Influencing Factors Of Laser Welding
As one of the two basic types of laser welding (the other being heat transfer welding), laser deep-fusion welding is becoming more and more widely used. In order to obtain higher benefits from laser deep fusion welding, FANUCI has summarised the main influencing factors of this welding method for all welding users, including laser power density, welding speed, focal point position, shielding gas, workpiece joint assembly gap, material nature and other aspects, to help users avoid harm and maximise the use of the laser and laser equipment.
Laser Power Density
1. Laser power density is one of the key parameters affecting laser welding. Power density is the amount of energy delivered per unit area in a given time period. In laser welding, the power density of the laser beam affects the depth of melt, the welding speed and the quality of the weld.
Higher power densities generally result in deeper weld depths, faster welding speeds and higher weld quality. This is because higher energy concentrations create a larger melt pool and allow the metal to evaporate more quickly, resulting in deeper depths of melt and faster welding speeds.
2. However, high power densities can also lead to increased heat input, which can lead to distortion, cracking and other welding defects. It is therefore important to balance the power density with the welding speed, the thickness of the material to be welded and the required weld quality.
3. The optimum power density for laser welding depends on several factors, including the type and thickness of the material to be welded, the welding speed and the quality required of the finished product. Generally, higher power densities are preferred for thicker materials or where faster welding speeds are required, while lower power densities may be better for thinner materials or where a higher level of accuracy is required.
Welding speed
1. Heat input: The speed of the laser beam affects the heat input to the part. If the welding speed is too slow, the heat input will be higher, which may result in increased distortion and heat affected zone (HAZ) size. On the other hand, if the welding speed is too fast, the heat input will be lower and the weld may not be fully penetrated, resulting in a weaker weld.
2. Weld quality: The speed of the laser beam also affects the quality of the weld. Slower welding speeds will result in deeper weld depths and higher weld strengths. However, this can also lead to increased porosity and cracking due to prolonged exposure to the laser beam. In contrast, faster welding speeds may result in less depth of fusion and weaker welds, but with less risk of porosity or cracking.
3. Weld seam shape: Welding speed also affects the shape of the weld seam. Slower welding speeds will result in wider and deeper welds, while faster welding speeds will result in narrower and shallower welds. The shape of the weld will affect its mechanical properties and the overall appearance of the welded joint.
4. Efficiency: Welding speed can also affect the efficiency of the laser welding process. Faster welding speeds will result in shorter process times and higher throughput, while slower welding speeds will result in longer process times and lower throughput.
In summary, welding speed is an important parameter in laser welding that affects the quality, efficiency and appearance of the welded joint. The optimum welding speed for each specific application must be determined by considering the required weld depth of fusion, weld shape and the required weld quality.
Focus position
1. Depth of weld: The position of the focal point determines the position of the maximum energy density of the laser beam, which significantly affects the depth of weld. If the focal point is too high above the workpiece, the laser beam will scatter, resulting in low energy density, shallow weld depths and poor weld quality. Conversely, if the focal point is too low, the energy of the laser beam will be concentrated on the surface of the workpiece, resulting in a narrow and deep weld, but with the risk of excessive heat input and distortion.
2. Weld width: The position of the focal point also affects the width of the weld seam. If the focal point is too high above the workpiece, the laser beam will diverge, resulting in a wide and shallow weld seam. Conversely, if the focal point is too low, the laser beam will converge, resulting in a narrow and deep weld.
3. Heat input: The position of the focal point also affects the heat input to the workpiece. If the focal point is too high, the laser beam will scatter and the heat input will be low. If the focal point is too low, the laser beam will concentrate on the surface of the workpiece, resulting in high heat input and possible thermal damage to the workpiece.
4. Quality of the weld: The position of the focal point also affects the quality of the weld, including the presence of porosity, cracking and other defects. The optimum focal position must be determined for the particular material and thickness in order to avoid these problems.
The optimum focal position must be determined according to the material properties, thickness and the desired weld characteristics IC.
Protective gas
The shielding gas is essential in laser welding as it protects the melt pool from atmospheric contamination such as oxygen and nitrogen, which can lead to porosity, lack of fusion and other defects. The following are some of the ways in which the choice of shielding gas and its flow rate can affect laser welding.
Type of material: The choice of shielding gas depends on the material being welded. In general, argon is suitable for welding inactive metals such as aluminium and copper, while helium is used for welding active metals such as titanium and magnesium. A mixture of argon and helium can also be used to balance the properties of the two gases.
Weld quality: The flow rate and type of shielding gas affects the quality of the weld, including its appearance, strength and resistance to cracking and other defects. Low flow rates or inappropriate gas mixtures can lead to lack of fusion, porosity and other defects, which can reduce the mechanical properties of the welded joint.
Welding speed: The weld gas also affects the welding speed. A high flow rate of shielding gas can increase the welding speed by reducing the heat affected zone and cooling rate. However, the gas flow rate must be balanced to prevent the risk of porosity, lack of corrosion or excessive spatter.
Welding environment: The shielding gas also affects the welding environment. In particular, the type and flow rate of the gas affects fume generation and heat dissipation, the safety of the operator and the performance of the equipment. Therefore, proper ventilation and fume extraction must be implemented in the welding environment.
In summary, the choice of shielding gas and its flow rate are fundamental parameters in laser welding that affect the quality of the weld seam, the welding speed and the welding environment. The optimum shielding gas and flow rate must be determined for the specific material and welding conditions to ensure a high quality weld and safe working conditions.
More notes on the use of gases can be found in this article：The use of gases in laser welding
Joint clearance
The joint gap is the distance between two pieces of material that are joined together in laser welding. The joint gap can significantly affect the quality and efficiency of the welding process. The following are some of the ways in which the workpiece joint gap affects laser welding.
Depth of weld: The joint gap affects the ability of the laser beam to penetrate the workpiece. A narrow gap will result in the laser beam penetrating too deeply, leading to excessive heat input and possible burn-through, while a wide gap will result in penetration and a weak weld. A properly sized joint gap is necessary to achieve optimum weld depth and strength.
Weld quality: The joint gap can also affect the quality of the weld, for example by the presence of defects such as porosity, lack of fusi and cracking. Narrow gaps can lead to insufficient weld volume, while wide gaps can lead to excessive material melting, resulting in excessive porosity and a weak weld. The optimum joint gap should be determined by the material and thickness of the weld .
Weld appearance: The joint gap can also affect the appearance of the weld. Wide gaps result in larger welds, which may require additional post-weld treatment to achieve the desired appearance. In contrast, a narrow gap will produce a narrow, deep weld, which may not be aesthetically pleasing.
Welding speed: The joint gap can also affect the welding speed. A narrower gap may require a slower welding speed to achieve proper penetration, while a wider gap may require a faster welding speed. A balance must be established between gap size and welding speed to ensure optimum weld quality and productivity.
In summary, the workpiece joint gap is a key parameter in laser welding and can significantly affect weld depth, quality, appearance and welding speed. The optimum joint gap must be determined for the specific material and thickness to achieve a high quality weld and maximum efficiency.
Material nature
The properties of the material being welded can have a significant impact on the laser welding process. The following are some of the ways in which material properties affect laser welding.
Absorption: The ability of the material to absorb the energy of the laser beam affects the welding process. Materials with a high absorption coefficient, such as metals, absorb more energy and are therefore easier to weld than materials with a low absorption coefficient, such as plastics.
Thermal conductivity: The thermal conductivity of a material affects the heat input and distribution during the welding process . Materials with high thermal conductivity, such as copper and aluminium, dissipate heat more efficiently and require a higher power density for optimum penetration.
Melting point: The melting point of the material affects the speed and quality of the weld. Materials with high melting points require higher laser power densities and longer exposure times, which can increase the risk of heat affected zones and distortion.
Thermal expansion: The thermal expansion of a material affects the residual stress and distortion of the weld. Materials with a high coefficient of thermal expansion, such as plastics, expand and contract more significantly during the welding process, requiring careful control of heat input and cooling rates.
Chemical composition: The chemical composition of the material affects the weldability and quality of the welded joint. Materials with high alloying elements, such as stainless steel, require precise control of welding parameters to avoid microstructural angles, cracking and other defects.
In summary, material properties can significantly influence the laser welding process, including heat input, depth of melt, quality and residual stresses. Optimal welding parameters such as laser power density, speed and shielding gas must be determined for the specific material being welded to achieve a high quality weld and avoid defects.
