DE102006031191A1 - Inorganic casting core sand binder, useful in aluminum foundry and as a fertilizer, comprises inorganic binder containing elements and ions of potassium ion, calcium ion and magnesium ion, and sulfate, phosphate and oxide - Google Patents

Abstract

The invention is a process for the production of core moldings for the foundry industry, based on molding sand and inorganic binders.
The binders are selected so that the molding sand residues can be used as special fertilizer.
Inorganic salts are used whose cations are the elements Ca, K and Mg and whose anions consist of sulphate, phosphate or oxides. It can thereby find salt combinations that act alone with H ₂ O and without organic compounds. The components for bonding the foundry sand can also be used as a sizing in a modified application. Furthermore, a further innovation in the production of sizing by overmolding the core molds with metal pastes is presented.

Description

following listed inorganic binders are for the production of casting cores for foundry technology known.

R. Stark used to set molding sand 3-7% -tige mixtures of sodium hexametaphosphate with about 0.5 to 2% water based on 100% molding sand content. This binder is characterized inter alia by the fact that the inorganic binder is very soluble in water and relatively low temperatures of 50 to 100 ° C for curing the cores are necessary ( DE 195 49 469 A1 ).

Especially for the casting of aluminum alloys there is an invention of R. Koppenhofer, where inorganic binders with magnesium sulfate, montmorillonite, bentonite and / or aluminum silicate layer minerals are used ( DE 10 2004 033 053 A1 ).

Several patents disclose water glass based binders. The AWB process uses 3% sodium silicate with a solids content of 30% and cures at a firing pressure of 6 bar at a core box temperature of 160 ° C in 20-30 s from the molding. It has a flexural strength of 1 N / mm ² ( DE 196 32 293 A1 ).

Th. Steinhäuser and RA Jones also use water-based inorganic binders with the alkali metal ions Li, K and Na ( DE 19951 622 A1 and DE 196 322 9306 ) and describe recycling in the form of orbital sands ( EP 0 917 499 B1 ).

Also sodium silicate used Th. Cobett. Iron oxide, a lubricant and starch preparations are added to this binder ( DE 3403 583 C2 ).

Laempe + Kules distribute a core sand binder, the Laempe Kules Binder LK 700, based on magnesium sulfate, NaOH and silicate and other inorganic Based on additives.

A. Zentgraf uses the so-called langbeinite pulp, an aqueous solution of the double salt K ₂ SO ₄ .2MgSO ₄ ( DE 333 22 50 ). The drying temperature of the core sands is 95 ≤ T ≤ 110 ° C. This pulp is also used, among other things, for the granulation of MgO-containing fertilizers.

Out the view of a secondary utilization the core sands as fertilizer In principle, the orthosilicates seem to be unsuitable. Sodium water glass due of sodium, the other water glasses because of their very high pH. The hexametaphosphate is also because of the sodium content as fertilizer component not suitable. The long-legged turbid as Binder originally comes from as a binder from the Mg artificial fertilizer production and owns good fertilizer properties with the elements K, Mg and the sulphate group but is not discussed under this aspect in the above patent.

According to the invention is in the initially formulated task, Kernsandbinder after the To recycle casts in such a way that they are used as special fertilizer can be solved by that inorganic salts are used as binders. You have to, at all to serve as adhesive components, Be hydrate former. It limits the number of conceivable salts by their second use, later Fertilizer too be, on the cations of the elements K, Mg and Ca, in the Anionenstrukturen on phosphates, sulfates and oxides.

These Structures are also characterized by this, especially for cast aluminum, to be free of orthosilicates. In principle, silicates of the second use would be her seen as fertilizer component Although it is suitable, but due to its setting behavior, relatively firm, hard to crumble structures, as well as their property, to the interface Al casting / core sanding tend to aluminosilicate formation led to their exclusion as an adhesive component.

For use, the compounds MgO, MgSO _4, K ₂ HPO _4, KPO ₃ and Ca can (PO _{3) 2,} which are mixed in various combinations together with water and sand core and cured after a preliminary drying in the microwave. This produces moldings which are still break-resistant at a layer thickness of 3 mm. The bending tensile strength of 4 × 4 × 16 cm test specimens is> 3 N / mm ² .

Of course, the idea of a core sand binder recyclable as a fertilizer component also implies that sizing should consist of similar material. Therefore, a size of MgO, CaO and MgSO ₄ with H ₂ O and methanol or glycerol was developed or implemented the idea to coat the core sand binder during aluminum casting with metallic Al-flakes. When crushing the shapes you can recover the Al metal flakes similar to the usual Plastrecyclen.

Not necessarily, the Mg salts used must be primarily produced substances, but may in turn represent recyclates. For example, in the case of heraklith production, so-called quench dust is precipitated as an MgO compound. The MgO-containing dust can be worked up with phosphorous or sulfuric acid to corresponding salts. These resulting Mg salts again represent basic components of the core sand binders.

Experimental Procedure

A MgO / MgSO ₄ binder

1.5 MgO are stirred dry with 4.5 g MgSO ₄ . This mixture is mixed with 94 g foundry sand. Are then added to above mixture, 10 ml H ₂ O and stirred for about 5 '. The pot life of the mass is about 20 '. After pre-drying the moldings, either the core sand molds can be cured with 4 × 2 'microwave irradiation (about 400 W) or at 140 ° C. in a drying oven.

BK ₂ HPO ₄ / MgSO ₄ binder

2 g of MgSO ₄ are dry-mixed with 2 g of K ₂ HPO ₄ . 94 g of foundry sand are added to this mixture. With a mixture of 3.4 g of H ₂ O and 2 g of glycerol, the core sand binder is finished. In contrast to recipe A, this binder must be allowed to air-dry for several days before it can be cured in the microwave.

C Binder made of magnesium oxide from puff dust

1.5 g of masticant dust, a product of the MgO production, is stirred with 10 ml of H ₂ O and then poured over with 3.7 g of H ₂ SO ₄ . After cooling the mixture, another 1.5 g of masticant dust is added. This mixture is mixed in accordance with regulation A with 94 g of sand and from this mixture a mold, as described above, prepared.

D Preparation of MgO based sizing

D1 Mg size without organics

1.5 g of MgO are dry-mixed with 4.5 g of MgSO ₄ . In this mixture is added 10 g of MeOH, and then 6 g H ₂ O. The sizing may be applied by dipping onto the mold after a waiting period of about 2-3 '. The solvent MeOH evaporates under the hood during pre-drying.

D2 Ca / Mg size

1.5 g of CaO are stirred with 4.5 g of MgSO ₄ dry. To this mixture are added 10 g MeOH and 6 g H ₂ O and the procedure is as for D1. The pot life of this sizing is 10 '.

D3 Mg sizing with residual organics

4 g of MgO are stirred with 12 g of MgSO ₄ and 10 g of glycerol. Then 20 ml of H ₂ O are added to this mixture. This size is suitable only for dipping. The pot life is much longer compared to D1.

E Preparation of sizing with metal suspensions

In the size according to regulation C becomes instead of ethanol a mixture of stirred metals (eg Al paste). It comes to 3 g of metal paste about 30 ml of ethanol. The sizing is sprayable and submersible.

F casting trials

From Each Kernsandbinder was prepared according to regulation A to C, a crucible and coated with the sizes D and E. It was then poured out with about 95 g of Al at a temperature of 800 ° C.

test criteria were the kindness the cooled metal surfaces, which had direct contact with the crucible, the gas formation at Casting and crucible strength during casting. As a result, it was found be that all crucible recipes the casting without cracks or Cracks were stable, the Al surfaces were smooth and only at Simple D1 a weak gas formation occurred. The molding sand material let himself go chop well.

G fertilizer discharge

The Material of trial F with a fertilizer content of approx. 6% MgO and Sulphate and 94% sand leaves to work for the soil improvement of magnesium and sulphate poorer soils, but especially in viticulture for Chlorosis susceptible Grape varieties, such as Müller-Thurgauer, Pinot Noir and Traminer.

H bending tensile strength of the core sand binders

From the core sand binders according to instructions A to C specimens were prepared with the dimensions of 4 × 4 × 16 cm size and cured. Their flexural strength was 6 Niger binder amount at 3 N / mm ² .

Claims (1)

Inorganic Kernsandbinder for aluminum casting and their use as fertilizers, characterized in that 1. the inorganic binder contains only elements and ions that can be safely used after their primary use as Kernsandbinder as a special fertilizer; So only the cations K ⁺ , Ca ⁺ , Mg ²⁺ and the anions sulfate, phosphate and oxide are used, 2. some of the combinations of the inorganics listed in claim 1 used only with water as a binder components for the core sand who which, but not necessarily, contain organic components (eg formulations A to C), 3. the inorganic compounds mentioned in claim 1 can also be used for the preparation of sizes according to formulations D1 to D3, 4. in the case of a coating of Al-plate cores that are mechanically or electromechanically removable from the sand matrix after casting