+86-18024499925
LASER NEWS
You are here: Home » News & Events » Industry News » Modern Laser Welding Technology Focus — Laser Spot Welding

Modern Laser Welding Technology Focus — Laser Spot Welding

Views: 0     Author: Site Editor     Publish Time: 2024-07-02      Origin: Site

Inquire

facebook sharing button
twitter sharing button
line sharing button
wechat sharing button
linkedin sharing button
pinterest sharing button
whatsapp sharing button
sharethis sharing button

Modern Laser Welding Technology Focus — Laser Spot Welding

Laser spot welding is a significant branch within modern laser welding technology. It utilizes a high-energy-density laser beam to locally heat the surface of workpieces in an extremely short time, achieving the melting and bonding of materials. Laser spot welding is particularly advantageous for applications requiring high precision, high speed, and minimal heat-affected zones, especially for thin sheets and delicate components.

1. Principles and Operation

Laser spot welding harnesses the high energy density of a laser beam to focus on a very small area (typically in the millimeter or sub-millimeter range). This allows the welding process to affect only the focal point, with minimal thermal impact on surrounding areas. This characteristic makes laser spot welding suitable for welding materials sensitive to heat or prone to deformation.

2. Application Areas

Laser spot welding finds wide applications in the following fields:

Automotive Industry: Used for welding automotive components such as doors and body panels due to its ability to efficiently weld different types of metals like steel and aluminum.

Electronics and Electrical Industries: Suitable for welding tiny electronic components such as circuit boards and wire connections, providing precise and non-destructive welding.

Aerospace: Used for welding aerospace components such as turbine blades and structural parts, ensuring welding strength and material integrity are maintained.

Medical Devices: Applicable for welding fine components in medical devices, including laser cutting and welding of miniature wires and tubes.

3. Technological Advantages

Compared to traditional welding methods, laser spot welding offers several significant technological advantages:

High Precision: Capable of achieving welding at the micron level, ensuring precise and stable welding joints.

High Speed: Fast welding speeds save production time and increase efficiency.

Non-contact: Laser welding is a non-contact welding method, minimizing mechanical damage to the workpiece.

Small Heat-Affected Zone: Due to minimal thermal diffusion, it reduces heat deformation and residual stress.

4. Technological Challenges

Despite its many advantages, laser spot welding also faces several challenges, such as:

Weld Depth Control: Precise control of weld depth and seam morphology for different material thicknesses.

Material Selection: While laser spot welding is applicable to most metal materials, optimizing processes for specific materials like copper and aluminum may require additional adjustments.

Equipment Costs: High-power lasers and precise welding equipment can be costly, which may pose challenges for smaller enterprises.

5. Future Trends

With continuous advancements in laser technology, laser spot welding is expected to expand further in precision, efficiency, and application areas. Future trends include:

Multi-wavelength Laser Welding: Combining lasers of different wavelengths to expand the range of applicable materials and welding depths.

Intelligent Welding Systems: Utilizing advanced sensors and control technologies to automate and optimize the welding process.

Customized Welding Solutions: Providing tailored laser spot welding solutions based on industry and application needs to optimize welding performance and cost-effectiveness.

1.Characteristics and Definition of Laser Spot Welding

Definition:

Laser spot welding refers to the process where a single laser pulse (t > 1 ms) or a series of laser pulses are used to melt and join workpieces at the same location.

图片

Laser Spot Welding and Its Characteristics

Laser spot welding is fundamentally similar to other laser welding processes, with the key distinction being that during spot welding, there is no relative movement between the laser beam and the workpiece. Laser spot welding can be divided into two types: conduction mode and keyhole mode.

In conduction mode spot welding, the laser only melts the metal without vaporizing it, making it suitable for welding metals with thicknesses less than 0.5 mm, such as electronic components welded with Nd

lasers. In keyhole mode laser spot welding, the laser can directly penetrate the material through a keyhole, thereby increasing the utilization of laser energy and allowing for greater depth of penetration. Traditional resistance spot welding relies on resistive heating generated by electric current to melt the workpiece, whereas laser spot welding uses laser radiation as the heat source, resulting in significant differences in the shape of the weld joint.

Adjustable parameters for laser spot welding typically include laser power, spot welding time, and focal offset. When pulse welding, parameters also include pulse waveform, frequency, and duty cycle. Laser power primarily affects the depth of penetration at the weld point, while spot welding time significantly influences the lateral dimensions of the weld spot. Generally, longer laser interaction times result in larger dimensions of the upper and lower surfaces of the weld and the fusion zone. Changes in focal offset mainly affect the spot size and energy density on the workpiece surface, thereby having a significant impact on the overall shape of the weld spot.

Characteristics:

Due to the use of laser as the heat source, laser spot welding offers fast welding speed, high precision, low heat input, and minimal workpiece deformation.

Laser spot welding provides greater freedom in welding position, enabling full-position and single-side spot welding, thereby enhancing product design flexibility.

Laser spot welding has low requirements for lap joint dimensions, lap overlap, and distance between weld spots, with minimal concern for current distribution effects.

Laser spot welding exhibits advantages over traditional methods when welding dissimilar thickness plates, dissimilar materials, and special materials (e.g., aluminum alloys, galvanized sheets).

It requires minimal auxiliary equipment, adapts quickly to product variations, and meets market demands efficiently.

Defect Analysis in Laser Spot Welding

Cracks, pores, and sagging are the most common defects encountered in laser spot welding, each of which is analyzed below:

Cracks

Cracks can be categorized as surface cracks and longitudinal cracks. The rapid heating and cooling rates during the laser spot welding process create significant temperature gradients between the heated zone and the surrounding metal, making crack formation more likely. The propensity for crack formation varies with materials; for instance, aluminum alloys are more prone to cracking during laser spot welding. Using optimized pulse waveforms to control metal solidification and reduce internal stresses is an effective method to mitigate crack formation.

Pores

Pores in laser spot welds can be classified as small pores and large pores. Small pores are primarily caused by the decreased solubility of hydrogen in liquid metal during metal solidification, rapid evaporation of metal in the keyhole, and turbulence in the molten pool. Large pores typically result from excessively fast cooling rates during the laser spot welding process, preventing adequate metal flowback around the keyhole. Generally, long-pulse spot welding methods tend to produce small pores, while short pulses tend to produce large pores.

The two most common locations for pores in laser spot welding are near the center of the fusion zone and at the root of the weld seam. X-ray imaging of molten pools shows that pores near the fusion zone are mainly due to necking when the keyhole collapses. Pores at the root of the weld seam result from the sudden disappearance of the laser after keyhole collapse.

图片

Laser Spot Welding and Its Applications

Sagging

Sagging is a prominent phenomenon in laser spot welding. The central sagging on the surface of the weld and the surrounding metal buildup are caused by the recoil force generated during metal vaporization, pushing liquid metal towards the weld surface. During the cooling process, the rapidly solidifying surface metal cannot completely flow back, resulting in buildup. Additionally, material loss due to rapid evaporation and spatter also contributes to central sagging. Pulse duration significantly affects the sagging of the weld surface and the formation of pores. Optimizing pulse waveform and duration can achieve satisfactory welds.

Influence of Focal Offset on Welding

Changes in focal offset directly alter the diameter of the laser spot and the energy density. Increasing the focal offset in both negative and positive directions results in larger spot diameters and reduced energy density. In laser spot welding, the spot diameter corresponds to the initial keyhole size formed by laser incidence on the workpiece, while the energy density determines the rate of weld pool expansion. A smaller absolute value of focal offset results in a smaller laser spot diameter, higher laser power density, faster weld pool expansion, and smaller initial keyhole diameter. Conversely, a larger focal offset leads to a larger initial keyhole diameter but slower weld pool expansion, resulting in variable weld sizes. Therefore, changes in focal offset affect both spot diameter and surface power density, determining the size of the weld.

Applications of Laser Spot Welding Technology

Due to its fast speed, deep penetration, minimal deformation, and ability to weld under ambient or specialized conditions with simple welding equipment, laser spot welding is widely used. The emergence of high-frequency pulse lasers (over 40 pulses per second) has facilitated extensive application in the batch production of micro and small components. Laser spot welding offers significant advantages over traditional methods, such as resistance spot welding, particularly in welding small electronic components requiring minimal heat-affected zones, connections between glass and metal, joints in thermosensitive semiconductor circuits, and connections between different metals in wires. Laser spot welding ensures contaminant-free welds and high welding quality.

Figure 6-60 illustrates an application example of laser spot welding in automotive lamp production using a 500W solid-state pulse laser to generate four similar weld spots at a high pulse frequency.

In precision spot welding of microstructures, pulse Nd

lasers offer both technical and economic advantages. In most industrial spot welding applications, pulsed solid-state lasers with an average power of 50W and pulse power >2kW are used, with laser energy delivered via optical fiber or combination focusing lenses.

Laser spot welding is applicable to a wide range of materials. For instance, when welding lithium-ion batteries, Nd

laser spot welding technology is more efficient than TIG and resistance spot welding methods, especially when using optical fibers for laser transmission, enabling quick and flexible movement between workstations.

In summary, laser spot welding exhibits the following characteristics:

With increasing laser power, the diameter of the weld spot surface fluctuates. The diameter of the fusion zone and the lower surface diameter grow slowly. There is no significant change in the cross-sectional shape of the weld spot. With increasing duration, the weld spot size increases rapidly, and the change rate of the diameter of the fusion zone is greater than that of the upper and lower surface diameters. Changes in focal offset greatly affect the size of the weld spot. It directly changes the diameter of the spot and the power density of the laser, and the comprehensive effect of these two determines the size of the weld spot.

Under full melting conditions, there is obvious sagging on the surface of the laser spot weld. With the increase of laser power and duration, the depth of sagging on the weld surface increases. In the case of long duration or large gap size, there will be internal concavity on the lower surface.

With the increase of gap size, the overall deformation of the weld spot is obvious, with significant central sagging and internal concavity, and shrinkage of the fusion zone, leading to a rapid decrease in strength. Currently, in the field of welding resistance, batteries, and electronics, the process of welding two points simultaneously is commonly used, usually using two laser light source designs.

LASER OPTICS

Laser Accessories&Consumables

QUICK LINKS

Copyrights © 2020 LASERHOME.COM   All rights reserved.  Sitemap