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Inclusion Problem in Iron and Steel Castings
"Dirty" metal is the most obvious source of inclusion material. Unwanted materials may enter the melt through any number of ways including the addition of unshotblasted returns to the charge, oxidation problems during metal transfer, the generation of reaction products of alloying elements and other melt treatment products and the erosion of refractory materials and slag build-up due to poor ladle maintenance.
Non-metallic inclusions are a major cause of defects in iron and steel castings. Some, such as furnace slag, ladle slag, flux and alloying residuals, are generated outside the mould and are carried into the mould cavity with the molten metal stream. Others start off inside the running system and mould cavity; these include mould sand, core and core coating materials and reoxidation inclusions generated when the molten metal is exposed to air in the mould during filling. Non-metallic inclusions compromise the physical properties and surface appearance of the casting, contribute to increased scrap rates or added cleaning room expense and create greater potential for customer returns because of machinability problems. Both prevention and removal tactics are used to reduce casting inclusions. Melting practices, ladle design and gating system design can all be optimized to decrease the occurrence of nonmetallic inclusions in iron and steel castings. One of the most efficient techniques is the use of ceramic foam filters.
How CERAFOAM® Ceramic Foam Filter Works
CERAFOAM® Ceramic Foam Filters are made first time in India by a Dynamic Indian Company, whose R&D Dept. works 24 hours to develop supreme class foundry products. CERAFOAM® Ceramic Foam Filters are multidimensional filters. The metal must flow through a torturous path before it enters the casting cavity. First, coarser size inclusions, which are too large to enter the passageways, are trapped on the surface of the filter. As inclusion begin to accumulate on the filter face, a thin cake of inclusion is formed which only permits retention of some finer particles. Molten metal that flows past the filter cake and into passageways follows a tortuous path through the body of filter. The foam filtration mechanism is based on multiple changes in metal flow direction and reduction of flow speed, causing smaller particles to be trapped in the internal filter structure. It also helps to prevent the formation of reoxidation inclusion by promoting reduced-turbulent flow as the molten metal enters the casting cavity.
Comparison with Other Filters Used in Foundry Practice
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Feature
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Foam
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Extruded
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Pressed
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Dimensional Accuracy
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Moderate
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High
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High
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Cold Strength
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Moderate
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Moderate
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High
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Filtration Effectiveness
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High
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Moderate
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Moderate
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Particle Retention Size
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Fine
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Medium
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Medium/Coarse
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Effect on Flow Rate
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High
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Moderate
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Moderate
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Turbulence Reduction
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High
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Minimal
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Minimal
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Erosion Resistance
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High
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Moderate
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Moderate
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Refractoriness
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High
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Moderate
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Good
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Effectiveness Chart of CERAFOAM® Ceramic Foam Filters
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Size of Direct Pouring Unit
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Metal in the Unit
(cc)
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Effective Modulus
(cm)
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Filtration Capacity
Kg
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Filtration Capacity
Kg
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Flow Rate Kg/Sec.
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Flow Rate Kg/sec.
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C.I./Gray Iron
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SG Iron/Cu
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C.I./Gray Iron
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SG Iron/Cu
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40X120
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191.00
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1.57
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35 to 50
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10 to 17
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2 to 3
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1 to 2
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50X150
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380.00
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1.99
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55 to 80
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18 to 26
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3 to 5
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2 to 3
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70X175
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840.00
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2.61
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110 to 155
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35 to 50
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6 to 9
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4 to 6
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90X200
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1550.00
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3.47
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180 to 255
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55 to 85
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10 to 15
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7 to 10
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Available Sizes of CERAFOAM® Ceramic Foam Filters for Use in Sprue Base and Gating System
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Round Foam Filters
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Square & Rectangular Foam Filters
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40 mm dia x 20 thk
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40 x 40 x 15
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50 mm dia x 20 thk
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50 x 50 x 22
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70 mm dia x 20 thk
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60 x 60 x 15
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90 mm dia x 20 thk
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75 x 75 x 22
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100 x 100 x 22
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50 x 75 x 22
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50 x 100 x 22
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75 x 100 x 22
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All dimentions are in mm All above sizes are available in 10 PPI & 20 PPI
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Benefits of Using CERAFOAM® Ceramic Foam Filters
Benefits of using CERAFOAM® Ceramic Foam Filters are not confined to filtration efficiency, but leads to Scrap Control, Productivity Improvements and Casting Quality Improvements.
- Lower levels of scrap produced;
- Lower tonnes shipped to tonnes melted ratio (yield) due to the elimination of long running systems designed to float out inclusion leads to savings throughout the foundry.
- Simplified gating systems since the filter itself will reduce velocity and smooth the flow of liquid metal;
- Helps using pattern plate efficiently.
- It can be positioned vertically, horizontally, or diagonally in a suitably designed runner system.
- Enhances mechanical properties such as tensile strength and elongation by way of controlling non-metallic inclusions.
- Improved mechanical properties due to greater metallurgical consistency;
- Increased fluidity of the metal improves casting finish, appearance and surface details.
- Machining allowances can be reduced with confidence due to a lower level of inclusions;
- Faster cycle times, especially where there are major savings in after-cast operations increases work schedule flexibility & foundry competitiveness;
- Desired directional solidification conditions are generated by the use of this system.
Raw Materials Group of India
402/A,Opp.Water Tank, Phase II,
G.I.D.C. Vatva, Ahmedabad-382445. (Guj) India.
Tel: +91-79-25830119 (Office Hours 10 am to 6 pm)
Fax: +91-79-25830789
Authorized Distributor of CERAFOAM® Ceramic Foam Filters for Gujarat, Rajasthan and Madhya Pradesh Region.
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