Welding as a fabrication process is one of the vital production routes for most manufacturing industries. Several factors are involved in the choice of welding process for specific applications;notable among these are...Welding as a fabrication process is one of the vital production routes for most manufacturing industries. Several factors are involved in the choice of welding process for specific applications;notable among these are compositional range of the material to be welded, the thickness of the base materials and type of current. Most metals oxidize rapidly in their molten state, and therefore, the weld area needs to be protected from atmospheric contamination;this is achieved in gas tungsten arc welding GTAW by a shielding gas (argon, helium, nitrogen). GTAW technique is one of the major processes for joining austenitic stainless steels (ASS) and ferritic stainless steel (FSS) fabrication. However, the microstructural change that occurs during welding and at weld joint is still a major challenge today as it affects both the corrosion resistance and the mechanical properties. Therefore, this present paper reviews past research findings on GTA welding of ASS and FSS. Results of the findings have confirmed that, depending on the amount of heat input, which can be controlled by welding parameters (welding speed, voltage and current), welded joints particularly, heat affected zones (HAZs) of both grades of steels can undergo mechanical failure and can be susceptible to corrosion attack if the joints are produced with a less ideal combination of welding parameters.展开更多
Process algorithm, numerical model and techno-economic assessment of charge calculation and furnace bath optimization for target alloy for induction furnace-based steelmaking is presented in this study. The developed ...Process algorithm, numerical model and techno-economic assessment of charge calculation and furnace bath optimization for target alloy for induction furnace-based steelmaking is presented in this study. The developed algorithm combines the make-to-order (MTO) and charge optimization planning (COP) of the steel melting shop in the production of target steel composition. Using a system-level approach, the unit operations involved in the melting process were analyzed with the purpose of initial charge calculation, prevailing alloy charge prediction and optimizing the sequence of melt chemistry modification. The model performance was established using real-time production data from a cast iron-based foundry with a 1- and 2-ton induction furnace capacity and a medium carbon-based foundry with a 10- and 15-ton induction furnace capacity. A simulation engine (CastMELT) was developed in Java IDE with a MySQL database for continuous interaction with changing process parameters to run the model for validation. The comparison between the model prediction and production results was analyzed for charge prediction, melt modification and ferroalloy optimization and possible cost savings. The model performance for elemental charge prediction and calculation purpose with respect to the charge input (at overall scrap meltdown) gave R-squared, Standard Error, Pearson correlation and Significance value of (0.934, 0.06, 0.97, 0.0003) for Carbon prediction, (0.962, 0.06, 0.98, 0.00009) for Silicon prediction, (0.999, 0.048, 0.999, 9E -11) for Manganese Prediction, and (0.997, 0.076, 0.999, 6E -7) for Chromium prediction respectively. Correlation analysis for melt modification (after charging of ferroalloy) using the model for after-alloying spark analysis compared with the target chemistry is at 99.82%. The results validate the suitability of the developed model as a functional system of induction furnace melting for combined charge calculation and melt optimization Techno-economic evaluation results showed that 0.98% - 0.25% ferroalloy saving per ton of melt is possible using the model. This brings about an annual production cost savings of 100,000 $/y in foundry A (medium carbon steel) and 20,000 $/y in foundry B (cast iron) on the use of different ferroalloy materials.展开更多
In this study, effects of sawdust, coal dust and iron filling additives at varied proportions on some selected properties of moulding sand were investigated. Consequently, cylindrical specimens with different percenta...In this study, effects of sawdust, coal dust and iron filling additives at varied proportions on some selected properties of moulding sand were investigated. Consequently, cylindrical specimens with different percentages of additives were prepared based on standard procedures. The prepared specimens were subjected to basic moulding sand testing including moisture content, bulk density, porosity, permeability, green compression strength and green shear strength using standard methods and equipment. From the obtained test results, all the experimental additives were found to improve the selected moulding properties of the base (silica) sand. Moulding sand specimen with sawdust additive revealed a relatively better compaction as compared to moulding sand specimens with coal dust and iron filling additives respectively. The moisture absorbing strength of the moulds was also found to increase with increasing percentage of sawdust. Addition of coal dust to the moulding sand was found to improve sand porosity and permeability which results in less casting defects, and due to improved moisture absorbing strength of sawdust, moulding sand specimens that contained sawdust were equally found to exhibit good compaction with maximum green compressive strength of 108.99 kPa. Also, the combination of 25% sawdust, coal dust and iron filling in the moulding sand was found to produce mould with optimum green shear strength value of 54.49 kPa.展开更多
Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by impr...Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by improper choice of electrode. Therefore, in this study, effects of different types of electrode on the microstructure and tensile property of type 304 L austenitic stainless steel heat-affected zone (HAZ) were studied. Chemical composition of the as-received sample was determined. A number of samples were cut from the as-received sample. Afterwards, two half were joined together with 308 L, 312 L and 316 electrodes at a controlled welding speed, current and voltage of 4.6 mm/s, 160 A and 30 V to produce a constant heat input of 626.09 J/mm. An automatic SAW machine with Model Type: DX3-301, and Frequency: 50 Hz was used. And based on ASTM standard, tensile and hardness samples were prepared from the as-received and HAZs. Tensile and hardness measurements were made. Also, specimens for microscopy studies were prepared from the HAZ and as-received samples. From the results, microstructures of the HAZs revealed varied volume fraction of austenite and ferrite phases and grain sizes, and at austenite and ferrite grain boundaries, chromium carbide formation and precipitation were observed. The weld joint produced with 308 L electrode revealed optimum UTS value and YS value of 475 and 325 respectively. While weld joint produced with 316 L electrode has superior ductility of value 41%. Irrespective of the types of electrode used, the as-received sample revealed superior tensile properties over the weld joints. Also, optimum hardness value of 45.7 HRA was obtained with 308 L. Hardness value of the as-received sample was higher than that of HAZ samples.展开更多
Solidification process of grey cast iron largely determines the resultant carbon precipitates in form of graphite or carbides. Microstructure and hardness properties of grey iron were therefore studied. Aggregate scra...Solidification process of grey cast iron largely determines the resultant carbon precipitates in form of graphite or carbides. Microstructure and hardness properties of grey iron were therefore studied. Aggregate scraps were melted with varying inoculants composition of 0.1 wt%, 0.2 wt% and 0.3 wt%. Cast produced was shaken out of the mould at various timing. Microstructures of the samples were determined and analyzed. Hardness properties were equally evaluated. It was observed that the occurrence of carbides was more with 0.25 hrs shakeout time than other varying timing. Increasing shakeout time was found to decrease hardness and increase the carbide grain size. When the ferrosilicon content increases, there is a gradual decrease in the hardness properties from 59.6 HRC to 53.2 HRC for 0.25 hrs shakeout time cast sample. Similar decreases were observed for various timing analyzed.展开更多
This research was conducted to formulate a refractory lining recipe for lining diesel fired rotary furnace from locally sourced kaolin, using locally sourced potter’s clay as binder. Six samples (A-F) of kaolin clay ...This research was conducted to formulate a refractory lining recipe for lining diesel fired rotary furnace from locally sourced kaolin, using locally sourced potter’s clay as binder. Six samples (A-F) of kaolin clay mined locally from Apata II area, Ondo road, in Ile-Ife,Nigeria, were roasted at 1200oC held for 8 hours, mixed with different percentages of raw kaolin and appropriately made into briquettes using potter’s clay of good plasticity as binder. The samples were tested for various refractory properties. The result showed that sample mixes A (100% chamotte), B (80% chamotte, 20% rawkaolin) and C (60% chamotte, 40% raw kaolin) are considered to have good properties. However, the optimum material-mix for the refractory bricks lining, with particular reference to the highest thermal shock resistance was found to be 80% chamotte mixed with 20% raw kaolin.展开更多
Effect of heat treatment on the corrosion of welded low-carbon steel in 0.3 M and 0.5 M of hydrochloric acid and sodium chloride environments at ambient temperature (25oC) has been investigated. Arc welded low-carbon ...Effect of heat treatment on the corrosion of welded low-carbon steel in 0.3 M and 0.5 M of hydrochloric acid and sodium chloride environments at ambient temperature (25oC) has been investigated. Arc welded low-carbon steel sample of known composition were subjected to the corrosion reagents for 21 days (504 hours). pH and weight loss values were taken at interval of 3 days. Thereafter, weight loss method was used to measure therate of corrosion attack on the heat treated samples at ambient temperature. Results obtained showed that at low concentration, the annealed sample exhibits better corrosion characteristic as compared to the normalized and quenched samples. However, at higher concentration the normalized sample exercised better service performance over the annealed and quenched samples. Thequenched sample was found to have relatively low corrosion performance over the annealed and normalized samples at both low and high concentrations of the media.展开更多
文摘Welding as a fabrication process is one of the vital production routes for most manufacturing industries. Several factors are involved in the choice of welding process for specific applications;notable among these are compositional range of the material to be welded, the thickness of the base materials and type of current. Most metals oxidize rapidly in their molten state, and therefore, the weld area needs to be protected from atmospheric contamination;this is achieved in gas tungsten arc welding GTAW by a shielding gas (argon, helium, nitrogen). GTAW technique is one of the major processes for joining austenitic stainless steels (ASS) and ferritic stainless steel (FSS) fabrication. However, the microstructural change that occurs during welding and at weld joint is still a major challenge today as it affects both the corrosion resistance and the mechanical properties. Therefore, this present paper reviews past research findings on GTA welding of ASS and FSS. Results of the findings have confirmed that, depending on the amount of heat input, which can be controlled by welding parameters (welding speed, voltage and current), welded joints particularly, heat affected zones (HAZs) of both grades of steels can undergo mechanical failure and can be susceptible to corrosion attack if the joints are produced with a less ideal combination of welding parameters.
文摘Process algorithm, numerical model and techno-economic assessment of charge calculation and furnace bath optimization for target alloy for induction furnace-based steelmaking is presented in this study. The developed algorithm combines the make-to-order (MTO) and charge optimization planning (COP) of the steel melting shop in the production of target steel composition. Using a system-level approach, the unit operations involved in the melting process were analyzed with the purpose of initial charge calculation, prevailing alloy charge prediction and optimizing the sequence of melt chemistry modification. The model performance was established using real-time production data from a cast iron-based foundry with a 1- and 2-ton induction furnace capacity and a medium carbon-based foundry with a 10- and 15-ton induction furnace capacity. A simulation engine (CastMELT) was developed in Java IDE with a MySQL database for continuous interaction with changing process parameters to run the model for validation. The comparison between the model prediction and production results was analyzed for charge prediction, melt modification and ferroalloy optimization and possible cost savings. The model performance for elemental charge prediction and calculation purpose with respect to the charge input (at overall scrap meltdown) gave R-squared, Standard Error, Pearson correlation and Significance value of (0.934, 0.06, 0.97, 0.0003) for Carbon prediction, (0.962, 0.06, 0.98, 0.00009) for Silicon prediction, (0.999, 0.048, 0.999, 9E -11) for Manganese Prediction, and (0.997, 0.076, 0.999, 6E -7) for Chromium prediction respectively. Correlation analysis for melt modification (after charging of ferroalloy) using the model for after-alloying spark analysis compared with the target chemistry is at 99.82%. The results validate the suitability of the developed model as a functional system of induction furnace melting for combined charge calculation and melt optimization Techno-economic evaluation results showed that 0.98% - 0.25% ferroalloy saving per ton of melt is possible using the model. This brings about an annual production cost savings of 100,000 $/y in foundry A (medium carbon steel) and 20,000 $/y in foundry B (cast iron) on the use of different ferroalloy materials.
文摘In this study, effects of sawdust, coal dust and iron filling additives at varied proportions on some selected properties of moulding sand were investigated. Consequently, cylindrical specimens with different percentages of additives were prepared based on standard procedures. The prepared specimens were subjected to basic moulding sand testing including moisture content, bulk density, porosity, permeability, green compression strength and green shear strength using standard methods and equipment. From the obtained test results, all the experimental additives were found to improve the selected moulding properties of the base (silica) sand. Moulding sand specimen with sawdust additive revealed a relatively better compaction as compared to moulding sand specimens with coal dust and iron filling additives respectively. The moisture absorbing strength of the moulds was also found to increase with increasing percentage of sawdust. Addition of coal dust to the moulding sand was found to improve sand porosity and permeability which results in less casting defects, and due to improved moisture absorbing strength of sawdust, moulding sand specimens that contained sawdust were equally found to exhibit good compaction with maximum green compressive strength of 108.99 kPa. Also, the combination of 25% sawdust, coal dust and iron filling in the moulding sand was found to produce mould with optimum green shear strength value of 54.49 kPa.
文摘Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by improper choice of electrode. Therefore, in this study, effects of different types of electrode on the microstructure and tensile property of type 304 L austenitic stainless steel heat-affected zone (HAZ) were studied. Chemical composition of the as-received sample was determined. A number of samples were cut from the as-received sample. Afterwards, two half were joined together with 308 L, 312 L and 316 electrodes at a controlled welding speed, current and voltage of 4.6 mm/s, 160 A and 30 V to produce a constant heat input of 626.09 J/mm. An automatic SAW machine with Model Type: DX3-301, and Frequency: 50 Hz was used. And based on ASTM standard, tensile and hardness samples were prepared from the as-received and HAZs. Tensile and hardness measurements were made. Also, specimens for microscopy studies were prepared from the HAZ and as-received samples. From the results, microstructures of the HAZs revealed varied volume fraction of austenite and ferrite phases and grain sizes, and at austenite and ferrite grain boundaries, chromium carbide formation and precipitation were observed. The weld joint produced with 308 L electrode revealed optimum UTS value and YS value of 475 and 325 respectively. While weld joint produced with 316 L electrode has superior ductility of value 41%. Irrespective of the types of electrode used, the as-received sample revealed superior tensile properties over the weld joints. Also, optimum hardness value of 45.7 HRA was obtained with 308 L. Hardness value of the as-received sample was higher than that of HAZ samples.
文摘Solidification process of grey cast iron largely determines the resultant carbon precipitates in form of graphite or carbides. Microstructure and hardness properties of grey iron were therefore studied. Aggregate scraps were melted with varying inoculants composition of 0.1 wt%, 0.2 wt% and 0.3 wt%. Cast produced was shaken out of the mould at various timing. Microstructures of the samples were determined and analyzed. Hardness properties were equally evaluated. It was observed that the occurrence of carbides was more with 0.25 hrs shakeout time than other varying timing. Increasing shakeout time was found to decrease hardness and increase the carbide grain size. When the ferrosilicon content increases, there is a gradual decrease in the hardness properties from 59.6 HRC to 53.2 HRC for 0.25 hrs shakeout time cast sample. Similar decreases were observed for various timing analyzed.
文摘This research was conducted to formulate a refractory lining recipe for lining diesel fired rotary furnace from locally sourced kaolin, using locally sourced potter’s clay as binder. Six samples (A-F) of kaolin clay mined locally from Apata II area, Ondo road, in Ile-Ife,Nigeria, were roasted at 1200oC held for 8 hours, mixed with different percentages of raw kaolin and appropriately made into briquettes using potter’s clay of good plasticity as binder. The samples were tested for various refractory properties. The result showed that sample mixes A (100% chamotte), B (80% chamotte, 20% rawkaolin) and C (60% chamotte, 40% raw kaolin) are considered to have good properties. However, the optimum material-mix for the refractory bricks lining, with particular reference to the highest thermal shock resistance was found to be 80% chamotte mixed with 20% raw kaolin.
文摘Effect of heat treatment on the corrosion of welded low-carbon steel in 0.3 M and 0.5 M of hydrochloric acid and sodium chloride environments at ambient temperature (25oC) has been investigated. Arc welded low-carbon steel sample of known composition were subjected to the corrosion reagents for 21 days (504 hours). pH and weight loss values were taken at interval of 3 days. Thereafter, weight loss method was used to measure therate of corrosion attack on the heat treated samples at ambient temperature. Results obtained showed that at low concentration, the annealed sample exhibits better corrosion characteristic as compared to the normalized and quenched samples. However, at higher concentration the normalized sample exercised better service performance over the annealed and quenched samples. Thequenched sample was found to have relatively low corrosion performance over the annealed and normalized samples at both low and high concentrations of the media.
