This guide will help gray cast iron buyers understand how to select the appropriate gray cast iron material grades for their casting products.

1. Which grey cast iron grades can you choose?

The table below shows all gray iron material grades in each country. So, if you are American, then you can choose No. 20, 30, 35 or 45, etc. If you are Australian, then you can choose T150, T220, T260 or T300, etc.

2. What is the role of material grade?

The material grade comes from its specific material standard. For example, in the United States, the general material standard for ductile iron is ASTM A48. In this standard, you can find No.25 mechanical properties with the minimum tensile strength. 172 Mpa, No. 30 tensile strength 207 Mpa.

Therefore, when you tell us what material grade you need, we will know what mechanical properties you need, and then we can produce your castings accordingly.

3. How to choose the right grade of gray iron?

Choosing a gray iron material grade is a very professional job. Usually only a professional material engineer can choose the right grade. However, if you are not a material engineer but have to make a choice, then the following methods may help you.

• A. Please check the two-dimensional drawing, as well as your technical requirements, and then you may find some clues about the “material”, the finished drawing should indicate the material grade.
• B. If you cannot find any important information in the drawings, you may need to consider it based on your experience. The following experience will help you.
• B1. If you only need gray cast iron or cast iron and have no special requirements on its mechanical properties, you can choose “No.20 or No.25” (the equivalent grades in other countries are GG15, EN-GJL) -150, T150, 150 , HT150). The material equivalent table above will help you.
• B2. If the material needs high strength, high strength, and can withstand larger load forces, you can choose “No. 30” or higher grade “No. 35” (for equivalent grades, please refer to the material grade table above)).
• B3. If you need materials with very high strength, need to withstand very high pressure loads, and need to be very strong, then you can choose “No.40” or “No.45”.

On this point, let me explain. For some products, such as stove parts, high material grades will bring some difficulties to further drilling work, so do not require high grades for these parts, higher grades will lead to higher production costs and higher defect rates. So unless you really need it, the lower grades will be better used for casting production.

4. Some important issues in choosing gray iron material grades

For most foundries in China, we can produce low and medium gray cast iron material grades, but not everyone can produce high gray cast iron grades, such as No. 50 or No. 60. They need further heat treatment, so if you need very high resistance Tensile strength, but does not require the special mechanical properties of gray cast iron, and nodular cast iron material can be considered, which is stronger and tougher than gray cast iron.

If you still cannot make a good choice, then you can seek the help of some material engineers, or tell us your requirements. You just need to tell us where your parts will be used and what your application requirements are, and then we will give you our suggestions.

Commonly, grade GG10 cast iron is the lowest grade in standard DIN 1691.

Today, YIDE Casting gives you some examples of DIN 1691 GG10 gray cast iron applications for your reference.

For small loads, the friction and wear no special requirements for important casting, such as protective cover, cover, oil pan, hand wheels, frame, floor, hammer, small handle, counter weights etc.

Physical Properties of DIN 1691 GG10 Gray Cast Iron

Density ρ 6.8 – 7.8 g/cm³ at 20 °C Typical for Cast Iron

Mechanical Properties of DIN 1691 GG10 Gray Cast Iron

Shear modulus G 41 GPa at 20 °C Typical for Cast Iron
Tensile strength Rm 100 MPa at 20 °C

Equivalent Material Grades

The comprehensive mechanical properties of gray cast iron are low, due to the presence of flake graphite. The metal matrix structure is split and the effective area of ​​load-bearing is reduced. However, the gray iron castings’ vibration damping, wear resistance, castability and machinability are better.

If the gray iron casting is too hard to machine during processing, we recommend the following inspection and rescue methods:

1. If the manganese content is too high, the surface of gray iron castings will be hard. Therefore, It is necessary to check the chemical composition.
2. The gray iron casting will be hard if the thin-walled cooling process is too fast.
3. Due to the relatively high hardness of gray iron castings, choosing a reasonable tool is necessary. You can use G8 for rough machining, G6 for semi-finishing, and G3 for finishing. It is also necessary to select the appropriate speed and feed rate.
4. Annealing treatment can eliminate the hardness of the casting itself, and lower the hardness of the casting as well. 

Yide Casting provides gray iron castings parts for kinds of industry, high attention to producing the qualified and high-quality casting parts according to the requirements from our customers, all of our casting products can be checked after selling. We provide both casting and machining by ourselves, has our own casting workshop and machining workshop, and we also have long term cooperator to do complex machining. If you are looking for a professional casting foundry, please don’t hesitate to contact us for a quick quote, and you are also welcome to visit our factory for better work.