Smelting method for medium-thin wall cast-state nickel-free low-temperature ductile cast iron

Abstract

The invention relates to a smelting method for medium-thin wall cast-state nickel-free low-temperature ductile cast iron. The medium-thin wall cast-state nickel-free low-temperature ductile cast iron comprises the following chemical components in percentage by mass: 3.5-4.1 percent of C, 1.7-2.2 percent of Si, 0.10-0.25 percent of Mn, not more than 0.035 percent of P, not more than 0.020 percent of S, 0.015-0.030 percent of Re, 0.025-0.045 percent of Mg, 0-0.20percent of Cu, less than 0.1 percent of residual element, and Fe in balancing amount. The medium-thin wall cast-state nickel-free low-temperature ductile cast iron is obtained by mixing furnace materials and carrying out high-temperature smelting in an intermediate-frequency furnace, modularization and inoculation treatment and casting and heat-insulating treatment on the mixed furnace materials. Cast iron products obtained by adopting the smelting method disclosed by the invention obtain normal-temperature mechanical property and low-temperature mechanical property under the cast state conditions; complex medium-thin wall parts are required to be subjected to low-temperature stress relief annealing; and simple medium-thin wall parts are free from being annealed, so that the production cost is greatly reduced, the production period is greatly shortened and the production efficiency is increased.

Description

technical field [0001] The invention relates to a nickel-free low-temperature ductile iron smelting method with medium and thin walls, and belongs to the technical field of ductile iron smelting. Background technique [0002] At present, low-temperature ductile iron castings are mainly divided into thick and large castings with a wall thickness ≥ 60mm, and medium and thin-walled castings with a wall thickness of 20-60mm. Thick and large as-cast low-temperature ductile iron castings have been widely used in large-scale wind power products. Nickel-free as-cast low-temperature cast iron products are produced. However, medium and thin-walled low-temperature ductile iron products, especially thin-walled castings, are difficult to meet the requirements of normal temperature performance, low-temperature performance and metallographic properties in the as-cast condition, so most of them need high-temperature graphitization annealing to meet the delivery requirements. The production...

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Problems solved by technology

However, medium and thin-walled low-temperature ductile iron products, especially thin-walled castings, are difficult to meet the requirements of normal temperature performance, low-temperature performance and metallographic properties in the as-cast condition, so most of them need high-temperature graphitization annealing to meet the delivery requirements. It reduces the production efficiency and increases the production cost, and for the medium and thin-walled parts with complex structure, it is easy to deform during the annealing process and cause scrap

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