Welding performance analysis of S690QL steel plate

The carbon content of S690QL steel plate does not exceed 0.2%. Due to the strengthening effect of alloy elements, the hardenability of weld seam and welding heat-affected zone is improved, and the post-weld structure is martensite. The transformation temperature point Ms of S690QL steel plate is relatively high, and the subsequent welding seam can automatically temper the martensitic structure formed by the previous welding seam. The improvement of the structure reduces the probability of cold cracks and reduces the tendency of cold cracks in the S690QL steel plate during the welding process. However, if the heat input is too concentrated or the cooling rate is slow during the welding process of S690QL steel plate, softening or embrittlement will easily occur in the welding heat-affected zone of the S690QL steel plate. There is a tendency to appear cold cracks and decrease toughness.

Therefore, when formulating the welding process of S690QL steel plate, attention should be paid to the control of preheating temperature and interlayer temperature. At the same time, in order to improve the crack resistance of welded joints for S690QL steel plate, the hydrogen content of welded joints should be reduced as much as possible. Dehydrogenation treatment and welding are carried out with small heat input, so as to minimize the high-temperature residence time in the heat-affected zone of coarse grains, reduce the overheated growth and stability of austenite, and thereby reduce the degree of embrittlement in the heat-affected zone of S690QL steel plate.

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