Life Cycle Inventory of Aluminium Hoods and Bumper Reinforcements for Automobiles

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1 Life Cycle Inventory of Aluminium s and Reinforcements for Automobiles Masanori Yamaguchi,Toshio OnoyeHiroshi Yagita, Atsushi Inaba, Makoto Ootani*, Masao Okubo**, Tomoya Ohzono***, Kenzo Ayata**** National Institute of Advanced Industrial Science and Technology Sumitomo Light Metal Industries, Ltd. **Japan Aluminium Association *** Japan Research Center for Metals ****Shinko Research Co.,Ltd. Keywords: Automobile, CO 2, LCI,,, Aluminium, Steel ABSTRACT Reduction of CO 2 emission from the transport sector, especially from automobiles, is an important theme for overall reduction of CO 2 emission in Japan. As the weight reduction of automobiles is an effective way to reduce CO 2 emission, utilization of aluminium is being examined for this purpose. As part of the investigation of LCI data, which are needed for a quantitative estimation of aluminium's effect on CO 2 emission reduction at each stage of automobile's life cycle, LCI data for hoods and bumper s of steel and aluminium were calculated by using sum-up method. 1. TION Reduction of CO 2 emission from the transport sector, especially from automobiles, is an important subject for total CO 2 reduction in Japan. Weight reduction of an automobile is an effective way for the reduction of CO 2 emission and aluminium utilization is now being examined for this purpose. Thus, in order to obtain CO 2 emission reduction, inventory data for the processing/assembling of hoods and bumper s, in which aluminium is currently used in some automobiles for the weight reduction were calculated by using summing up method on various kinds of data. Inventory analysis of hood and bumper production was confirmed by the LCA sectional committee of JAMA. 2. INVENTORY ANALYSIS 2.1 Inventory analysis of hood production Function and functional unit LCI analysis was carried out for the process of processing and assembling aluminium hood and conventional steel hoods. Transportation within the facility was not taken into account. The functional unit is a hood of compact passenger car. The shapes and dimensions of the hood outer and inner panels (aluminium and steel), shown in Fig.1, were assumed based on pictures shown in a literature[1]. The weight of hood outer and hood inner, shown in Table 1, was calculated on the assumption that the thickness of hood panels (both outer and inner) of aluminium is 1 mm [1] while the thickness of hood panels (both outer and inner) of steel is 0.75 mm [1] in the models shown in Fig.1. The weight saving ratio amounts to 52%. While the total weight of steel hood (outer and inner) is kg for this model, the weight of steel hood reported for Fairlady Z and Skyline are 14.9 kg and 16.8 kg, respectively [2]. Thus, the figure shown in Table 1 is relatively low, corresponding to relatively small vehicles. Table 1 Weight of hood outer and hood inner of aluminium and steel (kg) outer inner Joint parts Paint Total Aluminium Steel Weight saving ratio(%) 52

2 1,250 1, ,400 outer 1,350 inner or steel coil Fig.1 Model of hood outer and hood inner of aluminium and steel Outer Share Share Press Spot Assemble welding Press Baking finish Inner Fig.2 Process flow and system boundary of hood production System boundary As shown in Fig. 2, the system boundary (scope of data collection) for both aluminium hood and steel hood covers from the carrying in of the aluminium coil or steel coil to the completion of hood. The processes for producing hood include cutting of aluminium or steel sheets coil (for both outer and inner panels), pressing, spotwelding, attaching the joint parts for fitting into the body and baking finish of the surface Calculation of the inventory The inventory of the production of hood was calculated based on the processes shown in Fig. 2 and the data in the literatures/sources[3],[4],[5]. The consumption of electricity was converted to energy consumption at the rate of 2,250 kcal/kwh. Fig. 3 shows the calculated inventory of processing and assembling of an aluminium hood and a steel hood based on the assumptions kg Steel sheet Coil kg 1.737kWh Fuel MJ Parts 0.300kg Paint 0.418kg Processing and assembly 1.748kWh Fuel MJ Parts 0.300kg Paint 0.418kg Processing and assembly scrap kg Steel scrap kg hood hood 5.975kg Steel hood Steel hood kg Fig.3 Inventry of processing and assembly of aluminum and steel hood

3 2.1.4 LCI of hood The LCI of the material was calculated from the data on 6000 series aluminium [7]and cold-rolled steel [8]. As regards the coating materials, the use of a mixture of xylene (50%) and polyurethane (50%) was assumed and the background data [9] was used for calculation. The inventory of joint parts was ignored because its effect seems to be negligible. For the LCI of electricity and fuel, the data from the database [9] was used. Based on the breakdown of the fuel sources obtained from the material-process (MP) inventories provided by JAMA [3], the LCI of the each component of fuel sources was calculated. The leftmost bar in the chart of Fig. 4 shows the LCCO 2 obtained from the calculation. For the calculation, it is assumed that the aluminium sheet is composed of virgin (primary) aluminium. from processing is deducted at the rate of 95%, considering the market price of aluminium scrap. For the purpose of reference, other bars on the left of pairs of bars in the chart show the LCCO 2 for the aluminium sheet with a scrap content of 2.8 %, which is the same level as the steel scrap content of cold-rolled steel sheets, 50% and 100%. The bar on the right of each pair of bars shows the LCCO 2 for the aluminium sheet with a scrap content of 0 %, 2.8 %, 50% and 100% when both the scrap from processing and the scrap from discarded hood are treated as equivalent of primary aluminium and deducted at the rate of 95%, considering the market price of scrap aluminium. Although the energy consumption during the discard and recovery processes of hood is not considered, it seems to be negligible if hood is to be discarded manually. 2.2 Inventory analysis of bumper production Function and functional unit LCI analysis was carried out for the processing and assembling of aluminium bumper. The conventional processing and assembling of steel bumper was taken for comparison. Transportation within the facility was not taken into account. The functional unit is a bumper of compact passenger car. As the shape and dimension of bumper s varies with the type of automobile to which it is attached, the aluminium and the steel bumper, shown in Fig. 5, were assumed as models System boundary As shown in Fig. 6, the system boundary for aluminium bumper is from the extruded aluminium alloy shape to the completion of bumper. For steel bumper, the system boundary is from the high tensile strength steel coil to the completion of bumper as shown in Fig Calculation of the inventory The inventory of the production of aluminium bumper and steel bumper was calculated based on the processes shown in Fig. 6 and 7 and the data in the literatures [3],[4],[5]. Fig. 8 shows the inventory of processing and assembling of an aluminium and a steel bumper based on the assumptions above LCI of bumper The LCI of the material was calculated from the data on 6000 series extruded aluminium alloy shape [5] and cold-rolled steel [6]. The LCI of bumper using aluminium with a scrap content of 14%, which actually corresponds to the average for extruded aluminium alloy shape, was also calculated. For the LCI of electricity and fuel, same data base and inventories were applied as in the case of hood. LCCO2(kg) Assumption A: from processing and assembly is deducted. Assumption B: from discarded hood is deducted (0%) (2.8%) hood (50%) Deduction assumption A Deduction assumption A+B (100%) Steel hood :scrap(2.8%) Fig.4 LCCO 2 of processing and assembly of aluminium and steel hood 3mm thick mm thick ,300 1, kg=2.66 before processing 3.120kg=2.66after processing Steel 3.965kg=7.86before processing 3.961kg=7.86after processing Fig.5 Model of bamper of aluminium and steel

4 Extruded aluminum alloy shape (6000 grade) Cutting Bending,drilling Heat treatment Fig.6 Process flow and system boundary of aluminium bumper High tensile strength steel (60K grade) Share Punching Roll forming Seam welding Electrodeposition coating* * is occasionally coated with car body. Fig.7 The leftmost bar in the chart of Fig.9 shows the LCCO 2 obtained from the calculation in which scrap from processing is deducted at the rate of 95%, considering the market price of scrap aluminium. Other bars on the left of pairs of bars in the chart show the LCI for the aluminium sheet with a scrap content of 14%, which is the actual scrap content, 50% and 100%. The figure decreases by 10% when aluminium with a scrap content of 14%, and further decreases to a half when the scrap content is 50%. The bar on the right of each pair of bars shows the LCCO 2 when both the scrap from processing and the scrap from discarded bumper are treated as equivalent of pure aluminium and deducted at the rate of 95%, considering the market price of scrap aluminium. If both the scrap from processing and from discarded bumper are deducted, LCCO 2 is smaller than that of steel bumper regardless of the scrap content. Extruded aluminum alloy shape (6000 grade) 3.135kg High tensile strength steel (60k grade) 3.971kg 0.482kWh Fuel 0.349MJ 2.591kWh Fuel MJ Processing, Assembly, Heat treatment Processing, Assembly Fig.8 Inventry of processing,assembly and heat treatment of aluminum and steel bumper reinforecement Process flow and system boundary of steel bumper 15g 10g 3.120kg Steel 3.961kg LCCO2(kg) Assumption A: from processing and assembly is deducted. Assumption B: from discarded bumper is deducted (0%) (14%) bumper (50%) Deduction assumption A Deduction assumption A+B (100%) Steel bumper :scrap(2.8%) Fig.9 LCCO 2 of processing, assembly and heat treatment of aluminum and steel bumper REFERENCES [1] "Press Technique" Vol. 36, No. 1 (1998), p.34 [2] Masahiko Jinda"Press Technique" Vol 32, No , p.19 [3]"Material-Process inventories on automobiles manufactured in 1997,2002 Edition, JAMA [4]Report on "Assessment Technologies for LCA of Environmental Impacts" (2002 Edition), NEDO [5] Database of Pré Consultants's SimaPro ver. 5 [6] "Technologies of Materials for Automobiles"(1996), edited by JSAE, p. 45 [7] "Report on the LCI data of the Aluminium Materials for Automobiles" , JRCM [8] JLCA-LCA database 2004Fy 2nd edition [9] Database supplied with JEMAI-LCA by JEMAI

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