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一、前言: 锅炉换热器用φ40×1.5mm钢管以前采用无缝钢管,后来采用高频焊接钢管。国内厂家使用退火状态的冷轧带钢作为焊管的
First, the foreword: Boiler heat exchanger with φ40 × 1.5mm steel pipe before the seamless steel tubes, and later the use of high-frequency welded steel pipe. Domestic manufacturers use annealed cold-rolled strip as a welded pipe