Chapter II Classification and Selection Principles of White Area 2.1 Model Materials


Classification and Selection Principles of 2.1 Model Materials

When it comes to lost foam models, it is necessary to understand the special requirements for lost foam casting models. The relevant requirements are as follows:

1. Gasification quickly, completely, less residue

2. The prepared pattern has low density, good strength and surface rigidity. In order to make the pattern in the manufacturing, handling and dry sand filling process is not easy to damage, to ensure that the shape size and properties of stability.

3. The variety and specifications are complete, which can adapt to the needs of different materials and structural castings.

Then, what are the model materials? What are the different specifications and physical and chemical properties of these materials? How can we select the model materials according to the characteristics of the model?

2.1.1 Overview

Revisit the definition of lost foam casting. Lost foam casting (also known as solid casting) is the use of foam plastic (EPS, STMMA or EPMMA) polymer materials are made into the structure and size of the parts to be cast.MatchThe solid mold is dipped with refractory coating (which plays the role of strengthening, smooth and air permeability) and dried, buried in dry quartz sand and subjected to three-dimensional vibration modeling. The casting molding sand box is poured into molten metal under negative pressure to make the polymer material model heated, gasified and extracted, and then replaced by liquid metal.

2.1.2 Classification of model materials:

There are three kinds of foam beads for lost foam casting

  expandable polystyreneBeads (abbreviatedEPS)At present, the brands existing in the market include Dragon Ace, Jiaxing Brand, Xingda, etc., but the performance of Dragon Ace will be relatively stable. (The following model takes Dragon Ace as an example to explain)

  ② expandable methyl methacrylate and styrene copolymer resin beads (referred to as STMMA); now there is Hangzhou Kester to fill the domestic technology gap.

  ③ Developmentmethyl methacrylate beads(EPMMA for short).

2.1.3 Model, characteristics and scope of application of model materials

1EPS Model Classification

① Grade E material-standard material.

② Grade H material-special light material, high foaming ratio.

Grade B material-fast plastic, energy-saving type.

④ Class F material-flame retardant type.

⑤ FR grade material-pigment

⑥ Grade N material-impact resistant material

⑦ FD grade material-food grade material

⑧ Grade G material-special material

According to the use requirements of the lost foam for EPS, we will only explain in detail for Class H materials, that is, super light materials.

(1)H material characteristics

    (1) Multiple foaming performance-- highest available6Second, the bubbles are full and elastic.

foaming performance-- The foam is dry and loose, with good fluidity, high foaming ratio, short curing time and steam saving.

Machining performance-- Good combination, short heating time, wide molding range.

molding quality-- smooth, bright, good strength, good adhesion,

Preservation-- Raw grain storage6No problem for months, stable quality.

 

Specifications

specification

Particle size range (mm)

particle size range

One-time firing rate (times)

one-time foaming rate

Many times foaming rate

H-MS

1.2-1.8

75-85

180-200

H-SA

0.9-1.4

65-75

160-190

H-SB

0.7-1.1

55-65

120-150

H-S

0.5-0.9

40-55

80-120

H-4S

0.3-0.6

25-40

 

(2)EPSOriginal materialSpecifications:

 

The above five groups of photos are Dragon AceH-SM/ H-SA/ H-/ H-S/ H-4S 

 

(3)EPSScope of application of raw materials:Used for casting non-ferrous metals, gray iron and generalSteel castings.

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