The problem of machine tool Castings should be paid attention to when pouring
Machine tool Castings with EPC / resin sand Castings, when the machine tool Castings in the Castings should pay attention to the following points:
First, at the beginning of the pouring, especially in the moment when the molten metal is in contact with the foam, the static pressure head of the molten metal is less than the polystyrene decomposition when the gate is not filled or just started pouring due to the large amount of gas produced by the gasification of the molding material Product gas pressure, too fast pouring easy to produce choking fire phenomenon, so that the molten metal splash. In order to avoid this phenomenon, in the beginning of the pouring can take the first stream of slow pouring method, to be pouring system is filled with metal liquid, you can increase the Castings speed, the sooner the better, but the gate cup filled with metal Not spill as a criterion. At the end of the Castings, when the metal liquid reaches the top of the mold or the riser root, it should be slightly wrapped to keep the metal rise steadily and not to cause the molten metal to come out of the riser.
Second, as far as possible selection of the end of the package. Bottom injection of metal liquid heat loss is small, pressure head, pouring speed, slag floating in the metal liquid on the surface, pouring molten steel is relatively clean. By the equipment conditions, for some of the requirements are not high or generally small machine tool Castingss can also be used subcontract pouring.
Third, the pouring process can not be interrupted. In the disappearance of Castingss Castings, must continue to inject the metal liquid, until the mold is full. Otherwise, it is easy to pause at the Castings caused by the entire plane of the cold barrier.
Castings Common Defects and Analysis of Oxide Slag Defects Features: Oxidation slag is mostly distributed on the upper surface of the Castings, in the corner of the mold without ventilation. Fracture mostly gray or yellow, by x-ray or in the mechanical processing found, but also in the alkaline washing, pickling or anodizing found in the reasons: 1. The charge is not clean, the use of excessive chargeback 2. Pouring system Poor design 3. Alloy liquid slag is not clean 4. Castings improper operation, brought into the slag 5. Refined to calm the treatment of standing time is not enough.
To prevent the method: 1. The charge should be blowing sand, the amount of back to the appropriate reduction in the use of 2. Improve the Castings system design to improve its slagging capacity 3. Use appropriate flux to slag 4. Castings should be smooth and should pay attention to slag 5 The alloy liquid should be allowed to stand for a certain time before pouring.
Two holes in the bubble characteristics: three Castingss wall pores are generally round or oval, with a smooth surface, usually shiny oxide, sometimes oil yellow. Surface pores, bubbles can be found by sandblasting, the internal air bubbles can be detected by X-ray or mechanical processing.
Stomatal bubbles in the X-ray film was black Reason: 1. Castings alloy is not smooth, involved in the gas 2. Type (core) sand mixed with organic impurities (such as coal, grass horse manure, etc.) 3. Mold and sand core Poor ventilation 4. cold iron surface shrinkage 5. poor design of the pouring system.
To prevent the method: 1. Properly grasp the Castings speed, to avoid involvement of gas. 2. Type (core) sand can not be mixed with organic impurities to reduce the amount of material blowing 3. Improve the (core) sand exhaust capacity 4. The correct selection and treatment of cold iron 5. Improved Castings system design Three loose loose defects Features: Castings shrinkage generally produced in the middle of the runner near the root of the large part of the rifle, the thickness of the wall transition and a large plane at the thin wall.
Castingss are so widely used in mechanical products, mainly in the Castings of the following characteristics:
1, Castings methods such as forging, stamping, welding and powder metallurgy and other metal parts molding method compared to the Castings method can produce a very complex shape, especially with complex cavity shape of the rough and parts. Such as machine bed, box and so on. And the Castings method can limit the shape of the part structure, the Castings can adopt the most reasonable cross-sectional shape according to the stress condition, and the most reasonable cross-sectional shape can be used according to the force condition, and the reinforcing ribs can be arranged according to the needs, To improve the structural strength and stiffness.
2, under certain conditions, the use of special Castings, mosaic Castings, bimetallic Castings, small hole Castings technology and Castings structure and other methods can make the structure of the parts more reasonable. The use of these methods can also solve some of the other metal forming methods difficult to solve the problem in order to achieve better technical and economic results.
3, with the Castings method can produce a variety of materials and the size of the Castingss. At present the industry commonly used metal materials can be cast, and some metal materials, such as the application of a very wide range of cast iron, Castings method can only be used to shape. The size of the Castingss produced can be from small to several grams of instrument parts to weighing two to three hundred tons of metallurgical mines and power equipment in the heavy Castingss.