Table of Contents
Copper, primarily existing in monovalent and divalent forms in compounds, is a metal element known for its ductility and malleability. As a prominent conductor of heat and electricity, copper is naturally occurring and widely found in various ores such as brass ore, chalcopyrite, bornite, cuprite, and malachite. It is utilized in industries, engineering technologies, and craftsmanship in metallic form or as alloys. Being a highly reflective material, welding copper has been a challenging technological hurdle, especially in industries that involve welding copper components, where ensuring both the solidity and smooth appearance of the weld seam is crucial.
Challenges in Copper Welding
Copper, a common metal material with excellent conductivity and thermal properties, finds extensive applications in electronics, electrical engineering, construction, and manufacturing. However, welding copper poses several challenges, including:
High Thermal Conductivity
Copper's extremely high thermal conductivity means that heat easily spreads throughout the workpiece during welding. This requires higher welding temperatures and shorter welding times to ensure thorough melting of the welding area without excessive heating of the entire workpiece.
Oxidation Issues
Copper readily reacts with oxygen to form an oxide layer, adversely affecting the welding process. The presence of an oxide layer can degrade the quality of the weld seam, reducing welding strength. Precautions such as using nitrogen or other shielding gases are often necessary before welding to prevent oxidation.
High Melting Point
Copper has a relatively high melting point, necessitating the use of high-temperature welding equipment. Careful control of the welding temperature is required to avoid heat damage to equipment and workpiece surfaces.
Differential Thermal Expansion
Compared to other metals, copper has a relatively high coefficient of thermal expansion. In welding composite materials or dissimilar metals, differences in thermal expansion coefficients may lead to residual stress and deformation, requiring special attention.
Welding Residual Stress
Due to significant temperature changes during welding, copper is prone to welding residual stress. This stress can result in part instability or cracking, making post-weld heat treatment and proper cooling essential.
To overcome these challenges, welding copper often involves specific measures, including choosing suitable welding methods (such as gas metal arc welding, arc welding, laser welding, etc.), using appropriate welding materials, preheating workpieces, and employing the right atmosphere protection. Additionally, operators need to possess professional welding skills and experience to ensure process control and quality.
Common Copper Welding Methods
There are various methods for welding copper, and the choice depends on specific application requirements and workpiece characteristics. Some common copper welding methods include:
Gas Metal Arc Welding (GMAW)
Also known as Metal Inert Gas (MIG) welding, GMAW is a prevalent semi-automatic or fully automatic welding method. In GMAW, an arc is formed between the welding gun and the workpiece, heating and melting the copper welding wire, while an inert gas (usually argon) is used to shield the weld seam, preventing oxidation.
Arc Welding
This includes manual metal arc welding (SMAW) and tungsten inert gas welding (GTAW). SMAW uses a welding machine and welding rod, while GTAW employs inert gas (usually argon) as a shielding gas. These methods can be suitable for various thicknesses and shapes of copper.
Laser Welding
Laser welding is a highly precise welding method suitable for applications with stringent requirements for welding quality and appearance. Laser welding can achieve a very small welding heat-affected zone, minimizing deformation and welding residual stress.
Resistance Welding
Resistance welding utilizes the heat generated by electric current passing through the workpieces to melt the surface momentarily, followed by applying pressure to join the two pieces together. This method is commonly used for welding copper wires and electronic components.
Plasma Arc Welding (PAW)
Plasma arc welding is a high-energy density welding method suitable for thicker copper materials. In PAW, a plasma arc is generated using inert gas, and the energy of the plasma flow is controlled to melt the workpiece surface.
Ultrasonic Welding
Ultrasonic welding involves momentarily melting the workpiece surface through ultrasonic vibrations, followed by cooling and solidification to achieve welding. This method is suitable for applications sensitive to heat.
When selecting the appropriate copper welding method, factors such as material thickness, shape, quality requirements, and production efficiency need to be carefully evaluated and considered. Different welding methods have their advantages and applicability, necessitating a thorough assessment in practical applications.
Principles and Advantages of Laser Welding Machine for Copper Materials
Laser welding is an efficient and precise welding method that utilizes a high-energy density laser beam as the heat source. It represents a crucial aspect of the application of laser material processing technology. Initially used in the 1970s for welding thin-walled materials and low-speed welding, laser welding is a type of heat conduction welding. In this process, the laser radiation heats the surface of the workpiece, and the surface heat diffuses inward through heat conduction. By controlling parameters such as laser pulse width, energy, peak power, and repetition frequency, the workpiece is melted, forming a specific molten pool. Due to the high energy density, low deformation, narrow heat-affected zone, high welding speed, ease of automatic control, and elimination of post-processing, laser welding has become an essential means of metal material processing and manufacturing in recent years. Its applications span across industries such as automotive, aerospace, shipbuilding, hardware, medical devices, batteries, sensors, and home appliances.
The application of laser welding machines in welding copper materials offers significant advantages, making it an ideal choice for specific applications:
High Energy Density
Laser welding machines generate a beam with high energy density, allowing rapid energy transfer during the welding process. This facilitates quick heating of the welding seam area to achieve fast and efficient welding.
Precision Control
Laser welding provides precise welding control, enabling highly accurate adjustments to welding depth, weld seam shape, and welding speed. This is crucial for applications with high requirements for welding quality and appearance.
Small Heat-Affected Zone
Due to the concentration of energy in a small area, laser welding produces a relatively small heat-affected zone. This helps reduce thermal deformation of copper materials and minimizes welding residual stress.
Non-contact Welding
Laser welding is a non-contact welding method, with no electrode directly touching the workpiece surface. This helps avoid introducing external impurities and reduces electrode wear, especially suitable for applications requiring weld seam purity.
Suitable for Complex Shapes
Laser welding is applicable to welding workpieces with complex shapes, as the laser beam can be flexibly positioned and moved along a predetermined path, adapting to various welding requirements.
No Filler Material Required
In certain cases, laser welding can achieve welding without the need for filler materials. This is advantageous for applications that demand impurity-free and defect-free weld areas.
Remote Operation
Laser welding machines can be remotely controlled through Computer Numerical Control (CNC) systems, allowing operators to monitor and adjust the welding process in a safe environment.
While laser welding offers numerous advantages in welding copper materials, factors such as high equipment and energy costs, as well as the specialized requirements for operators, need to be considered. Therefore, when choosing a welding method, a comprehensive assessment of specific application requirements and practical considerations is essential.
Widespread Application of Copper Materials Will Drive Laser Processing Demand
Copper, being an excellent conductor of electricity, finds extensive applications in power, cables, motors, switches, circuit boards, capacitors, communication devices, telecommunication stations, and more. With its superior thermal conductivity, copper is widely used in heat exchangers, refrigeration equipment, household appliances, pipelines, and other areas. Additionally, copper has seen significant use in the battery industry, particularly in recent years, where laser welding technology has been adopted for battery encapsulation and power battery cell welding. Copper has the broadest and most extensive application in the electrical and electronic industries, accounting for over half of the total consumption. As laser processing technology gradually matures and is concurrently applied to copper material components, the future is expected to witness laser processing for copper materials driving demand for laser equipment, creating a new growth point in the laser industry, estimated to exceed tens of billions of yuan.
High Reflectivity of Copper Prompts the Emergence of Green and Blue Light
Among metallic materials, laser processing of steel has been explored and matured, whereas processing of high-reflectivity materials is still under exploration, especially copper and aluminum materials. Copper, with its excellent conductivity and high reflectivity, is extensively used in cables, household appliances, consumer electronics, electrical equipment, electronic components, and batteries. Over the years, laser technology has endeavored to explore copper material processing but has been constrained by the nature of copper.
Primarily, the high reflectivity of copper to the most common 1064nm infrared laser is as high as 90%. Secondly, copper’s excellent thermal conductivity quickly diffuses localized heat, making it challenging to achieve the desired processing effect. Thirdly, opting for higher power lasers for processing leads to copper material deformation. Even after completing welding, defects and incomplete welds are prone to occur.
Comparison of Reflectivity Between Laser Wavelengths of 1064nm and 532nm
|
Material
|
1064nm
|
532nm
|
|---|---|---|
|
Copper
|
90%
|
45%
|
|
Gold
|
98%
|
42%
|
After years of exploration, it has been discovered that utilizing shorter-wavelength green and blue light lasers for welding copper materials is more suitable, propelling the development of green and blue light lasers.
Summary
In summary, laser welding machines have overcome traditional challenges in copper material welding by leveraging advantages such as high energy density, precise control, and a small heat-affected zone. This has effectively addressed issues like high thermal conductivity, oxidation, and high melting points encountered in copper welding. As the demand for copper materials increases, laser processing technology is poised to become a key driving factor. Additionally, the application of green and blue light lasers opens up new possibilities for laser processing of copper materials, propelling a new round of growth in the laser industry. This development trend not only elevates the level of copper material processing but also provides reliable and efficient solutions for the modern manufacturing sector.
