Research status of sustainable development of foundry industry

Casting is the basis of equipment manufacturing industry, which undertakes the forming of most metal parts. As a relatively early metal hot working process, it plays an irreplaceable role. The molten metal is poured into the formed mold cavity, and the metal blank with certain shape and performance is obtained after cooling and solidification. With the proposal of advanced manufacturing concepts such as “made in China 2025” and “intelligent manufacturing”, the foundry industry also needs to change the current development mode of high investment, high consumption and high emission, and gradually realize the transformation to green and sustainable production. The construction of green casting mode, on the basis of ensuring casting cost and quality, and reducing pollution emissions as much as possible, is a key technology to deal with the problems of low technical level, talent gap, shortage of resources, serious pollution and so on.

While pursuing casting output and economic benefits, foundry enterprises often ignore the ecological sustainability of casting production process. The energy conservation and emission reduction measures implemented by enterprises are often carried out under the mandatory constraints of industrial environmental protection departments, such as energy-saving smelting technology, pollution control devices and the emission standard of air pollutants for industrial furnaces and kilns. However, this can not fundamentally solve the generation of pollutants in the casting process. Air pollutants concentrated in melting, sand preparation, molding stage and pouring area, including gaseous polycyclic aromatic hydrogen, silica dust and formaldehyde, will increase the cancer risk of foundry workers under long-term occupational exposure. Solid pollutants, such as casting sludge produced when limestone or cement is used as adhesive and casting fine sand, calcium magnesium lignosulfonate and activated carbon are used as additives, the heavy metals and organic pollutants contained in its leachate have certain ecotoxicity. According to statistics, China’s industrial sector accounts for more than 70% of the total carbon dioxide emissions, and ferrous metal smelting and processing account for about 35.9% of the carbon dioxide emissions of all industrial categories. As the most relevant industry, the casting industry will also aggravate the process of greenhouse effect due to the carbon emissions generated under the huge casting output. Therefore, the lack of sustainability of the traditional foundry industry is obvious.

In view of the sustainable development of the casting industry, relevant scholars have studied the energy conservation and emission reduction in the casting process from the perspective of process design, including optimizing process parameters and mold structure. For example, a green sand casting process parameter optimization technology for cast iron differential housing cover based on Taguchi parameter design method can minimize casting defects and improve casting yield, which can effectively reduce energy consumption caused by secondary processing. The low carbon process design method of sand casting based on process design parameters can effectively reduce carbon emission by 8.47%. In the aspect of mold structure optimization, the optimization design of gating system is studied to indirectly improve energy efficiency by reducing casting scrap rate. For example, using auto cast X1 technology to optimize the design of the casting gating system of wear-resistant plate can reduce the casting defects related to the gating system and reduce the scrap rate by about 30%. For the new gating system of four cavity mold solid model, through repeated iterative mold filling and solidification analysis of casting simulation software, the shrinkage porosity can be reduced by about 15% and the yield can be improved by about 5%. In addition, the mold layout design based on temperature distribution and solidification time can be targeted for the problems of long solidification time, poor mechanical properties and shrinkage porosity of the mold with dense cavities or small number of cavities. The realization of the minimum cavity distance can effectively use casting materials and energy, and achieve the purpose of optimizing casting output. On the one hand, the optimization of casting materials can also fundamentally reduce the generation of casting pollutants. The high-strength and water-soluble magnesium sulfate bonded sand core material is not only suitable for hollow composite structure castings, but also can avoid the generation of toxic gas and the recycling of magnesium sulfate adhesive in the casting process. The development and application of hot air hardening inorganic binder and CO2 hardening inorganic binder can also reduce the emission of harmful gases in casting production.