Resource and Environmental Load Evaluation of Sand Casting Process

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Sand casting, a foundational metal-forming technique, faces increasing scrutiny due to its environmental footprint. This study evaluates resource consumption and environmental impacts of two sand casting variants: static-pressure casting and V-process casting. By integrating lifecycle assessment (LCA) with a Delphi-derived evaluation framework, critical insights into process optimization and green manufacturing strategies are presented.

Methodology

The evaluation framework comprises three primary dimensions: resource consumption, environmental load, and human health impacts, further divided into nine metrics (Table 1). Weighting factors were determined through expert surveys using the Delphi method:

$$
\alpha_i = \frac{\sum_{x=1}^{n} k_{i,x}}{\sum_{i=1}^{m} \sum_{x=1}^{n} k_{i,x}}
$$

where \( \alpha_i \) represents the weight of the \( i \)-th indicator, and \( k_{i,x} \) denotes the score assigned by the \( x \)-th expert.

Table 1: Evaluation Metrics and Weights
Dimension Indicator Weight
Resource Consumption Water Use (WU) 0.012
Abiotic Depletion (ADP) 0.010
Primary Energy Demand (PED) 0.052
Environmental Load Climate Change (GWP) 0.160
Acidification (AP) 0.190
Eutrophication (EP) 0.152
Photochemical Oxidation (POCP) 0.170
Human Health Human Toxicity (HTP) 0.028
Respiratory Inorganics (RI) 0.228

Process Analysis

Key processes in sand casting include:

  1. Melting: Energy-intensive phase using cupolas/electric furnaces
  2. Molding: Sand preparation and shape formation
  3. Pouring: Molten metal transfer into molds
  4. Cleaning: Post-casting surface treatment
Table 2: Process Inputs/Outputs Comparison (per ton casting)
Parameter Static-Pressure V-Process
Pig Iron (kg) 465.84 903.73
Steel Scrap (kg) 528.36 89.35
Electricity (kWh) 1,139.4 640.06
PM2.5 Emissions (kg) 10.40 9.10
VOC Emissions (g) 92.26 65.21

Lifecycle Impact Assessment

The composite impact index \( CI_j \) for process \( j \) is calculated as:

$$
CI_j = \sum_{i=1}^{n} SER_{i,j} \times \alpha_{i,j}
$$

where \( SER_{i,j} \) represents normalized indicator values. Key findings:

Table 3: Impact Distribution by Process Stage
Process Static-Pressure V-Process
Melting 67.7% 69.3%
Molding 13.5% 12.1%
Cleaning 16.0% 12.4%
Pouring 2.8% 6.2%

Critical Findings

  1. Melting contributes >65% of total impacts due to high energy/resource inputs
  2. V-process demonstrates 23% lower composite impact than static-pressure casting
  3. Health impacts from PM2.5 and VOC emissions remain significant in cleaning stages

Optimization Strategies

  • Adopt vacuum-assisted molding to reduce binder consumption
  • Implement real-time emission monitoring during melting
  • Optimize charge materials ratio using LCA-based simulations

This systematic evaluation provides quantitative benchmarks for advancing sustainable sand casting practices while maintaining production efficiency. Future work should integrate real-time process monitoring with the developed evaluation framework.

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