Combined aluminum alloy double-wall drill pipe unit

The invention discloses a combined aluminum alloy double-wall drill pipe unit composed of an inner pipe, an outer pipe, an upper connector of the outer pipe, a lower connector of the outer pipe, an upper connector of the inner pipe, a lower connector of the inner pipe and seal rings. Two ends of the outer pipe are connected with the upper connector of the upper pipe and the lower connector of the outer pipe through clamping slots, respectively. The seal rings are arranged on matched cylindrical surfaces between the outer pipe and the upper connector of the outer pipe as well as between the outer pipe and the lower connector of the outer pipe. The inner pipe is arranged in the outer pipe. Two ends of the inner pipe are connected with the upper connector and the lower connector of the inner pipe through threads, respectively. As the combined aluminum alloy double-wall drill pipe units coupled, two adjacent outer pipes are in threaded connection through the upper connectors and the lower connectors of the outer pipes, and the inner pipes are in inserting connection through the upper connectors and the inner connectors of the inner pipes. The outer pipe made of aluminum alloy is 1/3 of steel in density, leading to light weight and carrying convenience. The combined aluminum alloy double-wall drill pipe unit is light, convenient to carry, simple in structure, easy to detach, reasonable in load distribution, accurate in the centering position between the inner pipe and the outer pipe, good in stress working condition and the like.