Bevel protractor: The bevel protractor is a direct angular measuring instrument, and has graduation marked from 0° to 180°. Angles can be measured within an accuracy of 1° using this instrument.
A simple protractor is a basic device used for measuring angles with a least count of 1° or 60 minutes.
The number of teeth in hacksaw blade used for cutting high carbon steel is 18.
Steel is an alloy of iron with greater than 0.02 % carbon but less than 2%, and cast iron is an alloy of iron containing a even more carbon between 2 and 4%.
Cast iron (usually, but not always) compared to steel has:
Higher damping ability.
Higher thermal capacity.
Higher fragility/ lower toughness.
Higher stability at higher temperatures.
Lower electric conductivity.
Lower thermal conductivity.
Lower coefficient of friction.
Normalizing involves heating steel to above 50°C above the upper critical temperature, (for hypo-eutectoid steel) and to 50°C above the lower critical temperature (for hyper eutectoid steel). Holding at this temperature for a shorter time to prevent grain growth and finally, cooling in air.
Critical Cooling Rate - The minimum rate of continuous cooling just sufficient to prevent undesired transformations. For steel, the slowest rate at which it can be cooled form above the upper critical temperature to prevent the decomposition of austenite at any temperature above the Ms. The limiting rate at which austenite must be cooled to ensure that a particular type of transformation product is formed.
Critical cooling rate is slowest cooling rate that converts 100% austenite to 100% martensite