Cement Industry Technical Bulletin
Originally printed in WORLD CEMENT MAGAZINE, March 2010
Initial Heat Treatment and Cleaning
Castings are often annealed or normalized before cleaning. Cleaning consists of
removing fins, bumps, riser pads, in-gate stubs, etc. and blasting a second time with
abrasive shot to remove new scale and processing spatter.
Final Heat Treatment
Final heat treatment changes the molecular structure of the casting to improve its
mechanical properties. It normally increases the hardness, strength and toughness of
the casting. Castings of equal chemical composition can be given different properties by changing the heat treating process.
Crusher mantle coming out of heat
treating oven.
Machining
Many castings require machining to provide proper fit and surface finish. Dimensional changes and distortions can occur during final heat treatment so most castings
are machined after final heat treatment. Some castings, such as alloy white iron castings, are normally machined in a softened state and again after final heat treatment.
Creating Wear
Resistant Castings
An understanding of the casting process can bring
benefits to cement plant operations.
By Scott McNiven, Product Engineering Manager, Columbia Steel Casting Co., Inc.
Computer modeling of a grinding roller.
BASIC OPERATIONS TO PRODUCE
WEAR RESISTANT CASTINGS:
A FULL SERVICE FOUNDRY WITH TRAINED
SALES REPRESENTATIVES AND SPECIALIZED
Designing
PRODUCT ENGINEERS CAN OFTEN WORK
Detailing
WITH CEMENT PLANT PERSONNEL TO
DEVELOP SUPERIOR PARTS THROUGH
At left: Machining a roller mill tire.
Above: Ultrasonic inspection of a
machined casting.
DESIGN AND MATERIAL CHANGES.
Final Inspection and Shipping
Depending on the part, final inspection can consist of various procedures. In addition to visual and dimensional inspection, castings can be non-destructively tested.
Magnetic particle inspection and dye penetrant inspection can detect cracks
and tears that may not be obvious to the naked eye. Ultrasonic and radiographic
inspection can detect internal defects such as cracks and shrinkage discontinuities.
Destructive testing is not normally required but can be done on sample castings
if warranted.
Parts that pass final inspection are prepared for shipping and shipped to the
customer. Foundry representatives should follow-up on with the cement plant to
verify that the parts fit properly and perform well.
Conclusion
Properly engineered and manufactured replacement parts should provide long,
trouble free service for cement plants and good foundries provide quality parts by
controlling their manufacturing process. Furthermore, a full service foundry with
trained sales representatives and specialized product engineers can often work with
cement plant personnel to develop superior parts through design and
material changes.
Patternmaking
Coremaking
Molding
Melting
Pouring
Shakeout
Riser and Gate Removal
Initial Heat Treatment
Machining
Inspection
www.columbiasteel.com
© 2010 Columbia Steel Casting Co., Inc. All rights reserved. Columbia, Columbia Steel, and the C logo
are trademarks of Columbia Steel Casting Co., Inc.
CM20-10
Shipping
Wear resistant and heat resistant castings, also known as replacement wear parts, are used
in several areas of cement plants — from the quarry to the final grinding.
What follows is an overview of the process that a foundry follows to produce castings. Full service foundries are capable of providing their customers value-added services, such as engineering consultation, wear studies, material selection, and part design
and customization. Better understanding the process to produce wear resistant castings,
can benefit cement plant personnel through their understanding of how foundries can
optimize parts to better meet the specific needs of cement plant applications.
Foundry Services
Foundries often provide services beyond simply producing castings. Ideally, trained sales
professionals and engineers work with cement plant personnel to provide parts that perform better and last longer. A properly designed wear part will fit properly, improve the
efficiency of the equipment in which it is used and provide a long service life.
Before a foundry can make recommendations it is important to determine how the part
fits in the machine, its relationship to other parts and of course its purpose and service
conditions. Questions must be asked. For instance, is the part subjected to severe impact
or just abrasion? Is there a history of part breakage or rapid wear? Are there fit problems?
Depending on the part and application, it may be possible for the foundry to make
design and material recommendations based on known information. In other cases it
may be necessary to do wear studies and analyze existing parts. Often it is necessary to
measure existing parts. Sometimes it is necessary to go inside the machine to get fit and
clearance information.
Cement Industry Technical Bulletin
Mechanical Properties of Typical Alloys
Alloy
Manganese steels
High strength steels
Chromium-molybdenum steels
Alloy white irons
Heat resistant steels
Hardness (HB)
228*
260 - 512
302 - 402*
555 - 713
180
Toughness & Ductility
Very good
Fair to good
Poor to fair
Very poor
Poor
Pouring
Machineability
Poor
Poor to good
Poor to fair
Very poor
Fair
In the casting process, molten metal is
poured from a ladle into a pouring cup that
sits atop the mold. The optimum pouring temperature varies with the chemical
composition of the metal being poured and
must be tightly controlled. Metal goes
down the sprue (downspout), into runners
and through gates into the mold cavity
created by the pattern (which was removed
before the mold was closed and prepared
for pouring). Risers are reservoirs of excess metal that feed heavy sections of the
casting. They are filled during the pouring
process and feed molten metal into the
casting as it solidifies and shrinks. Most
castings would not be solid without the use
of risers.
Weldability
Good
Poor to good
Not weldable
Not weldable
Poor to good
*The hardness shown for manganese steel is “as heat treated” — manganese steel work-hardens significantly during service.
**Chromium-molybdenum-vanadium tool steel has a hardness of 555HB.
Design and Material Selection
Two common methods by which a foundry
can improve the performance and life of a
replacement wear part are improving the
part design and pouring it out of a superior material. Sometimes the foundry can
improve the performance of a part simply
by changing the manufacturing or heat
treating process.
Often the life of a part can be improved by simply adding material to the
high wear areas. Sometimes it is possible
to move material from a non wear area to
a high wear area without increasing the
weight of the part, thus keeping the price
down and reducing throw-away weight.
Part life can often be improved by
changing the chemical composition or
heat treating process. Every alloy has its
benefits and detriments. Selecting the
right alloy for a wear part is a balancing
act between properties such as toughness
and hardness. Toughness is the ability
of a material to withstand shock loading
without fracture. Hardness is the ability
of a material to resist indentation. As a
rule of thumb, the harder a casting is the
better it will resist wear. In general, hard
parts are not tough and tough parts are not
hard. Other properties to consider include
heat resistance, ductility, machineability
and weldability. Some materials cannot
be drilled, tapped or accurately machined.
Some materials cannot be welded or hardfaced without risk of cracking.
Alloy white irons are extremely hard
and provide excellent abrasion resistance
but they have limited toughness. Manganese steels are tough but are normally
limited to applications where impact
loading will allow it to work-harden. High
strength steels are more machineable than
most wear resistant steels. Air-hardened
chromium-molybdenum steels are less
prone to cracking and distortion in processing than water-quenched steels. Heat
resistant steels are resistant to oxidation
and hot gas corrosion and have superior
mechanical properties at elevated temperatures but they do not have good abrasion
resistance.
The properties of steels and irons can
be varied by changes in chemistry and
heat treatment. This is especially true for
high strength steels, wherein a wide range
of properties can be obtained by varying
the chemical composition and tempering
temperatures in the heat treatment process.
A foundry with a knowledgeable
engineering and metallurgical staff can, by
working with the customer’s maintenance
and operations personnel, recommend the
optimum part design and material selection. Furthermore, solidification software
and computerized equipment and controls
can help a modern foundry manufacture a
quality casting that will provide excellent
service.
Manufacturing Process
Castings are created by pouring molten metal into molds and allowing it to
solidify. It is important for the casting’s
designer to be familiar with foundry processes and material options.
The basic operations of producing
steel or iron castings using the sand mold-
ing process include designing, detailing,
patternmaking, coremaking, molding,
melting, pouring, shakeout, riser and
gate removal, initial heat treatment,
cleaning, final heat treatment, machining, inspection and shipping. It should
be noted that manganese steel castings
receive only one stage of heat treatment.
The designing operation, including
material selection has been discussed
previously. The remaining operations
are discussed next.
Detailing
Product engineers create part drawings
for use by the pattern shop, machine
shop and inspection departments. The
drawings specify dimensions, tolerances,
finish allowance and allowable surface
roughness. Tolerance is the allowable
deviation from the specified dimension. Finish allowance is material that is
added to the pattern so that there is extra
material on the casting for machining.
The drawings can also include
notes regarding the location of cast
product information (e.g. pattern number, material code and foundry logo)
and other information such as associated
parts, special cleaning or inspection
instructions, and material specification.
Patternmaking
Patterns are reusable replicas of castings, normally made of wood or
urethane. They are slightly larger than
the castings they produce to allow for
dimensional shrinkage that occurs in the
mold during the solidification process.
Patterns have tapered sides, known as
draft that allows them to be withdrawn
from the sand mold.
Molding and Coremaking
Wooden pattern of a roller mounting frame.
Sand molding consists of placing a pattern in a box known as a flask and ramming green sand or placing chemically
Shakeout, Riser and Gate Removal
Mold being prepared for closing.
bonded sand around it. The pattern is
then removed and cores are placed in
the resultant mold. The mold normally
consists of two halves. The top half is
called the cope and the bottom half is
called the drag. The halves are created
seperately then combined in preperation
for pouring.
Cores are placed in molds to create
holes and pockets and to accommodate
backdraft situations. Backdraft is a
condition wherein the pattern cannot be
removed without destroying the mold.
Cores are made of chemically bonded
sand that breaks down during the solidification process to allow easy removal.
Melting
Most ferrous foundries create molten
metal in electric arc furnaces or electric
induction furnaces. In an arc furnace,
the metal charge is melted by an electric
arc from large electrodes. In induction furnaces, melting is accomplished
by the heat generated as a result of the
charge’s resistance to a current that is
induced by a magnetic field generated
by a coil. The process of pouring the
molten metal from the furnace into the
pouring ladle is called tapping.
At right: Furnace being tapped.
After the casting solidifies and cools in
the mold for a specified time (known as
the dwell time) it goes to the shakeout
department. Shakeout normally consists
of placing the mold on a vibrating grizzly
and allowing the sand to fall between the
bars of the grizzly while the casting stays
on top.
After the casting is shaken out, the
gates and risers are removed and it is blasted with abrasive shot to remove adhering
sand and scale.
Above top: Molds being poured.
Above: Casting with risers after shakeout.
Cement Industry Technical Bulletin
Mechanical Properties of Typical Alloys
Alloy
Manganese steels
High strength steels
Chromium-molybdenum steels
Alloy white irons
Heat resistant steels
Hardness (HB)
228*
260 - 512
302 - 402*
555 - 713
180
Toughness & Ductility
Very good
Fair to good
Poor to fair
Very poor
Poor
Pouring
Machineability
Poor
Poor to good
Poor to fair
Very poor
Fair
In the casting process, molten metal is
poured from a ladle into a pouring cup that
sits atop the mold. The optimum pouring temperature varies with the chemical
composition of the metal being poured and
must be tightly controlled. Metal goes
down the sprue (downspout), into runners
and through gates into the mold cavity
created by the pattern (which was removed
before the mold was closed and prepared
for pouring). Risers are reservoirs of excess metal that feed heavy sections of the
casting. They are filled during the pouring
process and feed molten metal into the
casting as it solidifies and shrinks. Most
castings would not be solid without the use
of risers.
Weldability
Good
Poor to good
Not weldable
Not weldable
Poor to good
*The hardness shown for manganese steel is “as heat treated” — manganese steel work-hardens significantly during service.
**Chromium-molybdenum-vanadium tool steel has a hardness of 555HB.
Design and Material Selection
Two common methods by which a foundry
can improve the performance and life of a
replacement wear part are improving the
part design and pouring it out of a superior material. Sometimes the foundry can
improve the performance of a part simply
by changing the manufacturing or heat
treating process.
Often the life of a part can be improved by simply adding material to the
high wear areas. Sometimes it is possible
to move material from a non wear area to
a high wear area without increasing the
weight of the part, thus keeping the price
down and reducing throw-away weight.
Part life can often be improved by
changing the chemical composition or
heat treating process. Every alloy has its
benefits and detriments. Selecting the
right alloy for a wear part is a balancing
act between properties such as toughness
and hardness. Toughness is the ability
of a material to withstand shock loading
without fracture. Hardness is the ability
of a material to resist indentation. As a
rule of thumb, the harder a casting is the
better it will resist wear. In general, hard
parts are not tough and tough parts are not
hard. Other properties to consider include
heat resistance, ductility, machineability
and weldability. Some materials cannot
be drilled, tapped or accurately machined.
Some materials cannot be welded or hardfaced without risk of cracking.
Alloy white irons are extremely hard
and provide excellent abrasion resistance
but they have limited toughness. Manganese steels are tough but are normally
limited to applications where impact
loading will allow it to work-harden. High
strength steels are more machineable than
most wear resistant steels. Air-hardened
chromium-molybdenum steels are less
prone to cracking and distortion in processing than water-quenched steels. Heat
resistant steels are resistant to oxidation
and hot gas corrosion and have superior
mechanical properties at elevated temperatures but they do not have good abrasion
resistance.
The properties of steels and irons can
be varied by changes in chemistry and
heat treatment. This is especially true for
high strength steels, wherein a wide range
of properties can be obtained by varying
the chemical composition and tempering
temperatures in the heat treatment process.
A foundry with a knowledgeable
engineering and metallurgical staff can, by
working with the customer’s maintenance
and operations personnel, recommend the
optimum part design and material selection. Furthermore, solidification software
and computerized equipment and controls
can help a modern foundry manufacture a
quality casting that will provide excellent
service.
Manufacturing Process
Castings are created by pouring molten metal into molds and allowing it to
solidify. It is important for the casting’s
designer to be familiar with foundry processes and material options.
The basic operations of producing
steel or iron castings using the sand mold-
ing process include designing, detailing,
patternmaking, coremaking, molding,
melting, pouring, shakeout, riser and
gate removal, initial heat treatment,
cleaning, final heat treatment, machining, inspection and shipping. It should
be noted that manganese steel castings
receive only one stage of heat treatment.
The designing operation, including
material selection has been discussed
previously. The remaining operations
are discussed next.
Detailing
Product engineers create part drawings
for use by the pattern shop, machine
shop and inspection departments. The
drawings specify dimensions, tolerances,
finish allowance and allowable surface
roughness. Tolerance is the allowable
deviation from the specified dimension. Finish allowance is material that is
added to the pattern so that there is extra
material on the casting for machining.
The drawings can also include
notes regarding the location of cast
product information (e.g. pattern number, material code and foundry logo)
and other information such as associated
parts, special cleaning or inspection
instructions, and material specification.
Patternmaking
Patterns are reusable replicas of castings, normally made of wood or
urethane. They are slightly larger than
the castings they produce to allow for
dimensional shrinkage that occurs in the
mold during the solidification process.
Patterns have tapered sides, known as
draft that allows them to be withdrawn
from the sand mold.
Molding and Coremaking
Wooden pattern of a roller mounting frame.
Sand molding consists of placing a pattern in a box known as a flask and ramming green sand or placing chemically
Shakeout, Riser and Gate Removal
Mold being prepared for closing.
bonded sand around it. The pattern is
then removed and cores are placed in
the resultant mold. The mold normally
consists of two halves. The top half is
called the cope and the bottom half is
called the drag. The halves are created
seperately then combined in preperation
for pouring.
Cores are placed in molds to create
holes and pockets and to accommodate
backdraft situations. Backdraft is a
condition wherein the pattern cannot be
removed without destroying the mold.
Cores are made of chemically bonded
sand that breaks down during the solidification process to allow easy removal.
Melting
Most ferrous foundries create molten
metal in electric arc furnaces or electric
induction furnaces. In an arc furnace,
the metal charge is melted by an electric
arc from large electrodes. In induction furnaces, melting is accomplished
by the heat generated as a result of the
charge’s resistance to a current that is
induced by a magnetic field generated
by a coil. The process of pouring the
molten metal from the furnace into the
pouring ladle is called tapping.
At right: Furnace being tapped.
After the casting solidifies and cools in
the mold for a specified time (known as
the dwell time) it goes to the shakeout
department. Shakeout normally consists
of placing the mold on a vibrating grizzly
and allowing the sand to fall between the
bars of the grizzly while the casting stays
on top.
After the casting is shaken out, the
gates and risers are removed and it is blasted with abrasive shot to remove adhering
sand and scale.
Above top: Molds being poured.
Above: Casting with risers after shakeout.
Cement Industry Technical Bulletin
Originally printed in WORLD CEMENT MAGAZINE, March 2010
Initial Heat Treatment and Cleaning
Castings are often annealed or normalized before cleaning. Cleaning consists of
removing fins, bumps, riser pads, in-gate stubs, etc. and blasting a second time with
abrasive shot to remove new scale and processing spatter.
Final Heat Treatment
Final heat treatment changes the molecular structure of the casting to improve its
mechanical properties. It normally increases the hardness, strength and toughness of
the casting. Castings of equal chemical composition can be given different properties by changing the heat treating process.
Crusher mantle coming out of heat
treating oven.
Machining
Many castings require machining to provide proper fit and surface finish. Dimensional changes and distortions can occur during final heat treatment so most castings
are machined after final heat treatment. Some castings, such as alloy white iron castings, are normally machined in a softened state and again after final heat treatment.
Creating Wear
Resistant Castings
An understanding of the casting process can bring
benefits to cement plant operations.
By Scott McNiven, Product Engineering Manager, Columbia Steel Casting Co., Inc.
Computer modeling of a grinding roller.
BASIC OPERATIONS TO PRODUCE
WEAR RESISTANT CASTINGS:
A FULL SERVICE FOUNDRY WITH TRAINED
SALES REPRESENTATIVES AND SPECIALIZED
Designing
PRODUCT ENGINEERS CAN OFTEN WORK
Detailing
WITH CEMENT PLANT PERSONNEL TO
DEVELOP SUPERIOR PARTS THROUGH
At left: Machining a roller mill tire.
Above: Ultrasonic inspection of a
machined casting.
DESIGN AND MATERIAL CHANGES.
Final Inspection and Shipping
Depending on the part, final inspection can consist of various procedures. In addition to visual and dimensional inspection, castings can be non-destructively tested.
Magnetic particle inspection and dye penetrant inspection can detect cracks
and tears that may not be obvious to the naked eye. Ultrasonic and radiographic
inspection can detect internal defects such as cracks and shrinkage discontinuities.
Destructive testing is not normally required but can be done on sample castings
if warranted.
Parts that pass final inspection are prepared for shipping and shipped to the
customer. Foundry representatives should follow-up on with the cement plant to
verify that the parts fit properly and perform well.
Conclusion
Properly engineered and manufactured replacement parts should provide long,
trouble free service for cement plants and good foundries provide quality parts by
controlling their manufacturing process. Furthermore, a full service foundry with
trained sales representatives and specialized product engineers can often work with
cement plant personnel to develop superior parts through design and
material changes.
Patternmaking
Coremaking
Molding
Melting
Pouring
Shakeout
Riser and Gate Removal
Initial Heat Treatment
Machining
Inspection
www.columbiasteel.com
© 2010 Columbia Steel Casting Co., Inc. All rights reserved. Columbia, Columbia Steel, and the C logo
are trademarks of Columbia Steel Casting Co., Inc.
CM20-10
Shipping
Wear resistant and heat resistant castings, also known as replacement wear parts, are used
in several areas of cement plants — from the quarry to the final grinding.
What follows is an overview of the process that a foundry follows to produce castings. Full service foundries are capable of providing their customers value-added services, such as engineering consultation, wear studies, material selection, and part design
and customization. Better understanding the process to produce wear resistant castings,
can benefit cement plant personnel through their understanding of how foundries can
optimize parts to better meet the specific needs of cement plant applications.
Foundry Services
Foundries often provide services beyond simply producing castings. Ideally, trained sales
professionals and engineers work with cement plant personnel to provide parts that perform better and last longer. A properly designed wear part will fit properly, improve the
efficiency of the equipment in which it is used and provide a long service life.
Before a foundry can make recommendations it is important to determine how the part
fits in the machine, its relationship to other parts and of course its purpose and service
conditions. Questions must be asked. For instance, is the part subjected to severe impact
or just abrasion? Is there a history of part breakage or rapid wear? Are there fit problems?
Depending on the part and application, it may be possible for the foundry to make
design and material recommendations based on known information. In other cases it
may be necessary to do wear studies and analyze existing parts. Often it is necessary to
measure existing parts. Sometimes it is necessary to go inside the machine to get fit and
clearance information.