| Cast iron generally means grey cast iron, but | | | | added to the melt prior to the final form |
| is identifies a group of ferrous alloys which | | | | being made by casting. |
| solidify with a eutectic. | | | | |
| | | | Iron is generally melted in a small blast |
| Overview: | | | | furnace called cupola. After melting is over |
| | | | the melted iron is ladled from the forehearth |
| Iron accounts for more than 95% the alloy | | | | of blast furnace. This system was developed |
| material, while the main alloying elements | | | | by the Chinese whose innovative ideas brought |
| are carbon and silicon. The amount of carbon | | | | revolution in field of metallurgy. Before |
| in cast iron is 2.1-4% while ferrous alloys | | | | that iron was melted in an air furnace, which |
| with less carbon are called carbon steel by | | | | is a type of reverberatory furnace. |
| definition. Cast iron has appreciable amount | | | | |
| of silicon normally 1.3%. Therefore, these | | | | Some advantages of cast iron in engineering |
| alloys should be considered ternary Fe-C-Si | | | | uses:a) A family of metals having capacity of |
| alloys. | | | | being used for engineering and production |
| | | | needs.b) You can have it in a wide range of |
| In spite of this, the principles of cast iron | | | | mechanical and physical properties.c) Good |
| solidification are understood from the binary | | | | strength to weight ratio.d) Generally cheaper |
| iron carbon phase diagram, where the eutectic | | | | than other competing metals and lower |
| point lies at 1154 °C and 4.3 wt% carbon. | | | | financial cost per unit of strength compared |
| Because cast iron has this composition, its | | | | to other metals.e) Lesser density and higher |
| melting temperature of 1150 to 1200 °C is | | | | thermal conductivity then steels at |
| about 300 degrees less than the melting point | | | | comparable tensile strength levels.f) Easily |
| of pure iron. Cast iron tends to be brittle, | | | | mechniable, allows high speeds and feeds and |
| though the name of particular alloy may | | | | less energy due to free graphite being |
| suggest opposite. The color of a fracture | | | | presence.g) Many iron castings may be |
| surface may be utilized to identify an alloy; | | | | utilized without heat treatment (as cast) but |
| carbide impurities allow cracks to pass | | | | when required may be heat treated to increase |
| straight through resulting in a smooth | | | | overall properties or local property like |
| "white" surface, while graphic flakes deflect | | | | surface hardness.h) Very good damping |
| a passing crack and initiate countless new | | | | capability especially in grey irons.i) |
| cracks as the material breaks, leading to a | | | | Chemical analysis may be changed to give |
| rough surface that looks grey with its low | | | | improved special properties like corrosion |
| melting point, good fluidity, castability, | | | | resistance, oxidation and wear resistance.j) |
| excellent machinability and wear rising | | | | Quickly changes from design to finished |
| resistance, cast irons have become an | | | | goods.k) Capable of having highly complex |
| engineering material with a wide range of | | | | sizes from ounces to 100 tons.l) Of flexible |
| uses like pipes, machine and auto parts. | | | | pattern and capacity to improve appearance |
| | | | for sales appeal.m) You can make intricate |
| Products: | | | | shapes as well as very thin to very thick |
| | | | sections.n) Capable of redesigning and |
| Cast iron is produced by remelting pig iron, | | | | combining two or more parts from metals into |
| normally with large quantities of scrap iron | | | | a single casting thereby lessening assembly |
| and steel and initiating steps to remove | | | | cost and time.o) Capable of being cast with |
| unwanted contaminants like phosphorus and | | | | inserts of other metals.p) Many casting |
| sulfur. Depending on use carbon and silicon | | | | systems for low, medium or high production.q) |
| content are lessened to the required levels | | | | Less tendency toward residual stress and |
| which may be anywhere from 2% to 3.5% and 1% | | | | warpage than other competing metals. |
| 3% respectively. Other elements are then | | | | |