Laser welding joins stainless steel pieces with a powerful beam. Differing from traditional methods, this advanced laser technology reaches deep and forms strong bonds. It’s beneficial because the joints it creates are reliable and sturdy.
The welded region has a refined structure due to the low diameter of the laser beam and the high feed rate, which ensures a strong binding at all points. Laser welding has grown in popularity recently as a versatile and precise welding technology for a wide range of metals, including stainless steel and aluminum alloy. There are great opportunities and scopes for new creations in the manufacturing sector with laser welding aluminum to stainless steel parts. Let’s learn about the process in detail for better understanding and outcomes.
Welding of Dissimilar Metals
The dignity of a metal defines its resistance to corrosion, and different metals have varied qualities. A metal’s corrosion resistance is correlated with how readily it loses electrons. Noble metals are more resistant to corrosion because they are better at holding onto their electrons than base metals.
Under the correct circumstances, two dissimilar metals will naturally come into contact, and the nobler metal will absorb electrons from the less noble metal. For instance, aluminum is not as noble as stainless steel. If an electrolyte (like water) is available, it will gradually wear the aluminum down by stealing electrons from it anytime it can. The likelihood of corrosion increasing with metal purity is directly proportional to metal purity. Welders can better determine which metals are likely to collaborate by knowing where each metal falls on the noble scale.
The Challenges of Welding Aluminum
Welding aluminum is more complex than other metals due to a few specific characteristics. It can only be welded using these techniques due to its low melting point (1,221°F/660.3°C) and relatively high thermal conductivity (around 209 W/m K). Let’s understand the challenges:
Aluminum Oxidation
Aluminum oxidation results from the metal reacting and combining with airborne or moisture-borne oxygen. It’s a normal process brought on by the metal’s deterioration over time.
It’s critical to distinguish between corrosion and rust in this situation. One kind of corrosion that mainly affects iron and steel is called rust, which happens when these materials come into contact with moisture. Metals corroding is the result of a chemical reaction wearing them down. This is the result of aluminum oxidizing.
Aluminum oxidizes to produce a white, chalky, powdery layer on the metal’s surface. A large portion of aluminum’s corrosion resistance can be attributed to this first oxidation. Which also serves to shield the metal from further corrosion.
Hydrocarbon Contamination
Welding issues may arise from hydrocarbon contamination of aluminum. It happens during material preparation and storage. Before welding, aluminum pieces are often shaped, sheared, sawed, and machined. To prevent poor welds, all lubricants used in any of these pre-weld activities must be removed entirely before welding.
Caution demands that aluminum components that are to be welded must be sawed. Also, they must be machined dry if at all feasible, or else the parts need to be thoroughly cleaned. Pre-weld processing should be done in a way that uses little to no lubrication.
Laser Welding Aluminum to Stainless Steel – How It Works
Recent years have seen a rise in the use of laser welding as flexible and accurate welding. This technique is suitable for various metals, including aluminum alloy and stainless steel. However, when joining these materials with laser welding, there are both benefits and drawbacks.
Laser welding offers several benefits because of the laser’s accuracy and control. It includes the production of excellent welds with little distortion and warping. Additionally, laser welding can produce small heat-affected zones. It also lowers the possibility of base material deterioration. Moreover, automation of laser welding can increase productivity and lower personnel expenses.
However, there are restrictions when employing laser welding for these materials. One drawback is that, in comparison to conventional welding techniques, the equipment can have a hefty upfront investment cost. Additionally, laser welding may require specific knowledge and training to operate the equipment and improve the welding process. Another restriction is the thickness of the materials that can be combined; it holds a significant impact in laser welding.
Lasers for Aluminum Welding
Three categories of lasers are suitable for welding aluminum:
- CO2 laser source
- YAG lasers
- Fiber Laser
High-quality aluminum welds can be produced using any of these methods. The choice of technique depends more on operational expenses than weld quality. Here is an explanation of aluminum welding.
CO2 Laser Source
The CO2 laser source is a popular tool for joining aluminum. However, it is not appropriate for pure aluminum. Aluminum has a high factor of thermal expansion and thermal conductivity, which makes the CO2 laser source very prone to deformation when welding. To assure the feature of the weld seam, the operator must follow suitable preheating and cooling procedures when using a CO2 laser source to weld pure aluminum.
YAG lasers
With an output wavelength of roughly 1.06 μm, the YAG (Yttrium Aluminium Garnet) laser source uses a YAG crystal as the laser medium. When welding aluminum, it results in a smaller spot size and a higher beam quality, allowing for more control and precision.
Aluminum is better suited for welding with a YAG laser source. Use an extra welding material or pulsed laser welding, which can produce superior welding quality if you wish to weld pure aluminum or aluminum alloys.
Fiber Laser
A novel technique for welding metal is the fiber laser welder. With an output wavelength of 1064 nm, it is perfect for producing welds of superior quality. For welding aluminum alloys, pure aluminum, and aluminum materials, this is the best laser source. Yes, the fiber laser source is pricey, but the final result is worth the money.
Laser Welding Modes of Operation
Either a continuous beam, a sequence of pulses, or a laser stir weld configuration can be used to provide laser beam energy to the workpiece. The application, the characteristics of the materials, etc., all influence the choice of which method to use.
Pulsed Laser Welding
A sequence of brief pulses with a specific width and frequency is produced by pulsed lasers. A pulsed laser’s ability to generate a higher peak power than usual is attributed to the energy being stored in capacitors before release. Very high peak powers can be achieved with pulsed lasers: For a few milliseconds, a 25 W pulsed Nd: YAG laser may generate peak energies of up to 5 kW. This indicates that it can create a spot weld that would need a 5 kW CW laser.
A sequence of overlapping spot welds produced by pulsed lasers forms a seam weld. These spot welds overlap 80–90% when used for hermetic sealing applications. Simple structural welds that don’t need sealing can have an overlap of about 70%.
Continuous Wave Laser Welding
Lasers with a continuous wave (CW) emit a beam that is steady and unbroken. These are fiber-style lasers, which produce laser light by exciting a gain medium using diodes that have been turned on. CW lasers work particularly well for welding crack-sensitive materials, such as high-carbon stainless steel, and for deep penetration welds (beyond 060″).
Power outputs for CW lasers range from 200 Watts to more than 100,000 Watts. For most metals, CW laser welding needs 200 watts or more to couple them together. Combining this broad power range with high energy densities makes it easier to fuse metals with various thermal and reflective properties.
Ferrous metals, including copper and aluminum, couple at much higher power (600–800 w). Meanwhile, materials like stainless steel couple at a lesser power (about 200 w). CW lasers operate at high feed rates to avoid overheating the component. The usual feed rates for CW are approximately 100 inches per minute. Power and feed speed must be regulated to get a weld with the desired penetration.
Laser Stir Welding
It’s difficult to laser weld aluminum without it splitting. Usually, operators use an easier-to-weld alloy for the filler wire or shim when welding strong welds on alloys that crack. This facilitates smoother welding and helps prevent cracks.
Filler materials should be used in conjunction with pulsed laser welding to weld heat-sensitive components, including electronic housings. We have achieved great success with our unique Laser Stir Welding process. It strengthens aluminum welds, which are prone to cracking.
In The End
Laser welding aluminum to stainless steel is a revolutionary innovation in the changing world of manufacturing. The smooth combination of these two unlike materials improves structural integrity and creates new opportunities. We at Fiber Laser Welder lead this revolution with our unique knowledge and modern technology. Be sure that every weld will be exact, long-lasting, and reasonably priced because of our dedication to perfection. Together, we are transforming the future of manufacturing.
