A Project Report On Cost Reduction in Melting - A SQC and Six Sigma Approach
A Project Report On Cost Reduction in Melting - A SQC and Six Sigma Approach
A Project Report On Cost Reduction in Melting - A SQC and Six Sigma Approach
APPROACH
Done at ARUNA ALLOY STEELS PVT.LTD
A PROJECT REPORT
Submitted by
ARUN KUMAR.S
(105914144005)
BACHELOR OF ENGINEERING
IN
MECHANICAL ENGINEERING
SIGNATURE
SIGNATURE
MBA., (Ph.D),
HEAD OF THE DEPARTMENT
SUPERVISOR
Assistant professor
Mechanical Engineering
Mechanical Engineering
Madurai- 625020.
Madurai- 625020.
INTERNAL EXAMINER
EXTERNAL EXAMINER
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENTS
CHAPTER NO
TITLE
PAGE NO.
ABSTRACT
iv
LIST OF TABLES
LIST OF FIGURES
xi
1
INTRODUCTION
11
16
16
16
17
18
19
19
20
21
22
23
24
1.6.1Gate valve
24
26
27
28
29
29
30
31
32
32
1.6.11 Trunion
33
33
33
33
34
34
34
34
6
2
3
\
1.6.19 Bracket
35
35
LITERATURE REVIEW
BASICS OF FOUNDRY
36
36
3.1 Foundry
38
38
38
3.2.1.1 Pattern
39
3.2.2 Methoding
39
3.2.3 Moulding
41
41
42
43
43
3.2.5 Pouring
44
45
3.2.7 Fettling
45
46
47
47
47
61
CASE STUDY
68
68
68
69
70
76
76
76
76
76
76
76
76
77
78
5.2.3.3Ultrasonic Testing
82
83
84
ANNEXURE
87
REFERENCES
95
LIST OF TABLES
Table 1.2.1
PAGE NO
Table 1.2.2
Table 2.1
2
7
37
72
72
72
73
75
75
Table 5.2.3.2.1
79
Table 5.2.3.2.2
79
10
LIST OF FIGURES
Figure 1.2.1-
PAGE NO
Figure 1.2.2
Figure 1.4.1.1
Gate valve
16
Figure 1.4.2.1
Butterfly valve
17
Figure 1.4.3.1
Ball valve
18
Figure 1.4.4.1
Globe valve
19
Figure 1.4.5.1
Check valve
20
Figure 1.4.6.1
Plug valve
21
Figure 1.4.7.1
21
Figure 1.4.8.1
Angle valve
23
44
71
73
73
Scraps + Returns
74
74
77
79
79
80
80
81
82
83
83
CHAPTER 1
INTRODUCTION
12
13
DEMAND( in m t)
GROWTH( in %)
1991-1992
14.84
1992-1993
15
1.07
1993-1994
15.32
2.13
14
1994-1995
18.66
21.80
1995-1996
21.43
14.84
1996-1997
22.12
3.21
1997-1998
22.63
2.30
1998-1999
23.15
2.29
1999-2000
25.01
8.03
2000-2001
26.87
7.43
2001-2002
27.35
1.78
2002-2003
28.897
5.65
2003-2004
31.169
7.86
2004-2005
34.389
10.33
2005-2006
38.151
10.93
2006-2007
49.777
30.47
2007-2008
55.174
10.84
2008-2009
54.833
-0.61
15
still look set for growth. Furthermore, the construction sector is benefiting
from major infrastructure projects. Capital expenditure is to be focused on
road building and the rail network, as well as on the construction and
expansion of ports and airports.
Strong growth in mechanical engineering:
Mechanical engineering output has increased some 10% p.a. over the
past five years. Thanks to the march of technological progress the prospects
for domestic suppliers should improve going forward, while import growth is
slightly crimped. Demand is greatest for building machinery and plasticmoulding machines as well as machine tools and textile machinery. Since the
domestic textile and apparel industry, for example, is focusing further up the
value chain, firms have to make numerous investments in modernising and
expanding their machinery portfolios Makers of building machinery are
benefiting from the large-scale infrastructure projects planned by the Indian
government, while machine-tool makers are being buoyed by the upturn in the
automobile and auto parts industries for example. Exports by the Indian
mechanical engineering industry rose recently by nearly 30% to USD 10 bn.
By comparison, German mechanical engineering firms exported products
worth close to USD 117 bn, including machinery to the value of about USD 1
bn to India. Germany claims a particularly large share of Indian imports of
Woodworking machinery and machine tools as well as pumps and
compressors. The demand for foreign machinery comes from customers
requiring especially high standards of performance and precision.
Booming automobile industry:
The automotive industry may consume a relatively small proportion of
steel output, but its growth rate is the highest of the most important clients for
the steel industry. In India a small but flourishing automobile industry has now
developed that sees its future primarily in the budget price segment and views
the domestic market and other emerging nations as potential markets.
17
18
19
YEAR
SUPPLY (in m t)
GROWTH (in %)
1991-1992
14.33
1992-1993
15.2
6.07
1993-1994
15.2
1994-1995
17.82
17.23
1995-1996
21.4
20.08
1996-1997
22.72
6.16
1997-1998
23.37
2.86
1998-1999
23.82
1.92
1999-2000
26.71
12.13
2000-2001
29.7
11.19
2001-2002
30.63
3.13
2002-2003
33.67
9.92
2003-2004
36.19
7.48
2004-2005
40.05
10.66
2005-2006
42.636
6.45
2006-2007
55.146
29.34
2007-2008
58.233
5.59
2008-2009
59.02
1.35
The growth of the Indian steel industry and its share of global crude
steel production could be even higher if they were not being held back by
major deficiencies in fundamental areas. Investment in infrastructure is rising
appreciably but remains well below the target levels set by the government due
to financing problems.
Energy supply:
Power shortages hamper production at many locations. Since 2001 the
Indian government has been endeavouring to ensure that power is available
Nationwide by 2012. The deficiencies have prompted many firms with
Heavier energy demands to opt for producing electricity with their own
Industrial generators. India will rely squarely on nuclear energy for its Future
power generation requirements. In September 2005 the 15th and largest
nuclear reactor to date went on-line. The nuclear share of the energy mix is
likely to rise to roughly 25% by 2050. Overall, India is likely to be the worlds
fourth largest energy consumer by 2010 after the US, China and Japan.
Problems procuring raw material inputs:
Since domestic raw material sources are insufficient to supply the
Indian steel industry, a considerable amount of raw materials has to be
imported. For example, iron ore deposits are finite and there are problems in
mining sufficient amounts of it. Indias hard coal deposits are of low quality.
For this reason hard coal imports have increased in the last five years by a total
of 40% to nearly 30 million tons. Almost half of this is coking coal (the
remainder is power station coal). India is the worlds sixth biggest coal
importer. The rising output of electric steel is also leading to a sharp increase
in demand for steel scrap. Some 3.5 million tons of scrap have already been
imported in 2006, compared with just 1 million tons in 2000. In the coming
years imports are likely to continue to increase thanks to capacity increases.
Inefficient transport system:
21
23
24
25
26
27
28
The body of ball valves may be made of metal, ceramic, or plastic. The
ball may be chrome plated to make it more durable.
FIGURE 1.4.3.1- BALL VALVE
32
33
34
35
GRADE
EN10213-2
EN10213-4
EN10213-3
: 1.6220
ASTM A 216
: WCB, WCC
ASTM A 217
- Back to Back
- Outer Diameter
- Inner Diameter
- Thickness
BONNET:
Overall Length
Body End Face to Stuff Box Face
Stuff Box - Dome Depth
- Bore Diameter
Body End Flange - OD / Profile Length & Width
- ID / Core Profile Length & Width
Eyebolt Lug Gap, Lug Thickness
Yoke Arm Width & Thickness (if applicable)
Yoke End Hub Dia., Thickness & Core Diameter/ Yoke End Flange profile
Length, Width & Thickness
Wall Thickness (if applicable).
DISC:
Thickness - Top & Bottom
Disc
- Outer Diameter
Guide Slot - Width & Face to Face
T-Slot
YOKE:
Top Flange - Outer Diameter
38
- Inner Diameter
- Thickness
Yoke arm - Width
- Thickness
Bottom Leg
(Bonnet Seat) - Width
- Length
- Thickness
1.6.2 GLOBE VALVE:
BODY:
Overall Length
Side Flange - Back to Back
- Thickness
- Outer Diameter
- Inner Diameter
Bonnet End Flange - Outer Diameter / Profile Square Width
- Inner Diameter
- Thickness
Diffuser ID
Seat Ring
- Bore Diameter
- Pad Thickness
Wall Thickness
BONNET:
Overall Length
Body End Face to Stuff Box Face
Stuff Box
- Bore Diameter
39
- Thickness
- Outer Diameter
Shank
- Outer Diameter
- Length
Disc
- Thickness
- Outer Diameter
- Inner Diameter
- Inner Step Depth
Shank - Length
- Diameter
HINGE:
Hinge
- Boss Height
- Boss Diameter
COVER:
Cover
- Outer Diameter
- Inner Diameter
- Back to Back
-Outer Diameter
- Inner Diameter
- Thickness
Cover flange
- Outer Diameter
- Inner Diameter
Top flange
- Outer Diameter
- Inner Diameter
Wall thickness
PLUG:
Port
- Width
- Height
Overall
- Height
Bottom
- Outer Diameter
Top
- Outer Diameter
COVER:
Cover
- Outer Diameter
- Inner Diameter
- Thickness
- Outer Diameter
- Thickness
- Hub Bore Diameter
- Hub Length
- Back to Back
42
- Outer Diameter
- Inner Diameter
- Thickness
Top flange
- Over Diameter
- Inner Diameter
- Thickness
Ball rotating
Seat
- Inner Diameter
- Inner Diameter
Wall thickness
CONNECTOR:
Overall Length
Side flange
- Back to Back
- Outer Diameter
- Inner Diameter
- Thickness
Ball rotating
- Inner Diameter
Wall thickness
BALL:
Ball
- Outer Diameter
- Inner Diameter
43
- Inner Diameter
- Thickness
Side flange
- Outer Diameter
- Inner Diameter
- Thickness
Top flange
- Inner Diameter
- Thickness
- Face to Face (Overall Length)
- Back to Back
Cover flange - Outer Diameter
- Inner Diameter
- Thickness
Wall Thickness
1.6.9 FOUR WAY GLOBE VALVE BODY:
Side flange - Face to face
- Back to back
- Inner diameter
- Outer diameter
- Thickness
Bottom flange - Outer Diameter
- Inner Diameter
- Thickness
Seat ring
- Bore Diameter
- Pad thickness
Wall thickness
Top flange face - Bottom flange face
Top flange - Outer Diameter
- Inner Diameter
45
- Thickness
1.6.10 ISO PAD:
- Outer Diameter
- Bore Diameter
- Step OD
- Thickness
1.6.11 TRUNION:
- Outer Diameter
- OAL Height
1.6.12 STEM HOUSING:
- Outer Diameter
- Bore Diameter
- OAL
1.6.13 BODY TUBING SPOOL:
Flange
- Outer Diameter
- Thickness
- Inner Diameter
- OAL
46
- Bore Diameter
- Inner Diameter
- Thickness
- Wall Thickness
- Outer Diameter
- Inner Diameter
Cover end
- Outer Diameter
- Inner Diameter
- Seat Diameter
47
- Outer Diameter
- Bore ID
- Thickness
CHAPTER 2
LITERATURE REVIEW
In India, productivity levels of SMEs are alarmingly low due to host of
problems (Director of Industries, 2003). For higher productivity in SMEs,
48
Defects reduction will be one of the most promising and viable strategy and
it will also be capable to cope up the emerging future challenges (Antony et al.,
2005). Six Sigma concept has been widely used in manufacturing sector
from last 25 years as company like Motorola has been improving its
processes since 1986 by using its defect reduction approach (Eckes,2001).
Similarly manufacturing giants like General Electric and Honey Well have
been using it as cycle time reduction tool, since 1996 (Zu et al., 2011). Other
well-known companies like Ford, Caterpillar, Our lady of Lourdes medical
centre, LG and Samsung etc. are also practicing Six Sigma as a quality
improvement technique in their respective manufacturing processes from
1999. Table 1 cites major works of the researchers related to application of
Six Sigma in manufacturing sector during the past decade.
After analyzing significant contribution of Six Sigma approach among
SMEs, an effort has been made to implement DMAIC methodology in nonferrous (medium scale) foundry, without ignoring its existing Indian
constraints. It further demystifies various myths regarding Six Sigma and
SMEs, specifically for the foundry unit.
49
S No
Author(s)
Henderson &
Evans (2000)
Company /
Unit
General Electric
Company
Medium sized
welding unit
Does et al.
(2002)
A bulb
manufacturing
SME
Anderson et al.
(2006)
A gravity die
casting unit
Cranberry
Drinks Ltd.
Improvement in
packing
process.
Antony and
Desai (2009)
Wilson Tools
Shorten the
heat treatment
time
Singh and
Khanduja
(2010)
A copper wire
manufacturing
plant
Quality
improvement in
rolling
operation
Parameters
Achievements
Implementation
as a quality
tool. Reduced
the cycle time
at repair shops.
Optimization of
welding process
parameters
Annual saving
of $2 billion
Process
improvement
done
Joint strength is
increased by
26% and scrap
work is reduced
by 3%
Sigma level
increased from
3.1 to 4.5
Improve the
process and
reduced the
shell cracking
of bulbs
Casting scrap
reduced from
23% to 11%
CHAPTER-3
BASICS OF FOUNDRY
50
40% reduction
in
manufacturing
cost with
annual savings
of $72000 p.a.
DPMO level
improved from
3011 to 178
only. 17%
reduction in
packing time.
Roughly $10000
per year
savings. 2%
reduction in
overall Lead
time
Defect are
decreased by
19% within nine
months of
DMAIC project
3.1 FOUNDRY:
A Foundry is a factory that produces metal, castings. Metals are cast
into shapes by melting them into a liquid, pouring the metal in a mould, and
removing the mould material or casting after the metal has solidified as it
cools. The most common metals processed are aluminium and cast iron.
However, other metals, such as bronze, brass, steel, magnesium, and zinc,
are also used to produce castings in foundries. In this process, parts of
desired shapes and sizes can be formed.
3.2 PROCESSES OF A FOUNDRY:
PATTERN MAKING
METHODING
MOULDING
MELTING
LABORATORY TESTS
FETTLING
QUALITY CONTROL
DESPATCH
3.2.1 PATTERN MAKING:
The making of patterns, called pattern-making, is a skilled trade that
is related to the trades of tool and die making and mould making, but also
often incorporates elements of fine woodworking. Patternmakers learn their
51
52
The
patternmaker
or
Foundry
engineer
decides
where
the Sprues, gating systems, Cores and Risers are placed with respect to the
pattern. Where a hole is desired in a casting, a core may be used which defines
a volume or location in a casting where metal will not flow into.
Sometimes chills may be placed on a pattern surface prior to moulding,
which are then formed into the sand mould. Chills are heat sinks which enable
localized rapid cooling. The rapid cooling may be desired to refine the grain
structure or determine the freezing sequence of the molten metal which is
poured into the mould.
Because they are at a much cooler temperature, and often a different metal
than what is being poured, they do not attach to the casting when the casting
cools. The chills can then be reclaimed and reused. The design of the feeding
and gating system is usually referred to as METHODING, or methods design.
It can be carried out manually, or interactively using general-purpose CAD
software.FOOT UP, RISER, CHILL, KALPAD, BRACKET, VENT, METALPAD, etc., are some terms used in METHODING.
Foot Up is used to cover extra material and to avoid defects such as Cracks,
Pinholes, & Gas holes. Blind & Open are two types of Risers and open riser
will be at maximum point; it is part of the gating system that forms the
reservoir of molten metal necessary to compensate for losses due to shrinkage
as the metal solidifies. Normally, metal will be at room temperature; So, Chills
are used to increase the strength of metal.
Kalpad is used to maintain the heat of metal. Bracket is used to avoid
cracks. Vents are used to remove air from surface. Metal-pad is used for easy
flow of metal. Patterns are given 3% allowance. Core boxes are given 2 to
2.5% allowances.
53
3.2.3 MOULDING:
Moulding sand, also known as foundry sand, is sand that when moistened
or oiled tends to pack well and hold its shape. It is used in the process of sand
casting. Greensand is an aggregate of sand, bentonite clay, pulverized
coal and water. Its principle use is in making moulds for metal casting. The
largest
portion
of
the
aggregate
is
always
sand,
which
can
be
the reverse change from liquid to solid, it is referred to as the freezing point or
crystallization point.
result in a mechanical force, which stirs the molten metal. The benefits of this
stirring include the production of a thermally and chemically homogeneous
melt and excellent alloy and charge absorption.
3.2.5 POURING:
57
to pour a full mould. Since this metal must be re-melted as salvage, the yield of
a particular gating configuration becomes an important economic consideration
when designing various gating schemes, to minimize the cost of excess sprue,
and thus melting costs.
3.2.8 HEAT TREATMENT:
Heat treating is a group of industrial and metalworking processes used to
alter the physical, and sometimes chemical, properties of a material. Heat
treatment involves the use of heating or chilling, normally to extreme
temperatures, to achieve a desired result such as hardening or softening of a
material. Heat treatment techniques include annealing, case hardening,
precipitation strengthening, tempering and quenching. After de-gating and heat
treating, sand or other moulding media may adhere to the casting. To remove
this, the surface is cleaned using a blasting process. This means a granular
media will be propelled against the surface of the casting to mechanically
knock away the adhering sand. The media may be blown with compressed air,
or may be hurled using a shot wheel. The media strikes the casting surface at
high velocity to dislodge the moulding media (for example, sand, slag) from
the casting surface. Numerous materials may be used as media, including steel,
iron, other metal alloys, aluminium oxides, glass beads, walnut shells, baking
powder among others. The blasting media is selected to develop the colour and
reflectance of the cast surface.
3.2.9 QUALITY CONTROL:
Quality control is the process of assuring the products with no defects and
good quality. Some of the methods used for Quality Control are:
Magnetic Particle Inspection;
60
Radiographic testing;
Ultrasonic testing;
Penetrant testing;
Visual inspection;
Dimensional inspection.
3.2.10 DESPATCH & PACKING
Finished products are sorted, tagged, packed and loaded for transportation
in this area. For export customers, un-machined castings are packed into wooden
crates or boxes depending on the customers preference. For very large castings,
wooden pallets are used. Machined castings are given protection covering in
machining surface to avoid damages. Protective Anti-Rust coatings are given for
Carbon steel and Alloy steel.
3.3 TERMS USED IN MELTING AREA OF FOUNDRY:
Charge
A given weight of metal introduced into the furnace.
Charging Crane
System for charging the melting furnace with a crane.
Charging Door
Opening through which the furnace is charged.
Charging Floor
Floor from which the furnace is charged.
Charging Machine
Machine for charging the furnace, particularly the open hearth.
61
62
Designations
Type of metal named, as steel, malleable, nonferrous, etc.
Disappearing Filament Pyrometer (Optical Pyrometer)
A telescope in which a hot body is viewed through an eyepiece and
temperature is measured by the matching colour of a calibrated lamp filament
with colour of hot metal.
Electric Arc Furnace
A crucible furnace that uses an electric arc, similar to an electric arc
welding operation, to melt metal.
Electrical Precipitator
In air pollution control, the use of electrodes in stack emissions emitting
high voltage; particles 0.1 micron and smaller can be attached and collected at
discharge electrode.
Fabrication
The joining usually by welding, of two or more parts to produce a
finished assembly. The components of the assembly may be a combination of
cast and wrought materials.
Feed Material
The volume of molten metal from which a casting feeds as it shrinks
(contracts) during solidification.
Fettle
A British term meaning the process of removing all runners and risers
and cleaning off adhering sand from the casting. Also refers to the removal of
slag from the inside of the cupola and in Britain to repair the bed of an open
hearth.
Filter
The filtering out of unwanted gases in the casting at pouring off portion
of making the casting.
Firebrick
Brick made of refractory clay or other material which resists high
temperatures.
Foundry (Foundries, plural)
A process or art of casting metals. The buildings and works for casting
metals.
63
Foundry Ladle
A vessel for holding molten metal and conveying it from furnace to the
moulds.
Foundry Returns
Metal in the form of sprues, gates, runners, risers and scrapped castings,
with known chemical composition that are returned to the furnace for remelting.
Hand Ladle or Shank
A small ladle carried by one man.
Heat
A single furnace charge of metal to be used for pouring directly into
mould cavities; a heat may be all of part of a master heat.
Heel
Metal left in a ladle after pouring or in a furnace after or between
tapping.
Holding Furnace
Usually a small furnace for maintaining molten metal at the proper
pouring temperature, and which is supplied from a large melting unit.
Holding Ladle
Heavily lined and insulated ladle in which molten metal is placed until it
can be used.
Inclusion(s)
Particles of slag, refractory materials, sand or de-oxidation products
trapped in the casting during solidification.
Induction Furnace
AC melting furnace, which utilizes the heat of electrical induction.
Induction Heating
Process of heating by electrical resistance and hysteresis losses induced
by subjecting a metal to the varying magnetic field surrounding a coil carrying
an alternating current.
Ingot
Casting to be later forged or hot worked. Also, a form used for
convenient handling of cast iron, aluminium, and other commercial metals.
64
65
Metallurgy
Science dealing with the constitution, structure, and properties of metals
and alloys, and the processes by which they are obtained from ore and adapted
to the use of man.
Mica Schist
A type of refractory rock used for lining cupolas and other melting
furnaces.
Nozzle
Pouring spout of the bottom -pour ladle.
Nozzle Brick
A thick-walled tubular refractory shape set in bottom of a ladle through
which steel is teemed.
Open Flame Furnace
As opposed to the crucible furnace; in the open-flame furnace the metal
charge is confined in the refractory lining, with the flame and products of
combustion coming in direct contact with the metal.
Open Riser
Riser whose top is open to the atmosphere through the top of the mould.
Optical Pyrometer
A temperature measuring device through which the observer sights the
heated object and compares its incandescence with that of an electrically
heated filament whose brightness can be regulated; or the intensity of the light
admitted from the object may be varied through filters and compared with a
constant light source.
Orifice
An opening of controlled size used to measure or control the flow of
gases.
Oven, Drying
A furnace or oven for drying moulds or cores.
P1
In production, acceptable quality level.
P2
In production, lot tolerance.
66
Patching
Repair of a furnace lining or repair of a mould core.
Peel
Free removal of burnt moulding sand from casting.
Pencil Core
A core projecting to the centre of a blind riser allowing atmospheric
pressure to force out feed metal.
Pour
Discharge of molten metal from the ladle into the mould.
Pouring
Filling the mould with molten metal. Transferring the molten metal from
the furnace to the ladle, ladle to ladle, or ladle into the moulds.
Pouring Basin
Reservoir on top of the mould to receive the molten metal.
Pouring Basin, Cup
Located on top of sprue or down gate.
Pouring Cup
The flared section of the top of the downsprue. It can be shaped by hand
in the cope, or be a shaped part of the pattern used to form the downsprue; or
may be baked core cup placed on the top of the cope over the downsprue.
Pouring Device
Mechanically operated device with a ladle set for controlling the pouring
operation.
Pouring Ladle
Ladle used to pour metal into the mould.
Pouring Off
The task of ladling, or mechanically pouring, of the molten metal into
the moulds, forming the casting.
Production Foundry
Highly mechanized foundry for manufacturing large quantities of
repetitive castings.
67
Production Welding
Any welding carried out during manufacturing before final delivery to
the purchaser. This includes joint welding of casting and finishing welding.
Purging
Elimination of air and other undesirable gases from furnaces or heating
boxes.
Pyrometallurgy
Chemical metallurgical process dependent upon heat.
Pyrometer
An instrument for determining elevated temperatures.
Pyrometric Cone
A slender trihedral pyramid made of a mixture of minerals similar in
composition to that of clay or other refractory being tested. Each cone is
assigned a number indicating its fusion temperature.
Pyrometric Cone Equivalent (PCE)
An index of refractoriness obtained by heating on a time-temperature
schedule a cone of the sample material and a series of standardized pyrometric
cones of increasing refractoriness.
Pyrometry
A method of measuring temperature with any type of temperature
indicating instruments.
Rare Earth (RE)
Any of a group of 15 similar metals with atomic numbers 57 to 71. Also
rare earth element, rare earth metal, lanthanide series, uncommon metals,
Misch metal.
Rare Gases
These include helium, argon, neon, krypton, xenon and radon.
Re-bonding
Term usually employed in reference to adding new bonding material to
used moulding sand so that it can be used again to produce moulds.
Receiving Ladle
A ladle placed in front of the cupola into which all metal is tapped. It
acts as a mixer and reservoir and to smooth out metal flow to the pouring area.
68
Refractory
Heat-resistant material, usually non-metallic, used for furnace linings
etc. The quality of resisting heat. Material usually made of ceramics, which is
resistant to high temperatures, molten metal, and slag attack.
Reject Rate
Ratio of the number of parts scrapped to the total number of parts
manufactured, expressed as a percentage.
Relief Sprue
The term usually refers to a second sprue at opposite end of the runner to
relieve pressure created during pouring operation.
Repair Welding
Any welding carried out after delivery to the end user, i.e., after the
casting has been in service.
Returns
Metal in the form of gates, sprues, risers or defective castings which are
put back into the melting cycle.
Reverberatory Furnace
Melting unit with a roof arranged to deflect the flame and heat toward
the hearth on which the metal to be melted rests.
Revert
Recycled sprues, gates, risers, defective castings and machine chips.
Reynolds Numbers
Used in hydraulics and in casting gating theory. A dimensionless value
(dynamic viscosity / density) describing the fairly sudden shift of flow from
laminar to turbulent. Re > 2000 represents turbulent flow. Laminar flow is
seldom experienced in runner and gating systems.
Riddle
Hand or power-operated device for removing large particles of sand or
foreign material from foundry sand.
Rigging
Gates, risers, loose pieces, etc., needed on the pattern to produce a sound
casting.
69
Riser
A reservoir of molten metal that the casting can draw from to offset the
shrinkage that is taking place as the metal solidifies.
Runner
Trapezoidal shaped piece that runs horizontally to the mould cavity and
connects the Sprue base to the gate(s).
Runner Box
System into which molten metal is introduced.
Sand Blast
Sand driven by a blast of compressed air (or steam). It is used to clean
castings, to cut, polish, or decorate glass or other hard substances, and also to
clean building fronts, etc.
Sand Casting
Metal castings produced in sand moulds.
Scarfing
Cutting off surface projections such as gates and risers from casting by
means of gas torch.
Scrap
Any scrap metal melted, usually with suitable additions, to produce
castings.
Scrap Metal
Metal to be re-melted; includes scrapped machinery fabricated items
such as rail or structural steel and rejected castings (metal to be re-melted,
castings that have to be re-melted).
Shank
The handle attached to a small ladle.
Silica Brick
Refractory material of ganister, bonded with hydrated lime, and fired at
high temperature.
Sodium Silicate (CO2 Process)
Moulding sand is mixed with sodium silicate and the mould is gassed
with carbon dioxide gas to produce a hard mould or core.
70
Solidification
Process of metal (or alloy) changing from the liquid to the solid state.
Spout
A trough through which the metal flows from the furnace to the ladle.
Sprue
A vertical passageway that takes the molten metal from the pouring
basin to the runner.
Spruing
Removing gates and risers from castings after the metal has solidified.
Tap
To withdraw a molten charge from the melting unit.
Tap Hole
Opening in a furnace through which molten metal is tapped into the
ladle.
Teapot Ladle
Ladle with external spout wherein the molten metal is poured from the
bottom rather than from the top.
Temperature
Degree of warmth or coldness in relation to an arbitrary zero measured
on one or more of accepted scales, as Centigrade, Fahrenheit, etc.
Temperature, Holding
Temperature above the critical phase transformation range at which
castings are held as a part of the heat treatment cycle. The temperature
maintained when metal is held in a furnace, usually prior to pouring.
Temperature, Pouring
The temperature of the metal as it is poured into the mould.
Tensile Strength (Ultimate Tensile Strength, UTS)
A measure of the amount of mechanical stress a material can withstand
before it fractures. Measured in Pounds per Square Inch (PSI) , or thousands of
pounds per square inch (KSI).
Test Bar
Standard specimen bar designed to permit determination of mechanical
properties of the metal from which it was poured.
71
Test Lug
A lug cast as a part of the casting and later removed for testing purposes.
Thermocouple
A device for measuring temperatures by the use of two dissimilar metals
in contact; the junction of these metals gives rise to a measurable electrical
potential which varies with the temperature of the junction. Thermocouples are
used to operate temperature indicators or heat controls.
Transfer Ladle
A ladle that may be supported on a monorail or carried in a shank and
used to transfer metal from the melting furnace to the holding furnace or from
furnace to pouring ladles.
Transformation (Temperature) Range
The critical temperature at which a change in phase occurs.
Vent
A pathway provided in the mould to allow gas to escape.
Cope
The top half of a horizontally parted mould.
Core
A separately made sand shape, usually baked or chemically bonded,
inserted in a mould to form the inside of a casting or parts which could not
otherwise be shaped by the pattern.
Drag
The bottom half of a horizontally parted mould
Gate
The connection to the casting cavity through which the molten metal
flows.
Parting Line
The line along which a pattern or core box is divided or the dividing line
72
73
High-Alloy Steel
Ferrous alloy with more than 12 weight percent of non-carbon
additions.
Inert Gas
A gas that will not support combustion or sustain any chemical reaction;
e.g., argon or helium.
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is
a metal in the first transition series. It is by mass the most common element on
Earth, forming much of Earth's outer and inner core. Melting point: 1,538 C
Manganese Briquettes
Crushed ferromanganese bonded with a special refractory in briquette form, and
containing 2-lb metallic manganese and -lb metallic silicon.
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the
atomic number 25. It is found as a free element in nature, and in many
minerals. Melting point: 1,246 C
Mild Steel
Plain carbon steel of about 0.25% carbon or less.
Mineral
Natural inorganic substance which is either definite in chemical
composition or physical characteristics or any chemical element or compound
occurring naturally as a product of inorganic processes.
Misch-metal
Alloy of rare-earth metals containing about 50% cerium and 50% lanthanum,
neodymium, and similar elements.
74
Monel
A high nickel alloy, approximately 67% Ni, 28% Cu, the balance Fe, Mn,
Si and other elements. Monel metal is resistant to corrosion and is widely used
to resist the action of acids.
Molybdenum
A metal used widely in alloying of other metals. It is used as hardening
element for steel, and for die-casting dies. The melting point is 2,620C
(4,748F), and the atomic number is 42.
Mother Metal
The molten alloy just before final solidification and freezing out of the solid.
Nichrome
Oxidation-resistant alloy 65% Ni, 20% Fe, and 15% Cr.
Nickel
An element used for alloying iron and steel as well as nonferrous metals;
melting point 1455C (2651F). Nickel is also a base metal for many casting
alloys resistant to corrosion and high temperature oxidation. Nickels chemical
symbol is Ni. Its formula weight is 58.69 and the specific gravity is 8.90, and
nickels melting point 1,452C.
Niobium
Niobium, formerly columbium, is a chemical element with the symbol Nb
and atomic number 41. It is a soft, grey, ductile transition metal, which is often
found in the pyrochlore mineral, the main commercial source for niobium, and
columbite. Melting point: 2,469 C
Nitrogen
Nitrogen, symbol N, is the chemical element of atomic number seven. At
room temperature, it is a gas of diatomic molecules and is colourless and
75
76
Selenium
A metalloid melting 220C (428F) added to stainless steel
to improve machinability
Stainless Steel
A wide range of steels containing chromium or chromium and nickel,
exhibiting high resistance to corrosion
Steel
An alloy of iron and carbon, containing no more than 1.74% carbon. It
must be malleable at some temperature while in the as-cast state.
Sulphur
A non-metallic chemical element, with a melting point of
444C (831.2F) occurring as an undesirable tramp (trace)
element in most ferrous alloys.
Super alloy
An alloy developed for very high temperature use where relatively high
stresses are encountered and where oxidation resistance is needed.
Ternary Alloy
An alloy that contains three principal elements.
Tin
A chemical element having symbol sn, formula weight 118.70, specific
gravity 7.31, and melting point 231.85C.
Titanium
A white metallic element, melting point 1660C (3020F), having a high
strength-to-weight ratio; useful in aircraft parts.
77
Tungsten
Steel-gray, metallic element, mp 3380C (6116F) used for electric lamp
filament, x-ray tube target, and as alloy element in high-speed steels.
Vanadium
A white, hard, metallic element, mp 1800C (3272F), used as an alloy in
iron and steel; a powerful carbide stabilizer and deoxidizer.
Virgin Metal (Primary Metal)
Metal extracted directly from the ore; not previously used.
Zinc
A chemical element having symbol Zn, formula weigh 65.38, specific
gravity 7.140, and melting point 419.4C.
Zirconium
Silvery-white, metallic element, mp 1,860C (3,380F), a powerful
deoxidizer when added to molten steel.
CHAPTER 4
CASE STUDY
Product -Castings
Materials - ASTM A216 WCB
ASTM A351 CK3MCuN
78
Problem:
Crack in castings.
4.1 PROBLEM SOLVING TECHNIQUES:
Techniques used for solving this problem are Statistical Quality
Control (SQC) and Six Sigma.
4.1.1 STATISTICAL QUALITY CONTROL
Statistical Quality Control (SQC) is the term used to describe the set of
statistical tools used by quality professionals. SQC is used to analyze the
quality problems and solve them. Statistical quality control refers to the use of
statistical methods in the monitoring and maintaining of the quality of products
and services. All the tools of SQC are helpful in evaluating the quality of
services. SQC uses different tools to analyze quality problem.
Descriptive Statistics involves describing quality characteristics and
relationships. SPC involves inspect random sample of output from process for
characteristic. Acceptance Sampling involves batch sampling by inspection.
The Seven Basic Tools of Quality is a designation given to a fixed set of
graphical techniques identified as being most helpful in troubleshooting issues
related to quality. They are called basic because they are suitable for people
with little formal training in statistics and because they can be used to solve the
vast majority of quality-related issues. The seven tools are:
Cause-and-effect diagram (also known as the "fishbone" or Ishikawa
diagram)
Check sheet
Control chart
Histogram
Pareto chart
Scatter diagram
79
previous phases.
Phase I: Define
The problem can be defined as Cracks and other defects found in castings.
Phase II&III: Measure and Analyse
FIGURE 4.1.2.1.1 FISHBONE DIAGRAM FOR DEFECTS IN
CASTING
Status
RT NSD%
K7748
K7837
K7668
K7715
Rejection
Rejection
Rejection
OK
50%
50%
75%
100%
Weld%
1.87%
82
Chemical
Compositio
n
OK
OK
OK
OK
Mechanical
properties
OK
OK
OK
OK
K7502
K7378
K7432
OK
Rejection
OK
100%
0.82%
100%
0.89%
OK
OK
OK
OK
OK
OK
Status
RT NSD%
K7868
K7906
K7629
K7643
K7513
K7521
OK
OK
Rejection
Rejection
Rejection
R OK
100%
100%
50%
50%
50%
100%
Weld%
0.93%
Chemical
compositio
n
OK
OK
OK
OK
OK
OK
Mechanical
properties
OK
OK
OK
OK
OK
OK
Status
RT NSD%
Weld%
Mechanical
properties
3.22%
Chemical
compositio
n
OK
K 6739
OK
78.90%
K6740
OK
81.50%
1.78%
OK
OK
K6741
OK
82.90%
5.11%
OK
OK
83
OK
Figure
4.1.2.1.2 RT
% of WCB
castings with
Scraps &
Scraps +
Returns
Heat
No:
Statu
s
RT
NSD%
Weld
%
Chemical
compositi
on
K674
8
K675
1
K675
2
K675
6
K676
1
K676
2
K676
4
K676
5
K676
6
OK
63%
OK
OK
81.50
%
75.30
%
89.50
%
63.20
%
73.70
%
48.60
%
94.60
%
83.80
%
15.17
%
1.66%
Mechanic
al
Propertie
s
OK
OK
OK
9.66%
OK
OK
0.52%
OK
OK
3.67%
OK
OK
3.18%
OK
OK
3.54%
OK
OK
0.78%
OK
OK
1.81%
OK
OK
OK
OK
OK
OK
OK
OK
OK
NSD
84
85
Table 4.1.2.1.5 Cost analysis of CK3MCuN Castings with Scraps & Scraps
+ Returns
Scraps
Heat No
K7378
K7432
K7502
K7668
K7715
K7748
K7837
Rate
409.09
413.59
413.71
413.4
406.22
406.75
416.35
Metal cost / Kg
Scrap + Returns
Heat No
Rate
K7513
408.99
K7521
401.01
K7629
364.62
K7643
392.53
K7868
390.45
K7906
391.27
Table 4.1.2.1.6 Cost analysis of WCB Castings with Scraps & Scraps +
Returns
Scraps
Metal cost / Kg
Scraps + Returns
86
Heat. No
K6739
K6740
K6741
Rate
Heat .No
46.66 K6756
46 K6761
44.3 K6762
K6751
K6764
K6765
K6766
K6748
K6752
Rate
40.09
36.91
37.53
41.6
42.08
42.49
38.75
42.87
40.12
CHAPTER 5
METHODS OF MEASURING THE DEFECTS
5.1 INSPECTION OF CASTING:
5.1.1 PROCESS INSPECTION
Inspection which is done while parts are being processed. This is helpful
to detect defects at the start and allow the corrections. This is a preventive act.
5.1.2 VISUAL INSPECTION
It is the simplest and fastest inspectional methods. Most commonly
employed. Usually good to check surface defects, but fails to identify internal
defects.
5.1.3 DIMENSIONAL INSPECTION
Before casting is to be machined dimensional inspection is done.
87
Castings are placed on surface plate or surface table with angle - measuring
instruments. Various measuring instruments are employed for a first set of
castings, so as to standardize subsequent castings.
5.2 TESTING METHODS
5.2.1 PRESSURE TESTING:
Casting that is used for containing or conveying liquids, gases, such
type are subjected to pressure testing. It is tested for any leaks through their
walls. Leaks may be detected by submerging the complete casting under water
for gas pressures or by visual inspection by liquid pressures.
5.2.2 DESTRUCTIVE TESTING:
This test is done causing harm to the casting i.e. by destroying it. Various
tests include fatigue tests, compression tests, creep tests etc.
90
91
Concrete
Steel
Lead
Tungsten
Uranium
Iridium192 44.5
12.7
4.8
3.3
2.8
Cobalt-60
21.6
12.5
7.9
6.9
60.5
92
5.2.3.3Ultrasonic Testing:
Ultrasonic Testing (UT) uses high frequency sound energy to conduct
examinations and make measurements. Ultrasonic testing is based on
piezoelectric effect which converts electrical energy to mechanical energy thus
generating ultrasonic waves .Ultrasonic waves are generated when a high
frequency alternating current of about a million times per second is impressed
across the forces of piezoelectric materials like quartz crystal. The crystal
expands in full half of the cycle and contracts when the electric field is
increased, thus producing mechanical vibrations.
When there is a discontinuity (such as a crack) in the wave path, part of
the energy will be reflected back from the flaw surface .The reflected wave
signal is transformed into an electrical signal by the transducer and is
93
displayed on a screen .In the applet below, the reflected signal strength is
displayed versus the time from signal generation to when an echo was
received. Signal travel time can be directly related to the distance that the
signal travelled .From the signal, information about the reflector location, size,
orientation and other features can be found.
94
95
96
CHAPTER 6
AVOIDING THE DEFECTS IN CASTING
Metallic Projections
Care in pattern making, moulding and core making;
Control of their dimensions;
Care in core setting and mould assembly.
Cavities
Make adequate provision for evacuation of air from the mould cavity.
Increase permeability of mould and cores;
Avoid improper gating systems;
Assure adequate baking of dry sand moulds;
Control moisture levels in green sand moulding;
Increase static pressure by enlarging runner height.
Discontinuities
Care in shakeout and in handling the casting while it is still hot;
Sufficient cooling of the casting in the mould;
For metallic moulds; delay knockout, assure mould alignment, use
ejector pins.
Defective Surface
Flow marks: On the surfaces of otherwise sound castings, the
defect appears as lines which trace the flow of the streams of
liquid metal.
Possible Causes Oxide films which lodge at the surface, partially
marking the paths of metal flow through the mould.
97
Remedies:
Increase mould temperature;
Lower the pouring temperature;
Modify gate size and location (for permanent moulding by gravity or
low pressure);
Tilt the mould during pouring;
In die casting: vapour blast or sand blast mould surfaces which are
perpendicular, or nearly perpendicular, to the mould parting line.
Incomplete Casting
Have sufficient metal in the ladle to fill the mould;
Check the gating system;
Instruct pouring crew and supervise pouring practice.
Incorrect Dimensions or Shape
Assure adequate rigidity of patterns and pattern plates, especially when
squeeze pressures are being increased.
Inclusions or Structural Anomalies
Assure that charge materials are clean; eliminate foreign metals;
Use small pieces of alloying material and master alloys in making up the
charge;
Be sure that the bath is hot enough when making the additions;
Do not make addition to near to the time of pouring;
98
For nonferrous alloys, protect cast iron crucibles with a suitable wash
coating.
99
ANNEXURE
VISION
Safe, Environmentally friendly and dependable World Class Steel
Foundry manufacturing machined valve castings for severe and critical
application in complex materials.
MISSION
Continually delight the customer with quality and on-time delivery for
forging long term sustainable win-win partnerships.
Continually improvise effectiveness of management to strengthen the
system and focus people on data driven decision analysis and problem
solving.
Continuously invest and develop people with core skills to improve
competency and organizational involvement.
Enhance capabilities and invest in new technology to improve
productivity and supply finished products for severe and critical
applications.
2011
201
0
ASTM Standard
Category
CARBON STEEL
Standard
Grade
ASTM A216
WCB, WCC
ASTM A352
LCB, LCC
DIN 10213-2
1.0619, 1.0625
DIN 10213-3
1.1131, 1.6220
ASTM A352
ASTM A743
ASTM A487
ASTM A148
90-60, 120-95
DIN 10213-2
DIN 10213-3
1.6982
CF10
STAINLESS STEEL
CK3MCuN
1.4308, 1.4309
DIN 10213-4
ASTM A890
101
GA
1.4552
GL
1A (CD4MCu)
CH
1B
PLU
4A (CD3MN)
CO
5A (CE5MN)
BU
1.4470
Inconel CW6MC, Cu5MCuC
ASTM A494
Val
1.4408, 1.4409
6A (CD3MWCuN)
NICKEL ALLOY
200
6
ASTM A351
DIN 10213-4
200
7
CA40
DUPLEX
200
8
ASTM A217
ALLOY STEEL
200
9
Monel M35-1
ANGLE
Body
BALL
Y-GLOBE
Body
PROCESS FLOWCHART
102
103
104
Packing and
Despatch
105
ORGANIZATIONAL STRUCTURE
MD
JMD
AMD
Purchase &
Admin
Pattern
shop incharge
HR (ADMININISTRATION)
Moulding
& Process
control in
-charges
Melting &
Fettling Incharges
HR (MATERIALS)
Quality
Control In
charge
Packing &
Despatch
Incharge
Stores
Maintenance
Mechanic
al
Electrical
Producti
on
Incharge
Melting
Incharge
106
Fettling
Incharge
REFERENCES:
www.arunasteel.com, Official website of Aruna alloy steels private limited,
Madurai.
www.steel.nic.in, Ministry of Steel, Government of India.
Casting Technology and Cast Alloys, A.K.Chakrabarti, 2005 PHI Learning
Private limited.
26th Annual SEEANZ Conference Proceedings Paper.
Richard B.Chase, Operations Management for Competitive Advantage
Ninth Edition, Tata McGraw-Hill
NareshK.Malhotra, Marketing Research Fifth Edition, Pearson Education
107