How to use this calculator
- Enter casting geometry. Enter the casting section volume and effective cooling area for the section you want to screen.
- Enter riser geometry. Enter the trial riser volume and effective cooling area using the same area convention.
- Set the empirical constants. Enter mold constant B and exponent n for the alloy, mold and process basis. B is evaluated with modulus in cm.
- Check the ratio. Compare casting time, riser time, riser time ratio and required riser modulus for the target ratio.
How it works
Chvorinov screening starts with casting modulus, the volume divided by
the effective cooling area:
M = V / A
The solidification time is then estimated with the empirical relation:
t = B * M^n
In this worksheet, dimensions can be entered in metric or imperial, but
the modulus is converted to centimeters before applying the entered
mold constant B.
The riser comparison uses the same B and n for
the casting section and the trial riser:
time ratio = t_r / t_c
To meet a target time ratio R_t, the required riser modulus is:
M_req = M_c * R_t^(1/n)
The margin output is M_r - M_req.
Worked example
Verified against the live calculator
Suppose a casting section has 500 cm3 volume and
400 cm2 cooling area. Its modulus is
M_c = 500 / 400 = 1.25 cm. With B = 120 and
n = 2, the casting time is
t_c = 120 * 1.25^2 = 187.5 s.
A trial riser with 250 cm3 volume and
130 cm2 cooling area has
M_r = 1.923 cm, so
t_r = 120 * 1.923^2 = 443.8 s. The time ratio is about
2.37. For a target ratio of 1.25, the required riser
modulus is 1.25 * sqrt(1.25) = 1.398 cm, so this trial
riser clears the formula-only modulus screen.
Frequently asked questions
What is Chvorinov's rule?
Chvorinov's rule estimates casting solidification time as t = B*M^n, where M is casting modulus V/A, B is an empirical mold constant and n is commonly near 2. It is a first-pass foundry screen, not a substitute for alloy, mold, feeding and simulation checks.
What is casting modulus?
Casting modulus is volume divided by effective cooling surface area, M = V/A. A higher modulus means a section cools and solidifies more slowly. This calculator reports casting and riser modulus in length units, while the Chvorinov time uses the modulus converted to centimeters.
How should I use the riser time ratio?
A feeder or riser should generally solidify after the casting section it feeds. The ratio t_r/t_c compares riser time with casting time, and the required riser modulus output shows the modulus needed to meet your entered target ratio under the same B and n assumptions.
Can this replace foundry simulation or shop trials?
No. This is a transparent formula worksheet for early screening. Feeding distance, shrinkage, gates, chills, riser necks, alloy freezing range, mold practice, superheat, section interaction, simulation and production trials still control final casting design.
Method & assumptions
- Uses only Chvorinov's rule,
t = B * M^n, withM = V/A. - The entered mold constant is empirical and depends on alloy, mold material, superheat, pouring practice and process control.
- Cooling area must be the effective heat-transfer area for the section or riser being screened.
- Riser comparison assumes the same
Bandnapply to both the casting section and riser. - No feeding distance, shrinkage allowance, gating, chills, riser neck geometry, hot-tear risk, solidification range, mold detail or simulation result is modeled.