During melting and mold filling of molten metal, various inclusions will be generated. If these impurities cannot be removed, casting defects will form inside the castings. Defective castings require extensive manual grinding and welding repair, and severe defects will result in scrapped parts. For high-grade cast steel production, foam ceramic filters have become an effective measure to control slag inclusion defects and stabilize casting quality, and their application is growing rapidly.

The manufacturer mainly produces cast steel parts for vacuum pumps, using chromite sand and alkaline phenolic resin sand molding process. The cast steel impellers produced by this enterprise have long suffered from slag inclusion defects. The narrow space between impeller blades makes welding repair and grinding extremely difficult, which seriously restricts casting quality and reduces overall production efficiency.

Ⅰ. Technical Parameters of Casting and Filter

Casting: Vacuum Pump Impeller

1. Material: 316 stainless steel

2. Total pouring weight: 430 kg, net casting weight: 340 kg

3. Pouring temperature: 1650℃, pouring time: 25 s

4. Filter adopted: Zirconia foam ceramic filter, specification Φ150×30, 10 ppi, quantity: 1 piece

Technical Indicators of Zirconia Foam Ceramic Filter

Ⅱ. Key Operation Notes for Filter

1. Pouring temperature control: The pouring temperature shall be kept above 1600℃ when using zirconia foam ceramic filters. The pouring temperature of this 316 stainless steel impeller is 1650℃, meeting the requirement.

2. Preheating protection: Preheat with hot dry air for more than 40 minutes before pouring to avoid chilling of the filter, preventing temperature drop of molten metal and cold shut defects.

3. Pouring operation: Adopt rapid pouring to match the flow capacity of the filter and ensure stable mold filling.

Ⅲ. Application Results

1. Slag inclusion defects of castings are basically eliminated, and the surface finish of castings is significantly improved.

2. The welding repair rate of castings is greatly reduced, solving the pain point of difficult repair in the narrow blade area of impellers.

3. The comprehensive production cost of castings is reduced by more than 10%, with synchronous improvement of product yield and production efficiency.

Zirconia foam ceramic filter features high temperature resistance and good mechanical properties, suitable for the production of 316 stainless steel and other stainless steel castings as well as high-temperature alloy castings. For complex vacuum pump impeller castings with difficult post-processing, it can efficiently filter inclusions in molten steel, stabilize casting quality and reduce repair working hours, providing a reliable purification solution for high-end stainless steel casting production.