球墨井蓋上的C250是什么意思，有什么含義嗎？
What does C250 on the nodular well cover mean and what does it mean?
球墨井蓋是球墨鑄鐵產品的一種，球墨鑄鐵通過球化和孕育處理得到球狀石墨，有效地提高了鑄鐵的機械性能，特別是提高了塑性和韌性，從而得到比碳鋼還高的強度。球墨鑄鐵是20世紀五十年代發展起來的一種高強度鑄鐵材料，其綜合性能接近于鋼，正是基于其優異的性能，已成功地用于鑄造一些受力復雜，強度、韌性、耐磨性要求較高的零件。球墨鑄鐵已迅速發展為僅次于灰鑄鐵的、應用十分廣泛的鑄鐵材料。所謂“以鐵代鋼”，主要指球墨鑄鐵。
Nodular well cover is a kind of nodular cast iron. Nodular graphite is obtained from nodular cast iron through spheroidization and inoculation, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, so as to obtain higher strength than carbon steel. Nodular cast iron is a high-strength cast iron material developed in the 1950s. Its comprehensive properties are close to steel. Based on its excellent properties, it has been successfully used to cast some parts with complex stress and high requirements for strength, toughness and wear resistance. Nodular cast iron has rapidly developed into a widely used cast iron material second only to gray cast iron. The so-called "replacing steel with iron" mainly refers to nodular cast iron.
球墨鑄鐵井蓋中的C250是什么含義呢？
What is the meaning of C250 in nodular cast iron manhole cover?
球墨鑄鐵井蓋C250級指的是：承重約25噸的井蓋球墨鑄鐵井蓋，250：實驗承載250KN（千牛）。按照行業標準， 此雨水井蓋用在次干道的機動車道上。
Nodular cast iron manhole cover C250 refers to the manhole cover with a load of about 25 tons, and the nodular cast iron manhole cover with an experimental load of 250kN (KN). According to industry standards, this rainwater well cover is used on the motorway of the secondary trunk road.
球墨鑄鐵井蓋一般分為圓形和方形，在市區的路政方面，一般采用圓形，因為 圓形的井蓋不易傾斜，能夠較好的保護好行人和車輛的安全。使用圓形，主要是考慮到圓形的井蓋通過其圓心的每條直徑長度都是一樣的，這樣如果井蓋被經過的車輛軋起時，因為不論如何軋起，其直徑都會比下面的井口略寬，井蓋不會掉到井口里去。
Nodular cast iron manhole covers are generally divided into round and square. In terms of urban road administration, circular manhole covers are generally used, because circular manhole covers are not easy to tilt, which can better protect the safety of pedestrians and vehicles. The use of circular covers mainly takes into account that the length of each diameter of the circular well cover passing through its center is the same. In this way, if the well cover is rolled up by passing vehicles, no matter how it is rolled up, its diameter will be slightly wider than the wellhead below, and the well cover will not fall into the wellhead.
而如果采用方形，因為方形的對角線明顯長于其每條邊長，這樣的井蓋被軋起時，很容易沿井口的對角線方向掉進井中，造成安全隱患。如果井口做成圓形或明顯小于井蓋，方形的井蓋就不會掉進井中。這里就牽涉到一個材料的利用和節約的問題。井口的使用取決于井口的大小，如果非要在上面安裝個面積遠遠大于井口的方形井蓋，那么材料的利用和實用價值自然沒有直接使用圓形的井蓋更有效，既節約井蓋的材料，也保證了井口的安全。而在鄉下和電纜井利用的，一般采用方形，這樣可以更好地預防雨水等液體的進入。
If the square is used, because the diagonal of the square is obviously longer than the length of each side, when the well cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, resulting in potential safety hazards. If the wellhead is round or significantly smaller than the well cover, the square well cover will not fall into the well. This involves the problem of maximum utilization and saving of materials. The use of the wellhead depends on the size of the wellhead. If it is necessary to install a square well cover with an area much larger than the wellhead, the utilization and practical value of the material is naturally more effective than using the circular well cover directly, which not only saves the material of the well cover, but also ensures the safety of the wellhead. In rural areas and cable wells, square is generally used, which can better prevent the entry of rainwater and other liquids.
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