Comprehend that the chemical composition of plain-carbon steels contributes to their physical and mechanical properties and therefore to usability in industrial/mechanical applications for - low-carbon steel 0.07% to 0.30% carbon: automobile body parts, wire products, structural plates and sections, seamless tubes and boiler plate - medium-carbon steel 0.30% to 0.60% carbon: automotive components, including shafts, axles, gears and crankshafts, stampings and forgings, train rails, wheels and axles - high-carbon steel 0.60% to 2.0% carbon: high-strength spring materials and wires, cutting tools, punches, dies and industrial knives.

A manufacturing plant produces crankshafts for automotive diesel engines. The engineering specification requires a plain-carbon steel with sufficient hardness to resist wear under cyclic loading, but adequate ductility to withstand torsional shock without brittle fracture. (a) Identify the classification of plain-carbon steel most suitable for this application. (b) State the carbon percentage range for the steel you identified in part (a). (c) Calculate the mass of carbon, in kilograms, present in a 45.0 kg crankshaft forging if the steel contains 0.48% carbon by mass. (d) Explain how the carbon content you calculated in part (c) contributes to the mechanical properties required for crankshaft operation.

A railway infrastructure project specifies the use of plain-carbon steel for continuous welded rail track. The rails must exhibit high wear resistance to withstand repeated wheel contact forces over millions of load cycles, while retaining sufficient ductility to accommodate thermal expansion and minor track settlement without cracking. (a) Identify the classification of plain-carbon steel most appropriate for this rail application. (b) State the carbon percentage range for the steel classification identified in part (a). (c) A single 18.0 m section of rail has a mass of 1,080 kg. If the steel contains 0.52% carbon by mass, calculate the total mass of carbon, in kilograms, within this rail section. (d) Explain how increasing the carbon content from 0.15% to 0.52% affects the hardness and ductility of the steel, and justify why the higher carbon content is preferred for rail track applications.

A remote mining operation in Western Australia requires three steel components for a new materials-handling system: • A 12-metre structural support beam that will be fabricated off-site in three sections, transported 850 km by road, then welded together on-site to form the final assembly • A set of compression springs in a vibrating screen that must withstand 3.2 million load cycles per year while separating ore particles • A large crankshaft for a diesel-powered conveyor drive unit operating under variable torque with peak loads during start-up Explain how the carbon content of plain-carbon steel influences the selection of an appropriate steel classification for two of these components. For each component you select, identify the steel classification, state the relevant carbon content range, and justify your choice by describing how a specific mechanical or physical property arising from that carbon content meets the functional requirement.

A fabrication workshop requires a steel for producing structural I-beams that will be welded on-site to form the frame of a multi-storey building. The beams must be joined easily without cracking and possess adequate load-bearing capacity. Identify which plain-carbon steel classification from the data below is most suitable for this structural application. Use two characteristics related to carbon content to justify your selection.

A structural fabrication workshop stores three grades of plain-carbon steel: 0.15% carbon, 0.45% carbon and 1.2% carbon. A client order requires material for two jobs: forming curved structural sections for a building frame that will be cold-worked on site, and manufacturing precision punches for a metal stamping press. Identify the most suitable carbon steel grade for each application and justify each selection using the relationship between carbon content and mechanical properties.

An automotive manufacturer is selecting a plain-carbon steel for a vehicle crankshaft that must endure cyclic loading and torsional stresses during engine operation. Identify the most suitable plain-carbon steel classification from the table below for this crankshaft application. Use two features of the steel's carbon content and resulting properties to justify your selection.

An engineering consultancy is investigating the failure of three steel components from different industrial settings: • A stamped metal panel from a shipping container that cracked along a weld line during routine handling • A railway wheel that developed surface pitting and micro-cracks after 80,000 km of service • A precision cutting die used in a textile factory that lost its edge geometry after only 12,000 cutting cycles For two of these failures, explain how an inappropriate choice of plain-carbon steel classification (in terms of carbon content) may have contributed to the observed failure mode. In each explanation, identify which classification was likely used, which should have been specified instead, and describe how the difference in carbon content would have altered the mechanical behaviour to prevent or reduce the failure.

A tool manufacturer is producing industrial cutting blades for a metal-stamping press. The blades must retain a sharp edge under continuous operation and resist wear from repeated contact with hardened steel workpieces. Explain why high-carbon steel is the most suitable material for this application, referring to its carbon composition and the mechanical properties that result.

An industrial tooling supplier stocks three grades of plain-carbon steel for different manufacturing applications. Refer to the table below. (a) A client requires steel for stamping automotive gear blanks. Determine which grade (P, Q or R) is most appropriate, and justify your selection by reference to both the carbon content classification and the mechanical properties needed for stamping operations. (b) The supplier purchases Grade P at $2.80 per kilogram and Grade R at $8.40 per kilogram. Calculate how many times more expensive Grade R is per unit of carbon content compared to Grade P. Express your answer to one decimal place.

A manufacturing company is designing a new crankshaft assembly and must select appropriate plain-carbon steel grades for three components based on their mechanical property requirements. Refer to the table below. (a) Determine which steel grade (A, B or C) is most suitable for the crankshaft itself, which requires high toughness and moderate strength. Justify your selection by reference to carbon content and typical applications. (b) Calculate the percentage increase in carbon content when changing from the steel used for the connecting rod to the steel used for the cutting tool that machines the crankshaft.

A railway engineering team is specifying plain-carbon steels for three components of a new freight wagon. Refer to the table below. (a) Identify which steel type (Type X, Y or Z) should be used for the wagon's structural frame, and explain your choice by reference to the carbon content range and mechanical properties required for structural plates. (b) The team initially selected Type X for the wagon wheels but later changed to Type Y after load testing. Calculate the ratio of the carbon content in Type Y to the carbon content in Type X. Express your answer to two decimal places.

A toolmaking workshop manufactures industrial metal-cutting lathe tools that must maintain a sharp cutting edge under sustained high-speed machining operations. The cutting edge experiences temperatures exceeding 600 °C and must resist wear from continuous contact with hardened workpieces. (a) Identify the classification of plain-carbon steel most suitable for this cutting tool application. (b) State the carbon percentage range for the steel classification identified in part (a). (c) A batch of 200 lathe tool blanks is produced, each with a mass of 0.850 kg. If the steel used contains 1.2% carbon by mass, calculate the total mass of carbon, in kilograms, contained in the entire batch. (d) Explain how the high carbon content in this steel contributes to the cutting tool's ability to maintain hardness at elevated temperatures, and state one limitation of using this steel grade for applications requiring impact resistance.

A manufacturing engineer is designing components for a new agricultural harvesting machine. Three critical components require steel selection: • Component X: A blade that must maintain a sharp cutting edge under repeated impact loading while harvesting dense crop stems • Component Y: A structural frame member that will be welded on-site and must resist deformation under variable bending loads • Component Z: A drive shaft transmitting rotational power at 1,200 rpm with cyclic torsional stress For each component, identify the most appropriate classification of plain-carbon steel (low-carbon, medium-carbon or high-carbon) and justify your selection by linking one specific physical or mechanical property arising from the carbon content to the functional demand of that component.

A manufacturing engineer is selecting steel for a new crankshaft assembly in a heavy-duty diesel engine. The component will experience high cyclic loads and requires excellent toughness combined with moderate strength. Explain why medium-carbon steel would be the most appropriate choice for this application, referring to its chemical composition and resulting mechanical properties.

A mining company needs to replace worn conveyor system components. The design engineer must select between medium-carbon steel and high-carbon steel for two different applications: drive shafts that transmit rotational motion under moderate cyclic loading, and cutting blades that shear through rock samples. Explain how the carbon content of each steel type makes it suitable for its intended application in this context.