Cast House Research Articles

Experience with the Use of Refractory Mixes in the Blast-Furnace Shop at Tulachermet

Results are reported from the use of unshaped refractory mixes at the Tulachermet company to line blast furnaces, the use of castable low-cement concretes for the system of troughs and hood covers in the cast house, and the use of high-durability notch mixes made by different manufacturers. Data are also reported from many years of use of concrete to line the main troughs. The factors that affect the durability of the lining are analyzed and solutions are found to technical and organizational problems, thus making it possible to increase the troughs’ service life, stabilize their performance, and improve working conditions. The article generalizes results obtained from use of the notch mixes and discusses new technical innovations developed to improve the technical-economic indices of blast furnaces and extend their useful life. One innovation examined in particular is a new technology for installing refractories. The technology entails the preliminary installation of a combination concrete lining on the surface of the blast-furnace coolers outside the furnace.

Properties and Performance of a Mud Gun Mass (Tap Hole Clay) with Respect to the Stable Application of the Product in Blast Furnaces

The new generation of blast furnaces have large volumes, operate at high maximum pressures, and increased blast temperatures. This has resulted in an increase in tapping rate, tapping temperature, and the duration of tapping. This has prompted changes in relation to material and application of refractories in cast house particularly in tap hole clays. The mud gun mass is prone to early erosion and therefore to obtain a trouble free cast, a good and strong tap hole mass with appropriate physical and chemical properties is required. The main physical need is to achieve trouble free tapping of hot metal, and for there to be a constant tap hole length during the tap hole opening operation, which usually takes an hour and ten minutes. Additionally there should be smooth flow of the hot metal and slag. The delivery speed of the hot needs to be as smooth as possible. These are physical requirements to protect the hearth of the blast furnace. This paper deals with the design, performance criteria, property evaluation, and application of a mud gun mass at blast furnace tap hole sites.

Challenges in Melt Furnace Tests

Measurement is a critical part of running a cast house. Key performance indicators such as energy intensity, production (or melt rate), downtime (or OEE), and melt loss must all be understood and monitored on a weekly or monthly basis. Continuous process variables such as bath temperature, flue temperature, and furnace pressure should be used to control the furnace systems along with storing the values in databases for later analysis. While using measurement to track furnace performance over time is important, there is also a time and place for short-term tests.

Mechanical Properties and Constitutive Behavior of as-Cast High Strength AA7xxx Alloys below Solidus Temperature

High strength AA7xxx alloys have been extensively used in aerospace industry. However, experience in cast house demonstrates that such alloys are particularly prone to cold cracking and ingot distortion during direct chill (DC) casting, which leads to big amount of scraping or even total rejection of ingot. Those stress induced defects are greatly affected by casting process, and fine tuning of casting parameters is critical to improve the quality and productivity. Recently, numerical modeling has been widely utilized in direct-chill casting for the purpose of thermal mechanical analysis and cracking evaluation. Parameter optimization has become convenient. The model needs the input of constitutive properties of the AA7xxx alloys, of which the microstructure should resemble those formed during DC casting. Unfortunately, these constitutive data are not yet available in literatures. In this study, the mechanical properties of two high strength AA7xxx alloys were measured at temperature range from solidus down to room temperature through on-cooling compressive tests and the effect of strain rate on stress-strain behavior was also studied. The results were fitted to extended Ludwik equation which has been proved to be able to properly describe the stress-strain response of aluminum alloys. The results of the current work shed some light on the evolution of mechanical behavior of high strength AA7xxx alloys during cooling from high temperature.

Statistical Analysis of Urban Growth in Kano Metropolis, Nigeria

Understanding and quantifying the spatio-temporal dynamics of urban growth in Kano Metropolis is necessary to put forward appropriate policies and monitoring strategies so as to make informed decision. The city has witnessed growth and infrastructural development such as low cast housing estates, highways and markets, to mention a few. This study examines the growth of Kano, Nigeria between 1986 and 2005 using remote sensing technology. Markov chain model was employed to predict future land use land cover in the area. Landsat images of 1986, 2000 and 2005 were classified into four land cover classes. Image classification analysis showed a rapid growth in built up land between 13.2% in 1986 to 19.3% in 2005 and an annual rate of change of 1.51% (1986-2000) and 1.24% (2000-2005). The period witnessed a reduction in vegetal cover from 33.9% by the year 1986 to 13.6% in 2005. Range land was recorded to occupy an average area of 56.4% in the 3 periods put together. It was also observed that change by 2015 will follow almost the same trend in the period studied with the built up area projected to cover (21.70%) of the total land area. The findings. The study indicated that in the last 19 years the built up area is increasing in size, and this have impact on the natural environment.

Dimensional analysis in the machining of housing components with cast holes

When cast housing components are machined, the displacement of the hole axis in reaming must be taken into account, because it produces pronounced nonuniformity of the margin. Means of reducing the machining error are analyzed.

Chemical profile identification of fugitive and confined particle emissions from an integrated iron and steelmaking plant

The aim of this study is to obtain the characteristic inorganic chemical profile of important particle sources identified in the integrated iron and steel process: sintering, blast furnace, steelmaking and desulfurization slag processing. A complete chemical and physical characterization program was developed: particle size distribution, chemical analysis, XRD, SEM-EDX and TGA/DTA. The sample collected from the sinter stack showed high levels of K and Cl−, followed by Fe, NH4+, Ca, Na and Pb. The profile of the dust samples taken from the sinter cake discharge zone was quite different, showing higher amounts of Fe, Ca and Al, and lower amounts of K, Cl−, Na and Pb. Dust samples collected from the blast furnace (BF) and steelmaking cast house may be distinguished from each other based on the higher levels of Fe (hematite and magnetite) and lower levels of Ca, Zn and C (graphite) found in BF dust. High levels of Ca and Fe were found in samples taken from the desulfurization slag processing area. Such information can be useful for source apportionment studies at receptor sites that could be influenced by iron and steelmaking plant emissions.

Analysis and ergonomic improvement of working postures in cast house work station using JACK modelling

This paper presents the ergonomics design of work system which is a prerequisite for better safety, health and productivity of industrial workers. The awkward working postures adopted by the operators in cast house operations has been observed and analysed using photographic analysis, line diagram techniques and Ovako Working Posture Analysis System (OWAS). The awkward working postures leads to discomfort, inconvenience and risk of injuries and illness to workers. Various anthropometric measurements of workers and postures in various activities are collected and analysed to improve the working conditions. The cast house work system model is developed and simulated in the computer-aided ergonomics assessment platform JACK 5.1 with virtual workers with their specific anthropometric variables. An ergonomic work system specifying changes in the work procedures, work norms and ergonomic interventions has been proposed. A new control board with sit stand chair has been suggested which improves comfort to the operators.

Increasing Cast House Throughput through “In-Spec First Time”

Achieving in-specification melt analysis first time has been the Holy Grail of many cast houses for a number of years and for a good reason. For many producers, the furnaces are the bottleneck of the value added casting process and removing that hurdle means big dollars. A six sigma project was carried out at the Bell Bay smelter aimed at reducing the time it takes to bring a furnace within chemical specification and highlighted that “in-spec first time” is more achievable than many think. This paper covers the steps having an impact on alloy recovery and suggests a “best practice” to be followed in each area. As is shown, consistently following these guidelines through robust controls can generate a significant increase in throughput of value add facilities in your cast house.

Preserving Metal Units Utilising the Latest Generation of Aluminium Dross Press

The handling of dross is an unfortunate but necessary activity in any aluminum cast house. One technology designed to cool dross and maximise metal recoveries is the dross press. Since its introduction to the industry in the mid 1990’s this technology has evolved to meet the demands of the modern cast house and ever more stringent environmental legislation. This paper describes developments that address the weaknesses and limitations of early systems and enhancements that have enabled the cooling of a wide variety of dross types including salt slag from rotary furnaces. The paper will discuss data and results from the first fully commercialized installation of a specially designed press for cooling salt slag from Tilt Type Rotary Furnaces. Finally the paper will look at some of the economical benefits of using a press through various economic models showing the positive effect small improvements in dross recoveries can have on plant profitability.

Cost Savings in the Cast House through Optimizing Furnace Operation, Staff Training and Associated Variables

While it is generally acknowledged in our industry that people are the most important asset, the importance of technical training for furnace operators is often overlooked. The primary focus for training is often on the down stream process where the final product is either being cast or fabricated. The furnace operators have a key role since they have direct influence on factors that dramatically govern a range of costs factors which include: productivity; melt loss; metal content in the dross; energy usage, and metal cleanliness.

Implementation of CASTfill Low-Dross Pouring System for Ingot Casting

Producing low-dross ingots has been a long-term goal in aluminium cast houses. The patented CASTfill technology [1] is a low-dross and high-productivity pouring system developed to fulfil this demand. This paper describes the research methods used during the development of CASTfill; now in service at Boyne Smelters Limited (BSL) since August 2009. The importance of combining scientific modelling and testing procedures with process operability, maintainability and durability to ensure the success of new technology in a production facility is also highlighted. Ingot assessments showed that the latest CASTfill design greatly reduced dross generated during mould filling. Improved ingot packaging and reduced variation of ingot weights were also observed as the results of a more tranquil flow of molten aluminium through CASTfill and its uniquely modular design.

Hot Tearing in Al-Mg-Si Alloys with Minor Additions of Cu or Mn

A study of the influence of minor additions of copper or manganese on hot tear susceptibility in Al-Mg-Si alloys has been conducted. Testing was carried out using a laboratory scale hot tearing rig and the results were validated using an analysis of cast house cracking scrap data for 6060 and 6063 extrusion billet alloys. Mn content was found to have a strong influence on hot tearing rates.

The Metallurgy of Homogenisation

Homogenisation of aluminium alloys is the high temperature heat treatment (450-600 °C) performed after casting and consists of three distinct steps; heat-up, soak and cooldown. This review considers the metallurgical importance of homogenisation and how it impacts on the further processing and final properties of some aluminium alloys, with emphasis on homogenisation of extrusion billet. The introduction of continuous homogenisation has significantly improved the temperature uniformity of homogenisation allowing the soak time to be minimised. Batch homogenisation, however, provides flexibility in practices tailored for different aluminium alloys. Soft 6060 and 6063 alloys are best homogenised at a higher soak temperature than harder alloys such as 6061 and 6082. The homogenisation cooling rate can also impact on the behaviour of the billet during extrusion processing as well as affecting the final mechanical properties. An understanding of the microstructural changes occurring as a result of homogenisation allows the cast house to ensure that the billet processing meets the customer requirements.

Improved injury management at an Australian aluminium smelter

This longitudinal study sought to determine the effectiveness of interventions to improve injury management in an industrial setting. Study participants were workers from three production departments of a large aluminium smelter. The interventions introduced were to encourage active participation in rehabilitation procedures by injured workers, improve communication with all stakeholders, identify and manage psychosocial issues, and focus the workforce on occupational health and safety matters. Linear regression modelling was used to determine the effectiveness of the interventions using data collected for fourteen months before and fifteen months after the introduction of interventions. Outcomes compared were the number of injuries, number of persons on restricted duty, and lost hours per month. Modelling showed the intervention significantly reduced the number of injuries in the potrooms (from 14 to 6 per month). The number of persons on restricted duties was reduced in all departments (potrooms: from 12 to 7 persons per month, cast house: 3 to 1 person per month, carbon plant: 3 to 1 person per month). Lost hours were significantly reduced in the potrooms (from 244 to 61 hours per month). These findings demonstrate the effectiveness of the revised injury management process introduced.

Strategic steps towards longer and reliable blast furnace trough campaign – Tata Steel experience

At Tata Steel, Jamshedpur works the hot metal production capacity was enhanced from 3·57 mT in 1997–1998 to 5·51 mT in 2007–2008 with the same number of cast houses, thereby, increasing the thermal load on the runner system. Maximising trough availability and ensuring zero breakouts were the means to fulfill the objective of handling the increased furnace production. Significant changes in trough refractory design and introduction of new materials like prefabricated shapes helped to improve reliability of the troughs. The paper presents the design and mode of operation of main troughs of different blast furnaces (BFs) operated at Jamshedpur works, modification of trough design in the upgraded G-BF and its performance and details of improvements made in the trough back-up refractory lining, its wear monitoring and cooling systems.

Recent Developments in Australian Aluminium Casthouse Personal Protective Clothing

Abstract With the recent release of the Victorian WorkSafe Authority Foundries Compliance Code [1] it is appropriate that Australian Aluminium cast houses, die casting shops and foundries review the status of their personal protective clothing/ equipment (PPE) and practices. Since the issuing of the Foundry Code of Practice [2] in 1986 and the issuing of the new Compliance Code in September 2008 there has been a significant change in the range of PPE utilised in cast houses. This change has been brought about as a result of the advancement in the design and development of the materials used, extensive industry experience and collaboration. The choice of appropriate PPE is also guided by the range and impact of injuries sustained in cast houses. This paper aims to highlight the number of PPE advancements and range of experiences gained between the writing of the Foundry Code of Practice and Foundry Compliance Code as well as to serve as a reference for future improvements for the protection of cast house personnel.

Greenhouse Emissions in Primary Aluminium Smelter Cast Houses - A Life Cycle Analysis

The aluminium industry is reducing its carbon dioxide emissions and environmental footprint. In order to identify and prioritise areas in the cast house where greenhouse gas emissions can be reduced it is necessary to quantify CO2e (CO2 equivalent tonnes) emissions for the various cast house operations. In this study two typical cast house layouts are examined. In one case, 22kg 99.85% aluminium remelt ingots are produced using chain conveyor ingot casting machines. In the second case, wrought alloy extrusion and rolling slab direct chill cast products are made. Both plants are sized at 500ktpa. The various process inputs in terms of energy and materials were identified and typical usage rates assigned. The results show that general electricity consumption, dross generation and furnace energy consumption are the three biggest areas of CO2e and should be targeted for improvement. Magnesium consumption also has a large effect in the case of the

Fives Solios Experience in Modern Secondary Aluminium Casthouse Construction

In early 2006, Fives Solios, namely Solios Thermal, was selected as a key cast house supplier by a major aluminium producer for a new 130,000te/yr re-melting facility. The project scope included not only the supply of modern melting and holding furnaces plus ancillary equipment, but also pre-heating furnaces, an air pollution control system, basic cast house engineering, cooling water schemes and complete turnkey project management. This project presented particular technical and logistical challenges and was required to meet exacting European environmental / efficiency standards for all major contractors involved. The facility was commissioned in March 2008 and the first production was on schedule. This paper will discuss the challenges that the Solios Thermal project team had to overcome, from layout of equipment to conclusion of the project; also how good communication and close collaboration between the customer and all major subcontractors resulted in a successfully implemented plant.

Development of a Phosphate - Free Reticulated Foam Filter Material for Aluminium Cast Houses

Filtration of molten aluminium using porous reticulated ceramic foam was developed in 1974 by SELEE Corporation. Since that time, there have been significant technical advances in filter bowl design and construction, preheat systems, development of fine pore size filters, development of compact two-stage filtration systems, filter gasket materials, and equipment automation. One area that has remained relatively unchanged has been the refractory filter material technology. The refractory material utilized by all of the major cast house filter suppliers is based on an alumina aggregate grain bonded with aluminium phosphate (AlPO4). This filter material, commonly referred to as “PBA” in the aluminium industry, has become an industry wide standard and accounts for nearly 99% of the filters supplied to cast houses worldwide. There are significant technical limitations of PBA filters in terms of refractory performance, as well as potential environmental, health and safety concerns. This paper describes the development of a cost effective replacement filter material that overcomes the limitations of PBA filters. The new material utilizes a low expansion – low modulus aggregate material and a non-phosphate bond. The result is a significant reduction in mechanical failures during use, improved filtration performance and elimination of the issue of potential environmental, health and safety concerns.