热处理工艺对国产T23(HCM2S)耐热钢组织的影响

分析研究了热处理工艺对国产T23(HCM2S)耐热钢组织性能的影响.结果表明提高正火温度,晶粒不断长大,且晶粒内的孤岛状物也明显长大.正火后770℃回火,贝氏体、铁素体基体出现多边形化,随着回火时间的延长,晶粒有所长大,但在180min回火的试样组织中,出现再结晶现象,晶粒反而变得细小;另外,随着回火时间的增加,基体中小岛状物不断分解、减少,而细小的碳化物颗粒明显增多.探讨了组织的变化对性能的影响,分析表明,随着正火温度的升高,钢的持久强度提高;延长回火时间,虽钢的塑、韧性有所增加,但持久强度下降.综合考虑,正火温度和回火时间必须在一个适宜的范围内,既提高钢的机械性能,同时兼顾工业生产的经济性.     

12Cr-4Ni-3Mo-V-Nb-N叶片钢高频淬火后回火硬化现象

12Cr-4Ni-3Mo-V-Nb-N叶片钢在高频淬火后进行不同温度的回火,发现随回火制度不同,硬度在250℃/4 h回火后下降,但在250℃/4 h+500℃/4 h及500℃/4 h回火后明显升高,文章对不同温度下回火的组织进行了TEM观察,结果显示在500℃回火过程中弥散析出的MX相和M23C6是导致硬度升高的关键原因。     

高温用2(1/4)Cr-1Mo钢的研究

本文对厚度为100～400毫米的2(1/4)Cr-1Mo 钢板,从奥氏体化温度(920℃)冷却速度对金相组织的影响,以及回火过程对机械性能和高温抗拉强度的影响进行了研究。结果如下:(1)当冷却速度大于6℃/分可得到均匀的贝氏体组织,冷却速度提高时减少使机械性能恶化的块状铁素体。(2)不同热处理过程对常温强度性能的影响,被表示为拉森一米尔(Larson-Miller)回火参数的函数,以致可制造抗拉强度为56公斤/毫米~2～90公斤/毫米~2的2(1/4)Cr-1Mo 钢。(3)冷却速度大于6℃/分可保持良好的缺口韧性。通过低温回火使抗拉强度高于70公斤/毫米~2的钢时,则推荐10～15℃/分或更快的冷却速度。运用这些结果,已造出一台壁厚365毫米的锻造筒壳。从它的机械性能和贝氏体组织来看都说明在筒壳两端和整个厚度上是均匀一致的。     

国产9Cr-1Mo-V-Nb耐热钢的显微组织分析

运用光学显微镜和透射电子显微镜分析研究国产9Cr-1Mo-V-Nb耐热钢1040℃正火及随后780℃回火态的显微组织。结果表明,正火态的显微组织为典型的低碳板条马氏体,其弥散细小析出物为M_(23)C_6型碳化铬和MC型碳化钒,经回火后板条马氏体粗化,位错密度下降,孪晶消失,马氏体再结晶开始进行,局部有亚胞形成,但板条的特征依然存在。认为由于合金碳化物聚集长大速度较慢以及Cr、Mo通过固溶强化提高原子间结合力,使原子扩散的激活能升高,推迟其回复和再结晶的过程,从而使回火抗力增长,这种组织结构的稳定性非常有利于高温蠕变性能的改善。     

对机车柴油机喷油泵用GCr15钢淬、回火工艺的研究

对不同原始组织状态的GCr15钢进行淬、回火工艺试验。试验发现碳化物不均匀性超过标准要求时,将增大淬、回火组织的过热敏感性,通过正火、球化退火使之符合标准的GCr15钢,其过热敏感性仍较强。指出要获得合格的淬、回火组织,必须对碳化物不均匀性级别进行严格控制。根据GCr15钢原始组织状态调整淬火工艺,并对有效淬火温度范围进行划分。     

宽幅细晶TC4钛合金薄板的制备及其性能研究

研究了退火温度对成品板材组织、晶粒尺寸、室温力学性能的影响,并对板材进行了超塑拉伸试验研究。研究结果表明:在普通退火方式下,板材横纵向的抗拉强度和屈服强度随退火温度的升高而减小,延伸率呈现先增大后减小的趋势,在780℃时强度和塑性得到了良好的匹配;随退火温度的升高,初生α的晶粒尺寸略有增大。超塑拉伸试验结果表明:在温度为910℃,初始应变速率为4×10-4s-1,板材最大延伸率达到789%。     

超超临界汽轮机用ZG13Cr9Mo2Co1VNbNB钢的组织与性能研究

介绍了1000MW等级超超临界汽轮机组大型铸件用材ZG13Cr9Mo2Co1VNbNB钢。通过相图计算、模拟焊后热处理,对比了材料的组织性能变化。试验结果表明:ZG13Cr9Mo2Co1VNbNB钢正火+高温回火后为典型的板条马氏体组织;材料中未形成Laves相;模拟焊后热处理降低了材料的屈服强度和韧性,塑性有所提高。     

固溶处理对TP347H钢性能的影响

本文主要研究了固溶处理加热温度对ＴＰ３４７Ｈ钢常温，短时高温性能及持久强度的影响。同时观察了不同温度固溶处理后的金相组织。研究结果认为，ＴＰ３４７Ｈ钢冷变形后的常温强度随固溶处理温度升高而降低，塑性、韧性随固溶处理温度提高。研究结果证明，１１６０￣１１９０℃固溶处理可获得符合要求的持久强度。     

热处理对SA-335P92焊接接头力学性能的影响

通过对SA-335P92钢的焊接接头分别进行Ac1点以下及Ac3点以上温度的焊后热处理的工艺试验,研究了焊后热处理对SA-335 P92钢焊接接头的力学性能的影响.试验结果表明手工氩弧焊加焊条电弧焊的SA-335 P92焊接接头在分别经历了正火加回火处理和去应力退火后,焊接接头的力学性能均能满足标准的要求,而且正火加回火处理后的力学性能要优于去应力退火后的力学性能.     

(42)锅炉用钢的热处理

锅炉用钢的性能可以通过“钢的合金化”来实现,要达到预期性能,应对钢实施热处理工艺。钢在加热和冷却过程中会发生组织结构的变化。加热后保温时间的长短和随后冷却速度的高低,也会影响组织结构的转变。使钢质本身组织结构的变化改变了钢的性能。钢的热处理就是对钢施以不同的加热、保温和冷却来获得所需要性能的一种工艺。锅炉用钢常用的热处理工艺有正火、淬火、固熔回火热处理,还有锅炉用钢经焊接后的消除应力热处理 (1)钢的正火     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。