It is estimated that the iron casting method first started in China in the 300s BC, during the Khan Dynasty, by pouring molten iron into molds at temperatures above 1,400°C. It is understood that the iron age reached Europe through the Balkans through trade channels and from Anatolia with its iron furnaces and craftsmanship. In other words, Anatolia has served as the cradle of all cultures and has also preserved its status as the oldest in foundry industry. During the Çatalhöyük excavation near Konya Çumra, it was determined that mining was carried out in Anatolia around 6000 BC.
The highest tonnage product of the foundry industry is cast iron. The fact that cast iron is a good material and has a low production cost expands its usage area. Cast irons have a wide range of varying strength, hardness, machinability, wear resistance, corrosion resistance and other properties.
Cast iron is a fluid material that melts at low temperatures, obtained by reducing the carbon of raw iron obtained from a blast furnace to 1.7% to 3% by burning it in cupola furnaces. The melting temperature is approximately 1250°C. Its tensile property is %k=1~2, its density is 7.2–7.4 g/cm3. It contains Carbon (C), Silicon (Si), Manganese (Mn), Sulfur (S) and Phosphorus (P). Since cast iron contains silicon as well as carbon and the cooling rate is slow, carbon solidifies into graphite during solidification. Cast iron is a family of iron alloys that contain many different properties, and as their name suggests, they are not worked in solid state but are cast into the desired shape. Other metallic and nonmetallic alloys are added to control and vary certain properties.
Casting products are used as an input in most industries. So much so that 90% of industrial products contain at least one casting product. In other words, the Turkish casting industry; It is one of the cornerstones of the Turkish manufacturing industry. At the same time, it is able to meet all production demands, especially machinery, transportation vehicles and defense industry, from design to prototype, tests and final products.
Despite the competition from new materials, cast irons have proven to be economical and suitable for thousands of engineering applications. Cast irons have a wide range of uses due to their low cost, castability and high compressive strength. If there is no other additive element, cast iron contains at least 1.7% carbon. If there is less than 1.7% carbon in the texture, the material is not cast iron. The carbon content may be lower when impurities and additives are present in cast iron.
With technological developments, small parts instead of large parts have become more functional and assembleable. For example, when we count the elements in the materials, there are 10-15 thousand materials in a CNC machine, 15-20 thousand in a tractor, 20-25 thousand in an automobile, 40 thousand in a tank, 100 thousand in an airplane and 120 thousand in a submarine. Each of these complex systems, where many materials are brought together, performs important tasks. Therefore, it is very important to choose these materials correctly and in accordance with the conditions in their location. Otherwise, the part of the system in question may break during operation and cause loss of life and property.
The ability of machine parts to perform their functions is also related to their features. In order for a technical staff to choose the right material, he/she must have knowledge of the internal structure of the materials and their manufacturing methods.
When choosing the material; The structure of the material, its specific gravity, its heat of melting, its electrical and thermal conductivity, whether it will be used in a low or high temperature environment, the forces on the material, the availability of the material, its suitability for workmanship, its physical, mechanical and technological properties, its economy, its resistance to internal and external effects, what it is used for in production. Factors such as the methods to be used should be taken into consideration.
The suitability of the materials for the place they are used is also extremely important. Thanks to appropriately selected materials, machines, benches and machine parts will be longer lasting and safer.
When we specifically consider the manufacturing of all kinds of pulleys, fan fasteners, couplings, bushings and bearing housings, which are the final products of Ünsal Makina manufacturing,
Resistance
ductility
Stability
Manufacturability
availability
corrosion resistance
Main items such as heat transfer properties must be reviewed.
Although our products are generally produced as "cast iron", we also perform "ductile iron" casting depending on the place of use and technical need.
Whether it is cast iron, ductile iron or steel, the main material of all of them is raw iron. Raw iron is strengthened by making it an alloy by adding "carbon" into it. They acquire different material structures and take different names depending on the preferred carbon ratio or distribution patterns of carbon atoms.
These products have international standard representations. By looking at these codes, we can understand what is used in the pulley casting and how much tensile force it withstands. For example, for a pulley we see GG20 or GJL 200. This shows us that the pulley is cast iron and produced with a tensile strength of 200 N/mm². Apart from this, spheroidal castings are referred to as GGG or GJS. Although GJL 200 casting (GG20) quality is applied as standard, the need and demand for GGG40 GGG50 production is increasing rapidly depending on the functions of the machines and elements used. So why?
Ductile iron has a structure consisting of spherical graphite dispersed in a matrix similar to that of steel. Its difference from cast iron in terms of microstructure is the shape of the graphite.
The main advantages of ductile iron over cast iron are its low melting point, good fluidity, good castability, excellent machinability and good shear strength. While the ductile iron product is similar to steel casting in terms of its mechanical properties, it is a special material that has the character of cast iron in terms of its production method.
Although the chemical compositions of cast iron and ductile iron are essentially the same (except for sulfur and magnesium), these two cast irons solidify quite differently. This difference also changes the mechanical properties of the material. As seen in the table below, ductile iron products have superior properties to GG25 in terms of mechanical properties such as tensile strength, elastic modulus and impact quenching.
Considering the superior properties of ductile iron, it can be seen numerically that both the production and therefore the export of the ductile iron curve has increased many times over the years, as seen in the 2 tables below. It has a structure consisting of spherical graphite dispersed in a matrix similar to that of ductile iron steel. Its difference from cast iron in terms of microstructure is the shape of the graphite.
The main advantages of ductile iron over cast iron are low melting point, good fluidity, good pourability, excellent machinability and good shear strength. While the ductile iron product is similar to steel casting in terms of its mechanical properties, it is a special material that has the character of cast iron in terms of its production method.
Although the chemical compositions of cast iron and ductile iron are essentially the same (except for sulfur and magnesium), these two cast irons solidify quite differently. This difference also changes the mechanical properties of the material. As seen in the table below, ductile iron products have superior properties to GG25 in terms of mechanical properties such as tensile strength, elastic modulus and impact quenching.
As can be seen in Table 4, the percentage of ductile iron exports in the production figures of the Turkish foundry industry, which was 2% in 1982, increased to 36%.
We would like to state that we are aware of this and that we provide the necessary engineering support to our customers free of charge. This support can be provided by our team of 15 engineers who are experts in their fields and an automatic molding / casting line. This can be easily seen in our GGG40 and GGG50 productions, which have increased by 200% in recent years.
writers
Sümeyye Çavdarcı, Industrial Engineer, Ünsal Makina
Belma Karatürk, Industrial Engineer, Ünsal Makina
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