Welder learning curves behaviour: “focus on welding productivity with the TIG process of marine platforms stainless steel pipes”

PurposeThe purpose of the study is to analyse the feasibility of using the potential and exponential curve models to assess the learning of a group of welders, when welding stainless steel piping with the tungsten inert gas process.Design/methodology/approachThe welding productivity data grouped according to the requirements of the ASME SECTION IX code is organised into two groups: average productivity and baseline productivity. When processing the adjustment to the two models, the Excel software Solver tool was used. The criteria for assessing the quality of the fit were: least squared method, Spearman's correlation coefficient and graphical method. The impact of the variation coefficient on the average productivity and the amplitude (difference between the minimum and maximum productivity) was also evaluated on the baseline productivity.FindingsThe curves elaborated based on the average productivity presented better quality of adjustment than those constructed from the baseline productivity. The potential and exponential models presented similar adjustment conditions, with the second having a slightly superior performance. There were no productivity gains due to learning in the studied time interval. The grouping of the average daily productivity data based on the diameter range established in the ASME code section IX presented satisfactory results, enabling its use by the industry.Originality/valueThere is no news of work on piping welding with this focus. The proposal to group the productivity data according to the degree of difficulty of execution established by the ASME code section IX, widely used in the industry, is a significant contribution to monitoring the evolution of learning. In the same way, the results allow to adopt the average productivity determined from the first 20 days of realisation of a project, as a reasonable indicator to estimate the future performance of the work, helping to correct deadlines during the realisation of a project.

Study of features in weld root formation under double-sided synchronized arc welding of vertical joints of steel tanks

It is shown that increase in the welding productivity of vertical joints of storage tanks for oil and oil products can be achieved due to the double-sided synchronized formation of the X-shaped groove. To minimize various disturbances, including variation of gap size and root face dimension, computer engineering analysis is performed, which showed that the formation of root pass during welding with the movement of the electrode down (vertical down) with increased dimension of the root face leads to lack of penetration, but during groove filling with the movement of the electrodes up (vertical up) deep penetration is achieved given the considerable root face dimension. It is defined that during welding of 30 mm thickness plates with root face dimension range from 6 to 8 mm, it is necessary to ensure the root gap dimension range from 1.5 to 3 mm along the entire length of the seam. In this case, the remaining unfilled cross-sectional area of the groove is small, which makes it possible to fill it in during single pass under two-arc double-sided welding. There is area of double-sided synchronized welding modes in which the occurrence probability of typical defects during the formation of the weld root is minimal.

Advanced Automatic Welding System for Offshore Pipeline System with Seam Tracking Function

Automatic welding technology is a solution to increase welding productivity and improve welding quality in offshore pipe welding. To increase welding productivity, it is necessary to save time during the assembly/disassembly of the guide track from the welding carriage and pipe to move the next station. The guide track consists of a pneumatic system that does not separate the welding carriage, and two welding carriages operate on a half-pipe joint to increase productivity. These welding carriages automatically operate under the controller command. An automatic welding system consists of a DC motor module, a step motor module, a welding control module, a welding monitoring module, and a central control module. The control systems incorporate control modules and transmit commands to each module for an automatic welding system. In order to minimize the inevitable misalignment between the centerline of the welding seam and the welding torch for each welding pass, a moving average algorithm for seam tracking is proposed, which was proven to be suitable for the root pass, filling pass, and cap pass. Welding experiments were also carried out to verify the validity of the weld seam tracking system.

The influence of electric ARC activation on the speed of heating and the structure of metal in welds

This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that ATIG and AMIG methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500?C/s-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of ATIG and AMIG welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of ATIG and AMIG welding capabilities.

Development of a Collaborative Robot (COBOT) for Increased Welding Productivity and Quality in the Shipyard

The future of welding for shipbuilding is increasing automation. As quality and productivity requirements continue to increase, automated systems will be required to meet those demands. What processes cannot be automated will require more highly skilled welders. Today, the shipbuilding industry depends heavily on manual welders. The nature of shipbuilding is that much of the welding, is done to produce relatively small number of ships – compared to, for example, the automobile industry. Robot programming is difficult and expensive, particularly for the welding process. By amortizing that cost over tens of thousands of automobiles, that industry can afford to use welding robots. Recently, a new approach to robotics is being developed – Collaborative Robots, also known as COBOT’s which are designed to work alongside humans. A feasibility study has been completed to develop a welding COBOT, specifically for shipbuilding. The study has shown that this human-in-the-loop mobile welding COBOT can be successful in remotely producing welds, increasing the welding speed of a skilled welder, and not requiring scaffolding to produce the weld.

Effect of Different Methods on Properties of SMA490BW Steel Welded Joints

Because of its advantages of high strength, good toughness and strong corrosion resistance capability, SMA490BW was access to a wide range of applications in bogie frame of high-speed train. Manual welding, single-wire automatic welding and double-wires automatic welding were used to weld plate butt joints of SMA490BW steel. The mechanical properties testing and microstructure observation were carried out. Results showed that the strength of welded joint and impact toughness could meet the design requirements with the above methods. Double-wires welding owned an outstanding advantages of saving energy and welding productivity in such the above methods which laid the foundation for application of double wires welding in bogie frame of high-speed train.

An Integrated Approach to Welding, AUT and ECA for Pipeline Construction

An integrated approach for the development of welding, inspection, and alternative weld flaw acceptance criteria, as used for girth welds during pipeline construction is presented. Welding is typically the pace limiting step during pipeline construction and is critical element of pipeline integrity. As such it is vital that it be completed efficiently and with high quality. Each of these three elements is vitally important to welding productivity and quality. At the core of the approach is the coordination of the three elements such that they are developed in concert. By this coordinated effort, all design options are considered leading to optimization of the final outcome. The approach is described by providing an example alternative weld flaw acceptance criteria, and giving the logic pertaining to choices of welding setup, AUT setup, the standard used for design and construction, and the impact of choices within these three elements on the final outcome. The paper illustrates the importance of a unified approach on weld productivity and quality.