中国低活马氏体钢熔化焊接头硬度与微观组织

针对4 mm厚的中国低活马氏体钢,采用TIG焊接方法分别对预热和未预热两组试样进行了焊接和焊后回火处理,对焊接接头的硬度和微观组织结构进行了测试和观察.结果表明,焊缝区硬度值偏高,靠近母材的热影响区出现较窄的软化带;焊接接头金相组织为板条特征明显的回火马氏体组织,未预热试样的马氏体含量与预热试样相比较,两者之间没有明显的差异.在晶内和晶界处分布大量的碳化物,焊缝区为尺寸较小的棒状,母材和热影响区为尺寸较大的颗粒状,接头的组织和碳化物的析出对焊接接头的硬度有很大的影响.

Abstract：

The preheated and non-preheated 4 man China low activation martensitic steel (CLAM) plate were welded by TIG welding and post-weld heat treating, and the hardness and micrcstructure in welded joint were tested and observed. The results show that the hardness in the weld metal is higher and the softening band in the heat-affected zone (HAZ) closing to the base metal. The tempered lath martensite is observed in welded joints. There is no significant difference in martensite content between the preheated and non preheated weldments. A large amount of carbide particles are observed in the grains and at the grain boundary. The carbides are small rods in weld metal and large granular in the HAZ and base metal respectively. The mierostrueture and carbides in welded joints have great effect on the hardness.     

焊接热循环对10Ni5CrMoV钢组织的影响

采用模拟焊接热循环的方法，研究了不同峰温和ｔ８／５条件下１０Ｎｉ５ＣｒＭｏＶ钢热影响区组织的变化，金相观察发现，峰温在Ａｃ１～Ａｃ３之间时，其组织为细小的马氏体和高温回火马氏体的混合组织；峰温超过Ａｃ３时，冷却后均转变为马氏体，且发生自回火现象，峰温越高，奥氏体晶粒粗大，冷却后形成的马氏体板条束尺寸也越大，随着ｔ８／５的增加，其组织由自回火马氏体（含少量孪晶马氏体）自回火马氏体＋下贝氏体，自回火马     

HG785D高强钢焊接热影响区性能

文中主要研究了HG785D高强钢焊接接头热影响区性能,HG785D高强钢采用熔化极活性气体保护焊(80%Ar+20%CO₂)进行焊接.通过对焊缝及热影响区力学性能及显微组织分析.结果表明,热影响区冲击性能较低,同时硬度较高.且热影响焊缝金属组织由母材的回火索氏体转变为马氏体及上贝氏体,而在焊缝区,由于填充金属合金元素较多,组织为铁素体和粒状贝氏体,具有较好的韧性.在热影响区,由于马氏体及上贝氏体等硬脆相的存在使得热影响区淬硬性增强,脆性增大.     

Fracture toughness and microstructure of 780 MPa class high-tensile strength steel plates: improvement of steel structural performance by laser beam welding for mid-thick section steel plate

Fracture toughness and microstructure of laser weld metal of 780 MPa class steels are investigated and compared with those of SM490A and SM570Q.

In SM490A and SM570Q, Charpy energy transition temperature of laser weld metals is 60–90°C higher than that of base metal, and upper bainite microstructures are observed in the laser weld metals.

In 780 MPa class steels, difference of Charpy energy transition temperatures between laser weld metal and base metal are only 10–30°C, and no upper bainite microstructures are observed in the laser weld metals. Hardness of the laser weld metals of 780 MPa class steels is identical to that of martensite microstructure. A superior toughness of the laser weld metal of 780 MPa class steels would be owing to the martensite microstructure resulted from a high carbon equivalent.     

Corrosion behaviour of weld heat affected zone of aluminium alloy 7075

Abstract

The microstructure of the weld heat affected zone (HAZ) of alloy 7075 was simulated using a Gleeble system. The corrosion behaviour of several locations in the weld HAZ was investigated by means of differential scanning calorimetry, electrochemical measurement in 3·5 wt-%NaCl solution, and exfoliation corrosion tests. Different exfoliation corrosion morphologies for the base metal and weld HAZ were also observed. The corrosion morphology of the weld HAZ was mainly related to the degree of precipitation of η' phase in the matrix. The HAZ in the region of the peak temperature 377° C contained the most precipitation of η phase, but no effect on corrosion morphology as a result of T6 post-weld heat treatment was observed.     

High-Temperature Corrosion Behavior in Different Regions of 9 Cr-1 Mo Steel Weldment in SO2 + O2 Atmosphere

This paper investigates the high-temperature corrosion behavior of microstructurally different regions of the weldment of 9 Cr-1 Mo steel used in thermal power plant boiler in SO₂ + O₂ environment. The weldment is produced by tungsten inert gas welding method, and the different regions of the weldment (weld metal, heat-affected zone, and base metal) are exposed in SO₂ + O₂ (ratio 2:1) environment at 973 K for 120 h. The reaction kinetics and corrosion growth rate of different regions of weldment in isothermal condition are evaluated. The post corroded scales of the different specimens are studied in SEM, EDS, and XRD. The results indicate that the weld metal shows higher corrosion rate followed by HAZ and base metal. The higher rate of corrosion of weldmetal is mainly attributed to the least protective inner scale of Cr₂O₃ with minimum Cr Content. This is due to the formation of delta ferrite, which leads to the precipitation of the Cr-based secondary phases and depletes the free Cr from the matrix. The thermal cycles during welding at high temperature are favorable for the formation of delta ferrite. On the other hand, in absence of delta ferrite, the base metal and HAZ regions of the weldment show lower corrosion rate than weld metal. The difference in corrosion rate in the three regions of the weldment is supplemented by post-corroded scale characterizations.     

Microstructures and mechanical properties in laser beam welds of titanium matrix composites

Laser beam welding (LBW) was used to 2 mm thick titanium matrix composites (TMCs) sheets and microstructure, hardness and tensile properties of butt joints were studied. Welded joints without defects were obtained indicating that LBW is a suitable processing method for TMCs. The results reveal that the fusion zone completely consists of α′ martensite causing an increase of more 27% in hardness compared with that of base metal. The heat affected zone consists of a mixture of α′ martensite and primary α phases. Large gradients of microstructures and hardness are found over the narrow heat affected zone dependent on the β-transus temperature during weld cooling. TiB_w with smaller sizes redistribute at grain boundaries in the weld. The joints show excellent strength and they can reach the full strength compared with the base metal with sound welding parameters, which is ascribed to the presence of α′ martensite and refinement of TiB_w in the weld.     

马氏体和奥氏体不锈钢TIG焊端接接头失效分析

针对船舶设备采用的马氏体和奥氏体不锈钢钨极氩弧焊焊接接头的泄漏问题,采用光学显微镜和扫描电镜观察、显微硬度测定等方法,分析了1Cr17Ni2马氏体不锈钢和1Cr18Ni9Ti奥氏体不锈钢焊接接头各个区域的组织变化和硬度分布.结果表明,在1Cr17Ni2一侧的热影响区紧邻焊缝部位,铁素体受热作用明显长大,显微硬度较低,在热影响区的较高温度区,快冷得到高硬度马氏体,该区断口呈典型的解理与准解理脆性断口,成为焊接接头的薄弱地带,容易产生裂纹导致泄漏.还分析了接头失效的其它原因并提出了改进措施.     

Effect of nitrogen on microstructure and corrosion resistance of Cr15 super martensitic stainless steel

ABSTRACT

To investigate the influence of nitrogen on structure and corrosion resistance of Cr15 super martensitic stainless steels (SMSS), two types (N-free and N-0.12%) of specimens were quenched at 1050°C and tempered at different temperatures, and then, optical microscope, transmission electron microscopy, X-ray diffraction, potentiodynamic polarisation, immersion experiments and Kelvin Probe Force Microscope were used to characterize its microstructures and corrosion properties. The experimental results show that the microstructure in the N-free Cr15 super martensitic stainless steel is a biphasic tissue with alternating martensite and austenite distribution while quenched at 1050°C and tempered between 600 and 700°C. The nitrogen addition increases the content of austenite, and changes the austenite morphology significantly into the coarse block and strip distribution. What’s more, micro-galvanic corrosion is formed between austenite and martensite, which deteriorates the corrosion resistance of the SMSS.     

Microstructure and corrosion resistance of radial friction welded supermartensitic stainless steels

In this work, supermartensitic stainless steel pipes were radial friction (RF) welded and their corrosion behaviours were studied based on potentiodynamic polarisation and double-loop electrochemical potentiokinetic reactivation tests. Measurements were performed on samples taken from the base metal (BM), weld interface and consumable ring (CR) of the RF weldment. The corrosion properties are discussed in terms of their resulting metallurgical microstructure. The precipitation of Cr carbides that takes place during the tempering treatment induces a substantial Cr depletion value (I_r/I_a = 54.22%). On the other hand, CR and weld interface regions, which had their microstructure transformed and their Cr carbide precipitates redissolved by the RF welding thermomechanical cycle, present a low level of Cr depletion (I_r/I_a < 1%). The AC microstructure, which is composed of a mixture of virgin martensite and stable retained austenite, presents an increase in pitting corrosion resistance compared to the tempered structure of the BM region. It was also observed that the δ-ferrite decreases the pitting resistance of the weld interface region.     

Microelectrochemical corrosion study of super martensitic welds in chloride-containing media

Pitting corrosion was studied in welded joints of supermartensitic stainless steels. The electrochemical behavior of three different weldment zones (weld metal (WM), parent metal (PM) and heat affected zone (HAZ)) was characterized independently using an electrochemical minicell through potentiodynamic and potentiostatic techniques. The minicell design selected for this work has the additional advantage of showing promise for service application. Macro-electrochemical characterization was also used to provide a basis for comparison and check the effectiveness of minicell techniques in characterizing the corrosion resistance of welded super martensitic stainless steels. Minicell experiments exhibit a great capacity to discriminate between the different welding zones. The electrochemical response can be correlated with the microstructure of the different zones. Thermal cycles resulting from the welding procedure do not have an important effect on the amount of retained austenite or on the values of the pitting potential E_P in the HAZ.     

G115钢CMT + P焊接工艺及组织和性能

基于冷金属过渡加脉冲(CMT + P)的焊接方法,研究了新型回火马氏体耐热钢G115的焊接性以及焊接接头组织和性能. 结果表明,焊接接头经热处理后为回火马氏体组织,焊缝晶粒呈现出等轴晶和柱状晶两种不同的形貌,而焊接热影响区和母材晶粒均为等轴晶. 与焊条电弧焊(SMAW)相比,CMT + P焊接方法有效降低了热输入,大幅度减小了热影响区宽度,提高了焊接接头的拉伸性能和热影响区冲击韧性,焊接接头焊缝冲击韧性略有降低. 焊接接头的室温和高温拉伸断裂机理均为韧性断裂,室温拉伸断口的韧窝内存在一定量的析出相.     

Cr5Mo钢管及其焊接接头长期服役后的组织性能与剩余寿命

本文研究了炼油厂铂重整装置临氢系统Cr5Mo耐热钢管及其焊接接头长期服役后的显微组织、力学性能和剩余寿命。试验结果表明,母材的组织和性能变化较小,估计还可继续使用10万小时。焊接热影响区的过热区已由马氏体转变为回火屈氏体,熔合线焊缝侧的类马氏体也已发生了回火,并在熔合线附近出现了增碳层。焊接接头的室温和高温瞬时强度高于母材,但其塑性韧性均较低,是裂纹萌生和扩展的薄弱部位,需加强运行监督。     

800 MPa级高强钢焊缝金属热处理组织与性能

在10Ni5CrMoV高强结构钢焊接中,为了获得良好的强韧性匹配,焊后需要进行热处理来改善焊缝金属的组织和性能.试验采用富氩气体保护焊焊接10Ni5CrMoV钢,分析了不同调质热处理工艺下焊缝组织、性能的变化规律.结果表明,焊缝金属焊态的组织主要是贝氏体、少量马氏体和残余奥氏体组织,调质热处理后焊缝组织主要为回火马氏体,随着回火温度的升高,焊缝中残余奥氏体减少,马氏体中碳化物析出长大并有球化趋势.调质态焊缝金属的强度随着回火温度的升高而逐渐降低,而韧性随着回火温度的升高而显著提高.     

新型9Cr-1Mo钢搅拌摩擦焊接头组织及性能

采用钨铼合金搅拌工具对新型9Cr-1Mo钢进行搅拌摩擦焊工艺试验,探讨焊缝成形、组织及性能变化规律. 结果表明,在300和400 r/min的转速,50 mm/min的焊接速度下可获得无缺陷接头;焊缝主要由搅拌区和热力影响区组成,具有明显的马氏体淬硬组织特征;高温热影响区为淬硬马氏体和回火马氏体混合组织,低温热影响区为过回火马氏体组织. 焊缝区具有晶粒细化特征,其晶粒尺寸约为母材69.2%. 焊缝区产生明显硬化,最高硬度约为母材硬度值的2.0倍. 焊接接头抗拉强度达到母材98%以上,搅拌区和热影响区冲击吸收能量分别达到母材的77.8%和87.4%,表明搅拌摩擦焊接头仍具有较好强韧匹配.     

Effects of B on microstructure and hardenability of resistance seam welded HSLA linepipe steel

Abstract

The effects of B on the microstructural and mechanical characteristics of resistance seam welded high strength low alloy linepipe steel were investigated at different regions, such as weld, heat affected zone (HAZ) and base. Because most of the solute B atoms were already precipitated as iron borocarbides and iron borides in as welded steels, the improved hardenability was not observed regardless of the observed regions. The amount of dissolved B precipitates increased with austenitising temperature, and the pre-existing B precipitates were fully dissolved at 950°C for 180 s. The segregation of solute B atoms into austenite grain boundaries was more marked at higher austenitising temperatures, and the segregated solute B atoms greatly increased the hardenability of the austenitised pipes, resulting in hard microstructures like bainite and martensite. The B addition also effectively compensated for the deteriorated hardness at the weld and HAZ of the tempered specimens, although B atoms were precipitated during tempering.     

聚变堆用CLAM钢激光焊接接头显微组织及性能

对聚变堆用CLAM钢进行了激光焊接试验,并对接头进行740℃/1 h焊后回火处理,分别对热处理前、后接头的显微组织及性能进行了研究.结果表明,获得了成形良好、无缺陷的焊接接头;焊态下,焊缝由淬硬的板条马氏体和大量的δ铁素体组织组成.完全淬火区由板条马氏体和极少量的δ铁素体组成,其硬度高达545 HV;焊后热处理使焊缝及完全淬火区的板条马氏体分别转变为碳化物弥散分布的回火马氏体和回火索氏体组织.显著降低了接头的淬硬程度,最大硬度仅比母材高约15%;焊后回火热处理前、后接头的抗拉强度均高于基体母材,虽然焊后热处理使接头强度有所降低,但仍达到原始母材的98%以上.     

不同热处理状态AMS6308钢惯性摩擦焊接头组织及力学性能

在HWI-IFW-130型轴/径向多功能惯性摩擦焊机上,成功实现热轧态与热轧态AMS6308钢、淬火+回火态与淬火+回火态AMS6308钢惯性摩擦焊接. 对两种不同热处理状态的焊接接头进行检测分析. 结果表明,母材为热轧态的焊接接头,焊缝区为马氏体组织,热力影响区和热影响区为马氏体+贝氏体组织;母材为淬火+回火态的焊接接头,焊缝区为马氏体组织,热力影响区和热影响区为马氏体回火组织. 以焊缝为中心,显微维氏硬度呈对称分布,焊缝区显微维氏硬度最高;两种不同热处理状态母材获得的焊接接头,拉伸均断于母材.     

Structural evolution of pulsed Nd-YAG laser welds of AISI 1006 steel

Abstract

Although correlations of welding parameters with the metallurgical features of conventional fusion welds in low carbon steels are well established, information on process–structure–property relationships associated with pulsed laser welds is more limited. This paper presents results on the characterisation of weld metal and heat affected zone (HAZ) microstructures observed in laser welded AISI 1006 steel. Pulsed Nd-YAG laser welds in the bead on plate configuration were used for this purpose, both in overlapping and non-overlapping bead configurations. As very rapid heating and cooling cycles occur during laser welding, the microstructures observed in the weld metal are the result of rapid solidification producing thin columnar austenite grains extending from the fusion boundary, which transform to martensite and bainite during fast cooling to ambient temperature. The HAZ structure in the base plate can also be rationalised in terms of the rapid thermal cycling experienced. The HAZ is narrow with the intercritical reheated subzone being dominant. As microstructural development has a critical effect on the mechanical properties of welds, microstructural characterisation plays an integral role not only in the understanding of pulsed laser welding, but also in the selection of optimum welding conditions for the material of interest.     

核电SA508-3钢焊接连续冷却转变曲线的分析

针对首次应用到核电上的SA508-3钢,在Gleeblei500D热模拟机上,采用膨胀法测定了SH-CCT曲线,获得了焊接工艺特征参数t8/5从3.75～20 000 s范围内的焊接热影响区组织变化规律.结果表明,获得全部马氏体相变的冷却时间为15 s,全部贝氏体相变的冷却时间60 8＜t8/5≤3 000 s,全部铁素体和珠光体相变的冷却时间为6000 s;当t8/5≤100 s时,焊接热影响区硬度高于350 HV,存在淬硬和裂纹敏感性;当t8/5≥20 000 B时,焊接热影响区硬度小于母材硬度,易出现软化现象.