The method of refining magnesium slag containing metallic magnesium chloride salt and magnesium oxide

 

(57) Abstract:

The invention relates to foundry and can be used to obtain magniysoderzhaschee ligatures magnesium slag containing metallic magnesium chloride salt and magnesium oxide, and its application in the production of castings from nodular cast iron. The essence of the invention that prepare special melt on the basis of silicon and / or copper; keep the temperature of the melt at its connection with the slag in the range between the melting point of chloride salts and temperature evaporation; fill the space, which connects the melt and magnesium slag, protective gas; connect melt and magnesium slag. The method allows for the processing of magnesium slag with a significant economic effect by combining the extraction of magnesium from magnesium slag and preparation of ligatures for the production of castings from nodular cast iron. 3 C.p. f-crystals, 4 tab., 1 Il.

The invention relates to foundry and can be used to obtain magniysoderzhaschee master alloys of silicon and / or copper and dissolved in them of magnesium from magnesium slag containing metal is SAI from nodular cast iron.

Currently, the enterprises producing castings of magnesium alloys by casting under pressure, is a very urgent problem processing the resultant magnesium slag containing chloride salts. So, on one of the famous enterprises magnesium toxins already accumulated several hundred tons. The waste products of this company have the composition shown in table. 1.

Magnesium-containing slag formed in the process of melting of the charge in the electric furnace CAT-0,15 due to oxidation of the magnesium and particles of magnesium oxide on the bottom of the crucible in the refining sludge finished alloy flux of chloride salts.

The number used for a heat flux is 2.8 to 3.0% by weight of the alloy in the furnace. Magnesium-containing slag formed at the bottom of the crucible, extract through the column of liquid alloy. It is a conglomerate confused magnesium alloy in fluvoamine mixture and structurally consists of a frame (skeleton) magnesium alloy, as well as small and large inclusions fluvoamine mixture, which may be the inclusion of metal particles of various sizes.

SCEP does not allow you to remove these waste products for disposal, in particular, due to the high content of the W ill result of practical implementation for a number of reasons.

In table. 2 presents technical solutions for processing magnesium slag selected as analogues.

The technical nature of the prototype should adopt the method which consists in fusing aluminum alloy surfaces, the flux and the introduction of waste magnesium below the level of the melt having a temperature of 660-720oC (M. B. Altman and other Smelting and casting of light alloys. M., "metallurgy", 1960, S. 317).

The purpose of the invention consists in the dissolution of magnesium from magnesium slag containing metallic magnesium chloride salt and the magnesium oxide in the molten metal on the basis of silicon and / or copper with getting alloys for the production of castings from nodular cast iron.

The proposed method of refining magnesium slag containing metallic magnesium chloride salt and magnesium oxide, with getting alloys for the production of castings from nodular cast iron includes:

preparing a melt of metals on the basis of silicon and / or copper;

maintaining the melt temperature in connection with the magnesium slag in the range between the maximum melting temperature chloride salts and minimum temperature of boiling;

filling the space in which zoetica, containing metallic magnesium chloride salt and magnesium oxide.

The main difference of the proposed method from the prototype is that, first, the melt are not based on aluminum and silicon and / or copper, secondly, the temperature of the melt in connection with the slag maintained within the range between the maximum melting temperature chloride salts (960oC) and minimum temperature of boiling (1413oC) thirdly, in the space in which it connects the melt and magnesium slag, serves a protective gas, in particular nitrogen.

The first two factors are essential. It is their combination allows the processing of magnesium slag containing metallic magnesium chloride salt and magnesium oxide, with getting alloys for the production of castings made of cast iron with spherical graphite.

The silicon and / or copper, on the basis of which prepare the melt, well dissolve the magnesium and not reduce casting and mechanical properties of cast iron, and, conversely, have to cast a positive modifier and alloying effects. Aluminum as the basis for the preparation of the melt and get ligatures for modifying conventional cast irons cannot be CLASS="ptx2">

It is of fundamental importance and maintaining the melt temperature at the time of its connection with the slag in the range between the maximum melting temperature chloride salts and minimum temperature of boiling. Maintaining the melt temperature above the maximum temperature of molten chloride salts (960oC) contributes to the rapid melting of the chloride salts and the establishment of direct contact between the melt and magnesium, found in the slag, and accelerate its dissolution in silicon and / or copper. The temperature of the melt below the minimum boiling point of the chloride salts (1413oC) reduces the bubbling, emissions melt and smoke atmosphere melting site.

The connection of the melt and slag at a temperature below the maximum boiling point of the chloride salts reach at the expense of putting in a silicon and / or copper other elements that lower the melting temperature (solidification) of the melt. For example, typing in copper 8-10% of Si lowers the melting temperature (solidification) 1089oC (copper) up to 875oC and enables the connection of the melt and magnesium slag at a temperature of 960oC and above. Enter in the silicon 40-50% of iron reduces the melting temperature (zi temperatures below the minimum boiling point of the chloride salts at a temperature of 1300-1400oC. in Addition, iron and copper perform another important function of the weight of the melt, resulting in accelerated floating (Department) fluvoamine mixture. Of course, the most preferred is the junction temperature of the melt and slag in the range between the melting point of chloride salts (960oC) and a boiling point of magnesium (1120oC). In this case, by eliminating the boiling point of magnesium is even more reduced proeffect and bubbling. Specified practically possible to implement when using molten copper based, in particular, with silicon content of 6 to 12% and, unfortunately, not possible with molten silicon-based. For this reason, the molten copper-based preferred, but because of the high price of copper compared with the silicon master alloys of copper is about twice as expensive alloys based on silicon. Master alloys of copper is economically feasible to use to produce castings of iron, which must be alloyed with copper. For plain cast iron is economically more preferred is the use of alloys based on silicon. In this case we have to make the connection the CSOs gas, in particular nitrogen, in the space in which it connects the melt and magnesium slag increases the absorption of magnesium from the magnesium slag reduces proeffect and size of the smoke emission.

The description is deliberately used the expression "the connection of the melt and magnesium slag" instead of, for example, the expression "input magnesium slag in the melt". This is because the connection of the melt and magnesium slag can be input magnesium slag in the melt in the furnace, the ladle, different capacity), or by filling the melt vessel (crucible furnace, ladle, mold, etc.,) located therein magnesium slag. The choice of the manner of connection of the melt and magnesium slag depends on a number of factors: in particular, the existing type melting furnace, the requirements of the ligature, in particular, on the number and limits of the content of magnesium; other possibilities and specific conditions in the foundry.

For example, in the preparation of the melt in the electric arc furnace and a relatively low content of magnesium in the alloy (up to 5-7%) more acceptable it may be pouring the melt onto a solid magnesium slag, located in the bucket or other special containers. Thus, space in the ladle or other emonster this method of connection can be attributed to the mobility and performance; among the disadvantages is the difficulty of obtaining ligatures with strictly defined content in magnesium due to possible variations in the magnesium content in the slag.

At relatively high content in alloys of magnesium (10-15%), the narrow limits to the variation in the content of magnesium in the alloy and available in the shop induction furnace will be more acceptable input solid magnesium slag in the melt directly in the furnace, for example, using the bells. The advantage of this method is the possibility of obtaining ligatures with the required content of magnesium; the disadvantage is the need for the bells. In this case, after carrying out the Express-analysis of magnesium and in the presence of deviations magnesium content from the set have the opportunity to enter additional estimated amount of the magnesium slag on the basis of data analysis. Before entering an additional amount of magnesium slag melt, as a rule, you will need to warm up.

If the production site of two or more melting furnaces can be implemented in connection magnesium slag and molten silicon and / or copper by pouring the melt of the magnesium slag, in which magnesium metal is in the molten state (mainly meidrim magnesium magnesium is dissolved in the silicon and / or copper, and chloride salts and magnesium oxide surface melt ligatures due to the significant difference in density of the melt and flysolo oxide mixture. As advantages of this method of connection of the melt and magnesium slag may be noted the possibility of using molten silicon and / or copper with lower temperature; the disadvantage is the need to have two melting furnaces.

Below are examples of the proposed method and the results obtained here.

Example 1. The graphite crucible was set in printed crucible of EAST-0.16 and melted 5 kilograms of copper, is then introduced into the melt of 0.5 kilogram of silicon. Enter silicon was carried out to reduce the melting temperature (solidification) of the melt. After dissolution of silicon at the temperature of the melt 1000oC above the crucible furnace has set a cap with a threaded through hole cap barbell bell. The bell was 0.4 kg of magnesium slag containing about 45% magnesium. From the container by a flexible hose under the hood filed nitrogen and introduced the bell in the melt. After the shake bell, which indicates the completion of the dissolution of magnesium, has cut off supplies of nitrogen and extracted the bell race is or hat with bell filed nitrogen, introduced into the melt of 0.4 kg of magnesium slag, has cut off supplies of nitrogen, removed the bell and the cap. Again removed from the surface of the molten slag, has set a cap with a bell, filed nitrogen and at a temperature of 940oC introduced 0,3 kg slag, removed the bell and the cap. In the latter case, about a quarter entered magnesium slag was unreacted low temperature of the melt is not allowed to melt chloride salts and this has hindered the process of dissolution of magnesium from magnesium slag. Fueled by the melt up to 950oC, took off the slag from the surface of the melt and pouring the molten alloy into the mold.

The resulting alloy composition, %:

Cu - 80

Mg - 7,5

Si - 9,2

Al - 0,9

Zn - 0,4

Fe - Rest

tried to modify cast iron.

The chemical composition of the cast iron after inoculation, %:

C - 3,4

Si - 2,95

Mn - 0,28

P - 0,12

Cr - 0,03

Cu - 1,32

Al - 0,05

S - 0,05

Zn - < 0,005

In table. 3 illustrates the properties of cast iron, the modified received by the ligature.

In table. 4 shows a comparison of the properties of cast iron, obtained by modifying a ligature made by the proposed method and cast iron according to GOST 7293-85 (respectively the respective brands see GOST 7293-85.

Analysis of the results shows that the proposed method for the processing of slag in the molten copper with getting this magniysoderzhaschee ligature is feasible, and the ligature can be used to produce castings of nodular form of graphite. Pictures of microstructures obtained irons shown in the drawing.

Example 2. In the furnace EAST 0,16 has napravila 50 pounds of alloy composition 60% silica and 40% iron. The main function of iron - lowering the melting temperature of the melt (1423oC to 1200-1220oC). Above the crucible furnace has set a cap with a threaded through hole cap barbell bell. The bell was 8 kilograms of magnesium slag containing about 50% magnesium. From the container by a flexible hose under the cover of the applied nitrogen. 10 seconds after the start of supply of nitrogen in the melt at a temperature of 1380oC introduced the bell with magnesium slag. After the dissolution of magnesium from the slag, as evidenced by the cessation of the vibration of the bells, the flow of nitrogen was stopped. Pulled from the melt bell. Removed the cap with a bell from the crucible furnace. Took off the slag from the surface of the melt. Conducted a rapid analysis of the melt on the content of mA the number of magnesium slag (QWin kg, which must be entered to access the desired content of magnesium in the ligature. The calculation was made according to the formula

QW= PW(Ct- Ca)(1 + Cand:100): Cand,

where PW- the amount introduced into the melt of magnesium slag, kg;

Ctrequired content of magnesium in the ligature, %;

Candthe content of magnesium in the melt according to the Express-analysis, %.

Placed in the bell of the estimated amount of the magnesium slag:

8 (9,25-7,5)(1+0,075);7,5=2 kg

Fueled by the melt to a temperature of 1350oC. Pushed through the hole in the cap barbell bell has set a cap with a bell above the crucible furnace filed nitrogen in the space above the melt and put the bell in the melt. After the dissolution of the magnesium slag blocked the flow of nitrogen, removed from the melt bell, removed the cap with a bell, took off the slag from the surface of the melt, has released the resulting melt ligatures in the ladle and poured it into the moulds.

Analysis ligatures showed the following composition:

Mg = 9,1%; Si = 55%; Al = 0,5%; Zn = 0,1%; Fe - rest.

The proposed method allows to process magnesium slag with a significant economic effect due to the combination process is dnim graphite.

Industrial use of the proposed method will allow us to solve not only a purely economic problem in the production of alloys on the basis extracted from the slag magnesium, but will help to solve environmental problems resulting from the removal of magnesium from the slag and reduce the amount of slag by 30-40% compared with the initial volume.

LITERATURE

1. Table of physical quantities. The Handbook. Ed. by Acad. I. K. Of Ciconia. M, Atomizdat, 1976, 1008 S.

2. Concise encyclopedia of chemical in five volumes. Moscow, 1961. Publishing house "Soviet encyclopedia". Volume 1, 378.

1. The method of refining magnesium slag containing metallic magnesium chloride salt and magnesium oxide, including the preparation of the metal melt and the connection of the melt metals and magnesium slag, characterized in that as the basis of the melt using silicon and/or copper, the temperature of the melt at its connection with the slag support within higher maximum temperature melting chloride salts, equal to 960oC, and below the minimum temperature of boiling equal 1413oC.

2. The method according to p. 1, characterized in that the space in which it connects the melt and magnesium slag, serves sah">

4. The method according to p. 1, characterized in that the melt temperature for alloys of copper-based support above the melting temperature of chloride salts is equal to 960oC, and below the boiling point of magnesium equal to 1120oC.

 

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