JPH083610A - Agent for preventing fall of molten iron temperature for steel making - Google Patents

Abstract

PURPOSE:To obtain an agent for preventing fall of molten iron temp. in steel making capable of rising the molten iron temp. by a combustion heat effect and exhibiting a heat insulating effect by containing specific amts. of Al particulate matter, CaO-Al2O3, Fe-Si, Al and C. CONSTITUTION:This agent for preventing fall of molten iron temp. is prepd. by contg. 20 to 40% Al particulate matter, 5 to 20% calcium aluminate (CaO-Al2 O3), 3 to 15% Fe-Si dr metal Si, 2 to 10% Al or Al-Mg particulate matter, <=5% C or expanded graphite, etc., and further, adding vermiculite or baked chaff thereto at need. The agent described above effectively retains the rising of the molten iron temp. The agent for preventing fall of molten iron temp. induces a thermit reaction with the molten iron and its slag as heat sources and raises the molten iron temp. by utilizing its rapid combustion heat effect. In addition, the agent improves the yield by reducing the iron oxide in the slag. Further, the resultant product of combustion covers the molten iron surface by expanding its volume, exhibits a heat retaining effect and permits control of the combustion time as well.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a hot metal ladle in a steelmaking plant,
The present invention relates to a hot metal temperature drop preventive agent for steelmaking such as a hot metal ladle, a tope car (a hot metal cart), and the like.

[0002]

2. Description of the Related Art Conventionally, hot metal that has become a metal in a blast furnace at a pig iron factory is transferred to a toped car (mixing pig car) or a hot metal ladle, or partially held by a top speed car (mixing pig car), and then a converter. After that, it was subjected to treatments such as desiliconization, dephosphorization, decarbonization, desulfurization, etc., and then alloys were added to obtain the desired steel types and products.

However, in recent years, new technology developed in Japan,
Commonly known hot metal pretreatment method (eg ORP etc. at Nippon Steel)
By this, it becomes possible to perform the desiliconization treatment or dephosphorization treatment that was conventionally performed in the converter in the intermediate step of the conventional blast furnace-converter, such as in the blast furnace casting bed, that is, in the hot metal gutter or the toped car or in the hot metal ladle. It has succeeded in rationalizing, that is, reducing the processing load particularly in the converter.

[0004]

However, the new method described in the prior art does not involve a rapid temperature rising (heating) reaction such as a desulfurization reaction due to oxygen gas blowing in a converter, and the hot metal is not used. The current situation is that the hot metal temperature is lowered by the treatments such as desulfurization and dephosphorization in the above.

An excessive rise in the hot metal temperature is unnecessary for refractory protection, but for example, vacuum treatment without a heating device, that is, post-treatment after the converter such as RH or DH treatment is considered. Therefore, lowering the hot metal temperature is not always preferable.

From the background described above, in recent years, there has been a remarkable tendency to use the hot metal after the hot metal pretreatment from the blast furnace as a part of the iron source in the electric furnace steelmaking process. That is, the conventional electric furnace steelmaking is performed by using iron scrap as a main raw material, and is said to be a representative industry of the recycling industry.

However, due to fluctuations in scrap prices, high quality of products in recent years, demands for virgin products due to demands for clean steel, etc., electric furnace steelmaking by partially using hot metal that can meet those demands is also possible. This is part of the current situation. In this case, in particular, unlike the converter steelmaking method, there are restrictions from the equipment side, and in some cases it is necessary to keep the hot metal in the temperature and keep it warm due to the difference in capacity from the electric furnace side that receives the hot metal supply. Many.

[0008] For example, even if the hot metal is supplied at 250t topede, due to the balance of the furnace capacity on the electric furnace side, for example, in the case of 100t electric furnace, 50% hot metal compounding operation, one use is 40 to 60t. Since it is used for about 1 time, there is a problem that the temperature of the hot metal in the tope car decreases when the residual hot metal becomes low. In order to solve these problems, there are some cases where an electric hot metal heat insulation device is installed, but the cost is high and the effect is small.

Therefore, the present invention was created in view of the above existing circumstances, and uses hot metal and its slag as a heat source to rapidly burn (thermite reaction) by an exothermic reaction, and the amount of heat thereof is increased. An object of the present invention is to provide a hot metal temperature lowering agent for steelmaking that can raise the hot metal temperature by utilizing it, and at the same time can cover the hot metal and exert its heat retaining effect, and at the same time control the combustion time.

[0010]

In order to achieve the above object, the present invention provides 20 to 40% of Al powder particles, 5 to 20% of calcium aluminate (CaO-Al ₂ O ₃ ) and Fe-Si.
Or 3 to 15% of metal Si, Al or Al-Mg powder particles
2 to 10%, C or 5% or less of expanded graphite, etc. are used to utilize the combustion exothermic effect, and if necessary, add vermiculite or chaff to increase the temperature of the hot metal and keep it warm. It is characterized by

[0011]

[Function] Using hot metal and its slag as heat sources, Al, C, M are added to iron oxides such as FeO and Fe ₂ O ₃ contained in the slag.
g and Si are made to react with each other and burned rapidly (Thermit reaction). A large amount of heat generated at this time is used to raise the hot metal temperature, and the iron oxide contained in the slag is efficiently reduced to improve the yield.

Further, the oxygen contained in the slag or the hot metal is used to cause a rapid exothermic reaction with Al, Mg, Si and C, and the heat retaining effect is exerted even with the heat.

Here, the hot metal is efficiently covered by Al ₂ O ₃ , SiO ₂ , MgO and the like produced after combustion of Al, Si, Mg and the like, and a heat retaining effect is exhibited. Further, the blended calcium aluminate exerts an effect of foaming the slag existing in the upper layer of the hot metal, and further enhances the heat retaining effect. In addition, the expanded graphite blended is approximately 100-200 after combustion.
Since it expands twice, it effectively covers the slag and exerts a heat retaining effect.

On the other hand, Al and Si (Fe-S) used to control rapid combustion (thermite reaction)
i), C, Mg, etc. are changed in their composition depending on the use conditions such as the hot metal capacity and the holding and holding time.

Further, in order to control the burning time and further enhance the heat retaining effect after burning, vermiculite or chaff is added and mixed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the case of using the agent of the present invention in FIG. 1 or in a 250t tope car (mixed pig car) at the time of supplying hot metal to an electric furnace. The relationship diagram between the temperature drop of the hot metal and the passage of time is shown.
Oxidation of Al, Mg, Si, C, etc. is an exothermic reaction, and is accompanied by a rapid heat generation by utilizing oxygen in the hot metal or slag. Also, in order to control the rapid combustion (thermite reaction), Al, Si (Fe-Si), C, Mg
Etc. are used, and the composition is changed depending on the use conditions such as the hot metal capacity and the holding and holding time for the particle size of about 0.5 mm to 5 mm. In particular, for Al, the surface of the Al grain is Al ₂
The composition coated with O ₃ is blended and the burning time is controlled.

The hot metal temperature drop preventing agent according to the present invention comprises 20 to 40% of Al powder particles in the hot metal and calcium aluminate (CaO).
-Al ₂ O ₃ ) 5 to 20%, Fe-Si or metal Si
3 to 15%, Mg or Al-Mg alloy powder particles 2 to 10%,
C or expanded graphite (expandable graphite) 5
% Or less, etc., and by utilizing its combustion exothermic effect, the hot metal temperature is kept warm.

The expanded graphite (expandable graphite) is produced by treating natural scaly graphite having good crystallinity with sulfuric acid and an oxidizing agent, washing it with water, dehydrating it, and drying it. It has characteristics such as sex.
Especially, by heating rapidly (800 ℃ -1000 ℃), C
Expandable graphite expands 100 times to 300 times in the axial direction, and the expanded expandable graphite is entangled with each other to form an extremely bulky mass (bulk specific gravity 0.01), which is an excellent heat insulating material and heat insulating material. By compressing this, a compression molded product having anisotropy and having extremely good crystallization can be obtained. For example, expandable graphite expanded 120 times can be compression molded into various shapes without using a binder. These compression molded products have chemical resistance, durability and heat resistance that are higher than those of conventional asbestos and PTFE. sex,
The airtightness is excellent, and the electrical conductivity and thermal conductivity are the physical properties of the raw material graphite.

Using hot metal and slag as heat sources and reacting with iron oxides such as FeO and Fe ₂ O ₃ contained in the slag, Al, C, Mg and Si are rapidly burned (thermit reaction). Then, the amount of heat is used to increase the hot metal temperature and reduce the iron oxide contained in the slag. Further, the hot metal is covered with graphite, Al ₂ O ₃ , SiO ₂ , MgO, etc. generated after combustion of Al, Si, Mg, etc., and its heat retaining effect is exhibited. Further, calcium aluminate (CaO-Al ₂ O ₃₎ reacts with the slag on the hot metal, further enhanced heat insulating effect is foam the slag. In addition, expanded graphite (expandable graphite), rice hulls, vermiculite, etc. are also effective in retaining heat. Specifically, for example, expandable graphite (expandable graphite) 5% or less, including those that cover the surface of slag such as chaff and vermiculite, the optimum effect is about 0.5 kg / t per 1 ton of hot metal. Demonstrate.

The method of using the inhibitor of the present invention is as shown in FIG. 2, in which the hot metal that has become metal in the blast furnace at the ironmaking plant is transferred to a tope car (a hot metal cart) or a hot metal ladle, or a part of the tope car (a hot metal mixture). Car, etc., and then desilvering or dephosphorizing that was conventionally carried out in a converter, such as a blast furnace cast bed, that is, a hot tub, a tope car, or a hot metal ladle, etc. Then, desiliconization treatment or dephosphorization treatment is carried out, and the process moves to the next step. In this case, when the hot metal is held in a tope car, a hot metal ladle, a hot metal mixing furnace, etc., this agent is added onto (slag-hot metal) to prevent the hot metal temperature from lowering and to keep the temperature warm.

[0021]

As described above, according to the present invention, FeO and F containing hot metal as a heat source and slag are contained.
The iron oxide such as e ₂ O ₃ is reacted with Al, C, Mg, and Si to rapidly burn (thermite reaction). The amount of heat generated at this time is used to raise the hot metal temperature, and the iron oxide contained in the slag can be efficiently reduced to improve the yield, and also in the slag or the hot metal. Utilizing contained oxygen, Al, Mg, Si,
A rapid exothermic reaction with C can be performed, and the heat retaining effect can be exhibited even with the heat. The blending calcium aluminate (CaO-Al ₂ O ₃₎ can be further enhanced heat insulating effect is foam the slag present on the molten iron.

Further, the hot metal can be efficiently covered by Al ₂ O ₃ , SiO ₂ , MgO and the like produced after the combustion of Al, Mg, Si and the like to exert a heat retaining effect, and the expanded graphite blended is Since it expands about 100 to 200 times after burning, it can efficiently cover the slag and exert a heat retaining effect.

On the other hand, Al and Si (Fe-S) used to control rapid combustion (thermite reaction)
The particle size of i), C, Mg (Al-Mg) or the like is changed depending on the use conditions such as the hot metal capacity and the holding and holding time, so that the heating can be performed under the optimum conditions.

Further, vermiculite or chaff is added and mixed in order to control the burning time and further enhance the heat retaining effect after burning.

Therefore, the hot metal and slag are used as heat sources and reacted with the iron oxides such as FeO and Fe ₂ O ₃ contained in the slag to rapidly burn Al, C, Mg and Si (thermit reaction). The amount of heat is used to raise the hot metal temperature and to reduce the iron oxide contained in the slag in order to improve the yield. At the same time, for example, graphite and Al ₂ O ₃ produced after combustion are added. ,
In addition to covering the hot metal with SiO ₂ , MgO, etc. to exert its heat retaining effect, the addition of calcium aluminate makes the slag foam and further enhances the heat retaining effect, and furthermore, the burning time can be controlled. is there.

[Brief description of drawings]

FIG. 1 is a graph showing an effect of a heat retaining agent according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a process of using the inhibitor of the present invention.

Claims (1)

[Claims] 1. A The Al granular 20-40%, calcium aluminate _{(CaO-Al 2 O 3)} 5~20%, 3~15% of Fe-Si or metal Si, Al or Al-Mg powder particles The 2
Steel making for the purpose of increasing the temperature of hot metal and keeping it warm, containing up to 10%, C or 5% or less of expanded graphite, etc., utilizing its combustion exothermic effect, adding vermukilite or chaff, if necessary. Hot metal temperature drop prevention agent.