Ferritic stainless steel for tubular heat exchangers and manufacturing method thereof

Abstract

The invention relates to a ferritic stainless steel for tubular heat exchangers and a manufacturing method thereof. The ferritic stainless steel comprises the following chemical components in percentage by weight: at most 0.015% of C, at most 0.020% of N, at most 0.5% of Si, at most 0.5% of Mn, at most 0.035% of P, at most 0.01% of S, 22-24% of Cr, 1.5-3.0% of Mo, 0.0050-0.050% of Al, and the balance of Fe and inevitable impurities, wherein 10(C+N)<=(Nb+Ti)<=0.6%. The manufacturing method comprises the following steps: smelting by an arc furnace+AOD (argon oxygen decarburization)+VOD (vacuum oxygen decarburization) three-step process, carrying out continuous casting to obtain a continuous casting blank, and carrying out hot rolling, acid washing, cold rolling, annealing, acid washing and the like to obtain the high-weldability cold-rolled stainless steel sheet strip. The high-weldability cold-rolled stainless steel sheet strip is suitable for manufacturing welded tubes with higher requirements for corrosion resistance and flaring performance; and the flaring ratio is up to higher than 35%.

Description

technical field [0001] The invention relates to stainless steel and a manufacturing method thereof, in particular to a ferritic stainless steel for a tubular heat exchanger and a manufacturing method thereof. The ferritic stainless steel has high corrosion resistance and a high flaring rate. Background technique [0002] In coastal areas, in order to save fresh water resources, many power plants generally use seawater for cooling. Due to the large amount of salt in seawater, strict requirements are placed on the pitting resistance of tubular heat exchanger (condenser) materials. At present, most of the condenser tubes in inland power plants use ordinary austenitic stainless steel tubes, and a few use copper tubes. Almost all new and renovated units in inland power plants use austenitic stainless steel tubes, and most coastal power plants use Ti tubes. [0003] Although austenitic stainless steel 316L has good pitting corrosion resistance and uniform corrosion resistance, its...

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Problems solved by technology

[0014] In addition, the chromium content of ferritic stainless steel in the above-mentioned patent is low, so it is difficult to meet the requirements of heat exchangers for pitting corrosion resistance; moreover, the above-mentioned patent does not involve the research on the welding performance of ferritic stainless steel and the flaring performance of welded pipes, which is The most important problem to be solved besides corrosion resistance

[0015] In order to develop ferritic stainless steel for tubular heat exchangers with higher corrosion resistance, it is necessary to further increase the chromium content in the steel, which may lead to a decrease in the flaring ratio

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