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Application of heat treatment of nodular cast iron manhole cover

Ductile iron manhole covers should be used after heat treatment. Because of the casting defects such as pores, cracks, shrinkage holes and shrinkage porosity, coarse grains, uneven structure and residual internal stress in the as-cast steel castings, the strength, especially the plasticity and toughness of the steel castings are greatly reduced. In order to refine grains, uniform structure and eliminate internal stress, steel castings must be normalized or annealed. Normalized steel has higher mechanical properties and lower cost than annealed steel, so it is used more. However, since normalizing will cause greater internal stress than annealing, it is only suitable for steel castings with a carbon content of less than 0.35%. Because of the good plasticity of low carbon steel castings, it is not easy to crack when cooled.

The products obtained from cast iron manhole covers are fine and complex, close to the shape of the parts, and can be used directly without processing or with little processing. widely. It is not only suitable for casting of various types and alloys, but also produces castings with higher dimensional accuracy and surface quality than other casting methods, and even complex, high temperature resistant and difficult to process castings that are difficult to be cast by other casting methods. , can be cast by investment cast iron manhole cover.

A method for improving the directional solidification rate of cast iron manhole covers. The difference from the PD method is that only the heat insulation baffle is installed on the lower part of the induction heating body, and a shell bracket is added under the water-cooled chassis, so that the shell shape gradually moves down with the cooling bottom plate after the flexible injection. The selection of fine steel castings has many advantages. It can accelerate the processing speed and improve the working power to a certain extent. The heat insulation shield blocks the radiant heat of the induction body, so that the condensing area in the shell is at the high temperature of the hot area, while the condensation area of ​​the part of the condensing shell removed is in the cold area, and the warm flow is removed by the water-cooling plate through conduction, and part of the warm flow Then the heat is dissipated to the surroundings through radiation, and then the temperature gradient G value along the alloy condensation interface is increased by 2 times compared with the general PD method, and the R value is increased by nearly 4 times.

Cast iron manhole cover methods are used such as sand casting, and factories that produce in large quantities should create conditions to use advanced modeling and core-making methods. The production line of the old-fashioned shock or shock molding machine is not high enough, the workers are labor-intensive and noisy, and they are not used to the requirements of mass production, and should be gradually transformed. For small castings, boxless high-pressure molding machine production lines with horizontal or vertical splitting can be selected, and the production power of solid-type molding is high and the floor space is small; for medium parts, various boxed high-pressure molding machine production lines can be used. , Air punch molding line, in order to meet the requirements of fast and high-precision molding production line, the core making methods can be selected: cold core box, hot core box, shell core and other efficient core making methods.

Silica sol is an important fine chemical product with different important uses. For example, alkaline silica sol is used in cast iron manhole covers, exterior wall coatings and other fields. Silica sol cast iron manhole covers are used in a wide range, and are not restricted by the size, thickness and shape complexity of the castings, and the production mode is convenient. It can use a wide range of materials and can use large amounts of scrap metal and renewable resources. Compared with ordinary casting methods, it consumes less. Castings have certain dimensional accuracy, small machining allowance, saving processing time and metal materials; low cost, good comprehensive economic performance, low energy consumption, and few consumables. Silica sol cast iron manhole covers have high dimensional accuracy and surface finish, which can reduce the workload of machining. Only a small amount of machining allowance can be used for parts with high requirements. Superalloy castings can be cast, such as jet engine blades, streamlined profiles and cooling chambers that are difficult to form by machining techniques.

Silica sol cast iron manhole covers are used in the coating industry, which can make the coating firm, and can resist pollution, dust, aging, fire and other functions. It will be useful in use, so that the hydraulic metal can better fill the cavity, copy the shape of the cavity, and improve the accuracy of the casting to prevent the shortcomings of air holes and lack of pouring. Silica sol cast iron manhole covers crystallize under the pressure. It is useful to put the shell in the pressure tank for casting. After the product is finished, the pressure tank will be closed immediately, so that the casting will condense under pressure to increase the size of the casting. density. For the directional crystallization of silica sol cast iron manhole covers, when using some investment castings such as their magnetic steel and turbine blades, if their crystalline structure is columnar crystals arranged in a certain direction, use their hot gravity casting, in the process of use. , which is a form of casting that is used more often. After the shell is taken out from the roasting furnace, it is poured at high temperature.


Post time: May-16-2022