Abstract: A method for production of a multi-layer gap-less steel pipe. An inner pipe and an outer pipe are formed from thermomechanically rolled steel strip with high notched bar impact strength by welding. The individual helical welding seam steel pipes of about the same lengths are matched with a difference of less than about one percent between the outer diameter of the inner pipe and the inner diameter of the outer pipe. The matched inner pipe is inserted into the outer pipe and the pipes are mechanically expanded with diameter control to a preset outer diameter of the multi-layer steel pipe. The resulting multi-layer steel pipe has the inner pipe disposed under compression and the outer pipe layer disposed under stress. The presence of a compression stress in the inner pipe provides a means opposed to hydrogen sulfide stress corrosion.

Abstract: For increasing the resistance of steel pipes or tubes against acidic medium, by a combination of a heat treatment and the use of an alloyed steel, a compressure stress is built up on the side of the tubes or pipes facing the acidic medium, of up to 30% of the yield limit.

Abstract: A method for production of a multi-layer gap-less steel pipe. An inner pipe and an outer pipe are formed from thermomechanically rolled steel strip with high notched bar impact strength by welding. The individual helical welding seam steel pipes of about the same lengths are matched with a difference of less than about one percent between the outer diameter of the inner pipe and the inner diameter of the outer pipe. The matched inner pipe is inserted into the outer pipe and the pipes are mechanically expanded with diameter control to a preset outer diameter of the multi-layer steel pipe. The resulting multi-layer steel pipe has the inner pipe disposed under compression and the outer pipe layer disposed under stress. The presence of a compression stress in the inner pipe provides a means opposed to hydrogen sulfide stress corrosion.

Abstract: A method of and device for producing multi-layer pipes by helically winding a plurality of bands loosely arranged one above the other, which are individually withdrawn from a supply, straightened out, trimmed, and in the form of a band loop are conveyed to the forming station at the respective angle of lead-in corresponding to the respective pipe diameter, whereupon the layers are together welded to form a pipe strand which is subsequently cut into individual pipes. All bands are supplied and advanced independently of the irregularities of the respective longitudinal band edge shape in steadily straight lead-in directions, and all band edges are machined together to a possible maximum width in coordination with each other whereupon the bands are driven together while the welding gap is controlled in conformity with their band edge shape merely by pivoting the pipe.