Steel Casting Near The Surface
Casting steel in the production process often occur in a variety of casting defects, the common form of defects are: trachoma, sticky sand, pores, shrinkage, shrinkage, Steel Casting sand, scarring, cracks and so on.
A) trachoma defect
The trachoma is due to the fact that the molten metal (blocks) of the molten metal that has been washed down from the surface of the sand chamber or in the shape and chamber is less likely to fall into the pouring system and remain in the interior or surface of the casting Caused. Trachoma defects in the internal or surface filled with (core) sand holes, is a common casting defects.
B) Sticky sand defects
On the surface of the casting, all or part of the metal (or metal oxide) mixed with sand (or paint) or a layer of burning sand, so that the casting surface rough, difficult to clean. Sticky sand occurs in the type, the core surface of the strong role of the site, sub-mechanical sand and chemical sticky sand two. When the penetration depth is less than the radius of the sand, the casting does not form sticky sand, Steel Casting but the surface roughness, when the penetration depth is greater than the sand radius, the formation of mechanical sticky sand, the formation of mechanical sand, Chemical sticky sand is the product of the chemical action of metal oxides and molding materials, Steel Casting and is firmly combined with the castings.
C) Stomatal defects
In the casting, the surface or near the surface, there are different sizes of smooth holes, the shape of a round, long and irregular, there are single, but also gathered into a piece. The color is white or with a layer of dark, sometimes covered with a layer of oxide. Due to the different sources and causes of gas formation, the manifestations of stomata are also different, with invasive porosity, precipitation porosity and reactive stomata. Steel Casting Invasive porosity larger, similar shape pear-shaped, often appear in the upper part of the casting near the core wall or pouring position, mainly due to the sand core gas generated in the metal can not escape, pear-shaped small holes The position indicates that the gas enters the cast member from there. Precipitation stomatal and scattered, generally located in the casting surface, often the same furnace casting almost all occur, Steel Casting mainly due to the metal in the melting process of the absorption of the gas before the solidification failed to all precipitation, in the casting to form many scattered small pores. Reactive stomata are due to the chemical reaction of the metal-to-metal interface, which is also known as subcutaneous stomata because of its uniform distribution and often occurring at 1-3è below the surface of the casting (sometimes under a layer of oxide). And because the pores are mostly elongated pinholes, Steel Casting the long axis and casting surface perpendicular, but also can be called pinholes.