The micro thermal crack source main defects is analyzed
the micro thermal crack source analysis of 5 main defects. 2. 2. # 1 crack crack forms, production/reason is not the same, FLL, uniform, Ii in Shanghai/ll once, eight/llfill t * I, less, the stress of large t· 。 In the process of its material casting, in & middot; Contractual terms bligh & # 39; , each & middot; Kind of alloy has its, I & # 39; II some liquidus and due to the phase line, and 'product t & middot; T have a corresponding two-phase coexisting 【 , only. In two phase zone l· , department, the liquid phase is more, I, ll l material is less, known as the liquid in the cutting area in two phase area initiation and development form, referred to as thermal crack; Such as: fruit is in the Material, lil liquid 1 l, l ll shadows I / # and development or a source of initiation of micro cracks in the liquid zone, and developed into the crack in the solid phase, referred to as cold crack, and in/t production practice, the majority of crack as hot cracking, and most of the cold crack, also by the micro thermal crack source or caused by fire, the source of crack development of form, is in phase II of cold and hot cracking criterion hot crack crack width is not two golden brown or dark gray, towards the twists and turns along the product bound by throughout the last solidification place; Always have low melting point material filling. Cold crack is light gray or light gray; LieKuan degree is, the difference is not big, rarely split crack transgranular through more; How distribution where the tensile stress in the biggest recipients of cold crack crack defects belong to malignant. Every crack detection and the whole furnace or the entire cast time scrap; Or check (200% of ingot The ingot two sampling inspection) Delivery of the goods, to ensure that no crack, to doubt all do scrap processing. The crack is often the main defects in casting. Aluminum processing technology workers for ingot casting crack has carried on the investigation and study of the long-term, made important progress, summed up the effective technical measures to prevent or control the occurrence of cracks. A control of chemical composition, to eliminate or reduce the crack control of the chemical composition of the main methods ( 1) The iron content of silicon ratio control to prevent the ingot casting crack. According to the different alloy, along the phase transformation condition, improve the brittleness of solid-liquid area, prevent the crack I) For Si < 0. 35% of industrial pure aluminum, AI - Mn alloy, Si not as A1 alloy elements - M aluminum alloy. Al - Mg content greater than 1% Cu- Mg alloy, A1 - Zn- Mg alloy, A1 - Zn- Mg- Cu alloy, regulating the chemical components in Fe> lili. Its role is the narrow temperature range in solid liquid. Aluminum processing, such as Si < 0. 35% of industrial pure aluminum, when Si> Fe, the unbalanced solidus temperature of 577 art, and Fe & middot; Si, the temperature can be increased to 611 ℃, makes the solid liquid temperature range narrowed the 34 cc. All of the thermal crack is caused by solidification shrinkage stress in solid-liquid area. Metal line contraction in the crystallization process starts, effective bugs interval crystal ceiling temperature until the end of the lower limit of effective crystallization range temperature. Its chemical composition, to adjust the expression of solidification crystallization change before paragraph 8 s LAN LiuJiu A fly the ending lamp XiDing box to account for.