Connection element

1 . A connection element comprising:

a tubular first part with a first ring-shaped connection face for connection with an austenitic steel pipe and a tubular second part with a second ring-shaped connection face for connection with a first ferritic steel pipe;

wherein the tubular first part is of an austenitic steel material and wherein the tubular second part is of a ferritic steel material;

wherein the tubular first and second parts are in one-piece and formed such that a passage between the first and second ring-shaped connection faces is formed; and

wherein the tubular first and second parts are produced by an additive manufacturing process,

wherein the tubular second part has a third ring-shaped connection face for connection with a second ferritic steel pipe,

wherein the third ring-shaped connection face is arranged concentrically with the second ring-shaped connection face, as seen in a length direction,

wherein a cooling channel extending along a circumference is formed in the tubular first part.

2 . The connection element according to claim 1 , wherein the additive manufacturing process is a cladding process, direct energy deposition, wire arc additive manufacturing, electron beam additive manufacturing, laser beam additive manufacturing, or plasma arc additive manufacturing.

3 . The connection element according to claim 1 , wherein an outlet of the cooling channel is arranged between the second ring-shaped connection face and the third ring-shaped connection face.

4 . The connection element according to claim 3 , wherein the cooling channel is spiral-shaped.

5 . The connection element according to claim 1 , wherein the tubular first part comprises an inner sleeve and/or an outer sleeve arranged in radially overlapping relation on an inside or an outside of a section of the tubular second part.

6 . The connection element according to claim 1 , wherein the tubular first part comprises a thermo-sleeve that extends inside the tubular first part;

wherein the thermo-sleeve is spaced apart from the tubular second part and/or the inner sleeve.

7 . The connection element according to claim 1 , having a transition region between the tubular first and second parts, in which a gradual transition between the compositions of the materials of the tubular first and second parts takes place.

8 . The connection element according to claim 1 , wherein the material of the tubular first part is an austenitic steel, selected from NiCr23Co12Mo, NiCr22Mo9Nb; and/or wherein the material of the tubular second part is selected from 16Mo3, 13CrMo4-5, 1OCrMo9-10.

9 . A pipe arrangement comprising a highly heat resistant steel pipe, an inner ferritic steel pipe and a connection element according to claim 1 , wherein an end of the highly heat resistant steel pipe is connected to the first ring-shaped connection face of the connection element by a circumferential weld joint, and wherein an end of the inner ferritic steel pipe is connected to the second ring-shaped connection face of the connection element by a circumferential weld joint.

10 . The pipe arrangement according to claim 9 , further comprising an outer ferritic steel pipe that forms a double pipe together with the inner ferritic steel pipe; and wherein an end of the inner ferritic steel pipe is connected to the third ring-shaped connection face of the connection element by a circumferential weld joint.

11 . A heat exchanger comprising an inner ferritic pipe for a fluid to be cooled and a connection element according to claim 1 ; wherein an end of the ferritic inner pipe is connected to the second ring- shaped connection face of the connection element.

12 . The heat exchanger according to claim 11 , wherein the heat exchanger is a double pipe heat exchanger having a double pipe formed by the inner ferritic pipe and an outer ferritic pipe; and wherein an end of the outer ferritic pipe is connected to the third ring-shaped connection face of the connection element.

13 . The heat exchanger according to claim 11 , further comprising a highly heat resistant steel pipe; wherein an end of the highly heat resistant steel pipe is connected to the first ring-shaped connection face of the connection element.

14 . A processing arrangement comprising a furnace and a heat exchanger according to claim 13 , wherein the highly heat resistant steel pipe is or is connected to an outlet pipe of the furnace.

15 . The connection element according to claim 1 , wherein the tubular first part comprises an inner sleeve and/or an outer sleeve arranged in radially overlapping relation on an inside or an outside of a section of the tubular second part, and wherein the inner and/or outer sleeves are arranged at least partially in radially overlapping relation with the cooling channel.

16 . The connection element according to claim 1 , wherein the tubular first part comprises a thermo-sleeve that extends inside the tubular first part, wherein the thermo-sleeve is spaced apart from the tubular second part and/or the inner sleeve, and wherein the thermo-sleeve radially overlaps the cooling channel.

17 . The pipe arrangement according to claim 9 , wherein the highly heat resistant steel pipe is an austenitic steel pipe.

18 . The heat exchanger according to claim 11 , wherein the end of the ferritic inner pipe is connected to the second ring-shaped connection face of the connection element by a circumferential weld joint.

19 . The heat exchanger according to claim 12 , wherein the end of the outer ferritic pipe is connected to the third ring-shaped connection face-of the connection element by a circumferential weld joint.

20 . The heat exchanger according to claim 13 , wherein the end of the highly heat resistant steel pipe is connected to the first ring-shaped connection face of the connection element by a circumferential weld joint, and the highly heat resistant steel pipe is an austenitic steel pipe.