SU505489A1 - Binder for shell molds made using fixed models - Google Patents

Description

one

The invention relates to a foundry, in particular, to a binder for the manufacture of shell molds manufactured by permanent models.

Known binder for shell molds made by permanent models, including the molasses used in the composition of the sandy-clay mixture.

A disadvantage of the known binder is the low rate of its hot curing and insufficient binding capacity, which leads to low strength indicators of the mixture based on it.

It is also known to use for the preparation of shell forms by permanent binder models based on pulverbakelite and technical furfural. However, a known binder in the process of thermal decomposition produces toxic gases, which impairs sanitary and hygienic working conditions.

In addition, it has a high cost, which increases the cost of producing castings in cortical forms.

The purpose of the invention is to increase the rate of hot curing and the binding capacity of the fixer based on molasses.

This is achieved by the fact that the proposed binder, including molasses, additionally contains a 30% solution of nitrate

ammonium in the following ratio of ingredients (in wt.%):

Molasses 99,4-5-99,55

30% ammonium nitrate solution 0.45-0.56

To prepare the binder, a solution of ammonium nitrate of 30% concentration is introduced into the syrup with their simultaneous mixing, and after the end of the injection of the solution, stirring is continued for another 2–3 minutes. Thus prepared binder acquires thermosetting properties.

A typical mixture for shell forms with a binder in accordance with the invention has the following composition (in

weight. %

The foundation

Quartz sand Binder (modified molasses) 2.0-2.8 Example. A binder consisting of 99.5 wt. Is prepared. % molasses and 0.5 wt. % solution of ammonium nitrate 30% concentration.

Next, prepare the molding mixture, the compositions of which are given in table. 1. At the same time, the mixture of L1 1 includes EE in its composition as a binder, which corresponds to the invention, and mixture No. 2 includes in its composition a binder, which corresponds to the chosen prototype.

Components

Quartz cesok 1KO16A

Ammonium nitrate modified syrup

Molasses unmodified Molding clay Sawdust

The manufacture of shell forms of the proposed mixture was made as follows.

The metal model was lubricated with a release coating (kerosene + graphite), and then lined with a mixture; Compressing the mixture around the model was carried out with a rubber diaphragm. During - sec. After the removal of the device for compressing the mixture, the model with the model and the mold are shown. Table 1

Component consumption, weight. %

Mixture number 1

Mixture number 2

91.0

3.0 4.0 2.0

The envelope was placed in a furnace with a working space temperature of 250 ° C with a holding time of 4 minutes. After firing, the shell was removed with a special device.

from the model and went to the assembly.

The effectiveness of hot curing the shell mixture with the proposed binder, as compared to the mixture in which the binder was used in accordance with the selected prototype, is shown in Table. 2

table 2