Gray iron发表评论(0)编辑词条

Gray iron

Gray iron or grey iron was the original "cast iron". It is an alloy of carbon, silicon, and iron, containing from 1.7 to 4.5% C and 1 to 3% Si. It is relatively easy and inexpensive to make. Compared to the more modern engineered irons, gray iron has a lower tensile strength and lower ductility. In other words, it will fail more easily, and its mode of failure will be sudden fracture (it will not bend). It is used for housings where tensile strength is non-critical, such as engine blocks, pump housings, valve bodies, electrical boxes and decorative castings.

In grey cast iron, a large part or all of the carbon is in the form of flakes of graphite. In three dimensions these appear as plate-like structures. In two dimensions, as polished surface will appear under a microscope, the graphite flakes appear as lines. The presence of graphite flakes gives capacity to damp vibrations caused by internal friction and, consequently, the ability to dissipate energy. Graphitic cast iron has a dark gray or almost black fracture. Upon small degree of super cooling, graphite is formed when the cast iron solidifies from its liquid state. Slow cooling promotes graphitisation. Rapid cooling partly or completely suppresses graphitisation and leads to formation of cementite. Rapidly cooled gray iron in which the carbon does not form graphite flakes, but rather combines with iron to form cementite is called white iron.

灰口铁

    生铁中的一种，又称铸造生铁。含碳量约3％，含硅约2％。断面呈深灰色，通常叫灰口铁。
　　碳在这种铁的合金里是以片状的石墨形态存在。质较软，可进行切削加工。热时容易流动，铸造性能好。较耐磨。强度及延展性差。由于石墨质软并有润滑作用，因而这种生铁具有良好的切削、耐磨和铸造性能等优点。但是，由于有片状石墨的存在，降低了它的抗拉强度，使它不能锻轧，只能用于制造各种铸件，如铸造机床床座、铁管等。
　　通常把这种生铁叫做铸造生铁（简称铸铁）。