铸件壁间转角处为何要设计结构圆角？
参考答案：
1.直角连接处形成金属积聚，而内侧散热条件差，较易产生缩松和缩孔。
2.在载荷作用下，直角处的内侧易产生应力集中。
3.直角连接时，因结晶的方向性，在转角的分角线上形成整齐的分界面，分界面上集中了许多杂质，使转角处成为铸件的薄弱环节。
4.圆角连接可美化铸件外形，避免划伤人体。
5.内圆角可防止金属液流将型腔尖角冲毁。
摘录信息（共5小题；每小题2分，满分10分） 阅读下面短文，根据所读内容在文后第53至第57小题的空格里填上适当的单词或短语，并将答案转写到答题卡上。 注意：每空不超过3个单词。 Some beach creatures are wonderful -- like dolphins, but others are dangerous. Here are some examples of harmful beach creatures. Puffer Fish Puffer Fish, found in all Japanese seas, have very interesting features. They are very easy to catch but must not be eaten because their flesh and organs contain a poison. Anyone who does eat the flesh can become sick very quickly. They may even stop breathing. The Blue Bottle The Blue Bottle is found in most Caribbean waters. Blue Bottles float lightly on the surface of the water but their tentacles (触须) can be as long as 10 metres. Blue Bottles are much less dangerous than some other jellyfish but they can give a swimmer a bad sting (刺) if the swimmer accidentally touches them. Stingrays There are many different kinds of stingrays in Mauritius waters. They usually swim and feed on the bottom of the sea. Accidents can happen if people stand on them or try to pick them up. Stingrays have a sting on their tail. These stings have poison on them. If someone is stung the wound can easily become infected. Title : 53
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