Defects & Cause. Defects Root Cause Shrinkage Rusty charge: very high chilling tendency in this iron low content of CE EFFECT OF SUPERHEATING Metal Holding Excess magnesium Under inoculation or over inoculation High Pouring temp Chunky graphite High Purity charge materials High CE High %RE(rare earth) High Pouring Temp Mech Failure Poor Charge Mix Fadding ELEMENT SEGREGATION TENDENCY Blow Hole Low Pouring Temp Slag inclusion Rusty charge materials Poor Pouring Practice
Types of shrinkage Decrease in volume of the metal as it solidifies Outer sunks: Outer sunks (pull downs, sinks) can be seen from the outside of the casting, usually as a smooth depression in the casting surface. Macro shrinkage: Macro shrinkages are usually found inside the casting and close to heat centers. They appear as larger holes, Defect size >5mm Micro shrinkages: Micro shrinkages are smaller cavities with irregular surfaces. Defect size <3mm also called porosity
Shrinkage Rusty charge: High Magnesium: very high chilling tendency in this metal High Magnesium: Very high chilling tendency in this metal High magnesium content acts to promote carbidic microstructures and increase shrinkage
Shrinkage Effect of Superheating: Holding: the temperature of any melt is increased above the normal melt temperature (high superheat), nucleation has been reduced. Holding: The longer the hold times, at any temperature, the greater the loss of nucleation.
Shrinkage Under inoculation: Not enough to precipitate Carbon as a graphite Over inoculation: Too many nucleation points are active early in the solidification feeders become inactive and contraction takes place, there is no graphite
Chunky Graphite Entrapment of gases in the cavity while pouring Chunky Graphite Entrapment of gases in the cavity while pouring. Occurrence: were the casting thickness is more High RE: Excessive cerium in the metal will cause the chunky graphite. Wall thickness < 25 mm Ce 0,020 – 0,015 % 25 – 50 mm Ce 0,015 – 0,010 % 50 – 100 mm Ce 0,010 – 0,005 % 100 – 250 mm Ce 0,005 – 0,002 % 250 mm Ce 0,002 – 0,000 % High Purity Charge material: Charge more than 50% sorrel PI cause there is no trace element eg: Pb,Bi,Sb etc High Pouring Temp & Holding: Both will affect the nucleation of SG to form CHG. High CE: Increased volume of the graphite
Mechanical Failure Exploded Graphite Excess, rare earths can cause exploded graphite. At very high carbon equivalent (CE). Exploded graphite is normally found in thicker section castings with slow cooling rates. High purity charges are used which are low in detrimental tramp elements such as lead, bismuth, antimony, titanium etc
Mechanical Failure Graphite Flotation At very high carbon equivalent (CE). The nodules, being of a lower density than the matrix, tend to float towards the surface of the casting.
CE shrinkage V1/V V2/V
Slag Inclusion A product resulting from the action of a flux on the oxidized non-metallic constituents of molten metals. Occurrence: Any place of the casting Rusty Charge: Charge containing oxide products (e.g:Rust CRS & Borings), that one oxidize the metal. it will cause Heavy slag formation in the metal. Pouring Practice: Slag should be removed thoroughly. Metal level should be maintained 75% of basin capacity during the pouring. Min 300Kg metal maintained in the Basin Material Charge Mix Slag steel 1-2% DI Returns 5-10% Pig iron 0.12% rusty scrap 12% Borings 25%
Dross Non metallic inclusion is called Dross Occurrence: Surface of the casting Excess residual Mg (>0.050%)in the metal react with oxygen & sulphur to form Mgo,Mgs respectively. It will appear on the surface of the casting. Low pouring Temp: mg easily react with Si to form Mgsi2 (During Inoculations) Turbulence: Rapid flow of metal into the mould Will cause Dross
Blow Hole Entrapment of gases in the cavity while pouring Blow Hole Entrapment of gases in the cavity while pouring. Occurrence: Any place of the casting Low Pouring Temp: Gas molecules not easily escape from the mould at low temp. Ti & Al content in metal: it will promote the evolution of the gas in the metal.
Requirements for cast-on sample as per standard DIN 1563-2003-02[5] Requirements for cast-on sample as per standard DIN 1563-2003-02[5] Material designation Walll Impact Mean(J) Impact Individual(J) Min. tensile Min. Yeild % Elong thickness, t(mm) strength(N/mm2) EN-GJS-350-22U-LT Impact at - 40 ± 2℃ < 30 12 9 350 220 22 30 < t ≤ 60 330 210 18 60 < t ≤ 200 10 7 320 200 15 EN-GJS-400-18U-LT Impact at - 20 ± 2℃ 400 240 390 230 370
Mechanical Failure The following Metallurgical defect Can cause the Mechanical failure. 1.Fading 2.Exploded Graphite 3.Chunky Graphite 4.Compacted Graphite 5.Graphite Flotation 6.Spiky Graphite
Mechanical Failure Fading Holding the metal after treatment will cause Fading High Sulphur content in the bath Inadequate inoculation
Mechanical Failure Compacted Graphite Incorrect weighing of the nodulariser. Although a long holding time in the ladle or excessive temperatures.
Mechanical Failure Spiky Graphite Excess, Trace elements such as lead, bismuth, titanium and antimony present in the metal to form Spiky Graphite.
Grey & SG iron ASTM A48 (Class 30, 35, 40? Gray Iron Castings ASTM 159 or SAE J431 ( G4000, G3500, G3000, G2500, G1800) Automotive Gray Iron Castings ASTM A319 Class I, II, III Gray Iron Castings for Elevated Temperatures ASTM A436 (DIN 1694, BS 3468) Ni-Resist Castings, Austenitic Gray Iron Castings DIN 1691 (GG10, GG15, GG20, GG25, GG30, GG35) EN 1561 （EN-GJL-200, EN-GJL-250, EN-GJS-300, EN-GJS-350,EN-GJS-400, EN-GJS-500, EN-GJS-600, EN-GJS-700) , ISO 185 SG IRON ASTM A536 (60-40-18, 65-45-12, 80-55-06?100-70-03, 400-15, 500-7, 600-3) Ductile Iron Casting ASTM A439 (DIN 1694, BS 3468) Austenitic Ductile Iron ASTM A897 Austempered Ductile Iron ADI ASTM A571 Low Temp, Pressure-Containing DIN 1693 (GGG-30, GGG-40, GGG-50, GGG-60, GGG-70, GGG-80) EN 1563 (EN-GJS-400-15, EN-GJS-450-10, EN-GJS-500-7, EN-GJS-600-3, EN 1563 EN-GJS-400-18-LT) SAE J434（D4018, D4512, D5506?D5504?D7003, D700, D800, D400) ISO 1083, BS 2789
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