Insert-type Electron Beam Welding Technology (Report 2) : Application to Welding of Boiler Tube

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In the previous paper, it was fully clarified that an insert-type electron beam welding has a significant effect on "Uranami Welding" and that the metallurgical and mechanical properties of dissimilar metal joints of 2.25 Cr- 1 Mo steel and austenitic stainless steel could be remarkably improved by the insert-type electron beam welding. This paper discusses the insert-type electron beam welding as applied to the "Uranami Welding" of boiler tube, and reports a systematical investigation of complications which appear in the weld bead of double run parts. Conclusions obtained may be summarized as follows : 1) Defects noted at the weld bead of double run parts are concavities at the external weld bead ; those found at the Uranami bead are concavities, excessive reinforcements and incomplete penetrations. 2) Only the downslope rate influences significantly the external weld bead appearance of double run parts. 7.5 mA/cm may be defined as the critical downslope rate regardless of the wall thickness. Therefore, at the external weld bead of double run parts, the concavity defect appears intensively when the downslope rate is higher than the critical value. 3) Both the Ib' value and the downslope rate influence the defects at the Uranami bead of double run parts. Incomplete penetration appears invariably when the Ib' value is low, and an excessive reinforcement is apt to occur when the Ib' value is too high. These defects do not occur if the Ib' value is within a proper range. This proper Ib' value increases with an increase in wall thickness Excessive reinforcement and concavity are apt to appear with the increase of downslope rate, even if the Ib' value lies in the proper range. 4) The "Lus+Lw" value does not influence the Uranami bead appearance if the Ib' value is proper. 5) Metallurgical and mechanical properties of the welded joint are quite satisfactory.
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Insert-type Electron Beam Welding Technology (Report 2) : Application to Welding of Boiler Tube

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