Mold Assembly Procedure for sand casting

- Jun 07, 2017-

1.      The ground where located the sand box should not be wet or with water.

2.      Blow off the falling sand to clean the molds and cores. Inspect the molds and cores thoroughly, including surface quality, flatness, smoothly degree, dry degree, strength, whether deformed, damage repaired or not, etc. Do not Fix the sand box if the molds and cores are not qualified.

3.      The coating should have good  strength at ordinary temperature and high temperature, high fire resistance, excellent high temperature chemical stability, so as to form a good isolation layer between the molten steel and the mold to resist the high temperature of the molten steel. So it is necessary to strengthen this work.

4.      The concentration of paint should be suitable. In order to keep the original ratio, try not to add alcohol or add as little as possible, so as not to affect the coating effect.

5.      The coating should be brushed from inside to outside, from top to bottom. Blend the solvent while brushing. Brush the coating evenly and reduce brush mark. Prevent the coating from flowing and accumulating, especially the lower part, corner and depression.

6.      Coating flow and accumulation are the key factors that result in pit defects in the bottom face of the casting, which need a lot of welding repair. The relative people should pay high attention to this.

7.      For pitman castings the molds and cores should not be brushed coating for only once. After brushing the first layer of coating, polish the surface with sand paper; inspect the flatness, eliminate the coating accumulation, find out the positions without coating to brush coating on them. Then brush the coating for the second time.

8.      Fire the coating immediately after brushing. Or brush the coating for a small area and fire it after brushing, then another area...If not fire the coating or not burning thoroughly, the coating will have no strength.

9.      After fired, the rigid surface of the coating offers the surface strength. So after the coating surface sanded by sand paper, another layer of coating should be applied. Or the coating will be flushed off by the molten steel.

10.  Along the mold parting surface, the core head margin, the core edge and corners are vulnerable points of invasive pores. Thus coating must be applied. No visible sand allowed.

11.  Since water glass sand tends to absorb moisture, and summer air is humid, the cores should not be stored for more than 3 days. Molds and cores absorbed moisture and strength decreased apparently should not be used.

12.  Molds and cores applied with coating should be used for pouring in time. If box fixing and pouring will be done the next day after the molds and cores coating applied, heat up before pouring.

13.  Any damage found during assembling the cores and fixing the box should be repaired to size carefully and responsibly. If not, any problems result in should be responsible by the operators.

14.  Measure the dimensions carefully during assembling the cores. Inspect the position degree and symmetry degree. Ask relative people to re-check and confirm if necessary.

15.  Fix the cores stably and steadily at the correct position, fasten them properly. It is important to fill in solidly the gap between the molds and the cores, especially the bottom locked cores, in case the molten steel gets in or the cores shift.

16.  Make sure the exhaust holes for the cores valid and unobstructed.

17.  Make sure the internal chill iron conforms to the processing technique request.

18.  Make sure the molten steel inlets and risers conform to the processing technique request. Do not expose waste sand around the risers and brush coating there. Molten steel cup is good for pouring operation.

19.  Repeatedly and effectively blow off the fallen sand in the casting system. The last job before closing the box is to blow and suck the sand again. When fixing the box, make sure the upper box won't crush the cores; make sure the wall thickness is even and the position is precise. Open and re-check the box if necessary. And check the situation from the risers.

20.  It is very important to fill in solidly the box gap, lock and weld up the box. Heavy or tall box should be poured in the underground pit and comply with relevant provisions. Nobody should operate under the box without support. The whole process should guarantee quality and safety.