DE889687C - Process for the production of casting molds - Google Patents

Description

Method of making casting molds The invention relates to a Process for the creation of casting molds, in which the model of a hardening .Layer, e.g. B. of glue or oil soaked sand, cement sand or the like. Surrounded and this layer is then backfilled. For backfilling, the one in Formerei also uses molding sand that is otherwise used, which is clayey and in the usual Way, e.g. B. is tamped down by compressed air tools. This is the one in the hearth and box forming when a hardening layer is used.

In contrast, the invention now proposes a correspondingly thin formed hardening layer on one of the form the strength-imparting filler layer from practically sound-free; Sand, e.g. B. silver sand, river sand, quartz sand, slag sand or to support pit sand. The practically clay-free sand has the property, even by low pressure, e.g. B. by pressing with the hand or with the foot, practically in the state of final compression, convertible to, in which he also one :! no longer yields to high casting pressure. He's standing. in contrast to that. to the clay-containing molding sand, which can only be obtained through considerable tamping with special Tools can be sufficiently compacted. On the recognition of this difference and its utilization, the new molding process is built up.

The use of practically clay-free filler sand. is for cement molds : has already been proposed, i.e. for forms that are boxless and consist of a continuous Cement bodies are formed. The walls of such a cement mold need just because of the stresses and strains involved in transport, be so strong that you can be alone without it Support by the filling sand are able to withstand the casting pressure. It should the clay-free sand in the known cement forms only incompletely fill the cavities fill in to achieve a certain flexibility of the shape.

In the invention, the clay-free filler sand is actually the load-bearing one Layer of box or hearth shape. If necessary, it can be combined with rauni: filling, large-story, porous lightweight stones are processed. The model is initially surrounded in the usual way with the hardening layer, for example cement sand. Then the clay-free filler sand is shoveled up in layers from about 20o to 3001m height and pressed something by hand or something is kicked into it. The pounding of the clay-free sand is not only superfluous, but also not feasible when the dense sand would only give way in an undesirable way. -Wait from lifting the model up to the incrustation of the model sand layer, 'This is how relatively dry, i.e. trickling, clay-free filling sand can be used Find. However, this wait is not required unless one is required to fill out the Moist, clay-free filler sand is used between the spaces. It is malleable and possesses Sufficient stability to be encrusted after removing the model or hardening of the model sand layer to allow even high mold walls to remain true to size. Even with this premature lifting of the model out of the not yet solidified Model sand can be used to achieve flawless casts. The hardening model sand layer can be kept relatively thin from top to bottom even with larger shapes, because the actual load-bearing layer is the filling sand. This is particularly evident also by the fact that at. artificially attached small openings in the Modellsandschi.cht the liquid iron only penetrates to the filling sand and does not find any cavities, in which it could widen.

In the manufacture of cast manganese steel, molds with a Model surrounding layer of cement and aluminum compounds and stamped Backfill made of cement sand. incidentally been suggested for forms with lesser Strength, especially for cores, cement sand @ backfill mass through, green sand, to replace dry sand, or ash. The present procedure, through application of soundless. It is not possible to achieve highly pourable forms with unstamped sand reveals, ° in particular the knowledge of the causal connection between the freedom of sound and the dimensional stability as well as the saving of stamping work.

Compared to the one previously in the box and. Hearth molding with hardening The methods used for modeling sand have the following advantages: r. The stamping of the forms not necessary. The usual press equipment can be saved; aside from that the avoidance of ramming results in a significant reduction in molding times achieved.

2. The models can be produced in lightweight construction, as except No special demands are made of them due to the lack of accuracy. The digging of the models from the unbonded form takes place without any force. The sand parts stored in any unevenness on the model are due to the low shear strength of the material is sheared off without damaging the mold wall. The models are also relieved of the stresses caused by tamping.

3. As a result of the ease of use, you can even manufacture difficult forms unskilled workers are used.

q .. The clay-free sand has a significantly greater gas permeability than the molding sand.

5. The usual emptying of the pieces with the help of heavy hammers, that Knocking out and digging is completely avoided. The emptying happens without any significant effort and the molding boxes will be accordingly largely spared.

6. There is only one basic material left in the molding and core making shops, the practically clay-free sand to use.

7. The entire sand preparation is omitted because of the shape Sand that fell out after casting was done by coarse screening of the encrusted sand Model sand needs to be separated in order to be usable again immediately after moistening to be. If abrasion of the encrusted model sand gets into the filler sand, this is the case irrelevant as the basic material is the same. New sand is only essential in part less necessary than before.

The elimination of the compressed air rammers and the entire sand preparation plants, the effortless emptying of the molding boxes and the extensive use of auxiliary staff represent radical changes and progress.

For the new process it is essential that almost pure quartz sand is used Is used, especially without the addition of fluorspar. Sands with minor Additions of around 1 / s to 3/4% clay can still be regarded as practically clay-free , although these clay admixtures are not desired and in the example specified sands are also not included. The usual molding sand, however, contains generally not below 3% clay.

Claims (4)

PATENT CLAIMS: e.g. Process for the production of casting molds by means of a hardening one surrounding the model, which alone cannot withstand the casting pressure Layer that is backfilled with sand, characterized in that, practically clay-free Filler sand, e.g. B. silver sand, river sand, quartz sand, Slag sand, Pit sand, poured around the mold layer to absorb the casting pressure, however is not stamped, but at most pressed on. 2. The method according to claim i, characterized in that when using moist, practically clay-free filling sand the model is excavated before the model sand has hardened. 3. Procedure according to claim. i, characterized in that in addition to the, practically clay-free filling sand porous lightweight building blocks or pieces thereof can also be used for backfilling. 4th Method according to claim i, characterized in that after the casting the from the The sands that fell out were simply sieved off and moistened and the fine ones Parts (filler sand) supplied for further use as filler without preparation will. Cited publications: German Patent No. 715 5, o6; U.S. Patents No. 2,144,532, 2,144,532, 2,169,385; Foundry Trade Journal, 1938, p. 521 to 525; "The Foundry," 1935, p. 60. "Die Gießerei", 1936, pp. 384 to 386.