NOTE.
I suspect Your best option to try is resistance welding with inert-gas purge/cooling. Or perhaps ultrasonic welding with/WO inert-gas purge/cooling.
Problem: High level of cleanliness/deoxidation of the wire-braid-ends being splice welded together is probably a mandatory 'no-brainer'.
Found following reference for resistance welded [braided/twisted] wires to terminals... may provide insight... although it is specifically NOT for splice welding wires together.
SAE USCAR-38 PERFORMANCE SPECIFICATION FOR ULTRASONICALLY WELDED WIRE TERMINATIONS...
1. SCOPE
This specification defines test methods and performance criteria for evaluating ultrasonically welded wire-to-terminal
metallurgical bonds. The examples used are specific to the linear weld type of process equipment. USCAR-38 is not
applicable for 'splice welding'. The specification is applicable to wire-on-pad configurations with a typical weld shown in
Figure 1. This test specification subjects parts under test to environmental exposures to simulate a lifetime of field
exposure for a road vehicle. Exposures called-out in this specification include Thermal Shock, Temperature Humidity
Cycling and mechanical abuse. This test specification is intended to evaluate the strength and performance of the
interface between wires to an electrical terminal. Validation of the performance of the Terminal is a separate task and can
be accomplished using a component validation test such as SAE/USCAR-2, which evaluates whether the entire
connection system is acceptable.
Regards, Wil Taylor
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