Weld deposition

Ferrous-aUoy-clad tube sheets are generally prepared by a weld overlay process in which the alloy material is deposited by welding upon the face of the tube sheet. Precautions are required to produce a weld deposit free of defects, since these may permit the process fluid to attack the base metal below the alloy. Copper-aUoy-clad tube sheets are prepared by brazing the alloy to the carbon steel backing material. 

Figure 15.13 Cracking in weld deposit caused by lamination in steel base metal. (Reprinted with permission from Helmut Thielsch, Defects and Failures in Pressure Vessels and Piping, New York, Van Nostrand Reinhold, 1965.)...

There is no guarantee that crack-free joints will automatically be obtained when fabricating weldable metals. This is a result of the fact that weldability is not a specific material property but a combination of the properties of the parent metals, filler metal (if used) and various other factors (Table 9.7) . The consequence of the average structural material possessing imperfect weldability is to produce a situation where defects may arise in the weld deposit or heat-affected zone (Table 9.8 and Fig. 9.27). 

Hydrogen Controlled Electrode a covered electrode which, when used correctly, produces less than a specified amount of diffusible hydrogen in the weld deposit. 

Bruscato, R., Temper Embrittlement and Creep Embrittlement of 2.25Cr-lMo Shielded Metal-Arc Weld Deposits, Weld. J. 49, Res. Suppl., pp 148-s -156-s, April 1970. 

A listed material may be used at any temperature not lower than the minimum shown in the tables in Appendix IX, provided that the base metal, weld deposits, and heat affected zone (HAZ) are qualified as required by the applicable entry in Column A of Table GR-2.1.2(b)(2). 

B-l Except as provided in Notes (2) and (3), heat treat base metal per applicable ASTM specification listed in para. GR-2.1.3(b) then impact test base metal, weld deposits, and HAZ per para. GR-2.1.3 [see Note (1)1. When materials are used at design min. temp, below the assigned curve as permitted by Notes (1) and (2) of Fig. GR-2.1.2(b)A, weld deposits and HAZ shall be impact tested [see Note (1)1. 

B-3 Engineering design shall be assured by suitable tests [see Note (5)] that base metal, weld deposits, and HAZ are suitable at the design min. temp. 

Consumable inserts may be used, provided they are of the same nominal composition as the filler metal and will not cause detrimental alloying of the subsequent weld deposit. The welding procedure using consumable inserts shall be qualified as required by para. GR-3.2.4. The consumable insert shall be used for welding the root pass of butt welded pipe components requiring complete weld joint penetration (CWJP) utilizing the GTAW or PAW processes. 

Fig. GR-3.4.4(a) Geometry of Weld Deposit Single Vee Groove Butt, Open Root...

GENERAL NOTE The weld deposit connecting the pipe end to the flange face at the I.D. shall not result in a weld buildup or undercut of the flange face surface. 

B Lack of fusion and incomplete penetration None of weld deposit or weld deposit to BM... 

C Surface porosity inclusions, slag or tungsten None of weld deposit... 

NOTE For chromium-nickel materials, extreme discoloration of the weld deposit or heat affected zone shall not be allowed. Acceptable coloration includes light straw, light blue, or hueing. 

Stellite (Cabot Corp.) (or the equivalent), Colmonoy (Wall-Colmonoy Corp.) (or the equivalent), Type 3 tungsten carbide, etc. overlay-weld deposit of 0.8 mm (0.030 in.) minimum finished thickness, or, if available, a solid cast part of equal material may be substituted. 

Aluminum, copper, nickel, and their alloys unalloyed titanium A-6 (a) No additional requirements A-6 (b) No additional requirements unless filler metal composition is outside the range for base metal composition then test per column B-6 B-6 Designer shall be assured by suitable tests [see Note (4)] that base metal, weld deposits, and HAZ are suitable at the design min. temp. 

Hardfaeing and Wear-resistant Alloys. These materials, essentially quaternary alloys of cobalt chromium, tungsten (or molybdenum) and carbon, are widely used for industrial hardfaeing purposes. They can be deposited by welding techniques, sprayed on as powders, or produced as separate castings. By using the weld deposition technique, a highly alloyed heat-, wear-, and corrosion-resistant surface can be applied to a... 

From an engineering standpoint, the ability to weld stainless steels with relative ease is a major advantage to their usefulness. Weld deposits, because they are cast structures, are subject to discussion regarding corrosion resistance similar to the cast materials. The chemistry of a weld deposit is likely to exhibit segregation and, depending on the alloy and the welding technique employed, may develop deleterious secondary phases in either the weld or heat-affected zone. 

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