To determine the appropriate size for an induction furnace, first consider the required hourly output of molten iron, the duration of each melting cycle, the actual operational availability of the furnace, and the metal yield. Then, select a furnace with sufficient capacity—ideally one that also provides a bit of extra margin.

I. Introduction

When determining the capacity of an induction furnace for a foundry, it is not enough to simply look at the desired tonnage of metal to be melted. Factors such as daily production targets, batch weight, melting cycle, type of metal, furnace power, charging time, pouring schedules, metal yield, and equipment utilization must all be taken into account.

Choosing a furnace that is too small can create a production bottleneck, while an oversized furnace may increase equipment investment, electricity demand, and operating costs.

This guide explains how to calculate induction furnace capacity, melting rate, tons per hour, furnace power, and the number of furnaces required for a foundry.

II. What Does Induction Furnace Capacity Mean?

Induction furnace capacity normally refers to the amount of molten metal that the furnace can hold or melt in one batch.

Common induction furnace capacities include:

100 kg
250 kg
500 kg
1 ton
2 tons
3 tons
5 tons
10 tons
20 tons or larger

However, furnace capacity is not the same as production capacity.

For example, a 1-ton induction furnace does not automatically produce exactly 1 ton of finished castings every hour.

Actual output depends on:Furnace capacity × number of heats × utilization × metal yield

Therefore, the first step is to determine how much molten metal your foundry actually requires.

Step 1: Calculate Your Required Daily Molten Metal Output

Start with the production target.

Suppose your foundry needs:

20 tons of good castings per day

and your overall metal yield from molten metal to acceptable castings is:80%

Then the required molten metal is:Required molten metal = Good casting output ÷ Metal yield

Therefore:20 tons ÷ 0.80 = 25 tons/day

Your melting system must therefore supply approximately 25 tons of molten metal per day, not merely 20 tons.

This distinction is important because foundries may lose metal through:

Gating systems
Risers
Slag
Oxidation
Spillage
Process losses
Rejected castings

Always calculate the furnace requirement from the actual molten metal demand, rather than finished casting weight alone.

Step 2: Calculate the Required Melting Rate

Next, determine how many effective melting hours are available each day.

Assume:

Required molten metal: 25 tons/day
Effective melting time: 16 hours/day

The theoretical required melting rate is:25 ÷ 16 = 1.56 tons/hour However, a foundry rarely operates at 100% utilization.

Time is lost during:

Charging
Slag removal
Temperature measurement
Sampling
Alloy adjustment
Tapping
Furnace inspection
Maintenance
Shift changes
Production interruptions

Suppose the expected furnace utilization is 85%.

Then:Required furnace melting rate = 1.56 ÷ 0.85 = 1.84 tons/hour

In this example, the melting system should therefore be designed to provide approximately 1.84 tons/hour or more.

Step 3: Determine the Required Batch Capacity

Once the hourly melting requirement is known, calculate the appropriate furnace batch size.

A simplified relationship is:Required Furnace Capacity = Required Melting Rate × Melting Cycle Time

For example:

Required melting rate = 1.84 tons/hour
Complete batch cycle = 60 minutes

The theoretical furnace capacity would be approximately:1.84 × 1 = 1.84 tons

A practical selection might therefore move to the next suitable standard furnace size rather than specifying exactly 1.84 tons.

For example, a 2-ton induction furnace could be evaluated.

However, this is only a preliminary calculation.

You must still verify whether the selected furnace and power supply can actually melt the required metal within the assumed cycle time.

Step 4: Calculate the Complete Melting Cycle

One of the most common mistakes is calculating furnace capacity using melting time alone.

A furnace cycle may include:

Charging
Initial melting
Additional charging
Complete melting
Slag removal
Composition adjustment
Temperature adjustment
Sampling
Holding
Tapping

Suppose a 2-ton furnace requires:

Charging: 10 minutes
Melting: 45 minutes
Slagging and composition adjustment: 10 minutes
Temperature adjustment: 5 minutes
Tapping: 5 minutes

Total cycle:10 + 45 + 10 + 5 + 5 = 75 minutes

Therefore, theoretical heats per hour are:60 ÷ 75 = 0.8 heats/hour

For a 2-ton furnace:2 × 0.8 = 1.6 tons/hour

The actual production capacity is therefore approximately 1.6 tons/hour before additional production losses are considered.

This is why furnace tonnage alone cannot determine foundry output.

Step 5: Match Furnace Capacity With Power

After calculating furnace capacity, determine whether the selected power supply can achieve the required melting rate.

For an induction furnace, melting performance depends strongly on:

Rated power
Furnace capacity
Metal type
Charge condition
Starting temperature
Furnace lining condition
Electrical efficiency
Thermal efficiency
Operating practice

The basic energy relationship is:Melting Time ≈ Required Energy ÷ Effective Furnace Power

For example, if a melting process requires a certain amount of electrical energy per ton, increasing effective furnace power can generally reduce melting time—provided that the furnace body, coil, power supply, cooling system, and electrical infrastructure are designed for that power level.

Therefore, when comparing two induction furnaces of the same nominal capacity, do not compare tonnage alone.

Compare:

Furnace capacity
Rated power
Estimated melting time
Energy consumption per ton
Melting rate per hour

How Much Power Does an Induction Furnace Need Per Ton?

There is no universal kW-per-ton value that applies to every induction furnace.

Power requirement depends on:

Steel, iron, copper, aluminum, or other metal
Furnace capacity
Starting charge temperature
Required tapping temperature
Power frequency
Furnace efficiency
Charge density
Desired melting speed

A supplier should therefore provide the expected performance under clearly defined operating conditions.

When requesting a quotation, ask for:Rated furnace capacity + rated power + metal type + cold-start melting time + tons/hour + expected kWh/ton

This makes quotations much easier to compare.

Step 6: Consider the Metal You Are Melting

Different metals require different amounts of energy because their:

Melting temperatures differ
Specific heat capacities differ
Latent heats of fusion differ
Electrical properties differ
Pouring temperatures differ

For example, a furnace selected for:1 ton of aluminum

should not automatically be assumed to have the same production performance when melting:1 ton of steel.

Common induction furnace applications include:

Cast Iron

Commonly used for:

Pump bodies
Machine bases
Automotive castings
Pipes
General engineering castings

Carbon and Alloy Steel

Used for:

Machinery components
Mining parts
Wear-resistant castings
Tool and mold materials

Stainless Steel

Requires appropriate temperature and composition control.

Copper and Copper Alloys

Furnace design and operating parameters should be matched to the alloy and required process.

Aluminum

Requires different melting temperatures and furnace operating conditions from ferrous metals.

Always tell the furnace manufacturer exactly what metal you intend to melt.

Step 7: Calculate the Number of Furnaces Required

One large furnace is not always the best solution.

Suppose your foundry requires:4 tons/hour

You could potentially evaluate:

One larger furnace
Two medium-sized furnaces
Multiple smaller furnaces

The correct arrangement depends on production organization.

Two furnaces may provide operational advantages because one furnace can be melting while another is:

Tapping
Holding
Being charged
Receiving maintenance
Changing alloy grades

For continuous foundry production, multiple furnace bodies can also provide greater production flexibility.

Step 8: Check Your Electrical Infrastructure

A larger induction furnace also requires greater electrical infrastructure.

Before selecting the furnace, check:

Incoming power capacity
Transformer rating
Supply voltage
Grid stability
Cable capacity
Switchgear
Power factor requirements
Cooling-system power
Auxiliary equipment power

A foundry may calculate that a large furnace provides the ideal production capacity but discover that its existing transformer cannot support the required electrical load.

This should be evaluated before equipment purchase.

Step 9: Calculate Cooling-System Capacity

Induction furnaces generate significant heat in:

Induction coils
Power supply
Capacitors
Water-cooled cables
Electrical components

Therefore, increasing furnace power usually increases cooling requirements.

The cooling system may include:

Closed cooling tower
Heat exchanger
Circulation pumps
Water tank
Filters
Temperature monitoring
Pressure monitoring
Flow monitoring
Emergency water supply

Do not select a furnace first and treat cooling as an afterthought.

The furnace + power supply + cooling system should be engineered as one system.

Step 10: Add Capacity Margin

Running a melting department permanently at its theoretical maximum output creates operational risk.

Actual production can be affected by:

Difficult charge materials
Alloy adjustments
Furnace relining
Power fluctuations
Cooling problems
Operator delays
Maintenance
Casting-line interruptions

Therefore, some production margin should normally be considered.

The correct margin depends on:

Production stability
Number of furnaces
Maintenance strategy
Casting schedule
Required redundancy

Avoid automatically adding an arbitrary percentage without analyzing the actual production process.

Example: Induction Furnace Capacity Calculation for a Foundry

Consider a foundry with the following requirements:

Finished casting production: 30 tons/day
Metal yield: 80%
Operating time: 20 hours/day
Furnace utilization: 85%

1. Calculate Molten Metal Demand

30 ÷ 0.80 = 37.5 tons/day

The melting department must therefore produce approximately 37.5 tons of molten metal per day.

2. Calculate Hourly Requirement

37.5 ÷ 20 = 1.875 tons/hour

3. Correct for Furnace Utilization

1.875 ÷ 0.85 = 2.21 tons/hour

Therefore, the melting system should be capable of approximately:2.2 tons/hour or more

4. Select Candidate Furnace Capacity

If a proposed furnace can reliably melt and tap approximately 2.5 tons/hour under the foundry’s actual operating conditions, it may provide sufficient capacity.

However, the final selection should still verify:

Metal type
Furnace power
Complete heat cycle
Transformer capacity
Cooling system
Production schedule
Casting-line demand
Maintenance allowance

Induction Furnace Capacity Calculation Formula

For preliminary foundry planning, you can use:

Required Molten Metal per Day = Finished Casting Output ÷ Metal Yield

Then:Required Melting Rate = Required Molten Metal per Day ÷ Effective Production Hours

If utilization has not already been included:Design Melting Rate = Required Melting Rate ÷ Furnace Utilization

Finally:Approximate Furnace Capacity = Design Melting Rate × Complete Batch Cycle Time

where cycle time is expressed in hours.

This provides a practical starting point for furnace selection.

Example Induction Furnace Selection Table

Foundry Requirement	Parameter
Finished casting target	30 tons/day
Metal yield	80%
Required molten metal	37.5 tons/day
Effective operating schedule	20 hours/day
Theoretical molten metal demand	1.875 tons/hour
Furnace utilization	85%
Required system melting rate	Approx. 2.21 tons/hour

This table demonstrates why a foundry producing 30 tons of castings per day may require substantially more than 30 tons/day of theoretical furnace output.

III.How to Choose Between One Large Furnace and Two Smaller Furnaces

This is an important decision for foundry planning.

One Large Furnace

May offer:

Simpler plant layout
Fewer furnace bodies
Potentially lower auxiliary-equipment complexity

But it can also create a larger production interruption if the furnace is unavailable.

Two Smaller Furnaces

May provide:

Greater production flexibility
Easier alloy changes
Better maintenance scheduling
Production redundancy
Better coordination between melting and pouring

However, the initial equipment configuration and control system may be more complex.

The correct choice should be based on the complete production flow rather than furnace capacity alone.

IV.Conclusion

To calculate induction furnace capacity for your foundry, first determine the required finished casting output, correct it for metal yield, calculate the molten metal demand per hour, account for realistic furnace utilization, and then match the required melting rate with furnace batch capacity, cycle time, and power. Do not select an induction furnace based on tonnage alone. The correct system should balance tons per hour, melting time, furnace power, energy consumption, electrical infrastructure, cooling capacity, and production flexibility.

If you are unsure whether your foundry needs a 1-ton, 2-ton, 5-ton, 10-ton, or larger induction furnace, provide your metal type, daily production target, working hours, batch size, and available transformer capacity. These parameters can be used to determine a suitable furnace capacity and power configuration.

Click “Request a Quote” to get a customized solution.

V. FAQ

1. How do I calculate induction furnace capacity?

First, calculate the required daily volume of molten iron and divide it by the number of effective operating hours; then, adjust this figure based on the furnace utilization rate, and finally, use the complete melting cycle to work backward to determine the necessary capacity per batch.

2. What size induction furnace do I need for my foundry?

Choosing the right furnace size depends on several factors: your required hourly throughput (in tons), the weight of a single batch, the type of metal being melted, the melting cycle duration, your production scheduling, the amount of molten metal required by the casting line, and the power supply capacity available at the site.

3. How many tons per hour can an induction furnace melt?

Melting rate is influenced by furnace capacity, rated power, type of metal, condition of the furnace charge, furnace efficiency, and operating practices.

4. How much power is required for an induction furnace?

The required power depends on the furnace capacity, type of metal, target melting time, tapping temperature, furnace efficiency, and actual operating conditions.

5. Is a bigger induction furnace always more efficient?

No. Choosing a furnace that is too large leads to higher capital investment, increased power supply requirements, and greater heat loss—all while actually reducing operational flexibility.

Supplier

Luoyang Anjing Intelligent Equipment Co., Ltd. is an enterprise dedicated to the research, development, production, sales, and technical services of heat treatment equipment such as high-temperature electric furnaces. We produce laboratory, vacuum, industrial, and medium frequency furnace, covering a temperature range from -100℃ to 2600℃, serving industries such as new energy, semiconductors, and advanced materials. We can provide customized solutions based on specific atmosphere, ultra-high temperature, and intelligent control system requirements. Please feel free to contact us if you are interested.