观察铸件在整个生命周期中的环境影响

The transport sector is responsible for approximately 23% of global energy-related CO2 emissions and is expected to increase at a faster rate than other energy end-use sectors. 为了减轻这种影响, automobile fuel economy regulations such as EPA’s Corporate Average Fuel Economy (CAFE) standards have been adopted. 同时有效提高燃油经济性, these automotive regulations are limited to only reducing the CO2 and other greenhouse gas emissions from the tailpipe. 因此, these regulations ignore the emissions due to producing the components within the automobile and the recycling or other end-of-life impacts that can lead to an unintended increase in greenhouse gas emissions over the life of a vehicle.

Life cycle analysis is a relatively new discipline that incorporates all major phases—production, use and recycling/end-of life—of a product or a process life cycle to calculate total impacts. It is quickly becoming a key tool for academics and industry analysts and has even started to be used within the regulatory environment. The European Commission calls life-cycle thinking “the best framework for assessing the potential environmental impacts of products, 流程和系统.“此外, the EU already has existing legislation directly based on life-cycle analysis, which requires the calculation of life-cycle greenhouse gas emissions of biofuels. 在美国境内.S.美国加州已经采用了低碳燃料标准. 此外, many solutions for industry to adapt to life cycle analysis already exist, 比如开源软件 
和模型.

The spread of life cycle analysis through regulatory programs indicates that similar approaches may become the preferred calculation method for limiting greenhouse gas emissions. Researchers at the Institute of 环境 Technology in Berlin have drafted many different process options to adopt it into governmental policy, 包括基于现有ISO标准的标准. 
由于它们的可回收性和较低的蕴含能量, 在这个框架下，铸件具有更可持续的潜力, 但需要更多的数据来量化其影响.

铸件和生命周期分析

An extensive literature review discovered only a limited number of casting-related life cycle analysis that included the use-phase. Rather, most of the literature focused on the energy and costs during production and recycling. This included two Life Cycle Inventory databases for cast aluminum and cast magnesium that provided production and recycling inputs, 哪些可以帮助未来的分析包含所有主要阶段.
而生产和报废的影响可以为生产商的决策提供信息, automotive suppliers evaluating new materials will be looking for the entire life-cycle story, as it is misleading to only report the production and end-of-life phases. 举个例子, 79% of total life-cycle greenhouse gas emissions of the VW Golf VII vehicle (driving 20,000公里或12,每年400英里)来自使用阶段. 即使有两种主要铸造材料的数据库, 只有三项研究涵盖了所有三个阶段——生产, 铸造部件的使用和寿命终止:

• “主要生产, Engine Production and on-the-road CO2: How can the 汽车 Industry Best Contribute to 环境 可持续性?第38届维也纳国际汽车研讨会(2017年4月).
• Jhaveri等人., “Life cycle assessment of thin-wall ductile cast iron for automotive lightweighting applications,“可持续材料和技术, 卷. 15, pp. 1–8 (2018).
• 西蒙ehrenberg, 汽车结构中镁构件的生命周期评价,国际镁协会(2013年5月).

几乎可以肯定，这个列表并不详尽, 但这表明对铸件这一主题缺乏研究. 此外, the scope of life cycle analysis work in castings is limited: 所有 three studies only compare to other casting processes and do not compare to other material processes. 

为什么铸件对环境的影响更小

尽管缺乏对铸件的生命周期分析研究, several plausible reasons explain why castings may have a lower life-cycle energy and greenhouse gas impact than other forms of processing. 

在生产阶段, castings have a lower embodied energy per kilogram than other processes using the same material (Fig. 1). This is most likely because castings are the shortest path from raw materials to a finished product. 作为警告, while embodied energy is not equivalent to greenhouse gas emissions over a product’s full life cycle, 它是生命周期排放的重要组成部分. 因此, 假设是相同的电源, a decrease in embodied energy will also have an associated decrease in greenhouse gas emissions over the full life cycle of the product. 

在使用阶段, the largest influence on fuel consumption and therefore energy and greenhouse gas emissions, 车辆重量是多少?. Since metalcasting is a near net-shape process that can minimize the amount of machining, 完成, 每个组件的零件数, 铸件为轻量化提供了极好的机会. 

例如, 正如最近的cast Source文章中所讨论的那样, 汽车减轻重量的3种方法,“将钢冲压件转换为镁铸件的结果是19.4磅. 大量节约和零件编号合并(图2). 2). 在同一篇文章的另一个例子中, converting an aluminum stamped assembly to an aluminum casting led to a 20% weight savings and part number consolidation (Fig. 3). 零件号整合可以转化为成本节约, and the mass savings will translate to a reduction of greenhouse gas emissions in the use-phase.

当废金属从不同的金属加工流中积累, 废料中的化学杂质变得更加集中. 由于材料纯度高，适用于锻压金属, fabricators cannot use a significant amount of scrap material for production. 该规范对铸造部件的要求不高. 例如, 锻铝可回收制成铸铝部件, 但情况不太可能逆转. Recent literature suggests that the baseline secondary content values for wrought aluminum are 0%, 而铸铝则是85%. Similarly, baseline secondary content for flat, long and cast steel are 5%, 85% and 100%. 因为铸件本身更容易回收, the energy and greenhouse gas emissions in the end-of-life phase also will be lower.

Castings hold great promise to be more sustainable than other processes for the same base material, 即使轻量化是不可行的. 由于铸件的生产优势和可回收性, their production may still result in a net savings in energy and greenhouse emissions while simultaneously providing a low-cost solution for automotive suppliers. 最终, 在以生命周期分析为重点的监管环境中, the casting industry could reasonably argue that their process is the most sustainable. 然而, 最大限度地提高这一论点的有效性, 需要深入的铸件生命周期分析研究.