问题 问答题 简答题

氧气转炉为什么要采取复合吹炼?

答案

参考答案:

顶吹转炉熔池钢水搅拌主要依靠碳氧反应生成一氧化碳。其次才是氧气射流冲击。因此,开吹后冶炼前期和后期,特别低碳钢种、碳氧反应减弱,使搅拌力大减,这样就出现钢液成分、温度、氧化性不均匀。与此相反底吹氧气转炉熔池搅拌不成问题,但炉渣氧化性弱极不易去磷。人们发现氧气转炉采用复合吹炼既能保持顶吹和底吹转炉的吹炼优点,又能克服顶吹和底吹的冶炼过程中的缺点。

填空题
阅读理解

阅读理解。

     Before a new type of airplane goes into service,every part of it

is tested again and again. But there are two tests that are more

important than all the others.

        The first is called the" tank test". A modern airplane must fly

very high in the sky. Air must be pumped into the plane so that the

passengers can breathe. The metal structure(结构) of the plane has

to be very strong for this reason. When the plane is filled with air,

the air presses against the skin of the plane inside. The pressure (压

力) on a small window is like a huge foot that is trying to get out. If

a small part of the plane were to fail,the plane would explode in the

sky. To test the structure of the plane, the plane is lowered into a

huge tank or container of water. Then it is filled with air. The pressure

inside the plane is greater than it ever will be when it is high

up in the air. Finally,there is an explosion. This does not cause so

much damage inside the water tank as it would anywhere else.

Engineers can discover which part of the plane has broken. Then that

part is made stronger.

     The most dangerous test happens when the new plane is going

through test flights in the air. The test pilot must find out exactly

what happens when the engines(发动机) are all shut off at once.

The plane begins to fall like a stone. It is the pilot's job to find out

how he can get control of the plane again. These two tests are

examples of how planes are made safe before they ever carry passengers.

1. By doing the"tank test" ,the engineers can find out___. 

A. the amount of air in the plane

B. the strength of the plane structure

C. the pressure inside and outside the plane

D. the power of the airplane engines

2. What will happen to the plane under the "tank test" ?     

A. It will be broken.

B. It will be made stronger.

C. It will be filled with water.

D. It will be tested by pilots.

3. According to the text,why are test flights most dangerous?   

A. The plane may explode in the air.

B. The pilot may lose control of the plane.

C. The engines may be damaged.

D. Too much air may get into the plane.

4. What might be the most suitable title for the text?  

A. Two Important Tests on Airplanes.

B. The Importance of Flying Safely.

C. The Danger of Testing Airplanes.

D. How Airplanes Are Made and Tested.