What Are The Factors That Affect The Thickness of Laser Welding

What are the factors that affect the thickness of laser welding?

Laser welding is a common metal joining technique widely used in manufacturing and construction. Among them, the welding thickness is a key parameter, and the welding thickness refers to the thickness of the welded joint, which directly affects the strength and stability of the welded joint. Understanding the factors that affect weld thickness is critical to ensuring weld shape and quality. This article will discuss the main factors affecting the thickness of laser welding, including welding method, metal material, welding process, and design requirements.

Influence of Laser Welding Method on Welding Thickness

Different laser welding methods are suitable for different application scenarios and have different requirements for welding thickness. These methods will have differences in power, heating speed, focusing mode, and welding energy during the welding process, so they have different limitations for different welding thicknesses.

Laser power and beam quality

Laser power and beam quality are two important parameters, which have a certain influence on the thickness of laser welding.

Laser power: Laser power refers to the energy transmitted by the laser beam. For the same material and welding conditions, higher laser power can generally provide greater weld penetration depth, which is suitable for welding thicker materials. However, excessive laser power can cause excessive melting of the weld and enlargement of the heat-affected zone, possibly causing deformation and quality problems. Therefore, it is necessary to balance the requirements of welding quality and speed when selecting laser power.
Beam quality: Beam quality has a significant impact on energy distribution and focusing performance during welding. Better beam quality can provide smaller focal spot size and higher beam focusing ability, making welding energy more concentrated, thus improving welding precision and control performance.

Beam focusing method and focus position

The beam focusing method and focus position also have a certain influence on the welding thickness during the laser welding process.

Beam focusing method: Common beam focusing methods include flat focus focusing, convex lens focusing concave lens focusing, etc. Different focusing methods have different adaptability to welding thickness.
Focus position: When the focus position is above the surface of the weldment, a larger welding depth and a larger heat-affected zone can be achieved. This focal position is suitable for welding thicker materials and can increase the penetration depth of the weld. When the focus position is below the surface of the weldment, a smaller weld penetration depth and a smaller heat-affected zone can be achieved. This focal position is suitable for welding thinner materials, which can reduce distortion and heat damage.

Scan speed and laser beam diameter

Scanning speed: The speed at which the laser beam moves in the welding area during laser welding is called the scanning speed. Lower scanning speed can provide longer welding time so that the heat can be transferred to the welding area more fully, suitable for cutting thicker materials. The higher scanning speed means that the laser beam stays in the welding area for a shorter time, which is more suitable for cutting thinner materials.
Laser beam diameter: A smaller laser beam diameter can provide higher energy density and make the heat in the welding area more concentrated. This helps achieve a lower weld penetration depth and is suitable for welding thinner materials. Larger laser beam diameters are beneficial for welding thicker materials or welding tasks that require filling larger areas.

Influence of material properties on weld thickness

The influence of different materials on the thickness of laser welding is multifaceted because different materials have different thermal conductivity, melting points, and melting behavior. Here are some key factors to consider:

Absorption coefficient

The absorption coefficient of a material determines how efficiently it absorbs laser energy. Materials with high absorption coefficients for the laser wavelengths used in the welding process tend to absorb more energy and heat up more quickly, resulting in deeper penetration and thicker welds. For example, metals such as steel have high absorption coefficients for certain laser wavelengths, allowing deeper penetration and thicker welds than materials with lower absorption coefficients such as aluminum.

Thermal conductivity

The thermal conductivity of materials affects the heat distribution during laser welding. Materials with low thermal conductivity, such as stainless steel, tend to retain more heat, resulting in deeper penetration and thicker welds. Materials with high thermal conductivity, such as copper or aluminum, tend to conduct heat away from the weld area more efficiently, resulting in shallower weld penetration and lower weld thickness. Therefore, they require higher laser power or longer exposure times to achieve deep penetration and thicker welds.

Melting point

The melting point of a material affects the temperature required for melting and welding. When laser welding, the material needs to reach its melting point to form a weld pool. Materials with lower melting points require less laser energy to reach melting temperature, resulting in increased penetration and weld thickness. Conversely, materials with higher melting points may require higher laser energy, resulting in shallower weld penetration and lower weld thickness.

Reflective

The reflectivity of the material affects the amount of laser energy absorbed or reflected. High-reflection materials (such as aluminum or copper) reflect most laser energy, resulting in reduced absorption and limited welding depth. In contrast, materials (such as carbon steel) with lower reflectivity (such as carbon steel) will absorb more laser energy, thereby achieving deeper depth and thicker welds.

Thickness

The thickness of the welding material also affects the thickness of the weld. Laser welding is usually more suitable for thinner materials because laser energy can be more accurate and effective. Thicker materials may require multiple welding tracks or higher laser power to achieve complete melting, which may affect the final welding thickness.

Thermal expansion coefficient

The thermal expansion coefficient is the degree of the material’s expansion or contraction with temperature changes. When the laser energy is applied during welding, the material will experience rapid heating and subsequent cooling. Materials with high thermal expansion coefficients (eg, certain plastics) may occur significantly during welding, resulting in changes in the thickness of the weld.

Metallurgical performance

The metallurgical performance of materials, such as their ingredients, grain structure, and alloy elements, can also affect the welding thickness. For example, certain alloy elements may change the absorption coefficient or thermal conductivity of the material, thereby affecting the thermal input and welding depth.

Vaporization and boiling behavior

Some materials are more likely to vaporize or boil when they are exposed to high temperatures. During the laser welding process, this vaporization or boiling can cause the melting material to be sprayed and reduce the weld melting depth and the reduction of the welding thickness. Shaping behavior is affected by factors such as material steam pressure, boiling point, and vaporization potential heat.

Following and solidification behavior

Different materials have different melting and solidification characteristics, affecting the formation and solidification of the melting pool. Materials that are narrow or consolidated in a fused range or obvious coagulation and contraction will affect the achievable welding thickness.

It is worth noting that these factors interact with each other and interact with laser welding process parameters (such as laser power, beam diameter, and welding speed). Therefore, optimizing the laser welding process for specific materials needs to be considered, and balanced these materials to achieve the required welding thickness and quality. In addition, the specific laser welding process (such as small holes welding or conduction welding) can also affect the relationship between material characteristics and weld thickness.

Influence of Laser Welding Process Control on Weld Thickness

The parameter setting and operation method in the laser welding process will also affect the welding thickness. For example, the selection of parameters such as welding current, welding speed, and welding time will directly affect the size and shape of the welded joint. In addition, processes such as preheating and post-heat treatment during the welding process are also important factors to control the welding thickness.

Preheat and post-heat treatment

Preheating and post-heat treatment are two commonly used welding process control methods. The following is a general situation of the effect of preheating and post-heat treatment on weld thickness:

Preheating: The purpose of preheating is to improve the thermal stress and cooling rate during the welding process. Through preheating, the temperature of the material can be increased, the temperature gradient during the welding process can be reduced, and the thermal stress can be reduced, thereby reducing the risk of deformation and cracks. Preheating of thinner materials should be evaluated and adjusted on a case-by-case basis.
Post-heat treatment: Post-heat treatment is to heat or cool the weld area after welding. The purpose of post-heat treatment is to improve the structure and performance of the weld, reduce residual stress, and improve welding quality.

Choice of weld shape and filler

Weld shape: Weld shape includes linear weld, V-shaped weld, U-shaped weld, J-shaped weld, etc. Different weld shapes have different effects on welding thickness. For example, straight welds are suitable for welding thinner materials, which can provide better welding strength and sealing. The V-shaped weld has a larger welding depth and is suitable for welding thicker materials, etc.
Filler: A filler is a material added to the weld during the welding process to fill and strengthen the welded area. For thinner materials, filler options may be more limited. For thicker materials, fillers can be used to fill welds of greater width and depth.

Influence of Design and Application Requirements on Weld Thickness

Design requirements refer to the requirements of products or structures for laser welding, including strength, sealing, appearance, etc. The influence of design requirements on the thickness of laser welding is as follows:

Higher strength requirements

For products or structures that require higher strength, it may be necessary to increase the strength of the welded connection by increasing the weld thickness.

Higher tightness requirements

If the product or structure needs to have high sealing performance, it may also be necessary to increase the sealing performance of the welding area by increasing the welding thickness.

Appearance requirements

If the product or structure has high requirements on appearance, it is necessary to pay attention to the unevenness and surface quality of the welding area. Larger weld depths and bead sizes can hurt appearance, so this needs to be balanced in the design.

Application Requirements

Application requirements refer to the specific application scenarios and requirements of laser welding. The influence of the working environment on the thickness of laser welding is mainly reflected in the temperature, vibration, and ambient atmosphere. For example, a high-temperature environment may cause the heat-affected zone of the welding area to expand, and corresponding measures need to be taken to control the welding thickness.

Summarize

In short, many factors affect the thickness of laser welding. In addition to welding methods, material properties, welding processes, and design requirements, it also involves many aspects. When performing welding operations, these factors need to be considered comprehensively, and the appropriate welding thickness should be selected according to the specific situation.
Only when the welding thickness meets the requirements can the quality and reliability of the welded joint be guaranteed, to meet the needs of engineering and products. If you are considering laser welding, please contact AccTek Laser and we will suggest the best solution for your needs.

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