Advantages and disadvantages of stainless steel casting process

Everyone in the casting industry knows a fact. That is the mechanical properties of stainless steel casting are higher than that of cast iron, but its casting performance is worse than that of cast iron. Stainless steel casting belongs to investment or precision casting, with relatively high melting point. The molten steel is easily oxidized, due to poor fluidity and large shrinkage rate. From a practical perspective, stainless steel casting is suitable for casting of various types and alloys.

Advantages and disadvantages of the stainless steel casting process are as below:

First, due to the poor liquidity of the molten steel, the wall thickness of the steel castings should not be less than 8 mm, in order to prevent the cold shut and misrun. The structure of the pouring system strives to be simple, and the sectional dimension is larger than that of cast iron. Adopt dry casting or hot casting, and the casting temperature should be appropriately increased to 1520-1600 ℃. The fluidity can be improved since the casting temperature is high with large superheat, thus the liquid stays for a long time.

However, if the pouring temperature is too high, it will cause defects such as coarse grains, hot cracks, pores and sand burning. Therefore, the casting temperature of small, thin-walled and complex casting should be at the melting point +150 ℃; and of large, thick-walled casting +100 ℃.

We must take these measures to prevent the occurrence of shrinkage holes and cracks in stainless steel castings. 1. Making the wall thickness uniform, and avoid sharp and right angle structures, 2. Adding sawdust to sand mold, and coke to sand core. 3. Adopting hollow sand core and oil sand core to change the deformability and permeability of the sand mold and core.

The density of ductile cast iron is approximately 7.3 g/cm3, or 7.3 kg/liter, or 119.6 g/cm3. However, due to the material grade and shrinkage level, the density has a certain range of variation.

In other words, if the quality of pig iron used by the iron foundry is better and the shrinkage rate is smaller, then the density of ductile iron will be higher. Otherwise, the density of ductile iron will be lower. Therefore, it ranges from 7.1 to 7.3 g/cm3.

Iron foundries usually estimate the weight of rough castings by calculating the volume of ductile iron, so the density will be used. However, you cannot judge the quality of castings by density alone.

There are more factors that will affect it, such as spheroidization rate and cooling rate. Hence, it will be reasonable within this range.

EN-GJS-500-7 Ductile Cast Iron GGG50

EN-GJS-500-7 is the middle grade of ductile cast iron in European standard DIN EN 1563.

It is equal to GGG50 in DIN 1693, QT500-7 in China, A536 70-50-05 in USA ASTM, GS500-7 in Italy, FCD500 in Japan, FGS500-7 in France, G500/7 in India, FGE50-7 in Belgium, SJK-500 in Norway, and ISO 500-7.

Now, let me introduce its mechanical properties, chemical composition, foundries and castings to you.

Mechanical Properties of EN-GJS-500-7

Tensile strength ≥ 500 Mpa.
Yield strength ≥ 320 Mpa.
Elongation ≥ 7%.
Hardness range: Brinell Hardness 170-230.
No impact requirement.

The tensile strength and elongation are the key inspection standard for qualification. Iron casting buyers could judge unqualified castings according to these two parameters. Hardness can not be taken as quality evaluation data unless you have special requirements.

Chemical Composition of EN-GJS-500-7

The normal chemical composition for this grade is as the following:

C: 2.7-3.7.
Si: 0.8-2.9
Mn: 0.3-0.7
P: ≤0.1
S: ≤0.02

The chemical composition has a big difference in different standards. All compositions are just for reference. The international standards stipulate that the manufacturers could adjust their chemical composition according to their experience and production conditions, as long as their material could meet the mechanical properties.

Production Foundries of EN-GJS-500-7

EN-GJS-500-7, or called cast iron GGG50, is a very common and normal cast iron grade. Most the iron foundries in China could produce this material. So, it is not difficult to find a foundry who could produce it, but just difficult to find one who could produce it very well. In other words, consistent quality is always important.

Main Casting Products of EN-GJS-500-7

There are many ductile casting products using this grade, such as iron brackets for trucks, tractors, other agricultural and construction machinery. The followings are some casting products manufactured by Yide Casting foundry.