焊接接头韧度CTOD评定的适用性与允许值研究

对厚钢板两种焊接工艺焊接接头中的焊缝材料和热影响区材料进行拉伸试验。发现各自的拉伸曲线都可视为理想弹塑性，符合Wells提出裂纹尖端张开位移（crack tip opening displacemem，CTOD）理论的假设条件。因此，证明CTOD试验评定焊接接头韧度的适用性。提出确定钢结构焊接接头CTOD允许值的“母材参考法”和“类比法”，为在钢结构的设计和建造中合理地确定焊接接头韧度指标提供方法。     

X65管线钢焊接接头低温韧性及安全评定的研究

研究了API5LX65海底管线钢焊接接头的力学性能和低温断裂韧度。采用欧共体提出的SINTAP方法，对焊趾处含有表面裂纹的X65管线钢焊接接头进行了安全评定。根据ISO标准(BS7448)，以裂纹尖端张开位移(CTOD)作为断裂韧度参量，测定了管线钢焊接接头0℃时的断裂韧度。对于热影响区试样，对其进行剖面金相显微组织分析，判断裂纹尖端是否落在粗晶区，确保试验结果的有效性及可靠性。根据全焊缝拉伸试验结果，建立了X65管线钢焊接接头焊缝的一级、三级评定曲线。     

POP-IN效应对材料断裂韧度的影响及评价

裂纹尖端张开位移占是衡量材料断裂韧度的一个重要参量，但在进行C3DD（crack tip opening displacement）试验时，F-V曲线上通常会出现瞬间的载荷迅速下降、位移增加很小的“突进”现象，俗称“POP-IN”，它的出现对确定CTOD值产生很大影响，进而影响到材料断裂韧度评价的准确性。针对这一问题，文中依据BS7448 PartⅡ中的有关评定标准，结合EH36钢埋弧焊接头CTOD试验，分别对均质、非均质材料中存在POP-IN现象时如何正确评定进行论述，力网为合理取舍POP-IN效应、准确评价材料断裂韧度提供依据。     

X70钢临界CTOD值ANSYS计算

随着海洋工程的发展,探索海洋油气的项目增多,天然气、石油的输送工程也日渐发展起来。UOE生产工艺下的高强X70钢被广泛运用到油气输运工程中,然后强度越高的钢其断裂韧度越低,需对这种高强钢的断裂韧度值进行确定。材料断裂韧度大小可以用临界裂纹尖端张开位移CTOD(crack tipopening displacement)来度量。临界CTOD是弹塑性断裂力学中重要的参数,其大小直接反映了裂纹尖端材料抵抗开裂的能力,临界CTOD值越大表示材料抗开裂性能越好,反之抗开裂性能越差,确定临界CTOD值意义重大。首先依据BS7448规范对X70钢断裂韧度临界CTOD值进行了测试,然后利用Ansys软件从CTOD定义出发对X70钢临界CTOD进行了计算,实现了试验与模拟的对比分析,可供压力容器和管道生产和结构安全性评估企业借鉴。     

温度及显微组织对30A钢断裂韧度的影响

用三点弯曲试样通过系列温度下的裂纹尖端张开位移(COD)试验，研究了温度对30A钢断裂韧度的影响。同时采用透射电镜(TEM)分析研究了30A钢在不同热处理制度下的显微组织结构特征，得出了温度、显微组织对30A钢断裂韧度的影响规律。     

高压气瓶母材、焊缝和热影响区的平面应变断裂韧度实验研究

通过军用高压气瓶母材、焊缝和热影响区的临界裂纹张开位移试验实验 ,研究了高压气瓶的断裂薄弱环节、平面应变断裂韧度及其参数的分布 ,给出了该部位的平面应变断裂韧度和平面应变断裂韧度对数的分布函数 ,为军用高压气瓶安全性和可靠性评估奠定了实验基础     

湘钢低焊接裂纹敏感性X610CF钢性能及工程应用

研究了低焊接裂纹敏感性07MnCrMoVR钢（简称X610CF钢）的力学性能、组织结构及其工程应用。通过对40mm厚钢板进行低温（-50℃）裂纹尖端张开位移试验（CTOD）,得出其a为0.12mm;在应变量为5％的情况下KK（-50℃）最低为260J,且时效敏感系数为14．6％。通过调质处理得出,X610CF系列钢在650～680℃时回火,保温时间（min）为钢板厚度的2．5～3倍时,可以得到最佳的强韧性匹配。结果表明,该钢具有较低的应变时效敏感性、优异的焊接性能和低温韧性,并且铜板的厚度≤50mm时焊前可不预热或稍加预热而不产生焊接冷裂纹,是制造大型压力容器（特别是低温和常温球罐）、水电站压力钢管的理想用材。     

铝合金焊接接头的低温断裂性能COD研究

为研究2A14T6铝合金焊接接头(焊缝/熔合线/热影响区/母材)的低温(77 K/4.2 K)断裂韧度,文中采用三点弯曲法,通过自主研制的低温位移传感器及力学测试系统,得到重要的低温裂纹张开位移(crack-tip opening displacement,COD)性能参数,并结合断口的微观结构具体分析形貌与断裂韧度的关系.研究结果表明,该测试系统能有效测量材料的低温裂纹张开位移参数δ;低温下断裂韧度为热影响区>母材>熔合线>焊缝;对低温断口的微观形貌观察显示,韧窝大而深的微观结构对应低温抵抗裂纹开裂能力强、韧性好.     

全焊接阀体管线球阀焊接接头的安全评估

介绍了一种评价焊接接头安全性的方法——裂纹尖端张开位移（CTOD）断裂韧性试验方法,根据CTOD试验值,对埋弧焊焊接接头免焊后热处理的可能性进行安全评定。为大型全焊接阀体管线球阀制造提供科学依据。     

用于高韧性材料Ⅰ—Ⅱ复合型断裂的多剖面法

本文根据韧性金属的断裂机理和裂纹尖端延伸区尺寸与断裂参量的关系提出了适用于高韧性材料Ⅰ—Ⅱ复合型断裂问题的多剖面法,可用来同时确定裂纹断裂角和裂纹尖端张开位移矢量的启裂值。本文用这种方法进行了双轴受载含倾斜裂纹的16MnR钢十字形试件的复合型位移断裂参量的测试。     

Some investigations on microstructure and mechanical properties of submerged arc welded HSLA steel joints

This paper investigates the influence of the submerged arc welding (SAW) process parameters (welding current and welding speed) on the microstructure, hardness, and toughness of HSLA steel weld joints. Attempts have also been made to analyze the results on the basis of the heat input. The SAW process was used for the welding of 16 mm thick HSLA steel plates. The weld joints were prepared using comparatively high heat input (3.0 to 6.3 KJ/mm) by varying welding current (500–700 A) and welding speed (200–300 mm/min). Results showed that the increase in heat input coarsens the grain structure both in the weld metal and heat affected zone (HAZ). The hardness has been found to vary from the weld centre line to base metal and peak hardness was found in the HAZ. The hardness of the weld metal was largely uniform. The hardness reduced with the increase in welding current and reduction in welding speed (increasing heat input) while the toughness showed mixed trend. The increase in welding current from 500 A to 600 A at a given welding speed (200 mm/min or 300 mm/min) increased toughness and further increase in welding current up to 700 A lowered the toughness. Scanning electron microscopy of the fractured surfaces of impact test specimen was carried out to study the fracture modes. Electron probe micro analysis (EPMA) was carried out to investigate the variation in wt.% of different elements in the weld metal and HAZ.     

Multi sensor data fusion for improving performance and reliability of fully automatic welding system

This paper presents a new generation of system for pressure vessel and shipbuilding. Typical pressure vessel and ship building weld joint preparations are either traditional V, butt, fillet grooves or have narrow or semi narrow gap profiles. The fillet and U groove are prevalently used in heavy industries and shipbuilding to melt and join the parts. Since the wall thickness can be up to 6 in. or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional processes such as submerged arc welding (SAW) and flux cored arc welding (FCAW) can be many hours. Although SAW and FCAW are normally mechanized processes, pressure vessel and ship structures welding up to now have usually been controlled by a full time operator. The operator has typically been responsible for positioning each individual weld run, for setting weld process parameters, for maintaining flux and wire levels, for removing slag and so on. The aim of the system is to develop a high speed welding system with multi-torch for increasing the production speed on the line and to remove the need for the operator so that the system can run automatically for the complete multi-torch multi-layer weld. To achieve this, a laser vision sensor and a special image processing algorithm have been made. Also, the multi-torch welding system can be applicable for fine grained steel because of the high welding speed and lower heat input compared to a conventional welding process.     

Weldability of Copper-bearing Aging Steel

The weldability of copper-bearing aging steel is evaluated using calculated cracking susceptibility index Pcm,oblique Y-groove cracking test,heat-affected zone (HAZ) maximum hardness measurement,submerged arc welding (SAW) test and gas metal arc welding (GMAW) test.The results show that this copper-bearing aging steel has low hardenability and cold cracking susceptibility.SAW test of 40 mm thick plate with WS03 wire matched by CHF101 flux reveals that the welded joints obtain high strength and good impact toughness at low temperature.The HAZ has no hardening but there exists a slightly softening phenomenon.Thus,line energy should be limited or controlled strictly to avoid softening behavior in HAZ during SAW.GMAW tests of 12mm and 24mm thick plates using WER70NH wire show that the tensile strength of joints reaches 720MPa,higher than the stipulated strength requirement of base metal.The average impact energy at-40℃ in the welded joints is more than 140J exceeding minimum stipulated requirement by a wide margin.There are no hardening and softening behaviors in the heat-affected zones of GMAW.All weld metals exhibit acicular ferrite (AF) plus small amount of proeutectoid ferrite (PF) structure,of which the former can significantly improve impact toughness of weld metal.The predominant microstructure in coarse grain HAZ is bainite.     

Welding of thin sheet of Al alloy (6082) by using Vario wire DC P-GMAW

This paper describes an investigation on the micro-structure, weld bead geometry, dilution rate and mechanical properties of the butt and overlap weld joints of 1-mm-thick 6082 aluminium alloy sheet. Weld joints were produced with the help of a variant of gas metal arc welding (GMAW) process, i.e. direct current-pulsed GMAW (DC P-GMAW), using a Vario wire. The capability of the new process has been assessed in terms of dilution, weld bead geometry, mechanical properties and porosity. The welding results with this new process showed good process stability in the welding of thin sheets of aluminium, while weld mismatch was found to increase with an increase in heat input. Weld bead geometry parameters such as weld size, throat and weld convexity increases with the increase in heat input. The dilution in case of lap joints (10–25%) was less than that of butt joints (60–80%). The increase in factor Φ (summarizing the effect of pulse parameters) increases the form factor and lowers the toe angle. Mechanical properties of the welds are poor as the tensile strength of 6082 alloy welds was around 150 MPa, and the percent elongation was about 1.3%, and it was primarily due to high porosity. Porosity (%) in weld joints was found in the range of 0.33–11.59%. The porosity is a major issue with DC P-GMAW welds.     

Effect of temperature on the charpy impact and CTOD values of type 304 stainless steel pipeline for LNG transmission

Stainless steel pipe of type 304 the with a wall thickness of 26.9 mm and the outer diameter 406.4 mm is welded by manual arc welding process. Mechanical properties and fracture toughness of type 304 stainless steel are investigated in the temperature ranging from room temperature to — 162°C. The results obtained are summarized as follows. The tensile strength noticeably increases as the temperature becomes lower while the yield strength is relatively insensitive to temperature. The Charpy impact energy and CTOD values become higher in the case that crack propagation direction is aligned to the transverse axis upon the rolling direction than longitudinal direction. The drop of fracture toughness is associated with the noticeable diminution of plastic component as temperature seduces from room temperature to — 162°C.     

15MnVNq钢埋弧焊焊缝强韧性研究

介绍几种焊丝与焊剂对１５ＭｎＶＮｑ桥梁钢埋弧自动焊焊缝强度与韧性的影响规律，经试验研究筛选出能够满足技术标准要求的焊接材料。研究成果解决了长期存在的九江长江大桥１５ＭｎＶＮｑ钢焊缝强度过高、韧性偏低的问题。     

氩气保护对埋弧焊焊缝氧氮含量和冲击韧性的影响

高洁净度钢铁材料的出现给埋弧焊焊缝金属的纯净度提出了挑战，而且焊缝金属中氧、氮含量偏高，严重地损害了接头的韧性。研究了在埋弧焊过程中采用氩气保护对焊缝氧，氮含量和冲击韧性的影响。结果表明，采用氮气保护使焊缝金属中的氮含量减少，而对氧含量的影响则不大，低温冲击试验表明，用氮气保护使埋弧焊接头的冲击韧性提高近50%。     

预应变对管线钢低温断裂韧度影响研究

油气管线无论是在安装还是在服役过程中,都会不可避免地产生大塑性应变(即预应变).为了研究预应变对材料力学性能和断裂韧度的影响,对X80管线钢原材料和塑性变形材料分别进行不同温度下的拉伸试验和断裂韧度试验,并对试样断口形貌进行分析.试验结果表明,温度对管线钢的断裂韧度具有显著作用,钢材的断裂韧度随着温度的降低显著减小,断裂方式也由延性断裂转变为脆性断裂;拉伸预应变因工作硬化提高了钢材的屈服强度与抗拉强度,而压缩预应变因包申格效应降低了钢材的屈服强度与抗拉强度,但两者都降低了钢材的塑性及断裂韧度,进一步增加脆性断裂发生的概率.因此,在管道设计、选材、安全分析及评定时,应充分考虑温度和预应变对管线钢断裂行为的影响.     

Selection of welding process for hardfacing on carbon steels based on quantitative and qualitative factors

Weld hardfacing techniques are employed mainly to extend or improve the service life of engineering components either by rebuilding or by fabricating in such a way as to produce a composite wall section to combat wear, erosion, corrosion, etc. In this paper, an attempt has been made to determine the best welding process to hardface boiler grade steels based on quantitative factors (by measuring percentage of dilution) and qualitative factors (using the analytic hierarchy process [AHP]). Five different welding processes including shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), and plasma transferred arc welding (PTAW) have been compared. Based on the quantitative and qualitative factors, the PTAW process is found to be the best method to hardface boiler grade steels.     

压力容器断裂韧度要求的预测

在弹塑性断裂双参数分析方法的基础上，导出了预测压力容器等重要工程结构断裂韧度ＣＴＯＤ要求的理论表达式。只要在实际结构服役条件下，材料断裂韧度高于该表达式要求的韧度值，就可防止结构的弹塑性断裂失效。同时，在该表达式中考虑了应力集中及焊接残余应力的影响，并表明断裂韧度要求随作用应力及板厚的增加而增加。最后给出了两个实例，以考核该理论表达式的实用性。