METHODS FOR OVERCOMING WELD SKILL LIMITATIONS
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MECHANICAL WELDING BACKING METHODS FOR OVERCOMING WELD SKILL m fusion welded joints, n is expense nt ensuring lulls continuous transition of metal between parent materials. The fillet Welti anil the partial penetrating hint weld usually are adequate; etnployetl intelligentIv. they can meet many structural re quirements. Fur this reason, they are manufacturing industry. For some demanding applications, however, maximum joint strength is mandatory. Products subjected to me- chanical fatigue, corrosion, or ther- mal cycling in end-uset Industries such as nuclear engineering, aero- space, and power generation need joints of optimum quality to provide an acceptable level of insurance against service failure. For these criti- cal applications, a fully penetrating hutt weld is essential. art process determines whether or not a square edge preparation i- ade quate. With the manual metal arc (GTAW) techniques, rhe maximum material thickness that can he weld- ed from one side usually is about 5 millimeters. Using a high-current gas metal arc welding (GMAW) tech- nique allows this thickness to he in- creased to about 6 millimeters. For thicker materials, the edges must he cut back lo pnwide access tor the torch. The simplest preparation of this type is the single V, and the joint is filled using a multiple run, with each pass tuning into the pre- vious one and into the adjacent side walls. The first pass is referred to as the root run. ami the quality of this deposit ultimately determines the overall quality of the finished joint. It provides continuous lusion between the two materials along their length, and this can he achieved in a number Tile most direct technique is tor the welder to exercise total control over the deposit, producing an ac-

Ceramic Tile Backing ceptahly smooth underhead ot con- stant width with no significant sur- face oxidation. The remt gap plays an imporranr pnrt here in ensuring con- sistency of penetration: too wide re- sults in overpenetration. while too small causes inadequate penetration. Achieving consistency requires a lev- el of skill on the part of the welder that is not always availahle. Weld Backing To counter this need tor .1 high lev- el oi welder skill, mechanical meth- yls of weld-based control have lieen developed. If the rear of the joint can he accessed, the external head protile...

common grades of stainless steel* hur some ol the nickel iilloys, such .1* MONEL' alloy, INCONEL' alloy, ami Typical inserts are known as A- shape. EB-, J-, and K-rype inserts (see Figure 4). Availability of these in- serts depends on the availability of the raw materials in the form required Although originally intended to he used to butt weld tube with the CTAW process, inert gas Kicking lias been extended to linear hurt welds (see Figure 5). When nominal gas joint seam, a gas pressure is created under the head that is sufficient to provide protection from contamina- ten metal. Inert gas...

WELD BACKING TAPE Extending the Argweld ® range of purging products, Huntingdon Fusion Techniques are providing an economical non metallic weld backing system for the backing of welds, where purging is required but not easily achieved, for quality and for supporting weld roots to improve weld bead profiles. Typically for the welding of thin wall stainless steel sheet and vessels from one side only, the backing tape can be attached to the backside of the weld, to support the weld pool, keep the argon from the weld torch surrounding the weld pool and eliminate the need to back purge, while...