Ductile Iron Vs Cast Iron


Ductile Iron Vs Cast Iron

Ductile Iron Vs Cast Iron, it is possible to bend ductile iron without it breaking. But as cast iron is brittle, when it is bent, it will break. Ductile iron vs cast iron valves, the biggest difference of all between the two is that, valves that are made from cast iron are not at all ductile. Ductile iron vs cast iron corrosion, ductile iron corrodes less quickly than cast iron. Pig iron is used to produce ductile iron

Cast iron vs ductile iron water pipe, as pipes made from ductile iron are stronger than pipes made from cast iron, pipes made from ductile iron are thus used in water lines and sewage lines. Looking at cast iron vs ductile iron cost or ductile iron vs cast iron price, as ductile iron has a more complicated chemical makeup than cast iron, it costs more than cast iron.

How to tell the difference between cast iron and ductile iron pipe, pipes made from ductile iron are more durable, they are stronger and they are lighter than pipes that are made from cast iron. Also, the difference in the two is that the graphite form in ductile iron is nodular or spheroidal. But in cast iron, the graphite is in the form of flakes. When we compare Ductile Iron Vs Cast Iron, it is possible to make different forms and shapes from ductile iron, as it can be bent. But it is not possible to make any shapes and forms by using cast iron.

Ductile Iron Composition

A typical chemical analysis of this material:

  • Carbon 3.2 to 3.60%
  • Silicon 2.2 to 2.8%
  • Manganese 0.1 to 0.2%
  • Magnesium 0.03 to 0.04%
  • Phosphorus 0.005 to 0.04%
  • Sulfur 0.005 to 0.02%
  • Copper <0.40%
  • Iron balance

Elements such as copper or tin may be added to increase tensile and yield strength while simultaneously reducing ductility. Improved corrosion resistance can be achieved by replacing 15% to 30% of the iron in the alloy with varying amounts of nickel, copper, or chromium.

Properties of Ductile Iron

  1. Ferrite – a pure, ductile, flexible iron with little strength. This matrix has poor wear resistance, but high impact resistance and good machinability.
  2. Pearlite – a mechanical mixture of ferrite and iron carbide (Fe3C). It is relatively hard, with moderate ductility. It has high strength, good wear resistance, moderate impact resistance, and good machinability.
  3. Pearlite/Ferrite – a structure consisting of a mixture pearlite and ferrite, and the most common matrix for commercial grades of ductile iron.

Common Ductile Iron Grades

Physical and Mechanical Properties ASTM A536, Grade 60-40-18 ASTM A536, Grade 65-45-12 ASTM A536, Grade 80-55-06
Tensile Strength, min, psi 60,000 65,000 80,000
Tensile Strength, min, MPa 414 448 552
Yield Strength, min, psi 40,000 45,000 55,000
Yield Strength, min, MPa 276 310 379
Elongation in 2 in. or 50 mm, min % 18 12 6
Density lb/in3 0.256 0.256 0.256
Density g/cm3 7.1 7.1 7.1
Melting Temperature (Degrees F) 2,100 – 2,190 2,100 – 2,190 2,100 – 2,190
Melting Temperature (Degrees C) 1,150 – 1,200 1,150 – 1,200 1,150 – 1,200
Compressive Strength Ksi 429 429 429
Compressive Strength MPa 2960 2960 2960
UNS F32800 F33100 F33800

Ductile Iron Class Production By Foundry

65-45-12 80-55-06 100-70-03
MTA X X
RDI X X X
NF X X X

Table of comparative qualities of cast irons

Name Nominal composition [% by weight] Form and condition Yield strength [ksi(0.2% offset)] Tensile strength [ksi] Elongation [% (in 2 inches)] Hardness [Brinell scale] Uses
Grey cast iron (ASTMA48) C 3.4, Si 1.8, Mn 0.5 Cast - 50 0.5 260 Engine cylinder blocks, flywheels, gearbox cases, machine-tool bases
White cast iron C 3.4, Si 0.7, Mn 0.6 Cast (as cast) - 25 0 450 Bearing surfaces
Malleable iron (ASTM A47) C 2.5, Si 1.0, Mn 0.55 Cast (annealed) 33 52 12 130 Axle bearings, track wheels, automotive crankshafts
Ductile or nodular iron C 3.4, P 0.1, Mn 0.4, Ni 1.0, Mg 0.06 Cast 53 70 18 170 Gears, camshafts, crankshafts
Ductile or nodular iron (ASTM A339) - cast (quench tempered) 108 135 5 310 -
Ni-hard type 2 C 2.7, Si 0.6, Mn 0.5, Ni 4.5, Cr 2.0 Sand-cast - 55 - 550 High strength applications
Ni-resist type 2 C 3.0, Si 2.0, Mn 1.0, Ni 20.0, Cr 2.5 Cast - 27 2 140 Resistance to heat and corrosion

Sources

  • astm.org
  • ductile.org
  • sorelmetal.com
  • wikipedia.org