MIL-HDBK-5: Chapter 8.2 — Metallurgical Joints
Chapter 8.2 Contents
8.2Metallurgical Joints 8.2.1Introduction and Definitions 8.2.2Welded Joints 8.2.2.1Fusion Welding—Arc and Gas 8.2.2.1.1Strength of Fusion Welded Joints of Steel Alloys 8.2.2.2Flash and Pressure Welding 8.2.2.3Spot and Seam Welding 8.2.2.3.1Design Shear Strengths for Spot and Seam Welds in Uncoated Steels and Nickel and Cobalt Alloys 8.2.2.3.1.1Effects of Spot-Welds on the Parent Metal Strength of 300 Series Stainless Steel 8.2.2.3.2Design Shear Strengths for Spot and Seam Weldings in Aluminum Alloys 8.2.2.3.2.1Effects of Spot Welds on Parent Metal Strength of Aluminum Alloys 8.2.2.3.2.2Fatigue Strength of Spot-Welded Joints in Aluminum Alloys 8.2.2.3.3Design Shear Strengths for Spot and Seam Welds in Magnesium Alloys 8.2.2.3.4Design Shear Strengths for Spot and Seam Welds in Titanium and Titanium Alloys 8.2.3Brazing 8.2.3.1Copper Brazing 8.2.3.2Silver Brazing
Navigate to Section
Chapter 1 — General Chapter 2 — Steel Chapter 3 — Aluminum Chapter 4 — Magnesium Chapter 5 — Titanium Chapter 6 — Heat-Resistant Alloys Chapter 7 — Miscellaneous Alloys Chapter 8 — Structural Joints 8.1 — Fastened Joints 8.2 — Metallurgical Joints 8.3 — Bearings, Pulleys, Wire Rope Appendix B & C — Alloy & Spec Index
Disclaimer

For reference use only. The formulas, graphs, and values herein are provided in good faith for general engineering guidance. Please verify all data against MIL-HDBK-5J or the applicable superseding document (MMPDS).

Figures and Tables
Table of Tables
Table 8.2.2.1.1(a)Strength of Fusion Welded Joints of Steel Alloys Table 8.2.2.1.1(b)Allowable Ultimate Tensile Stresses Near Fusion Welds in 4130, 4140, or 8630 Steels Table 8.2.2.1.1(c)Allowable Bending Modulus of Rupture Near Fusion Weld in 4130, 4140, 4340, or 8630 Steels Table 8.2.2.2(a)Allowable Ultimate Tensile Stress for Flash Welds in Steel Tubing Table 8.2.2.2(b)Allowable Bending Modulus of Rupture for Flash Welds in Steel Tubing Table 8.2.2.3Recommended Minimum Edge Distance and Spacing for Spot-Welded Joints Table 8.2.2.3.1(a)Spot-Weld Design Shear Strength in Thin Sheet and Foil for Uncoated Steels and Nickel and Cobalt Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.1(b)Spot-Weld Design Shear Strength in Panels for Uncoated Steels and Nickel and Cobalt Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.2(a)Acceptable Aluminum and Aluminum Alloy Combination for Spot and Seam Welding Table 8.2.2.3.2(b)Spot-Weld Design Shear Strength in Thin Sheet and Foil for Bare and Clad Aluminum Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.2(c)Spot-Weld Design Shear Strength in Panels for Bare and Clad Aluminum Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.2(d)Maximum Static Strength of Spot-Welded Joints in Aluminum Alloys and Corresponding Maximum Design Spot-Weld Pitch Table 8.2.2.3.3Spot-Weld Design Shear Strength in Panels for Magnesium Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.4(a)Spot-Weld Design Shear Strength in Thin Sheet and Foils for Titanium and Titanium Alloys (Welding Specification MIL-W-6858) Table 8.2.2.3.4(b)Spot-Weld Design Shear Strength in Panels for Titanium and Titanium Alloy (Welding Specification MIL-W-6858)
Table of Figures
Fig 8.2.1Schematic diagram of weld and parent metal Fig 8.2.2.3.1.1(a)Efficiency of the parent metal in tension for spot-welded AISI 301-A, and AISI 347-A, and AISI 301-1/4 stainless steel Fig 8.2.2.3.1.1(b)Efficiency of the parent metal in tension for spot-welding AISI 301-1/2H stainless steel Fig 8.2.2.3.1.1(c)Efficiency of the parent metal in tension for spot-welded AISI 301-H stainless steel Fig 8.2.2.3.2.1Efficiency of the parent metal in tension for spot-welded aluminum alloys Fig 8.2.2.3.2.2(a)Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by tearing sheet) Fig 8.2.2.3.2.2(b)Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds) Fig 8.2.2.3.2.2(c)Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05 Fig 8.2.2.3.2.2(d)Fatigue strength of spot-welded multiple row joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds) Fig 8.2.2.3.2.2(e)Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05 (static failure by tear in sheets)
8.2Metallurgical Joints

In the design of metallurgical joints, the strength of the joining material (for example, weld metal) and the adjacent parent material must be considered. The joint should be analyzed on the basis of its loading, the specified allowable strengths, dimensions and geometry.

8.2.1Introduction and Definitions

The allowable strength for both the adjacent parent metal and the weld metal is given below in the particular section dealing with the method of forming used, and the material being joined. The following subparagraphs define certain joining processes.

Welding — Welding consists of joining two or more pieces of metal by applying heat, pressure or both, with or without filler material, to produce a localized union through fusion or recrystallization across the joint interface. Examples of common welding processes include: fusion [inert-gas, shielded-arc welding with tungsten electrode (TIG) and inert-gas shielded metal-arc welding using covered electrodes (MIG)], resistance (spot and seam), and flash. Several terms used in describing various sections of a welded joint are illustrated in Figure 8.2.1.

Brazing — Brazing consists of joining metals by the application of heat causing the flow of a thin layer, capillary thickness, of nonferrous filler metal into the space between the pieces. Bonding results from the intimate contact produced by the dissolution of a small amount of base metal in the molten filler metal, without fusion of the base metal.

Open this page of MIL-HDBK-5
Figure 8.2.1 — Schematic diagram of weld and parent metal. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1382).

Figure 8.2.1. Schematic diagram of weld and parent metal.

8.2.2Welded Joints

The weld metal section of a joint should be analyzed on the basis of its loading, specified allowable strength, dimensions and geometry. The effects of the parent metal are to be accounted for as specified herein.

8.2.2.1Fusion Welding—Arc and Gas

Section 9.4.2 contains a detailed discussion of one acceptable method of establishing fusion welding allowables. As stated in that section, other methods can be employed as approved by certifying agencies. The following subsections contain specific information for a number of materials.

8.2.2.1.1Strength of Fusion Welded Joints of Steel Alloys

Allowable fusion weld-metal strengths of steel alloys are shown in Table 8.2.2.1.1(a). Design allowable stresses for the weld metal are based on 85 percent of the respective minimum tensile ultimate test values.

For steel joints welded after heat treatment, the allowable strengths near the weld are given in Tables 8.2.2.1.1(b) and (c).

For materials heat treated after welding, the allowable strength in the parent metal near a welded joint may equal the allowable strength for the material in the heat treated condition as given in the tables of design mechanical properties of the specific alloys; however, it should be noted that the weld metal allowables are based on 85 percent of these values.

Open this page of MIL-HDBK-5
Table 8.2.2.1.1(a). Strength of Fusion Welded Joints of Steel Alloys
MaterialHeat Treatment
Subsequent to Welding		Welding Rod
or Electrode		Fsu, ksiFtu, ksi
Carbon and alloy steelsNoneAMS 64573251
AWSA5.1 classes E6010 and E60133251
Alloy steelsNoneAMS 64524372
Alloy steelsStress relievedAWSA5.5 class E10013
MIL-E-22200/10, classes MIL-10018-M1		5085
Open this page of MIL-HDBK-5
Table 8.2.2.1.1(b). Allowable Ultimate Tensile Stresses Near Fusion Welds in 4130, 4140, or 8630 Steelsa
Section Thickness ¼ inch or less
Type of JointUltimate Tensile Stress, ksi
Tapered joints of 30° or lessb90
All others80
a Welded after heat treatment or normalized after weld.
b Gussets or plate inserts considered 0° taper with centerline.
Open this page of MIL-HDBK-5
Table 8.2.2.1.1(c). Allowable Bending Modulus of Rupture Near Fusion Weld in 4130, 4140, 4340, or 8630 Steelsa
Type of JointBending Modulus of Rupture, ksi
Tapered joints of 30° or lessbFb from Figure 2.8.1.1 for Ftu = 90 ksi
All others0.9 of the values of Fb from Figure 2.8.1.1 for Ftu = 90 ksi
a Welded after heat treatment or normalized after weld.
b Gussets or plate inserts considered 0° taper with centerline.
8.2.2.2Flash and Pressure Welding

The ultimate tensile allowable strength and bending allowable modulus of rupture for flash and pressure welds are given in Tables 8.2.2.2(a) and (b). A higher efficiency may be permitted in special cases by the applicable procuring or certifying agency upon approval of the manufacturer’s process specification.

Open this page of MIL-HDBK-5
Table 8.2.2.2(a). Allowable Ultimate Tensile Stress for Flash Welds in Steel Tubing
TubingAllowable Ultimate Tensile Stress of Welds
Normalized tubing — not heat treated (including normalizing) after welding1.0 Ftu (based on Ftu of normalized tubing)
Heat-treated tubing welded after heat treatment1.0 Ftu (based on Ftu of normalized tubing)
Tubing heat treated (including normalizing) after welding. Ftu of unwelded material in heat-treated condition:
< 100 ksi0.9 Ftu
100 to 150 ksi0.6 Ftu + 30
> 150 ksi0.8 Ftu
Open this page of MIL-HDBK-5
Table 8.2.2.2(b). Allowable Bending Modulus of Rupture for Flash Welds in Steel Tubing
TubingAllowable Bending Modulus of Rupture of
Welds (Fb from Figure 2.8.1.1 using values
of Ftu listed)
Normalized tubing — not heat treated (including normalizing after welding1.0 Ftu (based on Ftu of normalized tubing)
Heat-treated tubing welded after heat treatment1.0 Ftu (based on Ftu of normalized tubing)
Tubing heat treated (including normalizing) after welding. Ftu of unwelded material in heat-treated condition:
< 100 ksi0.9 Ftu
100 to 150 ksi0.6 Ftu + 30
> 150 ksi0.8 Ftu
8.2.2.3Spot and Seam Welding

Permission to use spot and seam welding on structural parts is governed by the requirements of the procuring or certifying agency. Table 8.2.2.3 gives the recommended allowable edge distance for spot and seam welds.

Open this page of MIL-HDBK-5
Table 8.2.2.3. Recommended Minimum Edge Distance and Spacing for Spot-Welded Jointsa
Nominal Thicknessb
of Thinner Sheet, inch		Minimum Lap Jointc,d
Edge Distance, inch		Minimum Spacinge, inch
0.0160.190.19
0.0200.200.30
0.0250.220.38
0.0320.250.46
0.0400.280.52
0.0500.310.58
0.0630.380.67
0.0710.410.73
0.0800.440.79
0.0900.470.89
0.1000.501.00
0.1250.561.25
0.1600.691.60
a Reference Aluminum Association and American Welding Society Handbook.
b Intermediate gages will require interpolation between adjacent gages.
c Edge distances are measured materials in contact; this can be to a free edge or to a sheet metal radius where one material bends away from another. Edge distances less than those specified above may be used provided there is no expulsion of weld material or bulging of the edge of the sheet; however, these joints may have less static strength and shorter fatigue life.
Sketch for Table 8.2.2.3: edge distance e and overlap 2e of spot-welded joints (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1386).
8.2.2.3.1Design Shear Strengths for Spot and Seam Welds in Uncoated Steels and Nickel and Cobalt Alloys

The design shear strength for spot welds for these materials are given in Tables 8.2.2.3.1(a) and (b). The thickness ratio of the thickest sheet to the thinnest outer sheet in the combination should not exceed 4:1.

Open this page of MIL-HDBK-5
Table 8.2.2.3.1(a). Spot-Weld Design Shear Strength in Thin Sheet and Foil for Uncoated Steelsc and Nickel and Cobalt Alloys (Welding Specification MIL-W-6858)
Thickness of
Thinnest Outer
Sheet, in.		Spots/inchMaterial Ultimate Tensile Strength, ksi
Standard
(Ns)d		Rangee,fAbove 185150 to 18590 to 149Below 90
Design Shear Strength, pounds per linear inch (Xm)
0.001401-5072645236
0.002201-3014412810472
0.003121-17240208164120
0.004101-14324280228152
0.00591-13392340272188
0.00671-10432380304220
0.00761-8504440352256
0.00851-7552488392284
a Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
b The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
c Refers to plain carbon steels containing not more than 0.15 percent carbon, austenitic, heat and corrosion resistant, and precipitation hardening steels. The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
d When the number of spots per inch is within 15 percent of the standard spot per inch requirement, the design shear strengths tabulated above will apply.
e When the number of spots differs from the standard spots per inch by 15 percent or greater, but does not exceed the noted range of spots per inch, applicable design strength will be determined as noted below:
Xm/Ns (K) Nr = Xr
where
Xm = design shear strength in accordance with the above table
Ns = standard spots per inch in accordance with the above table
Nr = required spots per inch (production part)
Xr = actual design shear strength requirement
K = 1.15 when number of spots per inch is reduced more than 15 percent of the standard spacing of the above table
K = 0.90 when number of spots is increased more than 15 percent of the standard spacing but within range of the tabular spacing.
f When the number of spots per inch is above the range indicated in the table, the design shear strength will remain constant at the value obtained at the top of the range.
Open this page of MIL-HDBK-5
Table 8.2.2.3.1(b). Spot-Weld Design Shear Strength in Panels for Uncoated Steels and Nickel and Cobalt Alloys (Welding Specification MIL-W-6858)
Design Shear Strength, pounds per spot
Material Ultimate
Tensile Strength, ksi		Above
185		150 to
185		90 to
149		Below
90
Nominal thickness of thinner sheet, in.:
0.00916014010480
0.01019616412892
0.012280220160120
0.016384320236172
0.018472392272200
0.020508424312224
0.022584488360264
0.025696580424320
0.028820684508372
0.0321000836620452
0.03612001004736552
0.04014001168852652
0.045168014361028804
0.050196017001204956
0.0562304204014161168
0.0632840247216881408
0.0713360298420281664
0.0803880352824041964
0.0904480407228122308
0.1005040457632002640
0.1125600509236363036
0.1256228566440523440
a Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
b The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
c Refers to plain carbon steels containing not more than 0.15 percent carbon and to austenitic heat and corrosion resistant, precipitation hardening steels. The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
8.2.2.3.1.1Effects of Spot-Welds on the Parent Metal Strength of 300 Series Stainless Steel

In applications of spot welding where ribs, intercostals, or doublers are attached to sheet, either at splices or at other joints on the sheet panels, the allowable ultimate strength of the spot-welded stainless steel sheet will be determined by multiplying the ultimate tensile strength of the sheet (A or S-value) by the appropriate efficiency factors shown in Figures 8.2.2.3.1.1(a) through (c). Efficiencies for gages under 0.012 will be determined by test.

Open this page of MIL-HDBK-5
Figure 8.2.2.3.1.1(a) — Efficiency of the parent metal in tension for spot-welded AISI 301-A, and AISI 347-A, and AISI 301-1/4 stainless steel. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1389).

Figure 8.2.2.3.1.1(a). Efficiency of the parent metal in tension for spot-welded AISI 301-A, and AISI 347-A, and AISI 301-1/4 stainless steel.

Open this page of MIL-HDBK-5
Figure 8.2.2.3.1.1(b) — Efficiency of the parent metal in tension for spot-welding AISI 301-1/2H stainless steel. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1389).

Figure 8.2.2.3.1.1(b). Efficiency of the parent metal in tension for spot-welding AISI 301-1/2H stainless steel.

Open this page of MIL-HDBK-5
Figure 8.2.2.3.1.1(c) — Efficiency of the parent metal in tension for spot-welded AISI 301-H stainless steel. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1390).

Figure 8.2.2.3.1.1(c). Efficiency of the parent metal in tension for spot-welded AISI 301-H stainless steel.

8.2.2.3.2Design Shear Strengths for Spot and Seam Weldings in Aluminum Alloys

The acceptable aluminum and aluminum alloy combinations for spot and seam welding are given in Table 8.2.2.3.2(a).

Design shear-strength for spot welds in aluminum alloys are given in Tables 8.2.2.3.2(b) and (c). The thickness ratio of the thickest to the thinnest outer sheet in the combination should not exceed 4:1.

Design shear-strength for spot-welded joints, based on tearing of the sheet, is given in Table 8.2.2.3.2(d) for some aluminum alloys, together with the “maximum” pitches that permit attainment of these strengths. Joints having larger pitches fail in the spot welds rather than by tearing of the sheet, and are governed by Tables 8.2.2.3.2(b) and (c). The design shear strengths listed are also applicable to seam welds.

Open this page of MIL-HDBK-5
Table 8.2.2.3.2(a). Acceptable Aluminum and Aluminum Alloy Combination for Spot and Seam Welding
SpecificationAMS-QQ-A-250/1AMS-4029bAMS-QQ-A-250/3AMS-QQ-A-250/4bAMS-QQ-A-250/5AMS-QQ-A-250/2AMS-QQ-A-250/8AMS-QQ-A-250/11AMS-QQ-A-250/12bAMS-QQ-A-250/13c
Material1100Bare 2014Clad 2014Bare 2024Clad 2024300350526061Bare 7075Clad 7075
SpecificationMaterial
AMS-QQ-A-250/11100······························
AMS-4029Bare 2014b···***············*···
AMS-QQ-A-250/3Clad 2014···*···*············*···
AMS-QQ-A-250/4Bare 2024b···***············*···
AMS-QQ-A-250/5Clad 2024······························
AMS-QQ-A-250/23003······························
AMS-QQ-A-250/85052······························
AMS-QQ-A-250/116061······························
AMS-QQ-A-250/12Bare 7075b···***············*···
AMS-QQ-A-250/13Clad 7075b······························
a The various aluminum and aluminum-alloy materials referred to in this table may be spot-welded in any combinations except the combinations indicated by the asterisk(*) in the table. The combinations indicated by the asterisk (*) may be spot-welded only with the specific approval of the procuring or certifying agency.
b This table applies to construction of land- and carrier-based aircraft only. The welding of bare, high-strength alloys in construction of seaplanes and amphibians is prohibited unless specifically authorized by the procuring or certifying agency.
c Clad heat-treated and aged 7075 material in thicknesses less than 0.020 inch will not be welded without specific approval of the procuring or certifying agency.
Open this page of MIL-HDBK-5
Table 8.2.2.3.2(b). Spot-Weld Design Shear Strength in Thin Sheet and Foil for Bare and Clad Aluminum Alloysa,b,c (Welding Specification MIL-W-6858)
Thickness of
Thinnest Outer
Sheet, in.		Spots/inchMaterial Ultimate Tensile Strength, ksi
Standard
(Ns)d		Rangee,f56 and AboveBelow 56
Design Shear Strength, pounds per linear inch (Xm)
0.001401-502416
0.002201-304832
0.003121-178052
0.004101-1410872
0.00591-1313292
0.00671-10148100
0.00761-8168112
0.00851-7188128
a The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
b Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
c The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
d When the number of spots per inch is within 15 percent of the standard spot per inch requirement, the design shear strengths tabulated above will apply.
e When the number of spots differs from the standard spots per inch by 15 percent or greater, but does not exceed the noted range of spots per inch, applicable design strength will be determined as noted below:
Xm/Ns (K) Nr = Xr
where
Xm = design shear strength in accordance with the above table
Ns = standard spots per inch in accordance with the above table
Nr = required spots per inch (production part)
Xr = actual design shear strength requirement
K = 1.15 when number of spots per inch is reduced more than 15 percent of the standard spacing of the above table
K = 0.90 when number of spots is increased more than 15 percent of the standard spacing but within range of the tabular spacing.
f When the number of spots per inch is above the range indicated in the table, the design shear strength will remain constant at the value obtained at the top of the range.
Open this page of MIL-HDBK-5
Table 8.2.2.3.2(c). Spot-Weld Design Shear Strength in Panels for Bare and Clad Aluminum Alloysa,b,c (Welding Specification MIL-W-6858)
Design Shear Strength, pounds per spot
Material Ultimate Tensile Strength, ksi56 and
Above		35 to 5619.5 to
34.9		Below 19.5
Nominal thickness of thinner sheet, in.:
0.0104840······
0.01260522416
0.01688805640
0.018100926852
0.0201121088064
0.0221281249676
0.02514814011688
0.028172164140108
0.032208188168132
0.036244220204156
0.040276248240180
0.045324296280208
0.050372344320236
0.056444412380272
0.063536488456316
0.071660576516360
0.080820684612420
0.0901004800696476
0.1001192936752540
0.11214241072800588
0.12516961300840628
0.14020201538······
0.16024961952······
0.18029802400······
0.19032282592······
0.25058805120······
a The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
b Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
c The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
Open this page of MIL-HDBK-5
Table 8.2.2.3.2(d). Maximum Static Strength of Spot-Welded Joints in Aluminum Alloys and Corresponding Maximum Design Spot-Weld Pitcha,b
Single Row JointsMultiple Row Joints
Material7075-T6 clad2024-T3 clad6061-T67075-T6 clad2024-T3 clad6061-T6
Thickness of
Thinnest Sheet,
in.		Strength,
lbs/in.		Pitch,
in.		Strength,
lbs/in.		Pitch,
in.		Strength,
lbs/in.		Pitch,
in.		Strength,
lbs/in.		Pitch÷No.
of Rows,
in.		Strength,
lbs/in.		Pitch÷No.
of Rows, in.		Strength,
lbs/in.		Pitch÷No.
of Rows,
in.
0.0102880.1672500.1922100.1904380.1103840.1253290.122
0.0123460.1733000.2002520.2065260.1144610.1303950.132
0.0164610.1914000.2203360.2387010.1266140.1435260.152
0.0205770.1945000.2244200.2578760.1287680.1466580.164
0.0257210.2056250.2375250.26710950.1359600.1548220.170
0.0329230.2258000.2606720.28014020.14812290.16910530.179
0.04010590.2619180.3017780.31917520.15815360.18013160.188
0.05012300.30210670.3499100.37821900.17019200.19416450.209
0.06314520.36912590.42610820.45127590.19424190.22220730.235
0.07115890.41513780.47911870.48531100.21227260.24223360.247
0.08017420.47115110.54313060.52435040.23430720.26726320.260
0.09019130.52516600.60514380.55639420.25534560.29029610.270
0.10020840.57218080.65915800.59643800.27238400.31032900.284
0.11222890.62219860.71717280.62049060.29043010.33136850.291
0.12525110.67521790.78819000.68454750.31048000.35341120.316
a For multiple row joints row spacing is at minimum and same pitch in all rows.
b For pitches greater than those shown, strength is governed by Tables 8.2.2.3.2(b) and (c).
8.2.2.3.2.1Effects of Spot Welds on Parent Metal Strength of Aluminum Alloys

In applications of spot welding other than splices, where ribs, intercostals, or doublers are attached to sheet, the allowable ultimate strength of the spot-welded sheet may be determined by multiplying the ultimate tensile strength of the sheet (A or S-values) by the appropriate efficiency factor shown on Figure 8.2.2.3.2.1. Efficiencies for gages under 0.020 will be determined by test.

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.1 — Efficiency of the parent metal in tension for spot-welded aluminum alloys. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1395).

Figure 8.2.2.3.2.1. Efficiency of the parent metal in tension for spot-welded aluminum alloys.

8.2.2.3.2.2Fatigue Strength of Spot-Welded Joints in Aluminum Alloys

The fatigue strength of spot-welded joints in aluminum alloy are given in Figures 8.2.2.3.2.2(a) through 8.2.2.3.2.2(e).

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.2(a) — Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by tearing sheet). (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1396).

Figure 8.2.2.3.2.2(a). Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by tearing sheet).

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.2(b) — Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds). (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1397).

Figure 8.2.2.3.2.2(b). Fatigue strength of spot-welded joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds).

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.2(c) — Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05. (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1398).

Figure 8.2.2.3.2.2(c). Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05.

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.2(d) — Fatigue strength of spot-welded multiple row joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds). (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1399).

Figure 8.2.2.3.2.2(d). Fatigue strength of spot-welded multiple row joints in aluminum alloy sheet. Load Ratio = 0.05 (static failure by shear in the spot welds).

Open this page of MIL-HDBK-5
Figure 8.2.2.3.2.2(e) — Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05 (static failure by tear in sheets). (image from MIL-HDBK-5J)
Image reproduced from MIL-HDBK-5J (PDF page 1400).

Figure 8.2.2.3.2.2(e). Fatigue strength of triple row spot-welded lap joints in 6061-T6 aluminum alloy sheet. Load Ratio = 0.05 (static failure by tear in sheets).

8.2.2.3.3Design Shear Strengths for Spot and Seam Welds in Magnesium Alloys

Design shear-strength for spot welds in magnesium alloys are given in Table 8.2.2.3.3. The thickness ratio of the thickest sheet to the thinnest outer sheet in the combination should not exceed 4:1.

Open this page of MIL-HDBK-5
Table 8.2.2.3.3. Spot-Weld Design Shear Strength in Panels for Magnesium Alloysa,b,c (Welding Specification MIL-W-6858)
Design Shear Strength, pounds per spot
Material Ultimate Tensile Strength, ksiGreater than 19.5Less than 19.5
Nominal thickness of thinner sheet, in.:
0.0122416
0.0165640
0.0186852
0.0208064
0.0229676
0.02511688
0.028140108
0.032168132
0.036204156
0.040240180
0.045280208
0.050320236
0.056380272
0.063456316
0.071516360
0.080612420
0.090696476
0.100752540
0.112800588
0.125840628
a Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
b The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
c Magnesium alloys AZ31B and HK31A may be spot-welded in any combination.
8.2.2.3.4Design Shear Strengths for Spot and Seam Welds in Titanium and Titanium Alloys

Design shear strength for spot welds in titanium and titanium alloys are given in Tables 8.2.2.3.4(a) and (b). The thickness ratio of the thickest sheet to the thinnest outer sheet in the combination should not exceed 4:1.

where one material bends away from another. Edge distances less than those specified above may be used provided there is no expulsion of weld material or bulging of the edge of the sheet; however, these joints may have less static strength and shorter fatigue life.

d Minimum contacting overlap is twice the minimum edge distance.

e Less than minimum recommended spacing may cause shunting that leads to deterioration of weld strengths and joint life.

Open this page of MIL-HDBK-5
Table 8.2.2.3.4(a). Spot-Weld Design Shear Strength in Thin Sheet and Foils for Titanium and Titanium Alloysa,b,c (Welding Specification MIL-W-6858)
Thickness of
Thinnest Outer
Sheet, in.		Spots/inchMaterial Ultimate Tensile Strength, ksi
Standard
(Ns)d		Rangee,fAbove 185150 to 18590 to 149Below 90
Design Shear Strength, pounds per linear inch (Xm)
0.001401-5072645236
0.002201-3014412810472
0.003121-17240208164120
0.004101-14324280228152
0.00591-13392340272188
0.00671-10432380304220
0.00761-8504440352256
0.00851-7552488392284
a The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
b Strength based on 80 percent of minimum values specified in Specification MIL-W-6858.
c The allowable tensile strength of spot-welds is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
d When the number of spots per inch is within 15 percent of the standard spot per inch requirement, the design shear strengths tabulated above will apply.
e When the number of spots differs from the standard spots per inch by 15 percent or greater, but does not exceed the noted range of spots per inch, applicable design strength will be determined as noted below:
Xm/Ns (K) Nr = Xr
where
Xm = design shear strength in accordance with the above table
Ns = standard spots per inch in accordance with the above table
Nr = required spots per inch (production part)
Xr = actual design shear strength requirement
K = 1.15 when number of spots per inch is reduced more than 15 percent of the standard spacing of the above table
K = 0.90 when number of spots is increased more than 15 percent of the standard spacing but within range of the tabular spacing.
f When the number of spots per inch is above the range indicated in the table, the design shear strength will remain constant at the value obtained at the top of the range.
Open this page of MIL-HDBK-5
Table 8.2.2.3.4(b). Spot-Weld Design Shear Strength in Panels for Titanium and Titanium Alloya,b,c (Welding Specification MIL-W-6858)
Design Shear Strength, pounds per spot
Material Ultimate Tensile Strength, ksiAbove 100100 and Below
Nominal thickness of thinner sheet, in.:
0.010164128
0.012220160
0.016320236
0.018392272
0.020424312
0.022488360
0.025580424
0.028684508
0.032836620
0.0361004736
0.0401168852
0.04514381028
0.05017021204
0.05620401416
0.06324001688
0.07127021914
0.08030482160
0.09034302435
0.10038102702
0.11242603030
0.12547603380
a The reduction in strength of spot-welds due to the cumulative effects of time-temperature-stress factors is not greater than the reduction in strength of the parent metal.
b Strength based on 80 percent of minimum value specified in Specification MIL-W-6858.
c The allowable tensile strength of spot-wells is 25 percent of the design shear strength. Higher values may be used, however, if these are substantiated by tests acceptable to the procuring or certifying agency.
8.2.3Brazing
8.2.3.1Copper Brazing

The allowable shear strength for copper brazing of steel alloys will be 15 ksi, for all conditions of heat treatment. Higher values may be allowed upon approval of the procuring or certifying agency.

The effect of the brazing process on the strength of the parent or base metal of steel alloys will be considered in the structural design. Where copper furnace brazing is employed, the calculated allowable strength of the base metal which is subjected to the temperatures of the brazing process will be in accordance with the following:

MaterialAllowable Strength
Heat-treated material (including normalized) used in “as-brazed” conditionMechanical properties of normalized material
Heat-treated material (including normalized) reheat-treated during or after brazingMechanical properties corresponding to heat treatment performed
8.2.3.2Silver Brazing

Silver-brazed areas should not be subjected to temperatures exceeding 900°F. Silver brazing alloys are listed in specification QQ-B-654. Deviation from this specification may be allowed upon approval of the procuring or certifying agency.

The allowable shear strength for silver brazing of steel alloys will be 15 ksi, provided that clearances or gaps between parts to be brazed do not exceed 0.010 in. Deviation from this specified allowable value may be allowed upon approval of the procuring or certifying agency.

The effect of silver brazing on the strength of the parent or base metal is the same as shown for copper brazing in Section 8.2.3.1.

Chapter 1 (General) Chapter 2 (Steel) Chapter 3 (Aluminum) Chapter 4 (Magnesium) Chapter 5 (Titanium) Chapter 6 (Heat-Resistant Alloys) Chapter 8 (Structural Joints) Chapter 7 (Miscellaneous Alloys)

Cite This Work