Production of Low Cost Spectrometer Drift Correct Standards
By: Phillip Kubichka, Advisor: Kyle Metzloff
A water cooled mold and the required core boxes to create spectrometer drift correct standards were
produced at the University of Wisconsin-Platteville. Although multiple heats have occurred, samples fit
for use as spectrometer standardizing material have yet to be produced. However, the work completed
thus far has been vital in proving designs and concepts for the creation of samples. The techniques and
processes require further refinement in key areas of core binder selection and possible iron treatment to
become fully feasible.
Objectives
To develop and refine a method for producing chill cast spectrometer drift correct standards on a small
scale of 50+ samples per heat in the UW-Platteville foundry.
Introduction
Production of white iron standards on a large scale of 500+ samples per pour has been studied
previously. Multiple parties have expressed interest in a production technique capable of producing
small batch size heats allowing them to produce samples of customized chemistries.
Terminology
Pour – A single event of a mold being filled with iron. Multiple pours may take place from a heat.
Heat – A single amount molten metal in the furnace, all with the same base chemistry that may be
poured over multiple molds. Multiple pours can take place from a single heat.
Types of Reference Material
RM - Reference Material
Material whose property values are sufficiently homogeneous and well established to be used for
calibration of an apparatus
CRM - Certified Reference Material
Reference material accompanied by a certificate indicating that chemical values are tested by an
accurate and traceable method including uncertainty values
SRM – Standard Reference Material
1
Certified Reference material that also meets additional NIST-specific certification criteria and is issued
with a certificate of analysis that provides information regarding its appropriate use.
History and Past Research into Producing Reference Material
The National Bureau of Standards, currently known as the National Institute for Standards and
Technology (NIST) produced the publication 260-1 titled Preparation of NBS White Iron
Spectrochemical Standards in 1964. This document details the production process, techniques and
materials needed for producing a large scale mold of 500+ samples per pour.
The Metals Research and Development Foundation produced project 169, titled Spectrometric
Standards in 1983 to fill chemistry vacancies of the original NIST standards of 1964. This report details
changes to sample shape and marking techniques from the 1964 NBS publication.
The Iron Casting Research Institute (ICRI) lead an investigation into the production methods for
spectrographic samples. The investigation was spearheaded by Pete Meyst and included process
observations from ACIPCO foundry. A document titled Tentative CRM Production Method was
produced in 2002 and instructed exactly what was needed for a large scale production, 500+ samples per
pour, and techniques behind successful pours.
Individual Foundries provided personal experience, tips and techniques for their current trials for scaling
down the process to a small scale production of spectrometer standards. These foundries include
Waupaca Foundry, Neenah Foundry, and Grede Foundry.
Production of Spectrometer Standards at UW-Platteville
Production methods, materials, and procedures shall be constructed, drafted, verified and published for
creation of reference material suitable for calibration of an emission spectrometer. This includes
creation of a water cooled mold along with all necessary working core-boxes.
2
Knowledge of this research is to be made publicly available through the American Foundry Society and
to any interested parties.
Apparatus
Solidcast Software
Magma Software
Mastercam Software
4 Axis Milltronics Vertical Mill
2 Axis Milltronics Vertical Mill
Water Cooled Copper Mold
Miller Shopmaster Welder
Palmer Continuous Mixer
Palmer Vibrating Molding Bench
Induction Power Supply
Tilt Pour Iron Furnace
Ductile Iron Treatment Vessel
Ladle Preheating Torch
Electro-Nite Datacast 2000
Pyrometer
Figure 1 Water Cooled Copper Mold
Figure 3 2 Axis Milltronics Vertical CNC Mill
Figure 2 4 Axis Milltronics Vertical CNC Mill
Figure 4 Palmer M50XL Continuous Mixer and
Palmer Vibrating Molding Bench
3
Figure 5 Pillar MK8 100kw 3000HZ Induction
Power Supply
Figure 8 Electro-Nite Quik-Lab Datacast 2000
Figure 6 Tilt Pour Iron Furnace 135lb
Capacity, Ductile Iron Treatment Vessel, and
Belch Fire Lade Preheat Torch
Figure 9 Miller Shopmaster 300 AC-DC Welder
Figure 7 Hand Held Pyrometer and Extra
Thermocouple Tips Sitting Atop the Furnace
Cooling Pump
4
Procedure
Sample Design
General sample size and shape must first be determined with the following conditions in mind
Figure 10
a) How will the sample be ground, by hand or mechanically?
b) What is the expected chill depth?
c) Will a specific shape produce a uniform structure?
A plate arrangement of samples and sample spacing is then determined with the following
conditions in mind Figure 11
Realistic sand core thickness between samples
d) Minimum sample separation distance for minimal side heat flow
e) Maximum mold size via machine and budget limitations
Gating Design
1) A pressurized gating system design is created following standard gating principals and
having the following criteria in mind
a) Minimal heat flow from gating system to the samples
b) Fast and complete mold filling Table 4
c) Easy sample de-gating
d) Minimal number of core boxes
e) Simple easy to understand design
2) A 3D model is drafted to reflect the above criteria Figure 13
3) A mold filling analysis is performed for gating verification Figure 12
a) Mold filling criteria are derived from gating calculations
i) 2500oF pour temperature
ii) 8 second fill time
5
iii) 28lb pour weight
Water Cooled Mold Creation
1) Incoming water flow rate is measured from the tap water faucet to be used Table 1
2) A pressurized 6 channel water distribution system is calculated, each channel shall rest below
a row of samples as they would be poured against the copper plate Table 3
3) A CAD model is drafted in Solidworks 3D CAD software representing all machined and
added features of the mold Figure 14
4) Copper plate, cast iron block, hose fittings, hardware, and liquid gasket are procured Table 2
5) 3D Cad drawing is imported into Mastercam CAM Software for tool path generation
6) The cast iron block is first mounted on the 2 Axis Milltronics Mill
7) Using hole center locations, counter bored bolt head holes are machined using the circular
pocket feature
8) Waste plate mounting holes and through block bolt holes are drilled using hole center
locations
9) Waste plate mounting holes are then tapped with a 5/16 x 18 bottoming tap
10) The cast iron block is mounted to a piece of waste plate and coordinated in the 4 axis
Milltronics mill
11) The CAM program is loaded into the 4 axis Milltronics mill and run
12) Once completed on the 4 axis machine. the cast iron block is then clamped on edge on the 2
axis Milltronics Mill to have channel inlet and outlet ports drilled
13) Inlet and outlet ports are then tapped and deburred Figure 15
14) Hose barb connectors wrapped in Teflon tape are threaded into the inlet and outlet channels
15) Next the copper plate is clamped to the bed of the 4 axis Milltronics mill and coordinated
16) The drilling program is loaded into the 4 axis Milltronics mill and run
17) Drilled holes are then tapped with a 3/8 x 16 bottoming tap
6
18) Burrs are removed from all machined areas with a sharpening stone on the cast iron block
19) Raised areas of the copper plate are filed flat
20) The mating surfaces of the copper plate and cast iron block are cleaned with brake cleaner
21) Liquid gasket is applied around the water channels and bolt holes
22) Bolts containing both a washer and lock washer are threaded through the cast iron block and
into the copper plate and hand tightened.
23) The mold is allowed to cure for 24 hours Figure 16
24) Bolts are then torqued to 100 in/lb in a pattern in an alternating pattern from the outside to
the inside in quarter turn increments
25) The hoses are attached and the mold is then pressure tested to check for water-tightness
26) Water flow rate leaving the mold is measured and recorded Table 1
27) A cost analysis of the water cooled mold construction is then verified Table 2
Core Box Creation
1) Sample and gating designs are broken apart in Solidworks and drawn into uniform core
boxes that are large enough for easy stack mold creation later on.
2) The core box designs are then verified against each other for consistent feature placement
3) CAD files are then loaded into Mastercam for tool path generation Figure 17
4) Red Board strips are arranged and epoxied together to form 3 blocks with the minimum
dimensions 13.5in x 16in x 1.5in
5) The block is then fly-milled on the back surface using the 4 axis Milltronics Mill at a depth
that provides a flat final surface.
6) A bolt hole pattern is then drilled into the back surface using a 1.5inch incremental step
command on the 2 axis Milltronics Mill
7) The holes drilled into the back of the block are then tapped with a 5/16 x 18 bottoming tap
8) The block is then mounted to waste plate with 5/16 x 18 countersunk head bolts
7
9) The first block and waste plate are then mounted on the 4 axis Milltronics Mill and
coordinated
10) The axis are zeroed using an edge finder
11) Tools are loaded securely into the tool holders and tools height offsets are set against the top
of the waste plate
12) The CNC program is loaded onto the mill controller and verified and ran Figure 18
13) Steps 5-12 of core box creation are repeated for the next two core boxes using their
respective CNC programs
Mold Cart Creation
1) A cart is designed to hold the water cooled mold on Solidworks Figure 19
a) The design is specified by comfortable pour height and sand core size
2) 1.5in x 3/16 square tubing is then cut to size and dry fit around the water cooled mold
3) The cart is then welded together using a Miller Shopmaster wire welder Figure 9
4) Holes are drilled into the steel tubing at the same locations of the waste plate mounting molts
previously drilled into the cast iron block.
5) The water cooled mold is then bolted to the steel plate which is then welded in place
6) Casters are then fastened to the bottom of the cart
Making Sand Cores
**Thoroughly clean the Palmer continuous mixer after each core box**
1) Check for sufficient quantities of resin, 15 minute catalyst and sand on the Palmer Mixer
Figure 5
2) Gather all necessary molding tools and extra molding boards and molding gloves
3) Inspect the surface of the core boxes for debris or damage
4) Apply parting powder to the interior surfaces of the core box being sure to tilt the core-box to
apply parting power to the vertical surfaces
8
5) Mix sand into a pail for between 15 and 25 seconds depending on the core box
6) Dump the sand into core box
7) Begin molding a core starting at the outside edges
8) Press sand into the deep areas by applying pressure with fingertips
9) Mold around the perimeter of the core and then work inward
10) To compact the interior passages, mold in the same fashion as the perimeter working in
straight lines
11) Disperse any remaining sand over the top of the core box and compact with the palm of your
hand
12) Strike off the top surface immediately after molding is completed Figure 20
13) Tap the side of the core box lightly on all 4 sides to help remove the core from the core box
a) Be careful not to tap too hard or the core will fracture and later break
14) After 5 minuets check the sand strength by pressing lightly on the surface of the core
15) If the sand cured properly it should be strong enough to be removed with ease
a) Removing the core too soon will result in the core crumbling from the core box
b) Waiting unnecessarily long to remove the core will result in the core sticking in the core
box and needing to be broken out
16) Place a large molding board on top of the core box
17) Grasp the board and core box and flip them both over being careful not to drop the core box
18) Set the board and upside down core box on the Palmer vibrating molding table Figure 4
19) While holding the core box against the board, vibrate the core box for 15 seconds
20) Using light fingertip pressure, attempt to lift the core box off the core
a) It helps to squat down and look along the molding board surface to watch the core drop
b) Rock the core box forward and back and left to right slightly to help the core drop
c) If the core continues to stick, try to vibrate the core box again
9
d) If the core continues to stick try tapping the back of the core box
e) As a last measure to remove the core lift the molding board and core box up to a height of
2-3 inches and thrust them downward at the table
i) This method should be used as a last resort, it can easily break the core
f) Once the core is removed, transfer it to a smaller molding board and store in a safe, level
place
g) Repeat core making procedures for all remaining core boxes
i) The core containing the direct pour riser is currently loose molded in a steel frame as
it awaits larger core box creation
ii) Mold at least one more of each core to be safe if one should break
h) Molds can be dried in a microwave oven to aid removal of moisture Figure 21
i) It is best to let cores set-up for at least 24 hours on a well ventilated rack to permit
adequate binder strength
Assembling the Sand Mold
1) Gather all 4 premolded sand cores, level, and an air hose and nozzle
2) Position the mold cart in a convenient location and route hoses out of the way
3) Check the surface of the mold cart with a level, adjust if necessary
4) Using your fingers, rub all edges of the cores to remove any sand fins
5) No core glue is to be used between mold layers, instead the layers are to be rubbed together
to form a tight seal
6) Begin by rubbing the bottom side of the sample core against the copper plate, rub in a tight
circular motion
7) Next, with the sample core oriented on the copper plate, rub the bottom of the gate core
against the top surface of the sample core
8) Position the gate core correctly on the sample core
10
9) Continue the same process, rubbing the runner core and pour cup core against the core that
will sit below it
10) Carefully disassemble the mold assembly and blow off the copper plate
11) Now reassemble the fitted cores back in position, blowing off each core before adding it to
the mold Figure 22
12) Add at least 200lbs of mold weights to the top of the mold
13) Cover the pouring basin to prevent debris from entering the mold
14) Green sand can be packed around the mold if desired Figure 23
a) Packing green sand around the mold will increase the mold change time, or only allow
one pour per heat
Pouring a Heat
1) A melt procedure has been posted in the UW-P foundry and the procedure found therein is
what will be used to melt Table 8
a) A melt pour and temperature log must be kept Table 5
i) The melt procedure may be different for each foundry and furnace charge material,
always follow the same melt rates to achieve a high level of consistency
ii) Data should be collected and logged to establish more accurate melt data and data
comparisons
b) Remember to pour a chill wedge and spectro button
i) Chill depth on the chill wedge should also be recorded
c) If pouring multiple heats in succession there is no need to preheat the furnace lining and
melting may begin immediately
Preliminary Analysis
1) A chill wedge should be sectioned and its chill depth recorded
2) Sample locations are then marked with a paint or permanent marker Figure 24
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Statistical Analysis and Chemistry Certification
1) Chemistry certification criteria are determined by each individual company requesting
samples
2) Certification should follow appropriate statistical sampling sizes
a) Reference ASTM publication E 1724-95 Standard Guide for Testing and Certification of
Metal, Ores, and Metal-Related Reference Materials
b) Once enough heats have been poured to assure process consistency, a reduced number of
samples may be tested if desired
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Data
Table 1 Water Flow Rate Into and Out of the Water Cooled Mold, Measured by Weighing Water
Collected In a 5 Gallon Pail over a 10 Second period, Average Amounts Shown Below
Measured Flow Rate
Weight
Time
(lbs)
Gallons (sec)
Gal/Min
Input Rate
17.1
2.06
10
12.36
Output Rate
15.78
1.90
10
11.41
Table 2 Cost Breakdown of Building the Water Cooled Mold
Water Cooled Mold Cost
Part
Quantity
Individual
Cost
Copper Plate
1
565.09
Cast Iron Plate
Threaded Hose
Barb
Liquid Gasket
Hose Clamps
Hose (per foot)
Teflon tape (per
roll)
1
129.73
2
1
3
25
2.63
3.38
0.59
0.54
1
2.59
Bolt
Lock Washer
Washer
16
16
16
0.30
0.03
0.04
Total Cost
Unit
Cost
Description
Cold Rolled 110 Cu Plate 12 x
565.09 12 (+,-.063) x 1 in (+,- .024)
12.25 x 12.25 x 2in Continuous
129.73 Cast Gray Iron Slab (Donated)
1/2in NPT - 5/8 ID Hose Barb
5.26
RTV Silicone Sealant, 650oF
3.38
1.77
1in Diameter
13.50 5/8in ID Radiator Hose
1/2in Wide Teflon Tape Roll,
2.59
25ft
3/8in Dia x 2 3/4in x 16
4.78
Threads/Inch, Grade 5
0.45
3/8in Dia
0.66
3/8in Dia
Manufacturer/
Distributor
Copper and
Brass Sales
Dura-Bar
ACE Hardware
Permatex
ACE Hardware
ACE Hardware
ACE Hardware
Fastenal
Fastenal
Fastenal
727.2
13
Table 3 Water Cooled Mold Coolant Channel Calculations Spreadsheet Screenshot
Table 4 Gating Calculations Spreadsheet Screenshot
14
Table 5 Melt Log for 4-26-07 Ductile Iron Melt
Melt Log 4-26-07
Actual
Time
Scheduled
Time
10:39
11:40
12:00
0:00
1:00
1:20
12:20
1:40
12:45
2:00
12:55
1:20
1:25
1:30
2:15
2:30
2:35
2:40
Event
Charge returns, Preheat lining
(Begin preheating treatment vessel ductile only)
Increase power to begin melting
Charge pig, all returns have been charged
Charge graphite, FeSi, FePhos, FeCr, Etc and begin
charging steel, all pig has been charged
All charge melted, increase bath temperature to 2800oF
Deslag melt, pour thermocouple cup to verify carbon and
silicon content, add graphite or FeSi as necessary
Prepare treatment vessel and treat iron (ductile only)
Pour chill sample mold, final thermocouple cup
Sand mold removed from copper plate
Temperature and Event Log
Time
12:45
12:55
1:05
1:17
1:20
Temperature
2750
2775
2835
2870
1:25
2535
Event, mold pour times, chill wedge chill depth
Prelim Thermocouple Cup C:3.7 Si: 2.3
Tap Furnace into Treatment Vessel
Pour Chill Sample Mold, Spectro Button and Chill Wedge
Depth .4in, No Final Thermocouple Cup Poured
15
Table 6 Iron Heat Chemistry for the Second Sample Heat
16
Table 7 Iron Heat Final Chemistry Continued From Table 6
17
Results
First Pour Results
Chill depth within the first pour appeared promising. Upon sectioning a sample a white iron
microstructure was observed unmagnified as fractures exposed a dendritic structure extending
half the height of the sample. After polishing and examination of the microstructure it was
determined the samples were unsuitable for use as standards due to the presence of graphite
nodules interlaced into the dendrite arms. Reason suspect for this occurrence has thus far been
poor melt practice, resulting in the late and unintentional inoculation of the bath just before and
during magnesium treatment. A second test heat has been scheduled and will attempt to
eliminate the presence of the nodules via strict melt practice. Thus far, no additives such as
Tellurium and Bismuth have been utilized to induce chill.
All samples have filled and have no shrinkage along the chill surface.
Samples were easily removed from the gating system, however they contained much burn-on and
cannot be run through a shot-blast machine for fear of removing the sample markings applied
with a paint marker.
Water condensation was observed on the copper plate from the sand cores after iron was poured
into the mold. This occurrence would hinder multiple pours in rapid succession because of the
safety hazards imposed. A longer cure time may be the remedy for this situation, or the use of a
long preheating cycle in a microwave oven to drive moisture from the mold.
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Second Pour Results
For the second heat, backing sand was not packed around the sand mold. A run out was then
experienced as a corner of the runner mold broke out as the runners filled with iron. Backing
sand was intentionally avoided to determine how the mold would react and determine the
viability for a run out between the mold layers. An in layer breakout was not expected and its
occurrence fostered questions about binder choice. A possible remedy for this situation would
be to use backing sand around every mold, or attempt a different sand binder with a lower
expansion characteristic.
The pour event and temperature log can be found in Table 5. The melt progressed without
incident and occurred at a faster pace than predicted.
Samples contained significant cold lapping and a sunken center section along the chill surface.
A slow pour time and a run out in runner bar core may be to cause for this.
Samples were easily removed from the gating system and present the same challenges in
marking and cleaning as experienced in the first heat.
Water condensation was again experienced upon the copper plate even after a 2 day core curing
period.
A chemistry calculation found in Table 6 was in error due to the absence of a silicon recovery
rate in the properties table; this mistake increased the silicon value by .5%, the chemistry
calculator appeared correct for the other elements.
19
Polishing and examination of the microstructure shows a presence of type I to type V graphite
nodules among a white iron dendritic structure, however in fewer quantities than experienced in
the first heat. Further examination also shows the presence of micro cracks and shrinkages
throughout the sample and also localized around the in-gate. Further research should be
conducted on the affect of these cracks on sample integrity and on the presence of the graphite
nodules and the use of a chill inhibiter to prohibit the formation of graphite in ductile iron.
Discussion
Sample Design Considerations
The sample diameter was chosen based upon existing RM standard sizes, and increased slightly
to maximize use of the available surface area of copper plate while still allowing a minimum of
.25in sample spacing for sufficient sand core strength.
The sample height was chosen to be 3/4in based upon test heats which took place months before
the sample design. In those tests a maximum chill depth of .25in was observed against an
uncooled copper plate. Following that observation the original sample design having 1in height
was reduced to eliminate extra metal volume and consequently extra heat which would need to
be dissipated. A sample height less that 3/4in may produce a microstructure containing deeper or
even complete chill, however this has yet to be investigated and has thus far been deemed
unnecessary as the samples were designed to be hand ground and should keep a rather tall
appearance.
Improvements to the Current Setup
Quick Change Mold System
A mold securment system has been suggested a novel idea to allow for the pouring of sequential
molds. Molds may be assembled elsewhere and then quickly placed upon the copper plate as a
single unit. Ideas to secure cores together include through bolts or a key core molded around the
20
entire assembly. After a short 5 minuet cool down on the copper, the assembled sand core
package could be slid out of the way and another assembled mold may be placed on the copper
plate. This method would increase the number of pours per heat, and could be used to produce
samples of intentionally varying magnesium content in ductile iron. Temperature of the water
flowing through the water cooled mold experienced a minimal increase; the mold could easily be
used for rapid pours without taxing the heat removal rate of the system.
Permanent Sample Markings
A permanent method for sample marking needs to be implemented. The current core boxes have
no surfaces available for engraving permanent sample markings because of the current parting
plane locations. A possible remedy for this may include the utilization of core-blowing instead
of hand packing. In such a process the existing gate and sample molds could be mated together
to form a single core, this would allow the samples core box to be engraved with the sample
location.
Sand Binder Choice
The sodium silicate binder system employed at the University of Wisconsin-Platteville has
serious limitations when used with high mold temperatures such as those experienced when
pouring iron. Molds are prone to cracking and the binder hardens significantly upon
experiencing high temperatures facilitating difficult mold removal. To alleviate this problem a
different binder system designed for high temperature use should be utilized.
Sample Core Box Material
The idea of eliminating the bottom sample core box and instead using a machined copper plate
has been suggested. This approach may provide the opportunity for increased chill depth if
needed. One foreseeable consequence to this approach is the sample contraction away from the
copper walls as it cools which could result in uneven chill depth.
21
Conclusion
Production of spectrometer standard samples in small batches appears promising although
further research is required to refine aspects such as choice of binder systems and mold
construction techniques. The process shows potential at producing rapid succession pours for
fast production of samples.
References
Preparation of NBS White Cast Iron Spectrochemical Standards, U.S. Dept. of Commerce,
National Bureau of Standards, Misc. Publication 260-1, Issued June 19th, 1964.
Spectrometric Standards. Project 169, Metals Research and Development Foundation, Prepared
by Price Burgess, April 15th 1983
Tentative CRM Production Method, Iron Casting Research Institute Ad Hoc task group lead by
Pete Meyst, Oct. 15th 2002
Standard Practice for Testing Homogeneity of Materials for Development or Reference
Materials, American Society for Testing and Materials, E 826-85 (Reapproved 1996)
Standard Guide for Testing and Certification of Metal, Ore, and Metal-Related Reference
Materials, American Society for Testing and Materials, E 1724-95 (Reapproved 2001)
Standard Guide for Planning, Carrying Out and Reporting Traceable Chemical Analysis of
Metals, Ores and Related Materials, American Society for Testing and Materials, 2053-00
22
Appendix A
Figure 10 3D Model of Sample Size and
Specifications, Samples Include 5 Degrees
of Draft
Figure 11 Sample Layout on the Copper
Plate
Figure 12 Solidcast Mold Filling Analysis Screenshots
23
Figure 16 Assembled Water Cooled Mold
Waiting for the Gasket Sealer to Cure
Figure 13 3D Model of the Gating System as
it would Rest on the Copper Plate
Figure 17 MasterCAM Toolpath
Visualization for the Samples Core box
Figure 14 3D Model of the Cast Iron Block
as it would Contain Coolant Passageways
and Bolt Holes
Figure 18 Machining of the Runner-Bar
Corebox
Figure 15 Machined Cast Iron Block
24
Figure 19 3D Model of the Mold Cart
Figure 22 Assembled Sand Mold
Figure 20 Sand Core yet to be Removed
from the Core box
Figure 23 Assembled Sand Mold Ready to
Pour
Figure 21 Sand Cores Awaiting Mold
Assembly
Figure 24 First Set of Standards Cast on
4-12-07
25
Table 8 Tentative UW-Platteville Iron Melt Procedure
26