Question 8
High carbon steel is used in the manufacture of
Not quite. Boiler plate is on the low carbon list. It is rolled, bent and welded into pressure vessels, so it needs ductility, the property high carbon steel gives up. In 2022, 8.8% of Queensland students chose (A).
Not quite. Rails are hard wearing, so they sound like high carbon steel, but train rails are on the medium carbon list. A rail also has to take repeated wheel impacts, and that needs the toughness medium carbon steel keeps. In 2022, 13.4% of Queensland students chose (B).
That is it. Step through the hints below to see why. In 2022, 65.1% of Queensland students chose (C).
Not quite. Crankshafts are on the medium carbon list with shafts, axles and gears. A crankshaft needs strength with toughness more than it needs hardness. In 2022, 12.0% of Queensland students chose (D).
Start from the list for the steel the stem names. The 2025 syllabus gives it word for word, and the formula book does not.
High carbon steel, 0.60% to 2.0% carbon: high-strength spring materials and wires, cutting tools, punches, dies and industrial knives.
Punching tools are punches. That is (C).
Place the other three so you know why they are wrong. Pick each option under the axis to see it land.
That rules out (A), (B) and (D).
The list follows from the microstructure. Even at the bottom of the high carbon band the steel is mostly pearlite.
$$\frac{0.60}{0.83}\approx72\%\text{ pearlite}$$
Hard cementite layers in all that pearlite give the hardness and wear resistance a punch needs to shear metal and keep its edge.
Punches are on the high carbon list in the syllabus: high-strength spring materials and wires, cutting tools, punches, dies and industrial knives. Boiler plate is low carbon, and train rails and crankshafts are medium carbon.
The most common wrong answer was (B), from linking hard-wearing rails to the hardest steel. Rails are on the medium carbon list because they need toughness as well as strength. Learn the three lists as lists, since the multiple choice items test them almost word for word.
Only mark this done when you could do it without help. Reading the solution does not count.
Question wording and any figures are from the 2022 QCAA Engineering external assessment, © State of Queensland (QCAA) 2022, licensed under CC BY 4.0, and have been adapted, except where a third-party source is named. Tangent Tuition is not affiliated with the QCAA.
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