BILBAINA DE TRATAMIENTOS
Our modern vacuum treatment furnaces have the possibility of tuning with high gas pressures ( up to 10-20 bar). The solve the problem of thermal fatigue by stopping isothermal tempering ( martempering ) that modern vacuum systems allow using accelerated cooling characteristics and maintenance high pressure low temperature convection .
This vacuum heat treatment is oriented to always treat complex problem of molds and dies material 1.2343 , 1.2344 , and steel equivalent.
To better understand the influence of heat treatment on steel, you must first know the structural changes at different temperatures. These changes are quite complex and depend on the amount of carbon and other factors, which in metallurgy accurately establishing the equilibrium diagram called iron-carbon .
Between 0 C and 1500 º C ª iron undergoes various transformations in its cubic structure , (owned aleotropica ) , the temperatures at which these changes occur are fundamental in thermal treatment and are called critical temperatures .
Up to 911 ° C ( critical temperature AC3 ) , ordinary iron crystallizes in the body-centered cubic system and is referred to iron ? or ferrite. It is a ductile and malleable responsible for good forgeability of alloys with low carbon content and is ferromagnetic up to 770 ° C ( Curie temperature at losing that status , is also commonly called AC2 ) . Supports up to 0.021 % C in solution eutectoid temperature . Constituent is softer steel .
Between 911 and 1400 ° C crystallizes in the face centered cubic system and is referred to iron ? or austenite. Given its greater compactness austenite deforms more easily and is paramagnetic . Is the most dense constituent of steel and is formed by a solid solution of carbon in iron insertion gamma . The amount of dissolved carbon , varies from 0.8 to 2% C which is the maximum solubility at the temperature of 1130 ° C.
Austenite is not stable at room temperature but there are some steels austenitic chromium-nickel whose structure is called austenite at room temperature. Austenite is formed by centered cubic crystal faces, with a Brinell hardness of 300 , a resistance to traction of 100 kg/mm2 and an elongation of 30%, is not magnetic .
Between 1400 and 1538 ° C again crystallized in the body centered cubic structure and is referred to iron ? which is essentially the same but with alpha iron lattice parameter greater the effect of temperature.
The higher the temperature the iron is liquid. If carbon is added to iron, the atoms may be located simply in the interstices of the crystal lattice of the latter , but in steels is combined to form iron carbide ( Fe3C ) , ie a chemical compound defined and is referred cementite so that carbon steel actually consist of ferrite and cementite .
Pearlitic structures are obtained by slowly cooling the carbon steel , perlite has hardness and ductility values ??intermediate to those of ferrite and cementite .
But changing the cooling conditions (base of the heat treatments ) may obtain different crystalline structures as the martensite which is the typical constituent of hardened steels and obtained almost instantaneously to quenching the austenite. Is a carbon supersaturated solution with alpha iron tendency , the higher the carbon to replacing centered cubic structure in the body for body-centered tetragonal . After cementite ( and carbides of other metals ) is the hardest constituent of steel .
Intermediate cooling rates lead to bainite , pearlite like structure formed by ferrite and cementite needles but higher ductility than this. Can also be obtained by rapidly cooling austenite alloys gammágenos elements (favoring stability iron ? ) As nickel and manganese, as is the case for example of the austenitic stainless steels .
Formerly also identified Troostite sorbitol and which have proved really tiny beads of interlaminar distance so that these names have fallen into disuse .
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