Cold setting sand for foundry moulds and cores

Details Cold setting sand for foundry moulds and cores Cold setting sand for foundry moulds and cores

1982-01-18

1984-02-07

Poer, James

Compositions: ceramic

Ceramic compositions

Refractory

501110, 501123, 501133, C04B 3504

Patent

active

044304412

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to foundry practice and more in particular to a cold setting sand for foundry moulds and cores.
There is known a foundry sand which comprises a refractory filler containing magnesium and/or chromium oxides, such as chrome-magnesite or magnesite-chrome, and a binder such as alcohol-sulfite lye or water glass (A. M. Liass, "Fast Setting Foundry Sands", Mashinostroenie Publishers, Moscow, 1965).
There is also known a cold setting sand which comprises a filler, orthophosphoric acid and a powdered material containing iron oxides.
The prior art sands are disadvantageous in that they are difficult to shake out, have insufficient strength, and require heat drying. Furthermore, the powder material containing iron oxides requires pregrinding, which makes the production more complicated and expensive, and damages to cores during their removal from core-boxes and subsequent handling.


DISCLOSURE OF THE INVENTION

What is required to a cold setting sand for moulds and cores of such composition having high strength, and not requiring heat drying and pregrinding of the starting materials.
The invention provides a cold setting sand for foundry moulds and cores, comprising a refractory filler and an acid, wherein the acid used is an organic acid with a dissociation constant of 10.sup.-5 to 10.sup.1, the components being contained therein in the following amounts, percent by weight:


______________________________________ refractory filler from 95 to 99 organic acid from 1 to 5 ______________________________________
A decrease in the amount of organic acid below 1.0 percent by weight will make it impossible to prepare a sand of the required strength, whereas an increase of this amount above 5.0 percent by weight will have no substantial effect on the sand properties.
The foundry sand of the invention lends itself readily for the knocking-out operation, has high strength and rapid setting rates, and requires no heat drying.
The refractory filler used in the sand of the invention is preferably magnesium oxides, and/or chromium oxides, and/or iron oxides, and/or silicon oxides, and the organic acid with the dissociation constant of 10.sup.-5 to 10.sup.1 is preferably an aromatic sulfonic acid or carboxylic acid.
Such selection of fillers and acids makes it possible to produce a cold setting sand of good technological properties.
Preferably, the cold setting sand of the invention additionally comprises orthophosphoric acid taken in a ratio to organic acid as 0.1:1 to 4:1.
The above organic acid/orthophosphoric and ratio of 1:0.1 to 1:4 permits the sand setting rates to be regulated in accordance with various production conditions. A lower content of orthophosphoric acid will have no effect on the technological properties of the sand, whereas a higher content will bring down the sand setting rate to an inadmissibly low level.


BEST MODE FOR CARRYING OUT THE INVENTION

According to the invention, the cold setting sand is prepared by stirring a mixture of the refractory filler and acid for 1-2 min.
The acid is preferably introduced undiluted, or in solution. In the latter case, the total amount of solution should be increased so that the content of acid as calculated for the undiluted acid will be within the range of 1 to 5.0 percent by weight.
The sand of the invention may be prepared both with the use as the filler of pure oxides of magnesium, and/or chrome, and/or iron, and/or silicon, or materials containing these oxides, for example, magnesite, chrome-magnesite, magnesite-chrome or a mixture thereof. The above-mentioned oxides or materials containing them can be also used in combination with other refractory fillers, such as quartz sand, zircon, kyanite-sillimanite, etc.
The aggregate content of the above-mentioned oxides in the refractory filler should be in the range of from 2.0 to 100 percent by weight.
Table 1 gives, as an example, the chemical composition of chrome-magnesite, magnesite-chrome and chrome ironstone, which are used as the refractory fill

REFERENCES:
patent: 2614050 (1952-10-01), Rusoff
patent: 3030216 (1962-04-01), Chantler et al.
patent: 3879208 (1975-04-01), Cassens
patent: 4183759 (1980-01-01), Epstein
patent: 4312671 (1982-01-01), Williame

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