The most suitable cooling speed must be chosen when the forging forming is finished, and the size of forgings and the chemical composition of the material should be considered when cooling speed is determined.
The common cooling methods of forgings are as follows:
According to the required cooling speed of forgings, the common cooling methods are air cooling, heap cooling, pit (box) cold, lime sand cold and furnace cold. Air cooling: Cool in air, faster.
Forging after forging a single or pile directly on the floor of the workshop to cool, but not on the wetland or metal plate, also do not put in a drafts place, so as to avoid the forging cooling uneven or local cold caused by cracks. Heap Cold: The pile of forgings is cooled in the air in the bin.
Medium and small carbon steel and low alloy steel forgings are often used.
Pit (Box) Cold: The forging after forging is placed in the pit or steel plate interlayer containing insulation asbestos steel plate box closed cooling. In the insulation material cold: forgings buried sand, lime or asbestos materials, slag cooling. General forgings into the sand temperature should not be less than 500 ℃, the surrounding sand storage thickness can not be less than 80mm.
The cooling speed of forgings in pits can be regulated by different insulating materials and insulating medium.
In order to effectively prevent the precision forgings from oxidizing during the cooling process, they can be cooled in a protective atmosphere. Furnace Cold: Forging after forging directly into the furnace in accordance with a certain cooling standard slow cooling. Because the furnace cooling can be controlled accurately by the temperature control of the cooling speed, it is suitable for high alloy steels, special steel forgings and various large forgings after the forging cooling. General forging of the furnace temperature is not less than 600℃?650℃, the furnace should be up in advance to the same temperature as the forgings, waiting for all the furnace cooling parts to start to control the cooling speed. General oven temperature should not be higher than 100℃?150℃.
Common cooling specifications are isothermal cooling and undulating isothermal cooling.
Control cooling: For some forgings must be controlled cooling, such as T12, GCr15, 9CrSi and other steel forgings, after the final forging with spray cooling to the 600℃?650℃, and then put people in the pit slowly cooling, to avoid the formation of coarse mesh carbide, but also to prevent cracks. Isothermal annealing: White-sensitive steel ingot after forging cooling is very important, after the stop-forging direct hydrogenation isothermal annealing to prevent the production of white spots.