The document discusses the types and requirements of binders used in foundry technology, classifying them into organic and inorganic types, with specific examples and properties of each. It details the role of various substances such as bentonites, fire clay, pitch, dextrin, and gelatin in enhancing the strength and performance of molds and cores during casting processes. Additionally, it covers considerations for the application of sodium silicate systems and the CO2 process for hardening molds, addressing their challenges and testing methods for effectiveness.

1. Inorganic Binders
Mr. Anirudh kumar
Scholar (M.Tech)
Department of Foundry Technology, National
Institute of Foundry and Forge Technology,
Hatia, Ranchi- 834 003,
E-mail: anirudhnifft@gmail.com

2. What is Binder ?
Binder is a chemical compound, which binds the sand grains
each other and impart strength, resistance to erosion,
breakage and degree of collapsibility of moulds and cores.
Classification of Binder’s
They may be classified as
•Organic,
•Inorganic

3. Organic binders:
Organic binders are combustible and are destroyed by heat.
Hence they contribute a degree of collapsibility to the core
and mould sand mixture. The commonly used organic
binders are core oil (0.5 to 3 %), cereal (0.5 to 2 %), resins,
plastics, pitch, dextrin, molasses, rosin, lignin, casein,
gelatin, wood flour etc.
Inorganic binders:
Inorganic binders are not combustible and may have
considerable strength at high temperatures, resistance to
erosion and relatively non-collapsables depending on their
nature. The commonly used inorganic binders in core and
mould making are Fire clay (< 2 %), bentonites (0.5 to 2 %),
silica flour (< 30 %), iron oxide, sodium silicate etc.

4. Binders
Organic Inorganic
Core oil
Cereal
Resins
Plastics
Pitch
Dextrin
Molasses
Rosin
Lignin
Casein
Gelatin
Fire clay
Bentonites
Silica flour
Iron oxide
Sodium silicate

5. Binders requirements are as follows:
• It must be readily reclaimable.
• It must be environmentally acceptable.
• It must be safe to use.
• It must have low odor at the mixing, moulding,
core making and pouring station.
• It should be no-bake, capable of providing the
long work life necessary for filling the largest
mould without the loss of mould strength.

6. •It must have sufficient hot strength to
sufficiently pour the castings weighing up
to 130 tons without premature mould/core
breakage.
•It must maintain good casting quality. The
binder should not contain significant levels
of elements that are responsible for gas
defects in steel castings, such as nitrogen
or that can alter the metallurgical
properties of the metal or promote other
casting defects.

7. • It must be cost effective. In addition
to binder costs, other costs such
as labor costs, equipment cost,
energy costs, core/mould scraps,
casting scraps, repairs, machining
and finishing costs must all be kept
low so that a good quality casting
that can be sold at a profitable,
competitive price will result.

8. BENTONITES:-
• The most commonly used inorganic binders are
BENTONITES as they produce strongest bonds in
foundry molding sands.
• Bentonites deposits are available in India in
Rajasthan and Bihar.
• Bentonites are weathered product of volcanic ash and
are soft creamy white powders.
• Bentonites are usually employed for synthetic
molding sands.
• Sodium and calcium type Bentonites give different
properties in moulding sands.

11. Bentonites

12. FIRE CLAY:-
• Fire clay is the refractory clay usually found in
coal measures.
• For use in the foundry molding sands the hard
black lumps are weathered and then pulverized.
• Fire clay particles are about 400 times as large as
compared to those of bentonite; hence the same
percentages of fire clay produce lower strengths.

14. Fireclays

15. PITCH
• Coal Tar Pitch is a black or dark-brown amorphous residue
produced by the distillation or heat treatment of coal tar. It is a black
solid at room temperature and exhibits a broad softening range
instead of a defined melting temperature. It consists of a complex
mixture of predominantly aromatic hydrocarbons.
• Binder Pitch is widely used in the Aluminium and Graphite industry
to manufacture electrodes used in their metallurgical processes.
• Epsilon Carbon has state of the art manufacturing facilities for
Binder Pitch with some of the best equipment, latest technology and
strict processes and quality control. AVH melting station is based in
a region which houses almost 70% of the volume of aluminium
manufacturing ensures better and prompt service to the customeR

17. DEXTRINE
• Yellow dextrin is manufactured by partially hydrolyzing Starch, using the dry
roasting method in the presence of a catalyst. Yellow dextrin has low
viscosity and is very sticky and hygroscopic in nature.
• Yellow Dextrin Powder helps in increasing dry strength at the same time
being completely soluble in water. Yellow Dextrin Powder is widely used as
water soluble adhesives, testifiers and as binding agents in various
industries.
• The adhesive industry uses large amounts of yellow Dextrin in the
preparation of liquid and dry adhesives. Yellow Dextrin Powder is in the form
of fine dry powder ranging from light to dark yellow and dark brown in color.

18. DEXTRINE
• Yellow dextrin serves as an excellent binding agent for sand cores in
foundry operations.
• Yellow Dextrin Powder is used to make the moulds of pattern in foundry
industry.
• Yellow Dextrin Powder eliminates air bubbles in the moulds of pattern.
• Machine labelling of tins, cartons, packages, envelopes, corrugated boxes
etc.
• Yellow Dextrin Powder is used in ceramic industry as a binder.
• Yellow Dextrin Powder is used in fireworks industry as a binder.
• Yellow Dextrin Powder is used for Carbon paper manufacturing, abrasives
and in dry distemper.
• Yellow Dextrin Powder is used by crackers manufacturer due to its adhesive
properties and also explosive character.
• Yellow Dextrin Powder is used for paper converting products for high
strength

20. MOLASSES
• Molasses, or black treacle (British, for human consumption; known as
molasses otherwise), is a viscous product resulting
from refiningsugarcane or sugar beets into sugar.
• Molasses varies by amount of sugar, method of extraction, and age of
plant. Sugarcane molasses is agreeable in taste and aroma, and is primarily
used for sweetening and flavoring foods in the United States, Canada, and
elsewhere, while sugar beet molasses is foul-smelling and unpalatable, so it
is mainly used as an animal feed additive in Europe and Russia, where it is
chiefly produced.
.

22. GELATIN
• Gelatin or gelatine (from Latin: gelatus meaning "stiff", "frozen") is a
translucent, colorless, brittle (when dry), flavorless food derived
from collagen obtained from various animal body parts. It is commonly used
as a gelling agent in food, pharmaceutical drugs, vitamin
capsules, photography, and cosmetic manufacturing
• Substances containing gelatin or functioning in a similar way are called
"gelatinous". Gelatin is an irreversibly hydrolyzed form of collagen, wherein
the hydrolysis results in the reduction of protein fibrils into smaller peptides,
which will have broad molecular weight ranges associated with physical and
chemical methods of denaturation, based on the process of hydrolysis.
• It is found in most gummy candy, as well as other products such
as marshmallows, gelatin desserts, and some ice creams, dips,
and yogurts.[1] Gelatin for recipe use comes in the form of sheets, granules,
or powder. Instant types can be added to the food as they are; others need
to be soaked in water beforehand.

24. RESIN
• In polymer chemistry and materials science, resin is a "solid or highly
viscous substance" of plant or synthetic origin that is typically convertible
into polymers.[1] They are often mixtures of organic compounds,
principally terpenes. Many plants, particularly woody plants, produce resin
in response to injury. The resin acts as a bandage protecting the plant from
invading insects and pathogens.
• Plants secrete resins and rosins for their protective benefits. They confound
a wide range of herbivores, insects, and pathogens, while the
volatile phenolic compounds may attract benefactors such as parasitoids or
predators of the herbivores that attack the plant.

26. SILICA FLOOR
• Silica flour is produced through the iron-free grinding of selected quartz
sand with a high SiO2 content in ball or vibration mills.
• The controlled particle size distribution is done via rotor-driven air
separators. This product is often used as a filler in floor systems

29. IRON OXIDE
• Iron oxides are chemical compounds composed of iron and oxygen. All
together, there are sixteen known iron oxides and oxyhydroxides.[1]
• Iron oxides and oxide-hydroxides are wide spread in nature, play an
important role in many geological and biological processes, and are widely
used by humans, e.g., as iron ores, pigments, catalysts, in thermite (see the
diagram) and hemoglobin.
• Common rust is a form of iron(III) oxide. Iron oxides are widely used as
inexpensive, durable pigments in paints, coatings and colored concretes.
Colors commonly available are in the "earthy" end of the
yellow/orange/red/brown/black range

32. ILLITE:-
•Illite is the decomposition product of micaceous materials due
to weathering.
•It is found in the natural molding sands.
•It possesses moderate shrinkage due to the loss of water.
•It does not swell in the same way as bentonite but gives
reasonable strengths.
•It has softening point of about 2500 F.
•Irreversible dehydration occurs in Illite in the temperature
range 932-1022°F.
• particles have thickness and width of 20 and 100-250mµ
respectively.

33. KAOLINITE:-
•Kaolinite is the residue of weathered granite and basalt.
•It has its composition 60% kaolinite, 30% illite, 10%
quartz.
•It possesses low shrinkage due to loss of water.
•It gets very low swelling due to water and is non gel
forming.
•It has a softening point of 3000-3100°F.
•Kaolinite particles possess thickness and width of 20
and 10-25mµ respectively.

35. Kaolinites

36. Sodium Silicate (water glass) systems
• IS 6773-1978 covers the detail specification for sodium
silicate
• Foundry sodium silicates are Meta stable solution in
which SiO2 is stabilized in solution by a combination of
Na2O and water.

37. Differences amongst various processes
using sodium silicate lie in the quality of:
• Hardener used
• Type of catalysts or other additives
• The nature of chemical reaction.
 The more commonly used silicates range
from a ratio of silica to soda of 2.0 to 3.2
 The commonly used mixtures are: a two-part
system containing a catalysts, a silicate and
a three-part system containing a catalyst, a
carbohydrate polymer and a silicate.

38. Fig. 1: Compression strength of sand mixture containing
3.0% weight ratio sodium silicate with 0.3 % of 1.51:1
ratio triacetin to diacetin catalyst.
As the ratio of silica to soda increases the rate of reaction
increases.

39. CATALYST
 The catalyst systems consist primarily of Easter.
CH3COOCH2 CH3COOCH2
 
HOCH HOCH
 
HOCH CH3COOCH2
GLYCERYL MONOACETATE GLYCERYL DIACETATE
(MONOACETIN) (DIACETIN)
CH3COOCH2 CH3COOCH2
 
CH3COOCH CH2
 
CH3COOCH2 O

GLYCERYL TRIACETATE CH2
(TRIACETIN) 
CH3COOCH2
CH3COOCH2

CH3COOCH2 DIETHYLENE GLYCOL
DIACETATE
ETHYLENE GLYCOL
DIACETATE

40.  The organic Easter will hydrolyze when reacted with a source of
hydroxyl ions.
 A typical reaction of an acetate Easter (triacetin) would proceed
according to this reaction.
OH

CH3COOCH2 CH3COOCH2 H2 H H2
 OH
-
   
CH3COOCH -------- CH3COOCH ----- 3 CH3COOH-  C – C - C ---
 Slow     
CH3COOCH2 OH  O O O
CH3COOCH2

OH
H2 H H2 H2 H H2
   H2O   
3 CH3COO- + C – C – C -------- 3 CH3COOH- + C – C – C + 3 OH-
     
OH OH OH OH OH OH

41.  As the ratio of triacetin to diacetin decreases, the rate
of reaction increases.
 The preferred catalyst level is 10-12 % based on the
weight of the binder (Fig. 2).
Fig. 2: Compression strength of sand mixtures containing various percentages
of a 2.58:1 ratio silicate with 1.0% of carbohydrate polymer and various
percentages of a 1.51:1 ratio of triacetin to diacetin catalyst

42.  Additives such as carbohydrate
polymer are usually used to
increase the knockout characteristic
and improve the tensile properties.
 The preferred reaction temperature
of the aggregate would be between
21-29 0C.

43. Various consideration for application of
self-set silicate
1. Be certain that the selection of the catalyst has a direct relation
to the Size of the mold or core applied, the type of mixing
equipment to be used, and the distance necessary to transport
the sand mixture.
2. The sand temperature should be between recommended levels
of 21 to 29°C.
- Faster for cold sand, Slower for Hot sand
3. Don’t be fooled by surface skinning of the mold or core. Always
check to certain that the system has been allowed to stand for
the recommended time interval.
4. If support rods are utilized in the mold or core, be certain that
they are at room temperature.
5.Properly check the pumps for proper delivery of the materials
into the sand mass.

44. 6. An equally important consideration is the supply of the
aggregate into the process.
7. The order of addition of the materials is absolutely essential.
It is recommended that the carbohydrate polymer be added
to the sand mixture first, then the catalyst and finally the
sodium silicate.
8. It is never recommended to mix any of the ingredients prior
to the delivery into the sand.
9. It is possible to increase the rate of reaction by placing
external conditions on the system.
10.Since the mold washes are applied to the various core
binding processes, it is essential that the system withstand
the varieties of mold washes.
11.If external heat is applied to the mold or core, be certain that
it is not exposed to prolonged heat.

45. CO2 Process
The main reason for the CO2 to be the
most widely used silicate hardener are:
 Relatively easy available
 Low cost
 Almost indefinite sound working life
 Instantaneous strip after gassing
 Good surface finish and high accuracy.

46. However, CO2 hardened moulds and
cores suffer from certain drawbacks as:
 Non-uniform strength development in the
mould/core due to difficulty in achieving uniform
gassing,
 Wastage of gas due to lack of proper control on
the foundry floor,
 Over gassed moulds/cores tend to become friable
on short storage time,
 CO2 -hardened moulds/cores have a tendency to
pick up moisture under humid conditions and
 It has poor breakdown property at knock off.

48. Principle of hardening
 The chemical reaction (for a 2 % weight ratio) occur as:
Na2O.2SiO2 (aqueous) + CO2  Na2CO3 + 2 SiO2 (aqueous) (1)
Na2O.2SiO2 (aqueous) + 2CO2 + H2O  2NaHCO3 + 2 SiO2 (aqueous) (2)
 The silica hydrogel is believed to consist of a loose network of
colloidal particles interconnected at only a few points in which
water and dissolved salts are rigidly held.
 To control the elements of gassing an apparatus was
constructed to regulate inlet gas pressure, flow rates, gassing
time and gas temperature.

49. Fig.4: Examples of systems for carbon dioxide hardening of cores and mould parts: (a)
progressive treatment using single probe, (b) cover board or hood, (c) multiple probe and
manifold, (d) hood over previously stripped cores, (e) treatment of mould after pattern
draw, (f) passage of gas through hollow pattern

50. Fig 5:Influence of carbon dioxide flow on compression strength,
illustrating reduction of strength on overgassing.

51.  For every 1 Kg of silicate, approx. 0.5-0.75 Kg
of CO2 gas required. The unreacted
mixture is reddish in color and as the gassing
progresses the radish color clears.
 Ratio of soda and silica is commonly used
1:2.1 to 1:2.5 and sp. Gravity is 1.55 to 1.71
 Sand must be dry and free from clay.
Silicate -3 to 5 % of sand is used (Fig. 3).

52. Fig. 3: Parts by weight CO2 required at 7X theoretical with various
weight ratio sodium silicates.

53. Testing of binder
 CO2 gassing depends upon various factors such as the
type of sand used, silica to soda ratio of binder,
additives added, mixing time, gas flow rate, gassing
time, temperature etc.
 Rajmahal sand develops higher gassed shear strength
compared to Allahabad sand.
 With higher ratio binder, 3 minutes mulling times gives
better strength compared to 5 minutes mulling time.

54.  With increase in silicate content in sand
mix, the as gassed compression strength
improved (Fig. 4)
Fig. 4: CO2 gassed compression strength at various
contained percentage of 2.4:1 weight ratio silicate with
various gassing ratios above theoretical.

55.  The hot compression strength of 3.5 %
silicate mix sand for various ratio of silica
and soda (Fig. 5)
Fig. 5: Hot compression strength of 96.5 % No. 1 silica sand
with various weight ratio sodium silicate mixtures.

56.  The retained strength diminishes until the
soaking temperature reaches about 535 0C
and then they increase dramatically (Fig. 6).
Fig. 6: Retained compression strength of 96.5 % No. 1 silica
sand with 3.5 % various weight ratio sodium silicate mixture.

57.  The compression strength obtained for a 2.4:1
ratio silicate, immediately and after 24 hr. in ambient
temperature and humidity condition (Fig. 7).
Fig. 7: Compression strength of 3.25 5 2.4:1 silica mixture at
various temperatures gassed at 7 with 7 lit/min.

58. 2. Ferrosilicon process
Na2O.n SiO2 + H2O  2NaOH + n SiO2 (1)
m Si + 2 NaOH + H2O  Na2O.m SiO2 +2H2  (2)
 The product is hard and spongy.
 The sand, 2 % ferrosilicon (~ 75-80 % Si and
3-3.5 m size0, sodium silicate (5 wt % of sand with
sp. Gravity 1.3 – 1.35 and mass ratio 2:1 to 2.3:1) is
commonly used
 The one major advantage of this process is less
residual moisture compare to the CO2 process is due
to exothermic reaction

59. 3. Dicalcium silicate (2 CaO. SiO2) process
 Generally 2 to 3 % dicalcium silicate is
used with 5-6 % sodium silicate and
foaming agent to make the mould/core.
 Mixing time is around 3 to 5 minutes. The
bench life was 25 to 30 minutes.
 The mass ratio of 2.3:1 to 2.8:1 sodium silicate
with sp. Gravity 1.48 to 1.5 is commonly used
in this process.

60. 4. Fluoride process
 Fluoride (sodium silico- fluoride) powder is used as
hardener.
 Hardener is used 20-25 % of the sodium silicate (5-6 %
of sand) used.
 The Fig. 8 gives the various properties of as hardened
sample while Fig. 9 compares the retained strength
with various silicate processes.

61. Fig 8: Effect of binder and
F. hardener on
compressive, shear
and retained
strength.
Fig 9: Comparison of retained
compressive strength
for various self-
hardening processes.

62. 5. Cement moulding process
Portland cement (~ 2 %) with sodium silicate
(4-5 %) and pitch or molasses (~ 1 %) is
commonly used.
 The bench life is around 15 to 20 minutes.

63. New generation of Inorganic binder (IOB)
This material is based on phosphate glasses
Advantages
 Produced cores with adequate strength
 Good surface finish
 Promise of removing the core from casting
by immersing the casting in water.

64. Limitation
 High resin level required
 Blowability of the sand into complex
shape was reduced
 Low softening temperature, restricted to
Al casting
 Storage problem (> 45 % humidity)

65. Borden chemical after several years of
intensive research and successful field trial
has developed improved inorganic binder
(IOB) system
 Can be used for both ferrous and non-
ferrous casting.
 It can replace many different core-making
methods including cold box, hotbox and
shell core.
 Water jacket cores for automotive or faucet
and valve cores for plumbing fixtures.

66. • Handling strength are twice those reported
for the original system, at half the binder
level.
• The one part IOB exhibits excellent flow
characteristics on sand. Binder levels on
sand are reduced from 4-5 % to 1.5 – 2.5 %.

67.  Fig. 10 shows strip and cold tensile as
well as scratch
Fig. 10: Mechanical properties of the cores made using silica
sand with 4 % (BOS) original binder and 2.5 % (BOS)
new binder in air assisted warm core box process.

68. • Dimensional accuracy of the casting is assured
because there is no indication of core distortion
measured over a period of weeks.
• Chemistry of this system is still totally inorganic; no
odors are generated in the core room, during casting
and at shakeout.
• This material meets the environmental regulations
and is disposable into municipal water treatment
facilities.
• The IOB system has been found as a replacement for
the organic binder, Urethane cold box (UCB) system.
• Shake out time is reduced up to 80-90 %. Bench life
of sand/binder mixture is extended.

69.  Fig. 11 shows less loss on ignition
for new IOB compared to other
processes.
Fig. 11: Loss of ignition (LOI) at 1000 0 C for cores made
with organic and new inorganic binders.

70. The IOB allows the reuse of all sand from
wasted sand mixtures, un-cast cores and
from cores after casting shakeout as shown in
Fig. 12-14.
Fig. 12: Effect of 10 % spent sand addition on tensile strength of UCB
cores made on lake sand with 1.6 % (BOS) binder. The spent
sand is washed sand from cores made with new inorganic
binder.

71. Fig. 13: Mechanical properties
of cores made using
new and UCB reclaimed
silica sands with 2.5 %
(BOS) new binders in air
assisted warm box
process.
Fig. 14: Photo showing a 10 kg
core used to produce
an automotive parts.
Removal of sand core
from this part is
complete in seconds.
 Expenses of sand reclamation based on water
application are lower than of thermal reclamation used
for organic binders.

72. NO BAKE BINDER SYSTEM

73. PHENOLIC URETHANE NO-BAKE
PEP SET
• PEP SET is arguably the most trusted name in the no-bake
marketplace. Known for its exceptional quality & highly controllable
curing reactions, PEP SET has long been the standard in no-bake
excellence. In fact, when placed on an automated production line
(roller-loop or turn table)
• PEP SET can produce fully cured molds in less than 90 seconds!
Clearly, speed, application flexibility and overall ease of use make
PEP SET ideal in satisfying any mold making requirement.

74. ADVANTAGES
• Predictable & repeatable cure times
• Superior work time / strip time ratio
• Excellent core & mold strengths
• Ease of reclamation

75. ACID CURING NO-BAKE
• The product range of brands for acid curing processes includes furan- and
phenolic-resins and serves for a wide range of applications in foundries.
ASKURAN -, CHEM-REZ- and BERANOL -resins can be applied for all
casting dimensions and metal types depending on the sand characteristic
and related analytical data.
Benefits:
• Excellent casting surface
• Controllable curing speed
• High strength
• Excellent shake-out and release

76. ESTER CURING NO-BAKE
• The no-bake solution for all metals, especially steel castings, and all mould
sizes. This ester-curing water-based no-bake is capable of being used in
most casting processes. It's water-based nature reduces material handling
requirements, as well as casting defects associated with solvent based
binder systems.
• Part II of this no-bake binder requires a liquid ester co-reactant. ASK
Chemicals offers the widest range of co-reactants allowing for all levels of
productivity. Thus, ALPHASET is ideal in most large scale casting
productions, especially in steel applications. It should be noted that as with
all Alkaline Phenolic No-Bake technology sand reclamation is more
problematic requiring greater control than other no-bake processes
• ASK Chemicals, fortunately, offers industry leading technical services to
assist you in all your casting challenges.

77. BENEFITS
Benefits:
• Wide variety of co-reactants
• Eco-friendly organic binder system
• Ideal for use in steel casting production

80. Thank You