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试述Cr5Mo钢的焊接工艺特点？

答案

参考答案：

CrMo钢属珠光体耐热钢，可焊性较差，采用同材质焊条，焊接工艺复杂，要求焊前预热，预热后处理，可以获得良好的组织。如采用奥氏体钢焊条施焊，虽工艺简单，但在熔合区存在脆硬层，可靠性较差。

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5000000克=______千克=______吨．
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Americans are often in a hurry. They rush to work, rush home, and rush through their meals. Workers and students usually have only half hour or an hour for lunch. As a result, a lot of Americans go and eat in fast food restaurants. The service is quick, and the prices are cheap.
What do fast food restaurants serve Of course, many of them have hot dogs, hamburgers, fried chicken, pizza, or ice cream. But other fast food restaurants specialize (专门从事) in different foods. Some places serve roast beef. Some serve fish and seafood. In fact, you can find popular foreign dishes in fast food restaurants, too. There are Italian restaurants with Italian sausage (香肠) and spaghetti (通心粉). And there are Chinese restaurants with Cantonese (粤式的) or Sichuan foods.

When do Americans usually go to fast food restaurants
[A] At breakfast time.[B] At lunch time.
[C] At lunch and dinner time. [D] At dinner time.

A lot of fast food restaurants are franchises (产品经销特许权), a very popular form of business in the United States. There are many restaurants in a franchise, and each franchise has a different owner. However, all of the restaurants are under one central management, and the name of the restaurants is the same everywhere in the United States — and in foreign countries, too. This kind of central control guarantees that, for example McDonald’s hamburgers and Kentucky Fried Chicken taste the same everywhere.
In modern American life, fast food restaurants are very important. They provide quick and inexpensive meals for American people in a hurry.
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