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Section 3: Ductile Iron

Section 3

Ductile Iron
■ Description of Grades .................3-2 ■ 65-45-12 Ferritic .......................3-3 ■ 80-55-06 Partially Pearlitic ..........3-6 ■ 100-70-02 Pearlitic ....................3-9 ■ 4512 HRDS Heat Resistant ......... 3-12 ■ Stock Listings ........................ 3-14

3-1

Ductile Iron Description of Grades
Ductile iron wasdeveloped in the 1940s and became widely recognized as an engineering material by 1960. The popularity of using ductile iron continues to increase especially with the concern over leaded steels being an environmental hazard. The nodular graphite provides the same free machining benefits as lead (see Fig. 1 & Fig. 2 below) without creating the machining and waste disposal problems. Ductile irons containType I & II nodular graphite, as defined in ASTM A247, in a matrix of pearlite and ferrite. The spheroidal shaped graphite maximizes the strength in cast iron. The ratio of ferrite to pearlite in the matrix is altered for each of the three grades in order to produce the required values for tensile strength, yield strength, and elongation. The ductile iron grades will conform to those listed under ASTMA536, with the primary difference being the high nodule count and fine grain size inherent to the DuraBar continuous casting process. Mechanical properties for each grade are guaranteed in the actual bar, not a separately cast test sample. The different grades are produced by controlling the matrix structure around the graphite nodules. Minimum tensile strengths range from 65,000-100,000 psi, withcorresponding minimum elongation requirements from 2-12%.

Fig. 1 (Left) Photo of 12L14 steel (200x, etched in 5% Nitol). Lead particles can be seen to be spheroidal in shape & uniformly distributed throughout the structures.

Fig. 2 (Right) Photo of Dura-Bar 65-45-12 ductile iron (100x, etched in 5% Nitol). Graphite nodules are uniformly distributed throughout the structure providing thesame free machining characteristics inherent to leaded steels.

3-2

Color Code: Yellow

65-45-12 Ferritic Ductile Iron 65-45-12 Ferritic Ductile Iron
General Description
Dura-Bar 65-45-12 ductile iron contains nodular graphite in a matrix of ferrite with small amounts of pearlite. The ferritic structure gives excellent machinability with good surface finishes along with optimal impactstrengths, fatigue properties, electrical conductivity and high magnetic permeability. This iron has approximately the same tensile and yield strengths as AISI 1020 steel in the as-rolled condition. This specification conforms to ASTM A536 grade 65-45-12.

Contents 65-45-12 Ferritic Ductile Iron3

Microstructure
The microstructure consists of Types I and II nodular graphite as defined in ASTM A247.The matrix is ferrite with approximately 5-25% pearlite. The “rim” will have a higher nodule count and will be mostly ferrite. Chill carbides will be less than 5% in any field at 100x and will be well dispersed.
Fig. 1 (Left) Typical microstructure in the center area (100x, etched in 5% Nitol) Fig. 2 (Right) Typical microstructure in the rim area (100x, etched in 5% Nitol)

Chemical CompositionThe chemical analysis is subordinate to the mechanical properties. Typical analysis will be as shown in Table 1 on the next page.
Table 1 65-45-12 chemical composition.

Element Carbon1 Silicon1 Manganese Sulfur Phosphorus

Percentage 3.50-3.90% 2.25-3.00% 0.15-0.35% 0.025% max. 0.05% max.
3-3
1

Carbon and silicon targets are specified for each bar size in order to maintain mechanicalproperties.

65-45-12 Ferritic Ductile Iron
Mechanical Properties
Hardness properties for various diameters are shown in Table 2 below. Hardness properties listed are minimum, maximum across the bar. For rectangles, squares and shapes, the hardness properties will depend on minimum and maximum section thickness and will be supplied on request.
Table 2 65-45-12 hardness properties

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