To easily manufacture a bent clad tube of excellent quality at a low cost by bending a low alloy steel straight tube that a stainless steel is cladded by welding on the inner surface while the straight tube is heated to the specified temperature.
Cladding by welding is applied, for example, on an inner surface of a low alloy steel (SQVIA) straight tube of 406 mm in outside diameter and 41 mm in wall thickness using a stainless steel (SUS309) welding electrode. The welding method is not limited to a TIG welding, but the submerged arc welding may be acceptable. Then, the straight tube is supported by a roll, a part to be formed is heated to 600±20°C by a high-frequency induction heating coil, and bent by pressing a bending roll thereagainst while pressing the part by a pressing die. The heating temperature may be in the range of 550 to 650°C. After the bending, the stress relief annealing (630°C×3 h) is applied over the whole tube. The ultrasonic flaw detection test and the dye penetration test are carried out on the bent clad tube to confirm no defects.
OTA TAKAHIRO
YAMAZAKI KOJI
YAMAZAKI MASATO
SATO NORIMOTO
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