The article provides a brief explanation of furan casting, which is one of the most popular casting methods.
Nowadays, foundries apply various metal casting technologies such as sand casting, traditional casting, furan casting etc. Each of these listed methods maintains its own distinctive characteristics and is suitable for casting... several types of products.
What is furan casting?
Furan casting technology is the technology line favored by Japanese companies. With this technology, the sand will be mixed with Furan and Acid resin according to a certain formula, the mold will harden and create a high-gloss surface product.
Furan technology uses CNC machining machines, pulse machines, wire cutting machines. The mold is made on a synchronous line (sand discharge – mold vibration – flattening – curing – dismantling).
Furan casting typical products
Furan resin ingredients
In Furan technology, Furan resin plays the most important role. Furan resin (Furan resin) is a polymer compound with the ingredients: 75% Furfurylalcohol + 11% Formaldehyde + 9% Urea + 5% Water. The ratio between the two components Formaldehyde and Urea will affect the setting time and durability of the Furan mixture.
Furfurylalcohol (FA) composition will affect the heat resistance properties of the mixture. That's why when casting steel, the FA component often has to be up to 90% and the nitrogen should not be more than 1% because a lot of nitrogen will cause air holes when casting steel.
How is furan process?
Casting patterns are made from metal samples and wood samples.
As a major difference of Furan cast iron technique, it is a combination of casting sand + Furan resin + hardener (curing by H2SO4 acid catalyst).
The furan resin is solidified by the fermentation of a plant fiber by a catalyst in the production of acids from furfuryl alcohol.
During the mold making process, attention must be paid to the ratio of water and nitrogen in the best plastic water at <3%. Nitrogen ratio <2.5% for cast iron, steel casting <0.8%.
More water will reduce the durability of the mold mixture, increase the amount of plastic used and generate gas in the molding process.
High nitrogen causes the casting to appear porous defects on the surface. To limit nitrogen gas generation, it is imperative to use a suitable mold primer to prevent gas from entering the casting. This will increase production costs, increase the cost of castings.
Mold is made from sand + Furan resin and binder, after adding the mixture of sand + mold bone + air hole into the compact mold.
After 30-60 minutes, the sand will harden automatically, take it out of the mold and check again, when it meets the standards, paint and dry it.
Preparation: Casting sand, casting samples, cast iron, aluminum frame, mold paint, tools for creating air-hole pouring system, mold tightening bolts, mold glue, etc.
Forming: the mold will be placed into the aluminum mold ⇒ for the sand mixture that has been mixed into the aluminum mold and compacted tightly ⇒ creating a pouring system, an air outlet ⇒ after taking the sample out of the mold, proceed to assembling and then is to paint the mold to avoid burning the sand (find out the paint of the mold)⇒Fire the mold inside after painting⇒Give the glue around the mold and install the two sides of the mold together to fix it with a mold tightening bolt.
Cook cast iron, pour cast iron
With Furan iron casting technique, induction furnace will be used to smelt cast iron depending on the operation form, different furnaces will be used:
- Low frequency induction furnaces use frequencies from 50 ⁓ 60Hz.
- Medium frequency induction furnace uses frequency 120 ⁓ 200 Hz.
- High frequency induction furnaces use frequencies from 500 ⁓ 3000 Hz.
The execution stages of the Furan technology cast iron process are very meticulous and costly, so the casting process is done very carefully, the casting process will be simulated in advance on the computer to minimize the maximum. Damage to subsequent pouring during smelting of cast iron will:
- Component Analysis Modification Modification of Components.
- Test the temperature of liquid metal with a thermocouple, hardening test, and flowability test.
- Finally, adjust the cast iron composition and pour cast iron into the bucket.
The bucket used is an inclined bucket with gears: It is a round cylindrical iron barrel lined with heat-resistant brick and lime mortar. There is gear attachment and tilt movement by turning the handlebars. Carry out transporting this pouring bucket by crane.
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