JPS6355384B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a self-hardening sand for manufacturing molds and cores in foundry engineering.
hardening sand). These molds and cores are
It is useful for both personal and small-scale production of medium-sized, heavy-duty castings, such as iron, steel, aluminum, and copper alloys. Refractory fillers such as silica sand, zircon; self-hardening sands for mold and core production consisting of binders - lignosulfonates and hardeners are known. Hardening agent (hardener) is 25
~98 parts by weight tricalcium aluminate
3CaO・Al ₂ O ₃ , 0.5 to 70 parts by mass of calcium silicate
0.5 to 25 parts by mass of tetracalcium alumoferrite, and 0.5 to 25 parts by mass of tetracalcium alumoferrite;
10 parts by weight of a mixture of petacalcium trialuminate. [See Soviet Union Inventor's Certificate No. 343506 International Classification B22C1/10, "Inventions, Discoveries, Industrial Designs, Trademarks" Publication No. 47, 1981 (cf. USSR Inventor's
Certificate No.343506, Int.cl.B22C1/10,
Bulletin “Inventions, Discoveries, Industrial
Designs, Trademarks” No. 47, 1981).] The active ingredient in this curing agent is tricalcium aluminate 3CaO.Al ₂ O _3. The other components of the curing agent are inert impurities and do not contain the active ingredient. Formed during the manufacturing process.The hardener (the active ingredient with inert impurities) is mixed with limestone and various alumina-containing materials such as _commercial alumina (containing approximately 98% _Al2O3 ), bauxite (containing approximately 30% containing Al ₂ O ₃ ), with additives such as china clay or alumite. To obtain a hardener with a high content of tricalcium aluminate, the Al ₂ O ₃ content must be about 98%. It is necessary to use commercial alumina. However, since commercial alumina is a valuable raw material used in the production of aluminum and abrasives, it is not sufficient to use commercial alumina in the production of hardeners. . Using other alumina-containing raw materials (bauxite, clay, etc.) with low content of Al ₂ O ₃
A hardener product with a low content of tricalcium aluminate will be obtained. To ensure the required durability of molds and cores,
It is necessary to add a large amount of hardening agent to self-hardening sand. This results in the presence of a high content of inert impurities in the self-hardening sand, resulting in low gas permeability and low fire resistance of the self-hardening sand. Furthermore, the production of this curing agent requires sophisticated process equipment to crush and homogenize the starting raw material components.
This requires the use of a rotary furnace for high-temperature calcination at temperatures of 1300 to 1550° C., as well as a grinder that breaks the sintered product obtained into particles with a specific surface area of at least 3000 cm ² /g. The aim of the invention is to overcome the above-mentioned disadvantages. The present invention provides a self-hardening sand for the manufacture of molds and cores in foundry engineering, and furthermore provides a hardening agent that is obtainable in a simple manner and is free of inert substances and is more easily available. It is possible to produce molds and cores in foundry engineering with high mechanical strength and gas permeability, and also provides an easily available hardening agent. The object of the invention is to provide a refractory filler (refractory filler).
This is accomplished by self-hardening sands for mold and core production containing fillers, lignosulphonates, and calcium aluminates. According to the present invention, the self-hardening sand is
As calcium aluminate, it contains a hydrogarnet of _the following _general formula: 3CaO.Al ₂ O ₃ . , the following component proportions (parts by mass). Refractory filler 100 Lignosulfonates 4-8 Hydrogarnet 2-5 The curing agent of the present invention does not contain inert impurities. Therefore, the content of inert impurities in the self-hardening sand can be reduced, thereby avoiding a reduction in the gas permeability and fire resistance of the self-hardening sand. Furthermore, the curing agent of the present invention has increased mechanical strength (e.g., ultimate compression strength after 24 hours curing of 20-22 Kg/
^cm2 . ) and low friability (0.15% or less). The fracture measurement method uses a cylinder-shaped mold or core sample with a diameter and height of 50 mm for 1 minute.
This is done by placing it in a perforated drum that rotates at a speed of 60 rpm. The ratio, expressed as a percentage, of the sample mass after a trial to the initial mass indicates its spalling properties. The curing agent used in the self-hardening sand of the present invention has the general formula: 3CaO・Al ₂ O ₃・XSiO ₂・YH ₂ O (wherein, X is 0.01 to 0.25 and Y is 5.5 to 5.98.)
It is a readily available material manufactured from hydrogarnet by a simple method. This material is produced in large quantities (thousands of tons) to make alumina, but it is not precious. The method of manufacturing the novel curing agent of the present invention involves washing the starting hydrogarnet with water to remove impure alkali, followed by drying at a temperature within the range of 300 to 500°C. Since the obtained curing agent has a specific surface area of 5000 to 6000 cm ² /g after drying,
There is no need to crush the curing agent after drying. Compressive strength of mold and core 1 hour after curing
With high curing speed ensuring equal to 5.0~8.0Kg/ ^cm2 ,
This hardener can be manufactured from self-hardening sand on which molds and cores are based. The self-hardening sand containing the curing agent of the present invention has a sufficiently high curing time (12-15 minutes at 18-20 °C), a large gas permeation time (up to 180 minutes) and separates well from castings. be able to. The self-hardening sand of the composition of the present invention is not excessively 35~
It can be used to make molds and cores of various shapes and sizes at a temperature of 40°C. All of the self-hardening sand components of the present invention are non-toxic and readily available. Compared to self-hardening sands based on synthetic resins, the self-hardening sands of the present invention have many essential advantages. In the method for producing self-hardening sand according to the invention, no toxic gases are released, as well as during the filling of molds made with liquid metal and during their cooling. Even if the self-hardening sand is thrown away after use, it is ecologically harmless. In terms of quantity, the main component of the self-hardening sand is the refractory filler, and the proportions of other components of the self-hardening sand are calculated based on the refractory filler. The content of lignosulfonates in the self-hardening sand is in the range of 4 to 8 parts by weight. Molds and cores produced with a content of lignosulfonates of less than 4 parts by weight have a significant brittleness and brittleness, and above 8 parts by weight, self-hardening sands have a significantly greater gas-forming capacity. The hardening agent content in the self-hardening sand is 2 to 5 parts by mass. When the curing agent content is lower than 2 parts by mass, the resulting mold and core have low mechanical strength and are significantly brittle and friable. Additionally, in amounts exceeding 5 parts by weight of curing agent, the curing life time of the self-hardening sand composition is significantly reduced and the gas permeability is substantially reduced. As is known in the art, ambient temperature has a significant effect on both the setting time and the setting rate of self-hardening sands. Therefore, as the temperature increases, the curing time of sand decreases and the curing rate increases. As already mentioned above, the hardening time of the self-hardening sand of the present invention is 12-15 minutes at 18-20°C. In many cases, this curing time may be insufficient for producing sturdy and/or irregularly shaped molds. In order to extend the hardening time of the self-hardening sand and adjust the hardening rate, water-soluble phosphates are preferably added to the self-hardening sand of the present invention in an amount of 0.03 to 0.50 parts by weight. Water-soluble phosphates include iron phosphate and/or
Alternatively, it is preferable to use manganese phosphate or tertiary sodium phosphate. The use of water-soluble phosphates in amounts less than 0.03 parts by weight is unsuitable since the curing time cannot be delayed. At amounts of water-soluble phosphate exceeding 0.5 parts by mass, the curing time is significantly retarded, resulting in mold and core compressive strengths (ultimate compressive strength after 24 hours of curing of 5-7 Kg/cm). ² or less) will be lower. In the self-hardening sand of the present invention, the refractory filler includes silica sand, zircon, chromite, olivine,
Chromomane (chromomagnesite), chromite and other materials known in foundry engineering are used. The lignosulfonates used in the self-hardening sand of the present invention include products obtained by the treatment of wood, which are widely used in foundry engineering as binders for the manufacture of molds and cores. As a water-soluble phosphate, the commonly used phosphate is
Used both individually and in various combinations, preference is given to iron and/or manganese phosphates, tertiary sodium phosphates. Self-hardening sands are produced in continuous-action or batch-type mixers. The dry components of the self-hardening sand are first mixed. That is, the refractory filler and curing agent are mixed, then the binder is added and mixed continuously for no more than 1-2 minutes. The self-hardening sand obtained is poured into a molding box or core box. Self-hardening sand initially has low durability. Therefore, it can be easily strengthened by vibration, compaction, squeezing, or other means. When adding water-soluble phosphate to self-hardening sand, the latter (water-soluble phosphate) is dissolved in advance in the binder-lignosulfonates. From the self-hardening sand produced by the above method,
The mold and core are manufactured in the usual manner used in self-hardening sand foundry engineering. In order to understand the invention even better, the following example is given below for the implementation of the production of self-hardening sand. The test results of the samples obtained are shown in the table following each example. Example 1 Self-hardening sand produced has the following composition (parts by mass). Silica sand 100 Lignosulfonates 8 Hydrogarnet 3CaO・Al ₂ O ₃・
0.01SiO ₂ .1.7H ₂ O 5 First, hydrogarnet is mixed with silica sand, then lignosulfonate is added and mixed for 1 to 2 minutes. These operations are carried out at a temperature of 18-20 ° C. The resulting sand mixture is poured into a core or mold and maintained at the above temperature. This causes curing of the mixture. The sand samples after hardening are subjected to physical mechanical tests. Example 2 Self-hardening sand produced by the same method as described in Example 1 has the following composition (parts by mass). Zircon 100 Lignosulfonates 4 Hydrogarnet 3CaO・Al ₂ O ₃・
0.13SiO ₂ ·1.5H ₂ O 2 Example 3 Self-hardening sand produced according to the method of Example 1 has the following composition (parts by mass). Chromite 100 Lignosulfonates 6 Hydrogarnet 3CaO・Al ₂ O ₃・
0.25SiO ₂・1.3H ₂ O 3 Example 4 Self-hardening sand having the following composition (parts by mass) is manufactured. Olivine 100 Lignosulfonates 7 Hydrogarnet 3CaO・Al ₂ O ₃・
0.20SiO ₂・1.4H ₂ O 4 Iron phosphate Fe (H ₂ PO ₄ ) ₂ 0.03 The self-hardening sand of the above composition is the same as that of Example 1, except that the iron phosphate is mixed with lignosulfonate in advance. manufactured in a similar manner. Additives and binders are then mixed into the olivine and hydrogarnet. Example 5 Self-hardening sand having the following composition (parts by mass) is produced. Chromite 100 Lignosulfonates 5 Hydrogarnet 3CaO・Al ₂ O ₃・
0.13SiO ₂ 1.5H ₂ O 3 Manganese phosphate Mn(H ₂ PO ₄ ) ₂ 0.50 This self-hardening sand composition was prepared as in Example 1, except that the manganese phosphate was premixed with the lignosulfonate. Ru. The binder containing additives is then mixed into the rhodochrosite and hydrogarnet. Example 6 The self-hardening sand produced has the following composition (parts by mass). Silica sand 100 Lignosulfonates 7 Hydrogarnet 3CaO・Al ₂ O ₃・
0.25SiO ₂ · 1.5H ₂ O 4 Sodium phosphate Na ₃ PO ₄ · 12H ₂ O 0.15 The self-hardening sand of the above composition was the same as in Example 1 above, except that sodium phosphate was mixed with lignosulfonate in advance. manufactured by a method. A binder containing additives is then mixed into the silica sand and hydrogarnet. Example 7 Self-hardening sand produced has the following composition (parts by mass). Silica sand 100 Lignosulfonates 7 Hydrogarnet 3CaO・Al ₂ O ₃・
0.01SiO ₂・1.7H ₂ O 4 Manganese phosphate Mn (H ₂ PO ₄ ) ₂ 0.25 Iron phosphate Fe (H ₂ PO ₄ ) ₂ 0.05 First, silica sand is mixed with hydrogarnet at a temperature of 35℃, and then Binder-lignosulfonate containing pre-dissolved phosphates of iron and manganese is injected and mixed continuously for 1-2 minutes. The sand thus produced is poured into a core or frame mold, where it is kept at a temperature of 35°C. The physical-mechanical test results of the obtained samples are shown in the following table.

Table 1 The self-hardening sands of the invention comprising the curing agents of the invention are therefore characterized by low initial mechanical strength, have the required curing time and high gas permeability. Molds and cores made from the self-hardening sand of the present invention have sufficiently high mechanical strength and low friability. By using water-soluble phosphates, the present invention allows for a wide range of adjustment of the hardening time of self-hardening sands, which is particularly important in the production of rugged and/or specially shaped molds and cores. . Furthermore, by using water-soluble phosphates, the present invention can produce self-hardening sand with a desired hardening time at ambient temperatures of 35-40°C.

Claims (1)

[Claims] 1. The self-hardening sand contains hydrogarnet having the general formula 3CaO・Al ₂ O ₃・XSiO ₂・YH ₂ O where X=0.01 to 0.25 and Y=1.3 to 1.7 as calcium aluminate. , the following component proportions (parts by mass): refractory filler 100 lignosulfonates 4-8 hydrogarnet 2-5; Self-hardening sand for core manufacturing. 2. The self-hardening sand according to claim 1, which contains 0.03 to 0.50 parts by mass of water-soluble phosphates as an additive. 3. As water-soluble phosphates, iron phosphate and/or
The self-hardening sand according to claim 2, further comprising manganese phosphate. 4. The self-hardening sand according to claim 2, which contains tertiary sodium phosphate as the water-soluble phosphate.