SU900930A1 - Composition for manufacturing shell moulds and cores in heated equipment - Google Patents

Description

The invention relates to a foundry, namely, to mixtures for the manufacture of casting shell molds and the storks in a heated tooling.

Mixtures for the preparation of shell molds and cores are known, containing a refractory filler, novolac resin and urotropin 1.

These mixtures are characterized by low heat resistance due to the presence of thermal stresses in connection with the temperature difference over the cross section of the shell. This leads to the fact that the mold cracks during the pouring of the metal and there is a defect in the casting of under-filling.

Compositions for the preparation of shell forms and cores are also known, containing refractory filler, novolac resin, hexamine, and technological additives that provide high strength mixtures at normal and elevated temperatures. Additives are waxes or dispersion of them in water 2.

These additives contribute to an increase in the physicomechanical properties of the mixture, but during mold casting, they do not significantly reduce the magnitude of the thermal stresses that arise. Upon receipt of castings weighing more than 40 kg, shell molds cracked at the time of pouring the metal and a shortage of underfill metal is observed.

Closest to the proposed technical essence and the achieved result is a mixture of 3 for the manufacture of cast shell

10 forms and rods in a heated snap-in containing, wt.%: Novolak phenol-formaldehyde resin 2-7

15 Urotropin0,2-0,7

Iron Oxide 0.5-2.0 Refractory

filler Else Introduction to the mixture of oxide additives

20 iron increases the heat resistance of shell molds and cores due to the fact that in the high-temperature region the thermal conductivity and heat capacity of the mixture increase. However, with this, an increased consumption of the binder is required in order to achieve optimum strength of the shells, which degrades the quality of the castings.

The invention invented is an improvement in the thermal properties of the clad

mixtures reduce the tendency of shell molds and cores to tregcinoobrazovanie and improve the quality of the surface of ferrous castings.

The goal is achieved by the fact that the mixture for the manufacture of casting shell molds and cores in a heated snap-in, including a refractory filler, novolac phenol-formaldehyde resin, urotropin and an additive-regulator of thermophysical properties, contains Albertol acid in the following ratio of components, weight. %:

Novolacna phenol formaldehyde resin 2-7

Urotropin0,2-0,7

Llbertoleva acid 0.1-0.6

Refractory

filler Else

Albertoleic acid under the action of the heat of the cast metal ignites and burns, improving the heat transfer between the sand grains of the mixture due to convection of combustion products. Therefore, a mixture containing the addition of albertoleic acid has a high thermal conductivity. Moreover, since Albertoleic acid has a lower temperature of self-ignition, amenenia (equal to or less than 7 ° C), h; I use Fenol-formaldehyde resin (more than 1000 ° C), the temperature distribution over the cross section of the shell is characterized by a slight drop, as a result of which the thermal stresses are low magnitude. The optimum amount of additive is 0.1-0.6% by weight of sand. It provides the improvement of the whole complex of thermophysical characteristics, as a result of which the internal stresses arising during the thermal expansion of quartz are insignificant, which contributes to a reduction in the tendency of the mold to crack formation.

When the content of the additive is less than 0.1%, the effect of its use is insignificant, since the heat transfer due to convection associated with the burning of the additive is insufficient to improve the thermophysical characteristics of the shell form. When the content of the additive is more than 0.6%, the strength of the shell molds and rods is reduced in a burning state.

Albertoli is a dispersion product of phenolic resins in rosin followed by esterification of abietic acid contained in rosin with glycerol.

Albertoleic acid is introduced into the mixture either as a product obtained by chemical interaction of a phenolic resin with abietic acid, or as an inseparable mixture of albertolic acids contained in modified phenolic resins, for example, FL-326 (TU 6-10-840-75) , FL-236 (MRTU 6-05-1131-68) with the content of these acids not less than 25%.

Example. The plated mixture is prepared in the usual manner. In the experiments, novolac phenol-formaldehyde resins SF-015 (GOST 18694-73) and SF-260 (TU 6-05-232-114-77) and 1Q010B quartz sand are used. Urotropin is administered in the form of an aqueous 33% solution. The sand is heated to a temperature of 120-140 ° C and mixed sequentially, first with novolac resin, then with modified phenolic resin containing albertolic acid, then with aqueous solution of hexamine.

The compositions of the proposed mixtures 1-5 and known 6 are given in table. one.

about

Table 1

Quartz sand Novolachna resin SF-O, 15

Novolacna resin SF-260 (

Urotropin

Resin FL-326 containing 50 albertoleic acid

Albertic Acid

92.5.

95.4

2.1 94.7 5.0 7.0 4.2 3.0

0.5

0.4

0.5

0.7

1.2

0.6 0.3

0.6

Gummy residue

Resin FL-236 with a content of 30 wt.% Albertol acid

Albertoleva acid Resinous residue

Albertoleic acid

Iron oxide

The specified amount of urotropine is used to prepare a 33% aqueous solution, in the form of which it is added in the process of sand-plating.

Given in Table. 1, the compositions of the inventive mixtures 1-5 are characterized by an increasing content of albertolic acid from 0.13 (mixture 1) to 0.6% by weight (mixture 5).

The effect of the composition of sand-resin mixtures on hot deformation and the formation of cracks in shell molds is investigated by the method of one-sided heating of a rectangular sample of a mixture of 100 x 25 bg meters in size to a temperature of 950–1000 ° С loaded with a concentrated force of 250 g nii Between supports 75 mm. Obtained data Thermal conductivity, (cal / cm-hail) X 10

Temperature diffusivity, (sms) X 10 Starting deflection of specimens 100X 25 b mm, mm Duration of initial bending, s

The tensile strength of the hot state, kgf / cm As follows from the table. 2, the introduction of a mixture of albertoleic acid-65

Extension of the table. one

0.2

0.2

.2,0

They are compared with the strength properties of the mixtures measured on standard samples made with a sherathur of the working tool for 250 s and held at this temperature for 3 minutes. At the same time, to calculate the thermophysical characteristics, the temperature change over the cross section of the shell is recorded at a distance of 2.4 and 6 mm from the heater. The quality of the mixture is additionally evaluated by the percentage of reduction in the rejects for underfilling because of the cracking of the mold at the time of pouring and crystallization of the metal (HF45-5 cast iron) and the presence of surface defects on the castings in the form of tempes.

The test results are presented in Table. 2

table 2

125 126 131

138 106

40

36 37

29

0.30 0.31 0.30 0.25 0.35 22 24 21 20 32

Claims (3)

11.9 26.1 17.6 12.0. 11.0 em resistance of the shell to thermal shock by 1.5 (times (compare strength in the hot state for cr,: Eg.: 4 and b with a similar binder content). The addition to the mixture of albertolic acid is positively reflected on thermal mode of the form (thermal conductivity increases by 1.3 times, thermal diffusivity by 1.4 times.) Mixtures containing the addition of albertoleic acid have a smaller value and duration of initial backward deflection (towards the heat source), which indicates a high crack resistance these mixtures. The willow is absent on all the proposed mixtures. Plates made from these mixtures do not have surface defects in the form of sinis. Thus, the proposed mixture provides an improvement in the thermophysical properties of shell molds and cores and a reduction in their tendency to crack formation. ferrous alloys, in particular, defects of castings such as weasel are eliminated and the shortage of mold shortage is drastically reduced. Claims of the Invention A mixture for the manufacture of casting shell molds and cores in heated equipment, including a refractory filler, novolac phenol-formaldehyde resin, urotropin and an additive-regulator of thermophysical properties, characterized in that, in order to improve the thermophysical properties of the mixture, sheath coating rods for cracking and improving the quality of the surface of ferrous castings, it contains as an additive-regulator of thermophysical properties albertol acid following ratio of ingredients, wt.%: novolac phenol-formaldehyde resin 2-7 Urotropin Albertoleva acid 0.2-0.7 0.1-0.6 refractory napolnitelOstalnoe Sources of information received note in the examination, Sokolov 1. NA Shell casting. M., Mechanical Engineering, 1978, p. 48-67. 2. USSR author's certificate number 532449, cl. B 22 C 1/22, 1975. 3.Journal of the - Institution of Engineers Mining and Metallurgy Division (3ndia), 1973, 53, No. 3, c.121-122.