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Application of heat treatment of nodular cast iron manhole cover

After heat treatment, ductile iron fence caps should be used. Due to casting defects such as pores, cracks, holes and spiral porosity, coarse grains, uneven structure and residual stresses in the cast steel casting, strength, in particular plasticity and toughness, of cast steel parts is greatly reduced. Steel castings should be normalized or annealed to refine the grains, create a uniform structure, and eliminate residual stresses. Standard steel has better mechanical properties and is less expensive than annealed steel, making it more commonly used. However, because normalization causes more internal stresses than annealing, it is only suitable for steel castings with less than 0.35% carbon content. Due to the good plasticity of low carbon steel castings, it is not easy to break when cooled.

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The products obtained from the cast iron lid covers are fine and complex, close to the shape of the pieces, and can be used directly without machining or with little machining. Not only is it suitable for casting of various types and alloys, but it also produces castings with higher dimensional accuracy and surface quality than other casting methods, and even complex, high-temperature-resistant castings. and difficult to machine that are difficult to strain with others. casting methods. , can be poured through the caps of the investment casting mouth.

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A method to improve the directional solidification rate of cast iron fence caps. The difference with the PD method is that only the thermal insulation sheet is installed at the bottom of the induction heater and a carcass support is added under the water-cooled chassis, so that the carcass shape gradually moves down with the bottom cooling plate after flexible injection. Choosing fine steel castings has many advantages: it can speed up processing speed and improve work efficiency to some extent. The thermal insulation shield blocks the radiant heat of the induction body, so that the condensation area of ​​the housing is at the high temperature of the hot zone, while the condensation area of ​​the part remote of the condensing housing is in the cold zone. , and the hot flow is removed through the water cooling plate by conduction, and part of the hot current is emitted into the environment by radiation, and then the value of the temperature gradient G along the Alloy condensation interface increases twice compared to the general PD method, and the R value increases almost four times.

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Cast iron fence cover methods are used, such as sand casting, and factories that produce in large quantities should create conditions to apply advanced methods of modeling and core manufacturing. The production line of the old blow molding machine is not high enough, the workers are industrious and noisy and are not accustomed to the demands of mass production and have to convert gradually. For small castings, production lines of boxless high-pressure molding machines with horizontal or vertical division can be selected, and the production of solid casting is high and the footprint is small; for medium-sized parts, several production lines of box-shaped high-pressure molding machines can be used. , Air punch molding line, to meet the needs of the fast and high-precision mold production line, the core manufacturing methods can be selected: cold core box, hot core box, core shell and other efficient core manufacturing methods.

Silica flooring is an important fine chemical product with several important uses, for example, alkaline silica flooring is used in cast iron fence tops, exterior wall coverings and other fields. Silica cast iron closure caps are only used in a wide range and are not limited by the size, thickness and complexity of the shape of the castings, and the shape of production is convenient.

It can use a wide range of materials and use large amounts of scrap and renewable resources. Compared to conventional casting methods, it consumes less. Castings have a certain dimensional accuracy, a small machining margin, saves machining time and metal materials, low cost, good overall economic performance, low energy consumption and few consumables.

Post time: Jul-05-2022