Zinc is a popular material part manufacturers use. From consumer hardware and decorative items to electrical enclosures and casings, zinc serves various industries. When joining zinc components, it is expected to consider laser welding because of its high precision and excellent speed.
Zinc poses some challenges during laser welding because of its low melting point, high heat conductivity, and high reflectivity. However, with correct welding parameters and proper workpiece preparation, the laser welding zinc process can be straightforward. This article explains what laser welding zinc is, the causes and solutions to laser welding zinc defects, and the industrial applications of zinc laser welded components.
What is Laser Welding Zinc
Laser welding zinc is an advanced technology where pieces of zinc or zinc-coated material are joined to make a single sturdy piece. Laser welding is the go-to method used to assemble zinc parts because of the unique properties of this metal. Zinc has a low boiling point, which is an issue when heat is applied. Rather than melt fully, there is a risk for evaporation, which can lead to defects.
Additionally, there is a tendency for oxide formation if heated zinc is exposed to air. The production of zinc oxide can contaminate the weld pool and weaken the joint. Laser welding applies localised heat and reduces damaging the surrounding material. It comes with a high speed and accuracy level.
The process of laser welding zinc is similar to other metals. It begins with cleaning all forms of contaminants that can cause unwanted reactions. After that, generate the laser beam using fibre or Nd: YAG lasers. Amplify the laser beam and deliver it through an optics system. The zinc workpiece absorbs energy from the laser beam and melts at the joint. As cooling and solidification occur, the parts fuse and a strong weld is formed. The final step involves inspecting the weld quality and making adjustments if needed.
Causes and Solutions to Laser Welding Zinc Defects
Laser welding zinc tends to produce defective welds if the process is poorly controlled. Let’s look at individual laser welding zinc defects, their causes and ways to prevent them
Porosity
Porosity is a common laser welding zinc defect. It occurs when tiny holes are formed within the joint after solidification. Porosity happens if the weld pool becomes contaminated. These pores usually appear scattered and occur when trapped air and moisture escape. They affect the structural integrity of the joint and can cause part failure over time.
Causes
- Zinc rapidly evaporates because of its low melting point, which leaves voids behind.
- Insufficient shielding gas coverage will not properly protect the weld pool.
- Using too high heat input.
Solutions
- Optimize heat input to prevent vaporisation.
- Preheat the workpiece to reduce thermal shock.
- Use the correct quantity of pure inert gas to shield the weld pool.
- Properly clean the surface of the workpiece before any welding process.
Blowholes
Blowholes are similar to porosity. However, they are bigger and can occur within the joint or at the surface. Blowholes can appear in clusters and are detected through a thorough inspection. These undesired holes are aesthetically unappealing and should be corrected whenever they occur. Additionally, they compromise the joint quality and weaken it.
Causes
- Too high laser power and fast welding speed can cause the zinc workpiece to boil.
- Presence of moisture and contamination of the base metals’ surface.
- Using the wrong type and quantity of shielding gas.
Solutions
- Adjust the laser welding parameters, including speed and power.
- Properly prepare the workpiece.
- Prioritize the use of shielding gases.
Zinc Oxide Inclusions
This occurs when zinc oxide slags become embedded in the joint after solidification. These inclusions can be easily seen on the weld metal because they are usually white and dense. Zinc oxide inclusions affect the part’s performance, especially in demanding applications. They reduce fatigue strength and increase the tendency of cracks occurring
Causes
- Inadequate access to the joint.
- The layers of zinc oxide are not properly removed before welding.
- High travel speed increases the likelihood of zinc oxide slags solidifying permanently.
Solutions
- Properly position the workpiece and clean the surface to prevent oxidation.
- Use the right travel speed.
Undercuts
Undercuts are common laser welding zinc defects that can occur. They appear as grooves or depressions at the areas where the joint meets with the base metals. This weld discontinuity makes the final parts prone to failure. It induces stress and affects the weld appearance.
Causes
- Improper alignment of the laser beam.
- Using excessive heat input and laser power which burns the edges of the base metals.
- Using worn-out machines and tools.
Solutions
- Properly align the laser beam with the joint.
- Reduce the laser power and manage the heat input.
- Maintain the laser welding system and its accessories adequately.
Cracks
Cracks are detrimental zinc laser welding defects. They appear as long and narrow fractures within the joint. There are two types of cracks in laser welding: hot and cold cracks. Hot cracks occur during welding, while the cold type happens when the parts are already in use. They usually start as thin lines and increase in length and size with time.
Causes
- Too high welding speed and heat input, which builds up residual stress in the joint.
- Rapid cooling of the weld pool.
- Contamination of the base metals.
Solutions
- Preheating the workpiece and cooling the joint slowly.
- Adjust the welding parameters as needed.
- Proper preparation of the workpiece.
Incomplete Fusion
You can also experience incomplete fusion and penetration with zinc laser welding. It occurs when the base metal does not fully fuse with the weld joint. Incomplete fusion can happen at any point, and the effects extend beyond aesthetics. This welding defect makes the joint weak and unreliable.
Causes
- Insufficient laser power.
- Using a travel speed that is too fast and prevents sufficient heat penetration.
- Improper alignment of the laser beam.
- Zinc’s high reflectivity can reduce laser beam absorption.
Solutions
- Proper joint preparation and laser beam alignment.
- Adjust the welding parameters.
- Using shorter wavelengths and applying a temporary non-reflective coating.
Spatter
Spatter occurs when molten zinc metal is ejected from the weld pool. The liquified metal lands on the surface of the base material and forms globules. Spatters can appear singly or as clusters. They result in uneven and rough surface finish. The effects of spatters sometimes extend beyond cosmetic problems. It can re-enter the joint and affect the structural integrity.
Causes
- The low boiling point of zinc metal allows it to evaporate quickly from the weld pool.
- Presence of impurities in the joint.
- Using worn-out laser beam delivery systems.
Solutions
- Optimizing laser power and travel speed.
- Thoroughly clean the base metals.
- Weld using the right angle and shielding gas coverage.
- Properly maintain the welding equipment.
Applications of Laser Welding Zinc
Laser welding is the method of choice when joining zinc metal pieces. This technique comes with high precision and gives you total control. Additionally, there is a reduced risk of thermal damage. Let’s look at typical applications of laser welding zinc in depth.
Automotive Industry
Laser welding zinc is becoming the mainstay technology when fabricating automotive parts. This industry makes extensive use of zinc metals and zinc-coated structures. Laser welding zinc produces strong and durable joints in exhaust systems, body panels, and chassis.
Consumer Goods
Another application of laser welding zinc is the manufacturing of consumer goods such as household appliances, decorative items, lighting fixtures, and tool housings. Zinc and zinc-coated components are visually appealing. They can be quickly joined without the need for post-processing.
Aerospace Industry
The aerospace industry uses laser welding zinc extensively. This technique makes it possible to assemble components that can withstand corrosion in harsh environments. Examples of laser-welded zinc aerospace parts are electrical connectors, enclosures, and housings.
Medical Devices
The use of zinc laser welding in the medical industry is nothing new. Zinc is corrosion-resistant and biocompatible. Hence, it will not break down when in contact with bodily fluids. Medical applications of laser welding zinc are surgical instruments, device casings, and enclosures.
Conclusion
While zinc has many desirable properties, it can be challenging to weld this metal. Zinc has a low melting point and reflects a good amount of laser beam. Hence, it takes careful consideration to cut through. When laser welding zinc, there is a probability of defects occurring. These defects, such as porosity, undercuts, and cracks, are caused when the laser power exceeds what is needed, or contaminants are present on the workpiece. To prevent this, you must properly clean the base metals and optimize the laser beam welding parameters.
