JPH06299263A - Method for removing slag from al or al alloy molten metal - Google Patents

Abstract

PURPOSE:To efficiently remove the slag floated on the surface of Al molten metal by adding oxide which can be subjected to thermit reaction with Al to the slag on the surface of the Al molten metal at the time of melting Al, heating the slag by this reaction and thereafter removing the resulting slag. CONSTITUTION:At the time of melting Al or Al alloy, the oxide which can be subjected to thermit reaction with Al is added to the slag on the surface of the Al or Al alloy molten metal and the slag is heated by the reaction between Al contained in the slag and this oxide and thereafter the resulting slag is removed from the molten metal. As the above oxide, SiO2 or a powdery or fragmentary mixture of SiO2 and about 2 to 10wt.% Fe2O3 is used in an amount of about 0.3 to 10wt.% based on the weight of the slag and about 0.01 to 0.3wt.% based on the weight of the molten metal. By using this method, good separation of the slag from the molten metal, easy removal of the slag and reduction of the metal loss can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing slag floating on a molten metal surface when smelting Al or an Al alloy (hereinafter represented by an Al alloy).

[0002]

2. Description of the Related Art Since Al alloys are lighter in weight, have higher specific strength and are more excellent in corrosion resistance than steel materials, they are used as outer panel materials and parts materials for vehicles such as automobiles and trains, building materials, and household electrical appliances. It is widely used as an outer plate material and can material for products. The manufacturing process for obtaining these Al alloy products is as follows.

Melting raw materials (metals, scraps, etc.) → melting
Refining → Slag → Casting → Soaking → Hot working → Cold working →
Heat treatment → Surface treatment → Inspection → Shipping Here, in the melting / refining process, oxides (alumite, etc.) on the surface of the smelting raw material and oxides generated in the melting / refining process float on the surface of the molten metal as slag. This slag is a mixture of a non-metal component mainly composed of oxide and a metal component (Al alloy). If the slag is left as it is, the non-metal component is A
Not only does it mix into the molten alloy but cause contamination of the molten alloy, but it also adheres and deposits on the furnace wall and furnace bottom after tapping, which reduces the volume of the melting furnace and adversely affects the productivity.

Therefore, it is necessary to remove slag from the surface of the molten metal as soon as possible after melting and refining. However, since this slag contains a large amount of metal as described above and has a high affinity with the molten metal, it is difficult to separate the molten metal, and if it is forcibly attempted to remove it from the surface of the molten metal, it will be discharged with a large amount of metal. Therefore, the yield of the molten Al alloy is significantly reduced. Therefore what is currently widely used as means for increasing the skimming properties, for example, KCl-AlF ₃ chloride or boiling products such as such as sparging with flux mainly or halogen-based gas (Cl _2,, six (Ethanol chloride, Freon, etc.) is blown into the slag, and the entire slag layer is heated by igniting and burning part of the metal components in the slag, melting the metal components mixed in the solid state At the same time, the oxides are changed to more stable and poor wettability with the molten metal.
The method of removing the slag after improving the hot water separation is adopted.

However, the refining agent used in this slag removal process is a halogen type, and a large amount of harmful halogen gas and hydrogen halide gas are produced under high-temperature processing conditions, so that the working environment is significantly polluted to cause a health hazard. It becomes a factor.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to
An object of the present invention is to provide a method capable of efficiently removing slag generated in the melting / refining process of alloy raw materials from the surface of a molten metal without using a harmful halogen-based refining agent.

[0007]

The constitution of the slag removal method according to the present invention which has been able to solve the above-mentioned problems is Al or Al.
In melting the alloy, an oxide that causes a thermite reaction with Al is added to the slag on the surface of Al or the molten Al alloy, and the slag is heated after the slag is heated by the reaction between Al contained in the slag and the oxide. The point is where you do. The oxide used here is SiO ₂ , Fe ₂
O ₃ , W ₂ O ₅ , Mo ₂ O _{5 and the} like are exemplified, but SiO ₂ or a mixture thereof with iron oxide is most preferable in view of the effect of improving the slag removal property and the cost.

[0008]

In the present invention, as described above, as a heating source for raising the temperature of the slag to dissolve the metal content and to change the oxide into an oxide having better removal of molten metal, an oxide (hereinafter referred to as "thermite reaction") which causes a thermite reaction with Al. , Thermite reactive oxide).
That is, the thermite reaction is, as shown by the following equation, Al
2nAl + 3MO _n → nAl ₂ O ₃ + 3M + Q In the formula, M is an element that forms an oxide, Q is a calorific value of generation, and a slag containing Al as a metal component and oxygen. Affinity is Al
If an oxide of a smaller metal is added, the oxide and A
The thermite reaction takes place between 1 and the slag is heated. As described above, a large amount of Al is mixed as a metal component in the slag, so if a suitable amount of thermite reactive oxide is added to the slag, a thermite reaction occurs with a part of the metal component, The slag is rapidly heated by the violent exothermic reaction. As a result, the remaining metal that was not consumed in the thermite reaction was melted by this heat and returned to the direction of the molten metal, reducing the amount of metal in the slag layer, and the oxide in the slag was more stable and had good release from the molten metal. It becomes a simple oxide and has excellent slag removal properties.

As described above, in the present invention, the metal component (Al) mixed in a large amount in the slag is effectively utilized, and the rapid heat generation caused by the reaction with the thermite reactive oxide is utilized to remove the slag. As long as it is intended to improve, and therefore the oxide can cause a thermite reaction with Al, for example, SiO ₂ , Fe ₂ O ₃ , W ₂ O ₅ , Mo ₂ O ₅ , Mg.
Various oxides such as O and ZrO ₂ can be used. However, among these, Fe ₂ O ₃ has a possibility of causing a fire because the amount of heat generated during the thermite reaction is excessive and abruptly occurs, and W ₂ O ₅ and Mo ₂ O ₅ are relatively expensive and reduction When the element generated by the above is mixed in the molten Al alloy, the adverse effect on the physical properties of the Al alloy product cannot be neglected. Therefore, most preferable is SiO ₂ or a small amount (about 2 to 10% by weight) for increasing the calorific value. Fe
It is a mixture of ₂ O ₃ .

When the thermite reaction occurs, Al is oxidized to Al ₂ O ₃ as shown in the above reaction formula, while the thermite reactive oxide (MO _{n in the above} formula) is reduced to M. Most of this reduction product (M) is Al
_Although it is adsorbed and held by ₂ O _3, etc., there is a risk that some of it will be mixed into the molten Al alloy. Therefore, as the thermite-reactive oxide, it is preferable to select an oxide of an element that does not easily mix as a reduction product into the molten Al alloy and does not have a bad influence even if it is mixed in a trace amount. In this sense, Si, which is a reduction product of SiO ₂ , is
Since it has a low wettability with respect to the molten Al alloy and a high wettability with respect to the slag, it also has an advantage that it is easily removed together with the slag without being taken into the molten metal.

However, in order to more surely prevent mixing of SiO ₂ and Si into the molten metal, the thermite-reactive oxide added as a heating source is added to the surface layer of the slag layer and only the surface layer is added. Therefore, it is desired that the thermite reaction is caused and the reduction product is promptly removed together with the slag.

The amount of the thermite-reactive oxide added cannot be uniformly determined because it depends on the amount of slag produced, but the entire slag layer is sufficiently heated to dissolve and remove metal components. From the meaning of utilizing the gist of the present invention that the improvement effect is effectively exhibited, 0.3 to 10 relative to the weight of the slag.
%, And it is desirable to select from the range of about 0.01 to 0.3% with respect to the weight of the molten metal.

The form of the thermite-reactive oxide added does not matter whether it is in the form of powder, granules, crushed pieces, or lumps, but it is uniformly dispersed on the surface of the slag layer without producing dust or the like. In order to uniformly heat the entire slag layer, it is preferable to add it in the form of particles or crushed pieces.

[0014]

EXAMPLES Examples of the present invention will be shown below. However, the present invention is not limited by the following examples, and may be appropriately modified and implemented within a range compatible with the gist of the preceding and the following. Both are included in the technical scope of the present invention.

Using a heavy oil-fired reverberatory furnace with a capacity of 10 tons,
JIS 1100 series Al alloy scrap (100%)
Was melted at 710 ° C. Then, when 0.2% of granular SiO ₂ was added to the slag floating on the molten metal surface with respect to the weight of the molten metal, an exothermic reaction immediately occurred, and the slag layer was heated from 710 ° C to 11 ° C in 5 minutes.
The temperature was raised to 00 ° C. During this period, no generation of harmful gas was observed. Then, when the slag was immediately removed, the slag was removed well and the slag could be easily removed. The amount of slag discharged to the outside of the furnace was about 3% by weight of the molten metal weight, and the metal content contained in this slag was about 30% by weight,
It was confirmed that the metal content in the slag (80 to 90% by weight) when the slag was removed without adding SiO ₂ could be significantly reduced. The increase in the amount of Si in the molten Al alloy produced by this slag treatment was less than 0.01%, which was not a problem in terms of quality.

[0016] On the other hand, the halogen-based flux _{(KCl + K 2 SO 4 +} K 3 AlF 6 + KNO 3) molten metal relative to the weight as a comparative example 0.
When the slag was heated and the slag was removed in the same manner as above except that 1% was added, almost the same slag removal property as above was obtained. However, in this method, a large amount of chlorine gas and hydrogen chloride gas are generated in the treatment step, and the work atmosphere is significantly polluted, so work in an open state is extremely dangerous, and a large-scale suction and exhaust duct is required, and the exhaust gas is For emission to the atmosphere, it was necessary to attach exhaust gas purification equipment from the viewpoint of pollution prevention.

[0017]

EFFECTS OF THE INVENTION The present invention is constituted as described above, and by effectively utilizing thermite-reactive oxide containing no halogen compound as an exothermic agent, the slag can be efficiently heated without producing harmful gas. As a result, the metal content in the slag can be efficiently returned to the molten metal, and the slag can be removed from the molten metal efficiently, and the metal loss can be efficiently removed while the metal loss is reduced as much as possible.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Ikeda 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works, Ltd. Chofu Works (72) Inventor Osamu Domoto 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Shares Company Kobe Steel Works Chofu Works (72) Inventor Takayuki Kitano 14-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Kobe Steel Works Chofu Works

Claims (2)

[Claims] 1. When melting Al or an Al alloy, an oxide that causes a thermite reaction with Al is added to the slag on the surface of the molten Al or Al alloy, and Al contained in the slag is added.
A method for removing slag from an Al or Al alloy molten metal, characterized in that the slag is heated by a reaction of the oxide with the oxide and then removed. 2. The slag removal method according to claim 1, wherein SiO ₂ or a mixture thereof with iron oxide is used as the oxide.