Welding Metallurgy of

This paper presents the investigation on welding of ASTM A 106 Grade B pipes to access the quality of weldments for mechanical and metallurgical characteristics by varying the influencing factors such as voltage, wire feed rate of the filler material, and gas flow rate of CO2. The experiment was conducted using an automated MIG welding setup that has the capacity to weld the pipes with diameter ranging from 20 to 90 mm. Further the welded samples are subjected to various tests to identify weld defects, weld bead geometry, microstructure, hardness, tensile strength, and fractography. The output responses such as reinforcement form factor, penetration shape factor, and tensile strength of the material are analyzed using Taguchi method and optimized results were reported and validated. The direct and interaction plots drawn between input parameters and output responses serves as a good indicator for achieving the quality weldments by the appropriate selection of process parameters. Fractography of th...

Effect of automated MIG welding process parameters on ASTM A 106 Grade B pipe weldments used in high-temperature applications

The aim of this work is to evaluate the welding residual stress profile in ASTM A106 Gr. B steel pipes with 4" diameter and to correlate this profile with the microstructure and hardness of the joint. The results showed that the residual stresses are more uniform for a lower welding heat input. Higher welding heat input causes not only a non-uniformity of the stress profile but also promotes the maximum stress as high as the yield strength. The microstructure was composed of ferrite, perlite and possibly bainite; the presence of martensite was not verified. The hardness results indicated that none of the welding parameters used produced levels of hardness greater than 249 HV. Such a result is of fundamental importance because it suggests that low hardness does not necessarily mean low residual stress levels.

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Residual Stress, Microstructure and Hardness of Thin-Walled Low-Carbon Steel Pipes Welded Manually

Technical Review On The Welding Condition Of Steel Pipes For Sulfide Stress Cracking Resistan Ce

The first part of this work presented the results of the experimental determination of residual stresses along top joints in pipes. The purpose of the second part will be to present a critical evaluation of the microstructure and hardness of the welded joints for pipes with small diameter used in oil refineries, aiming to correlate the results with the residual stresses. The methodology consists of welding pipes with a diameter of 2 in., using a manual TIG process. AWS ER70-S3 addition metal with a 2.5 mm diameter was used. An electronic welding source and a data acquisition system for control were used to control the welding parameters. Metallographic samples were conventionally prepared and electropolished using chloride acid solution. Optical microscopy and scanning electron microscopy were used to evaluate the microstructure. Microhardness tests were made along the weld. The results show that the combination of heat cycles between the root and the finish with low heat support caused significant reinin...

Welding of the ASTM A106 Gr. B steel pipes for high-temperature service – part 2 – microstructure and hardness

Welding is the principal process of manufacture used in the fitting and repair of tube sections. However, there is a lack of information about the alterations mechanically/metallurgically caused by the welding heat cycle, especially about the behaviour of the residual stresses. The objective of the first part of this work was to evaluate the welding residual stress in small diameter pipes used in oil refineries. Two-inch diameter pipes were welded using the manual GTAW process. AWS ER 70 S3 filler rods with diameters of 2.5 and 3.25 mm were employed. An electronic power supply was used, together with data acquisition systems to control the welding parameters. Stress measurements were carried out with an X-ray mini diffractometer. The axial residual stress profiles determined in the outer surface of the pipes were formed by compressive stresses in the weld region (the fusion zone and heat affected zone) and for tension stresses in the areas more distant from the weld bead. The evidence suggested that on th...

Francisco Diego Araruna da Silva

Papers

Welding of the ASTM A106 Gr. B steel pipes for high-temperature service – part 2 – microstructure and hardness

Welding of ASTM A106 Gr. B steel pipes for high-temperature service – part 1 – residual stress analysis