title = "Solidification, Cooling Rates, and Microstructure"

content = """
The solidification process — the transition of molten metal to a solid crystalline structure — largely
determines the microstructure and therefore the mechanical properties of a casting. Controlling
solidification is one of the most technically important aspects of foundry operations at Ridgecrest
Metalworks.

Solidification Sequence:
When molten metal is poured into a mold, heat extraction begins immediately through the mold walls.
Solidification initiates at the mold-metal interface (chill zone) and progresses inward. In a properly
designed casting, solidification should proceed directionally toward the risers, which feed liquid
metal to compensate for shrinkage as the metal contracts from liquid to solid.

Cooling Rate Effects on Microstructure:
- Fast cooling (thin sections, metal molds): Produces fine grain size, fine dendritic arm spacing,
  finer distribution of second-phase particles. Generally results in higher strength and hardness,
  better impact properties.
- Slow cooling (thick sections, sand molds): Produces coarser grain size and coarser microstructure.
  In gray iron, slower cooling promotes more graphite precipitation as flakes; in ductile iron, slower
  cooling affects nodule count and morphology.

Thermal Gradients and Centerline Porosity:
If a section solidifies simultaneously from all sides without a connected liquid feeding path,
the shrinkage that occurs during solidification cannot be compensated by incoming liquid metal and
a pore (shrinkage cavity) forms. This is the fundamental reason for riser design: risers are kept
liquid by their larger thermal mass and feed metal to the solidifying casting until the casting is
fully solid.

Solidification Simulation:
Process engineers at Ridgecrest use casting solidification simulation software to predict thermal
gradients, identify hot spots (areas of last solidification), and optimize riser placement and size
before building tooling. Simulation results are archived as part of the casting design record.

Heat Treatment After Casting:
Many castings are heat-treated after solidification to relieve internal stresses (stress relief anneal),
refine the microstructure (normalization), or achieve specified mechanical properties (quench and
temper). The as-cast microstructure is the starting condition for heat treatment, and achieving the
target as-cast structure (correct grain size, controlled segregation) is prerequisite to achieving
the target post-heat-treat properties.
"""

version = "0.0.1"
