美国尼伯科是美国最大的额定压力球墨铸铁阀门制造商。美国尼伯科多转阀门非常适用于许多应用领域：烃类，化学制品，船舶，消防防火，纸浆和造纸等行业中可以安装铸铁或铸钢阀门的地方。
　　NIBCO is the largest United States manufacturer of pressure rated Ductile Iron Valves. NIBCO’s Ductile Iron multi-turn valves are ideal for a wide variety of services: hydrocarbons, chemical, marine, fire protection services, pulp and paper applications where cast iron and/or cast steel valves could be installed.
　　作为钢的替代品，1949年人类开发了球墨铸铁。铸钢含碳量少于0.3%，而铸铁和球墨铸铁含炭量量则至少为3%。铸钢中的低含碳量使得作为游离石墨存在的碳不会形成结构薄片。铸铁内的碳天然形式是游离石墨薄片形式。在球墨铸铁内，这种石墨薄片通过特殊的处理方法变化成微小的球体。这种改进后的球体使得使得球墨铸铁比铸铁和钢相比具有更加优异的物理性能。正是这种碳的球状微观结构，使得球墨铸铁具有更加良好的展延性和抗冲击性，而铸铁内部的薄片形式导致铸铁没有展延性。通过铁素体基体可获得最佳的展延性，因此，所有美国尼伯科球墨铸铁的压力负载部件都经过铁素体化退火周期的工艺处理。球墨铸铁内部的球状结构也能够消除铸铁内部的薄片石墨容易产生的裂缝现象。在球墨铸铁的微观照片中，可以看见裂缝游行到石墨球后终止。在球墨铸铁行业内，这些石墨球称为“裂缝终结者”，因为它们具有阻止断裂的能力。
　　Ductile Iron, also known as nodular iron, was developed in 1949 as a substitute for steel. Cast steel contains carbon of less than .3% by weight, while cast and ductile irons have at least 3% total carbon. This low carbon content in cast steel does not allow the carbon to form as free graphite resulting in a laminate type of structure. The natural form of carbon in cast iron is the free graphite flake form. In Ductile Iron, this graphite flake is modified by a specialized treatment process to form tiny spheres or nodules. These modified graphite nodules provide Ductile Iron with physical properties greater than cast iron and comparable to steel. It is this nodular microstructure of carbon in Ductile Iron which produces high ductility and shock resistance while the flake form of cast iron results in no malleability. Optimum ductility is obtained with a ferritic matrix, therefore, all NIBCO’s Ductile Iron pressure containing parts are treated with a ferritizing annealing cycle. In Ductile Iron spheroidal nodules also eliminate the crack effect of flake graphite which is exhibited in cast iron. In microscopic photos of Ductile Iron, cracks can be seen traveling to a graphite nodule and stopping. These graphite spheroids are know as “crack arresters” in the Ductile Iron industry because of their ability to stop cracks in their tracks.
　　有时，球墨铸铁被称为“两个世界里最好的”金属，意思是球墨铸铁具有铸钢的强度，也有铸铁优异的抗腐蚀性。
　　In some circles, Ductile Iron is known as the metal that is the “best of both worlds” meaning that Ductile Iron combines the superior strength of cast steel with the excellent corrosion resistance of cast iron.

球墨铸铁与铸铁（灰铸铁）的比较
Ductile Iron vs. Cast (Gray) Iron

　　与铸铁相比，球墨铸铁在强度方面具有绝对的优势。球墨铸铁的抗拉强度是60k，而铸铁的抗拉强度只有31k。球墨铸铁的屈服强度是40k，而铸铁并没有显示出屈服强度，并且最终出现断裂。球墨铸铁的强度-成本比远远优于铸铁。(请参阅83页有关机械性能的全面比较)。球墨铸铁在耐腐蚀性方面与铸铁相同。
　　The strength of Ductile Iron when compared to cast iron is overwhelming. Ductile Iron tensile strength is 60k versus cast iron at 31k. Ductile Iron has a yield strength of 40k, whereas cast iron exhibits no yield, only ultimate fracture. Ductile Iron strength-to-cost ratio offers greater value for a marginal increase in cost over cast iron. (See page 83 for a complete comparison of mechanicals.) Ductile Iron offers excellent corrosion resistance that is equivalent to cast iron.

球墨铸铁与铸钢的比较
Ductile Iron vs. Cast Steel

　　球墨铸铁的强度和铸钢的强度是可比的。球墨铸铁具有更高的屈服强度，其屈服强度最低为40k，而铸钢的屈服强度只有36k。(请参阅83页有关机械性能的全面比较)。在大部分市政应用领域，如：水、盐水、蒸汽等，球墨铸铁的耐腐蚀性和抗氧化性都超过铸钢。由于球墨铸铁的球状石墨微观结构，在减弱振动能力方面，球墨铸铁优于铸钢，因此更加有利于降低应力。选择球墨铸铁的一个重要的原因在于球墨铸铁比铸钢成本低。球墨铸铁的低成本使得这种材料更加受欢迎，铸造效率更高，也较少了球墨铸铁的机加工成本。
　　The strengths of Ductile Iron and cast steel are comparable. Ductile Iron has a higher minimum yield strength at 40k versus cast steel at 36k. (See page 83 for a more complete comparison of mechanicals.) Ductile Iron has corrosion and oxidation resistance that surpasses cast steel in most general utility service applications, i.e. water, saltwater, steam. Because of Ductile Iron’s spheroidal graphite microstructure, Ductile Iron is superior to steel in its ability to deaden vibration and therefore reduce stresses. An important factor in selecting Ductile Iron over cast steel is cost. The lower expense of Ductile Iron results from readily available materials, foundry operation efficiencies and reduced machining costs of Ductile Iron.