煅后石油焦氢含量与比电阻和真密度关系的研究

介绍了测定煅后石油焦简称煅后焦中氢含量的原理、实验装置、测定步骤和计算公式，同时测定煅后焦的粉末比电阻的真密度。绘制了煅后焦氢含量与其比电真密度关系曲线，提出氢含量作为煅后焦性能指标的可行性与可靠性。     

石油焦高温煅烧技术的探讨和实践

探讨了煅烧温度对煅后焦质量的影响,依据不同煅烧窑炉的状况,通过以生焦挥发份调配为主、微量元素调配为辅的原料耦合技术,对窑况各项参数实时调控,使煅烧温度达到1300℃以上,并保持温度波动范围不超过20℃,实现了石油焦的高温煅烧,使煅后焦的真密度达到2.05g/cm3以上并保持稳定,为提高阳极质量创造了条件。     

罐式煅烧炉煅后焦质量的影响因素及改进措施

文章对影响罐式煅烧炉煅后焦质量的因素进行了深入分析,并结合中国铝业股份有限公司山东分公司煅烧生产实际提出了改进措施。措施实施后,取得了良好的效果。     

石油焦煅烧回转窑控制系统优化设计与应用

阐述了回转窑自动控制来统优化设计方案与应用方法.回转窑实现自动控制后,其生产效益得到显著提高,煅后焦各项指标得到了改善.     

Prediction of HAZ grain size in welding of ultra fine grained steel with different parameters

The temperature field and thermal cycling curve in the heat-affected zone during welding 400 MPa ultra fine grained steel by plasma arc were simulated using finite element method.The principle of grain growth kinetics was used to predict the grain size in the heat-affected zone under different welding parameters.The simulation results show that the growing tendency of HAZ grain could be controlled by adjusting the welding parameters,but the growth of HAZ grain could not be eliminated at all.The HAZ grain size became small with increasing of the cooling rate and added with increasing of welding current,arc voltage and welding speed.     

Microstructure and properties of CVD coated on gradient cemented carbide with different WC grain size

In this paper, cemented carbides with gradient surface enriched in Co phase and depleted of cubic phases were prepared by one-step vacuum sintering. The gradient cemented carbides of different WC grain size were used as the substrates of CVD coatings. The effects of WC particle size on the formation of gradient layer, microstructure and properties of the gradient cemented carbides were investigated. Besides, the influence of WC grain size and gradient layer on microstructure, growth and adhesion strength of the coatings were studied. The results showed that the thickness of surface gradient layer decreased with increasing WC particle size, which was attributed to the decreased diffusion paths and the increased diffusion distance. The interface between the surface gradient layer and the bulk was disordered due to abnormal grain growth of WC in ultrafine cemented carbide. The microhardness across the direction of the fcc-free (Face Center Cubic Free) surface layer to the bulk were similar in the three gradient cemented carbides, and could be expressed as: from the surface to the inner, the microhardness decreased firstly, then increased sharply around the interface, and subsequently dropped to the bulk level. The coating on the fcc-free surface layer was thicker than that on bulk, and the coating on the substrate with fine-sized WC grains is the thickest. The increase of the WC grain size in the substrate could improve the bonding strength of the coating. Furthermore, the presence of Co-rich layer could improve the bonding strength. However, bonding strength was poor for the grain size of ultrafine.     

Microhardness measurements and the Hall-Petch relationship in an Al---Mg alloy with submicrometer grain size

An Al-3% Mg solid solution alloy was subjected to intense plastic deformation, using either equal-channel angular (ECA) pressing or torsion straining, to produce grain sizes in the submicrometer range. Static annealing at elevated temperatures led to grain growth and average grain sizes of up to > 100 μm. As-fabricated and statically annealed specimens were used to determine the variation in microhardness with grain size, and results confirm that the Hall-Petch relationship persists down to at least the finest grain size examined experimentally (90 nm). The results provide no evidence to support the claims of a negative Hall-Petch slope when the average grain size is very small, but there is evidence of a decrease in the slope of the Hall-Petch plot at the very finest grain sizes (< 150 nm); this is attributed to the increased participation of mobile extrinsic dislocations in the boundary regions when taking the hardness measurements.     

The brittle-to-ductile transition in cold rolled tungsten plates: Impact of crystallographic texture,grain size and dislocation density on the transition temperature

The aim of this paper is to elucidate the mechanisms controlling the brittle-to-ductile transition (BDT) in pre-deformed, textured, polycrystalline body-centred cubic (bcc) metals by the example of cold rolled tungsten (W).For this purpose, five sheets were rolled out from one and the same sintered ingot, by various levels, representing degrees of deformation of 1.8, 2.5, 3.0, 3.4, and 4.1 (this refers to 83.5%, 91.8%, 95.0%, 96.7%, and 98.3% in the technical notation). Toughness tests show that the BDT temperature decreases with increasing degree of deformation from 115 °C ± 15 °C (388 K ± 15 K) down to −65 °C ± 15 °C (208 K ± 15 K). This is an improvement of >600 K compared with a sintered ingot.In this paper we perform an in-depth analysis of the microstructure of the five sheets mentioned above. This analysis includes the assessment of (i) crystallographic texture, (ii) grain size and (iii) dislocation density. A comparison between microstructural features and experimental data confirms our working hypothesis which states that the BDT is controlled by the glide of screw dislocations and that the transition temperature decreases with decreasing spacing, λ, of dislocation sources along the crack front. Sources for dislocations may be the intersection points of grain boundaries with the crack front (BDT-temperature-grain-size-relation) or dislocation multiplication processes such as e.g., the expansion of open and closed loops (impact of dislocation density).     

Microhardness measurements and the Hall-Petch relationship in an AlMg alloy with submicrometer grain size

An Al-3% Mg solid solution alloy was subjected to intense plastic deformation, using either equal-channel angular (ECA) pressing or torsion straining, to produce grain sizes in the submicrometer range. Static annealing at elevated temperatures led to grain growth and average grain sizes of up to > 100 μm. As-fabricated and statically annealed specimens were used to determine the variation in microhardness with grain size, and results confirm that the Hall-Petch relationship persists down to at least the finest grain size examined experimentally (∼90 nm). The results provide no evidence to support the claims of a negative Hall-Petch slope when the average grain size is very small, but there is evidence of a decrease in the slope of the Hall-Petch plot at the very finest grain sizes (< 150 nm); this is attributed to the increased participation of mobile extrinsic dislocations in the boundary regions when taking the hardness measurements.     

Investigation of the correlation between growth restriction and grain size in Cu alloys

The growth restriction factor Q of the alloying elements of the Cu-system was determined using thermodynamic software tools to obtain accurate Q-values. A comprehensive list was given for a nominal solute content of 1 wt-%. Based on the calculations, melting experiments were carried out under defined casting conditions given by the TP-1 test to evaluate the correlation between Q and grain size in Cu alloys.     

Wear damage of cemented carbides with different combinations of WC mean grain size and Co content. Part I: ASTM wear tests

In the present work we made and examined cemented carbides characterized by very different WC grain sizes varying from near-nano with a WC mean grain size of about 200 nm to coarse-grain with a WC mean grain size of about 4.5 μm and Co contents varying from 3 to 24 wt.%. The major objective of the present work was to examine the wear damage, wear behavior and wear mechanisms of cemented carbides having nearly the same hardness but greatly varying with respect to their WC grain size and Co content in the high-load ASTM B611 test and low-load G65 test.Both the hardness and resistance to fracture and micro-fatigue of cemented carbides play an important role in the wear damage by use of the high-stress ASTM B611 test when the carbide surface is subjected to alumina particles at high loads. In this case, the wear-resistance increases with increasing the WC mean grain size and decreasing the Co content at nearly the same hardness of the different cemented carbides. The submicron and near-nano cemented carbides are characterized by lower wear-resistance in comparison with the coarse-grain grade due to their reduced fracture toughness, fracture resistance and resistance to micro-fatigue.The Co mean free path in the carbide microstructure plays an important role with respect to wear-resistance in the low-stress ASTM G65 test when the carbide surface is subjected to gentle scratching by abrasive silica particles. The predominant wear of the thick Co interlayers leaving unsupported WC grains plays the decisive role in the wear behavior of the coarse-grain grade resulting in its low wear-resistance. In contrast to the ASTM B611 test the wear rate decreases with decreasing the WC mean grain size and increasing the Co content due to the corresponding reduction of Co mean free path in the carbide microstructure. As a result, the wear-resistance of the near-nano grade in the ASTM G65 test is the best of all in spite of its reduced fracture toughness.Phenomena of micro-fatigue, micro-fracturing and micro-chipping are found to play a decisive role in the wear damage of cemented carbides if they are subjected to abrasion wear, high loads and severe fatigue.