International Journal of Minerals, Metallurgy and Materials

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Mechanical Method Determining Precipitation in an Ultra-Low Carbon Bainitic Steel

Zijiu Dang, Yan Thang, Jun Ke, Xinlai He, Shanwu Yang

1998, 5(3): 115-118.

中文摘要(255) PDF(9) SpringerLink

摘要:
Stress relaxation was chosen as the best method for monitoring the precipitation process. Tests were carried out on an ultra-low carbon bainitic steel containing Mn, Nb and B over 800~950℃. Specimens were solution treated at 1250℃ for a certain holding period. A prestain of 20% was applied at a strain rate of 0.1/s. The experimental results are displayed by a set of stress vs. 1g(time) curves different from the typical stress relaxation curves. There are two singularities forming a stress plateau on the stress vs.1g(time) curves when precipitates could be observed. Suppose the first one is the start of precipitation (P_s), and the second represcnts the fihish (P_f). As a result Precipitation-Time-Temperature relationship is described as C-shape curves based on two points. This mechanical method is suitable and precise for measuring precipitates in microalloyed steels during hot working.

Materials

Equilibrium Precipitation of Niobium Carbonitride in Austenite

Fuming Wang, Wenchao Li

1998, 5(3): 119-122.

中文摘要(237) PDF(9) SpringerLink

摘要:
The equilibrium between niobium carbonitride and austenite has been studied. Experimentally, X-ray diffaction technique was adopted to verify that the precipitates have the same composition and structure. Theoretically, Hillert and Staffansson's regular model about stoichimetric phase was used to describe the thermodynamic properties of multi-component precipitate. Calculated results agree well with experimental values from literatures.

Materials

High Temperature Ductility Loss of 16MnCr5 Pinion Steels

Haiwen Luo, Pei Zhao, Zijiu Dang

1998, 5(3): 123-128.

中文摘要(274) PDF(12) SpringerLink

摘要:
A wide ductility trough covering from 700 to 1100 is observed in the curve of Reduction of Area (RA) vs. tempetature for 16MnCr5 pinion steel. At 750℃, corresponding to the minimum of RA, it is grain boundary sliding that controls its hot ductility rather than usual Deforming Induced Ferrite (DIF), which can only appear just below 750℃ and slightly improve hot ductility. The volume fraction of ferrite is dependent on the strain and strain rate.Firstly a critical strain must be necessary for formation of DIF then with strain rate increasing, the volume fraction of DIF decreases but RA is elevated. In the γ phase region, hot ductility is seriously deteriorated because of grain boundary sliding promoted by oxidcs and sulfides at the grain boundary and recovered because of dynamic recrystallization at higher temperature; when strain rate increases, ductility is improved as there is insufficient time for cracks to propagate along the γ grain boundary as well as dynamically precipitating, and ductility trough becomes narrower because the temperature for onset of dynamic recrystallization decreases. In addition, γ→α phase transformation introduced by temperature drop before the tensile test encourages precipitation of AlN and impairs ductility.

Materials

Three-Dimensional and Cross-sectional Characteristics of Normal Grain Growth Based on Monte Carlo Simulation

Xiaoyan Song, Guoquan Liu

1998, 5(3): 129-133,139.

中文摘要(215) PDF(8) SpringerLink

摘要:
An appropriate Monte Carlo method was developed to simulate the three-dimensional normal grain growth more completely. Comparative investigation on the three-dimensional and the cross-sectional characteristics of normal grain growth was done. It was found that the time exponent of grain growth determined from cross-section exhibits the same rule of increasing slowly with time and approaching the theoretical value n = 0.5 of steadygrain growth as the three-dimensional (3-D) system. From change of the number of grains per unit area with timemeasured in cross-section, the state of 3-D normal grain growth may be predicted. The gtain size distribution incross-section is different from that in 3-D system and can not express the evolution characteristic of the 3-D distribution. Furthermore, there exists statistical connection between the topological parameters in cross-section and thosein three-dimensions.

Materials

Potential Oscillations of a Stainless Steel Electrode during Galvanostatic Polarization in a Mixed Solution of Sulfuric and Chromic Acids

K Ogura, W Lou, M Nakayama, T Fukum

1998, 5(3): 134-139.

中文摘要(272) PDF(10) SpringerLink

摘要:
Potential oscillations of a stainless steel electrode galvanostatically anodized have been observed in a mixture of chromic and sulfuric acids. The potential regularly oscillated between 1.6 V vs. SCE (lower) and 2.1V (upper) with a certain frequency. The potential values are affected neither by the composition of chromic and sulfuric acids nor by the magnitude of applied current density although the potential frequency is very sensitive to these parameters. This phenomenon is interpreted in terms of the repeated formation and disappearance of the saturated layer of dichromate ions on the electrode surface. Such scheme is consistent with the in situ FTIR spectroscopic result that the concentration of Cr₂O₇^2- ions on the electrode surface increased with time during the polarization at the lower potential but the change in concenetion of Cr₂O₇^2- ions was negligible at the higher potential.

Materials

Special Orientation Relationships Observed at the Early Stages of Recrystallization in Pure AlMn Alloy

Ping Yang

1998, 5(3): 140-146.

中文摘要(258) PDF(9) SpringerLink

摘要:
Electron Back Scattering Diffraction (EBSD) technique in a SEM was used to obtain local orientational information on new grains and their surrounding deformed matrices at the early stages of recrystallization in pure A1-1.3%Mn alloy. Results show that special orientation relationships including twin-relationship often exist between new grains, between new grains and deformed grains or between deformed grains. The occurrence of such special orientation relationships is attributed to the special deformation behavior in the samples with large initial grain size. The formation of recrystallization twins is discussed in a different way to those of traditional ones.

Simulation on Slag Splashing for LD Converter

Anren Wang, Shouli Yang, Baohang Tu

1998, 5(3): 146-146.

中文摘要(298) PDF(8) SpringerLink

摘要:
SeveraL parameters affecting slag splashing in LD converter have been discussed. Using parffin and starch model, a simulated test about 30 t converter has been made in laboratory and the modified Frode number was chosen as the main similar basis of the system. It was results that the optimized slag splashing parameters was obtained through data treatment The nitrogen gas flow rate is about 8 500 m³/h, the splashing time is of 3 min, and the lance height is of 0.8 m. It is necessary to add MgO or carbon into the slag to adjusting slag composition. Also, it is difficult for the splashed slag condensing on the line when the slag temperature is much higher

Materials

Structure and Formative Mechanism of Black Patina on Bronze Mirrors

Zhaozeng Ma, Ling Du, Xiulan Yin, Lianji Jin, Chunying Fang

1998, 5(3): 147-155.

中文摘要(312) PDF(8) SpringerLink

摘要:
The formation of the black patina induced by soil humic asid under different conditions was studied, the black, grey and brown colored shiny surfaces prepared in laboratory were analyzed. As a result the formation of tin-rich shiny black surface on bronze mirrors is the product of soil corrosion of the bronze mirrors. The patina is formed by reection between the alloy and the humic acid in soil, and leaching of copper and lead oxides through a long period time when the mirrors were buried under the ground leaving a dense compact corrosion-resistant layer consisted predominantly of stannic oxide microcrystal.

Water Model Study of Level Flunction in Continuous Casting Mold

Jiying Li, Chuanji Han, Kaike Cai, Subo Yang, Xuemo Yan

1998, 5(3): 155-155.

中文摘要(314) PDF(12) SpringerLink

摘要:
Using 0.6-scale warer modelling based on Fr-We number similitude criteria, the influences of the submerged entry nozzle configuration and operating practices on the level fluctuation in the mold which caused surface defects and mold power catching, were studied. It was found that the level flunction was resulted from gas injection, impacting of the stream and standing wave. The level turblence raises with the incresing of the gas injection, however the casting rate, immersion depth and jet angel of SEN have a dual influenc on the level fluctuation.

Physical Property Model of MnO-SiO₂ System

Sitong Niu, Jian Zhang, Guoguang Cheng

1998, 5(3): 155-155.

中文摘要(198) PDF(8) SpringerLink

摘要:
From the viewpoints of coexistence theory of the slag structure, the investigation on the structural units of MnO-SiO₂ system and the chemical reactions between them has been carried out. The relationships between the physical propenies of the slag and the mass action concentrations of its have been set up at certain temperature and slag composition range, which based on the thermodynamic data of the chemtical reactions between the units and the method of linear regression. The calculated data from the model are in good agreement with the measured results. These calculated values are more accurate and systematic than those from other expirical and semi-expirical formulas used at present.

Materials

Microstructural Characteristics of CuCr50 Alloy by Laser Refining

Baihe Miao, Jianping He, Donglang Shao

1998, 5(3): 156-159.

中文摘要(282) PDF(10) SpringerLink

摘要:
An investigation concerning the microstructural characterization of CuCr50 alloy layer by laser surface refining on the powder metallurgy substrate was carried out Significant refined proeutectic chromium crystals distributed in an Cr-rich eutectic and high mutual solubility of Cu and Cr elements in the CuCr50 alloy were examined by Backscattered Electron Imaging (BEI) and Energy Dispersive X-ray Spectrum (EDS) techniques. The results show that surface refining and alloying by high-power laser have a great potential to develop new and high performance alloys in the immiscible and limited solubility systems like Cu-Cr and other similar alloy systems.

Microstructral Evolution of the Dendritic AlSi₇Mg Alloy during Semi-solid Remelting

Weimin Mao, Xueyou Zhong, Huayu Wang

1998, 5(3): 159-159.

中文摘要(236) PDF(6) SpringerLink

摘要:
The microstructural evolution during partial remelting of dendritic AlSi₇Mg alloys was studied with the help of an electrical fumace. The results show that it is difficult to change all the primary a dendrites into the spheroidal α phases, when the dendritic samples of AlSi₇Mg alloy are remelted under 589 or (597±1)℃ and held on mis condition for 5 to 120 min. The results also show that the samples remelted can be deformed under the heavy force, if the holding time is longer under higher temperature.

Materials

Irradiation Damage of Oxide Dispersion Strengthened Ferritic Steel after Recrystallization

Benfu Hu, Shunmi Peng, H Takahashi

1998, 5(3): 160-164.

中文摘要(288) PDF(7) SpringerLink

摘要:
The evolution of secondary defects and the characteristics of the void swelling of electrons irradiated Oxide Dispersion Strengthened Ferritic Steels (ODS steels) after recrystallization were studied. It was found that recrystallization increases the void swelling of ODS steel as compared with solution and injected He⁺ + D⁺ states.There are two size ranges of voids formed in recrystallized ODS steel during irradiation, and bubbles can be preferential sites for the void formation. Polycrystal with low density of defects is formed, and sites where point defects disappear by irradiation decrease. This is the main reason for the increase of void swelling of ODS steel after recrystallization.

Materials

One-Dimensional Fractal Curves and Fractal Dimension Determination

Qikai Li, Yue Zhang, Wuyang Chu

1998, 5(3): 165-168.

中文摘要(252) PDF(7) SpringerLink

摘要:
Various methods for evaluating the fractal curves were reviewed and simulated on computer. It is shown box-counting and power spectrum methods generally give poor measuring results, while yard and variation methods could obtain good results. However,owing to multiple influencing factors, further study needs to be done before widespread application of variation method. In order to improve the measuring accuracy of yard method, a new method has been propoed to measure the fractal dimension by changing the instrumental resolutions.

Materials

Correlation between Thermal Expansion and Magnetic Characteristics of Fe-Ni Alloys in Fe_1-xNi_x/Cu Superlattices

Weizhong Tang, H Zabel

1998, 5(3): 169-174.

中文摘要(315) PDF(13) SpringerLink

摘要:
Thermal expansion behaviors of FeNi alloys were investigated by means of X-ray diffraction technique within a Fe_1-xNi_x/Cu superiattice structure. It was found that with a Ni concentration of x = 0.35, FeNi alloy layers showed the well-known Invar behavior, but for alloy layers with either lower or higher Ni concentrations, thermal expansion coefficients were larger. Based on results of magnetic measurements it is concluded that FeNi alloy layers with Ni concentrations lower than the Invar composition are in a superparamagnetic state which leads not only to low spontaneous magnetizations but also to large thermal expansions of the alloy layers.

Effect of the Solidification Conditions on the Microstructures of AlSi₇Mg Alloy during Semi-solid Remelting

Weimin Mao, Xueyou Zhong

1998, 5(3): 174-174.

中文摘要(242) PDF(6) SpringerLink

摘要:
The effect of the solidification conditions on the microstructures was studied during partial remelting of AlSi₇Mg alloy with the help of an electrical pipe-type fumace. The results show that the eutectic is remelted above all and α phases are gradually evolved into spheroidal shape,if the AlSi₇Mg alloys shrmd strongly by rotating electromagnetic field during the first solidification are heated again to 589 or 597℃ and have been held for a short time (for example, 5~10 min), and moreover, the higher the holding temperature,the faster the eutectic remelting process and α phase's evolution are. In contrast even though the AlSi₇Mg alloy's samples non-stirred with fine dendritic microstructures are heated to the same temperatures as those stirred by rotating electromagnetic field and have been held for 60 min,it is not possible to change all the dendritic a phases to speroidal α phase.

Materials

Annealing Texture Evolution of Ti-IF Steel during Batch Annealing

Jing Shi, Xianjin Wang

1998, 5(3): 175-179.

中文摘要(308) PDF(9) SpringerLink

摘要:
Texture development and recrystallization behavior of Ti-IF steel during Batch Annealing (BA) were investigared with X-ray diffraction and EBSP in lab, and the results were compared with research work on continu ous annealing (CA) with rapid heating rate. The basic tendencies are similar that eary nucleation takes place in <111>ND fibers, <110>RD fibers are consumed at the end of recrystallization, and <111>ND texture dominates over annealing texture. However, the detailed texture transformation during batch annealing is different and somewhat more compicated than tha in rapid-heating process. Moreover, misorientation plays an important role in texture transformation of BA In addition, the results of EBSP are consistent with that of ODF well.

Effects of Suspension Casting on Solidification Process of GCr15 Steel Ingot

Yan Yu, Qijie Zhai, Changhu Xing, Jinbao Chen, Hanqi Hu

1998, 5(3): 179-179.

中文摘要(230) PDF(8) SpringerLink

摘要:
The mechanism of inoculation in the case of suspension casting process has been studied through solidification kinetics. The effect of suspension casting process on temperature field, solidification rate, temperature gap of crystallization, effective distribution coefficient of solute and nucleation frequency during solidification process in steel ingot were discussed on the base of experiments. It has been found that the suspension casting process can increase both cooling at and solidification rate of steel ingot, improve the temperature field and solute distribution, narrow the temperature gap of crystallication, and increase the nucleation frequency. Thus, the solidification time can be shorten, the solute can be well distributied, the shrinkage porosity can be reduced and the grain of crystallization can be fined.

Materials

Improvement of Boxcar Integrator and Its Application to Low Resistance Measurement of Inductive Load Coil

Xisheng Li, Shaochun Wang

1998, 5(3): 180-184.

中文摘要(290) PDF(14) SpringerLink

摘要:
A boxcar integrator is described which is suitable for the low-repetition-rate signal processing. This boxcar integrator, named fixed-interval mode boxcar integrator, is able to reject harmonics other than the first harmonic component. It can also decrease the effective time constant In many situations, the antialiasing filter with narrow bandwidth will cause distortion of the input signal. The fixed-interval mode boxcar integrator with suitable gate width can achieve relative high performance without signal distortion because the bandwidth of its antialiasing filter can be wider than that in the fixed-Point boxcar integrator. ms boxcar integrator is used as majn part of signalprocessing circult in the low resisance measurement of inductive load coil. The results of experiments show that the fixed-interval boxcar integrator is suitable for low-repetition-rate use.

Effect of Pre-deformation on Abnormal Segregation of Grain Boundary during Recrystallization Process

Bing Cao, Xinlai He

1998, 5(3): 184-184.

中文摘要(260) PDF(7) SpringerLink

摘要:
The softening rates of Fe-30%Ni alloy containing boron after 10% and 40% deformation at 1000℃ have been measured by a method of interrupted compression, the recrystallization process has also been evaluated.The moving velocity of the boundary of new recrystallizing grain which was growing into the deformed grans has been calculated semi-quantitatively. By means of PTA technique, the abnormal segregation phenomenon on the moving boundary during recrystallization and the influence of pre-deformation have been investigated and the amount of B segregation on moving grain boundaries has been measured.Results indicate that the abnormal segregation of boundaries, when the new grains are growing, is concemed with the pre-deformation and the moving velocity of the bourdaries. This phenomenon is discussed by the gtain boundary widening mechanism.

AGC-ASC Decoupled Neural Networks Predictive Control Method

Thongsuo Shi, Yikang Sun

1998, 5(3): 184-184.

中文摘要(265) PDF(7) SpringerLink

摘要:
The coupling models for the thickness-crown objects is established. A Dynamic Matrix Controller based on the TH neural networks is given with the convergence property. The computer simulations with the AGC-ASC decoupled neural networks predictive control system is complemented and it shows that the stable states of neural networks are reached with on more that one μs, this has not only sahsfied the fast property of rolling process, but also obtained a higher control index.

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1998年第5卷第3期