What is Iron Casting Process?

 

What is Cast iron?

Cast iron is a ferrous alloy of iron, carbon, and silicon. With carbon content of 2.1 to 4.5 % and silicon at about 2.2% and a small amount of Sulphur, Manganese and Phosphorous.

Iron casting is one of the oldest casting methods in the world. The cast iron is melted and poured into molds or casts to make a part of products of desired size and shape. Cast iron can be used in a range of industries. In the Manufacturing Process of Cast Iron, the alloying elements determine cast iron type. Compared with steel casting, iron casting has a wide range of advantages of its properties.

 

The Advantages of Iron Cast

1. Good machinability (graphite cast irons)

2. Excellent anti-vibration (or damping) properties hence it is used to make machine frames

3. Strong compression strength compared to steel

4. Low Cost

5. Excellent resistance to wear

6. Good Sensibility

7. Very low notch sensitivity

8. Constant Mechanical properties between 20 to 350 degrees Celsius

9. Durability, Resistance to deformation

10. Low-stress concentration

11. Good casting properties(low Tm, good fluidity). It can be given any complex shape and size without using costly machining operations

 

Iron Casting Process

Like other investment castings, there are also different producing methods of iron castings. There are 2 main methods for iron casting: sand casting or lost foam casting method.

 

Lost foam casting

Lost foam casting is another casting technique for iron castings. It is a type of evaporative-pattern casting process that is like investment casting. But replace the wax with foam for the pattern. The advantage of lost foam casting is that the boiling point of foam is low. This helps to simplify the investment casting process by removing the need to melt the wax out of the mold. Cast iron is one of the commonly cast materials in the lost foam casting process.

With lost foam casting, we can make small iron castings with good dimensional accuracy and surface finish. For large iron castings, sand casting is the primary choice.

 

Sand Casting

Also called sand molded casting. Is the process that utilizes non-reusable sand molds to form metal castings. Sand casting is used to produce a wide variety of cast iron components with complex geometries. In China, there are three types of sand casting techniques to make iron castings. They are precoated sand casting, resin sand casting, and clay sand casting.

Among them, precoated sand casting is the most precision sand casting process with general casting tolerance CT8. It can produce iron castings less than 2kgs. Clay sand casting is the second precision casting process with general casting tolerance CT9. Iron castings between 2kgs-60kgs are available in this method. And resin sand casting is mainly used for the production of large iron castings above 60kgs.

The types of Iron Cast

The Iron Cast main types are Grey Iron, Ductile Iron, Compacted graphite, White, Malleable, Abrasion-resistant, Nodular or spheroidal, Austenitic. Here we make a brief introduction in the below table.

Types	Properties
White cast iron: Carbon is present here in the form of Iron carbide (Fe3C).	High compressive strength Difficult to machine Good hardness Resistance to wear
Gray cast iron: Carbon here is mainly in the form of graphite. It is inexpensive.	Good machinability Good resistance to galling and wear High compressive strength Brittle
Ductile cast iron	High ductility High strength
Malleable cast iron They are made malleable with the help of annealing. They are used to make parts where forging is expensive like brake supports, hubs of wagon wheels, etc. They are inexpensive.	High ductility Tougher than gray cast iron Be twisted or bent without fracture Excellent machining capabilities
Nodular or spheroidal cast iron Here graphite is present in the form of spheres or nodules.	High tensile strength Good elongation properties

 

The applications of Iron Casting

The iron cast is the main raw material for Iron casting. It has wide applications.

1. Automotive parts

2. Cookware and utensils

3. Making anchor for ships

4. Stoves and firebacks

5. Cast Iron Piping Pluses

6. Engine Block Comeback

7. Hardware, hinges, latches

8. Columns, balusters,Stairs

9. Decorative features,Fences

10. Tools and utensils

The common Cast Iron used for Iron Casting and standards:

Cast Iron Standards	GB	AWS	BS	NF	DIN	ISO
Grey Iron	HT200	No.30	Grade 220	EN-GJL-200	GG20	200
Grey Iron	HT250	No.35	Grade 260	EN-GJL-250	GG25	250
Grey Iron	HT300	No.45	Grade 300	EN-GJL-300	GG30	300
Grey Iron	HT350	No.50	Grade 350	EN-GJL-350	GG35	350
Ductile Iron	QT450-10	65-45-12	GGG-40	EN-GJS-450-10	450/10	450-10
Ductile Iron	QT450-18	60-40-18	GGG-40	EN-GJS-450-18	400/18	450-18
Ductile Iron	QT500-7	80-55-06	GGG-50	EN-GJS-500-7	500/7	500-7

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