CNC Ferrous & Non-Ferrous Material Properties 2

Question 1

Which heat treatment process increases the surface hardness of low-carbon steel by introducing carbon into the outer layer?

Accepted Answer

Case hardening (carburizing)

Answer

Carburizing diffuses carbon into the surface of low-carbon steel, allowing the outer layer to be hardened while the core remains tough.

Question 2

What is the primary alloying element that makes stainless steel corrosion resistant?

Accepted Answer

Chromium

Answer

Chromium (minimum 10.5%) forms a passive oxide layer on the steel surface that prevents corrosion.

Question 3

Which aluminum alloy series is primarily alloyed with copper and is commonly used in aerospace applications?

Accepted Answer

2xxx series

Answer

The 2xxx series aluminum alloys use copper as the primary alloying element and offer high strength, making them popular in aerospace structures.

Question 4

Gray cast iron is easy to machine primarily because of which material characteristic?

Accepted Answer

Graphite flakes that act as chip breakers and lubricants

Answer

The graphite flakes in gray cast iron interrupt the chip and act as a built-in lubricant, reducing tool friction and producing short, manageable chips.

Question 5

Titanium alloys are significantly more difficult to machine than aluminum primarily because of:

Accepted Answer

Low thermal conductivity concentrating heat at the cutting edge

Answer

Titanium's poor thermal conductivity traps cutting heat at the tool tip, accelerating tool wear and requiring lower speeds.

(CNC) Computer Numerical Control Machinist Technical Practice Test

(CNC) Computer Numerical Control Machinist Technical Practice Test

CNC Ferrous & Non-Ferrous Material Properties 2