Table 3. Penetration and Veining Rankings 表 渗透ո毛Ӵ等ঃ
Sample ID 样ռ/*
Baseline Silica 砂硅ӕׂ
Silica w 10% Zircon խ有 锆ਸ਼砂ङ硅砂
Silica w 20% Zircon խ有 锆ਸ਼砂ङ硅砂
Silica w 30% Zircon խ有 锆ਸ਼砂ङ硅砂
Silica w 40% Zircon խ有 锆ਸ਼砂ङ硅砂
Silica w 7.5% Chromite խ有 铬铁矿砂ङ硅砂
Silica w 10% Chromite խ有 铬铁矿砂ङ硅砂
Silica w 30% Chromite խ有 铬铁矿砂ङ硅砂
additives promote the sintering of the surface of the core and forms a partially melted surface. Tis increases the rigidity of the surface due to the increase in the viscosity of the sintered surface. Te increase in viscosity at higher temperatures leads to higher strengths on the surface of the core, thereby resulting in reduced core distortion. Previous research has shown the veining defect in cores and molds is a result of a tensile stress exerted at the mold metal interface by a combination of contracting sand and subsur- face expanding sand. Tis tensile stress is created by the loss of volume observed in silica sand after the alpha-beta phase transition at 1,063 F (573C). Tis leads to a network of cracks formed due to the high thermal expansion of silica sand. Tese cracks then are filled by the liquid metal, which forms veins on the surface of the casting. Specialty aggregates have a lower thermal expansion when
compared to silica sand, which will prevent cracks being formed on the surface of cores and reduce veining defects. A major limitation is their high cost. For most applications, a small improvement in the high temperature physical proper- ties of silica sand will be more viable for good casting quality. Research was conducted to evaluate the effect of the addition
Veining Index 毛Ӵ指数
43 0 9 9 5 0 - -
砂д高提，加增چডЈچ温高较֨。加增Ф随Эچॆ 。量形ՊङਯдѺ降৲֜，چ强面੮ਯ Фӹङू९੮明，ਯ腔չ铸型ӄङਉ়缺陷是ंй 加施面उً金И型铸֨合ৈ胀膨չঢ়收面੮砂型过通 生ՇЈچ温）℃ ℉（ ֨。ङ成造力应ѵ拉ङ ѵ拉य़这д成形љ۱ע损॥ѽ现ӟ砂硅，եՊबŜ ś ً金ہ液。ৠ়裂य़一д成形胀膨温高ङ砂硅。力应 缺়ਉ成形面੮ў铸֨৲进，়裂п这д进ҭ填ե随 陷。
ਯ砂止防לਈ，Ѻ较性胀膨热砂य़特，比ब砂硅Њ 成是Ӳ限键ҼҿѸ。陷缺়ਉصӗ并成形ङ়裂面੮ ब量ૅў铸ङ高更Њ，ઈ৲用应ӣ部םйث。高较本 ՕО更Чѷ进改ش微ӟҟૅ性理物温高ङ砂硅ث，比 ੧。
特加添ӄ砂硅֨ѳછ，९ूд੧进մы९ू，此֜ ，९ूд੧进剂加添ङ型ঝय़ДثӰӣ。果效ङ砂य़ 殊特य़一是砂ਸ਼锆ङ用采۱。砂矿铁铬չ砂ਸ਼锆括包
Fig.6. The baseline silica casting is shown.
ׂдॐي֣本 ֣ ӕ硅砂铸ў。
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FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION March 2017
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