RU2469813C1 - Mix for making casting moulds and cores and method of its production (versions) - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed mix is prepared by cladding quartz sand by premade suspension from solution of carboxymethyl cellulose and periclase powder hardener, processing cladded sand in boiling bed by warm air of 50-80°C, and adding solution of alumina-boron phosphate concentrate into said solution.

EFFECT: higher mechanical properties and strength.

2 cl, 3 tbl, 2 ex

Description

The invention relates to the field of foundry and can be used for the manufacture of ceramic molds and cores in the manufacture of castings from alloys of non-ferrous and ferrous metals.

The global trend in the development of shaping processes for foundry is the use of cold hardening mixtures (CTS). Hardening in a snap at room temperature provides the rods and molds with high accuracy and low energy costs for their manufacture. At the same time, HTS was most widely used on organic binders - synthetic resins. These mixtures have a number of advantages compared with the known CTS on inorganic binders (liquid self-hardening mixtures (HSS), plastic self-hardening mixtures, CO ₂ process, etc.). Such advantages are better surface cleanliness, incomparable with LSS ease of removal of rods from castings and the regenerability of spent mixtures (Prospects for the use of phosphate cold hardening mixtures (Foscon process) / G.A. Kollodiy, S.S. Tkachenko, BCKrivitsky // Russian Foundry . - 2004 - No. 8. - S.23-24).

However, to date, a significant problem remains the environmental safety of the processes for producing castings using furan, phenolic and other resins and their impact on the environment (Prospect for the use of phosphate cold-hardening mixtures (Foscon-process) / G.A. Kollodiy, S.S. .Tkachenko, BCKrivitsky // Foundryman of Russia. - 2004 - No. 8. - S.23-24).

ChTS on inorganic binding materials, for example, on solutions of aluminum phosphate concentrate (ABPK), are promising in this direction. Such mixtures have the following advantages (Prospects for the use of phosphate cold-hardening mixtures ("Foscon" process) / G.A. Kollodiy, S.S. Tkachenko, BCKrivitsky // Foundry worker of Russia. - 2004. - No. 8. - P.23 -24). Complete absence of adhesion, easier knockability from castings, high heat resistance and low gas content of the mixture compared to other CTS. The possibility of using inexpensive domestic materials, as well as up to 80% of the regenerate after mechanical regeneration and universal mixing equipment, environmental friendliness of ABFC.

The closest in technical essence is a mixture for the manufacture of foundry molds and cores (RU No. 2281830, IPC В22С 1/00, application. June 21, 2004, publ. 08/20/2006), including a solution of alumina-phosphate concentrate, periclase powder hardener and quartz sand in the following ratio of ingredients, wt.%:

solution of aluminoborphosphate concentrate 3 ... 5; periclase powder hardener 1,0 ... 1,5; quartz sand rest.

The method for preparing such a mixture consists in introducing an ABFC solution into quartz sand with a periclase powdery hardener, these ingredients are mixed and the resulting mixture is immediately compacted in a snap, for example, by vibration. The mixture of the prototype and the method of its preparation makes it possible to obtain castings from alloys of ferrous and non-ferrous metals.

However, the prototype has the following significant disadvantages:

- the physicomechanical properties of the mixture do not allow for the stable production of cores and molds during large-scale production of castings (for example, insufficient strength of cores after 1 hour makes it impossible to quickly remove cores from equipment, especially if cores of complex configuration are made);

- a long cycle of forming the manipulative strength of foundry molds and cores, especially for large-scale production conditions, for example, in automobile and tractor manufacturing;

- the method of preparation of the mixture does not provide a uniform distribution of the powder hardener and, therefore, causes instability of the obtained properties;

- the prototype method does not allow the effective activation of ABFC and increase the physicomechanical properties of the mixture for the manufacture of cores and molds, especially for complex castings.

The basis of the invention is the technical task of improving the physicomechanical properties of the mixture, in particular strength after 1 hour and the accelerated formation of the manipulative strength of the rods and molds necessary to improve the quality of manufacturing complex and thin relief castings.

The specified technical problem is solved in that the mixture for the manufacture of foundry molds and cores, including a solution of aluminum phosphate concentrate, periclase powder hardener and quartz sand, according to the invention, additionally contains a solution of carboxymethyl cellulose in the following ratio of ingredients, wt.%:

solution of aluminoborphosphate concentrate 2 ... 8; periclase powder hardener 0.8 ... 1.7; carboxymethyl cellulose solution 1 ... 3; quartz sand rest.

The problem is also solved by the fact that in the method of preparing a mixture for the manufacture of foundry molds and cores, comprising introducing a solution of aluminum phosphate concentrate into quartz sand with a periclase powder hardener, according to the invention, it is treated with nanosecond electromagnetic pulses with a specific pulse power of 400 ... 900 before introducing a solution of aluminum phosphate concentrate MW / m ³ .

In addition, the stated technical problem is also solved by the fact that in the method of preparing a mixture for the manufacture of foundry molds and cores, comprising introducing a solution of aluminum phosphate concentrate into quartz sand, according to the invention, before introducing a solution of aluminum phosphate concentrate, quartz sand is clad with a previously prepared suspension from a solution of carboxymethyl cellulose and periclase powder hardener with subsequent processing of clad sand in a fluidized bed warm in air with a temperature of 50 ... 80 ° C.

The use of an alumina-borophosphate concentrate and a periclase powder hardener as a binder aqueous solution provides the required shaping cycle and excludes drying of manufactured molds and cores due to chemical hardening of the mixture.

The introduction of additional carboxymethyl cellulose in an amount of 1 ... 3 wt.% Creates the conditions for cladding and even distribution of the periclase piston-like hardener of the mixture, as well as an increase in the strength characteristics of the rods and molds, especially immediately after the mixture has hardened.

Cladding of sand with a suspension from a solution of carboxymethyl cellulose and a periclase piston-like hardener ensures uniform distribution of the hardener in the mixture volume. At the same time, clad sand can be stored in a separate container for unlimited time and, if necessary, be used for the preparation of XTS, which ensures high adaptability of the proposed method for preparing the mixture.

Processing of clad sand in a fluidized bed with warm air with a temperature of 50 ... 80 ° C creates the conditions for accelerated preparation of a filler clad in a hardener and to improve the physicomechanical properties of CTS and the quality of castings.

Processing with nanosecond electromagnetic pulses (NEMI) increases the cohesive strength and can significantly improve the physicomechanical properties of the mixture due to its electrophysical activation.

The preparation of the inventive mixture for the manufacture of foundry molds and cores is as follows. A calculated amount of a solution of ABFC and a powdered periclase hardener is attached to it, as well as a solution of carboxymethyl cellulose and silica sand. Then a suspension is prepared from a solution of carboxymethyl cellulose and a periclase powder hardener, it is poured into quartz sand, for example, grades 3K ₃ O ₂ 03 or 5K ₃ O ₂ 03 (GOST 2138-91), pre-mixed and treated in a fluidized bed with warm air with a temperature of 50 ... 80 ° C. Prepared clad sand can be stored indefinitely. As necessary, it is poured into the mixing equipment, for example, runners or a screw mixer, the calculated amount of ABFC solution is added, the ingredients are mixed, and after removing the mixture from the equipment, rods and molds are manufactured in a snap, for example, by vibration compaction.

To further improve the physicomechanical properties of the mixture in the manufacture of castings that are particularly complex in configuration, NEMI can process the ABFC binder solution. For this, a copper emitter connected to an NEMI generator with parameters: 1 MW per pulse, field strength 10 ⁵ -10 ⁷ V / m, duration of one pulse 10 ^-9 -10 ^-10 s is immersed in an ABFC solution. The specific impulse power is 400 ... 900 MW / m ³ .

The expansion of the range of values for the amount of ABFC solution in the mixture compared to the prototype is dictated, on the one hand, by the need for its hardening for the manufacture of large-sized massive castings of a particularly complex configuration (upper limit), and on the other, the possibility of reducing the amount of the liquid phase in the mixture with the same properties for account of electrophysical processing (the effect of "dilution") for economic reasons for castings for non-essential purposes (lower limit). Due to the expansion of the range of values for ABFC solution, the range of values for periclase powder hardener also changes.

The content in the proposed mixture ABFC less than 2 wt.% Adversely affects the strength and shedding of the finished molds and cores, and therefore leads to a decrease in the surface quality of the finished casting. The reason for this is the lack of binder material in the mixture. On the contrary, the content of ABFC more than 8 wt.% Leads to a deterioration in knockability, as well as an increase in the cost of the mixture.

The amount of periclase powder hardener in the composition of the mixture of 0.8 ... 1.7 wt.% Is optimal from the standpoint of ensuring the required duration of its solidification and survivability. A content of periclase powder hardener in the mixture of less than 0.8 wt.% Leads to an excessive increase in the solidification time of the mixture. The content of periclase powder hardener of more than 1.7 wt.% Causes a significant decrease in the survivability of the mixture.

A solution of carboxymethyl cellulose in the proposed mixture of 1 ... 3 wt.% Provides a high degree of uniformity of cladding of particles of silica sand. If its amount is less than 1 wt.%, Then it is not possible to evenly distribute and adhere the particles of powdered periclase hardener on the surface of sand grains. As a result, the instability of the properties of the mixture and the low quality of castings. If the amount of carboxymethyl cellulose is more than 3 wt.%, Then an undesirable clumping is observed during the preparation of quartz sand.

Processing of clad sand in a fluidized bed with a temperature of 50 ... 80 ° C speeds up the process of its preparation. If the temperature is less than 50 ° C, then it is not possible to provide a significant reduction in the duration of preparation of clad quartz sand. If the temperature is more than 80 ° C, then the integrity of the cladding layer on the particles of quartz sand is broken as a result of its loosening due to evaporation of moisture at high speed.

For the manufacture of particularly complex configurations of high-relief castings, a specific pulsed power of NEMI in the range of 400 ... 900 MW / m ³ is recommended for processing the ABFC solution in order to increase the cohesive strength and fluidity of the mixture. When the specific pulsed power of the NEMI is less than 400 MW / m ^{3, it is} not possible to significantly affect the physicomechanical properties of the mixture, and when the level of 900 MW / m ^{3 is} exceeded, the energy costs unnecessarily increase.

The proposed composition of the mixture for the manufacture of foundry molds and cores and the method of its preparation are illustrated by the following examples.

Example 1. Prepare clad quartz sand grade 5K ₃ O ₂ 03 (GOST 2138-91) using a solution of carboxymethyl cellulose (TU 6-15-1077-92) and periclase powder hardener brand (TU 2149-215-10964029-2004) in boiling a layer with a purge of warm air (temperature 60 ° C). Then the ABFC solution (TU 113-08-606-87) is introduced into the clad sand, the ingredients are mixed and samples of the molds are made, followed by their testing.

In parallel to obtain comparative data, the mixture is prepared according to the prototype. The compositions of the mixtures are given in table 1.

Table 1 Mixtures Name of ingredients The number of ingredients, wt.%, In mixtures prototype one 2 3 four 5 ABFC Solution four 2 5 8 5 5 Periclase Powder Hardener 1,5 1,2 1,2 1,2 0.8 1.7 Carboxymethyl cellulose solution - 2 2 one 2 3 Quartz sand Rest Rest

The test results of the mixtures are given in table.2. The numbers of the mixtures correspond to those given in table 1.

table 2 Mixture Test Results Indicators Test results of mixtures by composition prototype one 2 3 four 5 1. The duration of solidification, min thirty 10 fifteen twenty 22 12 2. Vitality, min 6 twenty 25 thirty 40 28 3. The tensile strength, MPa: a) after 1 hour; 0.15 0.15 0.45 0.47 0.41 0.38 b) after 24 hours 1,0 1,5 1.9 1.7 1.72 1,6 4. Knockout (residual strength), MPa 0.20 0.08 0.09 0.12 0.10 0.09 5. Shedding,% 0.06 0.04 0.01 0.012 0.019 0.01

Example 2. Prepare analogously to example 1, a mixture of composition 2 (see table 1), which showed the most rational combination of service properties (see table 2). In this case, before the introduction of the ABFC solution, it is treated with NEMI for 15 minutes. To do this, an emitter connected to the NEMI generator (RU No. 2030097, MKI N03K 3/33, KZ / 45. Shaper of nanosecond electromagnetic pulses. Belkin B.C., Shulzhenko GI, application. January 17, 1992) is introduced into the solution. The influence of NEMI on the properties of the mixture are presented in table 3.

Table 3 The effect of NEMI processing on the properties of mixtures Indicators Processing NEMI with specific pulse power, MW / m ³ 400 600 900 1. The duration of solidification, min 12 9 8 2. Vitality, min 26 24 twenty 3. The tensile strength, MPa: a) after 1 hour; 0.73 0.75 0.63 b) after 24 hours 2.6 2,8 2,3 4. Knockout (residual strength), MPa 0.08 0.06 0.05 5. Shedding,% 0.01 0.01 0.012

The impact of NEMI opens up the possibility of further improving the physicomechanical properties of the mixture, in particular, reducing the duration of the solidification of the mixture, significantly strengthening it during solidification, while maintaining an acceptable range of values of casting cores and molds improved in comparison with the prototype crumbling and knockability.

In general, the test results show that, in comparison with the prototype, the claimed composition of the mixture and the method of its preparation allow to accelerate the shaping cycle, increase the strength of molds and rods by more than 2 times, especially in the early stages of shaping, practically eliminate the crumbling of molds and rods, facilitate knockability of castings. This has significantly improved the surface quality of complex, thin-relief castings from ferrous and non-ferrous alloys.

The mixture and the method of its preparation passed industrial tests at CJSC Ural Bronze (Chelyabinsk) and OJSC AZ Ural (Miass). Given the improved set of recorded technological properties of the mixture, its universal nature, the claimed composition of the mixture and the method of its preparation can be used in almost any domestic enterprises using CTS.

Claims (3)

1. A mixture for the manufacture of foundry molds and cores, including a solution of aluminum phosphate concentrate, periclase powder hardener and quartz sand, characterized in that it additionally contains a solution of carboxymethyl cellulose in the following ratio of ingredients, wt.%:
solution of aluminoborphosphate concentrate 2-8 periclase powder hardener 0.8-1.7 carboxymethyl cellulose solution 1-3 quartz sand rest 2. A method of preparing a mixture for the manufacture of foundry molds and cores, comprising introducing a solution of aluminum phosphate concentrate into quartz sand, characterized in that prior to introducing a solution of aluminum phosphate concentrate, quartz sand is plated with a previously prepared suspension of a solution of carboxymethyl cellulose and periclase powder hardener followed by treatment of the clad sand fluidized bed with warm air with a temperature of 50-80 ° C. 3. The method of preparing the mixture for the manufacture of foundry molds and cores according to claim 2, characterized in that before the introduction of a solution of aluminum phosphate concentrate it is treated with nanosecond electromagnetic pulses with a specific pulse power of 400-900 MW / m ³ .