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Tap Handle Metal Casting defect analysis
Source£ºadmin   Added£º2009-12-14    Click£º698
A hot crack 1.1 The occurrence of the Cover the bottom of handle. 1. Handle heart 2. Handle cover 3. Handle the 4. Hot section 5. Crack 1.2 Causes As the copper-zinc content of the lower fluid, and the cast appear before the bottom right-angle, casting in the solidification contraction by metal type, core obstacles, in casting the next face at right angles to have a large concentration of shrinkage stress, so often cast the formation of heat in the area crack. 1.3 Measures taken by 1.3.1 Casting Design Improve casting structure at right angles into the next end-rounded to prevent crack defects. 1.3.2 Alloy Melting Melting, it is necessary to strictly control the chemical composition of alloys, zinc alloys to be appropriate, too much is easy to produce cold cracking, is easy to produce low thermal cracking. As the zinc smelting process of burning, shall be added to zinc ingots to ensure that the appropriate chemical composition: w (Cu) ¡Ö 59%, w (Zn) ¡Ö 38%. 1.3.3 Process Control Improving metal type, core temperature, the corresponding reduction of the casting shrinkage stress, can reduce the hot tearing tendency. Metal type, core suitable preheat temperature 350 ~ 400 ¡æ, operating temperature of 250 ~ 300 ¡æ. 2 pinhole 2.1 The occurrence of the Casting on the surface layer appeared irregular concentration of a single or a few needles size of less than 1 mm in diameter and have a certain length (1 ~ 2 mm) of the pinhole, as shown in Figure 2. 2.2 The reasons for the formation of Handle metal casting using all-metal type, metal core, the handle was mainly due to the surface of the mold exhaust pinhole poor casting mold of copper in the residual liquid and water vapor react with the gases produced by the solidification cooling process can not smooth and timely discharge, the formation of pinholes in the casting surface. 2.3 The measures taken in response 2.3.1 Mold Design Mold design should carefully consider the exhaust channel can make use of large core and small core (handle heart) a combination of space exhaust, in the handle to the end of the opening of the exhaust riser, the mold surface of the distribution of sub-type 0.5 mm deep, flat seam -shaped exhaust ducts, mold core set up the first seat at the triangle slot depth 1.5 mm. 2.3.2 Alloy Melting Strengthen the alloy refining, to improve the purity of alloy to reduce the alloy containing gas and slag material. Found in the production, refining and appropriately reduce the alloy pouring temperature is to reduce the thermal cracking, pinhole, to prevent shrinkage, and shrinkage of the effective measures. So pouring temperature control (970 ¡À 10 ¡æ) or so more appropriate. Rare earth metals in the copper solution to purify and metamorphism. In the copper solution by adding 0.03% ~ 0.05% of the mixed rare earth can be dehydrogenation, remove impurities, refine grain and improve the casting properties of alloys, thereby reducing the casting pinholes, cracks tend to improve the casting quality and yield. 2.3.3 Process Control (1) regulating the turning speed of casting machine will be controlled within 4 s pouring time around, so that a smooth liquid metal into the cavity in order to facilitate the smooth discharge of gas. (2) metal-type stick graphite coating is to improve the casting surface quality, effective measures to prevent pinhole. Metallic surface layer of graphite paint stick to liquid metal solidification new to cast it without immediately, so that gas can be uneven between the metal and coating the surface of escape, but also slow cooling molten metal, so metal-type stick graphite coating is to improve the casting One of the key surface quality. (3) before casting to metal type, within the core surface and runner debris, thoroughly clean the surface rust and eliminate the root causes of the production of gas. James graphite metallic paint, the finish to wait until complete evaporation of water, and then mold casting. 3 shrinkage and shrinkage 3.1 The occurrence of the Casting Hot Spot Service, within the gate roots. 3.2 The reasons for the formation of Inside the gate to open hot spot in the casting office to form a thermal contact section, an increase of gate section feeding on the thermal interference, thereby increasing the hot spot at the shrinkage and shrinkage, so casting shrinkage and easy to produce in the area Shrinkage. 3.3 Preventive Measures 3.3.1 within the gate to be opened to deviate from the hot spot at casting. 3.3.2 mold design to consider strengthening the hot spot at the cooling rate, in the mold hot section of office inlaid copper block chilled to improve the hot spot at the cooling rate, to prevent the casting resulting shrinkage shrinkage defects. Gravity die casting metal handle is a kind of high quality requirements, casting, when situations such as thermal cracking, pinholes, shrinkage, and shrinkage defects such as should be from the mold design, alloy melting and process control to be a comprehensive analysis of three aspects, a comprehensive solution can effectively overcome the casting defects, improve casting quality and yield. 
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