Blacksmith Gr II — Kerala State Water Transport — 2019 — Official Paper — Kerala PSC PYQ Practice with Answers

Correct answer (Option C):\nHigh carbon steel typically contains a carbon content ranging from 0.8% to 1.5%. This high concentration of carbon makes the steel exceptionally hard, high in strength, and heat-treatable, rendering it highly suitable for manufacturing cutting tools like chisels, drills, and dies.\n\nWhy others are wrong:\nOption A refers to low carbon steel (mild steel) which has below 0.25% carbon. Option B refers to medium carbon steel which ranges from 0.25% to 0.8% carbon. Option D exceeds the typical range for high carbon steels, crossing into the cast iron domain.\n\nStudy tip:\nRemember that as carbon content increases, hardness and strength increase, but ductility and weldability decrease.

Correct answer (Option A):\nMagnetite (Fe₃O₄) contains the highest percentage of iron among the common iron ores, reaching up to roughly 72.4% pure iron content. It possesses strong magnetic properties and is typically black or brownish-black in appearance.\n\nWhy others are wrong:\nOption B (Hematite) contains roughly 70% iron content. Option C (Limonite) is a hydrated iron oxide with lower iron content (~60%). Option D (Iron pyrite) is a iron sulfide containing about 46.6% iron and is majorly used for sulfur production rather than iron extraction.\n\nStudy tip:\nRemember the sequence of iron content in ores from highest to lowest: Magnetite > Hematite > Limonite > Siderite.

Correct answer (Option B):\nHot working is performed above the recrystallization temperature of a metal. Due to thermal expansion, oxidation, and scaling during cooling, it is not possible to achieve close dimensional tolerances with hot working.\n\nWhy others are wrong:\nOption A is wrong because hot working closes and welds internal cavities and porosity. Option C is wrong because mechanical properties like elongation and toughness are improved. Option D is wrong because the high temperatures cause grain refinement via dynamic recrystallization.\n\nStudy tip:\nIf close dimensional tolerances and a smooth surface finish are desired, cold working processes must be used after hot working.

Correct answer (Option B):\nSoft solder is primarily composed as a fusible alloy of Tin (Sn) and Lead (Pb). A common ratio utilized for electrical work is 60% tin and 40% lead, which provides a low melting point and optimal wetting properties.\n\nWhy others are wrong:\nOptions A and C mention copper alloys, which are not constituents of standard lead-based soft solders. Copper is the material usually being joined, not the main soldering alloy constituent.\n\nStudy tip:\nEutectic solder consists of 63% tin and 37% lead, melting exactly at 183°C without entering a pasty stage.

Correct answer (Option B):\nThe standard point angle or lip angle of a general-purpose twist drill intended for drilling structural steels and mild steel is 118°. This angle balances cutting edge strength with effective penetration resistance.\n\nWhy others are wrong:\nOptions A, C, and D list angles that deviate from the standard point angle specified for mild steel. For instance, wider angles like 135° or 140° are used for harder materials, while narrower angles are preferred for softer metals.\n\nStudy tip:\nRemember that harder materials require a larger point angle, while softer alloys require smaller angles to prevent grabbing.