Production of high-add value products from low grade ores and metallurgical wastes
2024 Metallurgical Conference, Northeastern University, Shenyang, China , 2024
In the recent years, the metallurgical industry faced many challenges on different levels that in... more In the recent years, the metallurgical industry faced many challenges on different levels that include but not limited to: scarce of high grade ores, pollutions, energy consumption, accumulation of huge amount of wastes and the large consumption of resources. To face these challenges, Steel Technology Department at CMRDI, Egypt innovated technologies to produce high grade silicon manganese from local low grade abundant ores and to produce high qualities iron from mill scale wastes produced from the hot rolling of steel.
Concerning low-grade manganese abundant ores, as a result of the depletion of high-grade manganese reserves, it has become necessary to consider the exploitation of low-grade manganese ores. The main problem of low-grade manganese ore is the low Mn/Fe ratio, which makes it unfit for the production of manganese ferroalloys. In this work, an innovative technology that has been developed for the smelting of Egyptian low-grade manganese ore to produce low-manganese pig iron and high-manganese slag is presented through selective reduction technique. The product slag was blended with medium-manganese ore and smelted in an electric submerged arc furnace, in the presence of coke and the fluxing agent, to produce silicomanganese alloy. The influence of reducing agent ratio, charge basicity, and charge Mn/Si ratio on the smelting process was investigated. The optimum conditions were found to be a coke ratio of, 1.35, Mn/Si ratio of 2.0, and charge basicity of 2.5. The silicomanganese alloy produced under these conditions satisfies the specifications for Si16Mn63 and Si17Mn65. The experimental results were applied on a pilot scale, producing a silicomanganese alloy with a chemical composition close to that of the standard specifications.
Concerning mill scale waste; crude steel production has increased significantly with higher growth rate in the past years. With the increase in steel production, large amounts of waste materials (slag, dust and mill scale) are produced. Mill scale is one of these waste materials produced during preheating of steel slabs and billets before hot rolling in steel plants in about 20-40 kg/ ton of steel. Mill scale is mainly iron oxides (iron-rich sources). On the other hand, high purity pig iron is used in foundries production of ductile cast iron forming 25% of input materials. An innovative recycling process of mill scale to produce high purity pig iron was developed. Different heats of smelting process were carried out using different reductants and fluxing materials to economically produce high purity pig iron with the highest recovery and minimum Mn, P and S contents. Different blends were applied using different reductants as coke, graphite and anthracite with different fixed carbon, sulphur, ash, volatile matter and moisture contents. Limestone and fluorspar mixture were used as fluxing and slaging materials in different percentage to adjust the basicity and physical properties of slag that control the reduction as well as the refining process. A high purity pig iron could be obtained with chemical composition conforming the requirements to be used in the production of ductile cast iron.
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Papers by Taha Mattar
This work examines tool steel grades and their grading systems, emphasizing the metallurgical concepts that influence their properties, particularly in production and heat treatment. AISI M2 high-speed tool steel is highlighted for its versatility in high-speed applications that require hardness, toughness, and wear resistance. Achieving optimal properties involves precise control of cleanliness, structure, and microstructure during heat treatment, which is essential for AISI M2 tool steel.
AISI M2 high-speed tool steel was produced through induction melting and electroslag refining (ESR) to reduce nonmetallic inclusions. Various characterization experiments were conducted to investigate phase transformation, microstructure, and dilatation. The study utilized JMatPro software for phase equilibria and solidification analysis. Precipitated carbides were examined using optical microscopy and X-ray diffraction, identified through wavelength dispersive X-ray, scanning electron microscopy, and energy-dispersive X-ray techniques. Image analysis with Image J software assessed the count and size distribution of precipitated carbides and inclusions. The critical transformation temperature was measured using dilatometry.
Concerning low-grade manganese abundant ores, as a result of the depletion of high-grade manganese reserves, it has become necessary to consider the exploitation of low-grade manganese ores. The main problem of low-grade manganese ore is the low Mn/Fe ratio, which makes it unfit for the production of manganese ferroalloys. In this work, an innovative technology that has been developed for the smelting of Egyptian low-grade manganese ore to produce low-manganese pig iron and high-manganese slag is presented through selective reduction technique. The product slag was blended with medium-manganese ore and smelted in an electric submerged arc furnace, in the presence of coke and the fluxing agent, to produce silicomanganese alloy. The influence of reducing agent ratio, charge basicity, and charge Mn/Si ratio on the smelting process was investigated. The optimum conditions were found to be a coke ratio of, 1.35, Mn/Si ratio of 2.0, and charge basicity of 2.5. The silicomanganese alloy produced under these conditions satisfies the specifications for Si16Mn63 and Si17Mn65. The experimental results were applied on a pilot scale, producing a silicomanganese alloy with a chemical composition close to that of the standard specifications.
Concerning mill scale waste; crude steel production has increased significantly with higher growth rate in the past years. With the increase in steel production, large amounts of waste materials (slag, dust and mill scale) are produced. Mill scale is one of these waste materials produced during preheating of steel slabs and billets before hot rolling in steel plants in about 20-40 kg/ ton of steel. Mill scale is mainly iron oxides (iron-rich sources). On the other hand, high purity pig iron is used in foundries production of ductile cast iron forming 25% of input materials. An innovative recycling process of mill scale to produce high purity pig iron was developed. Different heats of smelting process were carried out using different reductants and fluxing materials to economically produce high purity pig iron with the highest recovery and minimum Mn, P and S contents. Different blends were applied using different reductants as coke, graphite and anthracite with different fixed carbon, sulphur, ash, volatile matter and moisture contents. Limestone and fluorspar mixture were used as fluxing and slaging materials in different percentage to adjust the basicity and physical properties of slag that control the reduction as well as the refining process. A high purity pig iron could be obtained with chemical composition conforming the requirements to be used in the production of ductile cast iron.
These defects may be casting process related (such as star cracks, longitudinal cracks, transverse cracks, oscillation marks and gas porosity (pin, blow or open holes)); casting machine condition related (such as groove, marks, ridge marks and pit marks). The surface defects are classified into light, medium and heavy based on the severity, frequency, depth, length and width.
Surface quality problems and surface defects can result from multiple sources pertaining to unfavorable alloy chemistry, irregular casting practices and, improper processing. The evolution of these defects may occur during initial steelmaking stages, develop during the subsequent rolling operations.
The primary control problem in continuous casting is the level of steel in the mold. The level of steel in the mold should remain as constant as possible. The mold level control problem is the main problem that is addressed by control system researchers in the field of continuous casting.
Another important factor is the cleanliness of the steel as there can be oxidation of steel with oxygen from air or refractories, pickup of exogenous inclusions from ladle and tundish refractories and mold powders, poor control of fluid flow in the tundish so that inclusions do not float out and/ or poor mold powder and startup/shutdown procedures, causing break-outs.
Cracks occurring in, or on the steel such as surface cracks which are a serious quality problem because the cracks oxidize and give rise to oxide-rich seams in the rolled product or, to an even greater extent, cause the strand to be scrapped due to extremely deep longitudinal cracks, and internal cracks which can also be a problem particularly if during rolling, they do not close, leaving voids in the steel product.
There is also macro-segregation, when there are higher concentrations of certain elements in certain regions of the strand, causing cracks during rolling. Finally, cross sectional or transverse shape defects where deviations from the specified shape due to nonhomogeneous cooling sin the mold are recognized and require excessive reworking.
From the different research work and industrial investigations concerning the different defects in steel products it could be concluded that; mold level linked to defects in longitudinal cracking and inclusions, the mold level control is the most important single factor that contributes to surface defects and mold powder and mold friction are very closely related and are difficult to measure on-line, as is the taper of the mold; in other words every considered defect is linked to some variable in the mold.
It was concluded also that strand temperature plays a role in all the defects except inclusions and stop marks, temperature is a very valuable variable to use in any type of defect predictor.
Among the outcomes it was found that the steel composition is a factor which does not change dynamically during casting while measurement of inclusion outflow in the tundish is also difficult to quantify on-line and superheat is generally not measured at regular intervals.
Also it was found that iron oxide-containing slivers are a common defect in hot rolled steel products, and their origins could be many, surface and subsurface defects such as various cracks and mechanical scratches generated in the continuously cast slabs usually led to iron oxide-type sliver in rolled coils, star cracks on the slab surface resulted in characteristic U-type multiple-line slivers in rolled product, longitudinal cracks appeared as discontinuous long sliver lines in the rolling direction, deep groove marks caused long slivers extending throughout the length of the coil and the types and severities of oscillation marks did not cause any surface defect in rolled products.
high-strength steels (UHSSs): Steel A (fully martensitic) and Steel B (martensitic–bainitic). The in-
vestigation focused on the fatigue behaviour, damage mechanisms, and failure modes across differ-
ent microstructures. Fatigue strength was determined through fully reversed tension–compression
stress-controlled fatigue tests. Microstructural evolution, fracture surface characteristics, and crack-
initiation mechanisms were investigated using laser scanning confocal microscopy and scanning
electron microscopy. Microindentation hardness (HIT) tests were conducted to examine the cyclic
hardening and softening of the steels. The experimental results revealed that Steel A exhibited su-
perior fatigue resistance compared to Steel B, with fatigue limits of 550 and 500 MPa, respectively.
Fracture surface analysis identified non-metallic inclusions (NMIs) comprising the complex MnO-
SiO2 as critical sites for crack initiation during cyclic loading in both steels. The HIT results after
fatigue indicated significant cyclic softening for Steel A, with HIT values decreasing from 7.7 ± 0.36
to 5.66 ± 0.26 GPa. In contrast, Steel B exhibited slight cyclic hardening, with HIT values increasing
from 5.24 ± 0.23 to 5.41 ± 0.31 GPa. Furthermore, the martensitic steel demonstrated superior yield
and tensile strengths of 1145 and 1870 MPa, respectively. Analysis of the fatigue behaviour revealed
the superiorfatigue resistance of martensitic steel. The complex morphology and shape of the NMIs,
examined using the 3D microstructure characterisation technique, demonstrated their role as stress
concentrators, leading to localised plastic deformation and crack initiation.