1. TOPIC : CLASSIFICATION OF MATERIAL AND
EFFECT OF ALLOYING ELEMENTS ON STEEL
PURPOSE : TO UNDERSTAND THE METALLURGICAL
EFFECT OF ALLOYING ELEMENTS AND ITS
IMPACTON MECHANICAL PROPERTIES
WELCOME
3. METALS AND ALLOYS
FERROUS
Non-ferrous
CERAMICS AND GLASSES
MgO, ZnO , SiC
soda-lime Glass,
concrete, Cement
ORGANIC POLYMERS
Plastics
Rubbers
Fiber reninforced plastics
carbon reninforced rubber
MAJOR GROUPS OF ENGINEERING MATERIAL
COMPOSITES : Combination of two or more materials that has properties different from its constituents
Steels
of next
century
4. CLASSIFICATION OF FERROUS METALS
UPTO 2% C 2% ~4.43% C
STEELS CAST IRON
CLASSIFICATION OF STEEL
( ON THE BASIS OF %C )
1) LOW C STEEL (LESS THAN0.3%)
2) MEDIUM C STEEL ( 0.3 ~0.6 %)
3) HIGH C STEEL ( MORE THAN 0.6%)
( ON THE BASIS OF %ALLOY )
1) LOW ALLOY STEEL (LESS THAN 5%)
2) MEDIUM ALLOY STEEL ( 5~10 %)
3) HIGH ALLOY STEEL ( MORE THAN 10%)
5. ALLOTROPIC CHANGES IN IRON
1594
1395
910
768
HEATING
LIQUID
DELTA - Fe
GAMMA - Fe
ALPHA - Fe
ALPHA - Fe
MAGNETIC
DELTA Fe BCC 1594
GAMMA Fe FCC 1395
ALPHA (NON-MAGNETIC) BCC 910
ALPHA (MAGNETIC) BCC 768
REVERSIBLE
7. Fe-C PHASE DIAGRAM
# IT IS ALSO CALLED Fe- Fe3C DIAGRAM.
# IT INDICATES PHASES PRESENT AND PHASE CHANGES OCCUR DURING HEATING
AND COOLING.
# %C SOLUBILITY VARIES IN DIFFERENT FORMS OF Fe
DELTA Fe 0.1% MAX.
GAMMA Fe 2.03% MAX.
ALPHA Fe 0.008% AT RT MAX.
# REACTIONS OF Fe-C DIAGRAM
PERITECTIC REACTION ( L + - Austenite)
EUTECTIC REACTION ( L + Fe3C - Ledeburite)
EUTECTOID REACTION ( + Fe3C - Pearlite)
9. Fe-C PHASE DIAGRAM
Cementite :
Fe3C
contains 6.67% C
hard and brittle interstetial compound
high compressive strength
hardest structure that appears on diagram
Austenite :
interstitial solid solution of C dissolved in (FCC ) Fe
%C solubility - 2% at 1147°C
not stable at room temperature
10. Fe-C PHASE DIAGRAM
Ledeburite :
Eutectic mixture of austenite and cementite
Contains 4.43% C and forms at 1147°C
Ferrite:
interstitial solid solution of a small amount of C dissolved in
(BCC ) Fe
%C solubility - 0.008% at RT
softest structure that appears on the diagram.
Pearlite :
platelike lammelar structure of ferrite and cementite
eutectoid mixture containing 0.8%C
11. EFFECT OF ALLOYING ELEMENTS ON
Fe-C PHASE DIAGRAM
FERRITE STABLIZER
Cr ; W ; Mo ; V ; Si
AUSTENITE STABLIZER
Mn ; Ni ; Co ; Cu
ENLARGE AUSTENITE
REGION
STABLE PHASE AT RT
RESTRICT SEPRATION
OF CARBIDES
REDUCE C SOULBILITY
IN Fe
REDUCE AUSTENITE
REGION
12. Effect of various elements in steel
EFFECT OF S:
Always present in steel as inclusion (FeS and MnS)
Higher amount - undesirable ( 0.02 to 0.05 Max.)
HOT-SHORTNESS (FeS)
disintigration at high temperature during
rolling and forging.
MnS
FREE CUTTING STEEL
%S added upto 0.30~0.60 for better machinability
13. Effect of various elements in steel
EFFECT OF P:
Always present in steel .
Higher amount - undesirable ( 0.02 to 0.05 Max.)
COLD-SHORTNESS
reduction in impact stg. At low temperature
FREE CUTTING STEEL
Added in certain grades of steel upto 0.12% to
improve machinability
14. Effect of various elements in steel
EFFECT OF Si:
It dissolves in ferite increasing strength and hardness without
lowering ductility
Dexodizer - during casting of ingots ( 0.1 ~0.3 %)
0.3~0.5~% Si added to increase strength and soundness of casting
15. Effect of various elements in steel
EFFECT OF Si:
Electric steel :
%C ~ 0.5 max. ; % Si 3.0 ~4.0
for manufacturing cores of electric motors, generators and
transformers.
Spring steel :
%Si ~2.0 ; %Mn ~1.0 ; %C 0.5 ~0.7
with proper heat-treatment , this category have high elastic
limit and fatigue strength.
These steels are used to manufacturing springs , chisels and
punches
16. Effect of various elements in steel
EFFECT OF Mn:
It dissolves in ferrite to increase strength and hardness
It increases hardenability to a certain extent
It takes care of S in steel by forming MnS
(for this purpose Mn should be 3 to 8 times that of S)
HADFIELD STEEL
Mn up to 12 ~14 %
wear resistant, tough and non-magnetic steel
17. Effect of various elements in steel
EFFECT OF Ni:
It dissolves in ferrite, increasing hardness, strength and toughness
without sacrificing ductility
It increasing hardenability of steel
It increases impact resistance of steel at very low temperature
Higher amount of Ni is added to increase corrosion resistance
of high Cr steels
18. Effect of various elements in steel
EFFECT OF Cr:
Cr increases hardenability
It forms carbides havigg high hardness and wear resistance
Cr provodes strength, wear and oxidation resistance at elevated
temperature.
Higher amount of Ni is added to increase corrosion resistance
of high Cr steels
19. Effect of various elements in steel
EFFECT OF Mo:
Mo increases hardenability
It forms carbides having high hardness and wear resistance
0.15 ~0.30 % Mo is added to enhance the effect of other alloying
elements such as Mn , Ni , and chromium
It eliminates temper brittleness in steel
20. Effect of various elements in steel
EFFECT OF V:
V increases hardenability
It inhibits grain growth when steel is heated at high temperature.
V is a strong carbide former. Vanadium carbides posses high
hardness and wear resistance
V improves fatigue resistance
21. Effect of various elements in steel
EFFECT OF W:
W increases hardenability
It forms carbides having high hardness and wear resistance
It is important alloying element in tool steel
EFFECT OF Ti:
It is a strong carbide former
Ti in ss - to fix C and prevent ppt of chromium-carbide
22. Effect of various elements in steel
EFFECT OF Cu:
0.1 ~0.4% is added to get increased atmospheric corrosion
Effect of Al :
0.01 ~0.06 % - for fine grained steel
1 ~3 % in nitriding steel
Effect if B :
Increases hardenability ( 0.001 ~0.005%)
23. ALLOY STEELS
1) FREE CUTTING STEEL :-
- High machinability
- High quality surface finish
- %S - 0.3 ~0.6 % ; %P - 0.12 max.
(S present in MnS inclusions which promote formation
of short brittle chips)
- % Pb upto 0.35 % also improves machinability
(Pb exists in very small sub-microscopic globules)
Pb does not decrease ductility, toughness and other
mechanical properties
24. ALLOY STEELS
2) SPRING STEEL :-
(i) Medium and high C , plain C steels with higher
amount of Mn.
(ii) Medium C alloy steel with Mn and Si as main alloying
elements.
Cr, Ni, Mo , V may be added in place of Si
25. ALLOY STEELS
3) STAINLESS STEEL :-
(i) Austenitic (Cr + Ni min. 25%)
(ii) Ferritic (Cr 14 ~27)
(iii) Martensitic ( Cr - 11.5 ~ 18)
(iv) Precipitation hardening stainless steel
( Cr + Ni + Mo , Cu , Al)
26. ALLOY STEELS
4) TOOL STEEL :-
(i) WATER HARDENING TOOL STEEL
High C steel ( upto 1.40%)
Cr , V and Mo added for carbide
formation
(ii) SHOCK RESISTANCE TOOL STEEL
%C ~ 0.5 ~0.6
Cr , Mo and W added to improve stg
and hardnability
27. ALLOY STEELS
4) TOOL STEEL :-
(iii) COLD WORK TOOL STEEL
for tool intented for cold work application
non-deforming or non-distorting steel
@ Oil hardening steels - C-Mn steels ; Cr & W added to improve
hardenss , hardenability and wear resistance
@ Air hardeing steel - Cr-Mn-Mo steel
@ High C high Cr - air hardened - high hardness and
abrasion resistance
properties of this steel can be further enhanced by adding
Mo , W and V
28. ALLOY STEELS
4) TOOL STEEL :-
(iv) HOT WORK TOOL STEEL
for tool intented for HOT work application
EG. :- DIE CASTING
@ Cr BASE ( Cr - 5 ~7 % ; W , Mo , V added)
@ W BASE ( W 9~18 % Cr ~4% V added)
@ Mo BASE (Mo - 5 ~8 % , Cr, W , V added)
(v) HIGH SPEED STEEL
18 - 4 - 1 ( W-Cr -V)
