Question

for plain carbon steel, all of the following are true except:

1. steel can be hardened without carburizing
2. yield strength of a steel can be increased by cold rolling
3. high carbon steel is less ductile than medium carbon steel
4. larger grain size sheet is stronger than small grain size steel.

Which is not true ???

Answer 1

Ans :- 4

1)This is true.

Steel can also be hardened by Nitriding , Carbonitriding, Nitrocarburizing.

2) This is true.

Yield strength of steel can be increased by cold rolling however ductility gets reduced.This is also called strain hardening or work hardening.This makes steel harder and stronger through plastic deformation.

3) This is true .

High carbon steel is less ductile than medium carbon steel because as the amount of carbon increases hardness increases and ductility decreases.

4) This is false.

Strength of most steel and metals depends on grain size.For larger grains there is a more probability of dislocations.So due to more ease to dislocate larger grain size sheets are weaker than small grain size sheets.