Ductile Cast Iron Hardness Requirements
1.
Ductile iron castings
(ASTM A536-84)
Ductile iron
is a very good material for
metal castings, this kind of
cast iron has globular graphite, and basically has no other form of
graphite. The iron casting grade is represented by "tensile strength
- yield strength - elongation", For example:
Grade: 80-55-06. It
means the tensile strength is 80,000 pounds / inch 2 (552MPa), the
yield strength is 55,000 pounds / inch 2 (379MPa), and the
elongation is 6.0% (2 inches or 50mm).
The ductile iron
castings should be heat-treated appropriately, such as annealed,
normalized, quenched and tempered. There are certain provisions in
the contract or purchase order, the castings should meet the
requirements as hardness, chemical composition, and microstructure
and so on.
2.
Austenitic ductile iron castings (ASTM A439-89)
They are mainly used
as heat resistance, corrosion resistance and wear resistance
castings. The castings should be stress-eliminated, stabilized, heat
treated or annealed. The casting hardness requirements are as
follows:
|
Property |
Grade |
|
D-2 |
D-2B |
D-2C |
D-3 |
D-3A |
D-4 |
D-5 |
D-5B |
D-5S |
|
Property |
|
Tensile strength, not less than thousands of pounds / inch 2
(MPa) |
58 (400) |
58 (400) |
58 (400) |
55 (379) |
55 (379) |
60 (414) |
55 (379) |
55 (379) |
65 (449) |
|
Yield strength (0.2% residual elongation), no less than
thousands of pounds / inch 2 (MPa) |
30 (207) |
30 (207) |
28 (193) |
30 (207) |
30 (207) |
… |
30 (207) |
30 (207) |
30 (207) |
|
2 inches or 50mm elongation, no less than, % |
8.0 |
7.0 |
20.0 |
6.0 |
10.0 |
… |
20.0 |
6.0 |
10 |
|
Brinell hardness HB (3000 kg) |
139-202 |
148-211 |
121-171 |
139-202 |
139-193 |
202-273 |
131-185 |
139-193 |
131-193 |
3.
Austempered ductile iron castings
(ASTM A897M-90)
They
are used for ductile iron castings which need austempering heat
treatment. Austempering can narrow the mechanical properties between
different parts of the same area or castings cast from the same
furnace hot metal.
The
application of austempering heat treatment can increase the
performance range available on the ductile iron parts. The
mechanical property requirements of different grades of castings are
as follows:
|
|
Grade
850/550/10 |
Grade
1050/700/7 |
Grade
1200/850/4 |
Grade
1400/1100/1 |
Grade
1600/1300/- |
|
Minimum tensile strength, MPa |
850 |
1050 |
1200 |
1400 |
1600 |
|
Minimum yield strength, MPa |
550 |
700 |
850 |
1100 |
1300 |
|
Elongation (50 mm) minimum,% |
10 |
7 |
4 |
1 |
… |
|
Impact energy, Bajaur |
100 |
80 |
60 |
35 |
… |
|
Typical hardness, Brinell hardness HB |
269-321 |
302-363 |
341-444 |
388-477 |
444-555 |
4.
The
ferrite ductile iron castings used for high pressure
(ASTM A395 M-88)
They are
used
for high pressure ductile iron valves, flanges, pipe fittings, pumps
and other pipe fittings. The order contract should include the heat
treatment requirement.
The hardness of castings and the specimen should be within the
following range: Brinell hardness, 3000kg force / 10mm ball,
HB143-187.
The
casting hardness requirements are as follows:
|
1
1
1
1
2
2
2
3 |
A
B
C
D
A
B
C
A |
Ni-Cr-HiC
Ni-Cr-LoC
Ni-Cr-GB
Ni-HiCr
12%Cr
15% Cr-Mo
20% Cr-Mo
25% Cr |
550
550
550
500
550
450
450
450 |
600
600
600
600
600
600
600
600 |
650
650
650
650
650
650
650
650 |
600
600
600
550
550
…
…
… |
…
…
400
…
400
400
400
400 |
8(200)
8(200)
3(75) ball diameter
12 (300)
1 (25) ball diameter
4 (100)
8 (200)
8 (200) |
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