Furan Sand Casting is a widely used process in the production of cast iron parts. Its characteristic is that the pattern is made of polystyrene foam, which has low strength and is not removed after molding. During the pouring process, the pattern vaporizes and burns, producing a large amount of gas. This technology is widely used in the production of medium and large castings due to its unique advantages.
Design Elements of Furan Resin Sand Casting Process
When designing the Furan Sand Casting process, special attention should be paid to the following elements:
Pouring Position and Parting Line
Important machining surfaces and high-demand areas should be placed on the bottom or side to reduce the adverse effects of combustion residues on critical parts. Castings are generally placed in the lower mold, and the parting line is selected according to the principle of convenient molding, usually by placing it stably on the molding flat plate.
Machining Allowance
Select according to the third-level precision gray cast iron parts machining allowance (JZ67-62), and the top surface allowance can be increased by 1~3mm. Other process allowances are the same as ordinary sand casting. Furan Sand Casting does not need to consider draft angles or parting negatives and other process allowances.
Pouring System
An open pouring system is used, with the section ratio of each element being Fvertical : Fhorizontal : Finner=1 : (22.5) : (1.4~1.6), requiring an increase in the total area of the inner gate by 20%~30% compared to ordinary sand casting. Depending on the structure of the casting, the top pour, bottom pour, and step pour methods can be used, with preference given to the bottom pour method.
Riser Design
Furan Sand Casting places more emphasis on the use of risers. Not only should edging risers be used to prevent shrinkage defects in hot spot areas, but slag-collecting risers are also suitable to prevent slag inclusions in areas far from the gate or in dead corners and top positions of the mold. A certain number of exhaust risers should be set on the top surface of the mold to accelerate the escape of gas within the mold.
Furan Resin Sand Casting Process: Molding and Pouring
Pattern Making
The foam pattern is made of casting plate materials using traditional wooden mold manufacturing techniques, fabricated through mechanical processing and bonding. The active parts are positioned with bosses or iron nails, and defects such as holes on the surface of the pattern can be repaired with wax or filled with the same material, and then glass paper is applied for repair.
Coating Application
It is advisable to use alcohol-based coatings for medium and large castings. When using two types of coatings, apply a layer of graphite powder coating first, let it dry naturally, and then apply a layer of high-temperature coating. The coating layer is generally 1.5~2.0mm thick. The performance of the coating is crucial to the quality of the casting, so choosing the appropriate type of coating is very important.
Preparation of Cold Hard Furan Resin Sand
The sand should be mixed using a continuous sand mixer. Since Furan Sand Casting does not require pattern removal, box assembly, etc., the performance requirements of the resin sand process can be appropriately lowered.
Molding Process
First, place the pattern smoothly on the molding flat plate, place the pouring system close to the pattern, and then fill the sand to shape after setting the sand box. When compacting the sand, avoid exerting excessive force to prevent damage to the pattern. The sand mold should have high compactness that is as uniform as possible, which is a basic requirement for Furan Sand Casting molds. After the lower box is solidified and turned over, clean and inspect the quality of the lower mold immediately, apply additional coating if necessary, and speed up drying.
Compared with ordinary sand casting, Furan Sand Casting has significant technical and economic benefits in many aspects. This process is especially suitable for the production of medium and large, single-piece, small batch, complex parts.
Furan Sand Casting is widely used for surface strengthening of various wear-resistant equipment parts in industries such as metallurgical machinery, building materials machinery, power machinery, and mining machinery. It is particularly suitable for wear and impact from larger particulate materials, such as in metallurgical slag systems, feed and discharge systems, waste well transport filling, dry and wet materials in mines, chemical machinery, and coal ash gas transportation. Castings produced through this process have improved quality and dimensional accuracy while reducing production costs, gaining favor in an increasing number of industries and manufacturers.