SU777069A1 - Slag-producing mixture for treatment of cast iron and steel - Google Patents

Description

Magnesite 10-25

Waste slag from the production of alloys with rare earth metals 15 -: 40 For example, ferrosilicon, silicocalcium, silicoaluminium, silicomagnesium can be used as a silicon-containing alloy. If additional alloying is necessary, such elements as chromium, vanadium, manganese, etc. can be used. Silicon-containing alloys of the corresponding elements can be used.

As a material containing halides, for example, fluorspar, fluorite, fluorite concentrate, cryolite, chiolite, potassium or potassium salt, calcium chloride can be used.

As oxidizing agents (oxygen suppliers), for example, alkaline salts of nitric acid (sodium or potassium nitrate), manganese ore, iron ore, mill scale can be used. One or more oxidizing agents may be added to the mixture.

Waste slag from the production of alloys with rare-earth metals contains the following oxides, wt. % Rare earth oxides

elements 5-20

Aluminum oxide 30-55

Calcium Oxide 15-45

Silica 2-10

Magnesium oxide 0.5-10

In addition, there can be impurities in the slag — carbon, sulfur, oxides of iron, manganese, chromium, vanadium, titanium, etc. — in a total amount of not more than 5%.

In the mixture, magnesite is introduced to partially neutralize the nitrogen of the steel and reduce its transition to the metal.

Aluminum in the mixture is the main combustible material of the metallothermic process that occurs when using the mixture.

The oxidizing agents are the supplier of oxygen for such a process, the silicon-containing component of the mixture serves as a carrier of rare-earth elements in the metal being treated, and the material containing halides is used as a thinning agent.

The mixture can be used to process steel or cast iron in a furnace, ladle, mold, in a mold, as well as in an intermediate ladle or crystallizer during continuous casting of steel. Treatment of the metal with the mixture can be carried out by addition of the mixture in a container (for example, in paper bags) or in bulk to the bottom of the ladle or mold, to the metal surface, to the metal stream when it is discharged from the furnace, during casting, from one container to another. With

this amount of the mixture for metal processing is determined, depending on the conditions of its input and the desired effect of desulfurization and micro-alloying and is 2-70 kg per ton of metal.

From materials containing halides, materials containing 45–60 wt. % fluorine or chlorine. Halides lower the temperature

melting the slag-forming mixture and the viscosity of the resulting slags, with fluorides being more efficient than chlorides. However, the lower diluting effect of chlorides is compensated by a large amount of

chlorine in the components of the mixture compared with the amount of fluoride. For example, calcium fluoride contains 45% fluorine and calcium chloride contains 65% chlorine, therefore fluorides can be replaced by chlorides in the 1: 1 ratio, as shown in examples 1 and 3.

The maximum content of halogenides is selected to guarantee the safety of service personnel during steel casting. When the concentration of halides is 10%, there is still no noticeable release of fluorine or chlorine from the mixture. The minimum content of fluoride or chloride - 5%

due to the fact that with a lower content in the mixture, they have insufficient effect on the shlak.

Cryolite and chiolite lower the melting point of the mixture and the viscosity of slags more than, for example, fluorspar or fluorite. Its content in the mixture can be reduced by about 1.5 times. The lower limit of the concentration of these materials can be taken 3%, the top 10%.

Silicon in the mixture serves as a carrier of rare-earth metals, and one of the above-mentioned alloys containing 45–75% silicon can be used as a silicon-containing alloy. Moreover, when using alloys that are less silicon-rich, they should be introduced into the mixture in an amount close to the upper limit, and when using more silicon-rich alloys, their number can be reduced. The use of alloys containing more than 75% silicon is not recommended due to their strong hygroscopicity, as well as the possible saturation of the mixture with moisture and metal with hydrogen.

Thus, alloys containing 45–75% silicon are introduced into the mixture in an amount of 8–20 wt. %

The mixture is prepared by mixing pre-ground components.

Silicon-containing alloy and aluminum

add to the mixture last.

Recommended fractional composition of the mixture

up to 5 mm, humidity up to 0.5%.

For the preparation of mixtures used

following materials:

Aluminum powder PA-1 (GOST 6058-73)

75% ferrosilicon

Silicocalcium (62.1% silicon)

Fluorite concentrate

Cryolite

Salt

Sodium nitrate (GOST 828-68, grade B)

Magnesite

Dump slag production of alloys with rare earth metals.

Aluminum and sodium nitrate were used in the form of finished powders according to GOST 6058-73 and 828-68, the remaining materials were crushed in a ball mill and successively sieved through sieves with 5X5 and 2X2 mm cells. Then the components of the mixture were dried to a moisture content of 0.3%, metered and mixed, mixed vigorously.

Example 1. Steel was treated with a mixture, the components of which, their weight ratio and fractional composition are given in table. 1, mixture 1.

In a 0.5 kg resistance furnace with a graphite heater in an argon atmosphere on

The surface of the molten steel containing 1% carbon and 1.5% chromium, at a temperature of 1570 ° C, introduced 20 g of the mixture. Steel was melted in a magnesite crucible. After melting the slag mixture and holding

melt for 5 min. the crucible was removed from the furnace and the melt was cooled. The finished steel treated with this mixture contained: 0.005% sulfur, 0.0019% oxygen, 0.02% rare earth elements.

Example 2. Steel was treated with a mixture, the components of which, their weight ratio and fractional composition are given in table. 1, a mixture of 2.35 g of the mixture was used to treat steel, as indicated in Example 1. The finished steel contained: 0.007% sulfur, 0.0023% oxygen, 0.015% rare earth elements.

T a b l II c a 1

Example 3. Steel was treated with a mixture, the components of which, their weight ratio and fractional composition are given in table. 1, mixture 3. In a 20 kg arc furnace with a magnesite lining, a melt of steel containing 0.3% carbon was obtained. At a temperature of 1630 ° С, slag was removed from the surface of the melt and 100 g of the mixture was introduced onto the metal mirror. 7 minutes after the mixture was melted, the steel was poured out of the furnace, poured into a chill mold and cooled. In finished

Claims (3)

steel received 0.012% sulfur, 0.0031% oxygen, 0.015% rare earth elements. As can be seen from the table. 1, after treatment of the steel with mixtures 1–5, it received a low content of ser1, oxygen, and microalloying was achieved with rare earth elements. Mixtures 6 and 7 were also tested, in which the ratios of the components were outside the proposed limits. The tests of mixtures 6 and 7 were carried out in a similar way, as shown in example 3. According to the test results, it was found that mixtures 6 and 7 provide neither micro-alloying of steel with rare-earth elements nor effective desulfurization of steel. Mixture b has an excess amount of dross slag, a lack of exothermic and thinning agents, and mixture 7 burns with a high pyro effect and does not have enough silicon to transfer rare earth elements into the metal. An analysis of the test results allows the following conclusions to be drawn regarding the relative components of the mixture. The optimum amount of aluminum powder is 10-25%. A decrease in the amount of aluminum below 10% sells the recovery of rare earth elements from the mixture, and an increase in the amount of aluminum leads to an increase in the oxygen content in the steel (apparently, 20 due to the formation of refractory slags and steel pollution by fine alumina inclusions). The optimal amount of the silicon-containing component in the mixture is 8-20%. With a decrease in its amount by 25, the assimilation by the steel of rare-earth elements is deteriorated, and a higher content of this component in the mixture reduces the basicity and refining properties of the resulting slag. The optimal amount of halides in a mixture is 3-10%, a smaller amount worsens the refining properties of the mixture. Apparently, due to the increase in slag bone, a greater amount of halides can cause air pollution in the workplace. The optimum amount of oxidizers 40 is 10–40%, a smaller amount of them deteriorates the exothermicity of the mixture, a higher one can lead to an explosive reaction and pollution of the workplace atmosphere with nitrogen oxides. The optimum content of magnesite in the mixture is 10-25%. A decrease or increase in its amount in the mixture impairs the refining ability of the mixture, since it leads to an increase in the viscosity of the slags resulting from the combustion of the mixture. The amount of waste slag in the mixture is 15-40% due to the content of oxides of rare-earth elements and the refining properties of the slags resulting from the combustion of the mixture. Thus, the use of the proposed mixture for the treatment of steel allows the simultaneous refining of steel from sulfur and oxygen and microelecting with rare earth elements. In tab. 2 compares the examples of steel processing in the mold according to the invention and the prototype. G5 45 Table 2 Steel with a lower content of oxygen and sulfur and with a relatively high content of REE was obtained at a rate of about 4 times less than the waste slag produced by REE alloys; specific values of sulfur and oxygen removal from metal per unit of consumed slag of REE are 4.5 and 2.9 times higher, respectively, and the specific transition of REE from slag to steel is 2.3 times higher, i.e., using the proposed mixture more The useful properties of waste REE slag are fully realized, more efficient and economical steel processing is achieved. Claim 1. Slag-forming mixture for the treatment of iron and steel, including aluminum powder, material containing halides, and waste slag production of alloys with rare earth metals, characterized in that, in order to improve the efficiency of simultaneous refining of iron and steel from sulfur and oxygen and its micro-alloying with rare-earth elements, it additionally contains a silicon-containing alloy, an oxidizing agent and magnesite in the following ratio of components, weight. %: Powder aluminum 10 25 Silicon-containing alloy 8-20 Oxidizer 10-40 Material containing Halides 10-25 Magnesite Dump slag from snlavov production with rare-earth metals 15-40 2. A mixture according to claim 1, characterized in that the dump slag of the production of alloys with rare earth metals contains the following components, wt. %: Rare earth oxides elements 5-20 Aluminum oxide 30-55 Calcium Oxide 15-45 3-10 Silica 2-10 Magnesium oxide 0.5-10 Sources of information taken into account in the examination 1. USSR Author's Certificate No. 452596, cl. From 21 1/10, 1975. 2. USSR author's certificate number 499320, cl. C 21 C 5/54, 1976. 3. Certificate of authorship on application no. 2472014/02, cl. C 21 C 5/54, April 1977.