What are the advantages of the lost foam equipment? Why do defects occur during production?

Castings produced by lost foam equipment exhibit precise dimensions and shapes with excellent repeatability, embodying the characteristics of precision casting;

What are the advantages of lost foam equipment? Why do production defects occur?

The advantages of lost foam equipment are manifested in the following aspects:

(1) Castings produced by lost foam equipment exhibit precise dimensions and shapes with excellent repeatability, embodying the characteristics of precision casting;

(2) Castings feature high surface finish;

(3) Eliminating sand cores and the core-making department eradicates casting defects and scrap caused by core production and insertion;

(4) Eliminates molding boxes and mold removal, significantly simplifying the molding process and preventing defects and scrap caused by mold removal and box closure;

(5) Uses dry sand molding without binders, moisture, or additives, eliminating defects and scrap caused by moisture, additives, and binders;

(6) Greatly simplifies the sand processing system, allowing complete reuse of molding sand and eliminating the need for sand preparation and waste sand disposal departments;

(7) Easy sand removal substantially reduces labor intensity and workload;

(8) Castings from lost foam equipment exhibit no flash or burrs, cutting cleaning and polishing work by over 50%;

(9) Rational gate and riser designs can be positioned optimally without constraints from traditional parting lines or mold removal, minimizing internal casting defects;

(9) Negative pressure casting enhances liquid metal filling and shrinkage compensation, improving microstructural density of castings;

(10) Combined pouring enables multiple castings per mold cavity, substantially increasing process yield and production efficiency;

(11) Reduced machining allowances lower processing costs;

(12) Facilitates mechanized and automated assembly line production with high flexibility, enabling manufacturing of castings with different alloys, shapes, and dimensions on a single production line;

(13) Metal molds achieve service lives exceeding 100,000 cycles, reducing mold maintenance costs;

(14) Minimizes dust, fume, and noise pollution, substantially improving foundry workers' environment and reducing labor intensity. Industries traditionally dominated by male laborers can transition to female-dominated sectors;

(15) Simplifies process operations, substantially lowering the required technical proficiency of workers.

Causes of defects in lost foam casting equipment production include:

Shrinkage Cracks

Cracks in castings primarily result from contraction stresses occurring when metal solidifies beyond its ultimate strength. This relates to the casting's design and casting process, as well as cracking tendencies caused by high impurity levels in the metal (e.g., hot brittleness at high sulfur content, cold brittleness at low sulfur content). Axial intergranular cracks may also form in ingots. If not eliminated during subsequent blank forging, these cracks remain in the forging as internal fractures.

Cold rolling

This refers to a layered structure within castings, primarily related to casting process design. During liquid metal pouring, it forms as a diaphragm-like zone due to splashing, wave turning, pouring interruptions, or the convergence of two (or more) metal streams from different directions.

Ingot Body

This occurs during steel casting when molten steel is poured from a ladle into a ingot mold. Due to pouring interruptions or pauses, the initial layer of molten metal rapidly forms an oxide film in air, creating a distinct stratum (regional type). Subsequent molten metal breaks through during continuous pouring, forming the ingot body. This layer cannot be forged out during subsequent ingot blank forging.

Anisotropy

Alternatively, during ingot solidification, differing solidification rates from the periphery toward the core result in distinct crystalline structures. This manifests as mechanical anisotropy and also causes acoustic anisotropy—i.e., varying sound velocities and attenuation rates from the center outward. The presence of this anisotropy affects the magnitude and location of cracks in castings.

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