Casting Picecs Mechanical Action And Chemical Reaction
The source of inclusions is mainly ladle lined in the formation of high temperature metal melt erosion of the molten slag, with the flow into the cavity to cause Casting Picecss slag. The ladle lining should use high refractory material to reduce the erosion of inclusions, and finally through the metal liquid filter to improve the quality of Casting Picecs.
Metal inclusions. Micro-inclusions distributed in the grain boundary, derived from the metal liquid hydrogen, oxygen, nitrogen precipitation, suction, oxidation, charge, lining the melting solution, etc., need to be purified by refining. Inclusions can be called foreign inclusions, metal melting, containers, flow fields, mechanical effects of sand and inclusions generated by chemical reactions, and secondary additions of molten metal to the secondary oxidation inclusions during pouring and filling. Inclusions, the particle size greater than 50μm
Casting Picecs the surface and the surface after the visual appearance of the inclusions are often not tightly analyzed that is judged as "trachoma", which is not correct. Sand and slag are lighter than the metal liquid, when the temperature of the molten metal is gradually reduced, it will stay inside the Casting Picecs with the floating or late entry. The dregs entering the ladle are in accordance with the composition of the lining material: the Al2O3 is dominated by the neutral material, the SiO2 is mainly acidic and the basic material is MgO. Trachoma and slag eye, the appearance of the two similar appearance, identification method In addition to chemical analysis, the use of a pointed steel impact hole filling: If the filler is easy to brittle and broken color and the same color, Slag; if the white powder and sand and fill the material is full, the trachoma. There is a kind of slag, if the light yellow enamel and thinner, it is the molten metal flowing through the Casting Picecs system and the sand surface of the formation of the melting solution; if black, is the metal liquid in the Casting Picecs process of the formation of two Hypoxia. If the slag is floating with the metal liquid cooling into a thin slag, if not floating left in the Casting Picecs, the formation of slag eye defects.
Evaluation of the surface of the Casting Picecs slag slag, to be carried out before the shot, or shot blasting can not be identified. Surface and the inner wall of the wall if the smooth if the pores, if there are inclusions in the pores for the dregs produced pores. This is the ladle in the late pouring of the object (not the lining material) or alloy particles in the type of melting gas.
In the "trachoma" defects, inclusions accounted for 70-80%, the actual proportion of the trachoma is generally only 20-30%. We do not have strict inspection classification, usually called "trachoma". The main source of the trachoma: the pouring system, the cavity has floating sand, sand, from the skin, sand surface heat effect off, squeeze sand, gate cup, out of the hole out of sand, etc., but these defects are much smaller than the ladle lining high temperature After the erosion of the dross and a small amount of liquid scum.
(1) Casting Picecs cross-sectional size change is too large. If the size of the Casting Picecs in the design changes too large, the cooling rate of the thin section is much faster than the condensation rate of the adjacent thick section, so it is difficult to achieve the order of solidification of the Casting Picecs, but also difficult to make up. Design to try to avoid this situation, or should be used cold iron, in order to achieve the order of solidification of the Casting Picecs and conducive to fill.
(2) Casting Picecs section is too thick, if not take the appropriate measures to fill it, due to poor formation of shrinkage shrinkage.
(3) fillet is too small. Casting Picecs corner angle radius is too small, will lead to reduced heat transfer capacity of the sand, solidification rate decreased, while the sand because of the strong heat, gas pressure, precipitation of gas can not penetrate into the molten metal, resulting in Casting Picecs Air shrinkage.