Foundry Melt Charge Rule of Mixtures Calculator

This tool calculates the final alloy composition by applying the standard rule of mass-weighted mixtures (Sum(Wi * Ci) / Sum(Wi)) for scrap blending.

Charge 1 mass (kg)

Charge 1 element concentration (wt%, 0–100)

Charge 2 mass (kg)

Charge 2 element concentration (wt%, 0–100)

Charge 3 mass (kg)

Charge 3 element concentration (wt%, 0–100)

Blended alloy percentage (wt%)

0.00

Total charge mass (kg)

0.00

Disclaimer: for preliminary estimation only, not a substitute for review by a qualified/licensed engineer.

Introduction

For metallurgists and foundry charge-mix engineers blending scrap, returns and virgin ingot who must prove a proposed three-part charge lands on the alloy spec (18 wt% Cr in a 304-type heat, say) before the material goes into the furnace.

This calculator helps you quickly determine the final alloy composition using the rule of mass-weighted mixtures, ensuring your blend meets specification. It calculates the final alloy composition by applying the standard rule of mass-weighted mixtures (Sum(Wi * Ci) / Sum(Wi)) for scrap blending.

How to Use

Enter the mass in kg of your first charge component in the "Charge 1 mass (kg)" field.
Enter that component's concentration of the alloying element in wt% (0 if it carries none).
Repeat in the Charge 2 and Charge 3 rows, leaving a row's mass at 0 if your charge has only two components.
Read the blended wt% and total charge mass in the result, then check the substituted formula below to confirm the arithmetic.

FAQ

Q: How do you calculate the blended alloy percentage of a three-part melt charge?

A: Multiply each charge mass by that charge's element wt%, add the three products, and divide by the total mass: (800 kg × 18.0) + (150 kg × 9.0) + (50 kg × 0) = 15 750, ÷ 1000 kg = 15.75 wt%.

Q: Does it matter whether I enter the charge masses in kilograms or pounds?

A: No — every term in Sum(Wi × Ci) / Sum(Wi) is a mass multiplied or divided by mass, so the units cancel; just use the same unit for all three rows.

Q: Why not simply average the three percentages?

A: A plain average would weight a 1 000 kg charge and a 10 kg ladle addition equally; the rule of mixtures weights each by its mass, so the small addition moves the blend by only its share of the total.

Q: What happens if all three charge masses are zero?

A: The denominator Sum(Wi) is zero, so the calculation would divide by zero; the tool flags the error and shows no blended percentage instead.