SU984624A1 - Mixture for producing shell casting moulds and cores in heated equipment - Google Patents

Description

(54) MIXTURE FOR THE MANUFACTURE OF CASTING ENVIRONMENTAL FORMS AND RODS IN A HEATED TOOLING. 1 The invention relates to a foundry, namely, mixtures for preparing casting shell molds and cores in a heated tooling. Mixtures for the manufacture of casting shell molds and cores are known, which contain technological additives that change the properties of the binder and, accordingly, the sand-resin mixture in a given direction. Thus, the addition of glycerol or glycol ester of rosin Cl or albertoleic acid 2 has the best effect and increases the resistance of the mixture to thermal shock, but does not accelerate the flow of the shell to form and cure. The addition of alkylreasphine formaldehyde resin Cz improves the strength characteristics of the mixture, contributes to its faster curing at lower energy costs, but poorly plasticizes the mixture. For these known technological additives, it is characteristic that they solve the problem of improving the technological properties of a molding sand mixture in part and do not solve it in a complex. Closest to the proposed technical essence and the achieved result is a mixture for the manufacture of stump-shaped forms and stern in a heated snap-in, containing, wt.%: Phenopformaldehyde HaSa novolac resin1-8 Epoxy resin with aromatic fragments0, O2-4, OO Urotropin0,14 -1,36 Refractory fillerErestal As an epoxy resin with aromatic fragments, for example, the reaction product of bis-phenop A with epichlorohydrin, obtained in the presence of caustic soda, is used. Epoxy coatings, which are used as a special additive in amounts of 0.02-4.00%, act as active softeners in the sand clad with novopak. This leads to high resistance of the mixtures to the effects of thermal shock 4 1. However, an increase in the plastic properties of the mixture (plasticization) leads to a simultaneous decrease in the strength properties. In addition, in order to ensure the required strength of the shell forms and cores in the described known mixture, the amount of hexamine, at least 14%, based on the weight of the novolak, is necessary. This leads to the abandonment of gas porosity castings due to the intensive decomposition of excess hexamine at elevated temperatures with release of ammonia. The purpose of the invention is to achieve a simultaneous combination of increased rates of hot curing, strength of molds and rods and their high resistance to thermal shock due to Spinning (} cation during high-temperature heating and reduction in the degree of metal elevation with nitrogen. To achieve the goal, the mixture for the manufacture of shell forms and rods in heated equipment, including a refractory filler novopachnuyu phenol-formaldehyde resin, hexamine and technological additive based on epoxy resin As aforementioned additive, it contains epoxy aliphatic resin in the form of epoxidized glycidyl esters of glycoy in the following ratio of ingredients, wt.%: Novolac phenol formaldehyde 2-7 O, 16-0.7 O Urotropin Epoxy resin, OO4-O, 14O chesca epoxy aliphatic resins are epoxidized glycidyl glycols (triethylene glycol diethylene glycol). They have a viscosity, low molecular weight (250-350), a narrow limit of the content of epoxy groups (24-30%) . Epoxy resin containing active functional groups and introduced into the mixture in the amount of 0.004-0.140 weight. catalyzes the cessation of phenolic resin curing with urotropin, but poorly plasticizes the clad mixture. Sandy resins on a mixture containing the components in the specified amounts form, upon exposure to high temperatures, a crosslinkable composition that is characterized by optimally stable properties. The time interval for the curing of the phenolic resin in the presence of an epoxy aliphatic resin is narrowed (25-30 seconds instead of 40-13 ° C), which results in uniform curing of the mixture over the cross section of the shell with less consumption of hexamine. This leads to the stabilization of the operational characteristics of automatic molding lines and increase their reliability. When the content of the additive is less than O, 004 wt.%, The effect of its use is insignificant, the castings are affected by gas porosity due to the forced content of hexamine. When the content of the additive is more than 0.14%, the plasticizing effect of the additive begins to predominate over the stabilizing one, and the epoxy aliphatic resin acts as a softener, which increases the resistance of the mixture to thermal shock, but does not increase the strength of the rods and shapes. When the content of urotropine is less than 0.16 wt.%, The strength of shell forms and rods in a hot condition is insufficient (less than 11.0 kgf / cm), and when the content of urotropine is more than O, LLP wt.%, A defect of gas porosity occurs. Resins of the following types: DEG-1, TEG-1 (TU 6-05-182377) can be used as an epoxy aliphatic resin, and the epoxy resin can be introduced either directly into the mixture or as a binder. In the latter case, the required amount of epoxy resin is introduced into the phenolic resin after it is melted or after the end of the drying process of the novolak, and the mixture is heated at 160-18 ° C until a homogeneous mass is obtained. Example. The plated mixture is prepared in the usual manner. In experiments, novolac phenophormaldehyde resins SF-O15, SF-012, (GOST 18694-73) and quartz sand of brand 1KO1OB are used. Urotropin is administered in the form of an aqueous 33% solution. The sand is heated to 140-150 ° C and shifted with Novolac resin, then the mixture is introduced into the mixture.

5984624 "

epoxy-asyptic resin, then iiofl-tion is carried out in the same way as urotropine solution, zom.

In the case of using the mod and mixture 5 according to the prototype are given

bath novolac resin plaky- $ process in tab. one.

The compositions of mixtures 1-4 according to the invention

Table 1

Quartz sand 96.216 97.81 1K01OB Newest resin 3.5OO SF-O15 Novolacna resin SF-012 Urotropin (on dry iron ore, 28O 0.16 x substance) Epoxy-adipate resin 0, OO4 O, OZ DEG-1 Epoxy-aliphatic resin 0, OO4 O, OZ DEG-1 Epoxy-aliphatic resin 0, OO4 O, OZ DEG-1 Epoxy-aliphatic resin 0, OO4 O, OZ DEG-1 Epoxy resin with aromatic fragments As the epoxy resin with aromatic fragments in mixture 5, a 3-O4KR resin (TU 6-1O-12-4-77) was used, which is a 4% solution in ethyl alcohol solo of the epoxy resin obtained during the condensation of diphenylolprszhana in a silk environment with epichlorohydrin. The effect of the composition of sand-smog mixtures on a stable one. their technopsy properties are evaluated by studying the kinetic regularities of the sand-resin mixture curing process. The kinetics of the nptv curing process is studied according to the strength of the samples in a hot state at the temperatures of the model equipment of 200 N 25 OC and different sintering times of the samples (1, 2, and 3 min). In addition, the degree of curing of the binder by amount of prepolymer, op2, OO6O92.16 95.15 7, OO4, OO 00 0.70 O, 8O 32 08 ° chemically by means of extraction is carried out by means of Soxhlet apparatus. The quality of the resin and its scattering to the metal saturation with nitrogen with the formation of defects in the body of the casting of gas gas defects are evaluated on the basis of nitrogen in the surface layer of the casting technopolyne1 sample with a diameter of 1OO mm. The quality of the binder is evaluated by the time of gelation, which is determined in accordance with GOST 18694-73. The operational stability of automatic molding lines is assessed by the production of molds suitable for casting, while the minimum is estimated to the maximum possible production of molds under specific operating conditions. The test results are presented in taba. 2,

984624

Tensile strength, kgf / cm,

with and exposure time; min:

12

at 25 ° C and holding time

7.84.9

12

16.511,3

21.612,7

at ZOO C and time of the lid; min: Degree of solidification of the binder,%, in the shell thickness, mm: 9О1ОО 0-5 8895 5-1О 8693 1О-15 Gelation time 25-30 28-32 binder, with The value of the initial deflection, O, 37 OZO during heating , mm, Duration of thermal stress, with nitrogen content in process 0, OZ 0.02 sample,%

8 Table

4.9.

7,8

1O, 2 13.7

18.3

5.16.2

17,818,2

23,725,5

13.7

17.8 17.0 23.7 O 96 95 30 25-30 30-120 O, 38 0.42 O, 34 O, 02 0.03 O, O7

When comparing the achieved level of properties, mixtures should be compared with an equivalent content of the lowest state (mixtures 3 and 5 in Table 2),

As can be seen from the table. 2, the mixture according to the invention provides a simultaneous combination of increased rates of hot curing (which follows from a reduction in the gelatinization time of the binder), durability of the molds and rods and their high resistance to thermal shock due to the plasticity of the CRC of the mixture during high-temperature heating (which follows from an increase in the initial sample size of the sample during heating and from a decrease in the duration of thermal stress).

The additive to the epoxy aliphatic resin mixture is favorably reflected in the quality of the castings. Ball samples made from these mixtures | had in the surface layer of 2.6-4, O times the lower nitrogen content compared with the prototype. Thus, a reduction in the degree of saturation of the metal with nitrogen is achieved.

Due to the noted advantages, an improvement in the quality of ferrous castings is achieved, in particular, defects of castings such as gas porosity are eliminated.

Claims (4)

1. USSR Author's Certificate No. 831334, cl. B 22 C 1/22, 1980. 2. USSR author's certificate in Mg 2935509 / 22-02, cl. B 22 C 1/22, 198O. 3. USSR author's certificate for application No. 3224547/22-О2, cl. B 22 C 1/22, 198O. 4. The patent of Germany No. 2543055, cl. In 22 С 1 / ОО, published. 1976.