Method of and Apparatus for Shot Peening Stainless Steel Tubing

Abstract

A method of and an apparatus for shot peening an inner surface of a stainless steel tube. A set of at least two electromagnets is arranged around the stainless steel tube and has an iron core with an air gap adjacent to the stainless steel tube. At least one magnetic shot particle is provided inside the stainless steel tube. A controller controls the activation of the electromagnets according to a predetermined sequence, so as to cause the at least one magnetic shot particle to repeatedly hit the inner surface of the tube so as to shot peen the inner surface.

We Claim: 
     
         1 . A method of shot peening an inner surface of a stainless steel tube, the method comprising the steps of:
 arranging a set of at least two electromagnets around the stainless steel tube, the electromagnets having an iron core with an air gap adjacent to the stainless steel tube;   providing at least one magnetic shot particle inside the stainless steel tube;   projecting the at least one magnetic shot particle repeatedly against the inner surface of the tube so as to shot peen the inner surface; and   performing the projecting step by activating the electromagnets according to a predetermined sequence so as to cause the at least one magnetic shot particle to repeatedly hit the inner surface of the tube.   
     
     
         2 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising the steps of rotating the stainless steel tube around its axis and moving the set of electromagnets relative to the stainless steel tube in the direction of the axis of the stainless steel tube. 
     
     
         3 . A method of shot peening an inner surface of a stainless steel tube according to  claim 2 , further comprising the steps of attaching the set of at least two electromagnets in a frame and moving the frame in the direction of the axis of the stainless steel tube. 
     
     
         4 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising arranging a set of at least six electromagnets symmetrically outside an outer periphery of the stainless steel tube, wherein the stainless steel tube is not rotated. 
     
     
         5 . A method of shot peening an inner surface of a stainless steel tube according to  claim 4 , wherein the set of multiple electromagnets comprises at least eight electromagnets. 
     
     
         6 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising the steps of attaching the set of at least two electromagnets in a frame, rotating the frame around the stainless steel tube, and moving the frame along the stainless steel tube. 
     
     
         7 . A method of shot peening an inner surface of a stainless steel tube according to  claim 6 , further comprising rotating the frame back and form around the stainless steel tube. 
     
     
         8 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising arranging a set of multiple electromagnets on at least two adjacent rings outside the stainless steel tube, wherein the stainless steel tube is not rotated. 
     
     
         9 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising the steps of attaching the set of at least two electromagnets in a frame, and moving the frame along die stainless steel tube, wherein the stainless steel tube is not rotated. 
     
     
         10 . A method of shot peening an inner surface of a stainless steel tube according to  claim 9 , wherein the frame comprises, in a radial direction, movable segments, and the method further comprises the steps of attaching the electromagnets to the movable segments, and moving at least a portion of the segments radially, while moving the frame along a curved portion of the stainless steel tube. 
     
     
         11 . A method of shot peening an inner surface of a stainless steel tube according to  claim 1 , further comprising the step of providing at least two magnetic shot particles inside the stainless steel tube. 
     
     
         12 . An apparatus tor shot peening an inner surface of a stainless steel tube, the apparatus comprising:
 a set of at least two electromagnets arranged around the stainless steel tube and having an iron core with an air gap adjacent to the stainless steel tube;   at least one magnetic shot particle provided inside the stainless steel tube, and   a controller for controlling the activation of the electromagnets according to a predetermined sequence, so as to cause the at least one magnetic shot particle to repeatedly hit the inner surface of the tube so as to shot peen the inner surface.   
     
     
         13 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising a rotating device for rotating the stainless steel tube around its axis, and a transfer device tor moving the set of electromagnets relative to the stainless steel tube in the direction of the axis of the stainless steel tube. 
     
     
         14 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 13 , further comprising a frame, in which frame, the set of at least two electromagnets is attached, and which frame is movable in the direction of the axis of the stainless steel tube. 
     
     
         15 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising a set of at least six electromagnets arranged symmetrically outside an outer periphery of the stainless steel tube, which stainless steel tube is fixed. 
     
     
         16 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 15 , wherein the set of multiple electromagnets comprises at least eight electromagnets. 
     
     
         17 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising (i) a frame, in which frame, the set of at least two electromagnets is attached, (ii) a rotating device for rotating the frame around the stainless steel tube, and (iii) a transfer device for moving the frame along the stainless steel tube. 
     
     
         18 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 17 , wherein the rotating device is arranged to rotate the frame back and forth around the stainless steel tube. 
     
     
         19 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising a set of multiple electromagnets arranged on at least two adjacent rings outside the stainless steel tube, which stainless steel tube is fixed. 
     
     
         20 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising (i) a frame, in which frame, the set of at least two electromagnets is attached, and (ii) a transfer device for moving the frame along the stainless steel tube, which stainless steel tube is fixed. 
     
     
         21 . An apparatus tor shot peening an inner surface of a stainless steel tube according to  claim 20 , wherein the frame comprises, in a radial direction, movable segments for movable attaching the electromagnets to the frame. 
     
     
         22 . An apparatus for shot peening an inner surface of a stainless steel tube according to  claim 12 , further comprising at least two magnetic shot particles inside the stainless steel tube.