Machining Methods

Preventive measures for machine tool castings casting defects

Preventive measures for machine tool castings casting defects

Preventive measures for machine tool casting defects: improve the slag-blocking capacity of the casting system, increase the inner corners of the machine tool castings, there are penetrating or non-penetrating cracks on the machine tool castings (note if they are curved), and the metal skin at the cracks is oxidized.

Strictly control the content of S and P in molten iron. The wall thickness of the machine tool casting is as uniform as possible. To improve the concession of molding sand and core, the riser should not hinder the shrinkage of the machine tool castings, shrinkage loose in the machine tool castings, small and inconsistent shrinkage holes, gathered in one or more places, the grains are thick, and each grain exists Very small holes, seeping water during the hydrostatic test. Minimize the thermal joint at the junction between the walls and the pouring temperature and pouring speed as much as possible.

Sand holes have holes filled with molding sand inside or on the surface of machine tool castings. Strictly control the performance and molding operation of molding sand, and pay attention to cleaning the cavity before molding. It is impossible to pour the lack of meat in the machine tool castings caused by the metal liquid not completely filling the cavity. Increase pouring temperature and pouring speed. Do not stop the flow and prevent fire. There is a layer of metal nodules or flakes on the surface of the machine tool castings, and a layer of molding sand is sandwiched between the metal nodules and the machine tool castings.

Strictly control the performance of molding sand and core sand, improve the pouring system, and make the liquid metal flow smoothly. Large plane machine tool castings should be cast obliquely. There is a gap or pit in the machine tool casting that is not completely fused, and the border edge is smooth, which increases the pouring temperature and pouring speed, and improves the pouring system. Continuous flow when pouring. The sticky sand is on the surface of the machine tool castings, and it is completely or partially covered with a layer of metal (or metal oxide) and sand (or paint) mixture (compound) or a layer of burning structured sand, resulting in rough surface of the machine tool castings. Reduce the gap between sand particles, reduce the pouring temperature of metal properly, and improve the refractoriness of molding sand and core sand.

Shrinkage holes are inside the thick section of the machine tool casting, the interior of the two interfaces, and the interior or surface of the junction of the thick section and the thin section. The shape is irregular, the holes are rough and uneven, and the grains are coarse. Machine tool castings with small and uniform wall thickness should be solidified at the same time. Machine tool castings with large and uneven wall thickness should be solidified in order from thin to thick, and cold iron should be placed reasonably. The slag pores are irregular holes in the machine tool casting or on the surface. The perforations are not smooth, and all or part of them are filled with slag. Increase the temperature of the molten iron. Reduce the viscosity of slag. Avoid sudden changes in wall thickness, premature opening, and chilling of machine tool castings. Cold cracking has penetrating or non-penetrating cracks (mainly straight) on the machine tool castings, and the metal skin at the cracking point is oxidized

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