KR20070094837A - Non-sodium flux and processing method of aluminum alloy molten metal using same - Google Patents

Abstract

When treating aluminum alloy melt using non-sodium flux with flux injection rotary degassing apparatus, non-sodium flux and aluminum alloy melt using the same to prevent deposition and deposition of unreacted flux and secure high degassing effect Provide a treatment method. % By mass AlF ₃ : 80-95%, KCl: 2.5-10%, K ₂ SO ₄ : Non-sodium flux consisting of 2.5 to 10% of essential constituents and the balance of 5% or less of other chlorides, fluorides and nitrates in total. The rotor of the apparatus is kept immersed in the aluminum alloy molten metal, the inert gas and the above-mentioned flux are blown into the molten metal from the nozzle, supplied, the rotor is rotated at 200 to 450 rpm, and the inclusions in the molten metal are subjected to fine bubbles and flux. A method of treating an aluminum alloy which performs degassing and ash removal by flotation to the hot water surface.

Description

SODIUM-FREE FLUX AND PROCESS FOR TREATMENT OF MOLTEN ALUMINUM ALLOY WITH THE SAME}

The present invention relates to a method for treating molten aluminum, and more particularly, to a method for treating molten aluminum using a flux injection rotary degassing apparatus.

As a process Si improving agent for casting alloys, Na has been used for a long time, and Na-based fluxes containing NaF and NaCl as main components have been widely used as fluxes for Na addition.

However, although Na has an effect of promoting the dispersion of gas pores in aluminum castings, depending on the alloy composition and casting method, molten metal containing Na of several PPM or more is reacted with hydrogen in the air. The gas concentration tends to be high, and the oxidation on the molten metal surface is promoted, thereby generating dross. In addition, in the 5000 series aluminum alloy containing Mg as a main alloy component, it is also known that a trace amount of Na causes grain boundary brittleness and significantly deteriorates its properties such as elongation.

Thus, in the casting system line which is reluctant to mix Na, non-sodium flux has been widely used as a flux for the removal of aluminum alloy molten metal. Among these non-sodium fluxes, KAlF ₃ , AlF ₃ , and K ₂ which have a chloride-based flux containing no Na salt such as MgCl ₂ , CaCl _2, or KCl which have a degreasing effect as a main component and increase the reactivity with the molten aluminum therein. SO ₄ Etc. are mixed.

However, in the chloride flux, MgCl ₂ , CaCl ₂ is hygroscopic, so care must be taken in storage. If the absorbed flux is in direct contact with the molten aluminum, there is a risk of water vapor explosion, so it is better to avoid the use of MgCl ₂ , CaCl ₂ if possible. In addition, since MgCl ₂ and CaCl ₂ are reacted with an aluminum alloy molten metal, they are not widely used except in the case of use in a closed furnace such as a batch furnace because they cause malodor and impair workability.

Therefore, in the casting system line which is reluctant to mix Na, KAlF ₃ , AlF ₃ , K ₂ SO ₄ , which is a flux for de-melting treatment of molten metal, has KCl having a de-oiling effect as a main component and increases reactivity with the molten metal. Non-sodium flux mixed with such materials, for example KK765 (manufactured by Nippon Light Metal Co., Ltd. (trade name), mass%, 60% KCl, 15% KAlF ₃ , 15% AlF ₃ , 10% K ₂ SO ₄ ) has been developed and widely used. Has been used.

By the way, the rotational degassing apparatus is known for a long time as a processing apparatus which promotes degassing and degassing | melting of aluminum alloy molten metal. This is a rotary degassing apparatus having a nozzle capable of supplying an inert gas to the center of a rotating rotor shaft, while injecting an inert gas such as argon or nitrogen into the molten metal from the nozzle while the rotary rotor is immersed in an aluminum alloy molten metal. The rotary rotor is rotated at a rotational speed of 200 to 650 rpm to float the inclusions in the molten metal together with the microbubbles to the hot water surface, and degassing in parallel with the degassing (Japanese Patent Laid-Open No. 7-207373).

On the other hand, recently, in this rotary degassing apparatus, the apparatus which has one or more nozzles which can supply an inert gas and a flux to the center of a rotating rotor shaft is developed (US Pat. No. 6,375,712).

By using this flux injection rotary degassing apparatus, it has become possible to heighten the said degassing effect further, suppressing generation | occurrence | production of harmful gas, such as chlorine which arises from the flux scattered in the molten metal as much as possible.

However, when the present inventors conducted the test and carried out the melt treatment using the non-sodium flux in the flux injection rotary degassing apparatus, when the KCl, which is the main component of the flux, was discharged from the nozzle near the rotating rotor, it did not melt and salt. Instead, it has been found that a problem arises that the unreacted flux adheres and deposits near the nozzle.

The present invention solves the problems of the prior art, and when the aluminum alloy molten metal is treated using a non-sodium flux by a flux injection rotary degassing apparatus, it prevents the adhesion and deposition of the unreacted flux and provides a high degassing effect. It is an object of the present invention to provide a method for treating a non-sodium flux secured and an aluminum alloy molten metal using the same.

In order to achieve the above object, according to the present invention, it is a non-sodium flux used for treating an aluminum alloy molten metal by a flux injection rotary degassing apparatus, and in mass%, AlF ₃ : 80 to 95%, KCl: 2.5 to 10%, K ₂ SO ₄ : Non-sodium flux provided with 2.5-10% as an essential component and remainder consisting of 5% or less of other chlorides, fluorides, and nitrates in total.

In addition, a flux injection rotary degassing apparatus having one or a plurality of nozzles capable of supplying an inert gas and flux to the center of a rotating rotor shaft is a method of treating molten aluminum alloy using the non-sodium flux of the present invention. ,

The rotary rotor is immersed in the aluminum alloy molten metal,

The inert gas and the flux are blown out from the nozzle into the molten metal, and the rotary rotor is rotated at a rotational speed of 200 to 450 rpm. The inclusions in the molten metal are floated together with the fine bubbles and the flux to the hot water surface to remove degassing and ash. There is provided an aluminum alloy molten metal treatment method.

In addition, a flux injection rotary degassing apparatus having one or a plurality of nozzles capable of supplying an inert gas and flux to the center of a rotating rotor shaft is a method of treating molten aluminum alloy using the non-sodium flux of the present invention.

The rotary rotor is immersed in the aluminum alloy molten metal,

Inert gas and the flux are blown out from the nozzle into the molten metal, and the rotary rotor is rotated at a rotational speed of 200 to 450 rpm to degas and degreaser by floating the inclusions in the molten metal together with the fine bubbles and the flux to the hot water surface. The first step,

In addition, the inert gas is blown out from the nozzle into the molten metal and supplied, and the rotating rotor is rotated at a rotational speed of 200 to 450 rpm to lift the inclusions in the molten metal together with the fine bubbles and the residual flux to the hot water surface to perform degassing and degassing. Provided is an aluminum alloy molten metal treatment method, in which two steps are performed in sequence to perform degassing and deaeration.

The non-sodium flux of the present invention is AlF _{3 in} mass% from the nozzle of the flux injection rotary degassing apparatus. : 80 to 95%, KCl: 2.5 to 10%, K ₂ SO ₄ : Since it has a composition from other chlorides, fluorides, and nitrates of 2.5 to 10% and the total of 5% or less of the remainder, KCl can be melted and chlorided by the heat of reaction of K ₂ SO ₄ and the melt, and the reaction between AlF ₃ and the melt is performed. This makes it possible to smoothly disperse the flux into the molten metal, thereby significantly improving the degreaser effect.

With the development of this non-sodium flux (fluoride flux), it becomes possible to perform uniform dispersion of flux into aluminum molten metal by a flux injection rotary degassing apparatus and high efficiency ash removal treatment. At the same time, even if the amount of flux used is suppressed as much as possible, it was possible to establish a method for treating low-pollution aluminum molten aluminum that can maintain a high degassing effect.

As a result of examining the above-mentioned conventional problem, the present inventors have found that the non-sodium flux contains 60% of KCl in KK765, but the KCl has a relatively high melting point and does not immediately melt-melt even when it comes into contact with the molten metal. In addition, since only 15% of AlF ₃ having good reactivity with the molten metal is contained, the flux is not smoothly dispersed in the molten metal, and the unreacted flux is deposited near the nozzle, which significantly inhibits the degreasing effect. It was estimated.

As a result of repeated experiments from this point of view, it was found that in order to prevent deposition of unreacted flux near the nozzle, it is necessary to (1) melt-chloride chloride chloride and (2) increase the reactivity of the flux and the molten metal. .

And, in order to melt chloride to (1) a chloride flux in order to realize them, to contain the reaction heat with the high K ₂ SO ₄ with molten aluminum a suitable amount, (2) to disperse the molten chloride flux into the molten metal, aluminum It was concluded that it is necessary to have AlF ₃ having high reactivity with molten metal as a main component.

[Reason of flux composition]

<AlF ₃ : 80-95 mass%>

AlF _{3 which} is a main component in the flux of the present invention reacts with the molten aluminum to have an effect of promoting the dispersion of the flux into the molten metal. When the mixing ratio of AlF ₃ is less than 80%, the flux adheres and deposits in the vicinity of the nozzle of the rotary rotor, and dispersion of the flux into the aluminum alloy molten metal is not performed smoothly, thus preventing the above-mentioned degassing effect. When the composition ratio of AlF ₃ exceeds 95%, the flux is dispersed in the molten metal by the reaction of the flux with the molten aluminum, so that the flux does not adhere near the nozzle of the rotating rotor, but the flux itself Disinfection ability is significantly lowered. Therefore, the preferable mixing ratio of AlF ₃ is 80 to 95% of range.

<KCl: 2.5 to 10% by mass>

KCl, which is an essential component in the flux of the present invention, is finely dispersed in the molten aluminum to gradually float as a fine molten salt and float on the hot water surface with inclusions or the like, thereby remarkably increasing the degassing effect. When the composition ratio of KCl is less than 2.5%, the flux removal effect is remarkably inferior. When the composition ratio of KCl exceeds 10%, the composition ratio of AlF ₃ decreases with this, so that unreacted flux adheres and deposits near the nozzle of the rotating rotor, and the flux is smoothly dispersed in the molten aluminum alloy. It is not done so, and the said degrease effect is inhibited. Therefore, the mixing ratio of preferable KCl is 2.5 to 10% of range.

<K ₂ SO ₄ : 2.5 to 10% by mass>

K ₂ SO _{4, which} is an essential component in the flux of the present invention, acts as a reaction accelerator between the molten aluminum and the flux. When K ₂ SO ₄ and the molten aluminum react, a reaction such as K ₂ SO ₄ + Al → AlSO ₄ + K proceeds, and a large amount of heat of reaction is generated. By this reaction heat, KCl is easily melted and salted, and the above-mentioned degreasing effect can be enhanced. When the composition ratio of K ₂ SO ₄ is less than 2.5%, melt chloride salt of KCl is insufficient, and the flux is adhered and deposited in the vicinity of the nozzle of the rotary rotor. When the composition ratio of K ₂ SO ₄ exceeds 10%, an exothermic reaction between the flux and the molten aluminum occurs, melting and salting of KCl is promoted, and the flux does not adhere and deposit near the nozzle of the rotating rotor, A dross is burned violently by an exothermic reaction, producing smoke, which deteriorates the working environment. Therefore, the mixing ratio of preferable K ₂ SO ₄ is in the range of 2.5% to 10%.

<Other chlorides, fluorides, nitrates: 5% by mass or less in total>

In addition to flux, one or more specified components of the present invention, the total is within the range of not more than 5% by weight, the chloride other than KCl, AlF ₃ Other fluorides or nitrates may be contained. These chlorides, fluorides, and nitrates are typically the following.

Chlorides other than KCl: NaCl, CaCl ₂ , MgCl ₂

AlF ₃ Other Fluoride: NaF, KF, MgF ₂ , CaF ₂

Nitrate: KNO ₃ , NaNO ₃

When the total amount exceeds 5% by mass, NaCl is mixed in the molten metal with respect to NaCl, CaCl ₂ and MgCl ₂ are accompanied by hygroscopicity, and fluorides and nitrates such as NaF increase flux deposition.

Therefore, other chlorides, fluorides, and nitrates are 5 mass% or less in total.

<Example>

[Evaluation test of adhesion and deposition of flux]

Using the flux of the composition within and outside the range of this invention, the aluminum alloy molten metal was processed with the flux injection rotary degassing apparatus, and the adhesion and deposition of the flux to the lower part of the rotor were evaluated.

Table 1 shows the composition of the fluxes used. Flux A and B are the invention examples which have a composition within this invention range, and flux C-I are the comparative examples which have a composition outside this invention range.

Table 1 Composition (mass%) of each flux

Flux KAlF ₄ AlF ₃ KCl K ₂ SO ₄ MgCl ₂ Inventive Example A - 80 10 10 - B - 90 5 5 -  Comparative example C 100 - - - - D 70 - 20 10 - E - 100 - - - F 10 7 78 5 - G 15 15 60 10 - H - - 70 - 30 I - 70 20 10 -

In the state where 230 kg of AC4C alloy molten metal was hold | maintained at 740 degreeC in the holding furnace, the molten metal process was performed by the flux injection rotary degassing apparatus by 1-way rotation of 30000 rpm. As a first step, the flux of a predetermined composition at a supply amount of 40 g / min and N ₂ at a flow rate of 30 L / min The gas was simultaneously supplied from the nozzle, and the flux treatment for uniformly dispersing the flux in the molten metal was performed for 5 minutes. As the second step, only the flux was supplied while the rotor was continuously rotated, and only N ₂ gas was supplied from the nozzle at a flow rate of 30 L / min to perform degassing treatment for 10 minutes.

After the melt treatment, the rotor was pulled out of the melt and the deposition length of the flux adhering to the lower rotor around the nozzle was measured. Table 2 summarizes the deposition determination results for each flux.

            Table 2 Sedimentation Evaluation for Each Flux

Flux Flux deposition Deposit amount (* 1) (mm) Judgment (* 2) Inventive Example A 0 ~ 1 ○ B 0 ~ 1 ○  Comparative example C 30 × D 20 × E 0 ◎ F 50 × G 30 × H 10 △ I 10 △

(week)

(* 1) Lower rotor

(* 2) Judgment standard

Deposit amount (mm) Judgment 0 ◎ best 0 ~ 1 ○ good 1-10 △ allowance > 10 × bad

[Evaluation test of the flux removal effect of the flux]

Similarly, in order to evaluate the degreaser effect using the flux of the composition shown in Table 1, degassing experiment was performed without using the flux injection rotary degassing apparatus, and the cleanliness of the molten metal before and after a flux process was measured.

With 7 kg of AC4C alloy molten metal held at 740 ° C in a # 30 persimmon, one kind of flux shown in Table 1 was wrapped in 14 g (0.2 wt%) aluminum foil and pushed into the molten metal with a hose sprayer.

As inclusion evaluation, K mold sampling (n = 3) was performed before and after the flux treatment. The injected thin board | substrate shape (5 mm thickness x 40 mm width) sample was pounded with a hammer, and it was set as six fracture pieces. A total of 12 wavefronts were visually observed for all six, and the number of foreign matters such as inclusions and oxides was counted, and K value = number of foreign matters / 6 was calculated. Reduction ratio = (K0-Kl) / K0 was computed by making K value before a flux process into K0 and K value after a flux process as K1, and the degassing effect of the flux was evaluated based on this reduction rate. Table 3 summarizes the evaluation results of the degreaser effect for each flux.

Table 3 Effects of ash removal of each flux

Flux K0 = K value before processing K1 = K value after treatment (K0-K1) / K0 = stripping effect Judgment(*) Inventive Example A 6.1 0.4 0.93 ○ B 2.8 0.2 0.93 ○  Comparative example C 5.1 0.9 0.82 △ D 4.8 0.4 0.92 ○ E 4.5 1.1 0.76 × F 3.2 0.2 0.94 ○ G 3.8 0.05 0.99 ◎ H 4.2 0.5 0.88 △ I 3.8 0.2 0.95 ○

Criterion of note (*) stripping effect of Table 3

(K0-K1) / K0: Degrease effect Judgment > 0.95 ◎ best 0.90-0.95 ○ good 0.80-0.89 △ allowance <0.80 × bad

Table 4 shows the comprehensive evaluation based on the results of the above-described deposition evaluation and evaluation test.

Table 4 Integration Decision of Each Flux

Flux Judgment Sedimentation evaluation Disinfection effect integrated(*) Inventive Example A ○ ○ ○ B ○ ○ ○  Comparative example C × △ × D × ○ × E ◎ × × F × ○ × G × ◎ × H △ △ △ I △ ○ △

(*) The integrated judgment was made into the lower judgment level among the deposition evaluation and the removal effect.

(◎ best, ○ good, △ acceptable, × bad)

The details of the integrated evaluation were as follows.

Invention example flux A and B, the composition in the specified range of the present invention, since containing AlF ₃ 80 to 95%, by the AlF ₃ promotes the dispersion of the molten metal into the flux, a flux adhering to the rotor is substantially Does not happen. In addition, since KCl and K ₂ SO ₄ are appropriately contained, KCl is melted and salted by the exothermic reaction between K ₂ SO ₄ and the molten aluminum, so that the degrease effect is also good.

Flux C (comparative example) is a composition of 100% KAlF ₃ , and the reactivity with aluminum is very low compared to AlF ₃ , so that no flux dispersion occurs in the molten metal, and a large amount of flux adheres to and is deposited on the rotor. In addition, the degassing effect of KAlF ₃ is not good.

Flux D (Comparative Example) contains each component of KAlF ₄ , KCl, K ₂ SO ₄ , and has a good degreasing effect, but does not contain AlF ₃ , so that flux dispersion in the molten metal does not occur, so that a large amount is added to the rotor. Flux is attached and deposited.

Flux E (Comparative Example) is a component of 100% AlF ₃ and has a high reactivity with aluminum and facilitates flux dispersion in the molten metal, but has no other components and hardly has a degreaser effect.

Flux F and G (Comparative Examples) contain KAlF ₄ , AlF ₃ , KCl, and K ₂ SO ₄ , and have a good degreasing effect, but have a low AlF ₃ content and do not disperse flux in the molten metal. Therefore, a large amount of flux adheres and deposits on the rotor.

Flux H (Comparative Example) has KCI and MgCl ₂ , but does not contain K ₂ SO ₄ , so that exothermic reaction with aluminum molten metal does not occur and does not have a degreasing effect. Since AlF ₃ is not contained as such, flux dispersion in the molten metal does not occur, and flux adheres and deposits on the rotor.

Flux I (comparative example) has KCl and K ₂ SO ₄ , each having a good degreasing effect, but the AlF ₃ content is slightly low, and flux dispersion in the molten metal does not sufficiently occur, and flux adheres to the rotor. To be deposited.

In summary, among the used fluxes, the AlF ₃ content is lower than the prescribed range of the present invention, and fluxes exhibiting a tendency to adhere to and deposit on the lower part of the rotor, even though they have the original degreasing effect, cannot exhibit the degreasing effect for flux injection. . Flux containing AlF ₃ in an amount within the scope of the present invention and containing KCl and K ₂ SO ₄ in an amount within the scope of the present invention and having a degreaser effect are suitable as a flux for a flux injection rotary degassing apparatus.

According to the present invention, when treating aluminum alloy molten metal using a non-sodium flux by a flux injection rotary degassing apparatus, a non-sodium flux which prevents the occurrence of deposition and deposition of unreacted flux and secures a high degassing effect And a method of treating an aluminum alloy molten metal using the same.

Claims (3)

Flux injection Non-sodium flux used for treating aluminum alloy molten metal by rotary degassing apparatus, in mass%, AlF ₃ : 80 to 95%, KCl: 2.5 to 10%, K ₂ SO ₄ : 2.5 to 10% Is an essential component, and the remainder is a non-sodium flux, characterized in that the total consists of 5% or less of other chlorides, fluorides, and nitrates. A flux injection rotary degassing apparatus having one or a plurality of nozzles capable of supplying inert gas and flux to a central portion of a rotating rotor shaft, wherein the flux of claim 1 is used to treat aluminum alloy molten metal. The rotary rotor is immersed in the aluminum alloy molten metal, The inert gas and the flux are blown out from the nozzle into the molten metal, and the rotary rotor is rotated at a rotational speed of 200 to 450 rpm. An aluminum alloy molten metal processing method characterized by the above-mentioned. A flux injection rotary degassing apparatus having one or a plurality of nozzles capable of supplying inert gas and flux to a central portion of a rotating rotor shaft, wherein the flux of claim 1 is used to treat aluminum alloy molten metal. The rotary rotor is immersed in the aluminum alloy molten metal, Inert gas and the flux are blown out from the nozzle into the molten metal, and the rotary rotor is rotated at a rotational speed of 200 to 450 rpm to degas and degreaser by floating the inclusions in the molten metal together with the fine bubbles and the flux to the hot water surface. The first step, In addition, only the inert gas is blown out from the nozzle into the molten metal and supplied, and the rotating rotor is rotated at a rotational speed of 200 to 450 rpm to lift the inclusions in the molten metal together with the fine bubbles and the residual flux to the hot water surface to perform degassing and degassing. 2 processes are performed in order, and degassing and ash removal are performed, The aluminum alloy molten metal processing method characterized by the above-mentioned.