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ASME B31.3-2016 <br /> Designer,welding electrodes and filler metals used shall 328.4.2 End Preparation <br /> produce weld metal that complies with the following: (a) General <br /> (a) The nominal tensile strength of the weld metal (1) End preparation is acceptable only if the surface <br /> shall equal or exceed the minimum specified tensile is reasonably smooth and true, and slag from oxygen <br /> strength of the base metals being joined, or the weaker or arc cutting is cleaned from thermally cut surfaces. <br /> of the two if base metals of two different strengths are Discoloration remaining on a thermally cut surface is <br /> being joined. not considered detrimental oxidation. <br /> (b) The nominal chemical analysis of the weld metal (2) End preparation for groove welds specified in <br /> shall be similar to the nominal chemical analysis of the ASME B16.25,or any other that meets the WPS,is accept- <br /> major alloying elements of the base metal(e.g.,21/4%Cr, able. [For convenience, the basic bevel angles of <br /> 1% Mo steels should be joined using 21/4/o Cr, 1% Mo ASME B16.25 and some the <br /> J-bevel angles are <br /> filler metals). shown in Fig. 328.4.2,illustrations (a) and (b).] <br /> (c) If base metals of different chemical analysis are (b) Circumferential Welds <br /> being joined,the nominal chemical analysis of the weld (1) If component ends are trimmed as shown in <br /> metal shall be similar to either base metal or an interme- Fig. 328.3.2,illustration (a) or (b) to fit backing rings or <br /> diate composition,except as specified below for austen- consumable inserts,or as shown in Fig.328.4.3,illustra- <br /> itic steels joined to ferritic steels. tion (a) or (b) to correct internal misalignment, such <br /> (d) When austenitic steels are joined to ferritic steels, trimming shall not reduce the finished wall thickness <br /> the weld metal shall have a predominantly austenitic below the required minimum wall thickness,tm. <br /> microstructure. <br /> (e) For nonferrous metals,the weld metal shall be that (2) Component ends may be bored to allow for a <br /> completely recessed backing ring, provided the <br /> recommended by the manufacturer of the nonferrous remaining net thickness of the finished ends is not less <br /> base metal or by industry associations for that metal. than tm. <br /> 328.3.2 Weld Backing Material. When backing rings (3) It is permissible to size pipe ends of the same <br /> are used, they shall conform to the following: nominal size to improve alignment if wall thickness <br /> (a) Ferrous Metal Backing Rings. These shall be of requirements are maintained. <br /> weldable quality. Sulfur content shall not exceed 0.05%. (4) Where necessary,weld metal may be deposited <br /> (b) If two abutting surfaces are to be welded to a third inside or outside of the component to permit alignment <br /> member used as a backing ring and one or two of the or provide for machining to ensure satisfactory seating <br /> three members are ferritic and the other member or of rings or inserts. <br /> members are austenitic, the satisfactory use of such (5) When a girth or miter groove weld joins compo- <br /> materials shall be demonstrated by welding procedure nents of unequal wall thickness and one is more than <br /> qualified as required by para. 328.2. 11/2 times the thickness of the other,end preparation and <br /> Backing rings may be of the continuous machined or geometry shall be in accordance with acceptable designs <br /> split-band type.Some commonly used types are shown for unequal wall thickness in ASME B16.25. <br /> in Fig. 328.3.2. (6) Buttweld fittings manufactured in accordance <br /> (c) Nonferrous and Nonmetallic Backing Rings. Backing with ASME B16.9 may be trimmed to produce an angular <br /> rings of nonferrous or nonmetallic material maybe used, joint offset in their connections to pipe or to other butt- <br /> provided the designer approves their use and the weld- weld fittings without being subject to design qualifica- <br /> ing procedure using them is qualified as required by tions in accordance with para.304.7.2 provided the total <br /> para. 328.2. angular offset produced between the two jointed parts <br /> 328.3.3 Consumable Inserts. Consumable inserts does not exceed 3 deg. <br /> may be used, provided they are of the same nominal 328.4.3 Alignment (16) <br /> composition as the filler metal,will not cause detrimen- (a) Circumferential Welds <br /> tal alloying of the weld metal,and the welding procedure (1) Inside surfaces of components at ends to be <br /> using them is qualified as required by para.328.2.Some joined in girth or miter groove welds shall be aligned <br /> commonly used types are shown in Fig. 328.3.2. within the dimensional limits in the WPS and the engi- <br /> 328.4 Preparation for Welding neering design. <br /> (2) If the external surfaces of the components are <br /> 328.4.1 Cleaning. Internal and external surfaces to not aligned, the weld shall be tapered between them. <br /> be thermally cut or welded shall be clean and free from (b) Longitudinal Welds. Alignment of longitudinal <br /> paint, oil,rust, scale,and other material that would be groove welds (not made in accordance with a standard <br /> detrimental to either the weld or the base metal when listed in Table A-1, Table A-IM, or Table 326.1) shall <br /> heat is applied. conform to the requirements of para. 328.4.3(a). <br />