The concept of filling ability

Influencing factors

Three zones and three solidification methods

Three kinds of contraction

The difference and prevention between shrinkage cavities and shrinkage porosity

Thermal Stress

mechanical stress

Cracks and prevention

Deformation and prevention: (Spontaneous) When pulled out, it will be compressed and concave inward. The areas under pressure stretch and bulge outward. Prevent: Thick wall uniformity, symmetrical structure, simultaneous solidification principle, anti-deformation process, aging treatment

The number of straight parting surfaces is small, and the maximum cross-section is

Less loose pieces and cores

Most of the castings are in the lower box (accurate)

Machining allowance, large holes and unmachined holes are cast

Draft angle (note the tilt direction)

Questions on page 80 and questions 5 and 6 on page 81 of the book

Avoid undercutting in the direction of mold removal

The parting surface is a plane (remove the outer fillet)

The convex and concave platforms are extended, and the angle of the ribs is convenient for mold removal.

Structural slope

Use less cores and change the core supports into process holes (fixing and cleaning)

wall thickness

wall connection

Odd number of spokes, curved spokes (minimum deformation to relieve internal stress)

Symmetrical cross-section (thermal stresses cancel each other out)

Flat plates are provided with stiffeners (to increase stiffness)

Cold deformation and hot deformation

metallic nature

Temperature (the initial forging temperature of carbon steel is below the solidus line (1500) 200 degrees Celsius, and the final forging temperature is 800 degrees Celsius)

Strain rate (cold deformation strengthening and thermal effects)

The greater the number of compressive stresses, the better the forgeability

Free forging (upsetting, drawing, punching)

Die forging (mass production)

Remainder block (used less), machining allowance, parting surface (symmetrical), skin included

Die forgings must have forging slopes and rounded corners to avoid thin-walled deep holes.

Free forging cannot have cones and bevel structures, and the intersecting lines should be changed to straight lines.

Complex components are forged separately

separation

deformation

Prevent the elimination of welding stress: select materials with good plasticity, correct welding sequence (T-shaped welding seal, weld small first and then large, cross welding), preheat before welding, weld with medium or small capacity or hammer the weld, and remove stress after welding annealing.

Prevent and eliminate deformation: stress measures, anti-deformation measures before welding, mechanical correction or flame heating correction after welding, low current, multi-layer welding