I. Seven Core Advantages of V-Process Casting

1. Convenient Molding, Low Mold Cost and Long Service Life

• During the molding process, the sand mold is solidified under the action of vacuum, resulting in low demolding resistance and easy demolding;

• The mold does not need to bear the friction and impact of traditional molding, so wear is minimal, and the service life of the metal mold is greatly prolonged;

• The requirements for mold material are flexible, and even wooden materials can be used, which reduces the mold manufacturing cost and cycle.

2. High Casting Precision, Excellent Surface Quality and Mature Typical Products

• The casting has high dimensional accuracy and clear contours, among which the surface roughness of cast iron parts can reach Ra18-25μm;

• The application cases are extensive: the cast iron counterweight of forklift is its typical representative (for example, the counterweight produced by Hefei Casting and Forging Factory of Anhui Heli Forklift Group once won the first prize of castings in the 4th Beijing International Foundry Industry Exhibition in 2002). Moreover, almost all the counterweights and balance weights required for forklifts and engineering vehicles around the world are produced by V-process casting.

3. Strong Fluidity of Molten Metal, Suitable for Producing Both Thick-Walled and Thin-Walled Castings

• Dual effects improve fluidity: the heat preservation effect of V-process dry sand can slow down the cooling of molten metal, and the vacuum suction effect can eliminate the gas resistance in the mold cavity. Tests have proved that compared with green sand casting, the fluidity of molten metal in V-process casting can be increased by 27%;

• It has a wide range of applications: it can not only produce thick-walled castings, but also stably produce thin-walled castings. For example, Nanjing Toto Co., Ltd. introduced a production line from Japan to produce high-end cast iron bathtubs with a size of 1829mm×1067mm×650mm, a weight of 180kg and a wall thickness of only 7mm; the cast iron piano frame produced by Tianjin Young Chang Piano Casting Co., Ltd. is also a benchmark product of thin-walled parts made by V-process casting.

4. Good Sand Mold Stability and Significant Improvement in Molten Metal Utilization Rate

• The sand mold has excellent performance: compared with the traditional green sand mold, the V-process sand mold has no problem of mold wall movement, the hardness of the sand mold can reach 90-95, and the heat preservation time of dry sand is long, so the volume of the riser (the structure used for feeding molten metal) can be reduced by 5%-15%;

• Less material waste: the utilization rate of molten metal is greatly improved, among which the utilization rate of ductile iron castings is increased by about 25%, and that of steel castings is increased by about 20%. It is suitable for the production of ductile iron castings (such as ductile iron rear axles made by V-process casting) and steel castings (such as railway locomotive steel side frames produced by Tianrui Group using V-process casting).

5. Suitable for Aluminum Alloy Castings, Compatible with Large-Sized and High-Precision Small-Sized Parts

• The process characteristics are in line with the needs of aluminum castings: the V-process sand mold is in a vacuum environment, contains no moisture and has good heat preservation performance, which is especially suitable for producing small-batch aluminum alloy castings with few or no inner cavities;

• Diverse application scenarios: Japan once used a large-scale V-process molding machine and an extra-large sand box (7000mm×4000mm×1000/800mm) to produce cast aluminum yacht hulls; enterprises in Ukraine, the Netherlands, the United States and other countries use it to produce small aluminum castings for the medical, electronic and communication industries, and the surface quality is comparable to that of metal mold cast aluminum parts (such as the products of Harmony Casting Company in the United States, with a large flat surface thickness of 4.7mm and a local thickness as thin as 2.3mm).

6. Low Investment and Energy Consumption Costs, High Production Economy

• Low initial investment: compared with other advanced casting processes, the equipment investment of V-process casting is lower;

• Controllable operation cost: the sand treatment system has a simple structure, no need for complex links such as sand mixing and drying, and less energy consumption during operation.

7. Environmentally Friendly and in Line with Energy Conservation and Emission Reduction Requirements

• The production site is clean: low noise, the amount of casting shot blasting cleaning is reduced by more than 50%, and the required labor force is reduced by more than 35%;

• Less pollution discharge: the flue gas from films, coatings and resin sand cores generated during pouring can be pumped away by the vacuum system and discharged up to the standard after dry-wet filtration;

• Resource recycling: the dry sand regeneration rate is as high as 95%, and the discharge of solid waste is small, which is in line with the energy conservation and emission reduction needs of modern industry.

II. Five Prominent Disadvantages of V-Process Casting

1. Not Suitable for Producing Castings with Complex Shapes
   Molding depends on the coverage and extension of plastic films, but the extensibility of films is limited, so they cannot fit the surfaces of complex mold cavities (such as multi-curved surfaces, deep cavities and complex boss structures), which is prone to problems such as film rupture and incomplete molding.
2. Immature Core-Making Technology, Limitations in Producing Castings with Complex Inner Cavities
   The core-making process of V-process itself has not made a breakthrough. If it is necessary to produce castings with inner cavities, it is necessary to rely on external core-making processes such as resin sand cores or sodium silicate sand cores, which not only increases the production process and cost, but also may affect the casting quality due to the matching problem between the sand core and the sand mold.
3. Vacuum System Needs to Be Continuously Connected to the Sand Mold, Resulting in Low Production Flexibility
   The stability of the sand mold depends on the maintenance of a vacuum environment. During the whole process from molding, closing to pouring and cooling, the vacuum system needs to be connected to the sand mold at any time, and cannot be flexibly transferred like the traditional sand mold, which limits the layout of the production line and the mass production efficiency.
4. Not Suitable for Small-Sized Castings, Difficult to Improve Production Efficiency
   The "output per unit time ratio" of the process flow (such as film coverage, vacuum pumping and sand mold solidification) for small-sized castings is low, and the production of small-sized castings cannot give full play to the advantages of V-process in precision and material utilization rate, resulting in production efficiency far lower than that of traditional green sand casting.
5. Steel Castings Are Prone to Defects, and the Carburization Problem of Low-Carbon Steel Is Prominent
   When producing steel castings, the vacuum environment may intensify the reaction between molten metal and sand mold and coating, which is prone to defects such as pores and slag inclusions; especially for low-carbon steel parts, the carbon elements in the sand mold (such as organic components in resin sand cores and coatings) are easy to penetrate into the castings, leading to casting carburization and affecting the mechanical properties.