In the electrolytic copper production system, cathode welding is one of the core processes that
determine the service life of electrode plates and electrolysis efficiency. With the development
of ultra-thin copper foil thickness below 6μm and the surge in demand for high-purity copper in
the new energy field, cathode welding technology is undergoing a transition from traditional
manual operation to intelligent, high-precision direction. In this paper, we will analyze the process
points of this technology, innovation breakthroughs and industry application trends.
Process principle and equipment composition
Cathode welding mainly refers to the electrolytic copper starter piece and titanium / stainless steel
motherboard for reliable connection process, the quality of which directly affects the uniformity of
the current distribution in the electrolysis process. Modern industrialized production mostly adopts
automated welding system, and the key modules include:
1. High-precision positioning mechanism
Adopting visual positioning and laser tracking technology to realize ±0.1mm level alignment accuracy of the
contact surface between the copper sheet and the motherboard.
Dynamic compensation device can eliminate 0.3-0.5mm displacement error caused by lifting deformation.
2. Energy precision control system
High-frequency inverter power supply (5-20kHz) with PID algorithm to control the welding temperature fluctuation within ±8℃.
Self-developed pulse waveform generator, supporting 0.1-2ms pulse width adjustment, adapting to different
thickness of copper (0.6-1.2mm)
3. Process quality monitoring unit
Infrared thermal imaging camera real-time monitoring of the melt pool temperature field, generating
three-dimensional heat distribution mapping of the welding area
Acoustic emission sensor captures the characteristic frequency of weld cracks (120-180kHz) and automatically
identifies defects in the weld.
The whole system can complete single-point welding within 12 seconds, and the tensile strength of the welded
joint is ≥85MPa, which is more than 90% of the strength of the copper base material.
Technical difficulties and innovative solutions
Three major technical bottlenecks faced by traditional cathode welding and corresponding solutions:
1. Copper and titanium dissimilar metal welding
Difficulty: copper (1083 ° C) and titanium (1668 ° C) melting point differences lead to the interface prone to
brittle compounds
Breakthrough: Development of gradient transition layer technology, through the nickel-based intermediate layer
(thickness of 50-80μm) to inhibit the generation of Cu-Ti intermetallic compounds, so that the conductivity of
the joints increased to 92% of pure copper.
2. Thin copper sheet thermal deformation control
Difficulty: 0.8mm below the copper sheet welding prone to wavy warping (deformation> 1.5mm/m)
Solution: Adopt electromagnetic constraint tooling with local water cooling system to compress the width of
heat-affected zone to less than 2mm, and the overall flatness error is ≤0.3mm/m.
3. Continuous production stability
Pain point: Electrode wear during batch operation leads to decreased consistency of welded joints.
Innovation: introduction of copper-chromium-zirconium alloy electrode cap, with adaptive wear
compensation algorithm, so that the diameter fluctuation of the welded joints after 5,000 times of continuous
welding <±0.15mm.
After a large copper smelter applied the above technology, the electrode plate replacement cycle was
extended from 3 months to 8 months, the current efficiency of the electrolyzer was increased by 1.2
percentage points, and the annual savings in maintenance costs exceeded 2 million yuan.
Process parameter optimization strategy
To realize high-quality welding, we need to focus on controlling five dimensional parameters:
Accurate matching of energy input
Current density: copper thickness of 0.8mm, the best current range of 6500-7200A
Pressurization time: pre-pressure (0.15s)-welding (0.08s)-pressure maintaining (0.2s) three-stage precision control
Interface pretreatment standard
Electrolytic polishing of copper sheet: surface roughness Ra≤0.8μm, thickness of oxide layer＜5nm
Titanium plate activation treatment: using hydrofluoric acid - nitric acid mixture (concentration ratio of 3:1) etching,
contact resistance reduced by 40%
Environmental control specifications
Argon gas protection purity ≥ 99.999%, flow control in 12-15L / min
Work area humidity to maintain 30% -45%, to prevent the copper surface adsorption of water vapor caused by porosity
Through the Response Surface Method (RSM) to optimize the combination of parameters, a project will be welding pass rate
from 89% to 97.5%, spatter rate reduced to less than 0.3%.
Industry Technology Evolution Trends
Cathode welding technology is breaking through in three directions:
1. Intelligent process system
Development of multi-spectral collaborative monitoring technology, synchronized acquisition of temperature, deformation,
arc spectra and other 12-dimensional data
Construction of welding quality prediction model to achieve self-optimization of parameters and real-time correction of defects
2. Green manufacturing transformation
Test solid-state high-frequency welding technology, saving more than 30% of electricity compared with traditional industrial
frequency welding machine.
Promote cadmium-free brazing materials (e.g. Cu-P-Ag alloy) to reduce welding fume toxicity by 70%.
3. Adaptation for special applications
Develop vacuum electron beam welding equipment to meet the oxygen content control of nuclear-grade copper (≤5ppm)
Development of flexible welding robots, adapted to the curved cathode plate (radius of curvature ≥ 800mm)
precision processing
Quality control and testing methods
In order to ensure welding reliability, advanced manufacturers have established four levels of quality defense:
Online monitoring layer
Visual measurement of welding joint diameter (accuracy ±0.02mm)
Loop resistance testing (standard value ≤ 3μΩ)
Offline laboratory analysis
Metallographic section observation of melt core penetration (requirement ≥ 80%)
SEM-EDS detection of interface element diffusion behavior
Service performance verification
Simulated electrolytic environment for 2000 hours salt spray test
Conductivity decay rate ≤2% after 200 thermal cycles (-20℃~150℃)
Big Data Traceability System
Each welding joint generates an independent ID, associated with equipment parameters, operators, material
batch and other information.
Continuous optimization of process capability index (CPK) through SPC statistical process control.
Conclusion
Innovations in cathode welding technology are reshaping the economics and reliability of copper electrolysis
production. From micro-interface control to macro-system integration, each technological advancement is
driving the copper processing industry in the direction of higher purity and lower energy consumption. For
production enterprises, building a digital twin system of welding process and continuously exploring the
integration and application of new materials and processes will become the core path to break through
the competitive barriers in the industry.