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，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后，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。

As a substitute for steelin 1949,the human development ofductile cast iron.Less than 0.3% carbon steel,while thecast iron andductile iron with carboncontent the amount of at least 3%.Low carbonsteel makesasfree graphitecarbonsheet structure will not form.The natural form of carbonin cast iron is the freegraphite flake form.In ductile iron,thegraphite flakeschange through special processing methodsinto a tiny ball.The improvedball made of cast iron makeshas physical propertiesgreater than cast iron andsteel.It is this nodular microstructure ofcarbon,thenodular cast ironhas better extension andimpact resistance,whilethe flake form of cast iron resultsnoductility.To obtainthe bestductility,theferrite matrixtherefore,ductile iron pressurecontaining parts aretreated with a ferritizingannealingcycle,ductile iron spheroidal nodulesalso eliminatethe crack phenomenonof flake graphitecast ironinternalprone.Inmicroscopic photos of ductile iron,can see thecracks in the procession to theball after thetermination ofgraphite.In the ductile iron industry,thegraphiteballcalled “crackterminator ”,becauseof their ability to prevent breakage.

　　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。

Compared with cast iron,ductile iron hasthe absolute advantagein strength.Tensile strength of cast iron is60K,while the tensile strength of cast ironis only 31k.The yield strength of ductile iron is40K,and theirondid not showthe yield strength,andultimate fracture.Ductile ironstrength-to-cost ratiois much better than that ofcast iron.

　　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。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 strength of ductile iron andsteel strength is comparable.Ductile iron has a higheryield strength,yield strength minimum of 40K,while the yield strength of steel isonly 36k.In most municipal applications,such as: water,salt water,steam,ductile ironcorrosion and oxidation resistancethancast steel.Asthe spherical graphite cast iron microstructure,the decrease vibration capability,ductile iron better than steel,therefore more conducive to reducing stress.Chooseone of the important reasonsof ductile cast ironisductile ironcastinglow costratio.The low costof nodular cast ironmakes the material more popular,casting more efficient,lessthecost of machiningductile cast iron.