Copper to Tungsten Welding: Joining Metals with 2,337C Melting Point Difference 

Copper melts at 1085°C. Tungsten melts at 3422°C. The 2,337°C gap between them is the largest melting point difference in our entire weld parameter database. To put this in perspective, the melting point of tungsten exceeds the boiling point of many common metals. No conventional fusion welding process can produce a reliable Cu-W joint.

The metallurgical challenges go beyond the temperature gap. Copper and tungsten have zero mutual solubility — they do not alloy at any composition or temperature. There is no solid solution, no intermediate phase, and no intermetallic compound in the Cu-W phase diagram. The two metals are fundamentally immiscible. Brazing is possible but introduces a third material and a joint that weakens at elevated temperatures.

How Percussion Welding Bridges the Gap

The percussion welding arc plasma reaches temperatures far exceeding both melting points. The arc discharge creates a localized plasma channel at roughly 6,000-10,000°C between the wire tips. At these temperatures, both copper and tungsten surfaces melt simultaneously regardless of their individual melting points. The forging stroke then drives the molten surfaces together before either can solidify or oxidize.

Because there is no mutual solubility, the joint interface is a direct mechanical and metallic bond between the two pure metals. There is no alloy zone and no intermetallic layer. The bond depends on intimate atomic contact achieved by the forging pressure acting on the momentarily molten surfaces.

Verified Weld Parameters: Copper to Tungsten (Cu in Movable Clamp)

Wire Dia.	Main V	Time (ms)	Cap	Forge V	Tip
0.020"	48V	5.50	Cap3	40V	Long
0.030"	48V	1.00	Cap3	40V	Long
0.050"	48V	1.00	Cap3	55V	Long

Verified Weld Parameters: Tungsten to Copper (W in Movable Clamp)

Wire Dia.	Main V	Time (ms)	Cap	Forge V	Tip
0.015"	40V	2.50	Cap2	65V	Long
0.063"	48V	2.00	Cap3	55V	Long

Parameter Analysis

Several features of these parameter sets are notable:

• Moderate main voltages: Despite the extreme melting point gap, main voltages range from 40V to 48V. The arc plasma temperature far exceeds both melting points regardless of voltage setting. The moderate voltage prevents excessive vaporization of the copper, which would boil (2562°C) before the tungsten melts.
• All Long tips: Every Cu-W parameter set uses Long tips. The extended electrode spacing creates a longer arc that distributes energy more evenly across both wire faces, compensating for the extreme thermal property mismatch.
• Variable weld times: The 5.50ms time for 0.020" Cu-to-W is unusually long for percussion welding. At very small diameters, the tungsten wire has extremely low thermal mass and requires a sustained arc to bring the interface to tungsten's melting temperature without simply vaporizing the copper.
• Higher forge voltage in W-to-Cu: When tungsten is the moving electrode, forge voltages increase (55-65V versus 40-55V). Tungsten is much harder and denser than copper, requiring more forging energy to achieve proper upset at the interface.

Applications

• Lighting Filaments: Tungsten filaments joined to copper lead-in wires in incandescent and halogen lamp assemblies.
• EDM Electrodes: Copper feed conductors bonded to tungsten EDM electrodes for electrical discharge machining.
• Aerospace Thermocouple Probes: Tungsten-rhenium thermocouple elements connected to copper extension wires for high-temperature gas turbine monitoring.
• Vacuum Electronics: Tungsten emitters and grids joined to copper conductors in vacuum tube and electron gun assemblies.

Related Resources

View the complete Cu-W parameter database at Weld Schedules.