Fusion of Copper Materials
(adapted from The Socachim Handbook of Fusion Methods)

For Phoenix Fusion Machines

Introduction

A fusion method for copper materials such as:

Copper Sulphide (Cu: 20-30%; S: 25-35%; Fe: 20-30%; SiO2: 5-10%)
Copper Matte (Cu: 40-55%; S: 15-25%; Fe: 15-25%; Zn: 2-5%)

Materials

Flux XRF Scientific LT100 and LT66:LM34
Flux additives
Oxidizer Mix Lithium nitrate
Non-wetting agent Lithium Bromide (250g/L)

Method

1. Weigh 0.4 g of dried/grinded samples, 8.0g of lithium borate flux, 2.0 g of oxidizer and mix them together.
2. Ensure mixture is rigorously mixed to achieve optimal contact between the sample and flux
3. Transfer the mixture into the crucible and about add about 8 drops of lithium bromide ensure mixture is rigorously mixed to achieve optimal contact between the sample and flux on top
4. Start the fusion program as given below
5. When cooling has finished, remove the bead from the mould

Dilution sample:flux:oxidizer ratio is 0.4:8:2

Comments

Samples containing copper sulphide are prepared for XRF analysis by oxidising the weighed powder with the appropriate quantity of oxidant. The sample is mixed with the lithium nitrate and the flux.

Samples containing copper have the tendency to stick to the crucibles and moulds. The fused mixture must be cooled directly in order to avoid all crystallization. In addition, the mould must be polished regularly as even a small asperity can lead to crystallisation

Enhanced oxidation of the sample has been observed by using the oxygen injection option available on Phoenix Fusion Machines. An oxygen injector, placed above the crucible, can further enrich the atmosphere within the mix and help prevent the mixture sticking to the walls of crucible.

Variations

For Copper sulphide (Cu: 65-70%; Fe: 5-10%)

Dilution sample:flux:oxidizer ratio is 0.2:8:2

Fusion Program

Premelt 850°C 7 minutes
Melting, without swirling, 1185°C-1225°C# 3 minutes
Melting, with swirling, 1185°C-1225°C# 4 minutes
Mould control (mould preheating step), 1150°C 1 minute
Cooling (bi-level) Temperature 1 0 minutes
Cooling (bi-level) Temperature 2 3 minutes

# Actual temperature dependent on flux type used.