1、The castings have flying edges or burr.
Reason: Wrong ratio of water and powder;Improper storage method of investment powder; The time of stirring and vacuum has surpassed the regulated time (8-9minutes); The heating speed ofsteel perforated casting flasks in the furnace is too fast.
2、Incomplete casting
Reason: The trunks of wax trees are too small; The wax molds have not been burnt completely; The temperature of steel perforated casting flasks when castings is too low; The temperature of metal when casting is too low; The weight of metals is not enough.
3、The castings are not smooth
Reason: The wax molds have not been burnt out, leaving carbon in the investment molds; The furnace temperature is too high (over 788℃)
4、The castings have tiny holes
Reason: Metal temperature is too high; The temperature of steel perforated casting flasks is too high; There are too many old metals in the metals, the content of old metals should not be over 50%; Too much fusing agent has been added in the metals.
5、There are tiny grains in the surface of metals.
Reason: It is too fast to put the steel perforated casting flasks into the furnace; The heating speed of furnace is too fast; There are abnormal tiny grains in metals; The rust of the steel perforated casting flasks has not been cleaned off.
6、Castings are coarse
Reason: The water and powder have not been mixed completely; Wax molds are not welded well; Stirring time is too long or not enough; The heating speed of steel perforated casting flasks is too fast; The temperature of dewaxing can not exceed 150℃, otherwise, the wax will bubble up to erode the casting surface.
Additional:
Casting should be performed from high to low, according to the temperature of casting.
Graphite is liable to absorb the moisture, it must be dried appropriately before casting.