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Ductile Casting Cooling and Heat Treatment Temperature of Nodular Irons


Metal mold working temperature and each part of the temperature difference of ductile casting cooling temperature field has an important role. To metal type local overheating area forced water and air cooling is to ensure that the area to keep the normal operating temperature, improve the production efficiency, and at the same time, eliminate overheat, ensure the normal cooling temperature field. Metal mold working temperature control is advanced and effective means is to control the cooling water outlet temperature and outlet temperature of cooling water circulation speed regulation. In addition, to local large and thick hot day parts can also be set high thermal conductivity or heat storage capacity big metal insert or adjust coating layer thickness and coating types are in place to ensure that cast a form a reasonable cooling temperature gradient, eliminate local shrinkage.

Nodular casting heat treatment is to point to by a heat treatment standard, control the heating temperature, holding time and cooling speed degrees, change alloy organization, its main purpose is: to improve mechanical properties, enhance the corrosion resistance, improve the processing performance, get size stability.

In order to improve the actual effect of stress relieving, heating temperature can reach the best ductile casting last complete discharge temperature. In less than the last complete discharge temperature, heating temperature, higher the stress relief is more sufficient. However, the heating temperature is too high, can cause nodular casting organization change, thus affecting the performance of the ductile casting. For gray cast iron parts, the heating temperature is too high, can make the eutectoid cementite graphitization, nodular casting strength and hardness of the lower. For white cast iron parts, the heating temperature is too high, also can make eutectoid cementite decomposition, nodular casting hardness and wear resistance greatly reduced.

Nodular casting stress relieving heating temperature of 550℃. When cast iron containing stable base structure of alloy elements, can be appropriately increase to stress annealing temperature. Low alloy castings for 600℃, high alloy gray cast iron can be increased to 650℃. Heating rate is generally sixty to 100℃. Heat preservation time according to the following empirical formula calculation: H "2 ~ 8 range selection, type of ductile casting thickness of the unit is mm, heat preservation time unit is hours, H" in 2 ~ 8 range selection. Complicated shape and requirements fully eliminate stress ductile casting should take great H "value. With the furnace cooling rate should be controlled in 30℃ / H the following, general ductile casting cold to 150 ~ 200℃, a complex shape of ductile casting cold to 100℃ are.




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