JPS5856015B2 - Calcium alloy manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a calcium-based alloy as a cleaning agent suitable for removing nonmetallic inclusions or impurities present in molten steel or molten alloy iron.

In the description of the present invention, hereinafter, calcium will be abbreviated as Ca, aluminum as A and (-), and silicon as Sl.

Conventionally, Ca-8i alloys and CaC2 (calcium carbide) are known as this type of cleaning agent.

These cleaning agents are naturally effective, but on the other hand, Si or carbon inevitably remains in the product, so for steel types or ferroalloys that do not want to remove these substances,
Its use has its own limitations.

In addition, although metallic Ca has excellent effects as a cleaning agent,
Due to its high vapor pressure, there is a large amount of volatilization during use, and because of its high affinity with oxygen, there is a large loss due to combustion, etc. Therefore, the yield during use is very low, and it is also an expensive metal. Therefore, it was difficult to use it on an industrial scale.

Therefore, the appearance of a physically and chemically stable and inexpensive Ca-based alloy has been desired.

The present invention provides a method for producing an alloy mainly consisting of Ca and A7, which eliminates these conventional drawbacks.

The first invention of the present application, as stated in the claims,
When reducing Ca oxide with molten Al, the molten Al
The blending ratio for Ca oxide is 0.5 to 30 times the stoichiometric amount that satisfies the following formula, and 1350 to 1800
℃, and the reduced Ca is obtained as a molten alloy with Al, the second invention is a method for producing a Ca-based alloy in the first invention.
.

Ca oxide is reduced with molten A7 in the presence of an additive element for specific gravity adjustment consisting of one or more metals or alloys of Cr, Mn, and Ni, and the reduced Ca is added to the additive element for specific gravity adjustment and This is a method for producing a Ca-based alloy, which is characterized in that it is obtained as a molten alloy with Al.

As a known technique similar to the present invention, there is thermal reduction of Ca oxide with Al, and the outline thereof is as follows.

Ca oxide can be reduced with Al using the same retort and equipment as the Mg silicon iron reduction method.

CaO:Al-3
Mix briquettes with a ratio of = 2 (molar ratio) and 1O-
Reduce at 1050-1200°C in vacuum below 37IL flow Hg.

The Ca vapor condensation area is maintained at a temperature of 740 to 680°C.

Ca oxide is made by burning limestone and contains less than 3% impurities, M
gO is required to be 1% or less.

High-purity Ca for uranium production is produced by volatile purification.

The thermal reduction method described above requires complicated and expensive equipment because it is produced under vacuum using a retort.
Requires advanced technology and operations, such as the need to externally heat the retort to a temperature of 0.000C.

Therefore, Ca as a product inevitably becomes expensive.

There is also a method of melting metallic Ca and A7 to form an alloy, but this is not a good idea as it also uses expensive Ca as a raw material.

The method of the present invention utilizes the reduction reaction with Al shown in formula (1).

According to actual measurements, the reaction initiation temperature is about 1350'C.

Further, the reaction rate is quite high even in a low temperature range of 1500° C. or lower, and the higher the temperature is, the higher the vapor pressure of the Ca produced and the greater the evaporation loss.

In other words, part of the Ca produced by reduction in equation (1) evaporates and comes into contact with 02 in the atmosphere to become CaO and return to the slag, or it becomes Ca vapor and evaporates out of the system. However, the remaining Ca forms a metallic bond with Al, which is a reducing agent, and forms Ca-A in the form of CaAl4 and CaA72.
1 alloy.

Here, the content of Ca in the Ca-A1 alloy is centrally determined by the blending ratio of AA, which is a reducing agent, and the degree of mixing of other components. C
The evaporation rate of a also plays a role.

The feature of the present invention is that the reaction is carried out in the temperature range where the above (reduction reaction rate) - (Ca evaporation rate) is greatest, and especially at temperatures above 1800°C, the evaporation loss of Ca becomes enormous. , it's not a good idea.

Therefore, the reaction temperature range in the method of the present invention is 1350 to 1
The temperature is limited to 800℃, but if the fluidity of the produced slag and the evaporation loss of Ca are considered, the temperature is 1450~16
50°C is preferred.

On the other hand, CaO has a high melting point and is in a solid phase in the above reaction temperature range unless a special flux is used, but the reducing agent has a low melting point and is in a liquid phase, so the contact area between the two increases. Therefore, the reaction of formula (1) proceeds satisfactorily even in a solid phase-liquid phase system.

In addition, the Ca-A1 alloy and Ca
The freezing point of 0-A7203 series slag varies depending on its component composition, but it is approximately 900-950℃ and 125℃, respectively.
Since the temperature is about 0 to 1300°C and the products are in a liquid phase, general metallurgical operations can be applied to their treatment.

However, in order to make the stirring operation easier in the reaction of formula (1), there is also a method of adding and blending other oxides as a flux for the purpose of lowering the melting point or viscosity of CaO, but in the method of the present invention, Since AA, which has a strong reducing power, is used as a reducing agent, it may also reduce the fluxing agent added for the above purpose and impair the quality of the resulting Ca-A1 alloy. As an agent, C
A-type compounds are preferred.

Therefore, the oxides of Ca in the method of the present invention refer to oxides, carbonates, hydroxides, halides, and carbides of Ca such as quicklime, limestone, fluorite, and carbide, which are converted into oxides during the reduction reaction. It includes one kind or a mixture of two or more kinds of these.

However, the Ca oxide that is generally available on an industrial scale contains impurities such as SiO2, Mg02A1203. Fe
It is common knowledge that 2O3 and the like are mixed in, but any proportion or amount that does not interfere with the reduction reaction of formula (1) and the produced Ca-A7 alloy is acceptable.

Further, the higher the purity of A7 used in the present invention, the more preferable it is, but it is not limited to pure aluminum, and may contain about 90 to 98% of A1 and some M g + S t % or in some cases AI! It also includes so-called phased aluminum and recycled aluminum containing 203 and the like.

Next, practical heating methods can be roughly divided into induction heating methods and arc heating methods.

The Ca-A1 alloy obtained in the first invention of the present application has a lower specific gravity than slag, so in the molten state, the formed metal is on top and the slag is on the bottom, but there are operational problems when using the induction heating method. Not at all.

In the arc heating method, the power load state tends to become very unstable, and there is a possibility that it becomes difficult to continue the operation, but this problem can also be solved according to the second invention method of the present application.

That is, by adding additive elements for specific gravity adjustment that do not cause contamination to the steel or ferroalloy for which the Ca-A1 alloy is used, and adjusting the specific gravity of the Ca-A1 alloy to be lower than that of slag, the arc heating method can be applied. can be easily operated.

Here, the additive elements for specific gravity adjustment include Fe and Cr.

One or more metals or alloys of Mn and Ni are used.

Next, the blending ratio of A7 to Ca oxide will be explained.

Quicklime with a purity of 93% and Al with a purity of 98.5% were mixed in various proportions and heated to 1500°C in a 25KVA high frequency induction heating furnace.
and 16,000C in the atmosphere under normal pressure, and the relationship between the Ca content and the blending ratio of Al in the resulting molten metal was determined as shown in the figure.

Here, the blending ratio of Al is shown assuming that the stoichiometric amount of AA satisfying the above formula (1) is 1 equivalent.

In the figure, the solid line in the graph is not displayed when the Al blending ratio is less than 0.5 equivalent, but this is because the formation of Ca-A7 alloy was not observed.

Since the method of the present invention is a manufacturing method that provides a Ca-based alloy with a cleaning effect, the Ca content in the product is preferably as high as possible, and even if the Ca content is 2 to 3%, it is not practical. Although it does exist, it is preferably 5% or more.

From the above, it can be seen that the preferable Al blending ratio is 0.5 to 30% when the above conditions are taken into consideration.

The reaction atmosphere may be in the air under normal pressure, but a neutral or inert atmosphere is preferable in consideration of combustion loss of Al and Ca.

Further, in consideration of evaporation and transpiration of Ca in the formed alloy, it is preferable to operate under pressure rather than under atmospheric pressure.

Example 1 Table 1 shows the chemical composition of the raw materials used in this example.

After heating 50 g of quicklime to 1600'C in an artificial graphite crucible using a 2SKVA high frequency furnace, metal AA 31
．． 9 was charged.

The mixture was maintained at 1600° C. for 10 minutes with appropriate stirring to obtain 28.0 g of metal and 51.2 g of slag shown in Table 2.

Furthermore, as a result of X-ray analysis of this metal, AI34Ca and A72Ca were confirmed.

Example 2 300 g of quicklime, 90 g of fluorite, and A158 metal were placed in an artificial graphite crucible in an Ar gas atmosphere using a 25 KVA high frequency furnace.
0g and 95g of steel scrap were mixed and melted and held at 1500'C for 5 minutes to form 685g of metal and 315g of slag shown in Table 3.
I got g.

The result of X-ray diffraction of this metal was A14Ca.

AlsF'e, Al was recognized.

Example 3 Using a 330 KVA high frequency furnace, 128 ky of quicklime, 128 kg of fluorite, and 793 kg of metal A were melted at the same time.
The strain was maintained at 00 to 1600°C for about 10 minutes.

As a result, the metals and slag shown in Table 4 were each 91
ky, gained 159ky.

As shown in the above examples, according to the method of the present invention, Ca-based alloys can be obtained extremely easily and inexpensively even on an industrial scale, and the technical and economical effects of the method of the present invention are extremely large. It is.

[Brief explanation of the drawing]

The figure is a graph showing the relationship between the Al blending ratio and the Ca content in the produced alloy.

Claims (1)

[Scope of Claims] 1. When reducing calcium oxide with molten aluminum, the blending ratio of the molten aluminum to calcium oxide is 0.5 to 30% of the stoichiometric amount that satisfies the following formula.
Double, 3 Ca O+ 2 A l → 3 Ca + A 12
03 and within a temperature range of 1350 to 1800°C,
A method for producing a calcium-based alloy, characterized in that the reduced calcium is obtained as a molten alloy with aluminum. 2. When reducing calcium oxide with molten aluminum, the blending ratio of the molten aluminum to calcium oxide is 0.5 to 30% of the stoichiometric amount that satisfies the following formula.
double, and in the presence of an additive element for specific gravity adjustment consisting of one or more metals or alloys of iron, chromium, manganese, and nickel, and carried out within a temperature range of 1350 to 1800°C, and the reduced A method for producing a calcium-based alloy, characterized in that calcium is obtained as a molten alloy with the additive element for adjusting specific gravity and aluminum.