An initial study on welding procedure using tandem MIG welding of high strength aluminum alloy

The high-speed camera system and data acquisition system of welding parameters were created in tandem MIG welding of high strength aluminum alloy. The experiments were carried out in order to obtain the photos of droplet transfer under different welding parameters in pulsed mode. The droplet transfer mode of “one pulse one droplet” becomes the preferred selection during welding process because of its stable procedure and sound weld form. The parameter ranges for corresponding transfer mode were experimentally achieved, among which the stable droplet transfer mode of “one pulse one droplet” can be realized. These efforts brave the way for control weld heat input and weld formation in the future.

Investigation on welding procedures for in-service pipelines

Some research results are given in this paper about burnthrough and hydrogen cracking with a flowing chamber and a loop. Many factors including plate thickness, running rate, heat input and so forth have been studied. By experiments it can be found that occurrence of hydrogen cracking can be effectively reduced by properly increasing heat input and using the tempering bead technique.

Girth welding procedure and weldability evaluation of coal seam gas transmission UOE pipeline

According to the requirements of Queensland Gas Company Ltd. （QGC）, the operator of the Queensland Curtis LNG （QCLNG） pipeline project in Australia, girth welding experiments and weldability evaluations have been carded out for three X70 UOE pipes from Baosteel based on API 1104 standards. Shielded metal arc welding （SMAW） and gas- shielded flux-cored wire arc welding （FCAW-G） have been applied, and the girth weld joint quality and mechanical performance were evaluated. It was found that the field girth weldability of Baosteel＇ s XT0 UOE pipes was excellent under the conditions used here and satisfied the requirements of the QCLNG project for field girth welding construction. Furthermore,Baosteel has offered a solution to the QCLNG project for pipeline girth welding in which the girth welding joint design, selection of welding processes and consumables, welding procedures, techniques and joint inspections are included. Such research provides important guidance for the difficult tie-in welding applications for the construction of the QCLNG pipelines in the field.

Investigation of welding procedure of 9Cr－1Mo steel for manufacturing petrochemical equipment

The welding procedure of 9Cr-1Mo alloy, especially the preheating and the post weld heal treatment, have been investigated in this paper. The critical ts/5=11s at which cold crack occurs has. been proposed as a criterion to determine whether preheating is needed. The preheating temperature is decided by the curves of heat input, plate thickness of the 9Cr-1.Mo steel vs. preheating temperature when the heat input and plate thickness are changed It is necessary to stipulate tempering parameter|P|*for welding heat treatment of the 9Cr-1Mo steel the recommended tempering parameter[P] should be controlled within 20.6 -21.3. Tempering parameter [P] is determined by tempering temperature and holding time. Tempering temperature is 760-790℃ while the period of holding time is 2 hours in this experiment. The temperature range of 450-550℃ should t be avoided during the post-heat treating since this is the sensitive tempering induced embrittle temperature of the 9Cr-1Mo steel.

Effect of preheat on TIG welding of AZ61 magnesium alloy

The effects of preheat treatments on the microstructures and mechanical properties of tungsten inert gas （TIG）-welded AZ61 magnesium alloy joints were studied by microstructural observations, microhardness tests and tensile tests. The results showed that the vol- ume fraction of the lamellar β-Mg17（Al,Zn）12 intermetallic compound of in fusion zone （FZ） increased from 15% to 66% with an increase in preheat temperature. Moreover, the microhardness of the FZ and the ultimate tensile strength of the welded joints reached their maximum values when the preheat temperature was 300℃ because more lamellar β-Mg17（Al,Zn）12 intermetallic compounds were distributed at the α-Mg grain boundaries and no cracks and pores formed in the FZ of the welded joint.

A welding document management software package based on a Client/Server structure

According to specifications for Welding Procedure Qualification of ASME IX Section and Chinese code, JB 4708 2000, a software package for managing welding documents has been rebuilt. Consequently, the new software package can be used in a Limited Area Network (LAN) with 4 different levels of authorities for different users. Therefore, the welding documents, including DWPS (Design for Welding Procedure Specifications), PQRs (Procedure Qualification Records) and WPS (Welding Procedure Specifications) can be shared within a company. At the same time, the system provides users various functions such as browsing, copying, editing, searching and printing records, and helps users to make decision of whether a new PQR test is necessary or not according to the codes above as well. Furthermore, super users can also browse the history of record modification and retrieve the records when needed.

Fracture Assessment for Electron Beam Welded Damage Tolerant Ti-6Al-4V Alloy by the FITNET Procedure

Fracture assessment of the cracked structures is essential to avoiding fracture failure.A number of fracture assessment procedures have been proposed for various steel structures.However,the studies about the application of available procedures for titanium alloy structures are scarcely reported.Fracture assessment for the electron beam(EB) welded thick-walled damage tolerant Ti-6Al-4V(TC4-DT) alloy is performed by the fitness-for-service(FFS) FITNET procedure.Uniaxial tensile tests and fracture assessment tests of the base metal and weld metal are carried out to obtain the input information of assessment.The standard options and advanced options of FITNET FFS procedure are used to the fracture assessment of the present material.Moreover,the predicted maximum loads of compact tensile specimen using FITNET FFS procedure are verified with the experimental data of fracture assessment tests.As a result,it is shown that the mechanical properties of weld metal are inhomogeneous along the weld depth.The mismatch ratio M is less than 10% at the weld top and middle,whereas more than 10% at the weld bottom.Failure assessment lines of standard options are close to that of advanced option,which means that the standard options are suitable for fracture assessment of the present welds.The accurate estimation of the maximum loads has been obtained by fracture assessment of standard options with error less than 6%.Furthermore,there are no potential advantages of applying higher options or mismatch options.Thus,the present welded joints can be treated as homogeneous material during the fracture assessment,and standard option 1 can be used to achieve accurate enough results.This research provides the engineering treatment methods for the fracture assessment of titanium alloy and its EB welds.

Welding of SA213-T91 and SA213-T23 heat-resistant steels applied in ultra supercritical thermal power units

The marteasite SA213-191 and bainite SA213-T23 high-temperature resistant steels were applied to the heating surface of the ultra supercritical thermal power unit boiler. The weld metal microstructures and welded joint performance between the two kinds of dissimilar steels were analyzed. The main reasons of the welding defects such as hot crack, cold crack, brittleness and decrease in toughness were discussed during the welding of the dissimilar heat-resistant steels of SA213- 191 and SA213-T23 in boiler manufacturing and processing operation. The welding materials were chosen and welding procedure was made according to the base metals.

Effects of pin angle and preheating on temperature distribution during friction stir welding operation

Friction stir welding （FSW） is applied extensively in industry for joining of nonferrous metals especially aluminum. A three-dimensional model based on finite element analysis was used to study the thermal characteristic of copper C I 1000 during the FSW process. The model incorporates the mechanical reaction of the tool and thermo-mechanieal characteristics of the weld material, while the friction between the material and the probe and the shoulder serves as the heat source. It was observed that the predicted results about the temperature were in good compatibility with the experimental results. Additionally, it was concluded that the numerical method can be simply applied to measuring the temperature of workpiece just beneath the tool. The effects of preheating temperature and pin angle on temperature distribution were also studied numerically. The increase of pin angle enhances the temperature around the weld line, but preheating does not affect temperature distribution along the weld line considerably.

Metallurgical behavior and variation of vibro-acoustic signal during preheating assisted friction stir welding between AA6061-T6 and AA7075-T651 alloys

The present work investigated the effects of pin profiles(cylindrical and square),pin eccentricity(0.5 mm and 1 mm)in cylindrical tool and preheating(secondary heating)on metallurgical behavior,variation of vibro-acoustic signal pattern and joint strength during friction stir welding(FSW)between AA6061-T6 and AA7075-T651 alloys.The eccentric tool pins were observed to provide good flowability and intermixing between dissimilar metals,increased the size of stir zone,and the grains in stir zone were sufficiently finer with eccentric tool pin than concentric pin.The magnitude of vibro-acoustic signal increased when shoulder plunging started and drop in signal was noted when the tool shoulder reached its desired depth.The signal magnitude was noted to be higher in welding stage compared to tool plunging stage as the tool took in fresh material during tool movement along the weld path.Preheating the workpiece prior to pin plunging and during welding notably influenced the flow behavior and mixing pattern,and the grains in stir zone were slightly coarser than those in specimen without preheating.Significant reduction in the magnitude of the signal was also observed after preheating.Tensile and flexural strength of joints were also improved slightly when additional heating was employed.

Microstructures and properties of non-preheated hardfacing welding

A new type of non-preheated hardfacing electrode was developed using H08A as the core and the coat contents including ferrotitaninm, ferrovanadium, graphite, rutile etc. The microstrnctures and properties of hardfacing metal were systematically researched. The results show the hardness of hardfacing metal increases with increasing of ferrotitanium, ferrovanadium, graphite in the coat, but the crack resistance and processing weldability become worse. The carbides formed by arc metallurgic reaction are uniformly dispersed in the matrix structure. The phases of hardfacing metal consist of α-Fe, γ-Fe, VC, TiC and Fe3 C.The carbides are compression aggregation of TiC and VC, and their appearances present irregular block. The matrix microstrncture of hardfacing metal is lath martensite. The hardfacing layers with better crack resistance and wearability are achieved and no visible cracks occur when using non-preheated electrode in continuous welding process. Hardness of hardfacing metal is more than 60HRC, and its relative wearability is five times of wearability of D667 electrode in abrasive wear test.

Research on welding technology of hot-rolled extra-high-strength steel developed by Baosteel

In this study, the welding technology of the hot-rolled extra-high-strength steel, BS960QC, has been comprehensively investigated. Analysis has been made on the weldability ,the different welding procedures ,the mechanical properties, and the fatigue properties, and a set of recommendation guidelines have been proposed for evaluating the welded joints of the extra-high-strength steel. The research and results indicate that the hot-rolled extra-high-strength steel, BS960QC,has good weldability and an excellent adaptability to welding procedures. Further,the excellent mechanical properties and fatigue properties of the welded joints ,which can be achieved by using optimized welding procedures, can completely meet the technical requirements of the construction machinery industry.

Development of an engineering－practical expert system for arc welding and its shell

The major functions of an engineering-practical expert system(ESW) and the main features of an expert system development tool(QHWEST) for arc welding procedure are introduced. A brief description is given for the development background, process and principal techniques of the two software systems.

Research and Application of All-Position Automatic Welding Machine

The all position automatic welding machine system is the special welding system for pipeline girth automatic welding on site, which has been widely used in the long distance pipeline construction projects due to the advantages of automatic control for welding parameters at all position, moving speed of bugs and operating. This automatic pipeline welding system has been successfully used in several main pipeline projects in China, and has been approved by the constructors with the benefits of higher quality passing rate, higher welding efficiency and lower labor intensity.

Improving Laser Beam Welding Efficiency

Laser beam welding is becoming widely used in many industrial applications. This paper reviews recent research conducted on the performance, potential and problems of thick section butt joint laser welding. Common defects that occur in laser beam welding with high power laser welding are discussed and possible solutions proposed. Methods of welding process efficiency improvement are analyzed.

Characterization of Dissimilar Welding between 304 Stainless Steel and Gray Iron Using Nickel Coated Electrode

This paper presents the study carried out to study the microstructure and mechanical properties of AISI 304 stainless steel and gray iron, in order to recognize the effect of welding parameters on the joint. The shielded metal arc welding technique was applied with a 3.2 mm diameter nickel coated electrode under preheating and post heat conditions at 350°C. Vickers hardness test and metallographic analysis were carried out at the heat affected zone and at the interface to determine the effect on mechanical and metallurgical characteristics. Vickers hardness differences among joint areas were directly related to microstructural changes. There are no significant differences in AISI 304 hardness, but the hardness increased at the heat affected zone and decreased at the filler metal. Grey iron hardness at the heat affected zone was even lower and more slightly superior than grey iron hardness.

基于EEMUA及DNV标准的S460钢焊接工艺开发

为了满足海洋工程建造中EEMUA 158与DNV C401双标准下屈服强度460 MPa级别结构钢的焊接施工要求,开展了基于EEMUA 158与DNV C401双标准的焊态下EN10225 S460结构钢的焊条电弧焊打底,药芯焊丝气体保护焊填充盖面的焊接工艺评定试验,完成外观检验、无损检测和相关力学性能试验,试验结果满足EEMUA158与DNV C401的双标准要求,试验取得DNV挪威船级社的认证。此项工作为同类产品的焊接工艺评定工作提供了参考。

铸造低合金钢回火焊道与焊后热处理焊接接头性能对比研究

为评估回火焊道工艺在铸造低合金钢焊接中的应用效果,研究回火焊道工艺能否替代传统的焊后热处理工艺。采用焊条电弧焊(SMAW),选用R307、R407焊条分别对A217 WC6和A217 WC9进行焊接。控制预热温度、电流、电压、搭接率和层厚,以实现回火焊道工艺。焊后对接头进行金相、硬度、拉伸、冲击和侧弯试验。试验结果表明,A217 WC6焊接接头在焊态和热处理态下的性能均满足标准要求,而A217 WC9焊接接头在焊态下的冲击功小于母材,侧弯试样在熔合线附近出现表面裂纹,且硬度明显高于热处理态。分析表明,回火焊道工艺能有效改善A217 WC6钢焊接接头的组织和性能,可替代焊后热处理。但在A217 WC9钢的焊接中,回火焊道工艺未能达到改善组织和性能的目的,焊接接头性能不满足标准要求,不能替代传统的焊后热处理工艺。

进行CTOD试验的焊接工艺评定试板制备要点分析

文中对双面焊的大厚试板焊接工艺评定试板的制备过程制定了指导说明。针对大厚试板的制备过程的各个环节提出了合理做法,并结合作业特点,设定了合理的作业顺序,提高试板制备效率。针对热影响区CTOD试样容易出现无效试样的情况,明确了在试板焊接时应关注的操作要点,提高获取热影响区CTOD试样的有效率。

焊接工艺对钢管混凝土拱桥拱肋相贯节点残余应力的影响

为研究焊接工艺对钢管混凝土拱桥拱肋相贯节点残余应力的影响,基于建立的热力顺序间接耦合的有限元分析方法,对拱肋相贯节点的焊接温度场和残余应力场进行数值模拟,结合文献试验结果验证了有限元分析方法的准确性。然后对湘渝高速双堡桥拱脚处拱肋相贯节点进行焊接温度场和残余应力场的数值模拟。在此基础上,通过参数分析研究对比了不同焊接热输入和焊接速度以及进行焊前预热和焊后热处理等不同焊接工艺对拱肋相贯节点不同位置的残余应力影响。结果表明:不同焊接热输入和焊接速度下拱肋相贯节点的焊接残余应力分布规律基本一致,变化规律表现为焊接残余应力与焊接热输入呈正相关关系,与焊接速度呈负相关关系;随着焊接热输入的减小和焊接速度的提高,拉压残余应力整体减小,拱肋相贯节点经过焊前预热150~200℃以后,残余应力的峰值应力总体降低4%以上,但焊前预热对残余应力分布基本没有影响,更高的焊前预热温度能更有效地降低残余应力的峰值应力;拱肋相贯节点经过550~650℃保温温度下保温4 h的焊后热处理以后,焊接残余应力总体降低幅度在40%以上,更高的保温温度能更有效地降低焊接残余应力;钢管混凝土拱桥拱肋相贯节点可通过减小焊接热输入和提高焊接速度的焊接工艺、焊前预热处理和焊后热处理来减小焊接残余应力。