GB 1348-88 Alloyed Ball/Pearlitic Ductile Iron Castings
Chinas national standard, GB 1348-88, defines the requirements for alloyed ball/pearlitic ductile iron castings. Ductile iron is an iron-carbon alloy in which carbon is added along with manganese, nickel and silicon to the base iron. The greater carbon content gives ductile iron superior strength and greater impact resistance compared to gray iron. The alloyed ball/pearlitic ductile iron described in GB 1348-88 generally contains between 2 and 4.50% carbon, 1.00 to 2.00% silicon, 0.2 to 0.7% manganese, and 0.5 to 1.5% nickel.
The material is roughly divided into three grades based on the amount of nickel and silicon used in the alloy: GGG40, GGG50, and GGG60. The GGG40 grade has 2 to 4.50% carbon, 1.00 to 2.00% silicon, 0.2 to 0.7% manganese, and 0.50 to 1.50% nickel. The GGG50 grade has less silicon and nickel than the GGG40 grade, with 1.00 to 2.00% carbon, 0.5 to 1.5% silicon, 0.5 to 1.0% manganese, and 0.2 to 1.0% nickel. Meanwhile, the GGG60 grade has the lowest amounts of nickel and silicon, with 1.0 to 2.0% carbon, 0.2 to 0.6% silicon, 0.3 to 0.8% manganese, and 0.2 to 0.7% nickel.
The great advantage of alloyed ball/pearlitic ductile iron castings is that the material is strong and wear-resistant, yet ductile and shock-resistant. Ductile iron is well suited for the manufacture of various castings such as automotive, agricultural, marine and industrial components due to its superior strength, high casting accuracy and long-service life.
As defined in GB 1348-88, the chemical and mechanical requirements for ductile iron castings must meet the following specifications: sulfur content ≤ 0.030%, phosphorous content ≤ 0.040%, tensile strength ≥ 400MPa, elongation ≥ 12%, hardness ≤ HB180, and Brinell hardness ≤ HB220. In addition, all castings must have their surfaces free of scale, slag inclusion, and any other foreign impurities.
To ensure the manufacture of high-quality products, GB 1348-88 also requires nondestructive testing such as magnetic particle testing and/or radiographic inspection of all castings. The use of glass flake inspection is also specified when required by the design requirements and/or the casting surface conditions.
In conclusion, GB 1348-88 specifies the requirements to be met for the manufacture of alloyed ball/pearlitic ductile iron castings. This national standard ensures that ductile iron castings manufactured in China possess high strength, good wear resistance, and excellent surface finish and dimensional accuracy.
