• B.H.N.

    Abbreviation for Brinell Hardness Number.

  • B.T.U.

    See BRITISH THERMAL UNIT.

  • BABBITT

    Babbitt is a term applied to a series of tin-base alloys used for bearings. These relatively soft, low friction alloys are composed essentially of tin, with additions of antimony and copper to increase hardness, strength and fatigue resistance. The amount of lead in these alloys is usually limited to 0.35% to 0.50% to prevent formation of a lead-tin eutectic which reduces strength.

    The basic composition range of these tin-base babbitts is 75% to 95% tin, 2% to 10% copper, and 2% to 10% antimony. Lead-base babbitts containing up to 10% tin and 12% to 18% antimony are used for bearings, but do not have the strength of the tin-base babbitts.

    Babbitt is frequently melted with an air-fuel gas or oxyfuel gas flame prior to pouring. A similar flame is often used to melt babbitt from bearings and bearing caps for re-babbitting.

  • BACK BEAD

    A weld bead resulting from a back weld pass. See STANDARD WELDING TERMS.

  • BACK BEND

    See GUIDED BEND TEST.

  • BACK CAP

    A device used to exert pressure on the collet to hold the electrode in a gas tungsten arc welding torch and create a seal to prevent air from entering the back of the torch. See STANDARD WELDING TERMS.

  • BACK WELD

    A weld made at the back of a single groove weld. See STANDARD WELDING TERMS. See also Figure B-5.

  • BACKFIRE

    The momentary recession of the flame into the welding tip or cutting tip followed by immediate reappearance or complete extinction of the jlame, accompanied by a loud report. See STANDARD WELDING TERMS.

  • BACKGOUGING

    The removal of weld metal and base metal from the weld root side of a welded joint to facilitate complete fusion and complete joint penetration on subsequent welding from that side. See STANDARD WELDING TERMS

  • BACKHAND WELDING

    A welding technique in which the welding torch or gun is directed opposite to the progress of welding. See STANDARD WELDING TERMS. See also TRAVEL ANGLE, See WORK ANGLE, and DRAG ANGLE.

    Backhand welding is sometimes referred to as the “pull gun” technique in gas metal arc (GMAW) and flux core arc welding (FCAW).

  • BACKING

    A material or device placed against the back side of the joint, or at both sides of a weld in electroslag and electrogas welding, to support and retain molten weld metal. The material may be partially fused or remain unfused during welding and may be either metal or nonmetal. See STANDARD WELDING TERMS. See also Figure B- 1.

  • BACKING BEAD

    A weld bead resulting from a backing pass. See STANDARD WELDING TERMS

  • BACKING FILLER METAL

    A nonstandard term for CONSUMABLE INSERT.

  • BACKING PASS

    A weld pass made for a backing weld. See STANDARD WELDING TERMS.

  • BACKING RING

    Backing in the form of a ring, generally used in the welding of pipe. See STANDARD WELDING TERMS.

    A backing ring helps maintain correct alignment of the pipe or tube ends during welding, and assures complete fusion to the root of the joint without the formation of slag, icicles, or spatter within the bore. The backing ring can be made from a strip of metal which is formed into a ring and fitted to the inside surface of a pipe or tube prior to welding. The ring should be substantially the same chemical composition as the pipe or tube to be welded.

  • BACKING SHOE

    A nonconsumable backing device used in electroslag and electrogas welding that remains unjused during welding. See STANDARD WELDING TERMS.

  • BACKING STRIP

    Backing in the form of a strip of metal, carbon, or ceramic to retain molten metal at the root of a weld.

  • BACKING WELD

    Backing in the form of a weld. See STANDARD WELDING TERMS. See also Figure B-2.

  • BACKING, Split-Pipe

    Backing in the form of a pipe segment used for welding round bars.

  • BACKSTEP SEQUENCE

    A longitudinal sequence in which weld passes are made in the direction opposite to the progress of welding. See STANDARD WELDING TERMS. See also Figure B-3.

    The backstep sequence is a welding technique used to prevent accumulation of stresses and distortion by distributing deposited weld metal. This method consists of dividing the weld into short increments, and depends on depositing the weld metal in a direction opposite to the direction of progression. The welds may be made in the sequence shown in Figure B-3, or this sequence may be changed. For example, the welds may be made in the order of 1, 2, 3, 4, 5, 6, etc., or 1, 3, 5, 2, 4, 6, etc. The latter is an illustration of the skip backstep method, which is a combination of skip and back-step welding. In skip backstep welding the welds may be made in any convenient order. See BLOCK SEQUENCE, CASCADE SEQUENCE, CONTINUOUS SEQUENCE, CROSS SECTIONAL SEQUENCE, and LONGITUDINAL SEQUENCE.

  • BACKSTEP WELDING

    See BACKSTEP SEQUENCE.

  • BACKUP BARS AND PLATES

    Backing material used to retain molten metal or to assure complete fusion. Successful welding of various materials often depends on the type of backup bar or plate that is used. The high heat conductivity of a copper backup bar or plate, for example, will prevent it from sticking to the weld metal, while its chill-mold effect will assure a clean, smooth weld metal surface.

    Electrolytic copper has proven to be the most satisfactory material for backing up a weld.

    Copper backup bars are usually made by cutting pieces from copper plate or sheet. Electrolytic copper in cold rolled bars and plates is available in a variety of sizes for these applications. While these copper pieces give more satisfactory results than other backing materials, they must be made carefully to provide accurate dimensions and good surfaces.

    Figure B-4 illustrates the use of a copper backup bar to obtain a full penetration weld in heavy plate.

  • BACKUP, Flash and Upset Welding

    A locator used to transmit all or a portion of the upset force to the workpieces or to aid in preventin gthe workpieces from slipping during upsetting. See STANDARD WELDING TERMS.

  • BACKWARD WELDING

    A British term for BACKHAND WELDING.

  • BALANCED PRESSURE TORCH

    An oxyacetylene torch that operates under equal, or balanced, pressures for oxygen and acetylene, from 7 to 100kPa (1 to 15 psig), with the capability of supplying oxygen in pressures up to 170 Wa (25 psig). The ports at the entrance to the mixing chamber are equal in area, and deliver equal volumes of gases at equal pressures to the mixing chamber.