SEMIFINISHED FLAT TUBE, PROCESS FOR PRODUCING SAME, FLAT TUBE, HEAT EXCHANGER COMPRISING THE FLAT TUBE AND PROCESS FOR FABRICATING THE HEAT EXCHANGER

摘要

A semifinished flat tube 30 is for use in producing a flat tube 1 comprising an upper and a lower wall 2, 3 opposed to each other, and left and right opposite side walls 4, 5 interconnecting the upper and lower walls 2, 3 at opposite side edges thereof. The semifinished flat tube is produced from a metal plate 15 having two flat first portions 17, 18 for making the upper and lower walls 2, 3, a second portion 16 interconnecting the two first portions 17, 18 integrally for forming the right side wall 5, and two third portions 9, 10 projecting upward from the respective first portions 17, 18 integrally with the first portion each at a side edge thereof opposite to the second portion 16 for making the left side wall 4, by bending the metal plate 15 to the shape of a hairpin at the second portion 16 to cause the third portions 9, 10 to butt against each other. The two third portions 9, 10 are joined to each other by laser welding intermittently from outside at a plurality of portions spaced apart longitudinally thereof.