问题 问答题 论述题

电厂过热器管和主蒸汽管的用钢要求如何?

答案

参考答案:(1)过热器管和蒸汽管道金属要有足够的蠕变强度,持久强度和持久塑性,通常在进行过热器管强度计算时,以高温持久强度极限为主要依据,再以蠕变极限来校核,过热器和蒸汽管道的持久强度高时,一方面可以保证在蠕变条件下的安全运行,另一方面还可以避免因管壁过厚而造成加工工艺和运行上的困难。

(2)要求过热器管和蒸汽管道金属在长期高温运行中组织性质、稳定性好。

(3)要有良好的工艺性能,其中特别是焊接性能好,对过热器管还要求有良好的冷加工性能。

(4)要求钢的抗氧化性能高,通常要求过热器和蒸汽管道在金属运行温度(即管壁温度)下的氧化深度应小于0.1mm/年。

单项选择题
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In modern society there is a great deal of argument about competition.Some value it highly, believing that it is responsible for social progress and prosperity.Others say that competition is bad, that it sets one person against another, that it leads to unfriendly relationship between people.

I have taught many children who held the belief that their self-worth relied on how well they performed at tennis and other skills.For them, playing well and winning are often, life-and-death affairs.In their single-minded pursuit of success, the development of many other human qualities is sadly forgotten.

However, while some seem to be lost in the desire to succeed, others take an opposite attitude.In a culture which values only the winner and pays no attention to the ordinary players, they strongly blame competition.Among the most vocal are youngsters who have suffered under competitive pressures from their parents or society.Teaching these young people, I often observe in them a desire to fail.They seem to seek failure by not trying to win or achieve success.By not trying, they always have an excuse: "I may have lost, but it doesn't matter because I really didn't try."What is not usually admitted by themselves is the belief that if they had really tried and lost, that would mean a lot.Such a loss would be a measure of their worth. Clearly, this belief is the same as that of the true competitors who try to prove themselves.Both are based on the mistaken belief that one's self-respect relies on how well one performs in comparison with others.Both are afraid of not being valued.Only as this basic and often troublesome fear begins to dissolve (缓解) can we discover a new meaning in competition .

小题1:What does this passage mainly talk about?

A.Competition helps to set up self-respect.

B.Opinions about competition are different among people.

C.Competition is harmful to personal quality development.

D.Failures are necessary experiences in competition.小题2:Why do some people favor competition according to the passage?

A.It builds up a sense of duty.

B.It pushes society forward.

C.It improves personal abilities.

D.It encourages individual efforts.小题3:The underlined phrase "the most vocal" in Paragraph 3 means ____.

A.those who try their best to win

B.those who value competition most highly

C.those who are against competition most strongly

D.those who rely on others most for success小题4:What is the similar belief of the true competitors and those with a "desire to fail"?

A.One's worth lies in his performance compared with others'.

B.One's success in competition needs great efforts.

C.One's achievement is determined by his particular skills.

D.One's success is based on how hard he has tried.小题5:Which point of view may the author agree to?

A.Every effort should be paid back.

B.Competition should be encouraged.

C.Winning should be a life-and-death matter.

D.Fear of failure should be removed in competition.