Aluminum laser cutting & welding (2)

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Alexandria University Faculty of Engineering Production Engineering Dept. Presented By: Nesma Abdul lateef Basant A. Omarah

Transcript of Aluminum laser cutting & welding (2)

Page 1: Aluminum laser cutting & welding (2)

Alexandria University Faculty of Engineering Production

Engineering Dept.

Presented By:

Nesma Abdul lateef

Basant A. Omarah

Page 2: Aluminum laser cutting & welding (2)

*Principle of laser cutting *Aluminum oxide laser cutting

*Aluminum/Aluminum alloys *Advantages /Disadvantages of laser cutting

*Principle of laser welding *Aluminum alloys

*Wrought alloy series designation *Advantages /Limitations

*Applications

*Conclusion

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The laser beam is transferred to the workpiece and focused onto a small spot. The heat melts, evaporates the workpiece. The laser beam is surrounded by a nozzle which enables a which enables a flow of cutting gas to flush out the melt or vaporize it.

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*Aluminum is difficult to cut with a laser because it is both reflective and has a high thermal conductivity.

*Because of these characteristics, laser cutting aluminum requires special handling and equipment to provide adequate quality of the aluminum.

* As the thermal conductivity of aluminum is high, much of the energy is transferred laterally into the material, which results

in inefficient cutting and reduced cutting speeds.

*high reflectivity Solution >>

*Laser cutting of aluminum is suitable for thicknesses of up to around 8 mm.

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*Al2O3 particles reinforced aluminum matrix composite (Al2O3p/Al) are becoming used for their excellent physical and chemical properties. However, their poor machinability.

*laser heat-assisted machining is adopted in machining Al2O3p/Al composite. The result the cutting force is reduced by 30–50%, the tool wear is reduced by 20–30% and the machined surface quality is improved in laser-assisted machining as compared with conventional cutting.

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*Aluminum alloys are most often cut by melt shearing using nitrogen gas.

Anodized Aluminum Sheet 1xxx

Aluminum sheet coated with a layer of aluminum oxide which has a low reflectivity to CO2 laser light allowing it to be easier pierced and cut than natural aluminum.

Aluminum-silicon 2xxx:

*Increasing silicon content in the alloy increases the hardness, stiffness and wear resistance of the alloy.

*High silicon content (> 12 %) results in significant changes in machinability of the alloy; in which case, the tool wear increases significantly during machining process.

*The presence of silicon in the alloy alters the thermal resistance of the alloy during laser machining.

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*The laser cutting machines use less energy to cut sheet

metal with respect to the technology of plasma cutting. *Laser cutting is controlled by computer programs, thus

saving considerable amount of work. *Because the machine does not require human intervention,

except for repairs and inspections, the frequency of accidents and injuries is reduced.

*efficiency of a laser cutting machine is very high, and

required design replicas obtained are exact copies of each other

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*Power consumption and efficiency depends on the nature of the

laser for cutting. Usually includes the laser cut high consumption of energy compared to other technologies used for cutting.

*Production rate is not consistent when laser cutting is used. Will

depend largely on the thickness of the workpiece. *Setting regardless of the distance laser and the temperature can

lead to the combustion of certain materials. Some metals tend to discolor when the intensity of the laser beam is not necessary.

*Human intervention is required only in case of trial runs and

repairs. While these actions if by accident, a worker comes into contact with the laser beam, which can cause burns.

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The laser beam is focused onto the workpiece by a set of mirrors. These are used because they are much easier to cool than lenses, which are commonly used in lower-power cutting applications. When the laser beam is moved relative to the workpiece, the energy of the focused laser beam melts the metal so that a joint is formed.

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*Natural oxides on surface + moisture from atmosphere produce hydrogen which is highly soluble in Al & causes porosity

*Anodized aluminum prone to cracking & foams up *Remove Al oxide for overlap joints to increase weld width at interface *1000 series: (e.g. 1050=Al 99.5) welds good. Also 3003, 4032, 4047 okay. *5000 series: (e.g. 5005, AlMg5) most weld good. Filler wire if needed: AlMg5

or AlMg4.5Mn, (e.g. AlMg3 + AlMg5 wire = poor appearance w/ good strength)

*6000 series: (e.g. AlMgSi1 – silicon added for machinability) – not ductile

enough to handle shrinkage stresses & is prone to cracking. Weldable when Si>3% & Mg>4.5% (e.g. 6061). Filler wire used to increase weldability (e.g.AlMgSi1 + AlSi12 wire = good appearance / average strength)

*Shield gas = generally Argon, Helium to avoid inclusions and sink holes

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*Although aluminum alloys are wieldable by other more traditional fusion welding methods, the laser offers unique qualities that make it an ideal technology for joining aluminum alloys. *Most strain-hardenable alloys (for example, AA5182 and AA5754) can be laser welded autogenously, although filler metal can be introduced during laser welding to add reinforcement or to improve the strength and ductility of the joint, if desired. *Many heat-treatable alloys (for example, AA6016) are susceptible to hot cracking during welding, due both to their chemical compositions and the thermal strains induced in the metal during welding. To avoid hot cracking, a filler metal is used to adjust the weld bead composition beyond the crack-sensitive range.

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Industrial experience has shown that hot cracking can be avoided by the addition of an eutectic alloy, such as AI-Si, to the weld. However, this leads to a shorter solidification interval.

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The filler wire technique has two major disadvantages:

*Firstly, the macroscopic properties of the joint will change in an uncontrolled

way.

*Secondly, the small size of the laser beam leads to occasional feeding of filler wire directly into the beam, causing inconsistent penetration and weld-pool instability.

For example, adding a 4043 AI-Si alloy wire to the 6061 alloy weld reduces hot cracking susceptibility, but both the tensile and ultimate strengths are reduced by 50%. Therefore an optimization of the process parameters in order to reduce cracking sensitivity would be highly desirable for the production of light weight high-strength components, especially for

transport equipment industry.

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Aluminum Hood Welding

*Overlap joints

*Al6111 to Al6111 and Al6111 to Al5754 material combinations

*Stitch welds

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Aluminum Airframe Components

Fully welded metallic integral structure *Loading tolerant stringer-skin- joints

*Load adapted clip-skin-joints

*Damage tolerant skin-skin joints

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*High quality welds could be made in a number of aluminium alloys using a variety of laser sources and processes. Joint efficiencies of 95% could be reached when welding a non-heat treatable alloy. After heat treatment, joint efficiencies could also reach 95% for welds in heat treatable alloys.

*Cracking results have been found that extend current knowledge in an interesting way.

*For four of the aluminium alloys in this study, the pulsed Nd:YAG welds showed less cracking than those made with the continuous Nd:YAG laser. the continuous Nd:YAG laser produced more cracking than the CO 2 laser.

*Note that less (or no) cracking would be expected in many real applications as no cracking was seen when making the butt welds for tensile testing; the constraints introduced by the crack test are particularly severe.