DE1002495B - Process for the production of a self-drying molded part from an exothermic reacting mixture containing aluminum, oxidising agent and a fluoride by increasing it with water - Google Patents

Description

GERMAN

Exothermic mixtures as described in British Patent 627,678 are usually suitable molded parts, such. B. cans, pressed and dried in an oven.

It has been found that drying is saved and a self-drying molding is created if the mixture consisting of aluminum, oxidizing agent and a fluoride can be low Amounts of alkali are added.

The following exothermic reaction occurs when the alkaline mixture is moistened:

8 AH 5 OH "+ 2 H ₂ O + 3 NO ₃ " = 8 AlO ₂ "+ 3 NH ₃ .

If the control is correct, enough heat is developed to dry the mixture without to impair their later effect.

The alkali can be incorporated into the mixture as sodium aluminate or into the water with which the mixture is mixed is mixed into a malleable mass, are added.

The required amount of sodium aluminate is usually between 0.5 and 1.5% of the weight of the exothermic material. As from the The table below shows the delay before the self-drying reaction begins the amount of sodium aluminate is determined. You be-procedure for the production of a self-drying molded part from an exothermic reacting, aluminum, oxidizing agent and a fluoride-containing mixture by increasing with water

Applicant:

Foundry Services Limited, Birmingham (Great Britain)

Representative: Dr.-Ing. G. Eichenberg, patent attorney, Düsseldorf, Cecilienallee 76

Claimed Priority: Great Britain October 22, 1954

David Valentine Atterton and Francis Walter Pursall,

Birmingham (Great Britain) have been named as inventors

in the mixture according to British patent specification 627 678:

Sodium aluminate, in% 0.5 0.6 0.7 0.75 0.9 1.0 Time (minutes to start
the self-drying action) .. No reaction 125 45 24.5 17th 9 minutes

Advantageously, the amount of water used to form the can is compared to oven-dried mixtures increases as it improves the strength of the mold.

A more precise setting of the delay before the start of the self-drying reaction can be made by adding small amounts of boric acid in connection with the addition of sodium aluminate. The addition of 0.1% boric acid to a mixture containing 0.75% sodium aluminate gave a score of 14 50 minutes increased delay. Such delays are often of greatest value when dealing with large volumes the mixture are used in the manufacture of heavy castings.

The required alkalinity of the mixture can also be achieved by adding small amounts of base Metals, from magnesium powder or copper salts. So resulted in magnesium powder in abundance Delays similar to sodium aluminate up to 5%.

In the above-mentioned mixture of fine magnesium powder settled after the addition of 1 ⁰ Ia a self-drying reaction in 90 minutes. The addition of 0.075% copper sulfate reduced the time to 33 minutes, the addition of 0.15% copper sulfate to 10 minutes.

A u u u η gs b e i s ρ i el

An exothermic mixture was produced with the following composition:

Aluminum as a mixture of a fine aluminum ^percentage powder with aluminum sawdust 50

Sodium nitrate 7

Brownstone or iron oxide or one

Mix of both 10

Cryolite 3

Grained chamotte 23

Natural clay (bentonite) 2

Core binder 5

This mixture was shaped into a hollow cylinder with the addition of water. The water was Sodium aluminate has been added in an amount of 1 percent by weight of the molded article.

.--; ■ ".; ■ i? 609'770 / 29

Claims (1)

3 4 Self-drying started within 9 to 10 minutes from an exothermic reacting aluminum. The dried hollow cylinder contains suitable oxidizing agents and a fluoride for use in risers, pourings or mixing by pasting with water, and other useful places in casting molds. characterized in that the mixture is made weakly alkaline. Claims: 2 Method according to Claim 1, characterized in that 1. Method of making a self-dry draws that the water a small amount Sodium aluminumate is added to the hollow cylinder or other shaped part. 609 770Ä29 2.57