Introduction of special foam beads for lost foam casting

2024-06-22 10:06:25

If you want to ensure the quality of lost foam casting products, the use of high-quality casting special foam beads is a key link. The foam model used to make a product with packaging foam will greatly affect the quality of the casting product because of its uncertainties such as gas generation and carbon addition. Now with the rapid development of the lost foam casting industry in China, the raw and auxiliary materials have also become more and more specialized. In the following, taking the special foam beads of the disappearing die casting of the glory card as an example, some technical indexes and performances of the foam beads in the lost and auxiliary casting raw materials are introduced in detail:

1. Conventional special names for special foam beads for lost foam casting:

1. Expandable polystyrene resin beads (EPS) for lost foam casting;

2. Expandable methyl methacrylate and styrene copolymer resin beads (STMMA for short);

3. Expandable polymethyl methacrylate resin beads {abbreviated as EPMMA).

The user selects the required variety and specifications according to the characteristics and requirements of the casting to ensure a high quality foam model and lost foam casting.

Second, the scope of application of special foam bead products for lost foam casting

Variety
Scope of application
EPS
Non-ferrous metals (aluminum, copper, etc.), gray iron and general steel castings
STMMA
Gray iron, ductile iron, low carbon steel, alloy steel castings
EPMMA
Ductile iron, malleable cast iron, low carbon steel, alloy steel, stainless steel castings, etc.

Third, the product specifications

index
EPS
STMMA
EPMMA
Color
Translucent beads
Translucent milky white beads
Milky white beads
Apparent density (g/ml)
0.55-0.67
0.55-0.67
0.55-0.67
Pre-expansion ratio ≥
50
45
40
Volatile (%) ≥
6.5
8
10

Fourth, the bead size (mm)

1# 0.60-0.80
2# 0.42-0.60
3# 0.30-0.40
4# 0.25-0.30
5# 0.21-0.25
6# 0.18-0.21

Note: This product contains low-boiling hydrocarbon foaming agent. It must be stored in a closed container lined with plastic film bag during storage and transportation, and stored in a place with low temperature, ventilation and away from fire.

Fifth, the method of use:

The production process of the lost foam casting foam model is as follows:

Original beads → pre-foaming → drying, curing → molding foaming → foaming plastic mold

1. Original resin beads selection

First, according to the material of the casting and the quality requirements of the casting, which kind to choose, according to

The minimum wall thickness of the casting is chosen to be the bead size. The primary beads generally used have a particle size less than or equal to 1/9 - 1/10 of the minimum wall thickness of the casting.

2. Pre-expansion of resin beads

The pre-expansion of the beads for lost foam casting uses a batch pre-expansion machine. There are two types of intermittent pre-expanders, namely, a pressurized pre-expander and a vacuum pre-expander. Generally, the vacuum pre-expansion machine is better than the pressurized pre-expansion machine. The pre-fabrication parameters of the two pre-foaming machines can be referred to as follows:

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