Gray Iron Castings Hardness Requirements
1. Gray iron castings (ASTM A48-92)
They are used as the general engineering
gray iron castings which
take tensile strength as the main consideration, and are classified
into different grades according to the tensile strength of different
test bars. For this type of iron
castings, the chemical composition is secondary compared to
the tensile strength.
During ordering or production process, the castings are divided into
a number of grades according to a separate sample performance, each
grade is represented by a number followed by a letter, the number
indicates the minimum tensile strength of test bars in individual
casting, and the letter shows the specifications of test bars.
For example:
Gray iron casting, grade ASTM A48,
30B is produced according to standard ASTM A48, and the minimum
tensile strength is 30 thousand pounds / inch 2 (207MPa), and the
nominal test bar diameter is 1.2 inches (30.5mm).
It is addressed in standard as "when the foundry and the purchaser
reach a written agreement, to require castings to meet the hardness,
chemical composition, microstructure, pressure leakage, and X-ray
inspection and defect-free, size, Surface accuracy and other
requirements are necessary."
2. Gray iron castings for motor vehicle (ASTM A159-88)
They are used as sand molded grey iron castings in cars, tractors
and related industries.
The order contract should include the following terms:
• The need for special heat treatment.
• The surface of the hardness test.
• The required surface hardening depth and hardness.
Hardness requirements:
The Foundry should take the necessary control and inspection
techniques to ensure the compliance with specified hardness range.
Brinell hardness is tested according to ASTM E10 test method, and
test after the thickness of the material on casting surface has been
removed, which can ensure the representation of the hardness
readings. Unless there are some other agreements, we should use 10
mm steel ball and 3000 kg load. The hardness testing areas and the
location should be negotiated by both the supply and the demand
parties, and notified in the drawing.
Gray iron grades,
hardness range, the millimeters and metallurgy description
of Brinell indentation diameter (BID) got from a 10 mm ball, 3000 kg
force are as follows:
Grade |
Hardness range and
Brinell indentation diameter |
Description |
G1800 |
HB187 maximum
4.4BIDminimum or by agreement |
Ferrite - pearlite |
G2500 |
HB170-229
4.6-4.0BID or by agreement |
Ferrite - pearlite |
G3000 |
HB187-241
4.4-3.9BID or by agreement |
Pearlite |
G3500 |
HB207-255
4.2-3.8BID or by agreement |
Pearlite |
G4000 |
HB217-269
4.1-3.7BID or by agreement |
Pearlite |
The grade and
hardness requirements of round brake and clutch hub under heavy load
are as follows:
Grade |
Carbon, minimum% |
Hardness and
indentation diameter |
G2500a |
3.40 |
HB170-229 4.6-4.0BID
or by agreement |
G3500b |
3.40 |
HB207-255 4.2-3.8BID
or by agreement |
G3500c |
3.50 |
HB207-255 4.2-3.8BID
or by agreement |
The grade of gray
iron alloy camshaft motor vehicle is G4000d, the casting hardness -
in accordance with both the supply and demand sides, measured in the
support surface is 241-321HB.
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