JP2010269322A - Thermal insulation for molten metal - Google Patents

Abstract

An object of the present invention is to cover the surface of a molten metal with a small bulk specific gravity even with a small addition amount, and to generate heat without adding an expensive oxidation heating material such as metal aluminum powder or metal magnesium powder. The present invention provides a heat insulating material for molten metal that is excellent in heat retaining properties, has a low sulfur and phosphorus content, has no quality problems with molten metal, and is less expensive than shochu shells.
A heat insulating material for a molten metal is a heat insulating material for a molten metal which is added to the surface of the molten metal and prevents the temperature of the molten metal from being lowered by covering the surface of the molten metal. A tatami floor made of rice straw, which is the core material of the above. In this case, the size of the heat insulating material for molten metal is a size obtained by cutting a rectangular tatami floor with a size equal to or greater than 4 equal in the long side direction and equal to or greater than 2 equal in the short side direction. It is preferable that the core material of the tatami mat has the same heat retention as the shochu husk.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a heat insulating material for molten metal which is added on the surface of molten metal contained in a container such as a hot metal ladle or ladle and prevents the temperature of the molten metal from decreasing by covering the surface of the molten metal. is there.

  The hot metal discharged from the blast furnace is accommodated in a hot metal ladle or a kneading car and conveyed to the next converter process. Moreover, the molten steel decarburized and refined in the converter is discharged into the ladle and transported to the next continuous casting step. These containers are made of a refractory with low thermal conductivity on the inner wall to prevent temperature drop of the molten metal to be accommodated, but the upper side is open, and the heat of the molten metal Is diffused to the outside air, and the temperature of the molten metal decreases with the passage of the storage time. Due to this temperature drop, in the case of hot metal, the surface solidifies and it becomes impossible to discharge hot metal from the hot metal ladle, or it becomes impossible to increase the ratio of iron scrap in converter decarburization refining, etc. Problems arise, and in the case of molten steel, problems such as being unable to cast to the end in the continuous casting process occur. In particular, the temperature drop is significant in hot metal ladle and ladle with a large opening.

  Therefore, in order to prevent this temperature decrease, it is generally performed to add a heat insulating material to the surface of the molten metal accommodated in the container. In order to prevent a temperature drop, a lid for closing the opening of the container may be provided. However, the thermal insulation effect is not sufficient with the lid alone, and a thermal insulation material is used in combination.

Conventionally, shochu husk (also referred to as “carbonized charcoal”) has been frequently used as a heat insulating material in domestic steelworks. Shochu is a rice husk (raw rice husk) steamed and carbonized. The shochu husk is mainly composed of fixed carbon (content: about 49% by mass) and SiO ₂ (content: about 43% by mass), and its bulk specific gravity is about 0.11. That is, the bulk specific gravity is small, the entire surface of the molten metal is covered with a small amount, and the fixed carbon is gradually burned to generate heat, thereby exhibiting a high heat retaining effect. After the fixed carbon burns, a layer of SiO ₂ is formed to block the molten metal from the outside air. Furthermore, the content of sulfur and phosphorus, which are harmful elements in steel products, is low (total sulfur concentration: about 0.13% by mass, total phosphorus concentration: about 0.22% by mass), which can contaminate hot metal and molten steel. Absent.

  Conventionally, shochu husks are inexpensive, and the fact that they are inexpensive is the reason why they are often used as heat insulating materials, but in recent years the price has increased and alternatives have been proposed.

  For example, in Patent Document 1, a paper mill waste (pulp; 85 to 95% by mass, others; 5 to 15% by mass) dried instead of wood powder or rice husk is used as a heat insulating material. Patent Document 2 proposes a heat insulating material in which shochu husk and calcined vermiculite are mixed in a ratio of 3: 7 to 7: 3, and Patent Document 3 discloses 20 to 50 mass of paper pulp. %, 5 to 20% by mass of a carbonized product of plant fibers, 5 to 20% by mass of an inorganic material having expandability by heating, 5 to 15% by mass of an oxidizing exothermic material having oxidation and exothermicity by heating, each of the above A heat insulating material made of a solid material containing 5 to 40% by mass of a solid material for solidifying the material has been proposed.

JP-A-48-41924 Japanese Patent Laid-Open No. 7-148560 JP 2003-319883 A

  However, the above prior art has the following problems.

  That is, in Patent Document 1, it is necessary to dry the paper mill ruins, and although the paper mill ruins themselves are inexpensive, the costs associated with the drying process increase, and the heat insulating material obtained is not necessarily inexpensive. Absent.

  In Patent Document 2, calcined vermiculite is blended, and accordingly, the content of fixed carbon in the shochu husk is reduced, the heat generation effect due to combustion of the fixed carbon is small, and there is a problem in heat retention.

  Patent Document 3 has an excellent heat retention effect, but uses an expensive metal-based oxidation heat generating material such as metal aluminum powder or metal magnesium powder, which is much more expensive than shochu husk and is a substitute for shochu husk. It cannot be.

  The present invention has been made in view of such circumstances, the purpose of which, like shochu shell, is low in bulk specific gravity and can cover the surface of the molten metal even with a small addition amount, Moreover, even if expensive oxidation heat-generating materials such as metal aluminum powder and metal magnesium powder are not blended, heat is generated and heat retention is excellent, and furthermore, the content of sulfur and phosphorus is small, and the quality of molten metal is high. The object is to provide a heat insulating material for molten metal which is free from problems and cheaper than shochu.

  The heat insulating material for molten metal according to the first invention for solving the above-mentioned problem is a heat insulating material for molten metal that is added to the surface of the molten metal and prevents the temperature of the molten metal from decreasing by covering the surface of the molten metal. And it is what cut | disconnected the tatami-made tatami floor which is a plate-shaped core material of used tatami mat, It is characterized by the above-mentioned.

  In the heat insulating material for molten metal according to the second aspect of the present invention, the size of the heat insulating material for molten metal is equal to or more than four equal parts in the long side direction of a rectangular tatami floor. It is a size cut into two or more equal parts in the side direction.

  The heat insulating material for molten metal according to the third invention is characterized in that, in the second invention, it is cut into eight equal parts or more in the long side direction.

  According to the present invention, since the used tatami floor made of rice straw is cut and used as a heat insulating material for molten metal, waste is effectively used, which is significantly less expensive than shochu shells. It can be used as a heat insulating material. In addition, the composition of rice straw constituting the tatami floor is similar to that of raw rice husk, has a low sulfur and phosphorus content, has no quality problems with molten metal, and contains fixed carbon. The heat generation effect by combustion is obtained, the heat retaining property is excellent, the bulk specific gravity is small, and the surface of the molten metal can be covered even with a small addition amount.

It is a figure which compares and shows the amount of adhesion | attachment metal in a hot metal ladle with the case where a tatami floor is used as a heat insulating material, and the case where a shochu husk is used.

  Hereinafter, the present invention will be described in detail.

  In the present invention, a piece of tatami floor made of rice straw, which is a used tatami plate-like core material, is added to the surface of the molten metal contained in a container such as a ladle or a hot metal ladle, and the molten metal It is used as a heat insulating material for molten metal that prevents the temperature of molten metal from decreasing by covering the surface of the metal. Here, a used tatami mat is one that has become old and can no longer be used, or one that can be used but has been removed for some reason and is no longer used.

  The tatami mat is manufactured by wrapping the surface of a plate-shaped tatami floor (tatami mat), which is a core material, with a tatami mat (tatami mat). There are two types of tatami mats: a rectangular tatami mat with an aspect ratio of 1: 2 between the short side and the long side, and a square tatami mat with a horizontal half of the tatami mat. Both are used as heat insulation materials.

  The most traditional method of tatami flooring is to compress and dry the dried rice straw and sew it into a plate with a thickness of about 5 cm (typically 5.5 cm). Also called Toko). It effectively utilizes rice straw produced as a by-product of rice cultivation, and has high functions such as moderate elasticity, high heat retention, indoor humidity control and air purification. However, in recent years, it has been difficult to obtain materials, difficult to manufacture, heavy and cumbersome to handle, and easy to grow mold. In some cases, a new material obtained by laminating or laminating polystyrene may be used. In the present invention, a tatami floor made of rice straw, that is, a straw floor is used as a heat insulating material.

  Since the heat insulating material for molten metal is sometimes manually put into a container containing molten metal, in order to make it easier to put in, in the present invention, a material obtained by cutting a tatami floor into a plurality of pieces is kept warm. Use as material. The size of one tatami mat is vertical: 910 mm (3 scales), horizontal: 1820 mm (6 scales), but larger Kyoto (vertical: 955 mm, horizontal: 1910 mm) or smaller There are Edo spaces (length: 880 mm, width: 1760 mm), but a rectangular tatami floor with a tatami mat size of 4 or more, preferably 8 or more and preferably 2 It is preferable to use what was cut | disconnected above as a heat insulating material. In other words, considering the largest tatami floor with a kyoto size, it is preferable to cut it into a square or smaller size of vertical: 478 mm (955/2) and horizontal: 478 mm (1910/4). Desirably, it is cut | disconnected to the size below the rectangle of length: 478 mm (955/2), width: 239 mm (1910/8). In this case, it does not matter whether the tatami floor is attached to the cut tatami floor or not. A tatami mat is usually a “goza” made of dried or woven stems of grass or shichitoi, which also functions as a heat insulating material.

  Table 1 shows a measurement example of the composition and bulk specific gravity of the rice straw tatami floor in comparison with the shochu husk.

As shown in Table 1, the rice straw tatami floor is not steamed, so it has a high water content and a large amount of volatile matter, but it contains about 16.3% by mass of fixed carbon even though it is not steamed. When added over the molten metal, moisture is evaporated and removed, and volatile components are removed by combustion or vaporization, leaving fixed carbon. Moisture impairs the heat retention effect, but the volatile matter that burns increases the heat retention effect. Further, the remaining fixed carbon component burns and generates heat, thereby enhancing the heat retaining effect. In particular, the Inaba tatami floor is densely knitted, so it exhibits flame retardancy even though it has not been carbonized, and the remaining fixed carbon content does not burn at once, just like a shochu shell. It continues to burn for a long time. After combustion of the fixed carbon content, a layer of SiO _{2 in} the ash is formed on the molten metal surface to block the molten metal from the outside air. In addition, the content of sulfur and phosphorus, which are harmful elements in steel products, is low, and picking up sulfur and phosphorus from the rice straw tatami floor, which is a heat insulating material, does not cause a problem.

  Furthermore, the rice straw tatami floor is compressed and sewn, and its bulk specific gravity is larger than that of shochu husk, but it is about 0.23 at high and can be easily put in manually by an operator. it can. In particular, a tatami-sized tatami floor that is divided into 8 equal parts in the long side direction and 16 equal parts in the short side direction is divided into 16 equal parts. Can be put in.

  In using the heat insulating material made of this rice straw tatami floor, it may be used alone or in combination with other heat insulating materials such as shochu husk, wood waste, paper sludge, brick waste. Furthermore, it is possible to use not only a manual operator but also a thrower.

  As the molten metal to be kept warm, not only iron-based molten metals such as hot metal and molten steel, but also non-ferrous molten metals such as copper and aluminum can be targeted. Taking iron-based molten metal as an example, the molten metal is added from the blast furnace and added to the hot metal contained in the hot metal ladle to keep the hot metal hot, or the hot metal is discharged from the converter and ladle. The molten steel can be kept warm by adding the above-mentioned heat insulating material for molten metal onto the molten steel contained in the molten steel. Furthermore, it can be used also when it adds on the molten steel in the tundish of a continuous casting installation, and heats the molten steel in a tundish.

  As described above, according to the present invention, the used tatami mat made of rice straw is cut and used as a heat insulating material for molten metal, so that the waste can be effectively used. In comparison with this, the heat insulating material can be made much cheaper. In addition, the composition of rice straw constituting the tatami floor is similar to that of raw rice husk, has a low sulfur and phosphorus content, has no quality problems with molten metal, and contains fixed carbon. The heat generation effect by combustion is obtained, the heat retaining property is excellent, the bulk specific gravity is small, and the surface of the molten metal can be covered even with a small addition amount.

  An example will be described in which the heat insulating material of the present invention comprising an Inaba tatami floor is applied as a heat insulating material in a hot metal ladle that receives hot metal discharged from a blast furnace and conveys the hot metal to a steelmaking plant converter yard.

  The mass of the hot metal ladle in an empty state was measured in advance, and the hot metal ladle was placed directly under the blast furnace casting floor to receive about 100 tons of hot metal discharged from the blast furnace. After receiving, the hot metal temperature was measured, and then the tatami floor made of rice straw was added as a heat insulating material onto the hot metal in the hot metal pan by an operator. The size of the heat insulating material composed of the Inaba tatami floor used was about 478 mm in length, which was obtained by dividing a Kyoto tatami mat tatami floor into about 8 equal parts in the long side direction and about 2 parts in the short side direction. The width is about 239 mm. About 70 kg of this heat insulating material was added per hot metal ladle.

  The hot metal ladle containing the hot metal is transported to the continuous casting yard of the steelmaking factory for 0.5 to 1.5 hours, and the remaining molten steel in the ladle is divided into 2 to 3 times over about 4 hours in the continuous casting yard. 150 to 170 tons (add 10 to 20 tons of molten steel each time), transport this hot metal ladle to the converter yard, and store the molten iron (including molten steel) from the hot metal ladle to the converter charging pan I changed it.

  The mass of the empty hot metal ladle after this transfer was measured, and the difference between the mass of the hot metal ladle and the mass of the hot metal ladle before receiving was measured as the amount of adhered metal in the hot metal ladle. When the heat retention effect is small, the temperature drop of the hot metal in the hot metal pan is large, and the amount of adhered metal increases. Since the amount of attached metal increases as the time from receiving to transfer (referred to as “lead time”) increases, the amount of attached metal was measured with a hot metal pan with the same lead time.

  For comparison, the amount of adhered metal was also measured when shochu husk used as a conventional heat insulating material was used. The amount of shochu husk added is about 60 kg per hot metal ladle.

  In FIG. 1, the measurement result of the amount of adhering metal in the hot metal ladle is shown in comparison between the case where a tatami floor is used as a heat insulating material and the case where a shochu shell is used. In addition, FIG. 1 shows a regression equation of the relationship between the hot metal temperature and the amount of attached metal. The solid line shows the case of the tatami floor, and the broken line shows the case of the shochu shell. As shown in FIG. It was confirmed that the amount of gold was the same when the tatami floor was used and when the shochu shell was used. That is, it has been confirmed that the tatami floor made of rice straw has a heat insulation effect equivalent to that of shochu husk as a heat insulation material for hot metal.

Claims (3)

  It is a heat insulating material for molten metal that is added to the surface of the molten metal and prevents the temperature of the molten metal from being lowered by covering the surface of the molten metal, and a tatami floor made of rice straw that is a used tatami plate-like core material. A heat insulating material for molten metal, characterized by being cut.   The size of the heat insulating material for molten metal is a size obtained by cutting a rectangular tatami floor with a size equal to or greater than 4 equal in the long side direction and equal to or greater than 2 equal in the short side direction. The heat insulating material for molten metals according to claim 1.   The heat insulating material for molten metal according to claim 2, wherein the heat insulating material is melted into eight equal parts or more in the long side direction.

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