Welding parameters thick plates, and column strength

This paper presents a study of the influence of different welding parameters on the magnitude and distribution of residual stresses in oxygen—or flame-cut plates 24 X 2 in. made of A36 steel. The residual stress diagrams obtained after complete sectioning and after slicing are related to the original conditions of manufacture and fabrication. The welded flame-cut plates studied have been used as base metal plates of a built-up section 24H428, and the strength of this heavy section is analyzed theoretically. The differences observed in the theoretical column strength of this simulated section 24H428, built up with flanges of 24 x 2 in. flame-cut centerwelded plates and a web of a 20 x l 1 ^ in. flame-cut edge-welded plate, is correlated to the different heat inputs caused by the different fabrication processes. Conclusions are drawn with respect to J. BROZZETTI, formerly with Lehigh University, is Research Engineer, Centre Technique Industriel de la Construction Metallique, Paris, France; G. A. ALPSTEN formerly with Lehigh University is Associate Director, Swedish Institute of Steel Construction, Stockholm, Sweden; L. TALL is Director, Division for Fatigue and Fracture, and Professor of Civil Engineering, Lehigh University, Bethlehem, Pa. Paper presented at the AWS 52nd Annual Meeting held in San Francisco, Calif. , during April 26-29, 1971. The work described in this paper was carried out as part of an investigation sponsored jointly by the National Science Foundation and the Column Research Council, and was conducted under the technical guidance of the Column Research Council. the effect of the different welding parameters on the strength of the column. The variation of the mechanical properties through the thickness and at different locations across the 24 X 2 in. plates was determined by means of tension tests on the small size specimens. The results are discussed with respect to the specimen location, and compared with the patterns of residual stress obtained previously. The results of the study may be summarized in brief: 1. The variation of residual stresses across the thickness of a thick plate is substantial only in the region of the heat-affected zone of the weld. 2. In general, the variation of residual stresses through the thickness of a plate does not have an important effect on the strength of the column, as measured by the tangent modulus load. 3. Preheating temperatures higher than the specification recommendations have a negligible influence on residual stress formation or on column strength. 4. The number of passes and the speed of welding have little influence on the column strength of welded shapes. 5. The mechanical properties of the material in the region of heat inputs, such as due to welding or flame cutting, differ considerably from those in the unaffected base metal, but do not have an important influence on column strength. 6. The manufacturing and fabrication conditions play an important role for column strength: welded shapes of universal-mill plates compare unfavorably in strength with respect to welded shapes of flame-cut plates; annealed shapes indicate the most favorable column strength.