Revolutionizing Materials Manufacturing: A Deep Dive into Kobe Steel's Advanced Casting Technology for a Carbon-Neutral Future
This technical summary is based on the academic paper "Melting, Casting, and Welding Technologies Supporting the Art of Manufacturing in Materials Business" by Dr. Hitoshi ISHIDA, published in KOBELCO TECHNOLOGY REVIEW (NO. 42 FEB. 2025)..
Keywords
- Primary Keyword: Advanced Casting Technology
- Secondary Keywords: Melting Technology, Welding Technology, Resource Circulation, Carbon Neutrality in Manufacturing, Kobe Steel Technology, Steelmaking Process, Aluminum Casting, Titanium Melting
Executive Summary
- The Challenge: To maintain high product quality and achieve carbon neutrality amidst degrading raw material quality and increasing pressure to use recycled materials.
- The Method: A systematic refinement of core melting, casting, and welding technologies across diverse materials—including steel, aluminum, copper, and titanium—by controlling high-temperature metallurgical reactions and solidification structures.
- The Key Breakthrough: The development of integrated processes that not only enhance product quality, such as creating super-clean steel with over 20% greater fatigue strength, but also enable resource circulation by using by-products like arc furnace ash as refining agents.
- The Bottom Line: A holistic approach to materials manufacturing, where advanced casting technology is pivotal for producing high-value products efficiently while actively contributing to a green, sustainable society.
The Challenge: Why This Research Matters for HPDC Professionals
In today's manufacturing landscape, engineers and managers face a dual challenge. On one hand, the quality of raw materials is declining while procurement risks are rising. On the other, there is an urgent, industry-wide mandate to reduce CO₂ emissions, expand the use of recycled materials, and move toward carbon neutrality. These pressures are not abstract; they directly impact the quality, cost, and reliability of the final product. For professionals in casting and materials processing, the starting point of the entire value chain—the melting and casting process—is under intense scrutiny. How can we remove impurities from low-grade materials? How can we prevent defects and ensure the structural integrity of components made from recycled scrap? This paper addresses these exact pain points, detailing the core technologies required to turn these challenges into a competitive advantage.
The Approach: Unpacking the Methodology
Kobe Steel has systematically refined its core technologies by integrating fundamental metallurgical principles with advanced analytical techniques. The approach is rooted in three indispensable process pillars:
Method 1: Advanced Melting Technology
This involves the precise control of high-temperature metallurgical phenomena. The goal is to fine-tune material composition, remove impurities like unnecessary components and gases, and achieve a high level of cleanliness. This is accomplished through refining reactions that are foundational to the quality of the end product.
Method 2: High-Fidelity Casting Technology
This technology focuses on controlling the solidification process to produce high-quality materials. Key objectives include preventing casting defects and cracking, refining crystalline grain structures, and managing the overall solidification structure. The methodology combines experimental analysis, such as water models, with advanced simulation tools for thermal stress and flow-solidification analysis.
Method 3: High-Reliability Welding Technology
As a critical process for joining structural materials, welding technology is developed to ensure excellent quality, efficiency, and workability. The approach involves controlling the melting and casting that occurs locally at the joint, managing high-temperature metallurgical reactions, and understanding solidification behavior to prevent defects like cracking.
The Breakthrough: Key Findings & Data
The paper highlights numerous technological advancements. Three key breakthroughs demonstrate the power of this integrated approach:
Finding 1: Dramatically Improved Steelmaking Efficiency and Cost-Effectiveness
Kobe Steel enhanced its hot-metal pretreatment process by installing mechanical stirring desulfurization units (KR) and converter-type dephosphorization furnaces. This strategic division of functions improved overall process efficiency. As shown in Figure 2, by optimizing impeller speed and immersion depth through water model experiments, the team achieved highly efficient desulfurization using inexpensive materials like aluminum ash and lime. This resulted in a high-efficiency, low-cost reaction for producing high-quality special-steel products.
Finding 2: Quantitative Prediction and Prevention of Aluminum Casting Cracks
Surface cracking is a major challenge in the direct chill (DC) casting of large aluminum ingots. The research established a quantitative method to evaluate crack susceptibility. As shown in Figure 4, by plotting a "crack initiation parameter" against a "crack propagation parameter," researchers could clearly define a "Crack area" for various alloys and casting rates. This model allows for the clarification of crack suppression strategies even for alloys with different initiation modes, providing a powerful tool for producing defect-free, high-quality aluminum.
Finding 3: Development of Super-Clean Steel with Superior Fatigue Strength
For critical components like engine crankshafts, cleanliness is paramount. By transitioning to a ladle refining furnace process, Kobe Steel enabled the substantial removal of impurities like sulfur and oxygen. This, combined with optimized inclusion control, led to the development of "super-clean steel." As shown in Figure 5, the fatigue strength of this super-clean steel is more than 20% greater than current clean steel and nearly 40% greater than conventional steel. This breakthrough allows for the design of engines with higher output and greater compactness.
Practical Implications for R&D and Operations
- For Process Engineers: This study suggests that strategically allotting refining functions in steelmaking, as detailed in Figure 1, can significantly shorten process times and improve crude steel production capacity. The data on desulfurization in Figure 2 indicates that optimizing mechanical stirring parameters can allow for the use of lower-cost raw materials without sacrificing quality.
- For Quality Control Teams: The data in Figure 4 provides a quantitative framework for establishing new quality inspection criteria for aluminum casting. By understanding an alloy's position on the crack susceptibility chart, teams can better predict and prevent surface crack defects. Similarly, the fatigue strength data in Figure 5 for super-clean steel provides a clear benchmark for qualifying materials for high-stress applications.
- For Design Engineers: The findings on super-clean steel's fatigue strength (Figure 5) indicate that components like crankshafts can be designed to be lighter or to withstand higher loads, enabling greater engine compactness and performance. This directly links materials processing breakthroughs to tangible design advantages.
Paper Details
Melting, Casting, and Welding Technologies Supporting the Art of Manufacturing in Materials Business
1. Overview:
- Title: Melting, Casting, and Welding Technologies Supporting the Art of Manufacturing in Materials Business
- Author: Dr. Hitoshi ISHIDA
- Year of publication: 2025
- Journal/academic society of publication: KOBELCO TECHNOLOGY REVIEW NO. 42
- Keywords: Melting, casting, welding, steel, aluminum, copper, titanium, carbon neutrality, resource circulation
2. Abstract:
Melting, casting, and welding are essential core technologies that support the art of manufacturing in the Kobelco Group's diverse materials businesses. Technological development has been promoted, considering the unique characteristics of each field: steel, aluminum, copper, cast & forged steel, titanium, and welding. In recent years, there has been a degradation in the quality of raw materials, leading to rapid demand for the expanded use of recycled materials from the perspective of CO₂ reduction and resource circulation. Numerous technologies are currently being developed with the aim of realizing carbon neutrality in the future. This article introduces the progress and future efforts related to melting, casting, and welding technologies in each materials business.
3. Introduction:
The KOBELCO Group manufactures a wide variety of materials, including steel, nonferrous materials (aluminum, copper, titanium), and welding consumables for industries such as automotive, aircraft, and shipbuilding. Recently, challenges have arisen from increased raw material prices, decreased quality, and the need to achieve carbon neutrality through CO₂ emission reduction and expanded use of recycled materials. Melting and casting are the critical first processes that determine final product quality. Welding is an indispensable joining process requiring high reliability. This paper defines Kobe Steel's core technologies—(1) Melting, (2) Casting, and (3) Welding—and introduces the progress and future prospects in these areas across each materials business, with a focus on reducing CO₂ emissions and utilizing low-grade, high-impurity materials.
4. Summary of the study:
Background of the research topic:
The materials manufacturing industry faces significant challenges due to deteriorating raw material quality, rising procurement risks, and the urgent need to reduce CO₂ emissions and promote resource circulation to achieve carbon neutrality. These factors demand innovation in the foundational processes of melting, casting, and welding.
Status of previous research:
Kobe Steel has a long history of developing and refining melting, casting, and welding technologies tailored to the specific needs of its diverse business sectors, including steel, aluminum, copper, cast and forged steel, titanium, and welding. This has involved applying high-temperature metallurgical reaction control, chemical engineering experiments, and flow-solidification analysis to improve quality and efficiency.
Purpose of the study:
This article aims to introduce the progress and future efforts related to melting, casting, and welding technologies within each of the KOBELCO Group's materials businesses. It highlights how these core technologies are being advanced to produce high-value-added products, support carbon neutrality, and enable the use of diverse and low-grade raw materials.
Core study:
The paper details technological advancements across several materials businesses. For steel, it describes the optimization of hot-metal pretreatment processes for efficiency and cost reduction. For aluminum, it presents a quantitative method for evaluating and preventing casting cracks. For cast and forged steel, it details the development of super-clean steel with significantly enhanced fatigue strength. For titanium, it discusses proprietary VAR and CCIM melting methods for high-quality ingot production and scrap recycling. For welding, it covers the development of technology to inhibit solidification cracking. The paper also presents forward-looking examples, such as using aluminum business by-products for steel desulfurization and developing new welding methods for emerging energy applications.
5. Research Methodology
Research Design:
The research presented is a comprehensive review of developmental studies conducted within the KOBELCO Group. The approach combines fundamental scientific principles (equilibrium theory, kinetics) with applied engineering techniques (process simulation, physical modeling) to solve specific manufacturing challenges in each materials sector.
Data Collection and Analysis Methods:
The methodologies employed include a range of experimental and analytical techniques:
- Physical Modeling: Water model experiments were used to simulate and optimize fluid dynamics, such as the dispersion of desulfurizer by an impeller in the KR process.
- Process Simulation: Rate equations, thermal stress analysis, and flow-solidification analysis were used to optimize processes like dephosphorization, predict casting defects, and design ideal mold shapes.
- Laboratory and Pilot-Scale Testing: 5-ton KR testing and 300-kg laboratory tests were conducted to validate new processes, such as desulfurization using arc furnace ash.
- Material Characterization: Mechanical testing, such as fatigue strength evaluation, was performed to quantify the performance improvements of newly developed materials like super-clean steel.
Research Topics and Scope:
The scope covers the core manufacturing technologies of melting, casting, and welding across five distinct materials businesses: steel, aluminum, copper, cast and forged steel, and titanium, as well as the welding business. The research topics range from process efficiency improvements and quality control to the development of technologies for resource circulation and carbon neutrality.
6. Key Results:
Key Results:
- A new hot-metal pretreatment plant for steelmaking improved process efficiency and capacity by allotting refining functions, enabling the use of inexpensive materials for highly efficient desulfurization.
- A quantitative evaluation method for crack susceptibility in aluminum DC casting was developed, enabling targeted crack prevention strategies based on alloy composition and casting rate.
- "Super-clean steel" was developed for crankshafts, exhibiting over 20% greater fatigue strength than current clean steel, enabling higher-performance engines.
- A proprietary "Kobe Method" for titanium VAR melting reduces melting time by 50% and electricity consumption by 60% while allowing for the use of scrap.
- A resource circulation loop was established by successfully using arc furnace ash, a by-product from the aluminum business, as a desulfurization agent in the steelmaking process.
- A new deoxidation technique for TiAl intermetallic compounds was developed, enabling maximum scrap recycling and supporting the production of lightweight aerospace components.
- A new electroslag welding (ESW) method was developed, improving weldability and quality for thick plates used in applications like 9% Ni steel for LNG storage.
Figure Name List:
- Fig. 1 Improvement by allotment of refining function in hot-metal pretreatment
- Fig. 2 Effect of impeller speed and immersion depth on dispersion of desulfurization agent
- Fig. 3 Effect of RH treatment conditions on [N] content (calculation results)
- Fig. 4 Crack susceptibility evaluation of each alloy by crack susceptibility parameter and crack prevention concept for each group
- Fig. 5 Fatigue strength of super clean steel for solid type crankshaft
- Fig. 6 Effect of aluminum concentration on deoxidation behavior in molten TiAl with flux addition
7. Conclusion:
Kobe Steel has developed and refined melting, casting, and welding technologies tailored to the specific needs of its diverse materials businesses. The future vision is a sustainable world realized through carbon neutrality and resource recycling. The company aims to support both CO₂ reduction and resource circulation by integrating the diverse technological capabilities of its materials businesses in the ongoing development of these core technologies.
8. References:
- 1) T. Hamada. R&D Kobe Steel Engineering Reports. 2019, Vol.69, No.2, pp.3-8.
- 2) K. Nakayama et al. R&D Kobe Steel Engineering Reports. 2001, Vol.51, No.3, pp.2-8.
- 3) K. Saito et al. R&D Kobe Steel Engineering Reports. 2019, Vol.69, No.2, pp.32-36.
- 4) D. Watanabe et al. Iron Steel Technology. 2018, Vol.15, p.74.
- 5) T. Nishimura et al. R&D Kobe Steel Engineering Reports. 1997, Vol.47, No.3, pp.31-34.
- 6) T. Iwatani. R&D Kobe Steel Engineering Reports. 2018, Vol.68, No.2, pp.29-35.
- 7) Y. Yoshida et al. R&D Kobe Steel Engineering Reports. 2019, Vol.69, No.2, pp.26-31.
- 8) S. Kimura et al. R&D Kobe Steel Engineering Reports. 2004, Vol.54, No.3, pp.25-28.
- 9) S. Kimura et al. Iron and Steel. 2002, Vol.88, No.11, p.53.
- 10) T. Sugimura et al. ISIJ International. 2011, Vol.51, No.12, p.1982.
- 11) H. Ohta et al. R&D Kobe Steel Engineering Reports. 2011, Vol.61, No.1, pp.98-101.
- 12) K. Takahashi. Keikinzoku. 2015, Vol.65, No.10, pp.518-522.
- 13) K. Takahashi. Keikinzoku. 2015, Vol.65, No.11, pp.599-603.
- 14) M. Morishita et al. R&D Kobe Steel Engineering Reports. 2008, Vol.58, No.3, pp.23-28.
- 15) M. Morishita et al. Keikinzoku. 2009, Vol.59, No.8, pp.417-423.
- 16) M. Morishita et al. Mat. Trans. 2011, Vol.52, No.2, pp.166-172.
- 17) M. Morishita et al. R&D Kobe Steel Engineering Reports. 2012, Vol.62, No.2, pp.18-23.
- 18) K. Takeuchi et al. Journal of the Japan Copper and Brass Research Association. 1998, Vol.37, pp.182-188.
- 19) H. Ishitobi et al. Journal of the Japan Copper and Brass Research Association. 1998, Vol.37, pp.189-194.
- 20) H. Mori et al. R&D Kobe Steel Engineering Reports. 2000, Vol.50, No.3, pp.41-45.
- 21) M. Okamura et al. R&D Kobe Steel Engineering Reports. 1983, Vol.33, No.3, pp.3-7.
- 22) A. Suzuki. 10th International Forging Conference Sheffield. 1985.
- 23) T. Shinozaki et al. R&D Kobe Steel Engineering Reports. 2009, Vol.59, No.1, pp.94-97.
- 24) N. Fujitsuna. R&D Kobe Steel Engineering Reports. 2016, Vol.66, No.1, p.2-6.
- 25) T. Kusamichi et al. R&D Kobe Steel Engineering Reports. 1999, Vol.49, No.3, pp.13-14.
- 26) H. Yokoyama et al. R&D Kobe Steel Engineering Reports. 2005, Vol.55, No.3, pp.57-60.
- 27) M. Shimamoto et al. R&D Kobe Steel Engineering Reports. 2013, Vol.63, No.1, pp.32-36.
- 28) K. Tokuda. Keikinzoku. 2009, Vol.59, No.11, pp.652-653.
- 29) Takero Adachi et al. "Utilization of low-grade aluminum ash for mechanical stirring desulfurization process." 7th International Congress on Science and Technology of Steelmaking. Venice. 13-15 June 2018. Organized by ASSOCIAZIONE ITALIANA DI METALLURGIA. ICS081.
- 30) D. Matsuwaka et al. R&D Kobe Steel Engineering Reports. 2020, Vol.70, No.2, pp.27-31.
- 31) T. Kakizaki. Bodayori. 2020, Vol.507, p.2-6.
- 32) T. Kakizaki et al. Journal of the Japan Welding Society. 2021, Vol.90, No.6, pp.18-23.
Expert Q&A: Your Top Questions Answered
Q1: How exactly did Kobe Steel improve the efficiency of the hot-metal desulfurization process?
A1: The paper explains that efficiency was improved through intense stirring. As detailed on page 2 and in Figure 2, they used water model experiments and 5-ton KR testing to determine the optimal effects of impeller speed and immersion depth on desulfurizer dispersion. This allowed them to achieve highly efficient desulfurization using inexpensive materials like aluminum ash and lime, leading to a low-cost, high-efficiency reaction.
Q2: The paper mentions a quantitative method for evaluating crack susceptibility in aluminum. What is the underlying principle of this method?
A2: The principle, described on pages 3 and 4, is based on analyzing the semi-solidified region where cracks originate. It's hypothesized that cracking is caused by the disparity between the magnitude of shrinkage strain and the strain rate. The method calculates a "crack initiation parameter" (ΔRst/ΔTII) and a "crack propagation parameter" (ΔTII) to quantitatively express crack susceptibility, as visualized in Figure 4. This allows for a clear, data-driven approach to crack suppression.
Q3: What specific technological change enabled the production of "super-clean steel" with such high fatigue strength?
A3: According to page 5, the key change was transitioning from tap degassing to a ladle refining furnace process in 1993. This process, where molten steel is refined outside the electric furnace, enables the substantial removal of impurities like sulfur and gases like oxygen. This high level of cleanliness, achieved by reducing inclusions that are the origin of fatigue failure, is what gives the super-clean steel its superior fatigue strength, which is over 20% greater than conventional clean steel (Figure 5).
Q4: How does the "Kobe Method" for titanium VAR melting improve both efficiency and sustainability?
A4: The "Kobe Method," described on page 6, overcomes the challenge of using scrap as a raw material in the VAR process. It works by continuously introducing scrap fragments and other materials into the space between the consumable electrode and the crucible wall during melting. This results in highly efficient and homogeneous melting, which reduces melting time by 50% and electricity consumption by about 60%, directly improving both process efficiency and energy sustainability.
Q5: The paper highlights using arc furnace ash for desulfurization as an example of resource circulation. How does this work?
A5: This is a collaborative effort between Kobe Steel's steel and aluminum businesses, detailed on page 7. The Moka Aluminum Plant generates arc furnace ash as a residual by-product from recovering metallic aluminum from dross. This ash was found to contain aluminum nitride (AlN), which dissolves in molten iron and increases the concentration of aluminum available for desulfurization. By blending this by-product with the desulfurization agent at the Kakogawa Works steel plant, the company created a circular system that recycles a waste stream from one process as a valuable raw material in another.
Q6: Why is the CCIM method suitable for melting reactive alloys like Titanium Aluminide (TiAl)?
A6: As explained on page 7, CCIM (cold crucible induction melting) is suitable because it uses a crucible made of water-cooled copper segments instead of a traditional refractory crucible. This prevents reaction between the highly reactive molten TiAl and the crucible material, avoiding contamination. Furthermore, CCIM melts all raw materials at once, enabling easy adjustment of molten metal composition, which is critical for alloys with tight compositional tolerances.
Q7: What is the significance of the new electroslag welding (ESW) method mentioned for 9% Ni steel?
A7: The new ESW method, SESLA™, is significant because it improves the welding of extra-thick plates used in critical infrastructure, as noted on page 8. It maintains the advantages of traditional ESW (less spatter, good wind resistance) while overcoming its limitation of weld length. This is crucial for applications like liquid CO₂ storage tanks and offshore wind power equipment, which require high-quality, high-efficiency welding solutions to support the future carbon cycle and renewable energy sector.
Conclusion: Paving the Way for Higher Quality and Productivity
The core challenge of modern manufacturing is to deliver superior products while building a sustainable, circular economy. This research from Kobe Steel demonstrates that a deep, scientific understanding of foundational processes is the key to meeting this demand. By systematically advancing melting, casting, and welding, it is possible to not only mitigate the problems of poor raw material quality but also to create higher-performing products and innovative recycling loops. This commitment to Advanced Casting Technology and metallurgical excellence provides a clear roadmap for enhancing both quality and productivity in a carbon-neutral world.
"At CASTMAN, we are committed to applying the latest industry research to help our customers achieve higher productivity and quality. If the challenges discussed in this paper align with your operational goals, contact our engineering team to explore how these principles can be implemented in your components."
Copyright Information
This content is a summary and analysis based on the paper "Melting, Casting, and Welding Technologies Supporting the Art of Manufacturing in Materials Business" by "Dr. Hitoshi ISHIDA".
Source: KOBELCO TECHNOLOGY REVIEW NO. 42 FEB. 2025, pp. 22-30.
This material is for informational purposes only. Unauthorized commercial use is prohibited.
Copyright © 2025 CASTMAN. All rights reserved.