SU831340A1 - Method of preparing mixture for producing casting moulds and cores - Google Patents

Description

(invention. refers to the foundry and can be used for the preparation, mainly sand-resin mixtures, used in the manufacture of molds and core castings from black and colored alloys. The foundry uses molding and core mixtures with synthetic resins, especially with carbs-imide and carbamide vanes l. There is a known method of preparing sand-resin mixtures for making casting cores and molds, which before the introduction of resin and acid hardener temperature to a temperature below the boiling point of an aqueous or non-aqueous solvent included in these liquid ingredients, i.e., almost 50-90 C. This will dramatically increase the curing speed of the mixture in the tooling and the strength of the rods and molds at the initial stages solidification 2. However, this method involves the use of resin compounds within their warranty period. Urea and carbamide but-furan resins, such as UKS, KSF-1 and others, are manufactured with a warranty period of safety necessary operatio ns usually within 4560 days. Consumer plants produce synthetic resins in large batches and the processing of resins in foundries does not always meet the deadlines guaranteed by the manufacturer. Often, the duration of use of the resins of the same batch significantly exceeds the warranty period of their validity. The limitation of the shelf life of synthetic resin is due to the fact that polycondensation processes in the finished product (resin) continue to proceed constantly, albeit slowly and slowly. This leads to destabilization of the properties of the resin, the consolidation of molecular chains, an increase in viscosity, a decrease in the mobility of macromolecules and a deterioration in the distribution of the binder over the filler surface, and consequently, a decrease in the strength of the mixtures and an increase in the crushability of the forms and rods on synthetic binders. Particularly great difficulties are created with the insertion and distribution over the surface of the binder filler, for example UKS, CSF-1; with

overdue warranty period in installations in which resin is pumped through pipelines.

The closest to the proposed technical essence and the achieved result is a method of preparing a mixture for the manufacture of casting cores and molds, including sequential dosing / and mixing of the components of the mixture (refractory filler, acidic hardener and synthetic resin of polycondensation type) p}.

However, the use of synthetic resin in this method with an expired warranty period leads to a significant loss of strength and a sharp increase in the crumbling of the rods and shapes.

The purpose of the invention is to develop a method for preparing a mixture using synthetic resin with a shelf life exceeding the warranty period of its life, eliminating the loss of strength of the rods and molds and reducing their crumbliness.

The goal is achieved by the fact that according to the method of preparing a mixture for the manufacture of casting rods and molds, including sequential dosing and mixing of the refractory filler, acidic hardener and synthetic resin of polycondensation type, the synthetic resin is heated to OO-C before dosing.

Preheating the resin before being fed into the mixer reduces the viscosity of the binder, increases the mobility of the enlarged macromolecules of the resin, and distributes it evenly throughout the grains of the filler, which leads to an increase in strength and a reduction in the precipitation of the molds and rods. Preheating the resin to temperatures below 30 ° C does not significantly reduce the viscosity of the binder, and heating higher causes a partial destruction of the resin, a significant removal of the solvent and leads to a deterioration of its binding properties.

As synthetic resins of the polycondensation type, carbamide-formaldehyde, carbamide-formaldehyde-furan, phenol-formaldehyde, phenol-formaldehyde-furan, formaldehyde-furan, etc. can be used.

Example. For tests, a cold-hardening mixture is prepared, containing, wt%:

Quartz sand 96.4 Synthetic resin (UKS or KSF-1) 3.0 Sour hardener (phosphoric acid) 6.0

The mixture is prepared according to the following mode: an orthophosphoric kilot is introduced into the sand and mixed with it for 4 minutes, then a synthetic resin is introduced (without preheating or with heating, and stirred for another 0.8 min, after which the mixture is ready for use.

In tab. 1 shows the physico-mechanical characteristics of the mixture when using carbamide-furan resin KSF-1, aged for 180 days. from the time of manufacture to testing, which is 4 times longer than its shelf life.

Table 1

PrelaV table. 2 also shows the physicomechanical characteristics of the mixture using UKS carbamide resin, seasoned for 180 days. from the moment

manufacture prior to testing, which is 3 times longer than its shelf life, and at the same time goes into a completely substandard condition.

table 2

Claims (1)

Claim A method of preparing a mixture for the manufacture of foundry cores and molds, including sequential dosing and mixing of a refractory filler, an acid hardener and a polycondensation type synthetic resin, characterized in that, for the purpose of using a synthetic resin with a storage period exceeding the warranty period> eliminate the loss of strength of the rods and molds and reduce their crumbling, the synthetic resin is heated to a temperature of 30-80 ° C before dosing.