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Page 29-1
The Metallurgy of Welding; Welding Design and Process
Selection
CHAPTER 7-3
Page 29-2
Fusion Weld Zone
Figure 29.1 Characteristics of a typical fusion weld zone in oxyfuel gas and arc welding. See also Figs. 27.16 and 28.14.
Page 29-3
Grain Structure in Shallow and Deep Welds
(a) (b)
Figure 29.2 Grain structure in (a) a deep weld (b) a shallow weld. Note that the grains in the solidified weld metal are perpendicular to the surface of the base metal. In a good weld, the solidification line at the center in the deep weld shown in (a) has grain migration, which develops uniform strength in the weld bead.
Page 29-4
Incomplete Fusion
Figure 29.6 Low-quality weld beads, the result of incomplete fusion. Source: American Welding Society.
Page 29-5
Discontinuities in Fusion Welds
Figure 29.7 Schematic illustration of various discontinuities in fusion welds. Source: American Welding Society.
Page 29-6
Cracks in Welded Joints
Figure 29.8 Types of cracks (in welded joints) caused by thermal stresses that develop during solidification and contraction of the weld bead and the surrounding structure. (a) Crater cracks. (b) Various types of cracks in butt and T joints.
Page 29-7
Distortion After Welding
Figure 29.10 Distortion of parts after welding: (a) butt joints; (b) fillet welds. Distortion is caused by differential thermal expansion and contraction of different parts of the welded assembly.
Page 29-8
Residual Stresses Developed During Welding
Figure 29.11 Residual stresses developed during welding of a butt joint. Source: American Welding Society.
Page 29-9
Overview of Commercial Joining Processes
TABLE 29.1 Overview of Commercial Joining Processes*Joining Process
Brazing
MaterialThick-
ness
SMAW
SAW
GMAW
FCAW
GTAW
PAW
ESW
EGW
RW
FW
OFW
DFW
FRW
EBW
LBW
TB
FB
IB
RB
DB
IRB
DFB
Carbon steel SI
MT
xxxx
xxxx
xxxx
xxx
xx
x x
xxx
xxxx
xxxx
xxx
xxxx
xxx
xxx
xxxx
xxx
xx
xx
x xxxx
Low-alloysteel
SI
MT
xxxx
xxxx
xxxx
xxx
xx
x
xx
x
xxxx
x xxxx
xxx
xxxx
xxx
xxxx
xxx
xxx
x x x xxx
Stainlesssteel
SI
MT
xxxx
xxxx
xxxx
xxx
xx
x
xxx x
xx
xxxx
x xxxx
xxx
xxxx
xxx
xxx
xxxx
xxx
x x x xxxx
Cast iron IMT
xxx
xx
xx
xx
xxx
xx
xxx
xx
xxx
Nickel andalloys
SI
MT
xxxx
xx
xxxx
xx
xxx
x
xx
xxxx
xxxx
xxxx
xxx
xxx
xxxx
xx
x x x xxxx
Page 29-10
Overview of Commercial Joining Processes (cont.)
TABLE 29.1 (continued)Joining Process
Brazing
MaterialThick-
ness
SMAW
SAW
GMAW
FCAW
GTAW
PAW
ESW
EGW
RW
FW
OFW
DFW
FRW
EBW
LBW
TB
FB
IB
RB
DB
IRB
DFB S
Aliminumand alloys
SI
MT
xxxx
xxxx
xxx
x
x x
xx
xxxx
x xx
xxx
xxxx
xx
xxx
xxxx
x x xxx
x xxxx
xx
Titaniumand alloys
SI
MT
xxxx
xxx
xxx
x xxxx
xxxx
xx
xxxx
xxx
x
xxxx
x x xxxx
Copper andalloys
SI
MT
xxxx
x xx
xxxx
xx
xxxx
xxx
xxxx
x xx
xxxx
xx
Magnesiumand alloys
SI
MT
xxxx
xx
xx x
xx
xx
xxxx
xxx
xx
xxx
xx
xxx
Refractoryalloys
SI
MT
xx
x xx
x
x
xxx
xx
xx
xx
x x x xx
*This table is presented as a general survey only. In selecting processes to be used with specific alloys, the readershould refer to otherappropriate sources of information.Source: Courtesy of the American Welding Society.
Page 29-11
Overview of Commercial Joining Processes (cont.)
TABLE 29.1 (continued)
LegendProcess code Thickness
SMAW—Shielded Metal-Arc WeldingSAW—Submerged Arc WeldingGMAW—Gas Metal-Arc WeldingFCAW—Flux-Cored Arc WeldingGTAW—Gas Tungsten-Arc WeldingPAW—Plasma Arc WeldingESW—Electroslag WeldingEGW—Electrogas WeldingRW—Resistance WeldingFW—Flash WeldingOFW—Oxyfuel Gas WeldingDFW—Diffusion Welding
FRW—Friction WeldingEBW—Electron Beam WeldingLBW—Laser Beam WeldingTB—Torch BrazingFB—Furnace BrazingIB—Induction BrazingRB—Resistance Brazing DB—Dip BrazingIRB—Infrared BrazingDFB—Diffusion BrazingS—Soldering
S—Sheet: up to 3 mm in.BI—Intermediate: 3 to 6 mm A in.BM—Medium: 6 to 19 mm A in.BT—Thick: 19 mm A in. B and up
Page 29-12
Destructive Techniques
Figure 29.12 Two types of specimens for tension-shear testing of welded joints.
Figure 29.13 (a) Wrap-around bend test method. (b) Three-point bending of welded specimens--see also Fig. 2.11.
Page 29-13
Testing of Spot Welds
Figure 29.14 (a) Tension-shear test for spot welds. (b) Cross-tension test. (c) Twist test. (d) Peel test; see also Fig. 30.8.
Page 29-14
Welding Design Guidelines
Figure 29.15 Design guidelines for welding. Source: J. G. Bralla (ed.), Handbook of Product Design for Manufacturing. Copyright ©1986, McGraw-Hill Publishing Company. Used with permission.
Page 29-15
Standard Identification and Symbols for Welds
Figure 29.16
Page 29-16
Weld Design Selection
Figure 29.17