RU2492960C1 - Method of producing exothermal and insulation gate system insert - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. Aqueous solution of adhesives and silicate-based cement is prepared in mixing tank. Components of exothermal mix are added to the solution and suspended by mixing at 1500 rpm/min for 10 minutes. Aqueous solution is poured in the mould composed of outer cylinder, inner shell ring with 1.2-1.5 mm-dia holes and mould moving top part secured to male die. After pouring in the mould aqueous suspension is vibrated to squeeze it by the mould moving part. Note here that squeezed out water mix is pumped by vacuum from mould bottom cavity. Insert is withdrawn by feeding compressed air in the mould bottom, under the shell ring. Damp or moist insert is placed on the pallet, dried in furnace and cooled down. Exothermal mix contains the following elements in wt %: aluminium metal - 12-25, Al₂O₃ - 13-35, Fe₂O₃ - 8-30, SiO₂ - 17-28, Na₂O+K₂O - 5-7, CaO - 8-15, MgO - 0.2-4, ceramic fibre - 8-15.

EFFECT: higher quality of inserts, decreased defects, better ecology.

3 cl, 1 ex

Description

The claimed invention relates to metallurgy, and in particular to methods of manufacturing exothermic and insulating inserts of gate systems.

It is known that exothermic mixtures and inserts are intended for use in gate-feeding systems in the production of steel and iron castings. The goal is to eliminate casting defective defects, achieved by local heating of liquid metal (up to 1800 ° C), which slows down the solidification of the melt in the profitable part of the gate system and creates additional gas pressure on the metal in the exothermic reaction zone.

Exothermic mixtures are powders based on metal and aluminum oxides, which provide a significant amount of heat due to redox reactions in contact with liquid metal in profit. The action of exothermic mixtures (heating the metal in profit and increasing the time the atmospheric pressure acts on the liquid metal) improves the efficiency of the profit and prevents the formation of secondary shrinkage shells. Exothermic mixtures can be used as powders on the surface of large open profits and in the form of shaped products (exothermic inserts), which can be made in the form of shells that form the cavity of profit, or inserts (cylinders, cones) fixed in the form. The practice of using "pop-up" inserts made of mixtures with light fillers is practiced. The main advantages of using it are elimination of defective casting defects due to shrinkage defects, increase in suitable casting yield due to reduction of metal consumption of profits by 20-40% (1).

Exothermic and insulating inserts contain two constituent components - exothermic and insulating, each of which has a different composition of ingredients that affect the performance of the inserts. In addition, the geometric parameters and the quality of the surfaces of the inserts often determine the further technology of their use in the gate systems, which ultimately determines the quality of the foundry product and the complexity of its completion.

In turn, the inserts are made in various ways: “dry” or “wet (wet)”, which also largely determines the composition of the components of the mixture for the inserts, the quality of their manufacture and, ultimately, the quality of the molded products. And even the chosen method - “dry” or “wet (wet)” has many options for their implementation, forcing each time specialists - both developing and manufacturing - on the one hand, and casters - on the other hand, to solve the creative problem of constantly improving technologies implement the methods mentioned above. These technologies should take into account at least the requirements for foundry products, including in terms of the quality of the casting and from them it is already possible to meet the requirements for exothermic and insulating inserts.

A known method of manufacturing an exothermal insert for molds, including blowing the mixture into the space formed by the cold box and two rods, forming a hole in the uncured insert, open at both ends, an inner two-sided chamfer at the mouth of the insert and a flat surface with the opposite mouth of the side, curing the insert into cold box by interacting with the catalyst, removing the cured insert from the cold box, placing the plug in the insert hole at the end opposite the mouth, This mixture includes binder and besftoristuyu composition consisting of insulating and exothermic refractory material mixture comprising an oxidizable substance, an oxidizing agent capable of producing an exothermic reaction and magnesium, initiating an exothermic reaction (2). As can be seen from the description, the insert is made by blowing the mixture into the mold, i.e. "Dry way."

Patent (3) claims a composition for the manufacture of insulating or exothermic bushings and other elements of runners and mold feeders by blow molding, containing hollow spherical microparticles of aluminum silicate, a binder and, optionally, non-fibrous fillers, characterized in that it contains a binder cold curing binder, and hollow spherical microparticles of aluminum silicate contain less than 38 wt.% aluminum oxide. Here, the applicant has come to such a mixture composition and method of forming the insert by blow molding in order to obtain good geometry of the outer surface of the insert. This method, like method (2), is “dry” and has all the disadvantages inherent in “dry” methods.

The disadvantages of the "dry" method include, in particular, a sufficiently high fire hazard production of inserts. In addition, the binder, for example, “Rezamin”, used in this method, is toxic, slow-burning, and according to the degree of impact on the human body, it belongs to the second hazard class according to GOST 12.1.005-88. When processing a binder, pairs of phenol, formaldehyde, isocyanate and dioctyl adipate (DOA) are released.

Phenol is a nerve poison. Inhalation of phenol vapor causes irritation of the upper respiratory tract, and with prolonged exposure - general poisoning. Phenol belongs to substances of hazard class 2 according to GOST 12.1.005-88. It is able to penetrate the body through unprotected areas of the skin. In contact with skin, it has a strong cauterizing and irritating effect. The maximum permissible concentration (MPC) of phenol vapor in the air of the working area of industrial premises is 0.1 mg / m ³ . Flash point - 79 ° С, autoignition temperature 595 ° С. Concentration limits of vapor flame spread of 1.52-8.76% vol. The temperature limits of flame spread are 48-83 ° С. The content of phenol vapor in the air of the working area is determined according to the guidelines No. 1461 or according to the method 02-01-95.

Formaldehyde is a protoplasmic poison. It causes a strong irritating effect on the mucous membranes of the eyes and the respiratory tract, is an allergen, belongs to substances of hazard class 2 according to GOST 12.1.005-38. Auto-ignition temperature -430 ° С. Concentration limits of flame propagation 7-73% (vol.). MPC of formaldehyde in the air of the working area of industrial premises - 0.05 mg / m ³ . The content of formaldehyde vapors in the air of the working area is determined according to the guidelines No. 4524-37, No. 4320-83 or by the method 02-02-95.

Diphenylmethanediisocyanate - has a general toxic effect, causes a violation of the central nervous system (CNS) and the cardiovascular system. Irritating to the mucous membranes of the eyes and upper respiratory tract, refers to substances of hazard class 2. Flash point - 90 ° С. The maximum concentration limit of diisocyanate in the air of the working zone is 0.5 mg / m ³ . The vapor content of diisocyanate in the air of the working zone is determined by the guidelines of MU No. 1695-77, issue 1-5, 1981.

DOA (dioctyl adipate) - is a low-volatile, high-boiling liquid, insoluble in water and resistant to hydrolysis. By its effect on the body, it belongs to the 3rd hazard class according to GOST 12.1.007-76. Flash point - 190 ° С; The ignition temperature is 215 ° C. The maximum permissible concentration of vapors in the air of the working area is not defined (GOST 8728-88).

The above disadvantages make the use of a "dry" method of producing inserts extremely undesirable.

Exothermic and insulating casings for casting profits of the FT and FM series are known (4). The basis for the manufacture of exothermic and insulating shells for foundry profits is a special ceramic fiber (FT series) or microspheres (FM series) with the addition of aluminum powder, metal oxides and a binder. The manufacturer notes the features and advantages of such shells:

- shells of these materials allow for a long time to keep the metal in profit liquid, which leads to a reduction in profit up to 4 times compared with the classic;

- the pressure created in the closed profit due to the exothermic reaction, is an essential factor for providing power to the casting even in conditions when the height of the tap profit is less than the height of the feed unit;

- after the end of the exothermic reaction, the shell material retains its thermal insulation properties, while continuing to provide directional solidification in the casting.

Such casings in various specific series are used in the manufacture of small, medium and large castings of cast iron, steel and non-ferrous alloys.

A method of manufacturing shells (4) is “wet” i.e. with suction of the entire mixture on a snap. In this case, the outer surface of the shell turns wavy and rough, so the outer dimensions become significantly less accurate (as can be seen from the photograph posted on the site (4)). The main disadvantage of sucking the entire mixture onto the tool is that the inserts obtained in this way can only be used for molding according to ready-made models, i.e. First, ex profit is established on the model, and then all this is filled up and compacted by the flask. During backfilling and compaction, the flasks of the insert can break, crumple, which affects the quality of casting and increases the percentage of rejects of molded products. Thus, the fuzzy, wavy and rough outer surfaces of the insert (4), due to unsatisfactory external geometry, do not allow it to be installed after the flask is molded according to the models, i.e. to the place where the profitable exhibition was supposed to stand. In addition, this method of vacuum forming the inserts, when the entire mass of the mixture is sucked into the rigging, seems to us uneconomical.

A known method of manufacturing bushings by vacuum and wet molding, followed by drying and polymerization of resins at high temperature (Spanish patent No. 8403346 (5), described in RF patent No. 2176575 (3). A standard method of this type includes the following operations:

- suspending in water a mixture obtained from materials used in the manufacture of bushings, for example fibers from aluminosilicates, aluminum, iron oxide and phenolic resins, or, alternatively, a mixture obtained from silicon sand, aluminum slag, cellulose, aluminum and phenolic resins;

- vacuum absorption of said aqueous suspension through the outer and inner surface of the mold;

- removing from the mold a wet or wet sleeve, laying on a pallet, which in turn is placed in a furnace in which it is left for a period of 2 to 4 hours at a temperature of approximately 200 ° C, followed by cooling.

In some cases, not all aluminosilicate raw materials are present in the form of fibers, since part of it can be replaced by spherical hollow microparticles of the said aluminosilicate material in order to reduce the required amount of product and reduce the cost of the finished product. Such spherical microparticles are then used as a filler.

This process makes it possible to obtain bushings from an insulating or exothermic material (5).

As already noted in (3), method (5) has many disadvantages, among which the following are established.

The main disadvantage is the impossibility of producing bushings with sufficient accuracy of the outer dimensions, since suction of the mixture through the mold allows to obtain high precision bushings on the inner surface (which is in contact with the mold), but not on another surface. This inaccuracy leads to a mismatch in the sizes of the outer contour of the bushings with the internal cavity of the channels for topping up, which often leads to significant difficulties in their placement and connection. Those. the same disadvantages as described above with respect to the method (4) take place.

Another significant drawback of the method (5), affecting the ecology of production, is the presence in the mixture for the preparation of bushings of phenolic resins, the disadvantages of which are described above in relation to the "dry" methods.

Another disadvantage of method (5) is the vacuum absorption of the entire aqueous suspension through the outer and inner surface of the mold (tool), which leads to the removal of the necessary finely dispersed fractions of a number of components from the mixture, therefore, this technological technique seems to us inefficient and uneconomical, which does not allow us to achieve our goal - leaving in the wet molded insert the necessary components.

The closest analogue of the claimed method is a method of manufacturing exothermic and insulating inserts of the gate system, comprising suspending the mixture components in water, pouring an aqueous suspension into the mold for preparing the insert, pumping out the aqueous solution from the internal cavity of the mold, supplying compressed air under the upper part of the mold to extract the insert from the mold, laying the insert on a pallet, drying in an oven and subsequent cooling of the insert (GB 1204472A, 09/09/1970, page 1 lines 15-35, page 2, lines 60-85, page 3, lines 44-101, FIG. .one.)( 6).

The technical result of the proposed method is to obtain inserts with a more uniform density in volume and high-quality external and internal surfaces due to vibration of the aqueous suspension, which ensures smooth swelling of the mixture into the mold with simultaneous removal of various air inclusions.

The creation of a "wet (wet)" method of manufacturing exothermic and insulating inserts of gate systems using the claimed technology of partial evacuation of the mixture in combination with the selection of the components of the mixture described in the present invention allows to obtain exothermic and insulating inserts with high quality of both the outer and inner surfaces having sufficient strength at a relatively low density (450-600 kg / cubic meter, m) using less harmful components in the mixture than phenolic resins , which makes the production of inserts more environmentally friendly (less harmful for working people), and mainly increases the efficiency, efficiency and quality of the foundry itself when casting steel, cast iron and other castings, including by reducing the level of marriage or casting defects and improving the accuracy of castings.

The technical problem of obtaining exothermic and insulating inserts of the claimed method, using the appropriate components of the mixture and their ratios is solved as follows.

The inventive method of manufacturing exothermic and insulating inserts of the gating system, comprising suspending the components of the mixture in water, pouring an aqueous suspension into the mold to prepare the insert, pumping the aqueous solution out of the mold cavity with a vacuum pump, supplying compressed air to extract the insert from the mold, laying the insert on a pallet drying in an oven and subsequent cooling of the insert, characterized in that the form is performed in the form of an outer cylinder, an inner shell having through holes with a diameter of 1 , 2-1.5 mm, and the movable upper part of the mold attached to the punch, while after pouring into the mold, the aqueous suspension is vibrated, then compressed by the movable part of the mold, and to extract the insert from the mold, compressed air is supplied to the lower part of the mold under the shell .

Thus, the inventive method allows to obtain inserts with a more uniform density in volume and high-quality external and internal surfaces due to vibration of the aqueous suspension, which ensures smooth flowing of the mixture into the mold with simultaneous removal of various air inclusions.

The inventive method of manufacturing exothermic and insulating inserts of the gating system uses in the mixture, along with adhesives from an aqueous solution, including silicate glue, components in the following proportions (in volume percent):

Al (metal) 12-25% Al ₂ O ₃ (Alumina) 13-35% Fe ₂ O ₃ (Iron Oxide) 8-30% SiO ₂ (Silicon Oxide) 17-28% Na ₂ O + K ₂ O (Sodium oxide and potassium oxide) 0.5-7% CaO (calcium oxide) 8-15% MgO (Magnesium Oxide) 0.2-4% Ceramic fiber 8-15%

In addition, an organic-based precipitant is added to the mixture. The addition of an organic-based precipitant to the composition of the exothermic mixture allows the manufacturer to achieve the most efficient use of exothermic additives having sufficiently fine fractions (finely dispersed, for example: Al ₂ O ₃ - 5-10 microns, MnO ₂ - 45-65 microns, SiO ₂ - 45 -85 microns, Fe ₂ O ₃ - 5-25 microns) and as a consequence, suffer from a further (excessive) removal at the time of pumping a vacuum, which then entails uncontrolled during vakuumatsii depletion exothermic mixture and consequently decrease eff objectively profitable operation inserts.

The claimed method meets the condition of novelty, the condition of inventive step, since the prior art has not identified solutions that have signs that match the distinctive features of the claimed invention, and the condition of industrial applicability.

The inventive method for the manufacture of exothermic and insulating inserts of gate systems consists of the following main technological operations.

1. Preparation of the components of the mixture: alumina, iron oxide, hollow spherical microparticles.

An aqueous solution of adhesives, water and silicate glue are prepared in a stirring tank.

2. Addition of the mixture of components to this aqueous solution with a simultaneous increase in the speed of the stirrer tank to 1500 rpm. Mixing is carried out for 10 minutes from the time of falling asleep of the last component.

3. Adding heat-insulating ceramic fibers with the content of aluminosilicates to the existing mixture with simultaneous stirring in the mixer for 5-7 minutes at floating and increasing speeds from 500 to 1200 rpm. This is important for good mixing of the fibers.

4. The complex mixture of the components of the exothermic mixture and isothermal fibers after their final preparation in the mixer tank is poured into a mobile bath with which it is delivered to the molding table.

5. The forming table consists of a body with a horizontal surface (work table), on which at least one, and, as a rule, 4 or more forms for preparing inserts is placed. Each form is supplied with vacuum from a vacuum pump, as well as compressed air from a compressor. The geometry of the insert is determined by the inner diameter of the outer cylinder, the outer dimensions of the surface of the inner shell, standing inside the cylinder on the molding table and having through holes with a diameter of about 1.2-1.5 mm, and the inner surface of the punch.

6. The volume-dosed mixture is fed from above to the shell. When the mixture is fed into the working form, the desktop vibrator is turned on. The result is a smooth swelling of the mixture into the mold with the simultaneous removal of various air inclusions. If necessary, the mixture is manually rammed.

7. To precipitate active exoadditives on the fibers, an organic-based precipitant is added to the working exothermic solution of the mixture, which helps to “fix” active exoadditives (aluminum oxide, nitrate, magnesium oxide) on the refractory fibers of the exosmix. This contributes to the fact that the maximum number of exoadditions remains in the product (insert), preventing the collection of moisture from the product.

8. The mixture is pressed by a punch having a surface corresponding to the specified external dimensions of the future insert. The punch drops to the desired height corresponding to the height of the future insert. The mixture is compressed. The aqueous solution flows through the holes in the shell and is sucked off by a vacuum pump. Thus, 4 or more inserts can be molded in one go. After crimping with a punch and keeping the vacuum in order to remove the discharge in the mold itself, air is supplied to the lower part of the mold, under the shell, which contributes to a good clean removal of the insert from the shell and removing it from the mold.

9. Thermal drying of inserts in a thermal furnace at a temperature of 100-250 degrees Celsius for 20-40 minutes.

10. Quality control, sorting and packaging of finished inserts in containers.

11. Inserts are made for specific cast products of the customer, indicating the dimensions of the casting, the type of metal (aluminum, bronze, cast iron, steel (indicating its brand). Example 1

Exothermic and insulating inserts were made using the following composition:

Al (metal) 12% Al ₂ O ₃ (Alumina) 5% Fe ₂ O ₃ (Iron Oxide) 25% SiO ₂ (Silicon Oxide) twenty% Na ₂ O + K ₂ O (Sodium oxide and potassium oxide) 7% CaO (calcium oxide) fifteen% MgO (Magnesium Oxide) four% Ceramic fiber 12%

The relative popularity of the features of one or another developed method of manufacturing inserts even for an experienced specialist in the industry does not mean the possibility of its successful application in its method. Often, numerous experiments are required, mathematical models are developed, with reference to each technical task for a specific serious casting. The foregoing suggests that in such an industry as metallurgy, even small nuances of the method can be inventive. This is confirmed by the long-standing practice of the applicant.

The applicant, for the first time in Russia, successfully mastered the large-scale production of shell inserts of profitable parts of castings, both gas pressure with heating by exothermic mixtures, and heat-insulating, adiabatic (7). The products manufactured by him can be delivered and delivered to many metallurgical enterprises in Russia and the near abroad, both with the installed profitable rods in them to facilitate profit cutting, and without them.

The inserts produced by the applicant are highly adaptable and can achieve, when applied, the following results:

- increase the yield of casting on large castings up to 25%;

- reduction of metal consumption of the casting up to 40%;

- reduction of technological allowances for machining profitable castings from 15-20 mm to 4-5 mm;

- reduction, several times, of the consumption of metalworking tools;

- the complete elimination of the labor-intensive process of firing profit segments;

- the ability to install profits on any surface without violating the configuration of the casting;

- improving the quality of casting to reduce shrinkage defects (shells, friability, cracks), as well as non-metallic and gas inclusions;

- the possibility of serial production of inserts according to the individual customer’s specifications (shell shape and dimensions, geometrical parameters of a profitable core to facilitate profit cutting, heat storage capacity, exothermic reaction module, delayed combustion initiation, etc.).

The exothermic mixtures used by the applicant have the following characteristics:

- low flash point;

- stable burning of the mixture with an adjustable speed;

- an increase, not less than twice, of the total time of solidification of profits with exothermic mixtures, compared with conventional;

- good thermal insulation of the mixtures after the completion of the exothermic process;

- the lack of chemical interaction of the metal profit with the mixture;

- the lack of stable gas evolution during combustion of the mixture;

- lack of pyroelectric effect;

- high strength at all stages of the process;

- lack of a mechanical burnout;

- high gas permeability;

- lack of emissions of harmful substances.

Literature

1. www.lityo.com.ua/mi_3.html

2. RF patent No. 2299781 (prior. 09.09.2002).

3. RF patent No. 2176575 (prior. 09.07.1997).

4. www.ruscastings.ru/work/168/441/443/6805.

5. Spanish patent No. 8403346 (described in the patent of the Russian Federation No. 2176575 (3).

6. British patent No. 1204472A, (prior. 09.09.1970).

7.http: //masterm-vo.ru.

Claims (3)

1. A method of manufacturing exothermic and insulating inserts of the gate system, comprising suspending the components of the mixture in water, pouring an aqueous suspension into the mold to prepare the insert, pumping the aqueous solution out of the mold cavity with a vacuum pump to supply compressed air to extract the insert from the mold, laying the insert on a pallet drying in an oven and subsequent cooling of an insert, characterized in that a mold consisting of an outer cylinder, an inner shell having through holes with a diameter of 1.2-1.5 m is used And a movable upper mold part attached to the punch, wherein the aqueous slurry after pouring in the form is vibrated, compressed then the movable mold part and for extracting the insert from the mold of the compressed air supply carried out in the lower mold part under the shroud. 2. The method according to claim 1, characterized in that the following components of the mixture, vol.%: Are introduced into the aqueous solution of adhesive substances:
Al metal 12-25 Al ₂ O ₃ 13-35 Fe ₂ O ₃ 8-30 SiO ₂ 17-28 Na ₂ O + K ₂ O 0.5-7 Cao 8-15 MgO 0.2-4 Ceramic fiber 8-15 3. The method according to claim 2, characterized in that an organic-based precipitant is additionally added to the mixture.