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Forgings Heat Treatment Found That How To Deal With Overheating
Nov 02, 2017

Forgings heat treatment found that how to deal with overheating
Forgings in the heat treatment when the furnace was found overheating, can take from the overheating temperature to the disappearance of fire temperature (about 500 ~ 550 ℃), immediately reheated to the required annealing temperature. Forgings the overheating of the Forgings plant, the correct specification can be used to carry out a normalizing or annealing to re-refine its grain. Overheating is not serious Forgings, can be used a normalizing; and the larger Forgings can be used twice normalizing (Ac3 +50 ~ 70 ℃). Forgings plant for overheating more serious Forgings, can be used for the second normalizing, the first Ac3 +100 ~ 150 ℃; the second Ac3 +30 ~ 50 ℃. To prevent overheating is particularly important, which requires the appropriate heating temperature and heating and holding time, strict and correct implementation of the heating specifications.
Forgings plant should promptly check the temperature control instrument, the correct installation of thermocouple, in order to avoid heating temperature is too high. When the Forgings heating temperature is high close to the metal starting to melt the temperature, this time not only the grain is coarse, but also causes the austenite, grain boundary serious oxidation and low melting point composition melts, destroys the interrelations between grains, So that Forgings scrap, this phenomenon is called over burning. The Forgings plant emits sparks from the steel during the heating process and observes that the tissue is found to have melted or oxidized phenomena along the grain boundary, where the strength is extremely low and is no longer available. For the burning pieces can not be remedied, can only be scrapped.
The burned tissue makes the Forgings performance worse and is prone to cracking. Therefore, it is not permissible to heat the flaws. Therefore, it is necessary to strictly prevent the Forgings from burning during the heat treatment. Forgings overheating and overheating are caused by the heating temperature is too high, the precaution is to develop the correct heating temperature; often check the instrument, so as to avoid malfunction caused by overheating and over burning.
Forgings plant in the production of mechanical properties and surface hardness requirements of large Forgings, after Forgings to be rough, and then quenched and tempered heat treatment or surface hardening. In the Forgings plant heat treatment, due to rapid changes in temperature, will produce a lot of temperature stress. As the phase transition also produces tissue stress, and the residual stress of the Forgings is superimposed, the tensile stress of the composite will produce various forms of cracking and cracking if it exceeds the tensile strength of the material and there is no plastic deformation relaxation. Such as Forgings longitudinal, transverse, surface and center cracks, surface cracking and surface peeling. Due to the large size of large Forgings, the temperature distribution of heating and cooling is not uniform, the phase transition process is complex and the residual stress is large, and there are various macroscopic and microscopic defects, poor plasticity and low toughness, which can exacerbate crack initiation With the expansion of the process, often the formation of immediate or delayed cracking damage, and even burst and natural split, etc., resulting in economic losses Forgings plant.
Forgings the cooling is Forgings from the final Forgings temperature to room temperature cooling. Cooling mode improper selection, may be due to excessive stress cracks, the formation of reticular carbide and white spots affect the quality of products, and even Forgings scrap.
1, spray cooling. Use the fan of the wind from the water pipe out of the water sprayed on the Forgings on the cooling.
2, air-cooled. The Forgings is cooled by blowing.
3, air cooling. The Forgings are evenly placed on the ground to cool in the still air. Be careful not to place it on a damp ground or metal plate, and do not place a place where you can wind it to prevent the local cooling of the Forgings caused by defects.