The frequent defects of the metal parts, such as non-fully melting, thermal strain, and balling, which are produced by selective laser melting （SLM） that is a novel method of one-step manufacturing, are analyzed the...The frequent defects of the metal parts, such as non-fully melting, thermal strain, and balling, which are produced by selective laser melting （SLM） that is a novel method of one-step manufacturing, are analyzed theoretically and experimentally. The processing parameters significantly affect the quality of the final parts, and simultaneously, the appropriate laser mode and the special scanning strategy assure a satisfying quality of the final parts. The SLM experiment is carried out using Cu-based powder. The metal part is divided into several scanned regions, each of which is scanned twice at the cross direction with different scanning speeds. The microstructure is analyzed on microscope. The results show that the part is metallurgically bonded entity with a relative density of 95%, and the microstructure is composed of equiaxial crystal and dendritic crystal whose distributions are mainly decided by the scanning strategy.展开更多
Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing ju...Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing jujube wood at 673 K for 2 h and was used as reducing agent. The results of the direct reduction tests show that at a tem- perature of 1373 K, a char mixing ratio of 0.8, and a reduction time of 10-25 min, the briquettes reached a metal- lization degree of 80% -84% and a residual carbon content of 0.13 -1.98 mass%. Phosphorus remained in the gangue as calcium phosphate after reduction. The results of the melting separation tests show that residual carbon in reduced briquette negatively affects the phosphorus content （W[p]） in hot metal. When the reduced briquettes ob- tained under the aforementioned conditions were used for melting separation, hot metal suitable for basic oxygen steelmaking （w[p]〈0.4 mass%） could not be obtained from metallic briquettes with a residual carbon content more than 1.0 mass~. In contrast, it could be obtained from metallic briquettes with residual carbon content less than 0.35 mass% by mixing with 2%-4% Na2CO3.展开更多
This paper studied the changing principles of carbon content in direct reduction iron (DRI) and liquid iron in the COREX melting gasifier. Under the normal working conditions of experimental equipment, liquid nitrogen...This paper studied the changing principles of carbon content in direct reduction iron (DRI) and liquid iron in the COREX melting gasifier. Under the normal working conditions of experimental equipment, liquid nitrogen was poured into the melting gasifier from its tuyere to cool down quickly. And then seven cross sections were made to study the carburization reaction and its characteristics of the solid iron and the liquid iron, and also the reaction of carbon between the slag and the metal. According to the results, the influences of the thickness of the semi-coke layer and the temperature on the carbon content of liquid iron in the COREX melting gasifier were confirmed.展开更多
文摘The frequent defects of the metal parts, such as non-fully melting, thermal strain, and balling, which are produced by selective laser melting （SLM） that is a novel method of one-step manufacturing, are analyzed theoretically and experimentally. The processing parameters significantly affect the quality of the final parts, and simultaneously, the appropriate laser mode and the special scanning strategy assure a satisfying quality of the final parts. The SLM experiment is carried out using Cu-based powder. The metal part is divided into several scanned regions, each of which is scanned twice at the cross direction with different scanning speeds. The microstructure is analyzed on microscope. The results show that the part is metallurgically bonded entity with a relative density of 95%, and the microstructure is composed of equiaxial crystal and dendritic crystal whose distributions are mainly decided by the scanning strategy.
基金Item Sponsored by National Natural Science Foundation of China(51144010)
文摘Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing jujube wood at 673 K for 2 h and was used as reducing agent. The results of the direct reduction tests show that at a tem- perature of 1373 K, a char mixing ratio of 0.8, and a reduction time of 10-25 min, the briquettes reached a metal- lization degree of 80% -84% and a residual carbon content of 0.13 -1.98 mass%. Phosphorus remained in the gangue as calcium phosphate after reduction. The results of the melting separation tests show that residual carbon in reduced briquette negatively affects the phosphorus content （W[p]） in hot metal. When the reduced briquettes ob- tained under the aforementioned conditions were used for melting separation, hot metal suitable for basic oxygen steelmaking （w[p]〈0.4 mass%） could not be obtained from metallic briquettes with a residual carbon content more than 1.0 mass~. In contrast, it could be obtained from metallic briquettes with residual carbon content less than 0.35 mass% by mixing with 2%-4% Na2CO3.
文摘This paper studied the changing principles of carbon content in direct reduction iron (DRI) and liquid iron in the COREX melting gasifier. Under the normal working conditions of experimental equipment, liquid nitrogen was poured into the melting gasifier from its tuyere to cool down quickly. And then seven cross sections were made to study the carburization reaction and its characteristics of the solid iron and the liquid iron, and also the reaction of carbon between the slag and the metal. According to the results, the influences of the thickness of the semi-coke layer and the temperature on the carbon content of liquid iron in the COREX melting gasifier were confirmed.
