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The chassis of electric scooters is often constructed from lightweight industrial grade aluminum - Leaving Cert Engineering - Question 6 - 2022
Question 6
The chassis of electric scooters is often constructed from lightweight industrial grade aluminum. Tungsten inert gas (TIG) welding may be used to fabricate the chass... show full transcript
Worked Solution & Example Answer:The chassis of electric scooters is often constructed from lightweight industrial grade aluminum - Leaving Cert Engineering - Question 6 - 2022
Step 1
Describe, with the aid of a diagram, the process of TIG welding.
Answer
TIG welding, or Tungsten Inert Gas welding, involves creating an arc between a non-consumable tungsten electrode and the workpiece. The process utilizes an inert gas, typically argon or helium, to shield the weld area from oxidation and contamination.
- Arc Formation: An arc is initiated from the tungsten electrode to the metal, allowing the welder to control the molten pool effectively.
- Gas Shielding: Inert gas is fed through a nozzle surrounding the electrode to prevent atmospheric gases from affecting the weld.
- Filler Material: A filler rod may be introduced to the joint to add material to the weld pool.
This process allows high precision and quality in welding applications.
Step 2
Explain two reasons for using TIG welding in fabricating industrial grade aluminum.
Answer
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Precision and Control: TIG welding offers a high degree of precision, making it ideal for intricate aluminum structures. The welder can finely control the heat delivered to the workpiece, minimizing warping and ensuring a clean finish.
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Cleaner Process: TIG welding produces fewer contaminants, as it doesn't involve flux, therefore eliminating slag and reducing cleanup time. This leads to a cleaner, high-quality weld that is essential for critical applications in the automotive and aerospace fields.
Step 3
Outline three functions of the electrode coating in manual metal arc welding.
Answer
- Protection Against Oxidation: The electrode coating prevents atmospheric oxygen from contaminating the molten weld pool, ensuring a stronger bond.
- Slag Formation: It facilitates the creation of slag, which protects the weld from contamination as it cools.
- Stabilizing the Arc: The coating helps to stabilize the welding arc by providing ionization, which enhances the consistency of the weld.
Step 4
Explain two safety hazards associated with resistance spot welding.
Answer
- Electrical Shock: Resistance spot welding involves high voltage, which poses a risk of electrical shock to the operator. Proper grounding and protective equipment must be used.
- Flying Sparks: The welding process generates sparks that can ignite combustibles or cause burns, necessitating the use of adequate protective gear and fire safety precautions.
Step 5
Describe the principles of operation of a step-down transformer in welding.
Answer
A step-down transformer reduces voltage from the primary coil to a lower voltage in the secondary coil. The principle of operation follows Faraday’s law:
- The ratio of turns in the primary and secondary coils determines the transformation of voltage.
- If the transformer has more turns in the primary than in the secondary, the output voltage is lower.
- An ideal transformer maintains the same power level, ensuring the current increases proportionally with the reduction in voltage.
Step 6
Outline the function of a consumable bare wire electrode.
Answer
- Material Supply: The bare wire electrode serves as a filler material during the welding process, contributing to the weld pool.
- Arc Facilitation: It also assists in forming and stabilizing the arc, ensuring continuity during the welding operation.
- Weld Integrity: As the wire melts, it combines with the base materials, enhancing the overall strength and integrity of the weld.
Step 7
Outline how weld cracks and slag inclusions may form on a weld.
Answer
Weld cracks can develop due to excessive thermal stress, particularly when the material cools rapidly and unevenly. Poor weld design or technique can exacerbate this, leading to stress concentrations.
Slag inclusions, on the other hand, may form when molten weld metal becomes trapped in the solidified weld due to inadequate cleaning of the surface or poor manipulation of the electrode. This can weaken the joint by causing discontinuities within the weld metal.
Step 8
Describe the effects of either cracks or spatter on weld strength and finish.
Answer
Cracks in a weld can significantly weaken the joint, leading to failure under stress. They may propagate further, compromising mechanical integrity. Additionally, spatter can detract from the aesthetic finish of the weld, creating an uneven surface that may require additional finishing operations, such as grinding. This not only impacts the appearance but may also affect the overall performance of the welded structure by introducing potential weak points.