Introduction
Laser welding is a highly effective and strong welding method used in various industries, including automotive, aerospace, electronics, and medical devices. Its strength depends on several factors, including the materials being welded, the welding parameters and environment, and the quality of the weld. First we reference a study, then take a look at the factors that contribute to a stronger weld.
Case Study
To demonstrate the superior strength of a laser weld, we’ve referenced a study by the National Centre for Biotechnology Information (NCBI). The investigation studied the effect of laser welding process by evaluating the metallurgical and mechanical properties of SA516 grade 70 high strength low alloy steel joints without any weld preheat treatment. The following conclusions are derived from the experiment’s results¹ :
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Produced good quality weldment without any defect such as distortion, cold cracking and hydrogen induced cracking.
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The weld fusion zone contains martensitic structure due to very high cooling rates associated with laser welding.
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The microhardness of the fusion zone was found to be approximately 2.5 times the base metal in the welded region, whereas, a narrow soft zone of HAZ was observed near the weld interface.
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The joint fabricated by laser welding process exhibited higher strength values, and the enhancement in strength value is approximately 13% even without any weld preheat treatment.
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The tensile failure occurred in the base metal region during the tensile tests for all the trials. The ultimate tensile strength and percent elongation obtained for Nd:YAG CW laser welding are 550 MPa and 9% respectively. The SEM fractography of the tensile samples showed ductile mode of failure.
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The weld impact strength was found to be less as compared to base metal (5.5 J) and it is inversely proportional to the hardness.
Variables
Laser welding, when completed by a skilled tradesperson in a specialist environment, results in stronger welds than TIG welding. The following is a list of variables that result in laser welds that are extremely strong and durable.
- Materials: The strength of a laser weld largely depends on the materials being joined. Laser welding is suitable for a wide range of materials, including metals like steel, aluminium, titanium, and even some non-metals like plastics. When welding similar materials together, the joint strength can be exceptionally high, as the materials tend to bond well. However, when dissimilar materials are welded, the joint strength may be reduced due to potential differences in material properties.
- Welding Parameters: The laser welding process allows for precise control over welding parameters, such as laser power, welding speed, focal position, and pulse duration. Optimising these parameters ensures a strong weld. If the parameters are not well controlled, it can lead to defects like porous surface, incomplete fusion, or excessive heat affected zones, which can compromise the strength of the weld.
- Weld Quality: The quality of the laser weld is a critical factor in determining its strength. A well executed laser weld with proper penetration, minimal defects, and good fusion will result in a strong joint. Weld defects, such as pores, cracks, or lack of fusion, can significantly weaken the weld and compromise its strength. Operator expertise is key in achieving the highest strength welds.
- Microstructure: The laser welding process can produce unique microstructures in the weld zone, which can influence its strength. The rapid cooling rates during laser welding can lead to finer grain structures, potentially enhancing the joint’s strength and hardness. However, the microstructure can also be influenced by the welding parameters and may require further heat treatment to optimise strength in some projects.
Summary
Overall, laser welding¹ is known for producing high-quality, strong welds, especially in precision applications and industries where join integrity is crucial. Its strength and reliability make it a preferred welding method for critical components in various high-tech sectors where quality control is critical. Nonetheless, like any welding process, proper welding procedure and quality control are essential to achieving the desired strength in laser welds.
Please contact our specialist team today for advice in your laser weld project.