Induction Melting Copper

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Brand: HLQ

Description

Induction Melting Copper, Brass and Bronze in Small-Batch Furnaces

Quick Answer

Induction melting copper uses an IGBT medium-frequency power supply and a water-cooled coil to induce eddy currents in the copper charge. The charge is heated by Joule heating, melts, and is stirred electromagnetically.

For small batches, HLQ data gives:

5–100 kg furnaces: 15–75 kW at 2,000–8,000 Hz, about 15–45 minutes per heat
5–15 kg jewelry and art casting: 15–25 kW at 4–8 kHz
10–100 kg laboratory melting: 25–75 kW at 2–4 kHz

Use a magnesia lining for pure copper and a silica lining for brass. For brass, keep the melt at 950–1,020 °C to limit zinc loss.

Small induction copper melting furnace with manual tilting frame and IGBT power supplies — Small manual-tilting copper melting furnace with its induction power supply.

What is Induction Melting Copper?

Induction melting copper is coreless crucible melting of copper and copper alloys with electromagnetic induction. The system has three parts: an IGBT solid-state power supply, a water-cooled copper coil, and a refractory-lined furnace body with a tilting mechanism.

This page covers the small capacity class. For the full 5–5,000 kg range, see the copper melting induction furnace page.

Capacity tier	Capacity	Power	Frequency	Typical cycle	Primary market
Small / laboratory	5–100 kg	15–75 kW	2,000–8,000 Hz	15–45 min/heat	Jewelry, R&D, art casting, small foundry
Medium / workshop	100–1,000 kg	75–750 kW	500–2,500 Hz	45–120 min/heat	Brass/bronze foundry, die casting, valves
Large / industrial	1,000–5,000 kg	750–3,500 kW	250–1,000 Hz	90–240 min/heat	Recycling, wire rod, continuous casting

Molten copper in an induction crucible furnace — Molten copper in an induction crucible.

Key Applications

Small copper and brass induction melting selection chart: power and frequency for jewelry, laboratory, bronze investment casting and small brass foundry — Application and selection chart: power and frequency by application, with 5–50 kg class data.

Application	Alloy	Capacity	Key requirement
Jewelry and art casting	Pure Cu, Cu-Au alloys	5–30 kg	Precise temperature, small batch, clean melt
Metallurgical R&D, alloy development	All Cu alloys	5–100 kg	Flexible alloy switching, composition control
Investment casting of precision parts	Bronze, Al-bronze, Cu-Ni	50–300 kg	Melt cleanliness, temperature uniformity
Bronze bearing and bushing casting	C93200, C90500, C95400	100–500 kg	Tin and aluminum distribution, low porosity
Brass valves and fittings	C36000, C28000, C37700	200–1,000 kg	Zinc-loss control, consistent chemistry

Stirring molten copper alloy in a small induction furnace.

Suitable Materials

Material	Grade	Melting range	Recommended lining	Special handling
ETP copper	C11000	1,083–1,100 °C	Magnesia (MgO ≥ 90%)	Oxygen control; charcoal cover
Oxygen-free copper	C10200	1,083–1,095 °C	Magnesia or alumina-magnesia	Inert gas blanket
Cartridge brass 70/30	C26000	915–955 °C	Silica (SiO₂ ≥ 97%)	Zinc fuming; fume extraction
Free-cutting brass	C36000	885–900 °C	Silica or alumina-silica	Lead content; ventilation
Tin bronze	C90300, C90500	850–1,000 °C	Silica or alumina	Phosphorus deoxidation
Aluminum bronze	C95400, C95500	1,030–1,100 °C	Alumina (Al₂O₃ ≥ 90%)	Al₂O₃ inclusion control; careful skimming
Cupronickel 90/10	C70600	1,100–1,145 °C	Magnesia or chrome-magnesia	Nickel addition sequence
Silicon bronze	C65500	970–1,025 °C	Silica or alumina	Good fluidity
Beryllium copper	C17200	870–980 °C	High-purity alumina	BeO fume is toxic; sealed enclosure mandatory

Brass details: induction melting brass.

Working Principle

How induction melting copper works: IGBT power supply, capacitor bank, water-cooled coil, refractory lining, flux cover and electromagnetic stirring — Principle diagram: IGBT supply, LC resonant circuit, coil, lining, copper charge and stirring.

Power conversion: 3-phase AC is converted to DC, then to medium-frequency AC by the IGBT inverter.
Resonant circuit: The coil and capacitor bank form an LC tank circuit.
Magnetic field: The coil current creates an alternating field in the crucible bore. Copper is non-magnetic (µr ≈ 1).
Eddy currents: Currents are induced in the surface layer of the charge.
Joule heating: As copper heats, its resistivity rises and coupling improves through the melt cycle.
Electromagnetic stirring: Lorentz forces circulate the bath, distributing zinc, tin and alloying elements.
Temperature control: Feedback from a thermocouple adjusts the power output.

Background: how an induction heater works.

Current penetration depth in solid copper at 20 °C

Frequency	Penetration depth	Best-suited capacity
8,000 Hz	0.74 mm	5–20 kg
4,000 Hz	1.05 mm	20–100 kg
2,000 Hz	1.48 mm	100–300 kg
1,000 Hz	2.10 mm	300–800 kg

The very shallow penetration in cold copper is why a solid copper charge couples poorly at a cold start.

Technical Specifications

Parameter	5–50 kg class (HLQ data)
Rated power	15–50 kW
Operating frequency	2,000–8,000 Hz
Input voltage	3 × 380 V / 415 V
Power factor	≥ 0.93
Melting rate (pure Cu)	10–50 kg/h
Specific energy (Cu ingot)	420–520 kWh/t
Operating temperature	Up to 1,350 °C
Temperature accuracy	±8 °C
Lining material	Alumina / magnesia
Lining life	80–200 heats
Tilting	Manual or small hydraulic
Cooling water	5–20 m³/h at 0.2–0.3 MPa
Control interface	Digital panel / 7″ HMI
Protection class	IP23

Theoretical heat demand

Batch	5 kg	15 kg	50 kg	100 kg
Copper heated to ≈ 1,150 °C (≈ 0.19 kWh/kg)	≈ 0.9 kWh	≈ 2.9 kWh	≈ 9.5 kWh	≈ 19 kWh

Physical values: sensible heat plus latent heat. HLQ lists 420–520 kWh/t actual specific energy for this class; the difference is coil, lining and heat loss.

Induction smelting copper process in a tilting furnace — Induction melting copper in a tilting furnace.

Recommended Model Selection

Application	Material	Capacity	Power	Frequency	Key feature
Jewelry / art casting	Pure Cu, Cu-Au	5–15 kg	15–25 kW	4,000–8,000 Hz	Compact; tilt pour; inert gas option
Laboratory / R&D	All Cu alloys	10–100 kg	25–75 kW	2,000–4,000 Hz	Wide alloy flexibility
Bronze investment casting	C90300, C95400	50–300 kg	50–200 kW	1,000–2,000 Hz	Melt cleanliness; tight temperature control
Small brass foundry	C26000, C36000	100–300 kg	75–200 kW	1,000–2,500 Hz	Zinc-loss control; fume extraction

Example power supply: DW-MF-110KW

Parameter	Published value
Maximum oscillation power	110 kW
Frequency	1–20 kHz
Input	3-phase 380 V ±10%, 50/60 Hz; maximum input current 170 A
Inverter	IGBT, parallel inverter
Cooling water	> 0.3 MPa, 10 L/min
Duty cycle	100% at 40 °C
Generator / transformer size	560 × 270 × 470 mm / 550 × 300 × 420 mm
Protection	Over-voltage, over-current, over-temperature, phase loss, water shortage

Details: DW-MF-110KW copper melting power supply. For 100–1,000 kg, see the induction copper melter for brass and bronze.

Process Workflow

Small copper melting process flow: preheat, prepare, load, ramp power, add charge, flux cover, alloy, deoxidise, skim, temperature, sample, pour — Process flow chart for the 5–50 kg class.

Step	5–50 kg furnace practice
1. Preheat and inspection	Visual check; 15 min preheat at 30% power
2. Charge preparation	Weigh ingots or scrap; check for contamination
3. Initial loading	Dense ingots first; manual loading
4. Power ramp-up	30% → 100% over 5–10 min
5. Progressive charging	Add the remaining charge as the first batch melts
6. Flux	Charcoal or borax cover, applied manually
7. Alloying	Manual master-alloy additions
8. Deoxidation	P-Cu addition; manual lance purge
9. Dross removal	Manual skimming
10. Temperature check	Immersion thermocouple
11. Composition check	Sample for laboratory analysis
12. Pouring	Manual tilt; ladle or direct mould pour

Workshop layout

For larger batches with hydraulic pouring, see the hydraulic tilting copper melting furnace. For rod, bar or strip output, see the continuous copper casting furnace.

Common Problems and Solutions

Problem	Likely cause	Solution
Excessive red Cu₂O dross	Poor flux cover, overheating, air exposure	Apply charcoal or borax after each charge; lower the holding temperature; inert gas for pure copper
Hydrogen porosity in castings	Wet or oily scrap, damp flux, poor deoxidation	Pre-dry scrap and flux; add 0.02–0.05% P-Cu; purge with dry argon
Zinc fuming with brass	Above 1,050 °C, long holding	Keep 950–1,000 °C, minimize holding, add zinc last, run fume extraction
Rapid lining erosion	Wrong lining for the alloy, overheating, poor sintering, thermal shock	Choose the lining by alloy; follow the sintering protocol; preheat the charge
Furnace fails to start	Coil insulation fault, water flow alarm, IGBT or capacitor fault	Check coil insulation (> 1 MΩ), water flow, IGBT diagnostics and capacitor fuses
Slow melting on a cold start	Solid copper’s shallow penetration depth gives poor coupling	Start with a dense, clean charge; keep a molten heel; ramp power gradually
Alloy out of specification	Charge error, volatile element loss, contaminated scrap	Recalculate the charge; add volatile elements last; use certified scrap

Engineering Selection Guide

Step	Parameter	Decision criteria	Impact
1	Required throughput	Net kg/h needed, with a 70% utilization factor	Minimum capacity and power
2	Alloy family	Pure Cu, brass, bronze, Cu-Ni, specialty	Lining, atmosphere, temperature range
3	Charge form	Ingot, returns, mixed or fine scrap	Energy use, coupling, charge preparation
4	Atmosphere	Open air, flux cover, inert gas, sealed	Oxygen-free and specialty alloys need sealed designs
5	Electrical supply	Voltage, capacity, harmonic limits	Cable, transformer and filter sizing
6	Temperature measurement	Copper at 1,083–1,300 °C	Type B thermocouple; Type K only marginal for brass and bronze

Throughput example: 800 kg of molten copper per 8-hour shift ÷ (8 h × 0.70) ≈ 143 kg/h of net melting rate.

Advantages and Limitations

Advantages	Limitations
No combustion, so no flue gas in contact with the melt	Higher capital cost than gas-fired furnaces
Electromagnetic stirring distributes zinc, tin and alloying elements	Solid copper couples poorly at a cold start
Precise temperature control (±8 °C in the small class)	Lining chemistry must match the alloy
One platform from pure copper to cupronickel	Brass melting needs fume extraction
No gas lines, flue stacks or combustion-air systems	Cooling water failure stops the furnace immediately
Scalable from 5 kg to 5,000 kg on the same technology	Beryllium copper needs a sealed enclosure and full exhaust filtration

Why Choose HLQ?

Strength	What it means
5–5,000 kg copper range	Small to industrial furnaces on one IGBT platform
Alloy-specific linings	Magnesia, silica, alumina or chrome-magnesia chosen by alloy
Published power supplies	For example DW-MF-110KW, 1–20 kHz, 100% duty at 40 °C
Protection functions	Over-voltage, over-current, over-temperature, phase loss, water shortage
Tilting options	Manual, small hydraulic or hydraulic
Process guidance	Flux, deoxidation, zinc-loss and lining practice for each alloy

10 Core FAQs

1. At what temperature does copper melt?

Pure copper melts at 1,083 °C. ETP copper is melted at about 1,083–1,100 °C, and brass at about 885–955 °C depending on grade.

2. How much power does a small copper furnace need?

15–25 kW for 5–15 kg jewelry casting and 25–75 kW for 10–100 kg laboratory melting.

3. Which frequency is used?

4–8 kHz for 5–15 kg, 2–4 kHz for 10–100 kg, and 1–2.5 kHz for 100–300 kg brass and bronze.

4. How long does a small heat take?

About 15–45 minutes per heat in the 5–100 kg class. The 5–50 kg class melts about 10–50 kg/h of pure copper.

5. Which lining should I use for pure copper?

Magnesia. Silica linings suffer chemical attack from Cu₂O. Brass normally uses silica.

6. How do I limit zinc loss when melting brass?

Keep the melt at 950–1,020 °C and never above 1,050 °C, minimize holding time, add zinc last, keep a flux cover and run fume extraction.

7. Which thermocouple should I use?

Type B for 1,083–1,300 °C. Type K is only marginal for lower-temperature brass and bronze.

8. Why is cold-start melting slow?

Solid copper is highly conductive, so the induced current flows in a very thin layer (0.74 mm at 8 kHz). Coupling improves as the copper heats.

9. Can copper scrap be melted?

Yes. Clean, large-section scrap can be charged directly. Fine scrap must be dried, and wet scrap must never go into a hot furnace.

10. How much energy does copper need?

In theory about 0.19 kWh/kg to heat copper to about 1,150 °C. HLQ lists 420–520 kWh/t actual specific energy for the 5–50 kg class.

HLQ-Induction-Melting-Copper-Brochure