FI64525C - SAETT ATT FRAMSTAELLA EN GJUTKAERNA ELLER -FORM AV KORNFORMIGAOCH / ELLER FIBROESA MATERIAL - Google Patents

Description

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Patant- och regi * ter * tyral «an '' Amökan utlagd och utl.« Ttr »ft * n publlc« r »d 31.08.83 (32) (33) (31) etuolkuu * —Begird priorftet 21.12.78 Ο7. Ο9.79 Sweden-Sweden (SE) 781319 ^ -3 7907 ^ 50- ^ (71) Ahlsell IR AB, 27 Rannnarbyvägen, S-IOU 60 Stockholm, Sweden-Sweden (SE) (72) Ingemar Ahlandsberg, Värmdö, Lars- Erik Petersson, Södertälje, Sweden-Sweden (SE) (7 * 0 Berggren Oy Ab (5 * +) Method for making a casting core or mold from granular and / or fibrous materials - Satt att framställa en gjutkärna eller -form av kornformiga och / eller fibrosa The present invention relates to a process for producing a casting core or mold from granular and / or fibrous materials using sodium silicate or potassium silicate as a binder.

Sodium or potassium silicate, hereinafter referred to as alkali silicate, has long been used as a binder in the manufacture of molds and cores, e.g., from sand in the foundry industry. The molds and cores are then cured at room temperature by means of cures mixed with them or by blowing CCl 3 through them. However, such fabrication requires a relatively high binder content to achieve sufficient strength. In addition, the use of alkali silicate as a binder causes a number of other disadvantages, in particular: - deterioration of the fire resistance of the molds and cores - poor decomposition of the molds and cores after casting - low recovery of the spent core and mold material (casting sand).

These disadvantages have so far limited the use of alkali silicate in the manufacture of molds and cores.

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The cores are prepared by using organic binders, usually resins, by mixing a substance which acts as a hardener (e.g. an acid) and also by heating the core boxes or cores to a temperature of 250-300 ° C. Cores made in this way cause strong gas evolution both in the manufacture of the core and in the subsequent casting and are harmful to the environment of such a foundry. In addition, this type of core manufacturing consumes quite a lot of energy.

The object of the present invention is to reduce said disadvantages. The invention relates to a process for preparing a casting core or mold from granular and / or fibrous materials using sodium or potassium silicate as a binder, the invention being mainly characterized in that a surfactant is added with stirring and the core or mold is heated to 110-180 ° C. temperature.

Thus, when a surfactant is added to the mold material according to the invention and the core or mold is heated to a temperature of 110-180 ° C, the amount of alkali silicate added can be reduced compared to the prior art without compromising the strength and surface hardness of the mold or core. This allows the molds and cores to continue to be handled and stored without difficulty, and the cores also satisfactorily withstand heat and mechanical stress during casting. Due to the low alkali silicate content, the decomposition after casting is quite good. In addition, the casting is environmentally friendly, as gases harmful to health are generated only to a small extent. In the manufacture of the core, the radiant heat is reasonable and the energy consumption is low, and due to its speed, the method primarily enables serial production of the cores.

To the substance to be bound in the mold or core is added a relatively small amount of liquid alkali silicate, the ratio (molar ratio) SiO 2 / Na 2 O = 0.5-3.5, and a surfactant in the form of silicone oil, silicone emulsion or siliconate.

In order to keep the amount of binder as small as possible and to achieve the best possible decomposition after casting, e.g. sodium silicate is used with certain additives 3 64525. These are: a) Surfactants such as surfactants *, silicones (oils, emulsions) or siliconates (e.g. Berol 309¾ Rhodorsil E55® and Tegosivir®, respectively).

(b) Disintegrants and surface hardeners in the form of sugar derivatives, which have normally been treated in such a way that they remain stable in sodium silicate solution.

The invention is described in more detail below as exemplary embodiments of the invention, in which case it should be noted that the usual amount of alkali silicate, based on the amount of sand, is 3-5% or more.

1) A mixture was prepared containing sand and 1.5% sodium silicate (ratio 2.7) based on the amount of sand and 0.015% silicone emulsion (35%). Cylindrical specimens with a height of 50 mm and a diameter of 50 mm were prepared from this mixture. The test pieces were cured at 150 ° C and pressure tested after cooling. This gave compressive strengths of 500-600 N / cm. The blank test without the addition of silicone gave 2 compressive strengths of only 80-90 N / cm.

At a sodium silicate content of 2% and a silicone emulsion content of 0.02%, compressive strengths of about 800 N / cm 2 were obtained, with a blank test giving a result of about 550 N / cm 2.

2) The core box was heated to 150 ° C in a core blowing machine in a car accessories foundry. The core mass was made from sand (average grain size 0.25 mm) and 2.5% binder as described above. The machine was filled with core mass and the core was blown at a pressure to obtain a good degree of compaction, usually 400-700 kPa (4.7 kg / cra2). The cores were heat cured in the box for 20-60 seconds depending on the thickness (10-50 mm), after which they were ready for casting.

3) Core preparation was performed as above. However, the cores were now thicker, which is why warm air (110-150 ° C) was also blown through the core box. In this way, it was possible to produce perfect Keer nois in less than 60 seconds.

4) The preparation of the chemistry was performed according to 3).

However, the warm air was replaced here with CO 2 gas. Also in this way it was possible to produce flawless cores. This has not previously been possible with the above-mentioned alkali silicate concentrations.

5) The boils were prepared according to 3), but some of the warm air had been replaced with CO 2. Absolutely good Keer no was obtained.

6) The cores were prepared according to 4). Here, however, the binder consisted of 3% by weight of pure sodium silicate 49 ° Βδ, a ratio of 2.7 and 1% of a sugar derivative, i.e. the total amount of binder was 4%. The cores received good surface hardness. However, the decomposition after casting is slightly worse than in the above-mentioned sections 2), 3) and 4).

7. The cores were prepared according to 3) but with the addition of 7-10% of a standard type ester hardener. This allows the core to dry faster, which is important in the manufacture of larger molds / chemodes.

Experiments have shown that the concentrations of surfactant should not exceed 0.1% by weight of the substance, and should preferably be 0.0001-0.1%.

Claims (8)

5,64525 A process for preparing a casting core and a mold from granular and / or fibrous materials using sodium silicate or potassium silicate as a binder, characterized in that sodium or potassium silicate is added to the mixture 1-3% by weight, the surfactant being added up to 0.1% based on the weight of the substance and that the core or mold is heated to 110-180 ° C. Process according to Claim 1, characterized in that the surfactant is a surfactant, a silicone oil, a silicone emulsion or a siliconate, in particular a silicone emulsion, which is mixed with a binder and that the mixture of the substance and the binder remains stable. Process according to Claim 1 or 2, characterized in that a core box is used which is heated to 110 to 180 ° C. Method according to one of Claims 1 to 3, characterized in that warm air with a temperature of 110 to 180 ° C is blown through the core. Method according to one of Claims 1 to 3, characterized in that CCl 2 is blown through the core with or without the use of a supplementary purge with warm air. Process according to one of the preceding claims, characterized in that the molar ratio of sodium or potassium silicate is 2-3. 1. Sät att framställa en gjuterikärna eller form av kornfor-miga och / eller fibrösa material med sodium sodium silicon or potassium silicate som bindemedel, kännetecknat av att sodium sodium potassium silicate , that the active weight is set at a rate of 0.1% by weight of the material, and then the core or form is heated to between 110 and 180 ° C.