01-09-2012, 01:54 PM
SAND MOULD CASTING
SAND MOULD CASTING FINAL.docx (Size: 217.26 KB / Downloads: 88)
OBJECTIVE OF THE STUDY
To know about sand mould casting with reference to construction of an axle pulley of alternator and to compare green sand moulds and carbondioxide moulding process.
RATIONALE OF THE STUDY
Sand casting is a process of casting in sand moulds.There are several different types of casting sand and the process can vary greatly in scale from casting multi ton parts for industrial machines to casting items as small as a ring.
So the fundamental reason behind to this topic is to make clear understanding of the sand mould casting process and to find out the advantages of CO2 casting over green sand mould casting.It needs a thorough analysis on this topic sand mould casting.
METHODOLOGY OF THE STUDY
The sand mould casting process is one in which moist sand is packed round a wooden or metal pattern to make a mould.The pattern is then removed and the mould is used to make a cavity.Molten metal is then poured and when metal soldifies and cools the mould is broken and casting is removed.
And these technichal details can be easily found through technichal article magazines.So I mainly focus the above for the collection of datas for this study.Engineers in a foundry of the industry helped me to find out these details.
STATEMENT OF THE PROBLEM
Alternator of axle pulley is used in rail coaches for driving the dynamo for train lighting.
Here I analyse the sand mould casting with reference to construction of axle pulley of alternators.
The bonding agent is a material used as an additive to mould or core sand to impart strength or plasticity.This strength of green sand and co2 sand are different.Here I have been trying to find out the advantages of one over the other.
Crucible handling tools
When the crucible is glowing hot, with a load on molten metal in it one has to be able to pick it up out of the furnace and pour the metal in to it, A crucible gets a little soft at these temperatures.It is better to have some special tongs that go around the crucible and hold it firmly from several contact points.Crucible handling tools are shown in figure 3.
The moulding machine
For small parts to cast hand moulding is enough.For the construction of alternator pulleys and other larger parts a jolt moulding machine is employed.In jolt moulding machine,the patterns and flask are mounted on a mould plate and flask is filled with sand.Then the entire assembly is dropped against a fixed stop.
The impact compress the sand.The compacting is achived by deaccelerating forces acting on it.The prepared sand mixture is then compressed around the pattern at specific temperatures and pressure and finally cope and drag are prepared.
The furnace
A furnace is what makes the heat for melting metal.It is constructed from light weight fire brick, cut to fit and banded in to an octagon with fiber frax (a refractory fiber) gaskets to seal between the bricks (not absolutely necessary but nice).The ‘flamethrower’ part of the furnace began with a salvaged electric leaf blower.Then made a steel pipe nipple for the business end.Crucible in a furnace with a recycled leaf blower is shown in figure 4.
Pouring of molten metal
The molten metal is maintained at a set temperature in furnace.After the mould has been clamped and molten metal is poured by using laddle from its holding container in furnace and poured by means of an automated machine.Figure 11 is a mould ready to pour.
Cooling curve
Cooling curve is important in controlling the quality of casting.The most important part of the cooling curves is cooling rate which affects the micro structure and properties.Casting which is cooled quickly will have fine grain structure and properties.Casting which is cooled quickly will have fine grain structure and area which cool slowly will have coarse grain structure.Cooling curve is shown in figure 12.
CONCLUSION
The casting process can be simply understood by constructing an axle pulley of an altenator.The CO2 sand casting process is not economical than green sand casting process.But the CO2 sand casting process is better due to the following reasons.
1.Green sand contains moisture,it breaks very easily.While silica gel is formed when CO2 is passing through the CO2 mould.since it is a better bonding agent ,CO2 sand mould is more stronger.