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Ductile iron pipe is a pipe commonly used for potable water distribution and the

Ductile iron pipe

pumping of sewage. The predominant wall material is ductile iron, a spheroidized graphite cast iron, although an internal cement mortar lining usually serves to inhibit corrosion from the carried water and various types of external coating are used to inhibit corrosion from the environment. Ductile iron pipe is a direct development of earlier cast iron pipe which it has now completely superseded. Ductile iron has proved to be a better pipe material, being stronger and more fracture resistant; however, like most ferrous materials, it is susceptible to corrosion, and retains some brittle characteristics.Relatively recent developments such as polyethylene sleeving and/or zinc and polymer coatings and prior to that, cement mortar linings, have done much to mitigate corrosion concerns and a typical life expectancy is in excess of 75 years.

Dimensions
Ductile iron pipe is sized according to a dimensionless term known as the Pipe Size or Nominal Diameter (known by its French abbreviation, DN). This is roughly equivalent to the pipe's internal diameter in inches or millimeters. However, it is the external diameter of the pipe that is kept constant between changes in wall thickness, in order to maintain compatibility in joints and fittings, and consequently the internal diameter does vary, sometimes significantly, from its nominal size. Nominal pipe sizes vary from 3 inches up to 64 inches, in increments of at least 1 inch, in the USA.

Pipe dimensions are standardised to the mutually incompatible AWWA C151 (U.S. Customary Units) in the USA, ISO 2531 / EN 545/598 (metric) in Europe, and AS/NZS 2280 (metric) in Australia and New Zealand. Although both metric, European and Australian are not compatible and pipes of identical nominal diameters have quite different dimensions.

球墨铸铁管（Ductile Cast Iron Pipes）
　　定义：使用18号以上的铸造铁水经添加球化剂后，经过离心球墨铸铁机高速离心铸造成的管道，称之为球墨铸铁管，简称为球管、球铁管和球墨铸管等。
　　特点：具有铁的本质、钢的性能，防腐性能优异、延展性能好，安装简易、主要用于市政、工矿企业给水、输气等。
　　化学成分：球墨铸铁管的主要成分有碳、硅、锰、硫、磷和镁等。
　　金相组织：在铁素体和珠光体基体上分布有一定数量的球状石墨，根据公称口径及对延伸率的要求不同，基体组织中的铁素体和珠光体的比例有所不同，小口径的珠光体比例一般不大于20%，大口径的一般控制在25%左右。
　　力学性能：最小抗拉强度：420/Mpa，最小屈服强度300/Mpa，最小延伸率7%
　　执行标准：GB/T13295-2003 ISO2531/2003
　　口径：DN80-DN2600
　　历史：1947年英国H.Morrogh发现，在过共晶灰口铸铁中附加铈，使其含量在0.02wt%以上时，石墨呈球状。1948年美国A. P.Ganganebin等人研究指出，在铸铁中添加镁，随后用硅铁孕育，当残余镁量大于0.04wt%时，得到球状石墨。从此以后，球墨铸铁开始了大规模工业生产。有关球墨铸铁管的使用历史可以追溯到1668年巴黎郊区从塞纳河至凡尔赛全场约21.14Km的输水管线，300年的时光流逝，除部分管道和接头维修更换外，主体至今仍在使用。
　　我国球墨铸铁管的现状及前景：
　　我国的球墨铸铁管行业起步于20世纪90年代初，在中国城镇供水协会的大力支持下发展迅猛，经过近20年的实践使用，其安全性、实用性已被供水行业普遍认可，2008年国内年产量已达到220万吨，是1990年的11倍。由于我国是一个水资源缺乏的国家，缺水城市为600多个，严重缺水城市为200多个，供水节水事业方兴未艾，球墨铸铁管有着广阔的发展前景。
　　优缺点：
　　优点：在中低压管网，球墨铸铁管具有运行安全可靠，破损率低，施工维修方便、快捷，防腐性能优异等。
　　缺点：由于管体相对笨重，安装时必须动用机械。
　　我国最大的球墨铸铁管生产基地是位于河北省邯郸市的新兴铸管股份有限公司，年产球墨铸铁管150万吨，配套管件5万吨，产品曾成功应用于太原引黄工程、兰州引黄工程、南京市江宁供水工程、西安城市水环境治理二期工程、宝鸡城市应急供水工程等国家和地方重点工程建设，以过硬的质量、良好的服务赢得用户的普遍认可，是目前国内公认的行业龙头企业。