Heat Treatment

Question 1

heat treatment

Answer 1

is the controlled heating and cooling of metals to alter their physical and mechanical properties without changing the product shapes

Question 2

uses of heat treatment

Answer 2

• increase the strength of metals
• improve machining
• improve formability

Question 3

basic steps in heat treatment:

Answer 3

• heat the metal to a specific temperature
• hold the metal at temperature for a specific amount of time
• cool the metal in a specific matter

Question 4

what are particularly suitable for heat treatment?

Answer 4

steels

Question 5

steel are good for heat treatment why?

Answer 5

they have alot of carbon

Question 6

break down carbon content of : low carbon steels, medium carbon steels, high carbon steels

Answer 6

• low carbon steels .2%
• medium carbon steels .2-.4%
• high carbon steels >.4%

Question 7

Heat treatment provides an efficient way to manipulate the properties of metal by controling

Answer 7

• rate of diffusion

- rate of cooling within the microstructure

Question 8

in carbon steels fast cooling rates result in____

Answer 8

high degree of hardness

Question 9

steels are heat treated to accomplish:

Answer 9

softening, hardening, material modification

Question 10

softening is performed to

Answer 10

• reduce strength or hardness
• remove residual stress
• improve toughness
• restore ductility
• refine grain size
• change the electromagnetic properties of steel

Question 11

hardening of steel is done to ____

Answer 11

increase the strength and wear properties

Question 12

one of the pre-requisites for hardening is sufficient ____

Answer 12

carbon content

Question 13

the basic types of heat treatment include:

Answer 13

annealing, normalizing, quenching, tempering

Question 14

solubility limit

Answer 14

the maximum amount of solute that can be dissolved in solvent

Question 15

phases

Answer 15

a homogeneous portion of a system that has uniform physical and chemical characteristics

Question 16

microstructure

Answer 16

is characterized by the number of phases present, their proportions, and the matter in which they are distributed or arranged

Question 17

eutectoid reaction

Answer 17

describes the phase transformation of one solid into two different solids

Question 18

in Fe-C system, there is a eutectoid point at approximately…..

Answer 18

0.8 wt% C, 727°C

Question 19

name the types of microstrucutures

Answer 19

-pearlite= ferrite+cementite
coarse/fine

-bainite: ferrite+cementite
very fine

-martensite: is formed when autenitized Fe-C alloy is rapidly cool (quenched)… hardest and strongest

Question 20

define anealing

Answer 20

process for making a material softer while producing uniform material properties…. TEMP SLIGHT ABOVE CRITICAL TEMPERATURE

*RESULTING STRUCTURE coarse pearlite

Question 21

define normalizing

Answer 21

is a process for making materials softer, but products are strong and less ductile compared to annealed materials….. it is less expensive than annealing….

*Resulting microstructure is fine pearlite or bainite

Question 22

define quenching

Answer 22

refers to rapid cooling

makes steel harder and strong by creating….
-Martensite

Question 23

tempering

Answer 23

• heating a martensitic steel to a temperature below eutectoid for a specific period
• resulting structure is martensite

Question 24

microstructure of tempered martensite consists of…

Answer 24

extremely small and uniformly dispersed cementite particles embedded within a continuous ferrite matrix

Question 25

fine cementite particles in ferrite matrix provides ____ and ___ to the matrix

Answer 25

high grain boundary area.. and act as reinforcement