秦山核电站320MW汽轮机静叶片裂纹的焊接修复

对秦山核电站320 MW汽轮机静叶裂纹产生的原因进行了分析,从母材的材质性能、裂纹倾向、焊接拘束及应力状态等方面,对静叶焊接修复的可行性进行了分析,针对马氏体不锈钢的焊接修复特点,分析了不同的焊接修复方案,制定了合理的修复焊接工艺,着重阐述了裂纹挖补、焊前预热、母材小热输入焊接、焊后热处理及焊后PT检查等一系列修复措施。     

1Cr12Mo钢的高温回火脆性研究

1Cr12Mo钢是马氏体型耐热不锈钢,是汽轮机叶片的常用材料。由于该钢有高温回火脆性,在实际生产中冲击性能经常不合格。两次回火处理能改善1Cr12Mo钢的冲击性能,提出了叶片返修时可供选用的热处理工艺。     

Effect of minor change in composition on toughness of weldmetal for repair of turbine blades made of martensitic stainless steel

Abstract

Repair welding procedure for cracked turbine blades, made of 13Cr–2˙6Ni–1˙1Mo martensitic stainless steel, has been developed using gas tungsten arc welding process and a twin wire filler metal. The twin wire consists of a 1˙5 mm diameter ER 16-8-2 and a 2˙0 mm diameter ER 410 filler wires tack welded along the length of the two filler wires. A two stage post-weld heat treatment at 675°C for 2 h and 615°C for 4 h, such that the first heat treatments is above the Ac ₁ temperatures of the weld metal and the second is just below its Ac ₁ temperature; has been found to be suitable for obtaining good mechanical properties for the weldment. The weldment has a good combination of transverse weldment strength and weldmetal toughness, with its room temperature yield strength and Charpy V notch impact toughness being similar to that of the turbine blade material.     

Mechanical properties of 422 stainless steel repaired via wire feed laser welding

Abstract

Laser welding with filler wire additions could be used in restoration of components that are of high cost or sometimes difficult to procure, such as steam turbine blades in fossil fuel power plants. In the present work, machined V groove specimens were employed to simulate laser repair of Carpenter 636 stainless steel (SS), which has a similar composition to a blade material, type 422 SS. Before repair welding, a heat treatment procedure including solution and temper treatments of the specimens was carried out according to the mechanical and microstructural analyses of a used blade after 20 years service at about 540° C. Tensile, impact, and fatigue crack growth tests of weld repairs using 410 SS filler wire were conducted. The weld repairs exhibited an impact toughness similar to that of the base metal and a lower fatigue crack growth rate than the base metal. However, the lower hardness associated with 410 SS filler metal led to tensile fracture in the weld metal of repaired specimens. Accordingly, the use of 410 SS filler metal for repair welding type 422 SS components should be limited to regions under low stress.     

Repair welding of cracked turbine shroud using matching composition consumables

Abstract

Repair welding of a crack in the III-stage shroud of a high pressure turbine, was carried out using matching composition ER 410 filler wire by the gas tungsten arc welding (GTAW) process with ultra high purity argon as shielding and backing gas. The development of the repair welding procedure involved laboratory studies for the selection of a suitable ER410 filler wire, optimisation of welding parameters and PWHT. Mock up welding under simulated on-site constraints confirmed the feasibility to produce in situ sound weld joint. In situ repair welding and localised PWHT was carried out successfully. NDT and in situ metallography of the repair-welded region confirmed adequate tempering of the martensitic weldment during the localised PWHT.     

Laser cladding repair of turbine blades in power plants: from research to commercialisation

Abstract

Reliable and efficient power generation is a major global issue due to both political and environmental concerns. Nevertheless, many critical components, particularly the blades of the low pressure (LP) side of power generating steam turbines, are subject to failure due to severe erosion at the leading edges. Since taking machines offline for maintenance and removal of damaged blade for repair is extremely expensive, increasing the service life of these critical components offers significant economic and political benefits. Conventional techniques to increase service life include brazing of an erosion shield at the leading edge of the turbine blade, open arc hardfacing, and cladding with erosion resistant materials using gas tungsten, manual metal or plasma transferred arc welding. The authors have been investigating since 2001 the use of laser cladding technology to deposit a high quality and erosion resistant protection shield on the leading edge of LP blades. The project has demonstrated the feasibility of in situ repair of turbine blades in trials conducted at a power station using a fibre delivered diode laser and a robot. A company, Hardwear Pty Ltd, was established in late 2005 to commercialise this technology and has to date carried out successfully several commercial contracts involving the repair of 340 LP blades.     

消除汽轮机叶片围带焊接裂纹的误判

汽轮机叶片围带焊接后进行磁粉探伤时出现伪磁痕,造成焊接区存在裂纹的假象和误判。本文用成分—金相组织—物理性能方法进行综合分析,找到了误判的原因。指出汽轮机叶片围带焊后检测焊缝时避免焊接裂纹误判的正确探伤方法。     

冲击式水轮机转轮裂纹焊接修复

介绍了采用低匹配的奥氏体不锈钢焊条，在能整体不预热和焊后热处理条件下，现场手工电弧焊进行马氏体不锈钢转轮的裂纹焊补修复，修复质量经渗透探伤检验达到了要求。     

Recent developments in repair welding technologies in Japan

Abstract

Developments in some difficult repair welding technologies in Japan during the past decade are reviewed. The topics covered include the repair welding of bridges in service, the temper bead method which makes it possible to omit post-weld heat treatment (PWHT) of repaired pressure vessels, the seal welding of a reactor vessel in which stress corrosion cracks were detected, low heat input repair welding of neutron irradiated stainless steel and nickel based alloys, the prevention of solidification cracking in repair welding of aged heat resistant cast steels, the development of welding materials for the mending of single crystal nickel based superalloy turbine blades, underwater repair welding of nuclear reactors, the reduction of residual stresses in repair welding, and an ultrasonic testing method for nickel based weld metals. The local PWHT of creep resistant ferritic steel tubes is also reviewed.     

Laser Treatment of Textured X20Cr13 Stainless Steel to Improve Water Droplet Erosion Resistance of LPST Blades and LP Bypass Valves

X20Cr13, a martensitic stainless steel, is commonly used for the manufacture of low pressure steam turbine (LPST) moving blades and LP bypass valves of fossil fuel and nuclear power plants. The LPST blades, at present, are laser surface treated to improve their water droplet erosion (WDE) resistance. The laser-treated X20Cr13 stainless steel has improved the water droplet resistance (WDER) several times compared to untreated ones. Further improvements are being carried out by providing a carbide-based HVOF coating having appropriate surface roughness or by creating textured surfaces and treating with a high power diode laser. The surfaces, having appropriate roughness, absorb more laser energy, resulting in improved microstructure, microhardness, modified ultimate resilience, and thicker hardened layer. The WDER of laser-treated textured X20Cr13 stainless steel has improved significantly compared to the untextured ones. The WDE test results of laser-treated textured and untextured X20Cr13 stainless steel along with their microhardness, modified ultimate resilience, microstructure, SEM, and XRD analysis are discussed and reported in this paper. The laser-treated textured X20Cr13 stainless steel is highly suitable for LP bypass valves and LPST blades for achieving a thicker hardened layer with lesser heat input to the components.     

激光和TIG堆焊钴基合金的性能

为了提高马氏体不锈钢蒸汽涡轮叶片的性能,采用Nd:YAG激光、CO₂激光、半导体激光和TIG堆焊方法,在12%Cr马氏体不锈钢表面堆焊了钴基合金粉末(Stellite-6).通过X射线衍射分析、电子探针分析、能谱分析和耐磨试验,研究了堆焊层的形状、稀释率、维氏硬度、DAS(枝晶间距)值、显微组织和耐磨性能,并比较了不同堆焊方法的特点.与TIG堆焊相比,激光堆焊方法的堆焊层具有更小的稀释率、细小的显微组织、狭窄的热影响区、高的维氏硬度、优良的耐磨性、高的钴含量和低的铁含量的特点.     

纳米SiC粉体对铸造超低碳马氏体不锈钢耐磨蚀性能的影响

水轮机用铸造超低碳马氏体不锈钢遭受着泥砂冲刷和腐蚀的双重作用.在生产条件下将经过表面改性处理的纳米SiC粉体加入到铸造超低碳马氏体不锈钢中,分别在加与不加NaCl的两种水砂粒介质中进行磨蚀试验,研究纳米SiC粉体加入量对其耐磨蚀性能的影响.结果表明:纳米SiC粉体强化处理后马氏体不锈钢表现出优越的耐磨蚀性能,其材料失重形式主要为韧性断裂,当SiC加入量为0.1％时,在水砂粒和3.5％NaCl水砂粒中磨蚀率分别降低了90％和86％.     

活性气体对马氏体不锈钢MAG焊熔敷金属性能的影响

针对大型水轮机转轮用ＺＧ０Ｃｒ１３Ｎｉ５Ｍｏ高强马氏体不锈钢的熔化极气体保护焊工艺，研究了活性气体对焊丝ＨＳ３６７Ｌ和ＨＳ１３５Ｌ熔敷金属化学万分的力学性能的影响。     

气轮机隔板埋铸叶片断裂分析

供助光学显微镜，扫描电镜等手段，对用埋铸法生产的T9815气轮机组隔板断裂部位的金相组织特征，宏观和微观断口形貌等进行了研究，结果表明：由于高温铁水对叶片铸入部位的冲刷，增强作用，使不锈钢铸铁化进而使叶片铸入部位强度降低，在拉应力的作用下导致叶片铸入部位开裂。     

304不锈钢焊接管开裂原因分析

利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDX)和显微维氏硬度计对某开裂的不锈钢焊接管进行了失效原因分析。结果表明,该不锈钢管局部补焊区域存在残余应力,补焊造成附近组织晶界敏化,协同环境中存在S离子和Cl离子等腐蚀性介质,故在补焊位置发生应力腐蚀沿晶开裂。     

Advanced manufacturing technologies of large martensitic stainless steel castings with ultra low carbon and high cleanliness

The key manufacturing technologies associated with composition,microstructure,mechanical properties,casting quality and key process control for large martensitic stainless steel castings are involved in this paper.The achievements fully satisfied the technical requirements of the large 700 MW stainless steel hydraulic turbine runner for the Three Gorges Hydropower Station,and become the major technical support for the design and manufacture of the largest 700 MW hydraulic turbine generator unit in the world developed through our own efforts.The characteristics of a new high yield to tensile strength (Rp0 2/Rm) ratio and high obdurability martensitic stainless steel with ultra low carbon and high cleanliness are also described.Over the next ten years,the large martensitic stainless steel castings and advanced manufacturing technologies will see a huge demand in clean energy industry such as nuclear power,hydraulic power at home and abroad.Therefore,the new high yield o tensile strength (Rp0.2/Rm) ratio and high obdurability martensitic stainless steel materials,the fast and flexible manufacturing technologies of large size castings,and new environment friendly sustainable process will face new challenges and opportunities.     

T91/TP347HFG异种钢焊接接头裂纹原因分析

火电厂高温过热器用T91+TP347HFG异种钢焊接接头运行时,发生开裂泄露。分别从未开裂和开裂部分的焊接接头处取样,采用金相显微镜、扫描电镜、显微硬度计等对焊接接头试样进行检测和对比研究,分析其开裂原因。结果表明:焊接和焊后热处理工艺不当导致T91侧热影响区位置在整个焊接接头区域脆性较大,并有淬硬倾向比较大的组织出现;同时由于焊接规范参数较大而导致焊接热影响区较宽,在一定应力下的作用导致裂纹从此处萌生和扩展,最终导致该异种钢焊接接头开裂失效。     

某燃气轮机压气机Ⅰ级叶片断裂失效分析

对某燃气轮机压气机断裂的马氏体不锈钢ASTM403叶片进行了宏观检查、化学成份分析、硬度测试、断口分析(体视显微镜和扫描电镜分析)、微观金相组织检验分析、扫描电镜和能谱分析,通过以上各项实验的综合分析并结合叶片运行工况特点,得出叶片断裂的主要原因是烟气颗粒对叶身冲蚀形成的点状凹坑缺陷在交变应力的作用下所引起的低周疲劳开裂.     

Processing and microstructure of investment casting turbine blade NITAC in-situ composites

Directional solidification was used to produce turbine blades by the Bridgman method. NITAC alloys with various carbon contents were investigated; the optimum range was found to be 0.40 to 0.48%. Within this range, except for the blade locking piece edges, the blade structure consisted predominantly of aligned eutectics. The in- situ eutectics were aligned tantalum fibers embedded in a γ- phase matrix. The blades were produced using an alloy displacement rate of 1.86 x 10 ^{- 6} m/s. Measurements of fiber spacings along the blade height indicated that the rate of displacement of the solidification front exhibited some variations. These variations were closely associated with dimensional changes in the turbine blade cross sections.     

SA335 P91材料的埋弧焊

为提高SA335 P91钢的焊接效率，进行了P91埋弧焊和焊条电弧焊2种焊接方法的比较，并确定了P91材料埋弧焊的试验方案。通过试验，对P91埋弧焊的焊材选用、道间温度和热输入控制及焊后热处理进行了研究，确定了埋弧焊采用英国曼彻特和德国蒂森的焯接材料，采用正火＋回火或整体回火工艺，解决了焊缝冲击吸收功偏低的问题，并在生产上得到应用，生产效率提高了2倍以上。