this project is to study about free cutting steels and machinability property and to focus on newly developed Lead Free- Free Cutting Steel. Points are given below about project:- And also explained about Built up edge - Chip Formation to increase the machinability. effect of alloying elements on free cutting steel. manufacturing process of free cutting steel. BASED ON CHROMIUM AND CARBON ADDITION. To avoid Lead Hazardous problem and environmental friendly.

1. Presented by :- Mukesh kumar
Yogesh kumar
Guided by :- Mr. Bhupendra kumhare
Project Goals :-
The main goal of this project is to study about Free Cutting Steels and
machinability property, and to focus on newly developed Lead-free grade
of Free Cutting Steels,.

2. INTRODUCTION:-
Free cutting steel is the name given to those category of iron-carbon
alloys that can be easily worked during machining operation.
If a steel part is to be made by machining such as screw, bolts, nuts,
etc. then the free cutting steel can be used, and the main property
required for such type of steel is machinability.
The basic criteria for making free cutting are given below:-
1. Tool wears as low as possible at cutting times as long as possible.
2. Sufficient surface quality.
3. Low cutting forces and temperature to allow for the application of
sensitive cutting tools and machines.
4. Short, light breaking chips to ensure undisturbed chip removal.
All those properties are very necessary for better application of free
cutting steel.

3. APPLICATIONS OF FREE CUTTING STEELS:
Free cutting steel are suitable for application where good machinability is the
prime consideration. They are therefore used for rapid production on single or
multiple spindle automation lathes and capstan lathes of finely finished
components which will not be subjected to high stress in service, e.g. light duty
studs, cycle components and many intricate parts for textile and printing
machinery.

4. FREE CUTTING STEEL AND MACHINABILITY:
In 1897 it was discovered that sulphur is able to improve machinability and
therefore since 1903 low carbon free cutting steel with sulphur addition has
been produced.
The free cutting steels are resulphurised grades, i.e. have initially added
sulphur (0.08-0.300%), which improve the machinability and find application
for making less critical parts, as these have low toughness, low corrosion
resistance and causes problem in hot working. Sufficient manganese (more
than four times of content of sulphur ) is added, which form globular MnS
particles (or elongated stringer in rolled form ) in ferrite matrix. MnS break the
continuity of ferrite matrix and promote chip formation.
Criteria for good machinability:
• Removal of chips with satisfactory surface finish at lower cost.
• Metal should deform plastically so that fracture does not occur
continuously.
• Metal should have good thermal conductivity so as to increase the life of
tool tip.
• Coarse grained steel preferable as they have low toughness.
• MnS ratio should be around 4:1.

5. However in every machining process the important steps are:
• The metal is plastically stressed just ahead of the cutting edge of
the tool.
• The metal fracture approximately perpendicular to the tool tip and
the form discontinuous chips.

6. EFFECT OF ALLOYING ELEMENT IN FREE CUTTING
STEEL
CHEMICAL COMPOSITION OF FREE CUTTING STEEL
Carbon:- Carbon content in steel, increases the hardness of steel and
reduced the ductility of steel. The machine surface of very soft and
ductile steel is rough, uneven and torn, and of very hard steel is
notched and dull. For better machining process the hardness of the
low carbon resulphurised grade required BHN=110-120 and
maintain the carbon content in billet is 0.06-0.08%.
GRADE %C %MN %SI %P %S %PB
EN1A 0.07-.015 0.80-1.20 0.10 0.070 0.300 --
12L14 0.015MAX. 0.80-1.20 0.10 0.070 0.300 0.34-0.38
Phosphorus: - Adding up to 0.1 % phosphorus (P), which is
characterized by the lowest melting temperature of only P
= 44c, affects the machinability positively. Particularly,
chip breakage and surface quality can be improved due to
embrittlement of the ferrite grains.

7. Sulphur & manganese:-
Admittedly, sulphur is only slightly soluble in steel and therefore the addition of only
small amounts results in the formation of iron sulphide FeS, which has a melting point
of only FeS = 988ｰC. When cooling down melted steel, FeS settles at the solidified
crystals. When heating steel, the grain boundaries weaken in a temperature range
from 800 to 1000ｰC and lead to red brittleness, which implicates possibly failure in
warm forming processes.
At temperatures exceeding 1200-C FeS liquefies and causes hot breakage. In order to
prevent this impairing effect, manganese is also added in the steel making process. It
has a stronger affinity to sulphur and therefore builds manganese sulphide MnS,
which is characterized by a high melting temperature of MnS = 1520-C. The sulphides
solidify prior to the remaining melt as round inclusions, which act as seed crystals.
The manganese content should amount 4 – 5 times of the sulphur content
(Mn = 2.5*S + 0.15) to avoid the formation of FeS. Usual sulphur contents lie between
0.1 and 0.3 % and should not be higher as MnS deteriorates warm roll ability.

8. Fig: MnS streak in EN1A Fig: MnS with Pb streak in 12L14
Lead (Pb):- it is a very soft, highly malleable and ductile, blue-white
shiny metal. Since lead is an element. Lead fume is very
toxic for human heath lead is harmful in very small
amounts but Long term overexposure can cause
numerous health problems, including anemia and other
blood disorders, damage to nervous system and brain as
well as kidney, liver and marrow disease.

9. Fig: MnS inclusion & Pb distribution in 12L14
Importance of MnS inclusion in free cutting steel;
1. Reduction of the friction coefficient in the contact zones due to MnS layer
formation.
2. Reduction of friction due to the crystalline structure of the MnS metalloid. In
the lattice the sulphur atoms are located in a hexagonal plane, which are
likely to slide over each other.
3. In the shear zone MnS operates as stress raiser. The sulphides can be
regarded as voids, which lead to embrittlement of the material and support
the initiation of micro cracks within the primary deformation zone (PDZ).
Subsequently, flow stress is reduced.
4. Reduction of tool wears since MnS performs as a diffusion barrier.
5. Decrease of inner friction and reduction of flow stress of the work piece
material.
Correspondingly, reduction of friction in the contact zones due to lower.
Pb on the tip of MnS

10. Main benefits from adding Lead can be summarized as follows
1. It acts as an inner lubricant and it operates as a lubrication layer between the tool
and the chip bottom side. Friction in the contact zone is reduced and cutting
temperatures as well as cutting forces are lowered.
2. Due to layer formation, lead acts as a diffusion barrier. The tool wear is effectively
reduced.
3. Alloying with lead moves build up edge formation towards higher cutting speeds.
The builds up edges become smaller, more regular and more stable. It is assumed
that lead reduces bonding of the different layers of a build up edge. The deterioration
of surface quality due to the formation build up edges is reduced.
4. In resulphurised steels lead additions are to be found at the tip of manganese
sulphides or they cover the non-metallic inclusions. As a consequence, the
deformation ratio of manganese sulphides is reduced and their function with regard to
stress concentration and crack initiation is improved.
5. Void formation occurs around the inclusions in the plastic deformation zone during
machining. In the case of MnS inclusions the voids reweld due to high compressive
stresses and the voids do not remain in the chip. Lead prevents these voids from
rewelding and supports micro crack formation. The process forces are lowered and
chip breakage is improved.
Generally, in steels lead contents up to 0.35 % are believed to improve
machinability.

11. Energy optimizing furnace
Eccentric bottom tapping tap carbon 0.03% slag free tapping 80% alloy addition
Ladle refining furnace
Feo <=4.0% Aluminum <0. 010 maintain chemistry proper homogenization temperature
Vacuum degassing
5 minute VD Avoid alloy addition after VD assure chemistry and lifting temp.
For proper homogenization of MNS inclusion
Continuous casting process
Super heat (40-50c) EMS current & frequency (240/6.00) Free form internal & surface defect

12. Four face grinding
Suppress the formation of secondary scale Remove the surface defect of
billet
Produce high quality finish product suppress the rolling defect
Rolling mill
Billet temperature in heating zone temperature for
soaking zone
1120-1130o
c 1210-1230oc
Defect free rolling

13. CHIP
FORMATION
Chip forms are quite important as long chips may cause
disturbances in automated manufacturing systems, possibly
deteriorate surface quality and also endanger the safety of the
machine operator. Further, chip jamming may cause non-expectable
chip breakage. Today commercial inserts have chip-forming
elements, but special tools, which are often subject to re-grinding,
do not show any elements leading to chip breakage. Usually these
tools have plane surfaces and they are applied with positive rake
angles in order to keep the forces on a low level.
Although plane inserts with a positive rake angle came into
operation, at all combinations of speeds and feeds chip-breaking
problems did not occur.
Improper chip formation during machining of work piece, which is
responsible for build up edge and result reduced the tool life.

14. MECHANISM OF CHIP FORMATION AS SHOW IN
FIGURE.

15. BUILD UP EDGEThe effect of a buildup of metal deposits sticking to the tool
(which is called “built-up edge”, or BUE) formed during cutting
is known to be high in the machining of relatively soft free-
cutting steel such as a low-carbon free-cutting steel. In other
words, a built-up edge (BUE) grows on the tool tip and works as
a substantial part of the tool. But it’s sticking being not hard
enough, BUE repeats growth and drops, and part of a dropped
BUE can impair the surface roughness of the work piece being
machined.

16. The Relation between MnS and BUE formation. Since cutting a homogeneous
metal gives rise to a maximum stress in a metal portion nearest to the tool
face, a chip separation occurs at a location closest to tool face. It has been
known that MnS has an effect of reducing the resistance to cutting on
account of stress concentration. It is reported that if a heterogeneous
substance like MnS exists in steel, cracking arises out of the heterogeneous
part on account of stress concentration to eventually separate a chip.
With this in mind relative to the distribution of MnS, we can reason that the
presence of coarse MnS as in Fig. 2 causes to separate a chip at a location
somewhat away from the tool by the effect of stress concentration, leaving a
part of the work-piece, in the area between the chip separation point and the
tool, to remain on the tool as a built-up edge. Thus, it is reasoned, if MnS
particles are very small and uniformly distributed as shown in Fig. (b), the
effect of stress concentration is small and the chip separation point is close
to the tool face, leaving a small built-up edge to remain on the tool.
In above mention figure is clearly show that uniform/homogeneous
distribution of inclusion and uniform size of the inclusion shows small build
up age. Show in figure (b), where as figure (a) shows large build up edge.
Larger the build up edge to be form during machining of work piece the
tendency to large wear of tool which reduced the tool life.

17. Figure: - Tool coated with very hard material
Now a day a very special type are tool using for machining. It is TiN
coated tool as show in figure.

18. Replacement of lead
In the past decade intensive efforts were made to replace leaded free cutting
steels by more environment friendly.in spite of this work and of the increasing
political pressure on toxic additives the world wide annually production of
leaded steels still exceeds 2 million tons. The prolonged success of these
steels lies in the low melting point of lead. This guarantees steel inherent
lubrication and liquid mental embrittlement (LME) at low machining speed
preventing built up edge formation (BUE).
A more environmental friendly steel concept developed by Nippon steel.
Graphite inclusion where generated in the steel to obtain a lubricating effect
during machining. In this case an expansive thermal treatment must be used
to change hard cementite to graphite. The resulting differs in strength level
and toughness from conventional free cutting steels. Machinability is also
further improved by the lubricating action of the graphite on the tool surface.
on the other hand, because graphite particle are redissolve into the matrix by
heating in quenching process after machining. The possibility of graphite
becoming a stress concentrator is eliminated, avoiding deterioration in fatigue
strength. The dissolve carbon also improves the hardenability of steel
resulting in improved strength.

19. AS
rolled
Fe3C (cementite)
After graphitizing
C (graphite)
Final product
Solute C
Hot rolled
graphitizing
Quenching and
tempering
Cold forging
machining
Final product

20. CONCLUSION
During our work on Free Cutting Steels I have come to following conclusion
 Free Cutting steel is very special class of re – sulphurised grade steel and is
widely used in automative industries and generally do not require high
mechanical properties.
 The Mn/s ratio should lie below 4:1 to 5:1 so as to from Mns along with lead
impart the machining property of Free Cutting steel.
 Silicon even in very small amount has very detrimental effect on the
properties of Free Cutting Steel.
 Excessive amount of de – oxidizer used would also hinder the machinability.
 The addition of lead to the low carbon steel are to be done in particular
fashion during secondary steel making by adding lead in proper form proper
adding velocity.
 Maintain the superheat as per norms 90(40-50oC)for proper distribution of
sulphur.
 Maintain the electro magnetic stirrer Cutting frequency as per norms for
proper distribution of Mns and supress the segregation of inclusion.
 Soaking temperature (Before rolling ) should be maintained very close to
rolling temperature , so as to have a proper form and dispersion of Mns
inclusion. Thus producing good quality Free Cutting steels.
 Ideally the shape of Cutting tool edge and plasticity of work piece material
determine the quality of machining. Un-coated tools are sensitive to changes
in Cutting parameters, thus Tin and Al2O3 coated tool are used for Free
Cutting Steel machining.

21. CONCLUSION As lead is a hazardous element to deal with the , research work to
develop Free Cutting Steel in which lead is replaced by the other element
such as Tin ,Bismuth , Carbon etc. are in progress.
 One of the main development is by replacing lead with graphite inclusion
in steel , which also impart additional fatigue strength to Free Cutting
Steel.
 Such a type of steel is being developed in Nippon Steels, Japan, where
Free cutting steels are being made with additions of Cr and Si (or other
graphitizing agents).

22. THANKS FOR LISTENING