Joint flange using thickness-increased and cutting-processed pipe and method for manufacturing same

A method of manufacturing a joint flange using a thickness-increased and machined pipe, the method comprising:

• preparing and cutting a pipe to a predetermined length;
• forming a flange having a mounting hole by die casting, the flange used for installing the pipe;
• forming a thickness-increased part using a plurality of bumping operations, wherein:
• a first bumping operation uses a first punch member having a first entrance groove formed therein configured to accommodate an upper portion of the pipe, including a first expansion groove to increase a thickness of the thickness-increased part outward, and having a bead processing groove configured to form the first bead,
• a second bumping operation uses a second punch member having a second entrance groove formed therein configured to accommodate the upper portion of the pipe processed by the first punch member and including a second expansion groove to increase the thickness of the thickness-increased part inward, the second expansion groove having a greater width than the first expansion groove, and
• a third bumping operation uses a third punch member having a third entrance groove formed therein configured to accommodate the upper portion of the pipe processed by the second punch member and including a third expansion groove to further increase the thickness of the thickness-increased part inward, the third expansion groove having a width greater than the width of the second expansion groove,
• as a result of the plurality of bumping operations, an inner diameter of the pipe is decreased at the one end of the pipe, and the first bead locked to the flange is formed;
• machining a circumference of the thickness-increased part to form a sealing groove having an O-ring installed;
• and
• inserting and installing the pipe in the mounting hole of the flange and the other end of the pipe is pressed to form a second bead so that the pipe is pressed and fixed to a lower end of the flange.