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Great Designs in Steel is Sponsored by:

ArcelorMittal Dofasco, ArcelorMittal USA, Nucor Corporation,

Severstal North America, Inc. and United States Steel Corporation

A Comparative Study of Joint Efficiency for

Advanced High Strength Steel


John Bohr

A/SP Joining Technologies Team

Project Description

• Conduct a study on various grades of steel to quantify joint efficiencies of assorted joining and bonding methods.

• Methodology for this project was to produce typical welds/joints/bonds on lap-shear and/or coach peel coupons to generate tensile test (load-displacement)


coupons to generate tensile test (load-displacement) curves for the varied process and material configurations.

• Project deliverables include the load displacement curve and calculations of joint efficiency, stiffness, and energy for each test configuration.

Joint Efficiency1

A numerical value expressed as the ratio of the strength of a

riveted, welded, or brazed joint to the strength of the parent

metal. In welding, the ratio of the strength of a joint to the

strength of the base metal, expressed in percent.


strength of the base metal, expressed in percent.

(Coupon dimensions for tensile testing used in this study were derived from the AWS/ANSI D8 Automotive

Welding Standards.)

1 Definition from http://www.answers.com

Joint Efficiency Calculation Example25mm LASER Fillet Weld

Joint Strength = 4997 N

Parent Metal Strength = 8776 N


joint efficiency η = joint strength / parent strength

joint efficiency η = 4997 / 8776

joint efficiency η = 57%

Joint Strength Metrics

Stiffness = Slope of the best fit

line in the elastic region


Material Compositions – Phase I

Steel C Mn P S Si Cu Ni Cr Al Mo V Nb Ti N

Mild 0.07 0.049 0.006 0.0037 0.006 0.015 0.006 0.025 0.051 0.005 0.004 0.001 0.053 0.0044

590R 0.136 1.588 0.011 0.0066 0.115 0.024 0.01 0.031 0.033 0.013 0.002 0.041 0.002 0.0068

Chemical Compositions of Tested Steels (wt%)

•0.7mm Mild EG

•1.2 mm 590R GA

•1.2 mm DP600 GI

•1.15 mm DP780 GA

•1.0 mm Trip800 EG


Steel Location Al(wt%) Fe(wt%) Coating Weight (g/m2) Ave. Al (wt%) Ave. Fe (wt%) Ave. Coating Weight (g/m2)

Mild Top 0.005 0.032 67.0

Bottom 0.005 0.040 66.2

590R Top 0.322 11.500 49.5

Bottom 0.330 11.500 49.0

DP600 Top 0.262 0.921 63.4

Bottom 0.263 0.728 65.4

DP780 Top 0.220 8.890 57.6

Bottom 0.249 9.410 47.5

TRIP800 Top 0.005 0.056 54.8

Bottom 0.004 0.054 59.60.005

0.235

0.263

0.326

64.4

52.5

57.2

0.036

11.500

0.825

9.150

0.055

Coating Analysis of Tested Steels

66.6

49.3

0.005

590R 0.136 1.588 0.011 0.0066 0.115 0.024 0.01 0.031 0.033 0.013 0.002 0.041 0.002 0.0068

DP600 0.101 1.857 0.011 0.0038 0.361 0.034 0.008 0.024 0.053 0.014 0.003 0.004 0.003 0.0118

DP780 0.114 2.09 0.017 0.0028 0.034 0.034 0.013 0.234 0.056 0.184 0.005 0.004 0.002 0.0091

TRIP800 0.194 1.677 0.014 0.002 1.659 0.033 0.016 0.026 0.042 0.013 0.004 0.005 0.004 0.0062

Processes


Methodology

• Five samples were prepared for each welding / joining process.

(45 mm x 105 mm coupons)

• Process setup verifications* were performed prior to tensile

samples being produced in order to ensure quality joints.

• GMAW and LASER welds were cross-sectioned and analyzed

to verify conformance with requirements.


to verify conformance with requirements.

• For each process, two specimens were tensile tested. If peak

loads were within 5%, the data from the specimen with the

lowest peak load was used.

• If peak loads were greater than 5%, a third specimen was tested,

the data from the specimen with the median peak load was used.

*Note: Except for the A/SP Starting Weld Schedules

MethodologySchematics for Test Specimens


Mild Steel - Sample Results

YMMV


YMMV

0.7 EG - Population Results


Sample Load/Displacement Curves for 0.7 mm


0.7mm Mild ResultsMild

Joining Process Energy (J) Joint Efficiency Peak Load (N) Stiffness (N/mm)

Parent Metal UTS (45X105) 151.90 100% 8776.0 45222.7

Arc Braze - Double fillet in a slot (13X25) 122.48 93% 8143.3 19675.2

GMAW Double fillet weld in a slot (13X25) 103.30 90% 7870.6 24766.5

Arc Braze - Single fillet weld in a slot (10X25) 61.72 82% 7222.8 22642.5

Arc Braze (25mm lap fillet) 37.79 76% 6678.3 32536.9

GMAW (AWS D8.8M) 33.94 74% 6488.4 27084.1

GMAW (manual - Operator A) 28.86 73% 6442.0 29041.6

GMAW (Optimized geometry) 26.41 73% 6379.1 24311.7

GMAW (OTC DL) 24.29 72% 6287.7 21192.6

GMAW (OTC DP-400) 23.81 70% 6182.9 23199.5

Laser (staple geometry) 33.01 70% 6172.6 22108.4

GMAW Lincoln STT 21.16 69% 6065.9 26812.3

Lincoln Power Mode 18.14 68% 5943.3 23394.7

GMAW (manual - Operator B) 20.07 67% 5904.7 25540.5

GMAW single fillet weld in a slot (10X25) 22.10 67% 5849.2 25629.1



GMA Cold Metal Transfer (Fronius) 15.46 63% 5529.7 29138.9

Laser (25mm lap) 17.35 62% 5400.4 21483.0

Arc Braze - Plug Weld (8mm hole) 29.35 61% 5386.6 21505.4

Laser MIG (25mm lap fillet) 10.90 61% 5375.6 24866.5


Laser (25mm lap fillet) 11.10 57% 4997.2 22916.4

GMAW - Plug Weld (10mm hole) 18.60 56% 4881.8 18099.1

Laser Braze (25mm lap fillet) 4.25 49% 4320.0 22892.7


Resistance Spot Welding (ProSpot i4) 6.75 39% 3384.3 14138.9

GMAW - Arc Spot 5.54 38% 3337.6 16535.4

Fronius Delta Spot 4.49 37% 3268.3 20558.5

A/SP RSW Starting Schedule (DC) 5.73 36% 3193.7 17480.0

Resistance Spot Welding (AWS D8.1M) 4.55 34% 2996.4 16386.0

A/SP RSW Starting Schedule (AC) 3.23 29% 2581.3 16091.2

Hemlok Rivet 1/4" 15.97 27% 2346.2 4170.5

Self Pierce Rivet (Henrob) 4.56 26% 2291.5 10889.8

Mechanical Clinch Tog-L-Loc (BTM) 1.72 26% 2272.4 15710.9

590R - Sample Results

YMMV


YMMV

1.2mm 590R


1.2mm 590R Results590R







GMAW (OTC DL) 19.11 67% 20119.7 38983.8

Laser (25mm lap) 30.51 67% 20195.9 35723.1

GMAW Lincoln STT 26.46 66% 19808.4 37260.8

GMAW (Lincoln Rapid Arc) 15.49 66% 19873.3 35359.8



GMAW Lincoln Powermode 23.70 65% 19559.7 36065.2






GMAW (OTC DP-400) 17.28 61% 18455.9 39788.1

GMAW (AWS D8.8M) 15.63 60% 18120.3 38962.9













Hemlok Rivet 1/4" 22.39 29% 8820.7 27237.9



GMAW - Arc Spot 1.94 22% 6627.4 29388.4

DP600 - Sample Results

YMMV


YMMV

1.2mm DP600


1.2mm DP600 ResultsDP600





SPR/Adhesive (Rivbond Henkel 5087) 14.63 66% 21330.8 47963.7

Laser (25mm lap) 38.68 63% 20503.1 35155.6


GMAW Lincoln Power Mode 26.71 62% 20072.9 36898.0


GMAW (OTC DL) 20.59 59% 19133.1 37736.7


GMAW (OTC DP-400) 16.24 58% 18885.0 39229.8



GMAW (AWS D8.8M) 12.85 56% 18276.2 37494.2














GMAW Lincoln STT 3.11 37% 12125.5 38448.7

GMAW - Arc Spot 5.21 35% 11279.5 32101.7




Hemlok Rivet 1/4" 22.97 28% 8987.9 25990.6



TRIP800 - Sample Results

YMMV


YMMV

1.0mm TRIP800


1.0mm TRIP800 ResultsTRIP800





GMAW (OTC DL) 19.57 66% 23561.4 34599.4


GMAW (AWS D8.8M) 20.11 63% 22373.9 34302.4



Laser (25mm lap) 22.69 62% 21978.5 31916.5

GMAW (OTC DP-400) 15.10 61% 21957.5 34744.1

GMAW Lincoln GMAW Powermode 17.42 60% 21593.9 32191.8


GMAW Lincoln STT 12.17 58% 20764.1 33297.0



















GMAW - Arc Spot 5.02 28% 9959.8 26786.2

Hemlok Rivet 1/4" 14.27 23% 8248.3 29282.6



DP780 - Sample Results

YMMV


YMMV

1.15mm DP780


1.15mm DP780 ResultsDP780




GMAW Double fillet weld in a slot (13 x 25) 24.75 61% 27121.2 37375.6

GMAW Lincoln Powermode 25.37 58% 25461.4 36749.7

GMAW (OTC DL) 18.19 54% 23799.8 38030.1


Laser (25mm lap) 21.56 52% 22768.6 34096.6



GMAW single fillet weld in a slot (10x25) 12.87 49% 21548.1 38417.8

GMAW (AWS D8.8M) 11.79 49% 21752.3 37141.1











GMAW (OTC DP-400) 7.10 38% 16584.1 38241.1




GMAW Lincoln STT 6.19 36% 16112.2 37671.9





Structural Adhesive (Henkel 5087) 3.93 28% 12582.1 36984.2


Hemlok Rivet 1/4" 14.40 20% 9030.0 27964.6


GMAW - Arc Spot 3.15 19% 8610.4 31873.6


Joint Efficiency

Process Comparisons


Spot Weld and Rivet Comparison


Spot Weld and ProSpot Comparison


General Observations


Observations

• AHSS can be successfully welded/joined/bonded by many processes

• Various joining processes result in different strength metrics.


strength metrics.

• Joints with similar tensile peak loads can have different Energy (J) values.

• Joints with similar Energy (J) values can have different tensile peak loads.

Observations

• GMAW and LASER processes with steel filler

have higher joint efficiency in AHSS material

than Arc Braze or LASER Braze

• RSW and SPR in combination with structural


• RSW and SPR in combination with structural

adhesive produced specimens with the highest

joint efficiencies.

• The joint efficiency trend line generally

decreases as material strength increases.

Acknowledgements


Additional Information – Phase I


What’s Next


Phase I - Learnings

• Include HSLA and Martensitic materials for

additional Joint Efficiency and strength

calculations in Phase II

• Reduce coupon overlap to 15mm

• Expand the conditions studied to include a


• Expand the conditions studied to include a

15mm, 20mm and 25mm lengths for

continuous joining processes

• Include fatigue samples

• Include coach peel tests

FOR MORE INFORMATION

• CONTACT: John Bohr, ASP070 Co-Chair

810-602-8276

[email protected]

Ted Coon, ASP070 Co-Chair

313-594-2849

[email protected]

Cindy Jiang, Principal Consultant

248-668-3891

[email protected]


[email protected]

Mike Bzdok, ASP070 Project Manager

248-945-4778

[email protected]

"This material is based upon work supported by the Department of Energy National Energy Technology Laboratory under Award Number DE-FC26-

02OR22910.

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any

agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy,

completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned

rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily

constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of

authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof."

Questions and Answers




Great Designs in Steel is Sponsored by:

ArcelorMittal Dofasco, ArcelorMittal USA, Nucor Corporation,

Severstal North America, Inc. and United States Steel Corporation

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