JPS6124097B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating mold that has a large anti-seizing effect. Conventionally, for casting molds, it has been necessary to prevent molten metal from penetrating into the voids between the sand particles that form the mold, preventing sand from falling off when the mold is disassembled, and to maintain a good casting surface. A mold is applied with the aim of obtaining a cast metal with a In conventional coating molds for cast steel, phenolic resin or collophonium (natural rosin) is usually used as a binder, and alcohol is used as a solvent, and these alcohol-based coatings are applied by brushing or spraying onto the mold surface. be done. Phenol resin and colophonium, which are used as binders in conventional coating molds, have a coating thickness of 1.0 mm.
These resins can be applied fairly thickly, up to almost 300 ml, and are excellent in ensuring the strength of the coated mold at room temperature after application. However, these resins have insufficient heat resistance, so when casting molten metal, especially cast steel, Cracks occur in the coating film, making it easy for molten metal to infiltrate, and because conventional coatings have low permeability into the mold, the effect of closing the gaps between sand particles by the coating is small, and as shown above, the molten metal can easily penetrate through the coating layer. Since the molten metal easily penetrates into the gaps between the sand particles in the mold, the anti-seizing effect is insufficient. The present inventors have conducted extensive research in order to provide a coating mold that has a sufficient anti-seizing effect against the above-mentioned molten metal-induced seizing. Considering that it is most necessary to fill the gaps between sand particles, we use a coating that is easy to form a sintered layer with excellent permeability as an undercoat, and apply conventional coatings on top of that to make it easier for the sintered layer to separate from the casting surface. The present invention has been achieved by applying a coating mold containing an organic resin, which has been used since then, and applying a double coat of coating molds each having a different role. The undercoat mold in the present invention uses as a binder an ethyl silicate hydrolyzed solution that forms a silica component with excellent heat resistance and high temperature strength. The ratio of the base material and the diluent containing the binder in the coating mold is adjusted so that it is easy to fill, that is, the coating penetrates 2 mm or more from the mold surface.
The content is 50 to 90% by weight, and the diluent is 50 to 10% by weight. After various studies, it was determined that the penetration depth of this undercoating mold should be at least 2 mm or more, but the more base materials there are in the coating mold, the shallower the penetration depth of the coating mold becomes, so it should be kept to 90% by weight. On the other hand, there is a need
As the percentage of the base material decreases, the permeability improves, but the workability during application, especially the elongation of the coating mold during brush application, decreases, so the lower limit of the base material is set at 50% by weight. As the base material, zircon powder, alumina (Al ₂ O ₃ ), spinel (MgO.Al ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), etc. are used. As the binder in the diluent, an ethyl silicate hydrolyzate that forms a silica component is used as described above, and colophonium (natural rosin) is used to maintain the suspendability of the coating mold and reduce sedimentation. Added. Silica content: 0.15 from the viewpoint of preventing gelation of the ethyl silicate hydrolyzed solution, prevention of sedimentation of the coating mold, and prevention of gas defects during pouring.
~0.75 wt%, Corophonium 0.5-2.5 wt%
It was found that a material with a silica content: colophonium ratio of 3:10 was particularly good. As the solvent, alcohols such as ethyl alcohol, isopropyl alcohol, and butanol are used as the main solvent, and to this, ethyl acetate, butyl acetate, ascent, toluene, etc. can be added as a co-solvent. For the topcoat mold, it is sufficient to use the mold that is normally used, but it is better to use one that can be applied thicker to the mold surface compared to the undercoat mold so that the undercoat mold sintered during the main melting can be easily separated from the casting. It is suitable to use an organic resin binder such as phenol resin or colophonium as a binder (the ethyl silicate hydrolyzate contained in the above-mentioned undercoat type binder is not included) and alcohol as a solvent. and
Bentonite or the like may also be added to ensure the preservability (suspendability) of the coating mold. Corophonium has both a caking effect and an anti-sedimentation effect on the coating base material, and it acts as an anti-settling effect in the undercoat type where the base material tends to gel, and in the top coat type that does not contain materials that easily gel. It utilizes caking effect. The coating mold for molds of the present invention is effective in preventing penetrating seizure that tends to occur when casting ferrous and non-ferrous metals, and the molds can be green molds with bentonite as a binder, phenolic resins, etc. It is suitable for a variety of molds, including shell molds that use organic resin as a binder, cold boxes that use phenol resins and polyisocyanate resins as a binder, and molds that use organic resins as a binder, such as linokure molds and pebble molds. In particular, it is a coating mold suitable for flan molds, which have been widely introduced as molds for casting steel in recent years because sand can be easily recycled and recovered. The accompanying drawing shows a cross-section of a mold coated with the coating of the invention. The mold is composed of sand particles 1, and the undercoat mold 2 has excellent permeability, so the topcoat mold 3
It penetrates into the gaps between sand particles to a depth of about four times the layer (more than 2 mm) and fills the gaps between sand particles. Example: Furan resin mold (100% silica sand, 1.0 furan resin)
%, para-toluenesulfonic acid was added as a catalyst to the furan resin at a rate of 40%), and the coating molds of Examples 1 and 2 shown in Table 1 were applied as undercoat molds to a penetration depth of approximately
It was applied at 2.5mm and 4.0mm and dried by ignition. Any method can be used to dry the undercoat mold, but with this ignition drying method, the topcoat mold can be applied immediately, which shortens the coating process, and the remaining heat from ignition drying can dry the topcoat mold. Time is reduced.

[Table] Next, use the coating type shown in Table 2 as the top coating type.
Cast steel (SC 42) was cast at 1570°C with a coating of 0.3-0.5mm.

[Table] As a result, in both Examples 1 and 2, in the case of castings with a casting weight of up to 1000 kg, no penetrating seizure occurred at all, and the mold release of the sand was very good. When the cast weight exceeds 1000 kg, increasing the penetration depth to about 4 mm as in Example 2 resulted in a more stable anti-seizure effect.

[Brief explanation of the drawing]

The accompanying drawing shows a cross-section of a coated mold according to the invention.

Claims (1)

[Claims] 1 The first layer contains 50-90% by weight of the base material and 50-10% by weight of the diluent.
an ethyl silicate hydrolyzate in which the diluent acts as a binder and precipitates 0.15 to 0.75% by weight of silica; 0.5 to 2.5% by weight of colophonium;
and the remainder alcohol, an undercoat layer formed by permeating an alcohol-based coating mold from the mold surface, and on top of that, a second layer containing an alcohol-based coating containing an organic resin binder and not containing an ethyl silicate hydrolyzate. A coating mold that consists of two types of coating layers: a top coat coating layer and a coating coating layer.