Chemically bonded phosphate ceramics for stabilization and solidification of mixed waste
Chemically Bonded Defects Panel - … · Chemically Bonded Defects Panel ... • Common in sharp...
Transcript of Chemically Bonded Defects Panel - … · Chemically Bonded Defects Panel ... • Common in sharp...
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Chemically Bonded
Defects Panel
Randal Campbell – HA International
Giuseppe Iorio – Naval Surface Warfare Center
Joe Muniza – ASK Chemicals
Mitchell Patterson – HA International
Ayax Rangel – HA International
Ralph Showman – ASK Chemicals
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
What’s “Special” about
Chemically Bonded Molds/Cores
• Sand coated w/ binder to create a
resin bridge
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Chemical Binder Types
• In-organic
– Silicates
• Organic
– Phenolic Urethane
– Furan
– Acrylic / Epoxy
– Ester-cured Phenolic
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Production Methods
• Hot / Warm box– Heat cured
• Coldbox– Gas catalyzed
• Nobake– Liquid catalyzed
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
How does the chemical binder
relate to casting defects?
• Binder cure mechanisms– Production method
• Binder decomposition– Decomposition products
– Decomposition mechanism
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Defects Related to Chemical
Binders• Erosion
• Veining
• Scabbing
• Penetration
• Warpage
• Blows
• Gas porosity
• Nitrogen fissures
• Hot tears
• Lustrous carbon
• Flake skin
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Erosion
What is it?
• A projection of metal
outside the desired
shape and into the
molding material
where the core sand
was washed away
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Erosion
Causes
• Insufficient sand
cohesion
• Poor compaction
• Poor gating design
• Aggregate insufficient
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
ErosionPotential Solutions
• Increase binder level
• Use binder with higher hot strength
• Improve compaction – harder, more uniform ramming
• Use a refractory coating / more resistant refractory
• Modify aggregate – in total or facing problem area
• Re-design the gating system
• Use ceramic gates or strainer cores
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Background• Casting is a process which carries risk of
failure occurrence during all the process of
accomplishment of the finished product
• The correct identification of the casting
defect at the initial stage is essential for
taking remedial actions
• This presentation summarizes casting
defects involved with various casting
processes
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Lustrous carbon defects
What is it?
• Lustrous carbon forms
on inert surfaces
through thermal
decomposition of
hydrocarbon-bearing
gases in reducing
atmospheres above
650°C.
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Lustrous carbon defects
What is it?
• Lustrous carbon is
deposited as a film on the
silica grains of the mould.
Relatively thick layers of
lustrous carbon film can
result from the gas
pressure which develops,
particularly when
deposited on core
sections
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Possible Causes
• Resin-bonded sand
• Lustrous carbon producing capacity of the
core binder too high
• Insufficient venting of core gases.
• Gating and pouring practice
• Too much turbulence, leading to inclusion of
lustrous carbon
• Pouring temperature too low
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Metal Penetration
What is it?
• A projection of metal
outside the desired
shape and into the
molding material
• AKA burn-In, fuzz, etc
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Metal Penetration
Causes
• Poor sand compaction
• Excessive binder
• Refractory failure
• Low surface tension
alloy
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Metal Penetration
Potential Solutions
• Modify compaction method
• Lengthen work time
• Increase bench life, or blow cores within bench life
• Decrease binder
• Choose alternate binder
• Use a refractory coating
• Modify aggregate
• Reduce pouring temperature
• Modify alloy
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Veining
What is it?
• An expansion defect
caused by fissures in
the core / mold
• Lines of extra metal
that look like veins
appear on the surface
of the casting
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
VeiningCauses
• Mainly related to aggregate expansion
• Binder thermal properties play a role in veining
• Expansion exceeding the deformability and ultimately
lessening core strength
• Common in sharp angles and curve shapes
Stress caused by
sand expansion
Sand grains Veining
Damaged section
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Veining
Potential Solutions
• Aggregate selection
• Sand additives
• Binder system
• Right level of compaction
• Pouring temperature
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Gas Defects
What is it?
• Gases dissolved in
the metal are expelled
during solidification
• External gas pressure
creates a “bubble”
and the metal
solidifies around it.
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Gas Defects
Causes
• Moisture / Water
• High LOI
• Lack of Venting
• Low pouring temp
• N2 content of binder
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Gas Defects
Potential Solutions
• Control Moisture in sand and in compressed air
• Optimized binder type
• Optimized binder levels
• Titanium additions 0.02 – 0.04%
• Optimized venting practices
• Optimized metal pour temperature
• Desiccant dryers on Part II
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Metallurgical Surface Defects
10x
100x 100x
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Defect Causes
• The sand mold is very insulating and casting
temperature remains high for an extended time
• Decomposition of the organic binder creates an
atmosphere rich in CO with some N
• This could be described as “heat treatment”
• Shakeout time determines casting temperature
and “quench”
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Defect Prevention
• Control gas composition
– Binder type
– Additives
– Venting
• Control “quench”
– Shakeout time & temp
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
Urethane Acid Cured Alkaline Phenolic Shell
Core Float/Shift in Casting 4 2 2 1
Core Warpage 3 2 4 1
Gas Blow 4 2 1 3
Hot Tears 2 1 3 4
Erosion 3 4 2 1
Burn In (Poor Density) 2 3 3 1
Lustrous Carbon 4 1 1 3
Veining 3 2 1 3
Urethane Acid Cured Alkaline Phenolic Shell
Nitrogen Sulfur Pick-Up
Sintering (salt build-
up) Nitrogen
Blows (uncured
center)
Blows (uncured
center)
1: Least Susceptible - 4: Most Susceptible
Defect Potential by Binder System
Defects Unique to Binder Chemistry
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
QUESTIONS???
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
For additional information, please
contact:
AFS Sand Casting ConferenceOctober 20-22, 2014 – Indianapolis, IN USA
InstructionsSUBMISSION:
All PowerPoint Presentations are due at
AFS by September 13, 2013
Submit to [email protected]
Or by FTP Site: http://www.afsinc.net/uploadsite/index.asp
Username: consultant
Password: safe