Energy conservation and environmental protection are critical social and economic development issues of global concern. The determination of casting process plans must comprehensively consider the relationship between resource use and environmental impact. It is essential to stay informed about the development and application of new technologies, processes, equipment, and materials. Process methods that conserve energy, reduce consumption, maximize resource utilization, and minimize waste emissions should be adopted. Low-energy-consumption and environmentally friendly process plans should be prioritized, shifting the environmental focus from remediation to prevention and striving for clean production.
Reducing waste emissions, minimizing environmental pollution, implementing harmless waste treatment, and transforming waste into valuable resources are essential requirements for modern casting production in line with societal development. Determining a casting process plan must holistically consider casting cost, energy savings, and environmental protection. Starting from improvements in the castability of part structures, selection of molding and core-making methods, determination of the casting process plan, and design of the gating system and risers, as well as casting cleaning methods, reasonable and advanced casting processes, equipment, materials, and technologies should be adopted. This approach aims to minimize pollution, protect the environment, reduce costs, and ensure reliable and stable casting quality while achieving positive social and economic benefits. For example, using insulating risers for steel castings can increase the casting yield by 10%–20%, reduce energy consumption and furnace charge losses, decrease pollution from melting processes, and lower overall production costs.
Sand casting is the primary method for producing castings, accounting for 80%–90% of total casting output. Solid waste and dust pollution from molding materials pose significant environmental challenges. Effectively addressing the recycling and reuse of used sand is a crucial measure to reduce environmental pollution. Environmentally friendly inorganic binders or low-binder casting processes should be adopted whenever possible. For instance, the vacuum-sealed molding process with dry sand for lost foam casting not only improves casting conditions but also significantly reduces solid waste emissions and mitigates environmental pollution caused by discarded sand disposal. Furthermore, casting process design should emphasize energy conservation. For example, green sand casting consumes less fuel than dry sand casting, and replacing conventional dry sand molds with self-hardening sand molds or adopting cold-box core-making methods can save fuel or reduce electricity consumption.
To protect the environment and ensure worker health, casting process design should avoid, as much as possible, methods that involve toxic substances or generate high levels of dust. On one hand, non-polluting or low-pollution processes, as well as non-toxic or low-toxic methods, should be implemented-replacing polluting with non-polluting, high-pollution with low-pollution, toxic with non-toxic, and highly toxic with less toxic alternatives. Examples include using N₂ or Ar gas refining instead of hexachloroethane for aluminum alloy melting, adopting non-toxic gas-hardened resin sand, non-toxic refining modifiers, and water-based coatings. On the other hand, production processes should be enclosed and automated, operating procedures strictly followed, and protective equipment provided. For existing pollution in casting production, appropriate countermeasures must be implemented to ensure safety and environmental protection. For instance, strict control over triethylamine gas in cold-box core-making processes is necessary, requiring effective absorption, purification, and compliance with emission standards before release into the atmosphere. Smoke and high-dust air generated during processes such as nodularizing treatment, pouring, shakeout, and cleaning should also be purified before emission.
Clear requirements are imposed on the construction conditions, layout of process equipment, enterprise scale (production capacity/output value), product quality, energy consumption, environmental protection, occupational health and safety, labor protection, personnel qualifications, and supervision and management of casting enterprises, mainly reflected in the following two aspects:
(1) Energy Conservation and Emission Reduction
Enterprises should establish an energy management system in accordance with GB/T 15587-2008 to reduce energy consumption during melting, decrease pollutant emissions and waste sand volume, and improve casting yield, waste heat recovery, and wastewater reuse rates. Enterprises employing sand casting processes should be equipped with used sand treatment equipment to enhance the proportion of sand regeneration. The reuse rates for various types of used sand should meet the following standards: sodium silicate sand (regenerated) ≥ 60%, resin self-hardening sand (regenerated) > 90%, resin self-hardening sand (regenerated) > 70%, and clay sand ≥ 95%.
(2) Environmental Protection
Effective flue gas emission and purification systems should be installed for various melting furnaces (such as cupola and electric arc furnaces) and pretreatment stations. Induction furnaces should be equipped with effective flue gas emission devices. Sand mixing, shakeout, and cleaning equipment should be fitted with efficient ventilation and dust removal facilities. Charge materials must undergo proper purification before being fed into furnaces. Key process stations generating exhaust gases (such as benzene series, acid mist, and triethylamine) should be equipped with suitable and efficient exhaust and purification facilities. Regular monitoring of pollutant emission levels is required, and exhaust gas emissions must comply with national and local pollutant emission standards.
