Green Sand Casting

Key Parameters of Green Sand Casting

1. Sand Mixture Ratio

- Clay content: Typically 8-12% (by mass), with clay serving as the binder.

- Sand particles: Mainly silica sand (80-90% by mass), with particle size controlled (50-100 mesh) to improve fluidity.

- Moisture: 4-6% (affects mold strength and permeability).

2. Green Compression Strength

- Mold compression strength: 0.1-0.3 MPa, ensuring the mold does not deform during handling and pouring.

3. Permeability

- Standard value: 80-150 (permeability units), ensuring gases are smoothly discharged during pouring.

4. Compactness Rate

- 35-45%, reflecting the degree of mold compaction, which affects strength and surface quality.

5. Mold Hardness

- Green sand hardness: 70-90 (Shore hardness scale), requiring uniform compaction.

1. Cost-effective

Low material cost: Natural sand and clay are abundant and inexpensive, reducing procurement expenses.

Minimal equipment investment: Simple equipment leads to low initial investment and maintenance costs.

Low energy consumption: No need for high-temperature baking, thus saving energy.

2. Good process performance

High molding efficiency: The sand's fluidity enables rapid filling and short molding cycles.

Relatively high accuracy: can achieve good dimensional accuracy and surface quality.

Good permeability: Allows gas to escape during pouring, reducing defects.

3. Easy operation

Simple to master: The straightforward process is easy for operators to learn.

Flexible production: Can choose manual or machine molding for different production scales.

4. Environmental-friendly

Recyclable: Used sand can be recycled, minimizing waste.

Low pollution: Emits fewer harmful substances, being environmentally friendly.

The post-processing flow for green sand casting and a corresponding text-based flowchart description:

I. Post-Processing Flow for Green Sand Casting

1. Sand Knockout

- Purpose: Separate the casting from the sand mold and remove most of the adhering sand.

- Methods:

- Mechanical knockout: Using vibratory shakeout machines or tumbling equipment.

- Manual knockout: Suitable for small or complex castings.

2. Gating and Riser Removal

-Purpose: Remove the gating system (gates, risers, overflow channels, etc.) from the casting.

- Methods:

- Gas cutting, grinding wheel cutting, hammering, or hydraulic shearing.

3. Surface Cleaning

- Purpose: Remove residual sand, oxide scale, and burrs.

- Steps:

- Mechanical cleaning: Shot blasting, sand blasting, or grinding.

- Chemical cleaning: Acid pickling (to remove oxide scale) or alkaline cleaning (to neutralize residual clay).

4. Heat Treatment (Optional)

- Purpose: Improve the mechanical properties of the casting (e.g., annealing, normalizing, quenching).

- Applications: Castings requiring high precision or strength (e.g., gears, engine components).

5. Quality Inspection

- Inspection Items:

- Visual inspection: Surface cracks, pores, sand inclusions, and other defects.

- Dimensional measurement: Using calipers, coordinate measuring machines (CMM), etc.

- Non-destructive testing: X-ray, ultrasonic testing (UT), or magnetic particle testing (MT).

6. Defect Repair

- Methods:

- Welding repair (for cracks or pores).

- Epoxy resin filling (for small defects in non-load-bearing areas).

7. Anti-Corrosion Treatment

- Methods:

- Spraying anti-rust oil or paint.

- Phosphating treatment (to enhance surface corrosion resistance).

8. Packaging & Storage

- Notes: Moisture-proof, impact-resistant packaging with clear labeling.

II. Key Considerations**

1. Sand Reclamation:

- Used sand from knockout must be screened, magnetically separated (to remove metal scraps), and dedusted before reuse to reduce material costs.

2. Environmental Measures:

- Wastewater from chemical cleaning must be neutralized, and dust collection systems must be installed for shot/sand blasting equipment.

3. Automation Equipment:

- Automated shot blasting machines or robotic cutting systems are recommended to improve efficiency and consistency.