Now with the popularity of manhole covers, however, in the market, there are more and more kinds of them, such as cast iron manhole covers, ductile iron manhole covers, composite manhole covers and concrete manhole covers. Among them, the appearance of cast iron manhole cover and ductile iron manhole cover is very similar, which can't be distinguished only from the surface. In fact, the effect expressed by different materials is different, so we need to be able to identify several important matters in the purchase.
(1) Knock well cover: the sound of ductile iron well cover is similar to that of carbon steel. The knock of the gray iron manhole cover sounds dull.
(2) From the fracture, the grains of the former are very fine and black gray. The grain size at the fracture of gray iron well cover is coarse and gray white.
(3) In terms of refining methods: nodular cast iron well cover is achieved by adding inoculant and nodularizing agent in gray iron during refining to make graphite have dispersed flocculent and turn into ball, so as to reduce the fracture of ferrite, increase strength and improve performance。
(4) The gray iron well cover is directly refined into molten iron without adding any auxiliary materials, and then cast into well cover。 The former is made by adding spheroidizing agent, rare earth magnesium and other metal alloys。
(5) The ductile iron well cover has high strength and good toughness, so it is about 30% lighter than the similar gray iron well cover.
(6) The same is ductile iron products, spheroidization rate is different, the quality is different, the price is also very different.