represented by an element symbol of Ca, and is one of alkaline earth metals.
Metallic calcium is a silver-white soft metal, slightly harder than lead, rich in ductility and malleability, and can be easily processed into a thin plate, rod or particle form. In this invention, metallic calcium can be used in the form of a thin plate or rod, but it is preferable to use it in the form of particles. Particles having a diameter in the range of 0.5 to 30 millimeters can be used, but in particular, the diameter is preferably about 5 millimeters or less.

In the present invention, a film or layer made of an organic substance and / or an inorganic substance is formed on the surface of metallic calcium, and this is used as a desulfurizing agent for an iron-based metal.
Various organic resins can be used as the organic substance forming the film or layer. As the synthetic resin, for example, an aqueous solution of an initial condensate of a thermosetting resin such as a phenol resin, a melt of a thermoplastic resin such as polyvinyl acetate or polystyrene, an organic solvent solution, an aqueous solution of polyvinyl alcohol, or the like may be used. it can.

As the inorganic substance forming the film or layer, water glass, that is, an aqueous solution of sodium silicate, quick lime powder, anhydrous sodium carbonate powder, metal magnesium powder, metal aluminum powder, or the like can be used.
When the organic substance or inorganic substance that forms the film can be made into a solution form, it can be formed into a solution by brushing on the surface of metallic calcium and sprayed to form a film. Preferably, the film is formed by dipping. It is a method of forming. Immersion is particularly suitable when metallic calcium is in the form of particles.

In the immersion, it is preferable to adjust the viscosity of the solution in advance so that the solution of the film-forming substance diffuses quickly on the surface of the metallic calcium and an appropriate amount adheres. Therefore, it is preferable to adjust the amount of water or organic solvent.
Immersion is performed as follows, for example. Metal calcium is made into particles having a particle size of several millimeters in advance, and this is put in a wire mesh container. On the other hand, the film-forming substance solution is adjusted to an appropriate viscosity in advance. Next, the metal calcium particles are immersed in the film-forming substance solution while being put in the container, and the container is shaken in the solution to allow the solution to permeate the particle surface without any problem. Thereafter, the container is pulled up from the solution to evaporate the solvent from the particle surface and dry the particles. In order to speed up drying, dry air is blown or the temperature is increased. In this way, a film can be formed on the surface of metallic calcium to obtain the desulfurizing agent according to the present invention.

  When water glass is used as the film-forming substance, it is preferable that water is volatilized by blowing carbon dioxide gas onto the metal calcium particles on which the water glass film is formed. In particular, it is preferable that metal calcium particles are suspended in carbon dioxide gas blowing from below, and the water is volatilized by using the particles as a fluidized bed so that the particles do not adhere to each other.

When the organic or inorganic substance forming the film is a solid, and its melting point is lower than the melting point of metallic calcium, 839 ° C., the organic or inorganic substance is heated and melted, and metallic calcium is incorporated therein. It is preferable to form a film by dipping and dipping. In this case, the dipping method can be performed almost in the same manner as the dipping in the above solution. However, it is not necessary to dry in this case.
In addition, when the inorganic substance which forms a film | membrane is a metal like aluminum, a metal can be vapor-deposited on the surface of metal calcium, or it can form a film | membrane by spraying.

  If the organic or inorganic material forming the film is solid and its melting point is higher than the melting point of metallic calcium 839 degrees C or is easily decomposed when heated, the organic or inorganic material is powdered, The powder is attached to the surface of the metal calcium particles to form a dense layer of organic or inorganic powder. At this time, the weight of the organic or inorganic powder is much larger than that of metallic calcium, and the organic or inorganic powder is made finer than the metallic calcium so that the surface of the metallic calcium particles can be made as much as possible. Cover with organic or inorganic powder. The organic or inorganic material formed in this way is suitable as a dense layer rather than a film.

  When organic or inorganic powders are adhered to the surface of metallic calcium, if the powders themselves have adhesive strength to each other, a dense layer may be formed on the surface of metallic calcium only with organic or inorganic powders. it can. However, when the powder itself does not have mutual adhesive force, a dense layer is formed by adding a binder.

  As a special case, when calcium metal is made into particles and the inorganic material is made into a fine powder with a high melting point, if the weight of the inorganic powder is more than twice the weight of the metal calcium, By simply stirring the mixture into a uniform mixture, or simply pressing the mixture into a briquette form, the calcium metal is in a state where an inorganic layer is formed on the surface.

  For example, when using quicklime powder as an inorganic substance, quicklime has an adhesive force between powders. However, since quicklime has a high melting point, it is preferable to add a melting point depressant. As the melting point depressant, fluorite, calcium aluminate or the like can be used. When the melting point depressant is added, the composition is the same as 1 to 95 parts by weight of quicklime powder passing through a 100 to 200 mesh sieve to 1 to 60 parts by weight of metal calcium particles having a particle size of 0.5 to 30 millimeters. 1 to 50 parts by weight of calcium aluminate in the powder diameter range can be mixed, and this mixture can be used as it is as a desulfurizing agent according to the present invention. Such a desulfurizing agent can be obtained.

  In the above case, it is not necessary to form a sodium silicate film or a polyethylene film on the surface of the metal calcium particles in advance. However, when the above-mentioned coating film is formed on the surface of the metal calcium particles in advance, the obtained briquette-like desulfurization agent has improved stability and becomes even better.

  Thus, the desulfurization agent composed of metallic calcium having an organic or inorganic film or layer formed on the surface can be easily handled because it can be grasped with bare hands. In addition, this desulfurization agent does not generate appreciable hydrogen even when left in the atmosphere. For this reason, the desulfurizing agent can be stored and stored for a considerable period after production. Therefore, this desulfurizing agent can be used industrially. In addition, since this desulfurizing agent has excellent desulfurizing power and deoxidizing power, it is suitable for the production of high-grade steel.

As described above, the desulfurizing agent according to the present invention hardly reacts with moisture even if it is left in the atmosphere as it is, so that it is difficult to change its quality, but it is further covered with a water-impermeable film. Therefore, it can be made more difficult to be altered. Covering with a water-impermeable film means, for example, covering with a film made of synthetic resin, for example, wrapping with a film made of polyethylene or polypropylene, or sealing the mouth of the bag in a polyolefin bag. It is. Especially when covered with a water-impermeable shrinkable film, the deterioration can be prevented for a long time.
Hereinafter, examples and comparative examples will be given to clarify the superiority of the present invention.

Example 1
The metal calcium plate was cut to produce a number of metal calcium particles having a particle size of about 5 millimeters.
On the other hand, water glass was prepared, and water was added thereto to prepare a sodium silicate aqueous solution suitable for immersion at a viscosity of about 1400 mPas (20 ° C.).
The metal calcium particles were put into a container made of a wire mesh, and this was immersed in the sodium silicate aqueous solution at 20 ° C. as it was, and the container was shaken while immersed for 3 minutes.

Thereafter, the container was pulled up from the solution and left in the air for 30 minutes to dry the metal calcium particles. The particles thus obtained were used as a desulfurizing agent.
The metal calcium particles before immersion had a particle weight in the range of 30 to 35 milligrams, but the particle weight after drying was in the range of 48 to 140 milligrams. Therefore, it was considered that 0.2 to 1.3 milligram / square millimeter of sodium silicate covered the particle surface.

This desulfurizing agent was left in the atmosphere at 20 ° C. for 1 month, but no sign of generating hydrogen was observed. Therefore, it was recognized that there was no alteration for at least one month after production.
This desulfurization agent was added to molten steel having a sulfur content of 25 ppm and a temperature of 1600 ° C. at a rate of 1000 kg of desulfurization agent per 300 ton of molten steel, and as a result of desulfurization treatment, the sulfur content could be reduced to 20 ppm. .

Example 2
In this example, the same particles as used in Example 1 were used as the calcium metal, but the surface of the particles was the calcium metal as it was and the sodium silicate film was not formed.
Moreover, in this Example, the layer of the inorganic substance was formed on the surface of metallic calcium with these powders using quicklime and a melting point depressant of quicklime. Calcium aluminate was used as the melting point depressant.

Quicklime and calcium aluminate were pulverized into fine powder that passed through a 100 mesh sieve.
100 kg of the above calcium metal particles, 700 kg of the above-mentioned quicklime and 200 kg of the above-mentioned calcium aluminate are mixed, the mixture is sufficiently stirred, and then the mixture is pressurized to form a spherical briquette having a diameter of 10 to 60 mm. The briquettes obtained were used as desulfurization agents. The molding was easy.

This desulfurizing agent was left as it was for 1 month in an atmosphere of 70% relative humidity and 20 ° C., but no sign of generating hydrogen was observed. Accordingly, it was found that this desulfurizing agent did not change for at least one month.
When this desulfurizing agent was added to molten steel having a sulfur content of 25 ppm and a temperature of 1600 ° C. at a rate of 1000 kg of desulfurizing agent per 300 tons of molten steel, a desulfurization treatment was performed, and a steel having a sulfur content of 16 ppm was obtained. .

Example 3
This example was carried out in substantially the same manner as in Example 2, but in this example, metal calcium particles having a sodium silicate film formed on the particle surface obtained in Example 1 were used.
The same calcium lime and calcium aluminate as used in Example 2 are added to the metal calcium particles in the same proportions to form a mixture. The mixture is formed into a briquette like Example 2, and this is desulfurized. It was. The molding was easy.

The obtained desulfurizing agent was left as it was for 1.5 months in an atmosphere of 70% relative humidity and 20 ° C., but no sign of generating hydrogen was observed.
When this desulfurizing agent was used for the desulfurization treatment in the same manner as in Example 2, the same effect as in Example 2 was obtained.

Example 4
This example was carried out in the same way as Example 2, but only the mixing ratio was changed.
Specifically, 200 kg of calcium metal particles used in Example 2 are mixed with 600 kg and 200 kg of quick lime and calcium aluminate used in Example 2, respectively, and this mixture is formed into a briquette, which is used as a desulfurizing agent. did. The molding was easy.

This desulfurizing agent was left in an atmosphere with a relative humidity of 70% and 20 ° C. for one month as in Example 2, but no sign of generating hydrogen was observed.
When this desulfurizing agent was added to molten steel having a sulfur content of 20 ppm and a temperature of 1600 ° C. in the same manner as in Example 2 at a rate of 500 kg of desulfurizing agent per 300 tons of molten steel, the sulfur content was reduced to 7 ppm. It was possible to reduce.

Example 5
This example was carried out in the same manner as in Example 4, except that the metal calcium particles were previously treated with a solution of an initial condensate of a phenol resin (novolak type) to form a film on the surface.
When the metal calcium particles coated with the phenol resin were used as a desulfurizing agent as in Example 4, the same desulfurization effect as in Example 4 was observed.

Example 6
This example was carried out in the same manner as in Example 3 , except that the metal calcium particles had a particle size of about 1 millimeter and were not formed into briquettes, but were used in the form of a mixture as a desulfurizing agent. . The metal calcium particles before the immersion had one particle weight in the range of 0.5 to 1 milligram, but the particle weight after drying was in the range of 0.8 to 4 milligrams. Therefore, it was considered that 0.1 to 1 milligram / square millimeter of sodium silicate covered the particle surface.
Moreover, this was added to said metallic calcium as a fine powder which grind | pulverized quick lime and calcium aluminate and passed a 100-mesh sieve. The ratio of addition was 100 kg of coated metal calcium particles, 700 kg of quicklime fine powder and 200 kg of calcium aluminate fine powder, and this mixture was mixed well and the mixture was used as a desulfurization agent as it was.

This mixture was left as it was for 1 month in an atmosphere of 70% relative humidity and 20 ° C., but no sign of metallic hydrogen generating hydrogen was observed. Therefore, this mixture was not altered for at least one month.
When this mixture was charged into molten steel having a sulfur content of 25 ppm and a temperature of 1600 ° C. at a rate of 700 kg of the mixture per 300 tons of molten steel, the sulfur content was reduced to 13 ppm. As a result, it was confirmed that this mixture can be used as a desulfurization agent.

Example 7
In this example, metallic aluminum was sprayed onto metallic calcium particles to form a metallic aluminum layer on the particle surface, which was the main material of the desulfurizing agent.
Specifically, the metal calcium plate was first cut to form metal calcium particles having sides of about 5 millimeters. The particles were dispersed on the iron plate, and metal aluminum was sprayed on the particle surfaces. The metallic aluminum was calculated to adhere to the particle surface at a rate of 2 to 2.5 milligrams / square millimeter.

  The metal calcium particles with the aluminum layer thus formed were left in the atmosphere at 20 ° C. for one month, but no sign of generating hydrogen was observed from the particles. Therefore, it was recognized that the metallic calcium with the aluminum layer formed does not change for at least one month.

  The metal calcium particles on which the aluminum layer was formed were added with fine powder of quicklime and a melting point depressant of quicklime, and this mixture was formed into briquettes to obtain a desulfurization agent. Specifically, calcium aluminate is used as a melting point depressant for quicklime, and both calcium oxide and calcium aluminate are pulverized into a fine powder that passes through a 100-mesh sieve, and a metallic calcium in which an aluminum layer is formed. After adding 700 kg of quicklime fine powder and 200 kg of calcium aluminate fine powder to 100 kg of particles and mixing the resulting mixture well, the mixture is pressurized to form a spherical briquette having a diameter of 10 to 60 mm. A desulfurizing agent was used.

This desulfurization agent was left as it was for 1.5 months in an atmosphere at 20 ° C. with a relative humidity of 70%, but no sign of generating hydrogen was observed. Therefore, it was recognized that this desulfurizing agent was not altered for at least one month.
This desulfurizing agent was added to molten steel having a sulfur content of 25 ppm and a temperature of 1600 ° C. at a rate of 500 kg of desulfurizing agent per 300 tons of molten steel for desulfurization treatment. As a result, a steel having a sulfur content reduced to 15 ppm was obtained. Thereby, it was recognized that the performance of this desulfurizing agent is good.

Comparative Example 1
In this comparative example, what used fluorite instead of metallic calcium was used as the desulfurization agent. Specifically, fluorite, quicklime, and calcium aluminate were all pulverized to obtain a fine powder that passed through a 100 mesh sieve.
After adding 800 kg of quicklime fine powder and 100 kg of calcium aluminate fine powder to 100 kg of fine fluorite powder, the resulting mixture is sufficiently stirred, and then the mixture is pressurized to form a spherical briquette having a diameter of 10 to 60 mm. This was used as a desulfurization agent. This molding was easy.

Although this desulfurizing agent does not generate hydrogen, it was left to stand in an atmosphere of 20 ° C. and 70% relative humidity for one month. Then, the desulfurizing agent was pulverized in the middle and finally disintegrated. This is because quick lime in the desulfurizing agent absorbs moisture and reacts with water.
This desulfurizing agent was added to a molten steel having a sulfur content of 25 ppm and a humidity of 1600 ° C. at a rate of 1500 kg of desulfurizing agent per 300 ton of molten steel to perform desulfurization treatment. Compared to the above examples, the amount of desulfurizing agent used was increased, and the sulfur content was finally reduced to 18 ppm after desulfurization treatment for a long time.

Claims (10)

On the surface of the metal calcium, the film or layer of sodium silicate also characterized by the formation of the powder layer of a mixture of lime and quicklime melting point depressant, an iron-based metal of the desulfurization agent.   The iron-based metal desulfurization agent according to claim 1, wherein the metal calcium is a particle having a particle diameter of 0.5 to 30 millimeters.   3. The iron-based metal desulfurization agent according to claim 1, wherein the powder of the mixture of quicklime and a melting point depressant of quicklime passes through a sieve of at least 100 mesh.   The iron-based metal desulfurization agent according to any one of claims 1 to 3, wherein the quick-lime melting point depressant is calcium aluminate or fluorite.   The mixture of the quicklime and the melting point depressant of quicklime is 1 to 95 parts by weight of quicklime and 1 to 50 parts by weight of the melting point depressant of quicklime. 5. The iron-based metal desulfurization agent according to any one of 4 above.   The iron-based metal desulfurization agent according to any one of claims 1 to 5, wherein the iron-based metal desulfurization agent is wrapped in a water-impermeable synthetic resin film, or sealed in a bag made of the film. Agent.   A method for producing an iron-based metal desulfurization agent, comprising immersing metallic calcium in a water glass aqueous solution, removing the water from an aqueous solution and volatilizing water to form a sodium silicate film or layer on the surface of the metallic calcium. .   An iron-based metal desulfurization agent characterized in that a mixture powder of quick lime and quick melting point depressant is added to metallic calcium and stirred to form a layer of said mixed powder on the surface of metallic calcium as a uniform mixture Manufacturing method.   1 to 60 parts by weight of metallic calcium particles having a particle size of 0.5 to 30 millimeters, 1 to 95 parts by weight of quick lime powder passing through at least a 100 mesh sieve, and 1 to 50 parts by weight of a melting point depressant powder of quick lime And stirring the mixture, and then pressurizing the mixture to form a briquette having a particle diameter of 10 to 60 mm.   10. A method for desulfurizing an iron-based metal, comprising introducing the iron-based metal desulfurizing agent according to claim 1 into a melt of an iron-based metal.