Casting process parameters mainly include casting temperature, casting speed, and cooling intensity, followed by the height of the liquid level, casting start and end conditions, and so on.
1 casting temperature
Castability generally refers to the temperature required for good fluidity during injection of liquid metal from a holding furnace through a transfer tool. However, at present, most of the cast aluminum alloys have been applied with on-line degassing and filtration devices, and the casting temperature is still not comprehensive and correct according to the above concept. Practice has proved that the effect of outgassing is different for different liquid temperatures in the on-line degassing device. Therefore, it is necessary to consider the degassing effect of the on-line degassing device for the liquid temperature requirement. In addition, the gas precipitation in the crystallizer should also be taken into consideration. Due to the low casting temperature, the gas in the liquid crystal of the liquid does not rise to the liquid surface, causing blowholes, loose pores, and slag and cold isolator ingots. Quality defects and high casting temperatures should not exceed the melting temperature. Excessive casting temperatures can cause aluminum to leak at the start of casting. Bottom cracks and cracks, may also produce feathers tissue defects, and because the length of the injection tool and the liquid temperature drop is different, there is a heating point in the online installation, the liquid in the injection process temperature fluctuations, so the scientific specification of the casting temperature should refer to The temperature of the liquid injected into the crystallizer is generally 50°C~70°C higher than the actual crystallization temperature of the alloy. The 1 xxx, 3x xx series aluminum alloys have a narrow transition zone during casting and the casting temperature should be high; The transition zone of 2x xx, 7x xx alloys is wider. Casting temperature should be low.
2 casting speed
In continuous casting, the length of the ingot formed per unit time is called the casting speed. Old-fashioned casting is usually a casting time—a fixed casting speed; while modern casting is a curved casting speed, that is, the casting start and the casting process are not the same casting speed: the casting speed is fast and slow to the crack of the ingot, the surface quality of the ingot, The microstructure and properties of ingots have a great influence. Higher casting speeds should be used under the premise of ensuring the quality of ingots. The old-fashioned casting method solves the problem of cracks in some alloys and ingots of specifications. The method of laying or tempering is used for casting. The modern casting method adopts the curve ingot speed instead of the old-fashioned casting or tempering process. The number of auxiliary facilities has been reduced, manpower has been saved, and labor intensity has been reduced. It is also possible to avoid the fact that the casting speed of some ingot surface defects depends on the characteristics of the alloy produced and the size of the cross-section of the ingot. In general, the alloys and ingots with a greater tendency to cold cracks should be increased in casting speed, while the alloys and ingots with a higher tendency to hot cracks should be reduced in casting speed.
3 Cooling strength
Cooling strength is also called cooling rate. The cooling strength not only affects the crack of the ingot, but also has a greater influence on the microstructure of the ingot. As the cooling strength increases, the crystallization speed of the ingot increases, and the intragranular structure becomes more refined; as the cooling intensity increases, casting Acupuncture points become shallow. Transition zone size is reduced. Improve the metal feed conditions, reduce or eliminate the ingot in the loose, porosity and other defects. Increased density of ingots: In addition, the size of the compounds can be refined to reduce the extent of regional segregation.
Old-fashioned casting methods use split molds, especially when casting flat ingots. The water jacket is separate from the crystallizer. With the development of casting process technology, the molds of modern casting methods are one. Cooling water is consumed when casting with an old mold, because the old mold water supply is not closed, a part of the cooling water is opened and the cooling effect is not achieved, and the cooling intensity difference between primary cooling and secondary cooling is inevitably generated. Some ingot quality defects; while casting with a modern crystallizer. Cooling water consumption is small. Practice has proved that it is only about 70% of the old mold water consumption. At present, most foreign countries use low-level crystallizer for casting, the purpose of which is to increase the cooling intensity, reduce or eliminate the heating phenomenon in the air-gap area after primary cooling, so there is almost no secondary cooling quenching situation, ordinary cast ingot has been crystallized The height of the device is reduced to 100 people, of course, this requires the operator to have a high level of operation or increase the level of white moving control system.
However, the cooling water temperature requirement is not negligible. Normally, the cooling water temperature is set to 20, but due to the regional climatic conditions. The conditions of the water supply facilities and the temperature of the factory buildings lead to large changes, resulting in regional or seasonal ingot quality defects. Modern mold water supply system with pulse or cross-phase function is determined by process programming, so the cooling intensity can be set as a curve according to the casting process needs, especially for some hard alloys with poor low temperature plasticity, cold cracking during casting and Hot cracks exist almost at the same time. With the additional water-retaining plate system, the surface temperature of the ingot is increased to the plastic temperature of the tensile deformation, and the cold cracking of the ingot is eliminated. The hot crack prevention measures are then taken in the process to obtain a high quality ingot.
Toward to the front high brand of customized project lighting for hotel, club and other high end places.
China Branch Chandelier--Lavius,Rope Chandelier supplier & manufacturer, offer low price, high quality Geometric Chandelier,Square Chandelier, etc.
With VR showroom and factory, see everything directly
Branch Chandelier,Rope Chandelier,Geometric Chandelier,Square Chandelier
GUANGDONG LAVIUS LIGHTING CO., LTD. , https://www.laviuslighting.com