A Study on the smelting process of low carbon steel scrap and sponge iron in medium frequency induction furnace for production of front bumper beams

MS1200 steel grade is now widely utilized in the automotive sector because it is a good solution for the current trend of vehicle chassis frame construction. This research presents a technology procedure for producing MS1200 steel grade from low carbon steel scrap and sponge iron – a product of MIREX Vietnam. The smelting using up to 30 % sponge iron briquettes combined with low carbon scrap, FeSi, FeMn, FeCr, FeTi,… was realized in a medium frequency induction furnace. The heat treatment for forged steel was performed to obtain required properties. The steel product has the following properties: tensile strength σb = 1280 MPa, yield strength σ0.2 = 990 MPa and impact toughness ak = 769 J/mm2, that meets the need of industrial use.

Zinc carbonate recovery from brass melting slag

Brass melting slag (20.38 wt.% Zn) was leached in sulfuric acid with concentration of (50 + 80) g/l H2SO4, leaching temperature of (30 + 60) °C for (30 + 120) min. The optimized conditions for 94.16% Zn extraction from brass melting slag were found as 70 g/l H2SO4, room temperature and 90 min. The leaching solution was purified by removal of Fe through Fe(OH)3 precipitation when adding ZnO to adjust pH value of 5. The solution was continuously cemented by Zn metal at 60 °C for 60 min to obtain Cu metal with high purity of 99 wt.% Cu. The purified solution with 37.64 g/l Zn was modified by Na2C03 to have pH value of about 6 and precipitation of ZnC03 (94.14 %).

Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min. The final reduced pellet, under microwave’s wattage of 90 % and firing time of 120 min., shows the only phases of metallic iron and fayalite according to the XRD resolution. The present work could provide a scientific understanding to illustrate iron ore/carbon composite pellet behavior during solid-state carbothermic reduction under a microwave-heating.

Effect of heat and surface pre-treatment processes on the nitriding ability of stainless steel SUS420

As-supplied SUS420 stainless steel was annealed at 880 °C for1 h and quenched (1040 °c, 30 min), followed by tempering at 530 °c for 1 h. The sample surface after tempering was polished with different roughness levels by mechanical grinding. Samples in the states of as-annealed, as-quenched and as-tempered samples as well as ground tempered ones with different surface roughness were gas nitrided with NH3 gas at 520 °c for 5 h. The microstructure and mechanical properties of SUS420 steel before and after the heat and surface treatments were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, and micro-hardness testing. The results show that if the natural oxide layer on the surface of the SUS420 samples was not removed, the nitriding process was very difficult or even imposible. The annealed steel gave the highest nitriding depth but low surface hardness. The samples after quenching and/or tempering had lower nitriding depth but higher hardness. The surface hardness of the as-supplied steel (333 HV) decreased with annealing (181 HV). After quenching, tempering, and gas nitriding, the values were 632, 560 and > 1000 HV, respectively. The samples after nitriding showed the appearance of fine CrN phase in the nitrided layer. The highest nitriding depth (125 pm) was obtained for the annealed samples, and subsequently decreased for the quenched samples and tempered samples. The lower the roughness of the sample, the higher is the hardness. The nitrided layer thickness tended to increase as the roughness decreased.

Design of metal casting mold for ADC 12 aluminium alloy with assistance of 20 kHz ultrasonic vibration

Metal mold casting is widely used in industry because of higher accuracy than sand casting and lower cost than diecasting. Metal mold casting can yield products with complex shapes and adjustable cooling rate. In this work, designing and fabrication of 20 kHz ultrasonic assisted mold casting using 20Cr steel are studied. Some major components such as motor, heater power, melting chamber are selected and calculated. Model for heating and pouring the ADC 12 alloy is designed. Samples with and without ultrasonic vibration are investigated using 3D laser scan.

Metallurgical properties of iron ore pellet when using lime powder instead of bentonite

This paper reported effects of lime powder and bentonite binder using in iron ore pelletization on metallurgical properties of pellets as green strength, compressive strength and degree of reduction. The investigated pellets contain 0, 1 and 2 mass % of lime powder and 2, 1 and 0 mass % of bentonite, respectively. Green balls were dried (105 °c for 24 hours) then heated at 1200 °c for 30 minutes. The reductibility of fired pellets was examined at different temperatures of 900, 1000 and 1100 °c with various holding time (45, 90 and 120 minutes). The results showed that the combination of 1 mass % of bentonite and 1 mass % of lime powder in the pellet gave the most apropriate metallurgical properties of pellets as green strength, porosity and degree of reduction. This material charging ratio can be recommended for application in manufacturing of the pellet.

The effect of die radius on thickness distribution of SS304 stainless steel sheet in deep drawing of cylindrical cup

Thickness distribution of deep drawing products has been studied in recent decades since it has a significant influence on the product quality. In this paper a numerical simulation with experimental verification was conducted to examine the influence of die radius on the thickness distribution of cilindrical cup in deep drawing for SS304 stainless steel. Thickness distribution of the cup was analyzed through the stress-strain state during deep drawing by Deform 3D software. The obtained results allow choosing a reasonable die radius to achieve more uniform wall thickness of the cup, that optimizes tool design and reduces manufacturing costs.

The effect of hot-press sintering temperature on density of heavy alloys WNi5Cu3

The effect of hot-press sintering temperature on density of tungsten heavy alloys is presented in this paper. The experiments were performed for the WNi5Cu3 samples of W-Ni-Cu heavy alloy system. The hot-press sintering temperature was ranged from 1300 to 1440 °c with a constant applied pressure of 40 MPa. Subsequently, the sintered samples were annealed at 1000 °c in acgon atmosphere during 3 h. The results showed that the obtained heavy alloys had maximum density of 17,427 g.cm3 and final particle size around (10 + 15) mm. The obtained results met the requirement for fabrication of small balanced parts for aeronautical industry.

Microstructure and properties of FeSi6,5 soft magnetic materials prepared by spark plasma sintering

In this paper, FeSi6,5 (6.5 wt.% Si) soft magnetic materials have been prepared Via a Spark Plasma Sintering (SPS) technique at difference sintering temperatures in the range of 1150 to 1300 °c for 15 min and a heating rate of 100 °c/min. The results show that the density of sintered samples increased with the rising sintering temperature resulted in the enhancement of Vickers hardness and magnetic properities otsintered samples. Hovvever, the highest magnetic saturation (Ms) of 209.6 emu/g and lowest coercivity (Hc) of 1.85 Oe were obtained for the SPSed sample at 1250 °c. In contrast, the sample sintered in vacuum at 1300 °c for 1h with heating rate of 20 °c/min shows the lower magnetic properties due to the lower density and high amount of pores in the structure. The results of research show that the spark plasma sintering route has a high potential of fast sintering Fe-Si soft magnetic materials and for application.

Research on causes of hot-tearing of AA3003 aluminum billet during DC casting process

AA3003 aluminum alloy made from raw scrap materials that have the advantage of economical use, but hottearing often occurs in the product billets of the direct chill casting process. This study used ANOVA analysis method for determination of chemical composition of AA3003 aluminum billet products to show influence of chemical composition on hot-tearing ability. The evaluation of the microstructure and chemical composition distribution of the elements by optical and scanning electron microscopes combined with energy dispersive spectroscopy showed the existence of impurities such as Cu, Zn, Fe, Pb exceeding the allowable limit in aluminum billets, especially at grain boundary, which can be the main reason for the hot-tearing of cast aluminum billets.