Effect of melt-to-solid volume ratio and preheating temperature on Mg/Al bimetals interface by centrifugal casting

Compound casting is an efficient method for bonding dissimilar metals,in which a dramatic reaction can occur between the melt and solid.The centrifugal casting process,a type of compound casting,was applied to cast Al/Mg dissimilar bimetals.Magnesium melt was poured at 700 °C,with melt-to-solid volume ratios(Vm/Vs) of 1.5 and 3,into a preheated hollow aluminum cylinder.The preheating temperatures of the solid part were 320,400,and 450 °C,and the constant rotational speed was 1,600 rpm.The cast parts were kept inside the casting machine until reaching the cooling temperature of 150 °C.The result showed that an increase in preheating temperature from 320 to 450 °C led to an enhanced reaction layer thickness.In addition,an increase in the Vm/Vs from 1.5 to 3 resulted in raising the interface thickness from 1.2 to 1.8 mm.Moreover,the interface was not continuously formed when a Vm/Vs of 3 was selected.In this case,the force of contraction overcame the resultant acting force on the interface.An interface formed at the volume ratio of 1.5 was examined using scanning electron microscopy(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS),and the results demonstrated the formation of Al_(3)Mg_(2),Al_(12)Mg_(17) and(δ+Al_(12)Mg_(17)) eutectic structures in the interface.

Effect of groove angle and preheating temperature on temperature profile and fluid velocity in weld pool

The three dimensiotud transient weld pool dynamics are numerically analyzed ,for Forcearc welding, which is a new gas metal arc welding technology to get deep fusion penetration with smaller angle sf V groove to enhance welding efficiency significantly. The influence of groove angle and preheatin,g temperature on heat and .fluid .flow is studied and compared to get an optimal welding parameter. Good agreement is shown between the predicted and experimental results, such as weld bead cross-section and thermal cycles. It can he seen that an apprpriate groove angle could be used to replace high preheating temperature to get inproced penetration and thermal cycles.

The Influence of Preheat Temperature of Steel Plate on Steel-mushy Cu-graphite Bonding

The pressing bonding of steel plate to QTi3.5-3.5 graphite slurry was conducted. Under the conditions of 530 ℃ for the preheat temperature of dies, 45% for the solid fraction of QTi3.5- 3.5 graphite slurry, 50 MPa for the pressure and 2 min for the pressing time, the relationship between the preheat temperature of steel plate and interfacial mechanical property of bonding plate was studied. The results show that when the preheat temperature of steel plate is lower titan 618 ℃ , the interfacial shear strength of bonding plate increases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is higher than 618 ℃ , the interfacial shear strength decreases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is 618 ℃ , the highest interfacial shear strength of bonding plate of 127.8 MPa can be got.

THE DEVELOPMENT OF MINOR-CALIBER COMPOSITE PIPES ON CORROSIVE WEAR-RESISTANT

The ceramic lined pipes had been produced by gravitational separation SHS method and influential factors on combustion synthesis was investigated.The experimental results showed that the ceramic lined pipes had been produced easily under condition that selecting pipes well distributed on the wall thickness ,proper preheating temperature and appropriate additive.

Mechanism of Surface Depression on Foam Glass

The mechanism of the surface depression of the foam glass was studied. A method of powder sintering with plate glass as the raw material and carbon black as the foaming agent was adopted to investigate the influences of foaming temperature, soaking time, moisture content in the release agent, and flame preheating temperature on the surface depression of a foam glass blank. The results indicated that insufficient cooling rate and rapid foaming process that could not react synergistically with the surface tension and viscosity of the glass melt aroused the mismatching between the glass melt and the expansion or contraction of gas, resulting in upper surface depression of foam glass. Besides, the batch carbon black at high temperature reacted with residual water in advance to generate large amounts of gas and form the air space which could expand inside, leading to lower surface depression of foam glass.

Effect of Preheating Temperature on Surface Cracking of High Nitrogen CrMn Austenitic Stainless Steel

18Mn18Cr0.5N steel specimens were preheated at the temperatures from 1100 to 1250°C for 5 min,and then cooled to 950°C and compressed.The cracking behaviors were investigated using optical microscopy and scanning electron microscopy.The results showed that the hot workability of 18Mn18Cr0.5N steel gradually decreased with increasing preheating temperature between 1100 and 1200°C,and quickly deteriorated up to 1250°C.Above 1200°C,delta ferrite particles appeared in 18Mn18Cr0.5N steel,promoted cavity coalescence on grain boundary,and accelerated surface crack formation during the hot working process.

Analysis of Porosity and Preheating Temperature on the Decomposition and Combustion Characteristics within 5 N Ammonium Dinitramide(ADN)-based Monopropellant Thruster

In this study,the effects of porosity of the fore-catalytic bed and after-catalytic bed and preheat temperature on the decomposition and combustion characteristics of a 5N ammonium dinitramide(ADN)-based thruster were numerically investigated in terms of the distribution of components,temperature,and pressure.The results indicated that the porosity of the fore-catalytic bed and preheating temperature significantly affected the decomposition and combustion characteristics.The porosity of the fore-catalytic bed was optimized,and the thrust performance was demonstrated to improve with increasing of porosity of the after-catalytic bed and pre-heating temperature.The results were favorable for the investigation of decomposition and combustion characteristics and could also be beneficial to the design and manufacture of different types of ADN-based thrusters.

Effects of Temperature and Catalyst Concentration on the Growth of Aligned Carbon Nanotubes

The effects of preheating and pyrolysis temperatures and catalyst concentration on the synthesis of aligned carbon nanotubes （CNTs） using ferrocene as the catalyst and xylene as the carbon source in chemical vapor deposition were experimentally studied. The as-grown aligned CNTs were characterized by field emission scanning electron microscopy, transmission electronic microscopy, high-resolution transmission electronic microscopy, and Raman spectroscopy. The growth rate, the diameters, and the degree of crystal structure of the aligned CNTs were all found to depend on the preheating and pyrolysis temperatures and the catalyst concentration. The optimized conditions for the growth of aligned CNTs resulted in a rapid growth rate of 20.4 um/min, with the CNTs having a good, uniform crystal structure, and clean surfaces with little amorphous carbon. The results also show that higher preheating temperatures and lower ferrocene concentrations favor the growth of single-walled CNTs.

Low Temperature Growth of Vertically Aligned Carbon Nanotubes via Floating Catalyst Chemical Vapor Deposition Method

Synthesis of carbon nanotubes （CNTs） below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced. In this work, the effects of varying the preheating temperature on the synthesis of CNT were investigated. The reaction temperature was set at 570℃. The preheating set temperature was varied from 150 to 400℃ at 50℃ interval. Three O-ring shape heating mantels were used as heating source for the preheater. In situ monitoring device was used to observe the temperature profile in the reactor. Benzene and ferrocene were used as the carbon source and catalyst precursor, respectively. Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃. When the preheating temperature was increased up to 400℃, both the length and the alignment of CNTs produced were improved.

Dome Combustion Hot Blast Stove for Huge Blast Furnace

In Shougang Jingtang 5 500m 3 huge blast furnace ( BF ) design , dome combustion hot blast stove ( DCHBS ) technology is developed.DCHBS process is optimized and integrated , and reasonable hot blast stove ( HBS ) technical parameters are determined.Mathematic model is established and adopted by computational fluid dynamics ( CFD ) .The transmission theory is studied for hot blast stove combustion and gas flow , and distribution results of HBS velocity field , CO density field and temperature field are achieved.Physical test model and hot trail unit are established , and the numeral calculation result is verified through test and investigation.3-D simulation design is adopted.HBS process flow and process layout are optimized and designed.Combustion air two-stage high temperature preheating technology is designed and developed.Two sets of small size DCHBSs are adopted to preheat the combustion air to 520-600℃.With the precondition of BF gas combustion , the hot blast stove dome temperature can exceed 1 420 ℃. According to DCHBS technical features , reasonable refractory structure is designed.Effective technical measures are adopted to prevent hot blast stove shell intercrystalline stress corrosion.Hot blast stove hot pipe and lining system are optimized and designed.After blowing in , the blast temperature keeps increasing , and the monthly average blast temperature reaches 1 300℃ when burning single BF gas.

Effect of Mold Hardness on Microstructure and Contraction Porosity in Ductile Cast Iron

The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated.Molds with different hardnesses（0.41,0.48,0.55,0.62 MPa）and a sand mold prepared by Co2 method were used.The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated.The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases;therefore,the possibility of achieving a sound product without using any riser increases.

Influence of Mold Preheating and Silicon Content on Microstructure and Casting Properties of Ductile Iron in Permanent Mold

The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides,graphite nodule counts and shrinkage volume were investigated.The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased.The ductile iron with the carbon equivalent of 4.45 % and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 ℃.Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides.It is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon content.The suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 ℃ is the silicon content of 3.3% and carbon equivalent of 4.7%.

Numerical Simulation of Jet Behavior and Impingement Characteristics of Preheating Shrouded Supersonic Jets

As a novel supersonic jet technology,preheating shrouded supersonic jet was developed to deliver oxygen into molten bath efficiently and affordably.However,there has been limited research on the jet behavior and impingement characteristics of preheating shrouded supersonic jets.Computational fluid dynamics（CFD）models were established to investigate the effects of main and shrouding gas temperatures on the characteristics of flow field and impingement of shrouded supersonic jet.The preheating shrouded supersonic jet behavior was simulated and measured by numerical simulation and jet measurement experiment respectively.The influence of preheating shrouded supersonic jet on gas jet penetration and fluid flow in liquid bath was calculated by the CFD model which was validated against water model experiments.The results show that the uptrend of the potential core length of shrouded supersonic jet would be accelerated with increasing the main and shrouding gas temperatures.Also,preheating supersonic jets demonstrated significant advantages in penetrating and stirring the liquid bath.

Analysis of feed pelleting characteristics based on a single pellet press device

Pelleting is the most extensively used thermal processing method in feed industry.In this article,a single pellet press device was developed to investigate the pelleting processing of animal feed.Effects of moisture content(10%-18%w.b.),preheating temperature(60°C-100°C)and maximum compression force(0.2-0.6 kN)on feed pellet were determined and analyzed,as well as energy consumption.The results showed that unit density,pellet hardness and energy consumption were 0.87-2.92 g/cm3,1.08-4.55 kg,and 3.27-12.66 J/g,respectively.Unit density was found to increase with the increase of preheating temperature and maximum compression force,but decrease with the increase of moisture content.Pellet hardness showed a first ascending then descending trend with the increase of moisture content,but exhibited a positive relationship with both preheating temperature and maximum compression force.Energy consumption increased with the increase of maximum compression force,but exhibited descending trends with the increase of moisture content and preheating temperature.Due to its features of low cost,high efficiency and easy control,the single pellet press device has a wide application prospect in feed processing.

Experimental Investigations on NO_(x) Emission and Combustion Dynamics in an Axial Fuel Staging Combustor

Axial Fuel Staging(AFS)technology is an advanced low-emission combustion method in modem gas turbine,which divides the combustor into two axially arranged combustion zones.For revealing the characteristics of axial staged combustion,an industrial-grade combustor was designed and built.The distribution of temperature and velocity field in the combustor was presented with numerical simulation.And an Atmospheric Combustor Test Rig for axial staged combustion was built.The flow resistance characteristics of the combustor were measured at first.Then the effects of the equivalent ratio and the preheating temperature on the pollutant emission and combustion instability were investigated.The results show that the total pressure recovery coefficient in cold state is always above 98%;starting the secondary combustion at low load can reduce NO emissions by 50%,and can suppress the combustion oscillation amplitude of the combustor.At the design point with φ=0.62 and preheating temperature=400°C,NO emission and CO emission are 15.68 and 4.22 mg/m^(3)(@15%O_(2)).

Effects of Optimized Operating Parameters on Combustion Characteristics and NO_(x)Emissions of a Burner based on Orthogonal Analysis

To optimize the structure of the burner,improve the combustion performance,and reduce the emission of NO_(x),a self-circulating low NO_(x)combustion technology was used to design a new type of flue gas self-circulating low NO_(x)burner.Based on previous research on the numerical model of combustion and the composition of mixed gas on combustion and NO_(x)emissions,the effect of various factors on the ejection coefficient of the flue gas self-circulating structure was analyzed using the orthogonal test method,and the burner operating parameters,such as preheating temperature and excess air coefficient,were deeply studied through the three-dimensional finite element numerical model in this paper.The results show that the diameter ratio of the nozzle and the length of the cylindrical section of the flue gas self-circulating structure have great influence on its ejection and mixing ability.The optimal ejection coefficient was 0.4829.Overall,the amount of NO_(x)emissions greatly increased from 6.23×10^(-6)(volume fraction)at the preheating temperature 973 K to 3.5×10^(-3)at preheating temperature 1573 K.When the excess air coefficient decreased from 1.2 to 1,the maximum combustion temperature decreased from 2036.3 K to 1954.22 K,and the NO_(x)emissions decreased from 352.29×10^(-6)to 159.73×10^(-6).