Ductile iron manhole covers are generally made by heat treatment process, it is composed of three steps, namely heating, insulation and cooling, at the same time as the heating temperature and cooling speed and holding time are different, so the product matrix is different. Heat treatment technology can not only adjust the overall structure of the chemical composition but also can control and improve the intensity of use of manhole cover, so as to achieve better.
The heat treatment process of nodular cast iron manhole cover is carried out by heating and cooling of the two methods, the internal organizational structure that can have rules to change the properties of cast iron, so that the material itself covers corresponding, so as to meet the need of heavy vehicle road, has a very good performance in hardness, toughness, wear resistance the strength and plasticity, etc.. The process of each heat treatment process of ductile cast iron manhole covers are heated in solid state under the covers, heating, cooling and heat preservation is made of three steps.
Cast iron production in addition to some of the more suitable chemical composition to control the internal organization, structure and heat treatment can control and improve the microstructure, which can improve the performance of cast iron. The heat treatment of nodular cast iron has the same place as the heat treatment of steel, and there are different places. In the heat treatment of nodular cast iron is the production process of steel imitation, but in terms of process parameters due to the presence of graphite, solid metal and chemical composition are different, so that the heat treatment of cast iron has a certain particularity.
No matter how the ductile cast iron is made, it must be the first choice for the processing and processing to ensure that the ductile iron has enough strength, because it is related to the safety of pedestrians and vehicles on the municipal road. So compared with other covers, the bearing capacity of ductile iron manhole cover is great.