Aluminum Scrap Research Articles

Sustainable fluoride removal with scrap aluminum: Co-producing cryolite and hydrogen

This study presents a novel continuous process for fluoride removal and re- source recovery as cryolite, using a scrap aluminum-packed column. Efficient aluminum dissolution in hydrofluoric acid (HF) generates hydrogen gas and provides cost-saving alkalinity. The process achieves high efficiency (Al/F molar ratio of 2/6) within short Empty Bed Contact Times (15 min) and at low HF concentrations (500 mg/L). Solution pH plays a crucial role, with Al/F ratios above 1 achievable at pH below 4. The exothermic reaction requires temperature control, with a strong correlation (R²=0.99) between HF concentration and heat generation. Hydrogen production matches theoretical predictions. Cryolite synthesis was confirmed at optimized pH (5–5.5) with a 1:1 bypass ratio, achieving 98 % fluoride removal. XRD and SEM- EDS analyses verified cryolite formation. This approach offers a promising solution for industrial fluoride management, resource recovery, and clean hydrogen production.

Re-manufacturing of Pre-deformed Automotive Sheet Metal Stamping Scrap Without Melting

Abstract The recycling of aluminium sheet metal typically involves shredding and re-melting, processes which are both energy-intensive and challenged by the presence of metallic contaminants. To mitigate these issues, this study explores an alternative approach: the re-manufacturing of deep-drawn parts directly from scrap aluminium sheets, thus bypassing the melting step. We used 2 mm thick Al-Mg sheet metal in H111 temper to produce simulated stamping scrap (miniaturized bonnets). Blanks were cut from these bonnets and secondary parts in a cross-cup geometry were deep-drawn using two different forming processes: warm-forming at 200 °C and O-temper forming at room temperature. The resulting maximum draw depths were 20-22 mm for warm-forming and 25-30 mm for O-temper forming. While warm-forming resulted in lower draw depths, O-temper forming led to coarse recrystallized grain formation in some regions. Our approach could significantly reduce the energy consumption associated with aluminium recycling.

Modeling Aluminum Stocks and Flows in China until 2050 Using a Bottom-Up Approach: Business-As-Usual Scenario Analysis

Aluminum metal is used in a wide range of applications such as construction, transportation, power, and aerospace. Previous studies have mainly used a top-down approach to explore future aluminum stocks and flows in China. In this study, we developed a dynamic material flow analysis model using a bottom-up approach to simulate aluminum flows and stocks in China until 2050, based on current government and sector policies. The results show that China’s aluminum stocks will be nearly saturated by 2050, with a total and per capita of 591 million tons (Mt) and 449 kg/per, respectively. The domestic demand for aluminum will grow until 2030 and will remain relatively stable thereafter at around 28–30 Mt. Construction and transport are the two sectors with the highest demand for aluminum, accounting for over 60% of the total aluminum demand. The domestic aluminum scrap will increase almost sevenfold, from 2.7 Mt to 20.0 Mt between 2020 and 2050. However, even assuming a 90% recycling rate, secondary aluminum will at best meet around 70% of demand by 2050. To realize sustainable development in China’s aluminum industry, extending the life of aluminum products and increasing aluminum scrap recycling are sensible measures.

Benchmarking wire-fed and autogenous laser beam welding to study the effect of Cu additions on weld integrity of 6060-T6 aluminium extrusion

In the automotive industry 6xxx aluminium alloys are preferred materials, yet their fabrication contributes to a considerable carbon footprint. A promising strategy to mitigate the environmental impact is the increased utilisation of recycled (secondary) aluminium, sourced from diverse scrap streams. However, as aluminium scraps come from different sources, the intrinsic variability of chemical composition, stemming from uncontrollable levels, poses a challenge, impacting material properties and weldability. Balancing manufacturability while enhancing the adoption of recycled alloys becomes a critical effort. This study aims at benchmarking wire-fed and autogenous laser beam welding to study the effect of Cu inclusions on weld integrity of 6060-T6 extrusion. The paper contributes to show the impact of Cu addition during laser welding of 6060-T6 aluminium alloys. Findings highlighted that the modification of chemical composition using filler wires is currently the most efficient approach to improve joint strength, although the Cu additions tend to reduce the weld strength.

Modelling and optimization of an innovative facility for automated sorting of aluminium scraps

The growing demand for aluminium worldwide makes aluminium recycling critical to realising a circular economy and increasing the sustainability of our world. One effective way to improve the impact of aluminium recycling is to develop cost-efficient automated sorting technologies for obtaining pre-defined high-quality aluminium scrap products, thus reducing undesirable downcycling and increasing environmental/economic benefits. In this work, an innovative facility, which includes singulation, sensor scanning, and ejection, is optimised for the automated sorting of aluminium scraps. The sorting facility is computationally studied by a virtual experiment model based on the discrete element method. The model considers particle-scale dynamics of complex-shaped scraps and mimics the automated operation of the facility. Based on virtual experiment modelling, the flow of scrap is optimized by computation, with the feasible operation of the sorting facility being proposed. Accordingly, the sorting facility has been built and model predictions are confirmed in actual operation.

Sustainable recycling of aluminum scraps to recycled aerospace-grade 7075 aluminum alloy sheets

The production of aerospace-grade aluminum alloy sheet is characterized by stringent demands, resulting in a low yield rate. The processing of this material generates considerable amounts of highly alloyed scrap, complicating its recycling due to the challenge of maintaining melt cleanliness. This study employed an aerospace-grade melt refining system to purify the recycled 7075 alloy melt obtained from comprehensive scrap remelting. The melt's cleanliness was assessed using Porous Disc Filtration Analysis (PoDFA) and Liquid Metal Cleanliness Analyzer (LiMCA) and Alscan. The microstructure of the ingots and sheets was examined through Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), whereas the mechanical properties of recycled sheets were evaluated and benchmarked against those of primary sheet at an aerospace-certified testing facility. The findings indicate that the recycled 7075 sheet meets aviation standards, with no significant differences in microstructure or performance when compared to primary sheet. Furthermore, the study highlights the economic benefits of recycling scrap, revealing a potential cost saving of $4210.8 per ton of recycled sheet. The findings presented herein offer a theoretical framework and empirical evidence supporting the development of a recycling system for aerospace scraps and the certification of airworthiness for recycled aerospace aluminum alloy.

EFFECT OF PURE ALUMINUM ON THE MECHANICAL PROPERTIES AND STRUCTURE OF THICK ALUMINUM SCRAPS FOR THE PRODUCTION OF MOTORCYCLE BRAKE-PAD

The increasing demand for aluminium-based products, coupled with globalization in the aluminium industry, has significantly heightened the consumption of aluminium scraps for the reproduction of aluminium alloys. This research investigated the effect of adding pure aluminium on the mechanical properties and structure of thick aluminium scraps, commonly used for the production of motorcycle brake pads. The first step of this work involved casting the materials using a crucible furnace. Samples were produced with and without pure aluminium, and their properties and structures were compared. The results of the mechanical tests showed the best performance in samples containing pure Aluminium scrap. The microstructure of the sample with pure Aluminium revealed refined grains, while that without pure Aluminium exhibited a coarse grain structure. This research provides insights into producing long-lasting motorcycle brake pads in the industry, aligning with Aluminium production objectives

Electrolytic synthesis of γ-Al2O3 nanoparticle from aluminum scrap for enhanced methylene blue adsorption: experimental and RSM modeling

The presence of methylene blue (MB) dye in wastewater has raised concern about human health and environmental ecology due to potential carcinogenic, and mutagenic effects. Therefore, this work aims to remove MB dye from wastewater using γ-Al2O3 nanoparticles synthesized from aluminum scrap via simple electrolytic method. The successful synthesis of the adsorbent was confirmed by a range of spectroscopy and microscopy techniques, including XRD, SEM, FTIR, and BET. The central composite design (CCD) of the response surface methodology (RSM) method was used to optimize the processing parameters such as solution pH, contact time, initial MB concentration, and adsorbent dose. The ANOVA results clearly shows that the quadratic model (p < 0.0001) was sufficient to the best predicting of the removal performance of MB dye (R2 = 0.9862). The optimum condition for the maximum MB dye removal (98.91%) was achieved at solution pH of 8.298, initial MB concentration of 31.657 mg/L, adsorbent dose of 0.387 g/L, and contact time of 46.728 min. Nano-γ-Al2O3 was shown to have a good surface area of 59 mg2/g by BET analysis. The adsorption kinetics follows the pseudo-second-order model (R2 = 0.997). With a maximum adsorption capacity of 137.17 mg/g, the Langmuir isotherm model (R2 = 984) provides the best fit to the adsorption isotherm data, indicating a monolayer adsorption process. Furthermore, thermodynamic analysis demonstrated that the adsorption of MB dye was an endothermic and spontaneous process. The reusability study showed that γ-Al2O3 nano-adsorbent retained 85.08% of its original removal efficiency after five cycles. According to the findings of the study, MB dye molecules were taken up by γ-Al2O3 nano-adsorbent via hydrogen bond formation, Van der Waals interaction, and electrostatic attraction. Therefore, γ-Al2O3 nanoparticles can be used as a potentially eco-friendly and low-cost adsorbent for the removal of MB dye from aqueous solutions.

Utilization of recycled coral sand and aluminum scraps in foam concrete: Preparation, insulation of environmental noise and heat, and pore structure

The utilization of industrial and marine wastes in building materials can significantly mitigate resource consumption and environmental hazards. In this study, the waste aluminum scraps and coral sand were utilized as foaming agent and fillers for foam concrete (FC) to address application challenges associated with industrial and marine wastes. Simultaneously, their impact on the mechanical property, heat and noise insulation properties, as well as pore structure of FC were investigated. The response surface methodology was used to optimize the mix design of FC. Heat and noise insulation characteristics of FC were tested by a visible infrared thermometer and a self-manufactured soundproof device, while the pore characteristic was analyzed by digital image processing technique. Additionally, the effect of foaming agents and coral sand on the internal pore structure of FC was studied by means of microscopic analysis(FTIR, XRD, SEM). The results show that foam content significantly influenced the performance of FC. As the foam content reached 15%, the compressive strength was the worst (ranging from 1.26 to 1.59MPa). Additionally, foam and coral sand inhibited the expansion of sulfoaluminate cement. At 15% foam content and 30% coral sand content, the thermal conductivity decreased to 0.082 W/(m·℃), representing a reduction of 52.5% compared to the control group. Regarding noise reduction performance, a foam content of 10% yields optimal results. The heat and noise insulation properties were both improved due to the enhanced porous structure of coral sand. However, excessive admixtures, such as 50 % content of coral sand, could weaken the strength by destroying the fine pore structure. Microscopic analysis further revealed that foaming agents could affect the hydration of cement with little impact on macro performance. Moreover, they also enhanced the toughness of bubbles and changed the surface structure of pore walls to ensure the integrity of the pore structure of FC.

Investigation of the Microstructure and Dry-Sliding Wear Behavior of Co Containing Al-Si-Fe Scrap Alloy

This study investigates the influence of cobalt (Co) addition on the microstructural and wear properties of an aluminum (Al) scrap alloy containing high iron (Fe) impurity content (3%). Microstructural analysis using scanning electron microscopy and optical microscopy confirmed the presence of Co in Fe-rich intermetallics. Upon increasing the Co concentration, β-Al5FeSi phase was seen to be refined without significant morphological modifications. Furthermore, Co addition promoted the formation of a new quaternary phase Al32Si7Fe4Co phase, which was finely distributed throughout the microstructure and acts as a tribo-layer in the Al scrap alloy, offering enhanced wear resistance and improved stability against wear. Standard EN-31 steel disk with compositions chromium (Cr)-1.6%, manganese (Mn)-0.75%, silicon (Si)-0.35%, and carbon (C)-0.9% was used for the wear test. Microhardness and wear properties were evaluated for both the as-cast and heat-treated alloys, with the as-cast samples exhibiting superior wear resistance and a lower coefficient of friction compared to the T6 heat-treated samples. Addition of Co showed refinement in the β-Fe rich intermetallics over the morphological modifications. Similarly, Co addition enhanced the hardness and wear resistance in the as cast alloys. This work provides a detailed analysis contributing significant understandings into the wear mechanisms and potential applications of Co modified recycled Al in various industrial sectors.

A study on production of hydrogen using Al scrap feedstock.

A sustainable future, concerning the energy transformation of a country, heavily relies on the availability of energy resources, particularly renewables such as solar, wind, hydropower, and clean hydrogen. Among these, hydrogen is the most promising energy source due to its high calorific value, ranging between 120 and 140MJ/kg. It has the potential to lead the market in various industries such as power generation, steel, chemical, petrochemical, and automotive. Significant research has been going on in hydrogen production technologies to reduce costs and improve competitiveness with fossil fuels. One such potential approach includes the use of metal-water reactions, which offer unique opportunities for producing clean hydrogen and other valuable byproducts. However, the quantity of hydrogen produced varies depending on the metal feedstock, type of electrolyte, and the activator or catalyst, used in combination with water. This latest work discusses recent progress on hydrogen production and the effects of variations in different parameters on the process, with a focus on aluminum (Al)-water reactions. Investigations have been conducted and reported on the effect of various activators with different concentrations, the quantity of aluminum scrap feedstock, and the volume of the electrolyte on the kinetics of the metal-water reactions and hydrogen production. Sodium hydroxide (NaOH) was observed to be more effective than potassium hydroxide (KOH) in promoting metal-water reactions. These activator-assisted metal-water reactions help produce clean hydrogen, along with other value-added products such as hydroxides. This work clearly sheds light on the potential utilization of industrial aluminum scrap as feedstock for producing clean hydrogen.

Influence of Copper Addition on the Mechanical Properties and Corrosion Resistance of Self-Hardening Secondary Aluminium Alloy AlZn10Si8Mg

Aluminium alloys have a wide range of applications, mainly due to their advantageous strength-to-weight ratio, denoted as specific strength and corrosion resistance. In recent decades, there has been a notable surge in the usage of recycled alloys, attributed to their reduced production costs and emissions. One of the conditions for secondary production is the optimal sorting of used scrap. Once the aluminium scrap has been melted, it is tough to reduce the content of the various additives. Copper is the primary alloying element in some aluminium alloys, which leads to an increased amount of copper in the aluminium scrap. Therefore, it is important to investigate its effect on the properties of aluminium alloys in which it is not commonly present. For this reason, this paper is concerned with the influence of copper on the microstructure and properties of the secondary aluminium alloy AlZn10Si8Mg. Specifically, it compares two melts of self-hardening AlZn10Si8Mg alloys differing in copper content (0.019% and 1.72%). A complex quantitative and metallographic analysis by optical and electron microscopy has been performed. Mechanical properties were investigated by tensile test, Brinell hardness, and Vickers microhardness measurements. The corrosion resistance of the individual melts was verified by the Audi test.

Synthesis of industrially appealing low-silica zeolites using aluminum scraps and sand

In this study, Carbon footprint (CF) and hydric footprint (HF) were estimated for the synthesis of zeolite A and X using aluminum cans and sand as sources of aluminum and silicon, respectively. The fuse reagent prepared from sand, at 250 and 500° C, and the filtrated of fuse reagent product were considered as input variables in the experimental design. Aluminum waste, the mixture of aluminum waste treated with sodium hydroxide, and the formed Al(OH)3 were also considered as input parameters for the aluminum sources. Results showed that for obtaining of the fuse reagent based on sand, a temperature as low as 250 °C was sufficient to obtain the desired zeolites A, X and P without increasing the CF or the HF. The type of aluminum source did not display a significant impact on the CF and FH for the synthesis of the targeted zeolites.

Electrocoagulation employing recycled aluminum electrodes for methylene blue remediation

This work focuses on the recycling of aluminum-based metal joinery waste in the context of the treatment of wastewater containing organic materials, such as dyes, by electrocoagulation (EC); aluminum scraps were used as electrodes to process synthetic solutions of the methylene blue (MB) dye. The study investigated the effect of different parameters, including pH (3, 4, 5, 7, 9, 11) current density (100, 150, 200, 250 A/m2), electrolysis time (30, 60,120 min), sodium chloride concentration (0.5, 1, 2 g/L) and the initial dye concentration (10, 20, 45, 60 mg/L) on the removal efficiency of MB. The results showed that the optimum conditions for MB removal were achieved at the original pH of the solution which is 7 using a current density of 200 A/m2 and an inter-electrode distance of 1 cm with 10 mg/L as a dye concentration and 2 g/L of electrolyte. The removal efficiency under these conditions can reach 97.81 %. An estimation was made of the electrical energy needed to attain the ideal removal, which was found to be approximately 0.97kWh/g removal dyestuff the electrode consumption was 0.13 (kgAl /g of dyestuff), with an operation cost of 0.106 ($/g of dyestuff). The study suggests that EC using only two aluminum electrodes is efficient technique for the removal of MB from synthetic wastewater. The removal of the dye was monitored by UV–visible spectroscopy and scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) is used for the identification of the functional groups of MB in the obtained sludge by the EC process; and the aluminum electrodes surfaces, before and after treatment, were characterized by scanning electron microscopy (SEM) and Dispersive Energy Spectroscopy (EDS).

Sustainable and Novel Development of Metal Matrix Composite Using Scrap Aluminium Alloy Reinforced with Scrap Borosilicate Glass Particles by Stir Casting Technique

This study aims to achieve a sustainable and environmentally friendly approach to the development of metal matrix composites (MMCs) by utilizing locally available Scrap Aluminium Engine Heads (SAEH) as the matrix material and powdered Scrap Borosilicate Glassware (SBG) as reinforcement. The stir casting technique was employed for composite fabrication, combining the benefits of cost-effectiveness and ease of processing. The research evaluates the mechanical properties of the developed MMC, including tensile strength, compressive strength, hardness, and impact resistance. Physical properties such as density and porosity were also investigated, alongside microstructural analysis using optical microscopy, scanning electron microscopy (SEM), SEM energy-dispersive X-ray analysis (EDAX), and X-ray diffraction (XRD). The results demonstrate a significant improvement in the mechanical properties of the composite compared to the as-cast SAEH material. The ultimate tensile strength increased from 70.3 MPa for as-cast SAEH to 117.3 MPa for SAEH reinforced with SBG. Similarly, ultimate compressive strength improved from 513.7 MPa to 700.67 MPa, and hardness increased from 32.56 HRB to 43.33 HRB. Furthermore, the impact strength showed a notable enhancement, increasing from 1.4 Joules to 1.8 Joules. Importantly, the porosity percentage decreased from 14.28% in as-cast SAEH to 9.97% in SAEH+BS composites, indicating improved material density. This research contributes to the development of sustainable MMCs using recycled materials, offering enhanced mechanical properties and reduced environmental impact, making it valuable for various engineering applications. By aligning with Sustainable Development Goals (SDGs), this study addresses key sustainability targets and underscores the importance of environmentally responsible materials development in advancing global sustainability efforts.

Utilization and Experimental Use of Stainless Steel Metal Scrap Machinery Waste, St-40 Iron, Copper and Aluminum to Reduce Co, Hc, Co2 Elements in Vehicle Exhaust

Air pollution due to motor vehicle exhaust emissions is increased. Polluted air harms human health dan the environment. Consequently, it is essential to make a sustained effort to reduce air pollution. The purpose of this research is to investigate the effect of adding aluminum scrap to the exhaust system of a motor vehicle on gas emissions composition. The motor vehicle exhaust system was modified to accommodate aluminum scrap placement. A gas analyzer was utilized to observe exhaust gas composition, such as carbon dioxide, hydrocarbon, and carbon monoxide. Aluminum scrap with different masses was wrapped around the exhaust's inner tube in 50 gr, 70 gr and 90 gr. The engine speed was maintained at 500 rpm throughout the testing process. It was found that the temperature of the outer exhaust tube is in a range of 40 degrees Celsius to 50 degrees Celsius. The results revealed that the most appropriate amount of aluminum scrap was 90 gr n to reduce carbon monoxide, hydrocarbon, and carbon dioxide in an exhausts gas. The surprising outcome was 76.78 % of carbon monoxide content declined, and furthermore hydrocarbon, and carbon dioxide content were deteriorated by 61.63% and 78.37%, respectively.

Development of geopolymer mortar made from bagasse ash with waste aluminum

Geopolymer concrete is a type of concrete that is produced using industrial waste materials such as fly ash, slag, and other similar materials instead of traditional Portland cement. This research studied the variables affecting geopolymer mortar from bagasse ash mixed with aluminum scraps. The waste materials, bagasse ash (BA) and aluminium scrap (AL) were crushed to reduce the particles by grinding. An amount of ALU 0.01 – 0.15 wt% bagasse (BA) ash was added to the mixture. The alkaline solutions (AS) used to leach silicon oxide and aluminium oxide from BA were sodium hydroxide (NH) and sodium silicate (NS). The concentration of NH solution was varied between 7.5 – 15 molar. The ratio of alkaline solution to bagasse ash (AS/BA) was controlled at 0.50. Mortar samples were cast and cured at 60 80 and 100 °C for 48 hours. The results showed that the 10-molar sodium hydroxide solution tended to support the higher compressive strength. The highest compressive strength of geopolymer was found when using 0.04% aluminum scrap and curing at 80 °C. The additional water improved the workability of the fresh mortar, but the lower strength of the geopolymers was archived. GRAPHICAL ABSTRACT HIGHLIGHTS Do not use as a cementitious binder Reuse waste materials It is an environmentally friendly and sustainable material

Corrosion, wear and machinability studies on scrap aluminium alloy wheel based metal matrix composite

Recycled materials, especially scrap aluminum alloy wheels with reinforcement castings, are gaining applications in various fields such as aerospace, naval, military, and automobile. In this research, Honda car alloy wheels are stir-cast with 5% alumina as reinforcement and subjected to corrosion, wear, and machinability studies. Corrosion studies were conducted to evaluate the corrosion current density (ICorr), corrosion potential (ECorr), and corrosion rate for the cast aluminum metal matrix composite. The wear studies with different loads, i.e., 50 N, 60 N, 70 N, and 80 N, were performed on the specimen and investigated the coefficient of friction, frictional force, and pin temperature. The sliding load has a significant effect on wear performance, and for the sliding load of 80 N, the wear recorded was 2574.83 µm. The electrochemical machinability studies with voltage, duty cycle, and concentration of citric acid electrolyte are performed on the machining rate and surface corrosion factor. Analysis of the electrochemical machining process with PROMETHEE-II shows that 7 V, 60% duty cycle, and 30 g/L electrolyte concentration are estimated to be the best combination for a higher machining rate and a lower surface corrosion factor. KEY WORDS: Alumina, Machining rate, Nyquist plot, Electrochemical machining, PROMETHEE-II Bull. Chem. Soc. Ethiop. 2024, 38(4), 1163-1175. DOI: https://dx.doi.org/10.4314/bcse.v38i4.27

Effects of Fe content on the 3D morphology of Fe-rich phases and mechanical properties of cast Al-Mg-Si alloy

Fe is a common impurity element in recycled aluminum scraps, and adjusting Fe content can effectively promote the effective utilization of recycled aluminum. In this study, Al-Mg-Si-Mn-Fe alloys with different Fe contents were prepared by adding various percentage of aluminum scraps. Synchrotron X-ray tomography technology was used to study the morphological evolution of Fe-rich phases and corresponding effect on mechanical properties of studied alloys. The results showed that as the Fe content increased, the 3D morphology of Fe-rich phases changed from fine Chinese-script and needle-like shapes to coarse Chinese-script structure. Their 3D morphology was mainly composed of thin platelets and curved branches. The increase in Fe content did not significantly change the 3D structure of Fe-rich phases, but increased the volume fraction of large Fe-rich phases. When the Fe content reached 0.35 %, the maximum volume and the number of branches of individual phases increased by 182.9 % and 142.2 %, respectively, compared with the 0.2Fe alloy. With the increase of Fe content, the ductility of alloys gradually decreased, especially when the Fe content exceeded 0.25 %. The Fe content had a small effect on the liquidus temperature of alloys, but it changed the initial formation temperature and type of Fe-rich phases. When the Fe content exceeded 0.32 %, it promoted the formation of β-Fe phase, which may be the main reason for the significant decrease in ductility of studied alloys with higher Fe content.

Analysis of 3D-Printing Layer Height Pattern Effect to ADC12’s Mechanical Properties Investment Casting Results

This study aims to determine the mechanical properties, both hardness and tensile strength of investment casting results from 3D-Printing patterns. In this analysis, the aluminum scrap comes from the piston and will later be Die Casted and become ADC 12. The pattern used Poly Lactid Acid material, then the pattern is printed with varying layer height. After that, analysis was carried out using experimental for surface roughness and hardness of ADC12. The Hardness value is used to get the Tensile strength of ADC12 from empirical aproach. The results of the analysis show that the hardness and tensile strength of the ADC12 casting investment product have decreased due to the increasing value of the surface roughness of the cast product which is influenced by the use of a larger layer thickness.