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COB5 UMA CONTRIBUIÇÃO AO ESTUDO DA SOLDAGEM COM OS ARAMES TUBULARES AUTOPROTEGIDOS / A CONTRIBUTION FROM STUDY OF SELF-SHIELDED FLUX-CORED ARC WELDING.

Augusto José de Almeida Buschinelli, Carlos Alberto Mendes da Mota, Estela Surian & Jesualdo Pereira Farias.

Universidade Federal do Ceará/Campus do Pici/CT/DEM/ENGESOLDA-Bloco 715; CEP 60.455-760 Fortaleza - CE, Brasil

E - mail: jpf@truenet-ce.com.br; Fax: (085) 288 9636

Eight AWS E71T- 7 flux-cored steel welding wires were formulated with systematic changes in the Ni-content between 0% - 3,5% and with the addition of 0,5% and 1,0% Mn in the flux. The effects of the above changes and the effects of the welding current and stickout on the economical characteristics of the wire (fusion rate and deposition efficiency) and on the welding bead geometry were examined. The effect of the above wires and the welding parameters on the weld bead hardness were also analised. The results showed that the welding parametrs as well as the wire compositions affected the economical characteristics as well as the weld bead geometry. Otherwire, the effec of the heat imput on the weld bead hardness is less significant.

Keywords: Cored wire; Flow; Stability/Arame tubular; Fluxo; Estabilidade.

COB7 EFEITO DO MAGNÉSIO SOBRE A GEOMETRIA DA SOLDA E SOBRE AS CARACTERÍSTICAS ECONÔMICAS DE ELETRODOS AWS E7024/ THE EFFECT OF MAGNESIUM ON THE GEOMETRIC AND ECONOMIC CHARACTERISTICS OF THE AWS E7024 ELECTRODES

Celina Leal Mendes da Silva⁽¹⁾, Vinícius Sales Rocha⁽²⁾, Estela Surian⁽³⁾, Jesualdo Pereira Farias⁽⁴⁾

(1)Tv. Apinagés, 973/402 - Bairro Batista Campos - 66045-110 - Belém -Pa., Fones: (091) 224 9883 e (091) 222 0617.

Fax: (091) 241-3415 - e-mail: belucio@supridad.com.br

(2)Campus do PICI - Bloco 714 - DEM - 60455-760- Fortaleza - Ce, Fones: (085) 288 9617

(3)Campus do PICI - Bloco 714 - DEM - 60455-760- Fortaleza - Ce, Fones: (085) 288 9617

(4)Rua Bento Albuquerque, 1550/201, Bairro Papicu - 60190 - 080 - Fortaleza - Ce., Fones: (085) 288 9617 e (085) 288 9600.

FAX (085) 288 9636 - e-mail: jpf@truenet-ce.com.br

Among the different kinds of electrodes, the rutilic types are acknowledged as those which allow the easiest operation and handling. Their mechanical properties, however, are inferior to those of basic and cellulosic electrodes. A recent study has shown that adding magnesium to the coating of AWS E7024 rutilic electrodes improves considerably the impact strength of the welding metal and to reduce the content of diffusible hydrogen. This work attempts to analyse the effect of magnesium on the economic characteristics of rutilic electrodes and also on the geometric characteristics of the experimental welding electrodes. Derived from the AWS E7024 class were developed, with 3.25 mm diam., and exhibiting five different amounts of metallic magnesium ( from 0 to 4% ). Simple deposition automatic weldings in plane position with current DC+, DC- and AC were performed in 170x50x6 mm ABNT 1020 all-weld metal, using a computerised device. The results obtained were compared using the ANOVA method, and showed that magnesium content does not effect welding geometry neither economic characteristics of consumables.

Keywords: electrodes,magnesium,welding,rutilic/eletrodos, magnésio, solda, rutílico

COB9 UM CRITÉRIO PARA AVALIAÇÃO DA ESTABILIDADE DO ARCO ELÉTRICO DE SOLDAGEM EM PROCESSOS GMAW / A CRITERIA FOR EVALUATION OF ARC STABILITY IN GMAW

Carla Barata Ribeiro e Sadek C. Absi Alfaro.

Universidade de Brasília, GRACO: Grupo de Automação e Controle, ENM-FT-UnB. CEP 70.910-900, Brasília - DF. Brasil – E-mail: sadek@jazz.graco.unb.br

This work presents the evaluation of the arc stability in GMAW (Gas Metal Arc Welding) processes by the sound emitted during operation. Using a neural network, the relation between some criteria based on the oscilograms of voltage and current and some characteristics of the sound of the arc allows the recognition of stable or unstable behaviour patterns, and gives an intelligent and simple control of the welding.

Keywords: Arc stability, GMAW, Arc Welding

COB 12 - SELF CALIBRATION AND OFF-LINE PROGRAMMING OF WELDING CELLS

Milton L. Siqueira; Guilherme C. Carvalho & Sadek C.A. Alfaro

GRACO - Grupo de Automação e Controle, Dept^o de Eng. Mecânica, FT, Universidade de Brasília, CEP - 70-910-900 - Brasília-DF, Brazil. E-mail - milton@guarany.unb.br

The objective of GRACO’s research is to implement an off-line programming system, which includes welding parameters generation, as well as to integrate the joint location, the seam tracking, and the stand-off control features into a welding monitoring and control system for the GMAW process. The resultant combination is going to provide full off-line programming facilities allied to self-adjusting capabilities for an automatic welding cell.

Keywords: Automation, Robotic, Off-line programming, Self-calibration, welding.

COB13 APLICAÇÃO DE VISÃO POR COMPUTADOR PARA GUIAGEM DA TOCHA EM UMA CÉLULA DE SOLDAGEM / COMPUTER VISION APPLICATION ON TORCH GUIDANCE IN A WELDING CELL

Lélio Ribeiro Soares Jr, Víctor Hugo Casanova Alcalde & Sadek Absi Alfaro

Grupo de Automação e Controle, Faculdade de Tecnologia, Universidade de Brasília - UnB - CEP 70.910-900 - Brasília, DF;

E-mail: casanova@guarany.cpd.unb.br

A computer vision system is proposed for guiding the welding torch in a robotic welding station. The vision sensing system consists of a laser-emitting diode, a CCD video camera, a frame grabber card and a PC computer. The camera and the laser device are fixed to the welding torch. The laser beam produces a luminous stripe across the welding path and in advance of the torch. By capturing images from the workpieces reflecting the laser stripe an image processing algorithm establishes a welding reference path and compares it with the actual path. A trajectory deviation error is generated and transmitted to the robot control unit for the necessary action. Provisions for the implementation of a complete visual servo control for the robotic welding station are also discussed.

Keywords: Computer Vision Guidance; Welding Seam Tracking; Robotic Welding Station; / Guiagem por Visão Computacional; Rastreamento de Trajetória de Soldagem; Estação Robótica para Soldagem.

COB14 USO DE REDES NEURAIS EM SOLDAGEM MIG/MAG SINÉRGICO PULSADO / USE OF NEURAL NETWORK IN PULSED SINERGIC GMAW

José Hilton Ferreira da Silva e Sadek Crisóstomo Absi Alfaro

Universidade de Brasília, GRACO: Grupo de Automação e Controle, ENM-FT-UnB. CEP 70.910-900, Brasília - DF. Brasil

E-mail: sadek@jazz.graco.unb.br

The present work is aimed to optimise the synergic pulsed MIG/MAG weld process’ parameters. The experimental methodology was planned using factorial design 3⁴. The welding parameters controlled were the current, trim value, welding speed and stick-out. The results analyses were based on the bead geometry. A Neural Network like back-propagation was used to establish the best weld conditions. The results obtained here shows the practical use of factorial designs in welding experience. The neural network is useful in optimising the welding parameters and it is also showed in this work.

Keywords: Neural network, Optimisation, Pulsed Welding

COB15 OTIMIZAÇÃO DE PARÂMETROS DE SOLDAGEM NO PROCESSO GMAW UTILIZANDO ANÁLISE ESTÁTICA E REDES NEURAIS / OPTIMISATION OF GMAW PARAMETERS USING STATISTIC ANALYSIS AND NEURAL NETWORK.

Marcelo Elias, M. L. Siqueira e Sadek C. Absi Alfaro

Universidade de Brasília, GRACO: Grupo de Automação e Controle, ENM-FT-UnB. CEP 70.910-900, Brasília - DF. Brasil – E-mail: sadek@jazz.graco.unb.br

This work has two main purposes. Firstly, identify operating envelopes for GMAW (Gas Metal Arc Welding) process in commercial sheet steels produced in Brazil with 3,0 mm thickness. Secondly, establish mathematical relations between welding parameters and welding dimensions, besides their performance in welded joints; for doing that, some pre-determined conditions were established: such as shielding gas, electrode diameters and weld position. In this work was also verified if a commercial power source is efficient or not when used in semi-automatic process. The experimental methodology was planned using factorial design. The steel’s plates were welded in butt weld position and aided by a machinery tool, which was adapted to operate in the weld speed. The welding controlled parameters were current, tension and travel speed. The analysed parameters were based on the bead geometry and resistance of the weld joint. The mathematical models were determined by multiple regression and neural network which shows to be useful in optimise the welding parameters and the mechanical resistance of welding joint and bead geometry.

Keyword: Automation, Optimisation, Welding, Factorial Design, Multiple Regression Analysis, Neural Network

COB25 UTILIZAÇÃO DOS CAMPOS DE TEMPERATURA GERADOS DURANTE A SOLDAGEM À ARCO PARA AUTOMAÇÃO DO PROCESSO/THE USE OF TEMPERATURE FIELDS GENERATED DURING ARC WELDING FOR PROCESS AUTOMATION

Ivanilza Felizardo & Alexandre Queiroz Bracarense

Departamento de Engenharia Mecânica - UFMG - Belo Horizonte -

CEP 312700-901 - Belo Horizonte, Brazil - E-mail: queiroz@vesper.demec.ufmg.br

In arc welding process, the thermal energy from the electric arc is responsible for the fusion of the weld pool and for an abrupt thermal cycle in the adjacent unmelted metal. It is expected that the heat supplied by the arc should be sufficient for fusion affecting on minimum the rest of the material. However, one of the greatest problem resulted from the process is the occurrence of residual stresses. To evaluate the extension of the heating effect and looking for the development of a welding automation system, mathematical modeling can be applied. One objection however is that, the existent models are static and usually complex. Rosenthal's model is one of these existent models and despite it is static, it is very simple to apply. This paper presents a study of Rosenthal’s model modification to describe the thermal profiles on the base metal produced "during" welding. With the modification, it was possible to verify the more suitable welding parameter to be used as a dynamic manipulated variable in a welding control system, looking forward to a robotics application.

Keywords: Soldagem robotizada, Modelamento analítico, perfis térmicos, tensões residuais, automação e controle.

Robot Welding, Analytical Modeling, Thermal Profile, Residual Stresses, Automation and Control

COB375 EFEITO DAS DISTORÇÕES SOBRE A DISTRIBUIÇÃO DAS TENSÕES RESIDUAIS NA SOLDAGEM / DISTORTIONS EFFECTS ON WELDING RESIDUAL STRESSES DISTRIBUTIONS

Augusto Eduardo Baptista Antunes

UNESP - Campus de Guaratinguetá, Faculdade de Engenharia

CEP.: 12500-000 - Guaratinguetá, Estado de São Paulo e-mail: lidia@ieav.cta.br

In the welded steel sheets by shielded metal-arc welding and by oxyacetylene torch, the distortions were recorded and the residual stresses by X-rays diffraction measured. Thus, it was possible to show how the differents forms of distortions affect the macroscopic residual stresses distributions in welding junctions.

Keywords: welding, residual stresses, distortion.

COB376 DIFICULDADADES NA DETERMINAÇÃO DE TENSÕES RESIDUAIS NA SOLDAGEM POR DIFRAÇÃO DE RAIOS-X / DIFFICULTIES IN WELDING RESIDUAL STRESSES DETERMINATION BY X-RAYS DIFRACTION

Augusto Eduardo Baptista Antunes

UNESP - Campus de Guaratinguetá, Faculdade de Engenharia

CEP.: 12500-000 - Guaratinguetá, Estado de São Paulo, e-mail: lidia@ieav.cta.br

The X-rays diffraction methods are convenient for the welding residual stresses determination, and can be reasonably evalluated with such precision the great stress gradient that occur near the weld beads, presenting results seldom obtained by other experimental procedures. Nevertheless, the X-rays methods are not trivial if discernment and confidence are expected; it is particularly true in the welding residual stresses determination. This paper, tries to present the practical difficulties and possible solutions encountered to solve them. A lot of stress measurements effectuated, by the author, in sheets of differents kinds of steel, welded by shielded metal-arc welding and oxy-acetylene torch are the basis for discussion.

Keywords: Residual stresses, welding, X-rays difraction.

COB556 SELEÇÃO DE PROCESSO DE SOLDAGEM BASEADA EM ANÁLISE CONJUNTA DE CUSTO E QUALIDADE / WELDING PROCESS SELECTION BASED ON COMBINED COST AND QUALITY ANALYSIS

César Rezende Silva & Valtair Antonio Ferraresi

Departamento de Engenharia Mecânica, Universidade Federal de Uberlândia -- UFU

CEP 38.400-902 - C.P. 593 - Uberlândia, Brasil - E-mail: crezende@ufu.br; valtairf@ufu.br

The diversity of welding processes and their variants makes the choice of process difficult. Both Cost and Quality analysis are a good indicative to consider during the selection, because in the market exigencies of Cost and Quality must be attended in order to be competitive. In fact, the best process will be the one that analysing these factors together result in the best global performance. The objective of this work is to select the best process for a practical case study, using a thin carbon steel sheet as the workpiece normaly used in dredging pipes. The processes considered are: GMAW - short-circuit, spray and pulsed, and GTAW - convencional and pulsed. The results showed that, for the welding set conditions, in terms of Quality, the best was spray GMAW. In terms of Cost, short-circuit GMAW outperformed the others. However, considering both Cost and Quality requirements, the best was short-circuit GMAW.

Keywords: Welding, Cost, Quality, Thin sheet, Gaseous protection / Soldagem, Custo, Qualidade, Chapa fina, Proteção gasosa.

COB557 UTILIZAÇÃO DA EMISSÃO ACÚSTICA NO ESTUDO DA TRINCA DE REAQUECIMENTO/ACOUSTIC EMISSION UTILIZATION IN STUDY OF REHEAT CRACKING

Valtair Antonio Ferraresi⁽¹⁾ & Roseana da Exaltação Trevisan⁽²⁾

⁽¹⁾Departamento de Engenharia Mecânica, Universidade Federal de Uberlândia - UFU/DEEME

CEP 38.400-902 C.P 593 . Uberlândia, MG, Brasil - E-mail: valtairf@ufu.br

⁽²⁾Departamento deEngenharia de Fabricação, Faculdade de Engengaria Mecânica - UNICAMP

CEP 13083-970 C.P. 6122 - Campinas, SP, Brasil - E-mail: roseana@fem.unicamp.br

The Reheat Cracking phenomenon can occur either in the heat affected zone or in the fusion zone during Post Weld Heat Treatment (PWHT) for stress relief as well as in high temperature operation. An Acoustic Emission Measurement System (AEMS) was used in this work to determine the instant of propagation of reheat cracking. The AEMS was connected to a Modified Implant Test which is applied for simulation of thermal cycles typically. This study were developed using a high strength low alloy steel commercially produced. Tests varying initial loads and different heat-treatment temperatures, maintaining constant the welding conditions. It was concluded that the AEMS is very adequate for the purpose, where the modes fractures showed a predominance for low-ductility intergranular fracture. For the modes of fracture by creep cavitation were not possible determine with clarity the instant of propagation of reheat cracking.

Key words: Welding, Reheat cracking, Thermal treatment, fracture surface, Acoustic emission/Soldagem, Trinca de Reaquecimento, Tratamento Térmico, Superfície Fraturada, Emissão Acústica.

COB660 MODELAGEM E SIMULAÇÃO DA DINÂMICA DE UM SISTEMA PARA SOLDA DE CHAPAS A FRIO / PRESS JOINING SYSTEM DYNAMICS MODELING AND SIMULATION

Vicente Faxina Déo¹ e Mauro Speranza Neto²

¹Xerox do Brasil - Engenharia do Produto e Manufatura - E-mail: deo@ngm.br.xerox.com

²Departamento de Engenharia Mecânica - PUC-Rio - E-mail: msn@mec.puc-rio.br

This paper covers the description and modeling procedure, based on the Bond Graph language, of the Press Joining industrial method for fastening sheet metal parts. The computacional simulation of its dynamics and the applications of these results are presented, aiming to show the advantages of using these methodologies in the design of industrial process.

Keywords: Modelagem Dinâmica, Grafos de Ligação, Simulação Dinâmica, Solda à Frio, Processo Industrial.

Dynamic Modeling, Bond Graphs, Dynamic Simulation, Fastening Sheet, Industrial Processes.

COB1261 AUTOMATIC VOLTAGE TUNING - A MEANS OF ENSURING PROCESS STABILITY AND WELD QUALITY IN GMA WELDING

Guilherme C. Carvalho^*, Babatunde Ogunbiyi^†, Robert McMaster^† & Sadek C.A. Alfaro^*

* CNPq/GRACO, Departamento de Engenharia Mecânica, Faculdade de Tecnologia, UnB, CEP 70910-900, Brasília D.F., Brasil - E-mail: sadek@guarany.cpd.unb.br

†Welding Group, School of Industrial and Manufacturing Science, Cranfield University, Cranfield, Bedford, MK43 0AL, England - E-mail: wu917p@cranfield.ac.uk

This paper presents a method of attaining process stability and ensuring good weld quality in conventional gas metal arc welding by automatic voltage tuning. The process is first monitored, its stability assessed and, based on the assessment, voltage control commands are issued. The automatic voltage tuning algorithm utilises fuzzy production rules, which use as inputs the values of four monitoring indices calculated from the welding current and voltage waveform features. The main control objective of the algorithm is to ensure that the welding voltage is not too low or unnecessarily high, thereby preventing arc instability, minimising the level of fume and spatter generated, and reducing the risk of defects such as undercut and lack of fusion. The result of this present research work shows that welding procedures can be adapted to give good weld quality and stable welding arcs by trimming the welding voltage to a suitable level.

Keywords: Gas Metal Arc Welding, Automatic Voltage Tuning, Metal Transfer, Process Monitoring and Control.