GB1474181A - Welding method including backgrinding - Google Patents

Abstract

1474181 Welding by fusion and grinding REDPATH DORMAN LONG Ltd 26 April 1974 [26 April 1973] 19957/73 Headings B3R and B3D In a method of joining two metal plate edges by welding at least one edge to be joined is chamfered, as at 51 in Fig. 11, to leave a root face 11, Figs. 2 and 9, on that edge. The root face is abutted with a flat surface on the adjacent edge of the other plate forming a V groove on one side of the abutting surfaces. The groove is then welded at 53, Fig. 11, and metal is then removed from the other side of the abutting surfaces until the surfaces are completely removed, e.g. as shown at 16 in Fig. 5, to expose the inner portion of the weld metal. Finally, further weld material 13a, Fig. 6, is deposited in place of the removed metal. In at least the final stages of the metal removal step the metal is ground out by a high speed grinding wheel 15, Fig. 9, arranged to exert a substantially constant pressure on the metal to be removed, having a substantially constant speed of advance and having its axis maintained in a direction perpendicular to the direction of the weld. The weld metal may be initially removed by back-gouging e.g. arc-air gouging or flame gouging. In addition to forming chamfer 51, in Fig. 11, a chamber 54 may be formed on the other edge. Further chamfers 55 and/or 56 may be formed on the rear side of the plate edges to form a 'V'-groove 52 on the rear side which may have an angle of 90 degrees, while the first groove may be 60 degrees. The included angle of the edge of the grinding wheel is chosen to be less than that of groove 52 e.g. 40-70 degrees and preferably 60 degrees. The wheel may be resinoid having a root radius of 3/16 inches and capable of speeds of 9,500 surface feet per minute. A suitable apparatus for carrying out the grinding step on circumferential welds of drilling rig tubulars is shown in Fig. 7, wheel 15 is rotatably supported on an arm 16a pivotally supported between blocks 18 of supporting structure 19, 20 by means of a linear bearing which allows axial float. The wheel is counterbalanced by driving motor 17 and is urged into contact with the weld by the operator by means of handles 21. In the modification of Fig. 8 the wheel is urged upwardly by a pneumatic cylinder 22 under the control of the operator by means of valve 27. A hydraulic damper 31 is also provided. For grinding longitudinal welds on tubulars, the apparatus shown in Fig. 10 may be used. A column-supported boom 33 carries a bracket 39 pivotally supporting an arm 35 which carries a motor for driving via a chain drive, the wheel 37 which is supported with casing 38 on an arm 39 pivoted to arm 35. The depth of the wheel is controlled by adjuster 40 on pivoted L-shaped arm 41 carrying depth control wheel 42. Other conventional adjustments include tilt and position of the grinding wheel and means to reform the grinding edge-of the wheel.