RU2022678C1 - Cold-hardening mixture to produce foundry moulds and rods - Google Patents

Abstract

FIELD: foundry. SUBSTANCE: mixture comprises 0.75 - 2.0 wt. per cent of metal oxide material (produced by crushing together magnesium oxide material and iron oxide material up to 200 - 400 m²/kg specific surface); 2.00 - 3.50 wt. per cent of acid phosphate composition; the balance being fire resistant granular filling of silicate nature. Complex metal oxide material comprises 4.0 - 30.0 wt. per cent of FeO; 5.0 - 40.0 wt. per cent of Fe₃O₄; 1.0 - 20.0 wt. per cent of Fe₂O₃; 10.0 - 90.0 wt. per cent of MgO. EFFECT: increased quality of moulds and rods due to their increased elastic-plastic properties. 2 cl, 4 tbl

Description

 The invention relates to foundry, and in particular to compositions of cold-hardening mixtures for the manufacture of foundry molds and cores.

 A known mixture for the manufacture of foundry molds and cores containing a binder (50% phosphoric acid and 50% metallurgical dust - a waste from steelmaking in electric arc furnaces) and quartz sand. This mixture has a survivability of 7-15 minutes, gas permeability of 100-500 units. and compressive strength after 24 hours, 1.8-3.5 MPa [1].

 A self-hardening mixture for the manufacture of foundry molds and cores is also known, containing a material based on metal oxides with a valency of 2 (for example, based on magnesium oxide, concentrated phosphoric acid, sulfite-yeast mash, glycerin and a refractory filler. This composition allows to obtain mixtures with a survivability of 8- 12 min, low crumbling, tensile strength at the final stage of curing 0.5-1.2 MPa [2].

 However, insufficient strength at the initial stage of curing and increased fragility of these mixtures do not exclude the possibility of cracking when removing complex rods from a core box.

Closest to the invention in technical essence and in combination of features is a cold-hardening mixture for the manufacture of foundry molds and cores, including ingredients in the following ratio of components, wt.%:
Alumochromophosphate binder 4.0 ... 6.0 Iron oxides 3.0 ... 4.0 Marshalit 4.0 ... 6.0
20% aqueous solution
ammonia (in terms of NH ₃ ) 0.1 ... 0.3
Refractory filler
based on silicon dioxide Else [3].

 However, molds and rods made from a mixture of this composition have low plateauity at all stages of curing; increased brittleness of the mixture can lead to the formation of cracks in the rods and molds and, consequently, to the deterioration of their operational properties. In addition, a 20% aqueous ammonia solution introduced as a hardening catalyst by dispersing it in an air stream, in other words, ammonia-air purging of the mixture in order to increase the strength of the mixture and its curing rate, can contribute to the deterioration of sanitary and hygienic working conditions and environmental conditions in the shop. The disadvantages of the mixture should also include a relatively high content of the main components of the cold-hardening iron-phosphate mixture, compared with the inventive mixture: aluminochromophosphate binder 4-6 wt.% And iron oxides 2-4 wt.%.

 The purpose of the invention is to improve the quality of molds and rods by increasing their elastoplastic properties.

 The cold-hardening mixture according to the invention contains magnesium iron oxide powder as a complex metal oxide material.

Obtaining a complex metal oxide material is carried out by co-grinding the magnesium oxide and iron oxide materials to a specific surface of 200.. . 400 m ² / kg, while the ratio of the mentioned materials is taken respectively as (90 ... 10): (10 ... 90).

 Grinding of materials can be carried out in a ball mill, vibration mill, disintegrator and other types of equipment.

As iron-containing material can be used iron oxide, waste steelmaking, waste converter production, trifolin, crocus, magnetic black powder, iron ore concentrate. As the magnesium-containing material may be used magnesite, calcined at a temperature higher than 1500 ^{° C,} to which the metallurgical (sintered) magnesite (GOST 24862-81) and fused magnesite.

 The introduction of complex metal oxide material in the mixture in an amount of less than 0.75 wt. % determines the low strength of the molds and cores at all stages of curing, and its introduction in an amount of more than 2.00 wt.% leads to a sharp decrease in the survivability of the mixture, its ductility and possible softening of the molds and cores after 24-48 hours of hardening.

As the acidic phosphate compound in the mixture, phosphoric acid (GOST 10678-76) with a density of 1400-1600 kg / m ³ can be used; aluminophosphate binder containing, wt.%: P ₂ O ₅ 42.0 ... 45.0; Al ₂ O ₃ 10.0 ... 12.0; H ₂ O - the rest; alumochromophosphate binder containing, wt.%: P ₂ O ₅ 42.0 ... 45.0, Al ₂ O ₃ 8.0 ... 10.0, Cr ₂ O ₃ 3.7 ... 4.5 , H ₂ O - the rest and others. The acidic phosphate compound is proposed to be introduced into the mixture in an amount of 2.00-3.00 wt.%. The introduction of a mixture of acidic phosphate compounds in an amount of less than 2.00 wt.% And more than 3.50 wt.% Leads to a decrease in strength at the final stages of hardening.

 Refractory granular filler of silicate nature can be quartz, distensillimanite, zircon sands, etc.

 Mixtures were prepared as follows.

 A silicate refractory granular filler of nature was mixed in a batch laboratory vane mixer with complex metal oxide material. The mixing time was 1.0-1.5 minutes. An acidic phosphate compound was then introduced and stirring was continued for 1.0 min.

 Standard samples with a diameter and a height of 50 mm were stuffed from the obtained mixture by known methods to determine survivability, compressive strength, deformation, and shedding.

 The compositions of the mixtures are presented in table. 1 and 3, their properties are in table. 2 and 4.

 From the test results it follows that the mixture according to the invention provides an improvement in the quality of molds and cores by increasing the elastoplastic properties.

 Molds and cores made from the mixture according to the invention can be used for steel, iron and color casting in mass, large-scale and individual production.

Claims (2)

1. COLD HARDENING MIXTURE FOR THE PRODUCTION OF CASTING FORMS AND RODS, comprising a powdery iron-containing material, an acidic phosphate compound and a refractory granular filler of a silicate nature, characterized in that, in order to improve the quality of the molds and cores by increasing their elastic-plastic properties, it comprises a complex metal oxide material having a specific surface area of 200 - 400 m ² / kg, obtained by grinding own magnesium oxide and iron oxide of materials taken in the ratio of (10 - 90). (90 - 10), with the following ratio of components, wt%:
Complex metal oxide material with a specific surface area of 200 - 400 m ² / kg 0.75 - 2.00
Acidic phosphate compound 2.0 - 3.5
Refractory granular silicate filler nature Else. 2. The mixture according to claim 1, characterized in that the complex metal oxide material with a specific surface area of 200 to 400 m ² / kg contains, wt.%:
Iron oxide (2+) FeO 4 - 30
Iron oxide (2+, 3+) Fe ₃ O ₄ 5 - 40
Iron oxide (3+) Fe ₂ O ₃ 1 - 20
Magnesium Oxide MgO 10 - 90

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