The extrusion die design of the ordinary non-rolled aluminum round tube does not need to consider the problem of sufficient welding. Under normal inspection conditions, the appearance of the naked eye has no obvious weld line and no obvious cracking. Under such conditions, the inside is The pressure bearing capacity can generally be 1.5 times higher than the index value. However, for pure aluminum round tubes, the requirements for welding are very important. At this time, the design of ordinary molds can not meet the requirements. Compared with ordinary molds, it should be fully welded, in the mold design. Should be fully covered by the bridge, in this state, there is a difference of 10-12mm than the ordinary mold. This has a profound effect on the cracking of the fins of the pure aluminum round tube.
The heating of the aluminum rod of the common profile is generally between 450 and 490 ° C, and the temperature is maintained for about 2.5 hours, but the heating of the aluminum rod of the pure aluminum round tube is not applicable. After a long period of trials, the author found out that the heating temperature is controlled between 500 and 530 °C, and the temperature is more than 2.5 hours. This ensures adequate soldering, lifting height and elongation.
For the required H112 state, no full air cooling is required, as long as the aluminum tube is not burned to the cold bed, and the subsequent straightening temperature is not affected.
Due to the material and temperature, for a pure aluminum round tube, the ratio of straightening stretch length to tube length is between 30:8400.
Pure aluminum round pipe has strict requirements on the length of the material at both ends when sawing. Experience and calculation prove that the length of the material head is ≥1.8m.