Carbon Dioxide Sand Casting Process.

OBJECTIVE

Mixing COsand casting process together with additional ingredients according to the desired specifications and also pouring melted metal into mould.

 

DEFINITION

CO process is one of the moulding processes whereby Silica sand is mixed together with Sodium Silicate and being applied with COgas. By applying COgas toward this mould, it will be harden in a matter of seconds.

 

                                                                                                                                                            

Figure 1.0 The Cope and Drag of ‘Rehal’              Figure 1.1 The COSand mould.

 

 

ELEMENT NEEDED

1. Silica Sand
2. Water  
3. COGas
4. Sodium Silicate

 

 

 

APPARATUS

 

1. Sand Mixer
2. Rammer
3. Trowel
4. Lifter

 

PROCEDURE

 

1. Prepare the elements and apparatus.
2. The elements or ingredients is weigh and mixed together.
3. COSand mixture is prepared.
4. The COSand mixture is placed in a mould and being flattened equally.
5. The COSand mould is being tested.
6. The edge of the COSand mould is filled until it is full.
7. COgas is applied and make sure that the sand mould has really harden.
8. The sand mould box is turned over to remove the pattern.
9. The same process is done for the next COSand mould making.
10. Safety and precautions must be taken into account while the process is being done.

 

 

 

 

 

 

 

 

 

 

 

RESULT

 

Figure 1.2 The final products from COSand casting.

 

From this experiment, two patterns were selected and being applied in the COSand mould making. The patterns are ‘rehal’ and ‘keris’ trophy. Firstly, as according to the procedure, the sand mixture is being prepared and ingredients such as Silica Sand, Water, COGas, Sodium Silicate were added and mixed in the sand mixer. After the sand mixture is ready, it is taken out and directly mould making process is being done.

At this stage, a split pattern is being used for both types of patterns. The sand mixture is slowly being filled into the cope and drag until it is fully filled. The cope and drag are being hit a few times to make sure the mould itself will loosen a bit to make it easier to be removed from the mould box. Next, holes are made on the mould in order to apply COGas. The holes must be uniform, in order to obtain uniform hardening due to COGas later on. When the holes are done, COGas is applied into the holes for 30 to 45 seconds to harden the mould.

When this process is done, the cope is turned over .The cope and drag is slowly being removed and the COSand mould is obtained. Later, both cope and drag is combined together with moulding glue. As for the ‘rehal’ pattern mould, a core print is placed to determine the shape of the ‘rehal’ stand. When everything has done, melted metal which has been melted earlier is being poured into the mould.

The metal being used in this process is Aluminium which has a melting temperature of 660 equivalents to 1220 F. The Aluminium bar is melted in a furnace but exceeding more than 1220 F in order to obtain pouring temperature, which was

1300 F. This is to avoid cooling of the melted Aluminium before it is being poured into the mould. After the molten metal is being poured, it is left to cool and the pattern is broken on the next day.

            When the molten metal has solidified, the mould is being broke to obtain the casted part. For the result of the ‘rehal’, the overall shape is considered well done. However, the writings on top of the ‘rehal’ surface do not seem to be clear. As for the ‘keris’ trophy, the overall shape is considered average but at the bottom of the trophy there a surface defect occurred. Further explanation will be explained in the Discussion section.  

 

DISCUSSION

 

1.‘Keris’

 

            As been determined from the experiment, the ‘keris’ trophy product has a few defect. The defect occurred are located at the bottom of the trophy and also at the surface trophy itself. For the defect at the bottom of the trophy is termed as shrinkage cavity. This defect present due to improper solidification where certain regions cools faster and restrict the molten metal to flow to next region. For the surface finish, obviously the writing on the face of the trophy is not so clear. It is believed due to the improper CO Sand compacting. As for the result, the writings seemed to be faded. Other than that, further surface finishing is required to be applied to the whole trophy itself.

 

2. ‘Rehal’

 

            The ‘Rehal’ determined from this CO sand process can be considered as average. There are two defects present at the product of ‘Rehal’. The first detected defect is gas defect which refers to pin holes. This occurred due to lower permeability of the mould causing difficulties for the gas to escape. The second defect occurred is at surface of the ‘Rehal’ which affected the writings on top of it. This is due to the impurities present at the surface of the pattern. When this happened, the COSand cannot obtain the exact mould of the pattern.

 

CONCLUSION

 

            As for the conclusion, we can say that both of the products which obtain from this particular COSand process are not successful. This is due to the defects that occurred during the mould making process. For the defects involving shrinkage cavity, it can be overcome by having proper feeding of liquid metal and also proper sand casting design.

As for the defect involving unclear writings on the surface of the ‘Keris’ trophy, COSand must be compact firmly at the surface of the pattern. This is important to determine the desired shape or surface characteristics of the pattern itself.

            Referring to the ‘Rehal’, the gas defect occurred and caused pinholes to happen. This is due to the improper exits of the gaseous in the mould during the cooling process.  

It is also caused by lower venting, lower permeability of the mould, and improper design of casting. Other than that, the impurities that present at the surface of the pattern causing the mould to be inaccurate and making the final products to have poor surface finish and also the desired shapes or writing cannot be obtained.