问题 问答题 简答题

钢脱碳的危害性是什么?

答案

参考答案:

脱碳使钢的硬度、耐磨性、疲劳强度、冲击韧性,使用寿命等机构性能显著降低,对工具钢,滚珠轴承钢,弹簧钢,高碳钢丝等的质量有更大危害甚至因脱碳超过规定而成为废品。

阅读理解

根据下面一篇短文的内容判断下列句子的正误,正确的用 “A” 表示,错误的用“B”表示。

     Sally was fourteen. She studied in a middle school. She liked dancing and singing and spent a lot of time

on them. But she hated maths and even decided to give it up. Her father was anxious (焦虑) about it.

     It was Sunday. Sally's father gave a call to his sister who taught maths in another school. He hoped she

would come and tell his daughter how to learn maths. The woman came and said,"You are a clever girl, Sally.

I' m sure you will soon learn maths well if you do your best"

     "I'm afraid I can't, Aunt," said Sally. "Girls can't be good at maths."

     "I don't think so," said the woman. "I was good at it when I was a girl. You must do more exercises and

try different ways to practice doing maths problems until you work them out or at least understand them

better. Here is a maths problem. Please think it over and see if you can work it out."

     "OK," said the girl. "Let me try."

     About an hour later Sally took the exercise book to her aunt and said, "I've tried several times and worked

out the problem at last!"

     "Well done!" her aunt looked at her answer and said happily, "Now you see, maths is not as difficult as

you thought."

( )1. Sally tried her best to learn maths but could not learn it well.

( )2. Sally spent much more time in singing and dancing than in learning maths.

( )3. Her aunt didn't think that girls could be good at maths.

( )4. The father asked his sister to teach his daughter how to learn maths.

( )5. Sally worked out the problem at last

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