Production Process of Lost Foam Casting Valve


1. Product Overview

A lost foam casting workshop in Handan mainly produces high-quality valves made of cast steel, ductile iron and other materials. Valves are pressure-bearing parts, so there are high requirements for the density and materials of valve castings. A lost foam casting workshop in Handan mainly produces high-quality valves made of cast steel, ductile iron and other materials. Valves are pressure-bearing parts, so there are high requirements for the density and materials of valve castings.

2. material requirements

WCB Chemical Composition Requirements for Carbon Steel Valves

3. white mold production and raw material selection

For the quality of the white mold, the STMMA-FD model is selected for the pre-production material. The raw material has less combustion residue, small particle size and easy filling. The density of the pre-production beads is controlled at 22g/L, so that the white mold has sufficient strength and lighter density at the same time, thus preventing carbon deposition defects in the casting.

Design of 4. gating system

Considering that the structure of the valve itself adopts cross-casting method, the sprue: 50*50, the cross-runner is cylindrical in diameter of 50mm, the inner gate is wedge-shaped and has multiple water inlets. The riser is selected as an open riser with a height of 200mm. The riser with a wall thickness much larger than the hot section of the casting can prevent the casting from shrinking and improve the density of the casting. The valve parts also need to pass the pressure experiment. Such a design can effectively improve the finished product rate of the casting.

5. paint brushing and drying

The coating is made of special coating for ruiou cast steel, which has high fire resistance and good air permeability. After casting, it is easy to peel off from the surface of the casting and is convenient to clean.

Paint mixing should first add the proportion of good water, and then add the paint bag by bag to stir. After the completion of the stirring, the use of bomei agent to measure the degree of beauty of the coating, generally controlled between 68-70. Stirring time should be controlled in more than 2 hours, enough stirring time to make the coating uniform without dry particles.

The combination of dipping and brushing shall be selected for coating, and the coating shall be applied in 2-3 times. For the first time, the paint density should be slightly thinner. Dip the whole white mold, check whether there is any white, then put the painted white mold on the drain rack to drain, and then transfer it to the drying rack and send it to the drying room. First, the drying time after the second coating is more than 8 hours, and the last coating drying should be more than 24 hours. As the casting system is washed by a large amount of molten iron, the coating can be brushed once more to prevent the molten iron from washing the coating and entangling the molding sand into the casting.

After the yellow mold is completely dried, it shall be transferred to the casting area, and the damaged and exposed part of the yellow mold shall be repaired with alcohol paint or mastic.

The final coating thickness is controlled at about 1.5-2mm.

 

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