SU1419788A1 - Parting material for ceramic moulding shells by investment pattern - Google Patents

Abstract

The invention relates to foundry. The purpose of the invention is to increase the gas permeability and heat resistance of the forms, as well as to improve the removal of ceramics from the casting, which is achieved due to the fact that the sprinkled material contains, wt%: thermolite 90-95, synthetic chrome-spinelide (CXIU) 5-10. Thermollt bulk weight is 750-1200 kg / m. Thermolite contains,%: up to 10%; ,, up to 57, f oxides of alkaline-earth metals up to 3, the rest is amorphous silica. Forms made with a dusting material have 6–3–3.8 MPa, heat resistance (residual 6 c, air cooling from 700 to) 72–75%, gas permeability at 900 ° C 2–2.3 units. , the maximum expansion of the shell at 1.15-1.4%. With a 10-second vibration, 22-27% of the ceramics remains on the casting. 2 tab. i cl

Description

00 00

The invention relates to foundry, in particular, to the manufacture of molds for. melted model m.

The purpose of the invention is to increase the gas permeability and heat resistance of the molds of olives, as well as the improvement of ceramics from castings.

Example. Thermolite was crushed in laboratory runners LB-2, subjected to sieving through a sieve 032.

Thermolite is an artificial, porous, durable and lightweight material obtained by burning at 1200–1250 siliceous sedimentary rock (flask, diatomite, tripoli), consisting mainly of amorphous silica. The bulk weight of thermolite is 750-1200 kg / m. The following components are included in the thermolite, mas.7:

OKctm aluminum 0.1 - 10.0 Alkaline-earth metal oxides 0, 1 - 3.0 Ferric oxide 0.1 - 5.0 Alkali oxides

metals 0,01 - O, A

Amorphous silicaEverything else High content of amorphous krenezem in thermolite eliminates the possibility of polymorphic transformations, which increases the strength properties of shells and their heat resistance, and the porosity of Tbzrmolite increases the gas permeability of the forms. When the thermolite is heated to 950 ° C, the linear expansion of the shell is xenopenzylated by the shrinkage of the thermolite, as a result of which the final expansion of the shell is insignificant.

Synthetic chromospinelide (CXW) is a product of thermal decomposition of magnesium chromate, aluminum hydroxide, and iron oxide.

General formula 2 MgAloO IgFe / jOjj or as oxides: 2MdO-2Cg Oy MgO-Al Oj; MgO

REAOg.

Synthetic chromospinelide in the amount of 7 wt.% Was mixed with the prepared thermolite in the amount of 93 wt.%. The prepared mixture was used as a dusting material for the second, third and fourth layers of the shell. In the laboratory conditions such a dusting material was tested.

Table 1 presents the composition of dusting material, T a b l and c a I

sosta

The content of ingredients in the samples

May,%

one

95

93

90

For each composition, 3 samples were made for testing ceramics for bending and heat resistance (loss of strength after heat removal). At the same time, several rotor castings were made, representing two bushings interconnected by blades of variable cross section.

The method of making the refractory coating is as follows.

The first coating layer was applied on an ethyl silicate binder, and quartz sand was used as the bulk material. The second layer of the coating on this silsilicate binder was sprinkled with a mixture of thermolite and chrome spinelide, the third and fourth layers of the coating were applied to the liquid glass binder with the powder of each layer with a proposed powder.

Samples and blocks were melted with hot air according to known technology and subjected to tests.

Table 2 presents the test results

Table 2

(residual

five

Strength at a static bend at 900 С, MPa

Heat resistance

3.2

3.5

3.8

74 75 72

2.3 2.1 2.0

1.15 1.3 1, 4

27 25 22

Magnesium oxide formed during the decomposition of chromium spinelide in the process of heating the molds (calcination, pouring them into metal) interacts with quartz, which is the basis of the thermolite,

MDO + SiO., MgSiUj.

The formation of new compounds, the presence of chromium oxides, aluminum in

eight

The melted coating layer contributes to the brittleness of the ceramic shells after being filled with metal, i.e. improves the separation of ceramics from castings. The higher porosity of thermolite contributes to an increase in the gas permeability of ceramic materials (}). The use of dusting material allows a 1.3–1.5 times increase in the gas permeability of the forms, the maximum loss of shell decreases almost by one and a half, the heat resistance increases by 15-20%

The mechanical cleaning of castings from kerping is improved by 2 times.

Claims (1)

Invention Formula The dusting material for ceramic molds for melted models, containing a refractory porous material, is different from the fact that, in order to improve the permeability and heat resistance of the molds, as well as to improve the removal of ceramics from the casting, it is used as a refractory porous material. material contains thermolite and additionally synthetic hromipinelid in the following ratio of ingredients, wt.%: Termolit90-95 Synthetic chrome spine lead5-10