Extending the boundaries of scrap usage in wrought aluminium alloys for greater recyclability and lower energy consumption

Transcription

1 Extending the boundaries of scrap usage in wrought aluminium alloys for greater recyclability and lower energy consumption PhD. Gheorghe DOBRA; PhD. Marin PETRE; Florea STERIE - ALRO Slatina, Romania- 23rd International Recycled Aluminium Conference November

2 Summary 1. Aluminium industry overview 2. ALRO method to increase scraps recycling 3. Highlights 4. Conclusions 23rd International Recycled Aluminium Conference November

3 1. Primary Aluminium Consumption A growth rate around 5.9 % is actually a strong indicator that the aluminium market does not has a demand problem: in about 3 years (from 2013 to 2016), the demand increased by about +10 Mio mt. Next year, with a growth rate of about 5.6%, we should reach the 60 Mio mt threshold. Source: EA Metal Supply Statistics Commitee, rd International Recycled Aluminium Conference November

4 Primary Aluminium Regional Balance Importing regions Exporting regions Europe is one of the most import-dependent regions worldwide with Asia (without China). The exporters are: Middle East; CIS, China, Oceania and Africa.. China seems to compensate for supply deficit outside: China may export more primary in the future Source: EA Metal Supply Statistics Commitee, rd International Recycled Aluminium Conference November

5 Aluminium Industry Snapshot 70 Members of European Aluminium approx. 600 plants in 30+ European countries (EU 28, EFTA and Turkey) 1million + Direct and indirect jobs across Europe s value chain 40 Billion annual turnover 95% Recycling saves 95% of the energy needed for the primary production 75% of the aluminium ever produced is still in use An innovative value chain serving EU key markets 16% of worldwide aluminium is produced in Europe, half of which from recycled sources 10.5 million Tonnes recycling production in 2013 Source: European Aluminium, rd International Recycled Aluminium Conference November

6 World Primary Aluminium Balance Thousand tonnes (f) 2016(f) Production Consumption Balance/surplus Balance 2015(f) 2016(f) China R o W For 2015, it is expect a surplus of 949 kt and a surplus of 1,178 kt for The surplus in China is more or less unforeseeable. Source: EA Metal Supply Statistics Commitee, rd International Recycled Aluminium Conference November

7 EU imports dependency Each year the aluminium import increased and in the last years the production of primary aluminium decreased Source: European Aluminium statistics_2014 data 23rd International Recycled Aluminium Conference November

8 EU imports of unwrought aluminium Rest of the world (12%) EU imports of aluminium: 6.4 mio tonnes ktonnes Russia (23%) Middle East (11%) Source: Global Trade Atlas_2014 data 23rd International Recycled Aluminium Conference November

9 EU net exports of scrap In the last six years the exports of aluminium scrap quantity was minimum tonnes per each year! Source: European Aluminium statistics_2014 data 23rd International Recycled Aluminium Conference November

10 2. The ALRO method to increase scraps recycling Late 2013 Alro started operating its new investment, a scrap re-melting facility; consequently, for optimization purposes, a mathematical model has been developed in-house, aiming to prepare the scrap batches before re-melting, in order to obtain new chemical compositions and eventually use them to increase its value added products output. The main priorities in order to obtain the recycling-friendly compositions were: The minimal addition of primary aluminium and alloying elements; Keep the mechanical properties in the same range as in the standard one or customer requirements; Obtaining products without unconformities (i.e. porosity) defects that are determined by the increase of the scrap quantity/ batch. 23rd International Recycled Aluminium Conference November

11 Limitations in terms of scrap feed quantity In order to increase the scrap quantity, the following problems occure: scrap can have relatively widely varying compositions; compositions resulting from mixed wrought and cast scrap will be more difficult to use directly; to achieve acceptable impurity levels for the products; Fe and Si % are difficult to control in recycled metal; Other elements require special attention; heavy elements or Vanadium (V) for example. For aerospace alloys, impurity levels above % Fe or % Si are unacceptable. High performance automotive alloys usually restrict both Si and Fe to 0.40% max. 23rd International Recycled Aluminium Conference November

12 The benefits of recycling Recycling is essential to sustainable development. It allows resources to be saved and the amount of scrap to be reduced. More than that, there are economic benefits: Decrease of power consumption, taking into consideration that the power consumption in the aluminium scrap recycling process is about 95% less compared to the aluminium electrolysis production process; Recycling of internal aluminium scraps; Reduction of CO2 emissions because the electricity consumption greatly decreases; Savings on raw materials (bauxite, alumina ), sources that are becoming more and more scarce as the world resources availability is continuously decreasing; Using this method the cost is reduced by 10-20% depending on the quality & quantity of scrap used. 23rd International Recycled Aluminium Conference November

13 Defining the mathematical model 1. Expressing of the requested alloy properties (in this case 5754, H111 temper), as (polynomial) function of alloy composition. 2. Changing our internal standard chemical composition of wrought aluminium alloys towards the recycling-friendly limits. 3. By using the last square method and extrapolation we will formulate: - the new interval limits for the chemical composition; - the determination of the main alloying elements influence on the mechanical properties. We have used a large database for this analysis (over 2000 charges of 5754 aluminium alloys). 23rd International Recycled Aluminium Conference November

14 Results From the analyze of the products properties and chemical composition achieved in the period March 2013 September 2014: The Si and Fe content influence Generally the strength values are correlated with the distribution of phases (Mg₂Si, Al₆Mn, Al₆Fe, Al₃Fe etc.) from the base metal. The overall trend is growing of strength with increasing silicon and iron content. The lowest values for Rm ( 201MPa) were obtained for an Si content of 0.12%. 23rd International Recycled Aluminium Conference November

15 Results (2) The Mg content influence Usually the addition of Mg increases tensile strength. The highest values for Rm ( 213MPa) were obtained for an Mg content of 2.95%. For instance, for 5754 aluminium plates with thickness over 50 mm we have obtained the next regression equation: Rm = Si Fe Cu Mn Mg with a value for coefficient of determination Using this equation we can control the quality of our products. 23rd International Recycled Aluminium Conference November

16 Results (3) In order to validate the regression equation there where cast several charges which were followed up during the entire production flow. For these charges no unconformities were recorded. The average strength values obtained for these charges were close to the estimated value (about 8MPa higher). An increase of magnesium content determines a contraction porosity increase. The mathematical model is flexible if scrap is segregated by alloys series, thus an important role is represented by scrap sorting technology. 23rd International Recycled Aluminium Conference November

17 Results (4) With the advantage of primary aluminium, Alro uses more and more aluminium scrap to obtain value added products Transformation Transformation Transformation Aluminium scraps Final added value products 23rd International Recycled Aluminium Conference November

18 3. Highlights EU is net aluminium importer; EU is net aluminium scrap exporter; LME price is in free-fall due to: - strong US dollar; - the low price of oil; - higher China exports. The cost of electrolytic aluminium in UE will increase, mainly due to the electricity price; Starting with 2013, Alro is using aluminium scrap from the market and for this reason it developed a method to prepare the scrap before re-melting and in the final this is used to produce value added products; This method has been successfully used in Alro, not only for 5754 aluminium alloy plates but also for other aluminium alloys in order to obtain coils, sheets and plates. 23rd International Recycled Aluminium Conference November

19 4. Conclusions 1. Using the mathematical modelling, Alro has managed with success extending the boundaries of scrap usage in wrought aluminium alloys for greater recyclability and lower energy consumption. 2. Here we have shown how it is effectively determined the correlation between the chemical composition and mechanical properties of 5754 aluminium alloy plates. 3. This method can be applied by any producer of processed products if they use slabs as raw material for its flat rolled products. 4. Using this model we can control the quality of our products. 5. This method allowed us to optimise the primary aluminium quantity used for alloys, as well as increasing the aluminium scrap recycled ratio, closely observing the final product properties and characteristics; as a result, the unit energy consumption decreased in parallel with the CO2 emissions reduction; 6. The specific cost of the final product also decreased by 10-20% depending on the type of scrap used. 23rd International Recycled Aluminium Conference November