Molding Procedure For Sand Casting

- Jun 10, 2017 -

  The molding procedure for sand casting as below: 

  1.Confirm the molding base panel is not deformed.

2.Lay Chrome sand evenly at positions specified by the process technique such as  thick wall, turning corner and radius, etc. Beat it tight and compact it solidly with molding sand.

3.Lay the pouring system as per the process technique required. Seal the two ends of pouring inlet and ceramic tube joints. Prevent the molding sand from getting in the tube during the whole process. (Because the soft sand sticking on the ceramic tube could not be blowed off.)

4.Pouring inlet and mold junction and steel water falling passage inside the mold are major sand flushing points. Make sure these points has solid and strong sand layer, smooth surface, no loose sand. Add a thin brick if necessary.

5.During the manufacturing, pouring inlet should not be shifted or broken.

6.Make sure the mold has high and even compaction. Pay more attention to positions not easy to be solid, such as bottom of inserted piece, turning corner, groove and cantilever, etc. The whole mold is not allowed to have any loose sand.

7.Exhaust holes in mold corresponding with the ones in cores should be made properly. Set aside position for bolt to fasten the core.

8.Carbon dioxide holes should be even and to position. Do not stab the ceramic tube so as not to lead to leakage of steel water during pouring.

9.It is very important to blow the carbon dioxide. Over blowing could make the molds lose strength and change to powder, falling sand or sand easily to be flushed off during pouring, finally form a sand defect in the casting.

10.The higher the water glass modulus is, the quicker the mold sand will be hardened by blowing carbon dioxide, the lower final mold strength you'll get, and the shorter the hardening strength will keep. Because it is more tending to be over blowed. So it is not suitable to use high modulus water glass, especially in summer. When using low density water glass to mix the mold sand, the mold strength will be low, so it will not be proper to add water during mixing sand.

11.Water glass sand hardening strength is not determined by carbon dioxide flow. If the carbon dioxide flow is big, it will not be good to form the gel, not good absorption also lead to waste of carbon dioxide. So it is proper to blow with small flow.

12.Control the blowing time as short as possible in case over blowed, this is the key factor to get a high dry strength. Meanwhile control the storage time of the mold as short as possible in case the strength decrease naturally.

13.Badly chalked mold and core, especially the Chrome sand layer, could not be used.

14.Carbon dioxide hole should be blocked well and solidly instantly after blowed by molding sand, in case to result in steel water leakage during pouring.

15.Disassemble the pattern properly, do not damage the pattern.

16.Size and position of risers should conform to the processing technique. Lay Chrome sand at the roots of risers and make sure to have a fillet no less than R30mm. Sand content for box grid and risers should be no less than 100mm. Put foam board between two risers to facilitate to contract and retreat.

17.and complied with requests.

18.Any damage of molds and cores, positions not solid enough, positions with empty, loose and soft sand, and any hidden defects which will affect the casting quality should be repaired carefully one by one. Dry sand inclusion, stratification and gap appearance during repairing are not allowed. Make sure the molds and cores are solid and consistent in whole, without any defect that will affect casting quality and following works.

19.Newly repaired position should inserted with nails or brush a little water glass. The positions of upper surface, turning corner, where will be flushed by steel water or will be heated up should be repaired to sizes required and guarantee quality. Make sure no falling of the repaired sand so as not to form defects.

20.The whole mold and cores should meet the requirements of drawing and processing technique, should meet the size and shape requirements, meet the standard of hard, smooth, unobstructed, thick and clean.