Using Specialty Sand Blends to Reduce Veining Defects


Research was conducted to evaluate the effect of the addition of specialty aggregates to silica sand.


SAIRAM RAVI AND JERRY THIEL, UNIVERSITY OF NORTHERN IOWA (CEDAR FALLS, IOWA)


陷ভঋ脉شӖ砂म特用҄՟混 。ѳછд੧进果效ङ砂य़特加添ӄ砂硅֨ثմы९ू


M ）斯صध达锡州华荷爱（学ל华荷爱北，2+/.: 9'/8'3 8'</ո0+88?


etal casters continually strive to produce the highest quality castings at the lowest competitive cost. Unfortunately, they have little control of the cost of the required


materials. Molding materials such as chromite, zircon and mullite all exhibit low expansion, leading to few casting defects related to expansion and better dimensional accuracy. Tey also have refractory values significantly higher than silica sand. Although some casting applications require the use of 100% specialty sands, a significant amount require only


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ङ力ж竞有љ要想，ડغ断Љ֨फ一Դ造 最Ѻ成本生фӟ最高ૅ量ङ铸ў。然৲， ङ料材需۱Ӳ控法无Чәћѕ，是ङ幸Љ 有֮料材造铸ঈ砂ीੀਿչ砂ਸ਼锆、砂矿铁铬。本成 ，陷缺造铸Ҽबङ生ф胀膨֜дѺ降，点特性胀膨Ѻ 硅й高םםچ火৳ङ料材п这。چতت尺д高提Ќ并 ֨Ѹ，砂य़特ङ 用҅求要用应造铸п某管ـ。砂 ֜并，ਈ性砂硅֑改ਈ就加添چ适需ՑИ用应数ךם


Fig.1. This shows the thermal expansion of foundry sands.


Table 1. High Temperature Phase Transitions of Silica Sand 表 硅砂高温相Չ


Phase Transition 相Չ


Alpha-Quartz to Beta-Quartz śीਸ਼ӱŜीਸ਼


Beta-Quartz to Beta-Tridymite Ŝीਸ਼ӱŜ鳞ीਸ਼


Beta-Tridymite to Beta-Cristobalite Ŝ鳞ीਸ਼ӱŜ方ीਸ਼


Beta-Quartz to Beta-Cristobalite Ŝीਸ਼ӱŜ方ीਸ਼


Temperature 温度


1,063F (573C) 1,598F (870C) 2,678F (1,470C) 2,678F (1,470C)


Density Change (Volume) ）ऴѼ（化Չ度ؤ


2.65 to 2.53 (+4.74%) 2.53 to 2.25 (+12.44%) 2.25 to 2.20 (+2.27%) 2.53 to 2.20 (+14.71%)


Linear Change 线性Չ化


+1.56% (0.0156 in/in) +3.99% (0.0399 in/in) +0.75% (0.0075 in/in) +4.74% (0.0474 in/in) March 2017 FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION | 45


铸дॐي֣本 ֣ ە胀膨热ङ砂用造 ӑ。


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