中国600℃蒸汽参数火电机组用锅炉钢管国产化研制进展

总结了过去10年中国研究、试制和批量生产超(超)临界火电机组用P92、S30432和S31042锅炉钢管的进程,重点研究了中国在P92、S30432和S31042钢管最佳化学成分配比和最佳热处理制度确定上的主要技术突破,探讨了锅炉钢长期服役过程中的组织稳定性问题,介绍了P92、S30432和S31042钢管工业试制进展及其在中国600℃蒸汽参数超超临界火电机组上的应用前景。技术进步的结果表明,中国已基本掌握了P92、S30432和S31042钢管的生产制造技术,并正在形成批量供货的能力。     

T91/P91 一种应用日益广泛的耐热钢

随着对节能和环保的重视,目前大容量、高效率的亚临界、超临界机组已在国内电站获得广泛应用。因此,作为一种高温、高压耐热钢最理想的材料,T91/P91钢具有广阔的应用前景。T91/P91钢是一种改进的9Cr-1Mo钢,在美国试验材料学会(ASTM)和美国机械工程师学会(ASME)标准中,T91代表锅炉用小管子,P91代表大直径钢管,F91代表锻钢。法国在NFA标准中用TUZ10CDVNb09-01表示。德国曼内斯曼钢管公司用X10CrMoVNb9-1表示。我国在GB5310-95中用10CrMo1VNb表示[1]。T91/P91钢具有优良的高温蠕变性能,日益广泛地应用于亚临界及超临界火力发电…     

(超)临界锅炉用E911钢管的性能评定试验

对德国瓦鲁瑞克和曼内斯曼公司生产的Φ159 mm×27 mm的E911钢管进行了原材料热处理、抗氧化性能、持久强度的试验,并对供货状态及优选热处理工艺的E911钢管进行了时效试验和时效后的力学性能、金相组织测定。试验结果表明,在650℃下E911钢管,其常温性能、高温性能、持久强度都比T91要好得多,完全可以代替TP304H、TP321H和TP347H不锈钢管,可解决异种钢焊接问题,并可降低锅炉的制造成本。     

超临界超超临界锅炉管品种的开发现状

本文介绍了超临界、超超临界锅炉管的开发背景和品种发展现状,其中包括铁素体锅炉管、新型奥氏体不锈钢锅炉管、镍基合金锅炉管、加w的2.25%Cr(T/P23)钢管、改进型9% Cr-1% Mo(T/P91)钢管、加W的9% Cr( T/P92)钢管、双金属复合管等锅炉用管的主要化学成分、力学性能和耐蚀性能。     

热穿孔温度对T91钢管持久强度的影响

研究了φ75mm管坯穿孔温度对T91锅炉钢管高温力学性能的影响。结果表明，1200℃穿孔温度能获得持久强度和持久断裂塑性较好配合的综合性能。     

宝钢T92钢管焊接性能试验及焊接接头运行评价

检验及分析评价了宝钢产SA-213 T92钢高压锅炉管的焊接工艺性能及焊接接头性能,对T92钢焊接接头挂管电厂锅炉实炉运行考验,并对服役1年的T92钢焊接接头进行了高温持久强度试验及评价。结果表明,宝钢T92高压锅炉管焊接工艺性能及接头性能各项技术指标均符合DL/T 868—2004标准要求,实炉运行业绩良好,服役1年的T92管焊接接头高温持久强度总体仍达到或超过GB 5310—2008、EN10216—2007标准要求。     

S31042耐热钢650 ℃持久的析出相对持久塑性的影响

 S31042钢是一种重要的超临界和超超临界锅炉用钢。针对该钢持久塑性差的问题,采用扫描电镜和透射电镜研究了S31042钢在650 ℃持久前后的微观组织,主要探讨了析出相对持久塑性的影响。结果表明：持久1 608 h,S31042钢的塑性快速下降。而后塑性缓慢下降,并逐渐趋于稳定。S31042钢持久过程中主要的析出相为二次NbCrN和M23C6,长期持久会导致少量σ相和Cr3Ni2SiC的析出。S31042钢持久塑性显著下降的主要原因是由于M23C6在晶界上的析出。此外,链状M23C6、立方形M23C6以及未溶的NbCrN对S31042钢的持久塑性也有害。     

超超临界火电机组用锅炉钢技术国产化问题

综述了国内外超超临界火电机组技术的发展及其对中国实现节能减排战略目标和保障国家能源安全的重大意义,阐明了先进锅炉钢技术是支撑超超临界火电机组技术发展的关键所在和物质基础。总结了近20年来中国锅炉钢技术研究的进展、国家研究计划以及与国外先进水平的差距。重点介绍和分析了超超临界火电机组建设用关键锅炉钢(T/P92、S30432、和S31042)国产化过程中面临的主要技术问题及解决措施,同时探讨和展望了中国先进锅炉钢未来的发展方向。     

正火温度对12Cr2MoWVTiB耐热钢高温性能的影响

从不同正火温度对高压锅炉用１２Ｃｒ２ＭｏＷＶＴｉＢ钢管高温性能影响的研究结果表明，生产过程中该钢的正火温度不低于１０２０℃，才能满足锅炉设计对该钢持久强度性能的要求。     

中国600oC蒸汽参数火电机组用锅炉钢管国产化研制进展

 本文总结了过去10年中国研究、试制和批量生产超（超）临界火电机组用P92、S30432和S31042锅炉钢管的进程,重点研究了中国在P92、S30432和S31042钢管最佳化学成分配比和最佳热处理制度确定上的主要技术突破,探讨了锅炉钢长期服役过程中的组织稳定性问题,介绍了P92、S30432和S31042钢管工业试制进展及其在中国600oC蒸汽参数超超临界火电机组上的应用前景。技术进步的结果表明,中国已基本掌握了P92、S30432和S31042钢管的生产制造技术,并正在形成批量供货的能力。     

Suppression of creep cavitation in precipitation-hardened austenitic stainless steel to enhance creep rupture strength

Extensive creep cavitation in Ti, Nb and Cu containing precipitation hardened austenitic steels was found to limit the usefulness of deformation resistance to increase long-term creep rupture strength. The steels were microalloyed with boron and cerium that resulted in increase in creep rupture strength and ductility of the steels significantly. Grain boundary sliding and creep cavity nucleation and growth in the steels were suppressed greatly on microalloying. Auger spectroscopic analysis revealed the segregation of boron instead of sulfur on cavity surface and the absence of sulfur contamination of grain boundary upon the microalloying. Suppression of creep cavitation through the control of trace elements segregation along with the precipitation hardening increased the creep rupture strength of austenitic stainless steels.     

Investigation on the strengthening mechanism of S30432 austenitic heat-resistant steel

From the viewpoint of energy-saving and environment protection,it is necessary to develop Ultra Super Critical（USC） fossil-fired power plants.In order to ensure the reliable operation of power plants under high steam conditions,good mechanical properties（particularly high creep strength）,corrosion resistance and fabricability are generally required for the heat resistant steels used in USC boilers.Among these heat-resistant steels,S30432 austenitic heat-resistant steels are of interest due to high creep strength,excellent oxidation and corrosion resistance at temperatures up to 650 -700℃.In this paper,the strengthening mechanism of S30432 austenitic heat-resistant steel was investigated based on the precipitation behavior of S30432 during aging and creep at 650℃.Results show that the microstructure of as-supplied S30432 steel is austenite,the main precipitation consists of only Nb（C,N）.After aged for 10 000 h or crept for 10 712 h,there is a slight increase in the size of fine Nb（C,N）,but the transformation from Nb（C,N） to NbCrN does not occur.Aging and creep results in the precipitation ofε-Cu and M₂₃C₆.The coarsening velocity ofε-Cu particles diminishes greatly and they are still very fine in the long-term creep range.With the increase of aging and creep time M₂₃C₆ carbides tend to coarsen gradually.The size of M₂₃C₆ is larger and the coarsening is easier in contrast toε-Cu and Nb（C,N）.Nb（C,N） precipitates in the as-supplied microstructure,while aging and creep result in the precipitation ofε-Cu and M₂₃C₆.High creep rupture strength of S30432 steel is attributed to the precipitation hardening ofε-Cu,Nb（C,N） and M₂₃C₆.Extremely,ε-Cu plays an important role in improving the creep rupture strength of S30432,and at least 61%of the creep rupture strength of S30432 at 650℃results from the precipitation hardening ofε-Cu particles.     

Effects of Mn,Si, and purity on the design of 3.5NiCrMoV, 1CrMoV,and 2.25Cr-1Mo bainitic alloy steels

Three high-temperature bainitic alloy steels were evaluated in the laboratory to determine the effects of Mn, Si, and impurities (i.e., S, P, Sn, As, and Sb) on microstructure and mechanical properties. The alloy steels were 3.5NiCrMoV and CrMoV, which are used for turbine rotors, and 2.25Cr-1Mo, which is used in pressure vessel applications. The important effects of Mn, Si, and impurities, which should control the design of these high-temperature bainitic steels, are presented. Key results are used to illustrate the influence of these variables on cleanliness, overheating, austenitizing, hardenability, tempering, ductility, toughness, temper embrittlement, creep rupture, and low-cycle fatigue. Low levels of Mn, Si, and impurities not only result in improved temper embrittlement resistance in these steels but also lead to an improvement in creep rupture properties (i.e., improved strength and ductility). These results have produced some general guidelines for the design of high-temperature bainitic steels. Examples illustrating the implementation of the results and the effectiveness of the design guidelines are provided. Largely based on the benefits shown by this work, a high-purity 3.5NiCrMoV steel, which is essentially free of Mn, Si, and impurities, has been developed and is already being used commercially. T. OHHASHI was formerly Research Scientist, Japan Steel Works, Ltd., Muroran Research Laboratory, 4 Chatsumachi, Muroran, 051 Japan.     

New approach to predict the long-term creep behaviour and evolution of precipitate back-stress of 9–12% chromium steels

Modern advanced 9–12 % Cr steels are complex alloys with excellent creep strength even at high temperatures up to 620°C. The mechanical properties of these steels are significantly influenced by the presence and stability of various precipitate populations. Numerous secondary phases grow, coarsen and, sometimes, dissolve again during heat treatment and service, which leads to a varying obstacle effect of these precipitates on dislocation movement. In this work, the experimentally observed creep rupture strength of an modified 9–12% Cr steel developed in the European COST Group is compared to the calculated maximal obstacle effect (Orowan stress) caused by the precipitates present in these steels for different heat treatment conditions. It is shown that the differences in creep rupture strength caused by different heat treatments disappear after long time service. This observation is discussed on the basis of the calculated evolution of the precipitate microstructure. The concept of boosting long-term creep rupture strength by maximizing the initial creep strength with optimum quality heat treatment parameters for precipitation strengthening is critically assessed.     

Effect of Sb, P, Sn and B on the microstructure and creep properties of normalized and tempered 1.25 Cr-0.5 Mo steels

A program to study the effect of Sb, P, Sn and B on creep properties of four normalized and tempered 1.25 Cr-0.5 Mo steels at 538°C (1000°F) has been completed. Results show that even a combined addition of large amounts of Sb, P and Sn does not affect short time creep strength or ductility of the steel at 538°C (1000°F). Addition of B resulted in an increase or decrease of creep strength depending on the nature of the impurity species present, presumably due to B-impurity interactions. Regardless of the effect on creep strength, B additions caused sharp reductions in rupture ductility in all cases. Comparison of the present results on the four laboratory steels (100 pct bainite) with results of a previous study on a commercial steel (60 pct bainite + 40 pct ferrite) show that the effect of microstructure becomes negligible and rupture strength values of the various steels at 538°C (1000°F) approach each other at rupture times in excess of 10⁴ h.     

Effect of Sb,P, Sn and B on the microstructure and creep properties of normalized and tempered 1.25 Cr−0.5 Mo Steels

A program to study the effect of Sb, P, Sn and B on creep properties of four normalized and tempered 1.25 Cr−0.5 Mo steels at 538°C (1000°F) has been completed. Results show that even a combined addition of large amounts of Sb, P and Sn does not affect short time creep strength or ductility of the steel at 538°C (1000°F). Addition of B resulted in an increase or decrease of creep strength depending on the nature of the impurity species present, presumably due to B-impurity interactions. Regardless of the effect on creep strength, B additions caused sharp reductions in rupture ductility in all cases. Comparison of the present results on the four laboratory steels (100 pct bainite) with results of a previous study on a commercial steel (60 pct bainite + 40 pct ferrite) show that the effect of microstructure becomes negligible and rupture strength values of the various steels at 538°C (1000°F) approach each other at rupture times in excess of 10⁴ h.     

Thermal treatment improving creep properties of nitrogen-added Mod.9Cr-1Mo steels

Generation IV reactors are being developed to produce a reliable energy safely and with an economic benefit, because nuclear energy is being seriously considered to meet the increasing demand for a world-wide energy supply without environmental effects. Ferritic/martensitic steels are attracting attention as candidate materials for the Gen-IV reactors due to their high strength and thermal conductivity, low thermal expansion, and good resistance to corrosion. In recent years, new ferritic/martensitic steels have been developed for ultra supercritical fossil power plants through advanced technologies for steel fabrication. The microstructural stability of these materials for the pressure vessel, cladding and core structure of the VHTR and SFR is very important. Nitrogen is a precipitation hardening element, and the thermal stability of nitrides is superior to that of carbides. So the formation of nitrides may improve the thermal stability of the microstructure and eventually increase the creep rupture strength of high Cr steels. The effect of nitrogen on the creep rupture strength and microstructure evolution of nitrogen-added Mod.9Cr-1Mo steels has been studied. Creep testing was carried out at 873 and 923 K under constant load conditions. The optimum controlled Cr₂X precipitates were developed by special heat treatment, and they were not dissolved after a creep deformation. These fine and stable Cr₂X precipitates contributed to the increase of the creep rupture strength. The prior austenite grain size and martensite lath width were decreased by the resultant stable nitrides.     

Creep Rupture Strength and Microstructure of Low C-10Cr-2Mo Heat-Resisting Steels with V and Nb

The new ferritic heat-resisting steels of 0.05C-10Cr-2Mo-0.10V-0.05Nb (Cb) composition with high creep rupture strength and good ductility have already been reported. The optimum amounts of V and Nb that can be added to the 0.05C-10Cr-2Mo steels and their effects on the creep rupture strength and microstructure of the steels have been studied in this experiment. The optimum amounts of V and Nb are about 0.10 pct V and 0.05 pct Nb at 600 °C for 10,000 h, but shift to 0.18 pct V and 0.05 pct Nb at 650 °C. Nb-bearing steels are preferred to other grades on the short-time side, because NbC precipitation during initial tempering stages delays recovery of martensite. On the long-time side, however, V-bearing steels have higher creep rupture strength. By adding V to the steels, electron microscopic examination reveals a stable microstructure, retardation during creep of the softening of tempered martensite, fine and uniform distribution of precipitates, and promotion of the precipitation of Fe₂Mo.     

Creep rupture strength of tungsten-alloyed 9-12 % Cr steels for piping in power plants

The creep rupture strengths of the three tungsten-alloyed 9-12% Cr-steels E 911, NF 616 and HCM 12A are discussed. It is shown that Larson-Miller assessments may lead to an overestimation of the long-term creep rupture strength because of microstructural changes. The presented assessments indicate that all three alloys will have similar creep rupture strengths in the range of 110-120 MPa for 10⁵ h and 600°C. To obtain reliable estimates for creep rupture strength, however, further long-term tests are needed. In any case, the tungsten-alloyed steels will enable the main steam temperature to be raised by about 20°C over that possible with P 91.     

The effect of tungsten on creep

The effect of tungsten on creep behavior and microstructural evolution was investigated for tempered martensitic 9Cr steels with various W concentrations from 0 to 4 wt pct. The creep rupture testing was carried out at 823, 873, and 923 K for up to 54 Ms (15,000 hours). The creep and creep rupture strength increased linearly with W concentration up to about 3 wt pct, where the steels consisted of the single constituent of the tempered martensite. It increased only slightly above 3 wt pct, where the matrix consisted of the tempered martensite and δ-ferrite. The minimum creep rate was described by a power law. The apparent activation energy for the minimum creep rate showed a tendency similar to the W concentration dependence of the creep-rupture strength and was larger than the activation energy for self-diffusion at high W concentrations above 1 wt pct. The martensite lath microstructure with fine carbides along lath boundaries was responsible for a high resistance to creep deformation. With increasing W con- centration, the martensite lath microstructure became stabilized, which decreased the minimum creep rate and increased the apparent activation energy for the minimum creep rate.