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Plasma cutting is an advanced method used to cut metal - NSC Agricultural Technology - Question 4 - 2017 - Paper 1
Question 4
Plasma cutting is an advanced method used to cut metal. 4.1.1 Name TWO types of gases that may be used when cutting with the plasma-cutting machine. 4.1.2 What is ... show full transcript
Worked Solution & Example Answer:Plasma cutting is an advanced method used to cut metal - NSC Agricultural Technology - Question 4 - 2017 - Paper 1
Step 1
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4.1.3 Name TWO important personal safety items that must be worn for protection when doing plasma cutting.
Answer
Two important personal safety items that should be worn include:
- Fireproof gloves, which protect the hands from burns and sparks.
- Safety goggles or a face shield to protect the eyes from the intense light and flying particles.
Step 4
4.2.1 Name THREE types of metal that can be cut with an oxyacetylene cutting set.
Answer
Three types of metal that can be cut with an oxyacetylene cutting set include:
- Mild steel
- Cast iron
- Stainless steel These metals are commonly used in various applications and can be effectively cut using oxyacetylene methods.
Step 5
4.2.2 Describe the procedures that must be followed to successfully weld with the oxyacetylene apparatus in the overhead welding position.
Answer
The following procedures should be followed:
- Ensure a reduced melting pool is created, big enough to create the desired penetration.
- Adjust the size of the flame for optimal operation.
- Use a slightly thicker welding rod to enhance the weld quality.
- Maintain an appropriate angle of the flame to keep the molten metal stable.
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4.3.2 State THREE factors that can influence the shrinking that occurs in a welding joint.
Answer
Factors influencing shrinking in a welding joint include:
- Welding procedure, as different techniques affect heat distribution.
- Amount of weld overlay can drastically change the cooling rates.
- Degree of resistance, which relates to the material type and thickness.
Step 8
4.3.3 State TWO measures to prevent distortion of a welding joint.
Answer
To prevent distortion, consider the following measures:
- Pre-setting, which involves arranging parts to limit heat expansion during welding.
- Spot welding, which can help control heat input and minimize thermal distortion.
Step 9
4.4 Describe the vertical up arc welding process, as shown in the sketch below.
Answer
In vertical up arc welding, the following points are crucial:
- Welding upwards can create difficulties as the molten metal may tend to run downward.
- A specialized electrode is recommended, as it allows for a quicker melting process.
- The arc must be kept short to maintain control and provide the right penetration into the material.
Step 10
4.5 Explain the procedure to follow when preparing the cast iron for the welding process.
Answer
Preparation of cast iron involves:
- Using a nickel-based welding rod to improve compatibility.
- Setting the amperage on the machine as low as possible to prevent overheating.
- Thoroughly cleaning the surface to ensure no contaminants affect the weld.
- Marking the area to be welded to guide the welding process.
Step 11
4.6.1 State THREE disadvantages of MIG welding.
Answer
Disadvantages of MIG welding include:
- Higher initial setup cost compared to other welding methods.
- Dependency on stable atmospheric conditions, making it less suitable for outdoor work.
- Higher maintenance requirements due to the complexity of the electronic components.
Step 12
4.6.2 State THREE possible causes of porosity when doing MIG welding.
Answer
Possible causes of porosity in MIG welding are:
- Inadequate gas flow, leading to a lack of shielding.
- Blocked nozzle, which can disrupt the gas delivery process.
- Contaminants on the weld area, such as oil or rust, which can trap gases.