FeCr Slag Research Articles

Value Extraction from Ferrochrome Slag: A Thermochemical Equilibrium Calculation and Experimental Approach

The valorization of slag from the production of high-carbon ferrochrome is a challenge for ferrochrome producers. The recycling of high-carbon ferrochrome slag was explored through the smelting route to recover Fe–Si–Al–Cr alloys and reengineer the residual slag for alumina-enriched refractory material. In this research, the focus was to reduce the SiO2% and enrichment of Al2O3% in the final slag and recover the metallic value in the form of a complex alloy containing Fe, Si, Cr and Al. The manuscript consists of a thermochemical simulation of the smelting of FeCr slag followed by smelting experiments to optimize the process parameters such as temperature and the addition of coke, cast iron and alumina. An experimental investigation revealed that the maximum recovery of Si (57.4% recovery), Al in the alloy (20.56% recovery) and Al2O3 (85.78% recovery) in the slag was achieved at a charge mix consisting of 1000 g of FeCr slag, 300 g of alumina, 200 g of cast iron and 300 g of coke. The present study also demonstrated the usefulness of prior thermochemical calculations for smelting metallurgical wastes such as slag from high-carbon ferrochrome production for value creation and reutilization purposes.

Performance of limestone-calcined clay cement mortar incorporating high volume ferrochrome waste slag aggregate

This study set out to investigate the mechanical performance and physical properties of Limestone Calcined Clay Cement (LC3) – based mortar incorporating high dosage of ferrochrome (FeCr) slag aggregates. Green, sustainable and economical alternative binder has been prepared by replacing 60 wt% of the Ordinary Portland Cement (OPC) by a blend of limestone (LS) powder and metakaolin (MK) with LS: MK of 1:2 (wt%). The mortar specimens were produced with FeCr slag aggregate as a substitute for natural sand with different replacement ratios ranging from 25 % to 100 % with a stride of 25 wt%. The mini-slump flow test was conducted to assess the mortars behavior in the fresh state. Compressive and tensile strengths, capillary water absorption, leaching behavior and microstructure were investigated for the hardened mortars at 28 days of hydration. With the increase of FeCr replacement ratio, the water-binder ratio (w/b), compressive strength and tensile strength increased. OPC and LC3 mortars incorporating 100 % FeCr attained enhancements by about 71 and 63 % for compressive strength and 22 and 17 % for tensile strength respectively. The total replacement of sand with FeCr aggregate has decreased the water absorption of LC3 mortars by 11 %. The chromium and heavy metals leaching from LC3 mortar made with 100 % FeCr slag showed very low levels as a result of the improved microstructure in terms of compactness and interfacial transition zone (ITZ) tightness. Recycling of FeCr waste with utilization of green alternative binder in the production of mortar with improved mechanical performance is helpful in reducing the carbon footprint in the construction industry.

Development of Fe–Cr Slag mold for Al–Si Alloy (A356) Casting

Development of Fe–Cr Slag mold for Al–Si Alloy (A356) Casting

Elevated Temperature Wear Behavior of FeCr Slag Coating as an Alternative Coating Material for Caster Rolls

Elevated Temperature Wear Behavior of FeCr Slag Coating as an Alternative Coating Material for Caster Rolls

Microstructure Evaluation on Micro and Nano Slag Particles Reinforced AA7075 Composites

The research work was focused on utilization of solid industrial waste. In order to investigate the properties of Fe-Cr slag particulates strengthened AA7075 composites. In this paper addition of ferrochrome slag particles as reinforcement in AA 7075 alloy processed through stir casting technique. By varying size of ferrochrome slag particles were added to evaluate the size effects in the given alloy matrix. Prepared composites were subjected to heat treatment and evaluated for microstructure analysis. The results show that there is a uniform distribution of particles in the matrix and that there is a strong bond between the matrix and the reinforcement. Grain refinement in the alloy matrix is observed by inducing slag particles. Further nanocomposites show lower grain size values.

A Comparison in Metal Leachability Between Phosphoric Acid and Ascorbic Acid Stabilised Ferrochrome Slag

Ferrochrome (FeCr) slag was milled and stabilised with either ascorbic acid or phosphoric acid. The stabilised FeCr was then geopolymerised with 1 M KOH in order to obtain a monolith with at least an unconfined compressive strength of 1 MPa. The leachability of metals of the stabilised geopolymerised monoliths were then compared with the unstabilised geopolymerised monolith. Ascorbic acid stabilisation was only effective in Cr leaching reduction by 99.45% but was not effective on immobilisation of Fe, Zn, Ni and Mn. Ascorbic acid stabilisation was thought to proceed via the reduction of Cr(VI) species to insoluble Cr (III) species. Phosphate stabilisation reduced the leachability of Cr, Ni, Zn, Mn, Fe by 99.5%, 67.1%, 71.1%, 96.8% and 85.4% respectively. Phosphate stabilisation was thought to proceed via the formation of phosphate compounds of the metal ions in question. The phosphate stabilised FeCr slag leachability was within the allowable Toxicity Characteristic Leaching Procedure (TCLP) limits and its use is not detrimental to the environment.

Influence of mould materials on wear behavior of A356 alloy

This study aimed to determine the influence of mould materials on microstructure, mechanical properties and sliding wear behaviour of A356 alloy. Three separate moulds were made using ferrochrome slag, blast furnace slag and sand silica. The castings were produced separately on three moulds. All these samples were solutionized at 540OC for 8 h and aged at peak ageing condition (T6) 170OC 7 hrs. These were characterized for its microstructure, SDAS, hardness, and dry-sliding wear behaviour studies. Dry sliding experiments have been performed with a pin on a spinning disc. A pin size of 10 mm × length of 30 mm is selected. Metallographic results reveal casting made in Fe-Cr slag mould shown fine grain microstructure followed by GBF slag and sand mould. SDAS values of three mould castings were observed are Fe-Cr slag is 17, GBF slag is 31 and sand mould is 42. Improved hardness values were obtained for castings made in Fe-Cr slag moulds (122 VHN) followed by silica sand (114 VHN) and finally GBF slag (111 VHN). Thorough wear analysis was carried out on all these castings; results show samples of Fe-Cr slag moulds showed better wear resistance than either GBF slag or sand mould samples.

Microstructure and mechanical properties of oxide particulates reinforced PMCs

Studies are made to utilize the industrial solid waste of ferrochrome (Fe-Cr) slag as reinforcement to make particulate Polymer matrix composites (PMCs). Fe-Cr slag exhibits hard and high strength also consist multiple oxides of SiO₂, Al₂O 3 , MgO, Fe₂O 3 and Cr 2 O 3. Three different sizes (500 µm, 210 µm and 45 µm) were chosen as reinforcement in E glass fiber and epoxy resin matrix. Hand lay-up technique adopted to process all the PMCs. Metallography and mechanical properties evaluation has been done on all these PMCs. SEM studies reveals the homogeneity in the particles distribution and good interfacial bonding between matrix and reinforcements. Improved mechanical properties were observed for all the slag particulates PMCs. However, size of the slag particles also contributing the performance of the composites. Neither coarse (500 μm) nor very fine (45 μm) particles but optimum size of 210 μm slag particles is stimulating to increase the strength of the proposed composites.

Dry sliding wear behaviour of micro and nano high entropy Fe-Cr slag particulates reinforced AA 7075 composites

Abstract In metal matrix composites (MMCs), matrix materials are reinforced with various kinds of ceramic particulates to obtain optimum and tailor-made properties. The Fe-Cr slag consists of SiO2, Al2O3 and MgO with high entropy values. In the present investigation was conducted to synthesize the AA 7075 Fe-Cr slag particulate reinforced composites through stir casting technique. Studies were focused on particles size effects.For this two types of composites with reinforcement of micron (36 μm) and nano-size (68 nm) of 5% wt. of Fe-Cr slag, particulates were chosen. As cast and peak, aged samples were characterized for its metallurgical and mechanical properties. In the peak aged condition, the wear test is done.Wear morphology studies of base alloy and the composites have been carried out by scanning electron microscopy. Nanocomposite showed enhanced propertieswhich also exhibits better wear resistance in all the loads and longer sliding distances than micro composite or base alloy.

Up-Concentration of Chromium in Stainless Steel Slag and Ferrochromium Slags by Magnetic and Gravity Separation

Slags coming from stainless steel (SS) and ferrochromium (FeCr) production generally contain between 1 and 10% Cr, mostly present in entrapped metallic particles (Fe–Cr alloys) and in spinel structures. To recover Cr from these slags, magnetic and gravity separation techniques were tested for up-concentrating Cr in a fraction for further processing. In case of SS slag and low carbon (LC) FeCr slag a wet high intensity magnetic separation can up-concentrate Cr in the SS slag (fraction <150 µm) from 2.3 wt.% to almost 9 wt.% with a yield of 7 wt.%, and in the LC FeCr slag from 3.1 wt.% to 11 wt.% with a yield of 3 wt.%. Different behavior of Cr-containing spinel’s in the two slag types observed during magnetic separation can be explained by the presence or absence of Fe in the lattice of the Cr-containing spinel’s, which affects their magnetic susceptibility. The Cr content of the concentrates is low compared to chromium ores, indicating that additional processing steps are necessary for a recovery process. In the case of high carbon (HC) FeCr slag, a Cr up-concentration by a factor of more than three (from 9 wt.% to 28 wt.%) can be achieved on the as received slag, after a single dry low intensity magnetic separation step, due to the well-liberated Cr-rich compounds present in this slag. After gravity separation of the HC FeCr slag, a fraction with a Cr content close to high grade Cr ores (≥50% Cr2O3) can be obtained. This fraction represents 12 wt.% of the HC FeCr slag, and can probably be used directly in traditional smelting processes.

Ferrochrome slag and manufactured sand as fine aggregate replacement in concrete and mortar - A Brief Review

Background/Objective: To review on the river sand supplants particularly Manufactured sand (Msand) and Ferrochrome slag (FeCr slag) aggregate in concrete and mortar matrix. Methods: A study on FeCr slag as sand is skimpy and countable; so here they clustered together and discussed for its performance. Msand by its shape, texture, physiochemical characters, strength parameters and durability is much similar to river sand in a concrete matrix. FeCr slag shape and texture is almost similar but porous in nature and ingredients like MgO and Cr2O3can cause an effect on concrete. Msand based on various grades and mechanical strength is analysed. Findings: Msand strength behaviour is discussed in detail with reference to other authors which clearly states that Msand is ideal for fine aggregate replacement. Industrial waste FeCr slag is replaced instead of sand, which also behaves well until 40% to 50% replacement of sand at later ages of strength. Compressive strength, splitting tensile strength and flexural strength of these two materials are graphically depicted from a literature surveys of recent researches. Novelty: This study provides robust information about strength performance of Msand and FeCr slag with varying percentage ranges from 10% to 60% by weight. Keywords: Msand; ferrochrome slag; strength; compressive; splitting; flexural; river sand

Correlation between SDAS and mechanical properties of Al–Si alloy made in Sand and Slag moulds

Investigations have been carried out to evaluate the correlations between microstructure and mechanical properties of cast products made by Ferro chrome (Fe-Cr) slag and Granulated Blast Furnace (GBF) slag moulds in tune with silica sand moulds. A356 alloy castings were performed on all these three moulds with cylindrical pattern. The obtained castings were evaluated for its metallurgical and mechanical properties at as cast and peak ageing conditions. In all the castings, improved mechanical properties were noticed in peak ageing condition; further Fe-Cr slag cast products shows enhanced properties than either GBF slag or silica sand mould cast products. Fe-Cr slag mould cast products shows lower SDAS values than rest of the two moulds. Improved mechanical properties were observed with lower SDAS values. Correlations between individual and combined microstructural features with mechanical proprieties were established. Improved and reliable correlations were established by considering combined microstructural features.

Sustainable solidification of ferrochrome slag through geopolymerisation: a look at the effect of curing time, type of activator and liquid solid ratio

Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 10 M KOH and an L/S of 0.26 yielded a geopolymer with a UCS 13.0 MPa after 28 d of ambient temperature curing. A 0.125 wt KS:KOH addition yielded a geopolymer with a UCS of 14.7 MPa whilst a 1.25 wt KA:KOH addition yielded a geopolymer with a UCS of 24.5 MPa. The increase in strength was due to the formation of Calcium Silicate (Aluminate) hydrate. The aluminate activated FeCr slag geopolymer was the most competent of all geopolymers synthesised as it resulted in over 97% immobilisation of Fe, Zn, Mn, Ni and Cr. The 360-d static leachability tests for the aluminate activated geopolymer yielded a metal release rate lower than 90 mg mm− 2 of the geopolymer. The aluminate activated geopolymer also was resistant to changes in wet and dry cycles as it had a UCS reduction of 42% after 10 cycles whereas the pure FeCr slag geopolymer and the silicate activated geopolymer had a UCS reduction of 91 and 72% respectively after 10 cycles. The aluminate activated geopolymer met the minimum requirements for use as a paving brick for low traffic pavements. The study provides opportunities for sustainable use of FeCr slag with minimal environmental impact.

Comparison of dry sliding wear behavior of plasma sprayed FeCr slag coating with Cr2O3 and Al2O3‐13TiO2 coatings

AbstractThe microstructure and dry sliding wear performance of thermally sprayed FeCr slag coating were evaluated in comparison with those of commercially available Al2O3‐13TiO2 and Cr2O3 ceramic coating powders to assess the applicability of FeCr slag (FS) powder, fabricated from industrial waste, as a ceramic top‐coating material against wear. Ceramic top coats and underlying NiCoCrAlY bond coats were deposited on AISI 316L samples via atmospheric plasma spraying (APS), and their tribological properties were assessed using a ball‐on‐disc test rig at room temperature. As a result, FS coating exhibited the lowest worn volume, although it has the lowest surface hardness. Tribolayer formation was observed on the surface of the samples which were subjected to dry sliding wear tests. Delamination type wear is the dominant wear mechanism for Cr2O3 and FS coatings, whereas local spallation areas arising from plastic deformation were observed on the surface of Al2O3‐13TiO2 coatings. The results suggested the applicability of FS powder as a candidate ceramic top coating material against wear.

Ferrochromium slag as a protective coating material against oxidation for caster rolls

In this study, ferrochromium (FeCr) slag, which is available as an industrial waste, is proposed as a protective surface coating material particularly for protection of continuous casting rolls against oxidation. FeCr slag was successfully deposited with atmospheric plasma spray (APS) method. Before the coating process, FeCr slag powder prepared in the particle size range of 5-38 μm, was investigated using conventional characterization methods (XRD, SEM, TGA etc.). Thermal Barrier Coating (TBC) system was used as a basis for deposition processes. Accordingly, NiCoCrAlY (Amdry, −45 + 5 μm) was firstly deposited as metallic bond coat layer onto the surface of AISI 420 substrate, and then FeCr slag layer was deposited as the top coating layer. After the deposition of FeCr slag powder, the resulting coating layer was found to have low porosity with a homogeneous microstructure. The deposited FeCr slag coatings were subjected to isothermal oxidation tests at different temperatures and test durations for determination of their oxidation behavior and upper operating temperature limits. The results obtained from this study indicate that FeCr slag can be considered as an alternative protective coating material for caster rolls which are subjected to high temperatures up to 800°C.

Evaluation of the microstructure, secondary dendrite arm spacing, and mechanical properties of Al–Si alloy castings made in sand and Fe–Cr slag molds

The microstructure and mechanical properties of as-cast A356 (Al–Si) alloy castings were investigated. A356 alloy was cast into three different molds composed of sand, ferrochrome (Fe–Cr) slag, and a mixture of sand and Fe–Cr. A sodium silicate–CO2 process was used to make the necessary molds. Cylindrical-shaped castings were prepared. Cast products with no porosity and a good surface finish were achieved in all of the molds. These castings were evaluated for their metallography, secondary dendrite arm spacing (SDAS), and mechanical properties, including hardness, compression, tensile, and impact properties. Furthermore, the tensile and impact samples were analyzed by fractography. The results show that faster heat transfer in the Fe–Cr slag molds than in either the silica sand or mixed molds led to lower SDAS values with a refined microstructure in the products cast in Fe–Cr slag molds. Consistent and enhanced mechanical properties were observed in the slag mold products than in the castings obtained from either sand or mixed molds. The fracture surface of the slag mold castings shows a dimple fracture morphology with a transgranular fracture nature. However, the fracture surfaces of the sand mold castings display brittle fracture. In conclusion, products cast in Fe–Cr slag molds exhibit an improved surface finish and enhanced mechanical properties compared to those of products cast in sand and mixed molds.

Molding and casting behavior of ferro chrome slag as a mold material in ferrous and non-ferrous foundry industries

ABSTRACTIn the present investigation, efforts are made to use Ferro Chrome (Fe-Cr) slag as a mold material for the replacement of silica sand in the foundry industry. The sodium silicate-Fe–Si process is adopted for evaluating the same. The process parameters considered for this investigation are % of sodium silicate, % of Fe–Si powder as a binder, and mold setting time. A series of sand tests are carried out on sand, slag individually, and for various combinations of these two. Three types of molds are made with sand, slag individually, and combination of these two with 6% sodium silicate and 1.5% Fe–Si. Various ferrous and non-ferrous castings are performed on these newly developed slag molds. The results reveal that the Fe-Cr slag with mold permeability, compression, and shear strength is a suitable candidate for either partial or full replacement of silica sand. During casting neither fusing, dripping, nor collapse of the mold walls is observed in slag molds; this is true for both ferrous and non-ferrous castings. Castings with good surface finish and no surface defects are made by slag molds. Faster heat transfer in slag molds enable to obtain castings with enhanced metallurgical and mechanical properties.

Ferro Chrome Slag: An Alternative Mould Material in Ferrous and Non-ferrous Foundries

Various efforts are being made to use industrial wastes as an alternate moulding material in the foundry industry. Ferrochrome (Fe–Cr) slag has many of the same attributes of sand. Hence, in this paper, investigations were carried out on the suitability of Fe–Cr slag as mould material for either full or partial replacement of existing silica sand in the foundry industry. Owing to the superiority, sodium silicate–CO2 process was adopted for evaluating the same. The process parameters considered for this investigation were percentage of sodium silicate and CO2 gassing time. A series of sand tests were carried out on silica sand, Fe–Cr slag individually and various combinations of these two. Three types of moulds were made with Fe–Cr slag, silica sand individually and combination of these two with 8 %sodium silicate and 15 S CO2 gassing time. Various ferrous and non-ferrous castings were performed on these newly developed slag moulds. Results reveal that mould permeability, compression and shear strength of Fe–Cr slag are suitable candidates for either partial or full replacement of moulding sand. During casting, no burning, dripping nor collapse of the mould walls was observed in slag moulds; this is true for both ferrous and non-ferrous castings. Castings with good surface finish, no surface defects and without porosity were made by slag moulds. Slag moulds show faster solidification rates than sand moulds. Faster heat transfer in slag moulds enables obtain castings with enhanced metallurgical and mechanical properties like, hardness, compression and tensile with improved elongation.

In-situ chromium and vanadium recovery of landfilled ferrochromium and stainless steel slags

A novel heap leaching method was investigated for selective removal of chromium (Cr) and vanadium (V) from ferrochromium (FeCr) and stainless steel (SS) slags. In particular, alkaline oxidative heap leaching was simulated on lab-scale by batch and column leaching tests. The results show a selective leaching of Cr (11–19%) and V (7.0–7.5%) after 64days of column leaching, with a very low dissolution (<2.2% (FeCr slag) and <0.15% (SS slag)) of matrix elements (e.g. Al, Fe, Si, Mg, Ca), when NaOCl is applied as oxidation agent and NaOH as alkaline agent. Furthermore, the used leaching liquor is reactive for a longer period of time, indicating that circulation of leaching liquor could be possible. Finally, the experimental results were fed into a first-order model which predicts that Cr will continue to leach from the tested slags for 4–5years at a chosen infiltration rate of 73,000 l/(ym2).

High Carbon Ferro Chrome Slag – Alternative Mould Material for Foundry Industry

High silica sand is commonly used in foundry industry for sand moulds making. Various efforts are being made to use the industrial wastes as an alternate molding material in foundry to conserve the natural resources; and effective utilization of the industrial waste to sustain the industrialization. Ferro chrome (Fe-Cr) slag has many of the same attributes of the sand. In this paper investigations were carried out on comparative mould and casting properties of high silica sand and Fe-Cr slag for foundry applications. A series of sand tests were carried out on silica sand, Fe-Cr slag individually and various combinations of these two. The process parameters considered for this investigation were % of Sodium silicate, CO2 gassing time, and mould setting time. Two types of moulds were made with 100%Fe-Cr Slag and 100% Silica Sand individually with 8%Sodium Silicate and 15Seconds CO2 gassing time. AA2024 Aluminium alloy cylindrical castings were made through these two moulds; castings were investigated for its microstructure and hardness studies. Results reveal that standard samples with Fe-Cr slag can be prepared; these shows smooth surface finish and accurate dimensions on par with the sand samples. The mould permeability, compression and shear strength results showed Fe-Cr Slag will be a suitable candidate for either partial or full replacement of molding sand. Enhanced mould properties were observed for Fe-Cr slag than silica sand. Good surface finish castings with enhanced mechanical properties and fine grain microstructures were produced by Fe-Cr slag moulds.