Analysis of the sintering cavity defects in gas machine cylinder head

by:XEX     2021-02-22
Gas machine two valve cylinder head is on the basis of the original two valve diesel engine cylinder head, by improving the string structure and water injector structure based on the development of new products, is a WP10 series of monomers, gas engine cylinder head, is made of cast iron HT250, cast iron is 225 mmx149mmx125mm dimensions, 20 blank quality. 75公斤。 Cylinder head production precision casting using the intermediate frequency electric furnace smelting process, the pouring temperature of 1400 ℃ ~ 1430 ℃, HWS automatic pouring casting, core group is composed of seven kinds of sand core, the change of the structure of the nozzle core and core water interlayer adopts high-temperature coated sand hot core box core-making process, the shape of membrane sand molding process, 8 per box, type gating system for ladder, as the bottom note and the note in the combining form, is beneficial to improve the stability of iron liquid filling, avoid the casting is easy to produce the precision casting defects such as porosity, local sintering. Problems and analysis for gas cylinder head under heat load is high, in order to prevent copper set of technology on injector position high leakage rate caused by quality problems, the cylinder head design, compared with the former two valve cylinder head of diesel engine, fuel injector position with casting process, as shown in figure 1, at the same time to optimize the flow of cooling water, change the water partial structures of composite laminated core, cylinder head, when mass production, change position. Plenty of sintering defects, fine clear difficulties, not fine, because of the inner cavity of substandard rejection rate as high as 0. 42%. Figure 1 injector position using casting technology injector sintering defects as shown in figure 2, compared to the original two valve cylinder head of diesel engine, fuel injector liner of the forged structure, cast out the injector liner diameter of 30 mm ( Note the injector liner position after cooling processing forming, precision casting for all solid structure) , surrounded by cooling water channel is only 7 mm, the thinnest place belongs to the thin wall position, after high temperature molten iron to burn note, because of the size of sand core is weak and the sand wick, lateral were high temperature iron liquid package, under the hot action of high temperature molten iron, sand core surface crack formed by the transformation occurred cracking of quartz sand, metal seeping into the pulse formation, and because of its high temperature hot enough heat to ensure the cores and the interface of the temperature of molten iron is higher than the solidus temperature of iron, this will continue, penetration once started only penetrate the forefront of iron liquid solidification, penetration, so that metal by sand core crack or pore penetrated the whole cross section of the core to form the so-called core sintering. This kind of defect is not easy to clean up, and thus iron scrap. Figure 2 sintering flaws sheung shui laminated core sintering gas injector machine cylinder head water exhaust duct laminated core end position of the bridge of the nose, the thickness of the sand core just 4. 5 mm, as shown in figure 3, is the most weak position, sheung shui laminated core and core high temperature iron liquid height is above 30 mm, as shown in figure 4, significantly thicker than the bottom, iron liquid cooling speed is slow, sand core under the effect of high temperature of iron liquid for a long time, prone to sintering, serious when the department of position, sintering blocking channel plugging and water of the string, influence the cylinder head water cooling, cause engine failure, the other as shown in figure 5, 6, veins defects, because of the limitation of casting structure, the corresponding position of sintering and fat grain defects can't clean up, can only artificial using endoscopic equipment for inspection, cause a lot of manpower and material resources waste. Figure 3 weak interlayer core drawing up 4 weak position chart 5 cores sintering block figure 6 cores veins defects
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