RU2634535C1 - Method for ceramic grinding bodies producing - Google Patents

Abstract

FIELD: metallurgical engineering.

SUBSTANCE: method includes the preparation of charge containing waste of copper smelting production, melting it to produce cast iron, casting it into moulds and extracting cast iron moulds in the form of grinding bodies from them. As starting materials of the charge, a mixture of slag from copper smelting production, containing copper from 0.7 to 2.4%, and a carbonaceous reductant is used, pellets are produced from the resulting mass, which are dried and roasted in a reducing medium to obtain metallized pellets which are charged in arc furnace and melted to produce cast iron.

EFFECT: invention makes it possible to reduce the cost of manufacturing grinding balls from cast iron containing sulfur in quantity, while ensuring their high wear resistance.

2 ex, 2 tbl

Description

The group of inventions relates to the production of cast iron products, in particular to the production of cast iron grinding bodies (balls and tilbeps) and their composition, and can be used for disposal of waste from copper smelting in those regions where it is available.

The problem is as follows.

The maximum sulfur content in cast iron grades currently used is limited to 0.15%, therefore, in the production of cast iron and steel, desulphurization of the feedstock and (or) liquid metal is performed. The desulfurization process significantly complicates the process and increases the cost of production.

It is known that in the production of pig-iron grinding bodies, various alloying additives are introduced to obtain the necessary operational properties, which change the structure of the metal and improve the indicators of wear resistance and impact resistance (Girshovich N.G. Cast iron. Training manual. L. - M .: Mashgiz, 1949).

The introduction of such additives complicates the technology and increases the cost of production.

One of the alloying additives used is copper. It is known that the introduction of copper increases the ductility of the metal, which positively affects the indicators of wear resistance. The positive effect of copper alloying of cast iron for cast grinding media was noted in the book of authors Mikhailov A.M., Bauman B.V., Blagov B.N. "Engineering", 1987

At the same time, the copper content in the vast majority of steel and cast iron grades used in metallurgy is limited to 0.3%, which is associated with the effect of “red breaking” during metal rolling.

Currently, there are no cheap and effective methods for separating iron from copper in a melt, therefore, some natural and man-made sources of iron production are not used in metallurgy. A potential raw material base for ferrous metallurgy is the waste from the copper industry: slag, which, depending on the technology adopted at the plants, contains from 0.3 to 1% copper and up to 40% iron. In this case, as a rule, in the dumps of enterprises slags with different copper contents are contained: granulated, produced by outdated technology and sludges obtained from ground slags and subjected to foam flotation for the maximum possible copper recovery. These slags in millions of tons are stored in dumps, which occupy large areas and create environmental problems.

Copper slag contains up to 1.5% sulfur. In one of the most efficient production methods using solid-phase reduction of iron, cheap types of coal (including brown) that are not used in traditional metallurgy are used as a reducing agent, which introduces an additional amount of sulfur into the metal.

The applicant experimentally found that when the sulfur content in cast iron in an amount of up to 2% in the presence of 0.7-2.0.% Copper, the operational properties of grinding media are within the limits of GOST 7524-89 "Steel grinding balls" and KR ST 2310-2013 "Cast-iron cast-iron grinding balls" of the Republic of Kazakhstan. This allows cast iron for grinding media from copper slag to dispense with the operation of desulfurization, which significantly reduces production costs. In addition, cast iron from copper slag is obtained by naturally alloyed free copper.

A known method of producing castings of a wearing part from white wear-resistant cast iron (see Belarus patent No. BY 10945 C1 from 2008.08.30).

The known method includes melting the mixture, the introduction of an alloying additive, pouring the molten iron into the mold and removing the casting from the mold and differs in that 3-6 wt. % complex alloy, which is a by-product of normal corundum smelting and containing by weight: 1.3-2.0% carbon, 8-12% silicon, 0.3-1.0% manganese, 0.4-0.9% nickel , 0.6-1.5% chromium, 3-7% titanium, 0.5-1.0% vanadium, 0.3-0.6% tungsten, 0.3-0.6% molybdenum, 0.6 -1.6% of aluminum, 0.03-0.1% of copper, 0.08-0.10% of phosphorus, 0.01-0.02% of sulfur and the rest of the iron, casting of iron is carried out at 1360-1380 ° C in sand-clay form, and after extraction from the mold, the casting is cooled in air.

This method allows to obtain grinding media with normative operational characteristics, using as an alloying agent a cheap by-product of fusion of electrocorundum. The disadvantage is that 94-97% of the composition of the charge is expensive iron raw materials, smelted according to traditional technology.

There is a method of producing cast billets from white wear-resistant cast iron for wear parts, presented in clause of the Russian Federation No. 2169787 by class. C22C 37/0.

The known method includes smelting, alloying and modifying cast iron to obtain a given composition, producing castings by casting cast iron in sand or metal molds, cleaning and heat treatment of castings, using cast iron of the following composition, wt. %: carbon 2.4-4.0; silicon 0.5-1.5; Manganese 2.0-4.0; nickel 2.0-4.0; chrome 8.0-12.0; molybdenum 0.5-0.8; boron 0.1-0.3; barium 0.005-0.001; phosphorus 0.02-0.07; sulfur 0.02-0.07; iron is the rest.

The disadvantage of this method is the use of an increased amount as alloying components of expensive and scarce elements of chromium, nickel, molybdenum and others, which significantly increases the cost of castings.

A known method of smelting cast iron [see RF patent No. 2409681 by class C21B 11/10]. The known method includes filling iron ore and coke in a furnace, heating and melting it with an electric arc, reducing iron, producing pig iron and slag, and differs in that the waste open-hearth furnace slag with iron content up to 36%, manganese up to 9% and ferroalloy metals, iron and manganese are reduced, after reduction, the melt is treated with fluorides or chlorides of alkali or alkaline earth metals, packed in a metal capsule, and the cast iron is refined and refined of slag.

The disadvantage of this method, in which industrial waste is used as iron-containing raw materials, is the complexity of execution associated with the need for additional expensive alloying operations and the manufacture of special capsules for this purpose.

The known composition of wear-resistant cast iron (patent 831851), containing as alloying additives copper 0.6-1.4% (by weight) and rare earth metals.

The disadvantage of this cast iron is the high cost of alloying additives.

A known composition for producing grinding media from cast iron, presented in paragraphs of the Russian Federation No. 2055930 "Wear-resistant cast iron."

The known composition contains 1.0-2.4% of copper. The remaining components, mass%: Carbon - 3.9-4.5; Manganese - 5-9; Silicon - 0.5-1.2; Aluminum - 0.5-1.5; Vanadium - 0.1-0.45; Copper - 1.0-2.4; Calcium - 0.01-0.05 Cerium - 0.01-0.05 Iron - the rest. Copper according to the invention is introduced to stabilize austenite to a certain level. In addition, copper increases the viscosity and strength of cast iron. Its content is less than 1.0% ineffective, because does not provide sufficient stabilization of austenite.

An increase in copper content of more than 2.4% contributes to excessive stabilization of austenite, which reduces the effect of self-hardening during operation, and also contributes to graphitization of cast iron and embrittlement of the alloy.

The disadvantage of this composition of cast iron is the use of alloying additives specially introduced during melting, vanadium, cerium, manganese, which complicates the technology, necessitates overheating of the melt, and makes production more expensive. Sulfur is absent in the composition of cast iron, which indicates an expensive operation of desulphurization of cast iron. All these factors lead to an increase in the cost of products.

Closest to the technical nature of the claimed means are a method for producing cast iron grinding bodies and the composition of these bodies, presented in clause of the Russian Federation No. 2016077, class. C21C 1/08, claimed 04/03/1992, publ. July 15, 1994

The known method includes melting a mixture based on pig iron with alloying elements introduced into it in the form of waste from the production of stone products from copper smelting slag, casting iron into metal molds and removing castings from molds. This method allows to reduce the cost of products due to the use of waste as an alloying copper-containing additive.

The known chemical composition of the material obtained using this method of balls is as follows, wt. %: 3.11-3.9 C; 0.11-0.8 Si; 0.02-0.8 Mn; 0.9-2.1 Cu, iron - the rest.

A disadvantage of the known method and composition is that up to 15% of waste from the melting of copper slag is used as an alloying copper-containing additive, and at least 85% of the charge is made up of expensive iron raw materials: pig iron smelted by traditional technology.

In addition, stone casting from copper slag has not found industrial application.

The objective is to reduce the cost of manufacturing grinding balls made of cast iron while ensuring their high wear resistance.

The problem is solved in that

- in a method for producing pig-iron grinding bodies, including preparing a charge containing waste from copper smelting, melting it and producing cast iron, casting it into molds and extracting from them cast iron castings in the form of grinding bodies, ACCORDING TO THE INVENTION, ACCORDING TO THE INVENTION, charge materials are used as starting materials a mixture of copper smelting slag containing copper from 0.7 to 2.4% and a carbon reducing agent, pellets are made from the resulting mixture, which are dried and calcined in a reducing medium to obtain metallization Rowan pellets were charged into the arc furnace and is melted to yield pig iron that is poured into molds.

The use in the method of producing pig-iron wear-resistant grinding balls as a charge of slag from the production of copper, contained in it in an amount of 0.7-2.4%, makes it possible to obtain inexpensive, but having good wear resistance due to the use of 100% raw materials as waste from the smelting production grinding balls, since the copper contained in the slag serves as an alloying additive.

It was experimentally established that when the copper content is less than 0, 7%, the impact resistance of grinding media decreases. When the copper content is more than 2.4%, the hardness of grinding balls decreases. An increase in the sulfur content in cast iron in an amount above 2% reduces the impact resistance of grinding media. In addition, the casting properties of cast iron melt are deteriorating, which is reflected in the overgrowing of the sprue channels.

Therefore, despite the fact that the copper smelting slag includes sulfur, however, in the presence of copper in it in an amount of 0.7-2.4%, the content in the grinding pig-iron balls of sulfur obtained by the inventive method in an amount of up to 2% of the mass does not reduce wear resistance and strength properties of these balls, without requiring desulfurization and ensuring their low cost.

The technical result is a reduction in the cost of obtaining grinding cast iron bodies while ensuring their high wear-resistant properties.

The inventive method has a novelty in comparison with the prototype, differing from it by the presence of such distinctive features as the use of raw materials of a mixture of slag from a copper smelter containing copper from 0.7 to 2.4%, and a carbon reducing agent, the manufacture of the obtained mixture of pellets which are dried and fired in a reducing medium to obtain metallized pellets, loading them into an arc furnace and smelting to produce cast iron, which is poured into molds that together provide the given result.

The applicant is not aware of technical solutions possessing the indicated distinguishing features that would ensure the achievement of a given result, therefore he believes that the claimed method meets the criterion of "inventive step".

The inventive method for producing cast iron grinding bodies and their composition can be widely used for the disposal of waste from smelting production, in particular, in the Southern Urals and in other regions and therefore meet the criterion of "industrial applicability".

The invention is illustrated in the tables, which show the composition of cast iron for examples of practical implementation.

The inventive method for producing cast iron grinding bodies is as follows.

Take the charge in the form of iron and copper slag from copper smelting at a copper content of 0.7 to 2.4% in the total mass and subjected to smelting. Then the melt is poured into molds and castings are removed from the molds.

In the composition obtained by the claimed method of cast iron grinding media, including cast iron and copper in wt. % 0.7-2.4, possibly a sulfur content of not more than 2%.

Examples of practical implementation of the proposed method.

Example 1. The starting material: copper slag from the tailings of the processing of the Balkhash concentrator and reducing agent (coal) were dried to constant weight in an oven. The coal was ground in a disk mill to a fraction of minus 1 mm, after which the slag, coal and binder were mixed. The amount of reducing agent in the mixture was 15%. A dry binder in an amount of 4% was added to the resulting mixture. Pellets (with a diameter of 10-20 mm) with the addition of 12% water were made from the resulting mass on a laboratory granulator.

The pellets were dried in a drying oven at a temperature of 120 degrees.

The dried pellets were placed in alundum crucibles, covered with lids (crucibles of a smaller diameter) and covered with crushed coal. The crucibles were placed in a muffle furnace. The material was calcined in a reducing medium. The presence of a reducing medium in the furnace was confirmed by the remains of unburned coal in crucibles after firing. After this treatment, the pellets became metallized, since iron oxides were reduced to metal almost completely. Further, the pellets were loaded into an arc furnace and cast iron was smelted from them. The metal yield was 30% by weight of the sludge. The metal was white cast iron (approximately 40% iron carbide and 60% perlite), sulfur was in round balls of 10-50 microns in the form of iron sulfides FeS mixed with Cu. The melted metal was molten in an induction furnace at a temperature of 1420 ° C (melting time 30 min) and cast into a cast iron chill mold.

As a result, samples of cast iron balls with a diameter of 40 mm were obtained.

The hardness test of samples of cast iron obtained by pouring balls showed a value of 52 units on the Rockwell scale, which corresponds to group II hardness according to Technical Requirements GOST 7524-89 "Steel grinding balls" and KR ST 2310-2013 "Cast iron grinding balls."

When repeatedly dropping from a height of 4 m onto a cast-iron plate, no chips or dents were found on the balls.

The chemical composition of cast iron is shown below in table. one.

The high sulfur content (1%) did not lead to a deterioration in the mechanical properties of cast iron below that required for grinding media. The presence of 1% copper, which is mainly found in ferrite, increases its ductility and overall product.

Example 2. As the source material was used slag from the flotation tailings of the Karabash smelter. Cast iron balls were made using the same technology as in Example 1, but balls with a diameter of 80 mm were cast. Due to the high sulfur content in the slag, 30% of granulated copper slag of the same plant (from old dumps) was added to the feedstock, the difference of which was the increased copper content (0.6%).

The chemical composition of cast iron obtained from a mixture of two types of copper slag is given below in table. 2.

As follows from the data table. 2, the sulfur content in cast iron from a mixture of two types of slag was 1.65%. The hardness test of samples of cast iron obtained by pouring balls showed a value of 52 units on the Rockwell scale, which for a ball diameter of 80 mm corresponds to the III group of hardness according to Technical Requirements GOST 7524-89 "Steel grinding balls" and KR ST 2310-2013 "Cast iron balls grinding ”.

Thus, the use of a mixture of pig iron for smelting grinding media from slag from copper production allows to obtain products with high performance characteristics, while eliminating the desulfurization operation.

In comparison with the prototypes of the claimed method for producing cast iron grinding bodies from cast iron and the composition of the cast iron grinding bodies obtained in this way are cheaper with good wear resistance of the obtained balls.

Claims (1)

A method of producing cast iron grinding bodies, including preparing the raw materials of the mixture, containing waste from copper smelting, its melting to produce cast iron, casting it into molds and removing from them cast iron castings in the form of grinding media, characterized in that as the raw materials of the mixture use a mixture of slag from a copper smelter containing copper from 0.7 to 2.4%, and a carbon reducing agent, pellets are made from the resulting mass, which are dried and calcined in a reducing medium e to obtain the metallized pellets, which are used when loading the charge into the arc furnace and melting it to obtain iron.