City Guilds Model Questions Vol1 2018 Engineering Question 22
Practice objective / multiple choice question 22 from the 2018 City Guilds Model Questions Vol1 Engineering examination.
A steel gear is to be hardened by the following heat‑treatment sequence: austenitising at 850 °C for a time (a) minutes, immediate oil quench (time negligible), then tempering at 200 °C for (t) minutes. The final Rockwell hardness (H) (in HRC) after tempering is approximated by (H = 65 - 0.05,t). The austenitising time must be at least 30 min, and for every additional 10 min beyond 30 min the required tempering time decreases by 5 min. To obtain at least 55 HRC, determine the minimum total heat‑treatment time ((a + t) minutes).
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About This Question
This is City Guilds Model Questions Vol1 2018 Engineering Question 22. It is one of the objective questions from the 2018 City Guilds Model Questions Vol1 Engineering examination.
Difficulty level: Hard .
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