The role of universities in efforts to increase the added value of recycled bucket tooth products through product design methods

1.1 Low-carbon steel metal waste

The steel industry accounts for 24.9% of global emissions in the industrial and manufacturing sectors [1] and plays a key role in national economies. The extraction and transportation of iron ore, along with coal use in beneficiation, increase CO₂ emissions, which harm ecosystems and hinder sustainable development in the steel sector [2], Rising industrial activity leads to environmental challenges that are difficult to manage [3], highlighting the need to prioritize sustainability for future generations [4]. The mining sector is a major contributor to greenhouse gas emissions [5]. Coal mining in Indonesia produces 1.18 million tons of methane, equivalent to 101 million tons of CO₂, according to the International Energy Agency (IEA). Developing eco-friendly supply chains is crucial and reusing low-carbon steel component waste from earth-working tools (ground-engaging tools [GETs]) offers a potential solution. Steel consumption in Indonesia reached 17.4 million tons in 2023 and is expected to rise by 5.2% in 2024, driven in part by the automotive steel sector [6] steel consumption in Indonesia reached 17.4 million tons in 2023 and is projected to increase by 5.2% to 18.3 million tons in 2024, with a focus on supporting the automotive steel industry. Steel is a critical metal in modern life, and the price of steel scrap is considered a significant indicator of macroeconomic activity and investment [7]. BUMA, a mining service company in East Kalimantan, Indonesia, averaged 1,620.5 tons of GET spare parts waste from 2019 to 2021. GET metal contains over 94% iron (Fe) [8], providing opportunities for sustainable recycling and economic sustainability [9]. The Regulation of the Minister of Trade of the Republic of Indonesia Number 30 of 92/2019 classifies this waste as non-hazardous [10], making it suitable for reuse as a secondary material to reduce environmental pollution [11,12].

The utilization of GET metal waste through the extension of the product life cycle [13] supports the growth of the metal recovery industry [14] and is aligned with sustainability principles [15] to potentially reduce CO₂ emissions [16,17]. Redesigning products through recycling is an important step [13] in creating economic value that considers environmental and economic aspects [18], while supporting efficient secondary management [11] and environmentally friendly processes [19]. The main challenges faced by local industries in this management process include limited knowledge and development, supply chain management, especially the use of waste materials, sustainable recycling practices, and resource planning [10,16,20], as well as quality improvement [21]. Industries need to design supply chain networks that facilitate the exchange of ideas, and knowledge from universities, and technology [22,23]. Knowledge of metal products is essential for the process of developing better designs [9], processing and recycling technologies for optimal quality [24], and turning recycled materials into valuable new products [15,25]. This value chain advantage will transform GET waste into economically valuable products [26] to achieve economic value (20, 28) through an interactive innovation process [27].

1.2 The role of universities in the design and development process

In accordance with the Tri Darma of Higher Education, universities in Indonesia play a key role in addressing social and economic challenges [28]. Sharing knowledge and fostering innovation is crucial for both public and private sectors to stay competitive through advancements in information [10]. As part of the collective knowledge creation and application system, universities offer solutions focused on social and humanitarian innovation [9]. The success of these innovations relies not only on formal performance but also on collaboration among stakeholders [3]. Developing products from the waste materials of GETs is an eco-friendly and responsible way to tackle environmental, social, and economic issues [3]. A product design approach adds economic value by meeting specific market demands [29], with its commercial potential generating revenue through marketing and sales [30].

Collaboration is an effective way to promote knowledge transfer, organizational growth, innovation, and socio-economic development for small industries [10,31]. Research and development partnerships are often formed as joint efforts [13], providing a framework that defines participants’ roles and identities while contributing to a growing innovation ecosystem [14]. Shared knowledge-based values are established as organizational behavior [32], illustrating the synergy between education and business in the innovation ecosystem. Collaboration happens when two or more organizations work together to improve efficiency [20] and offer new pathways and perspectives for a knowledgeable industry community [17], contributing to the innovation ecosystem in traditional manufacturing [24]. Integrating strategic initiatives across the supply chain, from upstream to downstream, is key to improving overall performance [20]. The quality of this integration helps create opportunities for members to share information and resources and take initiative [21]. Collaboration in traditional manufacturing supports the move toward a sustainable economy [25] and enhances organizational resources within business networks [4]. A major challenge for the medium foundry industry in Indonesia is a lack of technical expertise. Business collaboration is needed to overcome this barrier by developing new ideas for improvement that aim to create benefits [24] in the face of global challenges [18]. The university plays an important role in promoting an open innovation system through partnerships, sharing ideas, knowledge, and technology with other organizations [33] to offer customers effective research and product development solutions [14,34].

2.1 Qualitative methods

The grounded theory approach was used to explore the role of universities by identifying key factors in collaborative activities [39]. The study employed systematic inductive methods, including data analysis, summarization, and theory development. Semi-structured interviews were conducted with key participants, such as the Director of Human Resources & Culture at a mining services company, the General Manager of Transformation, an on-site Project Manager, university researchers, and foundry small and medium-sized enterprise (SME) business owners. Twelve participants (11 men and 1 woman) took part, each playing a key role in shaping business strategies and goals. Data analysis was carried out in three phases: (1) open coding, (2) axial coding, and (3) selective coding [40]. Coding is an analytical process that organizes concepts by properties and dimensions [41], serving as a “critical link” between data collection and interpreting its meaning [40], as outlined below:

2.2 Quantitative methods

In this study, we combine a quantitative method and laboratory investigation [43] to examine the low-carbon steel waste from the residue of GETs of heavy equipment used in coal mining activities. Bucket teeth were extracted from mining areas in BUMA, located in Berau, Kutai Kertanegara, and Tanah Bumbu Regencies. The dimension and original design and specific dimension of GET are shown in Figure 1. In this study, we used a bucket tooth with Series 200T which is usually used in the mining sector for digging, trenching, grading, and material handling.

Figure 1

Testing of material samples using the quench oil-cooled and tempered methods.

Material composition was tested using the optical emission spectroscopy (OES) and the Bruker Q4 Tazman instrument (Bruker, Massachusetts, USA). The OES method is highly effective for analyzing the elemental composition of various materials, including metals and metal alloys. Ensuring the safety, efficiency, and longevity of bucket tooth products requires thorough durability testing. The spectrometry test was conducted to analyze the composition of the original bucket tooth (OBT), which was performed on several OBT specimens. Based on the analysis, the OBT mainly comprised 93.70% Fe (Iron), and some elements are shown in Table 1.

Understanding ferrous classification refers to the understanding of the grouping and classification of different types of ferrous metals based on their chemical composition. Ferrous metals are a type of metal that contains iron as the main component, and they are often used in various industrial applications due to their strong mechanical properties and resistance to corrosion. The remaining components of bucket tooth are included in the category of low carbon steel which is classified as part of low alloy steel. Low alloy steel is a type of steel that contains relatively low amounts of alloying elements compared to high alloy steel or alloy steel. These alloying elements, such as manganese, nickel, chromium, molybdenum, and others, are added to steel to improve certain properties, such as strength, hardness, toughness, and corrosion resistance. In this study, we also conducted several tests to determine the quality of the environment of the mining sector including rocks and the chemical composition of scraps. To determine the crystal structure of minerals contained in rock samples, an X-ray diffraction (XRD) test was carried out using a Panalytical X’pert Pro X-Ray Diffractometer PW3040/x0 (Malvern, UK). Conversely, X-ray fluorescence (XRF) testing, which includes stimulating atoms with X-rays, was used to analyze the chemical composition of rock samples. The stimulation produces fluorescence, which is measured to determine the concentration of chemical elements present. Instruments, such as the ARL 9900, Thermo 502, and Bruker S1 Turbo SD, are commonly used (Bruker). Aside from XRD and XRF testing, we also conducted the Los Angeles method to perform an abrasive test. This laboratory test method evaluates the wear or hardness of coarse aggregates by measuring the resistance to abrasion or friction produced by the movement of aggregate grains in a cylindrical tube. The Los Angeles test procedure follows the SNI Standard 2417 to 2008 guidelines. By combining various testing methods, any deficiencies or potential problems with bucket tooth can be identified and corrected before being actively used in the field. The durability tests include environmental, material, mechanical design, and non-destructive tests (NDT).

The characteristics and properties of sedimentary rocks at the coal mine site play a crucial role in the necessary design method. This method includes analyzing the composition and mineral content of these rocks. Sedimentary rocks are formed through deposition processes influenced by specific environmental conditions, including pressure (P) and temperature (T) [44]. Therefore, this method entails examining the mineral content in sandstone, which dominates the coal mining environment. Sandstone sediment rock was sampled at three locations for material testing, each representing distinct workplace and environmental characteristics. Laboratory testing was performed using the XRD method on several samples to analyze the lithology at the workplace.

2.2.1 Mechanical design

2.2.1.1 Heat treatment

The heat treatment process is carried out using equipment with an electric power source to obtain the stability of the heating process namely Electrical Resistance Heat Treatment Furnace, Model RT3-80-12, rate power 80 kW, maximum temperature 1,200°C, and chamber size 1,000 × 800 × 1,000. Referring to the scale of Grade SCMnCr4, a Brinell hardness value of 223 HB was obtained at the tempering point after quenching. Adhering to the JIS G5111 standard for SCrMn4, this 223 Brinell (HB) value corresponded to 20 HRC on the Rockwell C scale. Achieving a hardness value of 42 HRC required a controlled heat treatment process, including precise engineering for controlled heating and cooling. The heat treatment, a controlled heating and cooling method, was conducted to achieve the desired mechanical property of tensile strength. The process outlined in the ASM Handbook Vol 9 [45] and ASTM chapter A216 included quenching at 950°C with a 1.30-h hold, followed by tempering at 350°C for 3.30 h, as shown in Figure 1. This regimen is crucial for adjusting the properties of the material to meet specific mechanical requirements, enhancing strength and durability for intended applications.

The subsequent process involves reheating the carbon steel bucket tooth samples to a specific temperature lower than the austenitization temperature. This temperature ranges between 150 and 650°C. In this case, the metal is held at a tempering temperature of 300°C for a certain period, 4 h Figure 2. At this temperature, the mechanical properties of the metal, such as reduced brittleness, increased elasticity, decreased cracking, and improved impact resistance, are expected to be achieved. After this process, the metal is then slowly cooled in ambient air to complete the tempering process. At this temperature, the mechanical properties of the metal, such as reduced brittleness, increased elasticity, decreased cracking, and improved impact resistance, are expected to be achieved. After this process, the metal is then slowly cooled in ambient air to complete the tempering process.

Figure 2

Testing of material samples using the tempered methods.

2.2.1.2 Tensile strength

The test was conducted using Micro Computer Universal Testing no 1485 with HT 950-1 specifications: capacity 50,000 kg, stroke 250 mm, and power requirement 220 V. The sample has a length of 240 mm placed on the testing machine in a vertical position, as shown in Table 2.

Table 2

Standard strength and tensile properties (JIS G5111, SCrMn4 mechanical properties)

Assortment	Yield point on proof stress (N/mm2)	Tensile strength (N/mm2)	Elongation (%)	Reduction of area
Tempering after normalizing	410	690	9	20
Tempering after quenching	540	740	13	25

2.2.1.3 NDT

NDT uses methods to inspect, test, and evaluate materials, components, or structures without causing damage or altering their integrity. These techniques can identify defects or property changes without harming the object being examined. Such flaws can impact the durability and mechanical properties of metals, potentially causing economic losses. Common NDT methods, like ultrasonic, photoacoustic, and magnetic particle testing, are widely used to find metal defects. Ultrasonic testing (UT) uses sound waves to locate flaws and check structural integrity, ensuring the metal meets design specifications [46]. During testing, a specific test area limit of 16 mm² from the total inspection area is examined, as shown in Figure 3. The maximum allowable tolerance for the depth of ultrasonic wave reflection is set at ±2% (16 mm²) from 800 mm² of the inspection area [47], aiming to identify delamination or non-diffusion of material.

Figure 3

Ultrasonic test inspection area.

3.1 Grounded theory approaches

Analysis of the interview results with 12 key informants representing the interests of universities, SMEs, and users revealed 23 conceptual ideas, which were grouped into 12 categories, as shown in Figure 4. The findings, gathered from interviews, observations, and documents, identify and label relevant pieces of information. The identification of data codes in detail is central to representing and understanding the phenomenon of university roles. The results of the open coding stage consist of a collection of codes and concepts that serve as the foundation for further analysis, aimed at developing relationships between these concepts to form a more coherent theory.

Figure 4

Open coding (code and categories).

The second stage is axial coding, which connects and organizes the categories identified during the open coding stage. A thorough analysis was conducted to understand the relationships between these concepts. Axial coding helps to transform scattered or unstructured data into more organized and systematic categories. The researcher explored how these categories could be further explained and linked, making it easier to understand the dynamics within the five categories shown in Figure 5.

Figure 5

Axial coding model.

As shown in Figure 5, the blue box labeled knowledge transfer highlights one of the key strategies in this collaboration. Knowledge transfer represents the role of universities in disseminating knowledge to the collaborating stakeholders.

In the third stage, selective coding is used to filter and integrate the main categories identified during open and axial coding, leading to the development of a core narrative or theory explaining the phenomenon under study. The findings from open and axial coding provide an overview of the phenomenon emerging from the need for collaboration. This core theory highlights the central elements that connect all identified categories and subcategories, linking relevant data parts and aligning the findings for a more structured and in-depth understanding of the collaboration phenomenon. Based on the study results and theoretical framework, a conceptual model is created to illustrate how the relevant categories interrelate and influence one another. This model serves as a theoretical framework to explain, predict, or interpret the phenomenon of collaboration, particularly in the context of partnership.

3.2 Product design properties

The focus lies on environmental commitment, specifically regarding the development of products using waste from residual components of low-carbon steel GET. This shows the conscious efforts of individuals or groups to contribute both directly and indirectly to environmental well-being [48]. Absorptive capacity, which influences the flexibility of strategies and innovations, is important in this context [49]. In a knowledge-based economy, innovation performance relies on formal measures and the ability to interact and use collective knowledge effectively, thereby enhancing the competitiveness of an organization [10,50]. Absorptive capacity is essential for improving the ability to innovate and produce new products. The reduce–reuse–recycle framework integrates environmental or ecological and economic perspectives but often affects efforts to hinder production growth. A transition towards more environmentally friendly production methods is required as a bridge toward economically valuable product design innovation. Product design referred to in this method focused on the development standards feasible for implementation in small-scale or local industries, comprising (1) workplace environmental method where component units were used, (2) mechanical design specifications, (3) chemical composition, and (4) product functionality.

3.2.1 Workplace environmental testing

The characteristics and properties of sedimentary rocks at coal mine sites play an important role in the required design methods. This method includes analyzing the composition and mineral content of these rocks. Therefore, this method entails examining the mineral content in sandstone, which dominates the coal mining environment. Sandstone sedimentary rocks were sampled at three locations for material testing, each representing different workplace and environmental characteristics. Laboratory testing was carried out using the XRD method on several samples to analyze lithology in the workplace.

Testing procedures were conducted following the GL-MU_1.2 method 4.2.2, 4.3.2, 4.4.2, and bulk preparation. Samples were taken from locations coded as Binungan (B), Sungaidanau Jaya (S), and T (Tabang) in East Kalimantan, Indonesia. The Quartz mineral is described macroscopically as being present in sand-sized grains of 1/8 to 1/4 mm, showing physical attributes associated with abrasiveness or erosion. Sandstone composition, microstructure, pore distribution, and mechanical properties are interconnected [51]. Figure 6 shows the results of the Sedimentary rock or solid test conducted using the XRF method. The results obtained from XRD and XRF tests are integral to the design specification process. These tests provide valuable insights into the mineralogical and elemental composition of the sedimentary rock. Additionally, XRD and XRF aid in understanding the interaction between metal and specific sedimentary rock characteristics, providing essential information for designing materials capable of effectively handling or interacting with rock formations.

Figure 6

Sedimentary rock/solid test results using the XRF method.

3.2.2 Secondary material testing

Based on Callister [8], with a carbon content of approximately 0.299%, the GET material is classified as low-carbon steel. This carbon content, which is less than 0.25% by weight, imparts softer and more malleable properties to the material while retaining adequate strength for various applications. Callister [8] also categorize this GET waste as a ferrous metal, with iron (Fe) as the primary component. The remaining components of the bucket teeth are classified as low-alloy steel, which contains fewer alloying elements compared to high-alloy steel. Alloying elements such as manganese, nickel, chromium, and molybdenum are added to enhance strength, hardness, toughness, and corrosion resistance. Low-carbon steel, with carbon (C) content ranging from 0.0 to 1.5% [52], is a specific type of steel alloy. The secondary raw material processing, in terms of design, refers to the Japanese Standard Casting, JIS 5111 (Japanese Steel Alloy – High tensile strength carbon steel castings and low alloy steel casting for structural purposes), which specifies the following values C: 0.35–0.45, Si: 0.3–0.6, Mn: 1.2–1.6, P: max 0.04, S: max 0.04, and Cr: 0.4–0.8. The identification of low-carbon steel as a secondary raw material refers to the SCrMn4 group, as shown in Table 3.

Table 3

Chemical composition testing of secondary material samples

No	Specimens	Chemical composition (%)
		C	Si	Mn	P	S	Cr	Mo	Ni	Cu
1.	SBT-01	0.209	0.630	0.686	0.013	0.006	2.545	0.091	2.851	0.429
2.	SBT-02	0.266	0.630	0.967	0.017	0.023	2.366	0.144	2.807	0.575
3.	SBT-03	0.228	0.483	0.843	0.017	0.005	2.390	0.242	2.687	0.628
4.	SBT-04	0.254	0.492	0.904	0.041	0.006	2.409	0.272	2.831	0.583
5.	SBT-05	0.218	0.574	0.982	0.013	0.006	2.475	0.268	2.892	0.624

Based on the provisions and standards referring to ASM Handbook Vol 9 [45] and ASTM chapter A216, the test results on the Code B (Nital Etching) sample with the IK 5.4-1-4 test method and the type of photomicrographic metallographic test results in Figure 7, taken at 200× magnification, show the four-phase microstructure of controlled heating and cooling during heat treatment. These transformations show changes in material properties, such as hardness, strength, and tenacity. Therefore, understanding this phase is important for determining the mechanical behavior of materials and their application in various industries, particularly in terms of durability and performance.

Figure 7

The results of microscopic structure analysis testing, appearance: (a) pearlite phase; (b) ferrite phase; (c) martensitic phase; and (d) chromium carbide phase at a magnification of 200×.

Phase identification is based on the appearance of standard characteristics observed during testing. According to preliminary studies, the dominant phase in the material is the martensitic, as shown in Figure 8 with a magnification of 500×.

Figure 8

The results of microscopic structure analysis testing martensitic phase, at a magnification of 500×.

In Figure 9, this phase is characterized by hardness and crackability, which are important considerations in the teeth design process. For comparison, it is shown in martensite phase conditions after process quenching.

Figure 9

The martensitic phase after the quenching process (ASM Handbook Vol. 9).

However, the inclusion of toughness, specifically during tempering in the heat treatment process, is important to prevent martensite cracking. The chromium carbide phase is formed due to the relatively high chromium content, thereby leading to carbon bonding with the metal to form a chromium carbide compound. The perlite phase is formed based on carbon content that reaches the austenite temperature in the product, showcasing both hardness and toughness. In addition, this phase originated from low carbon content and solubility, characterized by soft and ductile properties [45].

3.2.3 Mechanical design specification

Material selection principles must be in line with market or customer preferences, making the material essential to carefully select these items when designing mechanical specifications for a product. The considerations include diverse factors: (1) mechanical properties such as strength, toughness, hardness, and ductility, (2) physical properties namely thermal expansion, dimensions, and microstructure, and (3) chemical properties including corrosion resistance and reactivity to chemicals. Other factors considered include (1) technological availability for processing materials into finished products, (2) economic factors, including material and product prices, as well as production costs, and (3) availability of raw materials in the market.

3.2.3.1 Hardness

The hardness of a metallic material is a property that describes the resistance of a substance to penetration, abrasion, or plastic deformation. This property measures the difficulty associated with the change in shape or surface due to pressure and friction [8]. Based on the Mohs scale, metals have a hardness level of less than 7, which varies depending on chemical composition, heat treatment, and processing methods. The Mohs scale provides a relative measure of scratch resistance [50]. Several research adopted methods such as using microhardness and depth measurement indentation to determine the hardness of the first nine minerals on the Mohs scale, including talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, and corundum. Sedimentary rocks from the research area analyzed through XRD and XRF tests, predominantly contain the mineral quartz (SiO₂). In addition, quartz found on the Mohs scale, has a hardness level of 7, with resistance against penetration, deformation, or pressure-induced alterations. This property is significant in assessing the ability of the rock to withstand external forces such as pressure and friction. Friability, another crucial aspect affecting rock geomechanically properties, is closely associated with hardness, rock susceptibility, and cracking [53]. To establish a relationship between the dominant hardness of quartz mineral in sedimentary rocks and metal materials, the quartz hardness (SiO2) is converted to the Vickers hardness (HV) value obtained from the Bowieite mineral, which also ranked 7 on the Mohs scale or VHN100 = 858–1288. According to Callister [8], the optimal hardness value for steel materials is 746 HV, corresponding to 42 HRC. Hardness testing conducted with a Portable Rockwell Indenter on cast materials was used to generate graphs and corresponding values shown in Figure 10.

Figure 10

Impact and hardness testing of low carbon steel metal waste.

Table 4 shows a range of HV values between 386.7 and 407.4 HV for the original component material, suggesting a consistent level across the specimens tested. This consistent range is crucial for re-engineering low-carbon steel waste into new components. Engineers use the HV values data as a benchmark to customize manufacturing and design processes, ensuring that the components possess mechanical properties like those needed for applications in line with the physical characteristics of the existing rock in the field. This is essential to guarantee the adaptability and reliability of the re-manufactured components in the intended environment or application.

Table 4

HV testing of original material

Specimen HV point	Impact energy (J)	Specimen HV hardness	Average HV hardness
H1	17.167	407.4	399.1
H2	19.848	386.7
H3	20.761	403.3

3.2.3.2 Tensile strength

The tensile strength of a metal material refers to the capability to resist forces exerted in tension without undergoing deformation or changes in the cross-sectional area. This force reaches a maximum capacity, known as tensile strength (Su), representing the maximum stress the material can endure before deformation occurs. The required strength and tensile values conform to the standards outlined in JIS G5111, particularly concerning the mechanical properties of grade SCrMn4. The results obtained from laboratory tests conducted on low-carbon steel metal samples are shown in Table 5. The results show that the raw material can withstand tensile stress ranging from 438.95 N/mm² to a maximum of 619.19 N/mm² at forces of 56,000.00 N and 74,775.00 N, respectively. These values show the ability of the material to respond to applied stress.

Table 5

Tensile strength test results of material samples

Description	No of specimen
	STS01	STS02	STS03	STS04	STS05
Area (mm2)	121.74	122.72	127.68	120.76	118.82
Max force (N)	59657.10	68924.70	56044.00	74775.00	71252.40
Yield strength (N/mm2)	337.60	341.43	164.00	367.82	299.04
Std. yield strength (N/mm2)	410.00	410.00	410.00	410.00	410.00
Tensile strength (N/mm2)	490.04	561.65	438.95	619.19	599.65
Std. tensile strength (N/mm2)	690.00	690.00	690.00	690.00	690.00

The sample’s maximum tensile strength is 619.19 N/mm², which is the highest force it can withstand before breaking. This shows the material’s capacity to handle tensile forces without fracturing. The maximum yield strength is 367.82 N/mm², marking the point at which the material begins to deform permanently and will not return to its original shape once the stress is removed. The material’s elongation ranges from 11.60 to 15.50% before it starts to deform.

3.2.3.3 NDT

Testing was conducted on 209 bucket tooth samples, as shown in Figure 11. The test showed no internal defects in products exceeding 16 mm², including porosity and lamination. The absence of inner defects beyond the specified area implied the high quality and reliability of the tested products, showing the suitability and structural integrity of bucket tooth for the intended applications.

Figure 11

Internal defect testing of the component using UT.

4.1 University roles

Collaboration across businesses, sectors, and geographic locations presents challenges, particularly in the management of low-carbon steel waste from mining. This ecosystem includes universities, metal foundry SMEs, and product user industries, built around the roles of various actors aiming to achieve high customer satisfaction and strengthen the independence of local metal foundry SMEs. Each entity has a defined position within this business model. Coherence is demonstrated through an agreement on the values of the strategic path, which includes knowledge transfer, supply chain, communication, and synergy. Interview results from organizational leaders reveal that the relationships between these categories have formed a phenomenon, agreed upon as the key to success in addressing challenges and solving problems. This is reflected in the matrix of role division among the collaborating actors, as shown in Table 6.

4.2 Product design recycled bucket tooth parts

Measuring these requirements and characteristics is essential for determining product performance, such as lifespan and technical specifications. Bucket teeth are key components of excavators, mounted on the bucket edges for tasks like digging, breaking, raking, and moving materials like rock or mud. Product innovation focuses on recycling low-carbon steel waste to create products with a lifespan that meets market needs. Since 2019, 281 bucket teeth have been produced using knowledge applied to product design. Engineering efforts have concentrated on improving the recycled material’s chemical composition and mechanical properties to exceed the market standard of 450 working hours. Testing was conducted in the coal mining area of East Kalimantan, specifically in regions with sandstone containing 65–83% quartz (SiO₂). The chemical composition was compared to the standard (JIS G5111), with key adjustments made in chromium (Cr) and nickel (Ni) content to enhance hardness, strength, and resistance to abrasion and pressure. The increased percentages of Cr and Ni in the engineered composition reflect efforts to improve these key properties.

A nickel–chrome alloy (Ni–Cr) is a type of alloy consisting of Ni and Cr as the main elements, with the addition of two or more elements in specific ratios. This alloy has several properties that make it highly useful in various industrial applications, particularly in the manufacture of stainless steel. The properties and characteristics of this alloy include corrosion resistance, hardness and strength, heat resistance, and dimensional stability. Ni–Cr and Ni–Fe–Cr alloys are widely used as structural materials in harsh environments, such as in manufacturing, due to their high-temperature strength and corrosion resistance [54]. These alloys also exhibit high tensile strength, high yield strength, and excellent resistance to localized corrosion, pitting, and stress corrosion cracking [55]. Nickel-based superalloy products are utilized for their exceptional ability to withstand high temperatures and resist heat corrosion [56].

The final design of the bucket tooth focuses on meeting customer needs, emphasizing aesthetics, functionality, efficiency, quality, and reliability. The product features include a tiger crawl type, medium carbon steel, steel casting, and a weight of 49–50 kg, as shown Figure 12. It is made for 200-ton excavators, intended for use in sedimentary rock and coal mining areas. To improve hardness, strength, and resistance to abrasion and pressure, the metal composition is enhanced with Cr and Ni.

Figure 12

Product of bucket tooth.

This adjustment helps the product endure harsh conditions, particularly the abrasiveness of quartz in sedimentary rocks, as shown by Los Angeles test results indicating an abrasive value of about 40% for sand sedimentary rock, as shown in Table 7.

Product results of bucket tooth designs that refer to the JIS G511 standard are confirmed in Table 8. Where the results of this product design have adopted working environment conditions in the mining industry that functionally provide added value compared to products circulating in the market. Based on Table 8, recycled products (RP) show quite significant variations in chemical composition compared to the JIS G5111 standard and market products (MP). In general, although there are advantages in some elements such as chrome and nickel, variations in carbon, manganese, and silicon content can affect the mechanical performance of the material. In harsh mining environments, RP may have better corrosion resistance than MP, but reduced strength and toughness due to low carbon and manganese levels need to be considered.

Improvements in the recycling process to approach standards can provide more optimal added value for the industry. The integration of environmental management, economic well-being, and social responsibility in green supply chains increases the role of the environment in value creation in the supply chain. Examples include material recovery, quality improvement, and increased product selling value that surpasses previous products before recycling [57].

The need for innovation in the business environment is in line with the knowledge transfer policy [54]. Innovative environment-based processes have succeeded in reducing dependence on primary raw materials by extending the life of metals according to their characteristics [27]. Waste steel management as a sustainable strategy presents significant challenges for the supply chain [16], with a focus on reduction, reuse, recycling, and recovery [27]. Lopez et al. [58] highlighted the critical components in the development of RP and innovative ecosystems that support waste management [59]. Economic value is achieved through the integration of supply chain management strategies that create a measurable value proposition [60]. The existence of metal waste is an important part of the need for raw materials for MF SMEs. In accordance with the principles of the circular economy, which aims to maintain the value of assets across the natural resources, human, cultural, manufacturing, and economic sectors [10,60]. Until 2021, the implementation of this product design has involved local SMEs MF to produce 281 bucket tooth or equivalent to 15.1 tons to meet the needs of bucket teeth at BUMA. The longevity of the 531 HM bucket tooth provides a lower hourly cost perspective compared to the current 450 HM standard as shown in Figure 13.

Figure 13

Bucket tooth component lifespan.

The need for innovation in the business environment aligns with knowledge transfer policies [61]. Innovative processes driven by environmental concerns have effectively reduced dependence on primary raw materials by extending the life of metals according to their characteristics [27] Managing steel or scrap metal waste as a sustainable strategy poses a significant challenge for participants in the supply chain [16]. Focusing on reduction, reuse, recycling, and recovery throughout the production, consumption, and distribution cycles supports sustainability. Lopez et al. [58] identified critical components in managing the development of RP and innovative ecosystems that underpin waste management and recycling. This added economic value reflects the integration of supply.