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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:


Hardness range and Brinell indentation diameter 



HB187 maximum
4.4BIDminimum or by agreement

Ferrite - pearlite


4.6-4.0BID or by agreement

Ferrite - pearlite


4.4-3.9BID or by agreement



4.2-3.8BID or by agreement



4.1-3.7BID or by agreement


The grade and hardness requirements of round brake and clutch hub under heavy load are as follows:


Carbon, minimum%

Hardness and indentation diameter



HB170-229 4.6-4.0BID or by agreement



HB207-255 4.2-3.8BID or by agreement



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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