Tell Me about Foundry Sand

Posted on Apr 29, 2021

Foundry Sand

EPA estimates that about 2.6 million tons of waste foundry sand can be effectively used outside the foundry every year, of which iron, steel, and aluminum sand account for 96% of the waste foundry sand. Currently, only about 14% of these sands are advantageously used for soil-related applications.

The metal foundry industry produces waste foundry sand. The foundry purchases new raw sand to make the mold, and the sand is reused many times in the foundry. This reuse ultimately makes sand unsuitable for use in molds, and part of the sand is continuously removed and replaced with original sand. Used foundry sand can be recycled or landfilled in non-casting applications. In 2007, the American Foundry Association estimated that less than 30% of the 10 million tons of waste sand produced each year were recycled. Many believe that more waste foundry sand can be reused safely and economically.
 

Beneficial Uses of Waste Foundry Sand

EPA's risk assessment of the beneficial uses of waste foundry sand found that silica-based Waste foundry sand produced by iron, steel, and aluminum foundries can be safely reused to save energy, reduce the need for mining raw materials and reduce costs for producers and end-users. EPA supports the use of these casting types of silicon-based waste foundry sand in the following applications: as an ingredient in artificial soil; as a component of soilless medium (potting soil); and as the foundation layer of the road (foundation).

EPA estimates that about 2.6 million tons of waste foundry sand can be effectively used outside the foundry every year, of which iron, steel, and aluminum sand account for 96% of the waste foundry sand. Currently, only about 14% of these sands are advantageously used for soil-related applications. EPA believes that for the applications studied in the 2014 risk assessment, there is potential for potential beneficial market growth and increased environmental benefits.

Foundries and foundries' waste sand recyclers should consult state regulatory agencies to ensure that the planned use is consistent with the state's beneficial use and waste management plan and that the chemical and physical properties of the sand comply with applicable state environmental restrictions, engineering performance Standards, and other state requirements.
 

:: Read More: Casting Sand for Industrial Use

Regulations on the Beneficial Use of Waste Foundry Sand

The Resource Conservation and Recycling Act (RCRA) encourages the adoption of environmentally sound material management practices to maximize the use of recyclable materials and promote resource recovery. EPA strives to encourage behavior change through normative and non-normative methods to improve materials management. The main role of EPA in non-hazardous solid waste management (including evaluation of beneficial uses) is to provide national leadership and technical assistance. According to RCRA, non-hazardous solid waste including non-hazardous industrial materials is predominately regulated by state and local governments. Many states have beneficial use programs EXIT and should be consulted to determine whether beneficial uses of spent foundry sands are allowed within a specific state.
 

Risk Assessment of Beneficial Uses of Foundry Waste Sand in Soil-related Applications

The EPA has launched a cooperative effort to assess the potential risks of using waste silicon-based foundry sand produced by iron, steel, and aluminum foundries and encourage beneficial use. Based on the results of the risk assessment, the EPA supports the beneficial use of these materials because the concentration of components found in waste silicon-based foundry sand from steel and aluminum foundries is lower than the Agency's health and environmental benchmarks. The risk assessment shows that in the evaluated soil-related applications, the beneficial use of waste foundry sand can protect human health and the environment, and generate environmental benefits, thereby supporting EPA's continuous efforts to promote sustainable material management.

In the risk assessment, only silicon-based waste foundry sand from iron, steel, and aluminum foundries is evaluated. In contrast, foundry waste sand from brass and bronze-lead foundries is often classified as RCRA hazardous waste. The waste foundry sand from the lead-free brass foundry and the waste foundry sand containing olivine sand were also not subject to risk assessment. In addition to used foundry sand, foundries also generate many other wastes (for example, unused and broken cores, core chamber sweeps, cupola slag, scrubber sludge, dust from dust, shot blasting fines ). However, this assessment is only applicable to the waste foundry sand defined in the assessment: the molding sand and core sand that have undergone metal casting processes can no longer be used to make molds and cores. If another foundry waste is mixed with waste foundry sand, the conclusion of the assessment may not be applicable.

Foundry sand is mainly composed of clean, uniform size high-quality silica sand or lake sand, which is bonded into molds for iron (iron and steel) and non-ferrous (copper, aluminum, brass) metal castings. Although these sands are clean before use, they may contain ferrous metals (steel) after casting, accounting for about 95% of foundry sand used for foundry. The automotive industry and its parts suppliers are the main producers of foundry sand. The most commonly used casting process in the foundry industry is the sand casting system. Almost all sand molds used for ferrous metal castings are green sand molds. Greensand consists of high-quality silica sand, about 10% bentonite (as a binder), 2% to 5% water, and about 5% sea coal (a carbon mold additive used to improve the finish of castings). The type of cast metal determines which additives and sand content used. The green sand used in the process constitutes upwards of 90 percent of the molding materials used.

In addition to green sand molds, chemically bonded sand mold casting systems are also used. These systems involve the use of one or more organic binders (usually proprietary) in combination with catalysts and different hardening/curing procedures. Foundry sand accounts for about 97% of the mixture. Chemical bonding systems are most commonly used for "cores" (used to produce cavities that cannot be produced by normal molding operations) and molds for nonferrous castings. It is believed that the United States produces 9 to 13.6 million tons (10 to 15 million tons) of foundry waste (including dust and waste foundry sand) each year. (2) Generally, about 1 ton of foundry sand is required. Every ton of steel castings produced.

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