1. The Pros and Cons about Melting Galvanized Steel Charge In a
Silica-lined Coreless Induction Furnace
Co-Authors
Mr. David C. Williams Allied Mineral Products
(Presenter)
Mr. Saito Kiriu Corp.
Mr. M. Imasaki Kiriu Corp.
Nippon Crucible Ltd.
Dickinson’s Metallurgical Supplies

2. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Definition of the problem with
Zinc-Coated Charge
Any zinc-coated charge has always
caused numerous infiltration of
coreless furnace linings, especially
when melting iron alloys.
Zinc will melt at 787F( 420C).
At 1664F(907C), Zinc will turn into
a gas, easily penetrating the porosity
of the sidewall. At the point of Zinc
Solidification Temperature, the metal
will collect in the form of a metallic
fin.
With conventional lining design, the
Zinc will reach the coil grout and
copper coils, even though the copper
coils are water-cooled. Eventually, “turn to
turn” coil arcing will result.

3. Corrosion Service Coatings for Steel Strip
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Corrosion Service Coatings for Steel Strip
Galvanizing Alloy Zn 99.7% Al 0.3%max.
Galfan Zn 95% Al 5%
Galvalume Alloy Zn 55% Al 45%

4. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Kiriu Corporation
Case study of a 6MT, 50 Hz, coreless induction furnace used for melting Ductile-base iron,
C 3.85%, Si 1.85%,
Mn 0.25%, S 0.03%max, P 0.03%
Allowable Zn %
Typical Charge:
Treated Ductile Returns, Pig Iron,
20% Galvanized Steel Trim
Refractory Lining:
Silica Dry Vibratable w/ Boron Oxide Bond
Total Tonnage for a Typical Lining Campaign:
tons, Shave Repairs every 1000 tons in Taper and Floor
©2004 Allied Mineral Products, Inc

5. Cross Section of Furnace Lining
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Second Antenna
0.5 mm Al
Heat Insulation Sheet
120 mm SiO2 Refractory
Cross Section of Furnace Lining
Coil
3 mm Mica Sheet
Courtesies of Kiriu Corporation 2002
©2004 Allied Mineral Products, Inc

6. Classic Model for Finite Elemental Analysis for 6MT Coreless Furnace
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Classic Model for Finite Elemental Analysis for 6MT Coreless Furnace
HIGH ALUMINA GROUT
120 mm
SILICA
©2004 Allied Mineral Products, Inc
2mm MICA
2mm MICA

7. FINITE ELEMENT ANALYSIS OF 6MT CORELESS FURNACE
HIGH ALUMINA GROUT
2mm MICA
120 mm
SILICA
0.5mm
ALUMINUM FOIL
6mm
INSULATING BOARD
2mm MICA
©2004 Allied Mineral Products, Inc 1

8. Installation of Second Antenna/ Ground Detection Foil
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Installation of Second Antenna/ Ground Detection Foil
- A metallic ring is placed
against the upper portion
of the furnace.
Vertical steel strips, spread
apart 200 mm around the
ring, will help to keep the
0.5 mm Al foil lay flat
against the mica back-up.
It is important to get the
Al foil to lay flat without
any air pockets. Air
will disrupt the thermal
profile through the silica
sidewall and will lead to
deeper zinc penetration.
Courtesies of Kiriu Corporation 2002

9. Installation of the Floor Refractory
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Installation of the Floor Refractory
Dumping 125 mm of loose silica dry vibratable per layer.
Deairing 4 passes per layer.
Add mm of excess silica over desired floor thickness.
Vibrate floor with pneumatic form vibrator attached to 25mm thick floor plate, for a 15 minute period.
Scrape back any excess silica and remove from furnace.
Level floor surface, then set melt-in steel form.
Set melt-in steel form into place.
Courtesies of Kiriu Corporation 2002

10. Sidewall Installation using the Netter-Cross Vibrator Rig
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Sidewall Installation using the Netter-Cross Vibrator Rig
Once form has been properly aligned and secured, the material is introduced into the sidewalls in 100 mm layers.
This is followed by a leveling step.
Each layer is deaired 4 passes.
A Netter-Cross Vibrator is then placed approximately one third of the vertical form height, up from the bottom.
A 20 minute vibration period is used. During this period, the silica level will drop, requiring more silica to be added.
Courtesies of Kiriu Corporation 2002

11. Preparation of Sintering of Lining
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Preparation of Sintering of Lining
Once the vibration sequence has been completed, the rig is removed and solid charge (i.e. grey iron starter blocks) is carefully stacked inside of the form.
The steel plates of the furnace structure are attached.
A minimum of 3 “K” type thermocouples are placed at the top, the middle and at the floor, to help monitor temperature during the sinter.
Courtesies of Kiriu Corporation 2002

12. Inner Hot Face Surface of Conventional Silica Refractory
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Inner Hot Face Surface of Conventional Silica Refractory
Gray Area
Orange Area
Normal Area
Courtesies of Kiriu Corporation 2002

13. Outer Cold Face Surface of the Conventional Silica Refractory
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Outer Cold Face Surface of the Conventional Silica Refractory
Gray Area
Powder Gathered on this side
Courtesies of Kiriu Corporation 2002

14. Shaving Floor Refractory Using Bosch Installation
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Shaving Floor Refractory Using Bosch Installation
After the penetrated silica was removed from the taper and floor, the new floor is installed using the Bosch vibrator tamper method.
Each 125 mm layer of loose silica is deaired at least 4 passes before compaction with the Bosch.
A full sintering process is followed.
Courtesies of Kiriu Corporation 2002

15. Shave Repair of the Conventional Silica Refractory
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Shave Repair of the Conventional Silica Refractory
in the Taper Section after Penetration/Erosion
Typical lining life varies between 900 to 1000 tons throughput.
Relines are determined by measurements in the taper and floor.
Galvanized steel charge represents 20 % of the charge.
This furnace was lined with
a modified silica mix and completed 1436 tons throughput without repair.
Courtesies of Kiriu Corporation 2002

16. A View of A Spent Furnace Lining after 1436 Tons
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
A View of A Spent Furnace Lining after 1436 Tons
Without Any Repair (Newly Redesigned Silica)
The sidewalls showed minimal erosion.
The taper section has eroded approximately mm.
No taper or floor shave repairs performed.
No zinc penetration reaching through the silica or reaching the Al antenna foil.
Courtesies of Kiriu Corporation 2002

17. Demolition of the Floor Refractory after 1436 ton campaign
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Demolition of the Floor Refractory after 1436 ton campaign
No Zinc metal penetration was detected in the floor refractory.
Unsintered, loose silica refractory remained in the floor.
Ground Detection wires are still intact.
Courtesies of Kiriu Corporation 2002

18. Complete Demolition of the Redesigned Silica Lining
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Complete Demolition of the Redesigned Silica Lining
No zinc evident against the heat insulation board or on the cold face of the silica lining.
No zinc was observed on the cold face of the heat insulation.
No zinc was picked up on the Al foil in between the two layers of mica.
Courtesies of Kiriu Corporation 2002

19. Inner Hot Face Surface of Heat Insulation Sheet
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Inner Hot Face Surface of Heat Insulation Sheet
Normal Area
Dark Area
Courtesies of Kiriu Corporation 2002

20. A View of the Hot Face Surface of the 0.5 mm Al Antenna Foil
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
A View of the Hot Face Surface of the 0.5 mm Al Antenna Foil
During the demolition of the lining, there was no evidence of zinc deposition on the hot face of the Al foil.
A portion of Al foil is peeled back to show the cold face surface.
The discoloration of the foil is due to the presence of heat stored within the lining.
Courtesies of Kiriu Corporation 2002

21. The Cold Face Surface of the Second Antenna Foil
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
The Cold Face Surface of the Second Antenna Foil
Specimen with White Powder
Courtesies of Kiriu Corporation 2002

22. Hot Face Surface of the Al Antenna Foil
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Hot Face Surface of the Al Antenna Foil
Less Burnt Area
Courtesies of
Kiriu Corporation 2002
Black Burnt Area

23. Mica Layer after a 1436 ton campaign
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Mica Layer after a 1436 ton campaign
Hot face of the first layer of mica between the grout and the metallic foil / antenna.
No zinc penetration was evident.
Courtesies of Kiriu Corporation 2002

24. A View of the Shunts of the Power Coil after 1436 ton Campaign
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
A View of the Shunts of the Power Coil after 1436 ton Campaign
No zinc penetration against the shunts, indication no zinc reaching the copper coils.
Courtesies of Kiriu Corporation 2002

25. A Close-Up View of the Power Coil and the Electrical Shunts
Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
A Close-Up View of the Power Coil and the Electrical Shunts
No zinc presence on the coil or on the face of the shunts.
Clean coil with no zinc presence.
Courtesies of Kiriu Corporation 2002

26. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Old Silica New Silica
Saturation comparison: Old 50mm New 0 mm.
Courtesies of Kiriu Corporation 2002

27. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Old Silica New Silica
Saturation comparison: Old 60mm New 23mm.
Courtesies of Kiriu Corporation 2002

28. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Old Silica New Silica
Saturation comparison: Old mm New 24mm.
Courtesies of Kiriu Corporation 2002

29. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Courtesies of Kiriu Corporation 2002

30. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Courtesies of Kiriu Corporation 2002

31. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge
Courtesies of Kiriu Corporation 2002

32. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge in a Silica-lined Coreless Induction Furnace D. Williams
Summary:
Changes were made to a conventionally designed silica dry vibratable
to help minimize zinc penetration in the sidewall of a coreless induction
furnace when using galvanize-coated steel charge.
Zinc penetration did not reach the secondary Al foil antenna, nor the
power coil. Some zinc penetration observed within the floor, the taper,
and the sidewall, but was less than the conventionally-designed silica
dry vibratable.
Although significant layers of slip plane and insulation was used, no
Zinc was found against the mica or secondary antenna.
Ultimately, lining life had improved from tons melted to
1436 tons melted without any shave repair. This was done while using
20% of the charge as galvanize-coated steel charge.

33. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge in a Silica-lined Coreless Induction Furnace D. Williams
The Pros of Melting Galvanized Steel Charge in a Silica-lined
Coreless Induction Furnace
Allows for more diversity in Charge and may lower melting costs. With
the demand for steel charge and the subsequent shortage, this may
represent a possible solution.
Using the Aluminum foil as a secondary Leak detection system,
also allows the foundry to have an impervious layer to shutdown
Zinc permeating to the coil. It would have a similar effect towards
other low temperature non-ferrous metals such as Lead, Tin or Bismuth.
Less penetrated hot face of the silica typically results in longer service
life of the coreless furnace.
A change in the silica product is needed as well as a change in the
Sintering process.

34. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge in a Silica-lined Coreless Induction Furnace D. Williams
The Cons of Melting Galvanized Steel Charge in a Silica-lined
Coreless Induction Furnace
Early Zinc Penetration to coil causing turn to turn electrical arcing.
The cost of the Aluminum foil
Lower Service Life due to erosion of hot face
Zinc Vapor will be collected in the pollution control system and
will cause a build-up as time progresses.

35. Australian Foundry Institute Conference November 2004 Pros and Cons of Melting Galvanized Steel Charge in a Silica-lined Coreless Induction Furnace D. Williams
This presentation was made possible through the successful
efforts of Mr. Saito and his melt personnel, who incorporated
the use of galvanized-coated steel charge as a viable part of
a ductile-base charge (approximately 20%) for a 50 Hz,
continuous heel melting operation at Kiriu Corporation.
It has always been a challenge to successfully use galvanized
steel in any coreless induction furnace. The problem is zinc
deposition on the copper coils, leading to “turn to turn” arcing.
Complete zinc infiltration of all refractories including the coil
grout will often be the outcome. Kiriu Corporation has developed
a method of using galvanized charge as part of a ductile-base
Iron heat in a silica-lined coreless induction furnace.
Kiriu Corporation with assistance from Nippon Crucible Ltd.
have successfully managed this problem for the past 2 years.