问题 问答题 简答题

铸件的内浇道开设的原则是什么?

答案

参考答案:

(1)内浇道在铸件上的位置和数目应服从所选定的凝固顺序或补缩方法

a同时凝固:内浇道在薄壁处,数量多且分散分布。

b顺序凝固:内浇道开在厚壁或冒口处

c复杂铸件:采用顺序凝固与同时凝固相结合的原则。

(2)方向不要冲着细小砂芯、型壁、冷铁和芯撑

(3)内浇道应尽量薄。

(4)对薄铸件可用多内浇道的浇注系统实现补缩。

(5)内浇道避免开设在铸件品质要求很高的部位。

(6)各内浇道中金属液的流向应尽量一致。

(7)尽量开在分型面上。

(8)对收缩大易裂纹的合金铸件,内浇道的设置不应阻碍收缩。

阅读理解

I have returned to my hometown after I was away ten years ago. So many things have changed around here. It has become better and better. When I left here, there was a small pool on the right of my house. Now the pool has gone and people have built a large shopping mall(商场) there.

The biggest changes have taken place in the center of the city. There are sidewalks on both sides of the street. You can see a street center with so many tall buildings around. You can’t drive there any more because no vehicle is allowed to pass there. A European-style fountain(喷泉) has been built in the street center garden.

There used to be an old school near my house. I spent my five years studying there. There was a small payground in front of the school. But now what I can see are five tall buildings standing there. There are two big classroom buildings and a library. A new post office has also been built just across from the new school.

小题1:I have been away from my hometown for ________.

A.ten months

B.one year

C.five years

D.ten years小题2:On the right of my house, there was a _________ ten years ago.

A.library

B.garden

C.supermarket

D.pool小题3:No vehicle is allowed to pass the _________.

A.center of the city

B.old school

C.street center

D.playground小题4:Which of the following is WRONG(错的)?

A.A fountain is in the street center garden.

B.Now there is an old school near my house.

C.There are two big classroom buildings and a library in the new school.

D.There is a post office across from the school.小题5:What’s the best title for the passage?

A.Great Changes in My Hometown.

B.A Wonderful Place

C.What a Nice Town

D.My School.

多项选择题