In precision casting, graphite sheet in gray iron casting has the effect of cutting non-metallic matrix, damaging its continuity and increasing its strength.From the strength of thought, should prevent the production of long and thin graphite sheets and thin graphite sheets, with obvious orientation of the graphite sheet reaction is particularly large.Grasp the spread of graphite, is to ensure that gray iron casting function of the key.

Type A graphite is formed under conditions of low carbonization yield and low freezing rate.Because of the large primary dendritic crystal body, eutectic change occurs super-cooling degree is not big, graphite centers do not have much, eutectic group is bigger, consisting of the d-type graphite graphite pieces more than. Because ice is turbulent, the body of the dendritic crystal is thriving, eutectic change occurs in liquid phase is not necessary, between the primary dendritic crystal body composed of graphite flake along dendritic crystal orientation growth, deposit is coupled to the azimuth of about iron mechanical function of the reaction is bigger, to make every effort to prevent it happen.

Type B graphite was in the shape of yellow flower under the optical wind microscope. The graphite sheets in the center of the eutectic cluster were relatively thick and thin.In practice, the center is d-type graphite and the center is a-type graphite.The nucleation environment of type B graphite is worse than that of type A graphite, and the degree of supercooling during eutectic transformation is also higher than that when forming type A graphite. When crystallizing, supercooled graphite (type D) occurs at the center of the eutectic group first, and the latent heat of crystallization released increases the degree of supercooling around, forming type A graphite.If the amount of type B graphite is not much, the function of iron reaction is not large, under normal circumstances can allow it to have.

Type C graphite is a kind of iron with low carbonation equivalent, high freezing rate, high undercooling degree, and formed between dendrites in the environment of flourishing dendritic crystals of primary body. The graphite sheet is thick and directional.D - type graphite is rare in thin - walled gray iron castings with low carbonation equivalent.In the absence of alloying elements, type D graphite is often accompanied by a lasso.If the matrix is pearlite, then pig iron wear resistance is better, and machine processing can lose a finer nominal roughness.

It is necessary for d-type graphite to present in highly carbonized equivalent (hypereutectic), frozen and turbulent cast iron, including fine flake graphite, small flake graphite, and sometimes the whole graphite sheet with sharp angular blocks.When supereutectic ferric liquid freezes, after passing through the liquid phase line, primary graphite is separated at a certain degree of supercooling and gradually grows in the liquid phase.Because the crystallization measurement is higher, into a short time longer, constitute less branches of the slender sheet.When the measurement was elevated to eutectic measurement, the deformation of eutectic transformation occurred. The graphite then occurred was A deformed eutectic ink (type A graphite). After all, the result was that A deformed eutectic ink was scattered between the fine graphite sheets.Thus, type C graphite is composed of fine, massive graphite and type A graphite.Type C graphite can improve the thermal conductivity of pig iron and improve its anti-tax charging power, but the mechanical function of pig iron is more reactive, normal structural castings should not have this graphite.

E-type graphite is formed when eutectic transformation occurs in the environment with low degree of supercooling due to its high nucleation power and low freezing rate.

At the time of the investigation under the optical wind microscope, the graphite was in the form of evenly distributed tortuous sheets with directionality, but its length was not the same due to the nucleation environment and freezing rate of the pig iron.

Excellent consumption of grey mouth precision casting, should make its matrix arrangement for all pearlite, graphite for A type, and graphite sheets should be evenly distributed in the non-metallic matrix, pearlite should also be large and symmetrical.To minimize as much as possible the type B graphite and type D graphite in the arrangement, there should be no type C graphite and type E graphite.Therefore, it is necessary to abort the inoculating treatment and control the freezing rate of the casting.The pig iron that can present e-type graphite, such as higher freezing rate, can also form d-type graphite.Therefore, d-type graphite and e-type graphite are commonly seen in high-strength thin-wall cast iron.

The mechanical function of gray iron casting in precision casting is not necessarily derived from its matrix arrangement. In order to lose high strength, it is expected that the matrix arrangement is dominated by pearlite, and the ferrite content will be reduced over fire.It is assumed that the amount of ferrite is too much, without only causing low strength of pig iron, and the processing date will make the machine overheat, significantly increase the life of the machine tool.Unlike nodular iron, there is no request for ductility and tolerance of gray iron castings, only its strength is required, because the normal pearlite content is high.

Such graphite can be occasionally found in subeutectic pig iron.Such as: induction furnace training and furnace guess the amount of cast iron too much, because the original cast iron genetic reaction, can present with sharp Angle of block graphite;This graphite also occurs when the amount of the inoculant is too large to form a full concentration of silicon.

The mechanical function of gray iron castings in precision casting depends on the matrix arrangement and the distribution of flake graphite.The mechanical function of gray iron castings depends on the matrix arrangement and the distribution of flake graphite.The mechanical function of gray iron casting is not necessarily derived from its matrix arrangement. In order to lose high strength, it is expected that the matrix arrangement is dominated by pearlite, and the ferrite content is reduced over fire.