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Annealing Treatment Process Of Cast Iron



The high annealing temperature annealing furnace, pit type annealing furnace as main casting part, and must eliminate intensity and even, must consider the change of the organization, the most suitable annealing temperature can be roughly summarized as follows: in terms of non iron alloy, at about 500~575 DEG, for low cast iron the bar, at approximately 550~600 DEG, of high alloy cast iron is at 600~650 DEG C, the temperature distribution in the furnace, must as far as possible to avoid the existence of uniform temperature gradient, under no circumstances, for annealing flame or hot gas, can not be directly sprayed to the casting, in order to avoid heating when the thin wall part in time, caused by thermal stress, and increase the amount of residual stress, and cause rupture, at the annealing temperature after the first hour most of the internal stress are eliminated, as the thickness of the casting, general casting thickness of each 25mm must increase with increasing annealing time of one hour the.
Softening annealing of gray cast iron and spheroidal graphite cast iron cast iron 2 annealing furnace annealing, in fact is a kind of heat treatment on carbide decomposition, non alloy and low alloy cast iron, iron carbide is not formed carbon is a stable phase, after a long enough time at high temperature, carbide is decomposed into graphite, iron or fertility of austenite, the decomposition process is commonly called softening heat treatment, the main program is also manufacturing malleable iron, gray cast iron in the carbide is mainly divided into two categories, the first category is the eutectic carbides formed in the solidification process (EutecticCarbide, commonly called free carbides (FreeCarbide. The softening process is divided into two steps. The first section is the first section of the graphite and the two phase of the graphite. The graphite is decomposed into second stages of the iron and graphite.
The first part of the process of graphite treatment, so when the process of the formation of amorphous carbon, graphite, graphite and graphite, and the sharp edges, due to the cooling rate faster, or in the sharp edges of the cast, and the sharp edges, and when the silicon is not enough, and the lack of carbon content, if the lack of carbon, or inoculated with the Cr, V,, if the,,,, can form the same results if the the original formation of carbides will not have an effect on the formation of the carbide in a certain temperature range, the decomposition rate decreases rapidly with the decrease of temperature, and increases with the increase of temperature. The first stage graphitization temperature should not be too low, the temperature range between about 850 to 950 DEG C, of spheroidal graphite cast iron, due to high toughness, so the temperature should not exceed 920 degrees, so as to avoid the occurrence of austenitic crystal Tiechu, annealing time must be lengthened, the annealing time not only determined by the annealing temperature at the same time, need to consider the species composition of cast iron, and even to consider the type of carbide, generally by annealing time is 2~15 hours, in order to avoid decarburization, considering the economic benefits, the annealing time should be shortened as much as possible, graphite elements such as silicon and trace the decomposition of copper can accelerate cenentite, stability the carbide elements, such as chromium, aluminum, copper, will seriously delay the graphitization under the condition of normal time.
The main role in the cooling process, the first part of the graphite after treatment, in the cooling process, the first part of the process, in order to prevent the formation of iron in the cooling process, the second section of the graphite processing can be seen in the first part, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is no eutectic carbide, if there is a very slow cooling, or in the case of spherical graphite cast iron, or in the case of spherical graphite. The rate increases with the increase of temperature.


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