Welding technology of P92 steel submerged automatic arc welding for power station boiler

Abstract

The invention relates to a welding technology of P92 steel submerged automatic arc welding for a power station boiler. According to a specific method, welding wires are selected, wherein the content of C is 0.06-0.08wt%, the content of Co is 0.9-2.0wt%, the contents of other elements are the same as that of a base material, and the diameters of the welding wires are 2.4mm; the specific welding method comprises the following steps: firstly preheating; beginning to weld until the temperature is 200-250 DEG C by preheating, wherein the welding speed is constantly kept to be 13-22 m/h, and the interlayer temperature is controlled to be 300-350 DEG C; stopping welding when the temperature is over 350 DEG C, and going on welding when the temperature is reduced to be lower than 350 DEG C and not lower than 200 DEG C. Therefore, the welding technology has the advantages that the crack sensitivity of weld joints is reduced and the formation of delta-ferrites is inhibited by selecting a low-carbon Co-alloying welding material, so that the tenacity of the weld joints is improved. According to the technology, the upper limit of the interlayer temperature can be promoted to be 350 DEG C, and thus the welding efficiency is greatly improved.

Description

[0001] technical field [0002] The invention relates to a submerged arc automatic welding process, in particular to a submerged arc automatic welding process for P92 steel used in power station boilers. Background technique [0003] P92 steel is a new type of martensitic heat-resistant steel widely used in thick-walled pipes such as ultra-supercritical boiler main steam pipes and headers. The welding of the main body of the P92 header is completed in the factory, and the submerged arc automatic welding method with high efficiency and stable quality is generally used. However, the heat input of submerged arc welding is larger than that of electrode arc welding, and the thermal conductivity of P92 steel is lower than that of low alloy steel, so that the temperature between welding layers is at a high level (continuous welding can reach above 450 ° C). Deteriorating the toughness of the weld, but the layer temperature limit is too low and the welding process has to stop frequ...

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Problems solved by technology

Studies have shown that when the interlayer temperature exceeds 300 °C, the probability of cracks increases significantly (Li Zhenshan, Yan Zheng, Liu Zhiming, et al., Nondestructive Testing and Defect Prevention of P91 / P92 Steel Pipeline Factory Prefabricated Welded Joints, 2009). The temperature is generally controlled within 280°C (Mao Min, Xu Zailin, Zhang Yanfei, et al., P92 Steel Welding Quality Control of Ultra (Ultra) Critical Units, 2009), but the interlayer temperature is limited below 280°C, which makes the welding process stop frequently and single-shot The pause time is obviously extended, which seriously reduces the production efficiency

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