问题
问答题 简答题
棒材穿水冷却装置的基本原理是什么?
答案
参考答案:
在精轧机后设有一个由数个水冷箱组成的可调水冷段,对棒材进行急剧冷却,使棒材表面形成马氏体组织,在随后的温度恢复过程中,芯部热量散出对表面马氏体组织可产生回火作用,结果棒材表面层为回火马氏体,芯部为细粒珠光体及索氏体组织。这种组织结构使棒材屈服极限和韧性提高,并具有良好的可焊性。
棒材穿水冷却装置的基本原理是什么?
参考答案:
在精轧机后设有一个由数个水冷箱组成的可调水冷段,对棒材进行急剧冷却,使棒材表面形成马氏体组织,在随后的温度恢复过程中,芯部热量散出对表面马氏体组织可产生回火作用,结果棒材表面层为回火马氏体,芯部为细粒珠光体及索氏体组织。这种组织结构使棒材屈服极限和韧性提高,并具有良好的可焊性。
It sounds like a science fiction, but researchers say it’s a scientific fact: Microscopic organisms dubbed "killer algae" are paralyzing fish with unknown toxins and then eating away at their flesh. They might be making people sick, too. The name given to this single-cell organism, or dinoflagellate, is Pfiesteria piscimorte—literally, "fish killer." It was discovered at North Carolina State University in 1988, but at the same time, few scientists believed in its existence, much less in its highly unusual predatory nature. But ongoing research has led to international acknowledgment of the phenomenon and, recently, research funding. Seemingly prompted by an unknown substance secreted by fish, the aggressive creature swims into action. It sends neurotoxins into the water and air, paralyzing a fish’s nervous system, and causing it to gasp for air at the surface. Eventually the fish suffocates. The killer dinoflagellate then attaches itself to the fish and begins sucking away at its flesh. This macabre scenario may help solve several sea mysteries, such as why fishermen report seeing "fish walks" (fish trying to leave the water) and pools of dead fish with holes eaten through them. Whether humans are affected by the dinoflagellate’s toxin remains to be seen. Researchers think it’s unlikely eating fresh fish are in danger, but anyone with frequent exposure to the creature could be in peril. Several researchers working with the algae have reported bouts of memory loss and disorientation. To understand the killer algae further, scientists must fully characterize their toxin and determine what stimulates them to attack. They also need to know if the algae are hurting fish populations, and whether pollutants make them more likely to attack. |
The word "they" underlined in Paragraph 1 refers to ______ .
A.organisms
B.fish
C.toxins
D.flesh