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High Power Laser Welding of Thick Construction Steels

Hans Engström, Jan Flinkfeldt, Klas Nilsson Luleå University of Technology

Tony Nilsson, SSAB Tunnplåt AB Anders Skirfors, SSAB Oxelösund AB

Marcus Miller, Volvo Articulated Haulers AB

(2)

Presentation

• Introduction

• Experimental

• Results

– Allowed gap width

– Weld geometry, microstructure – Strength

– Design opportunities

• Conclusion

(3)

Introduction

Benefits of Laser Welding

• High Welding Speed

• Small Distortions

• New Design Opportunities

(4)

Laser equipment used

Laser I II III

Power [kW] 6 12 17

Focal length [mm] 275 270 300

Beam focal diameter [µm]

500 500 800

Shielding gas supply

He, Coaxial nozzle, ø6 mm

He, He/CO

2

, He/Ar Coaxial nozzle, 4xø1,2 mm

He, He/O

2

Open + lateral supply nozzle

(5)

Materials

Steel grade C Si Mn P S N Al Nb Ti V CE

1)

Domex 280 YP, 8 mm, (040XLK)

0,06 0,22 0,36 0,006 0,010 0,005 0,047 - - 0,008 0,13 Domex 420 YP, 8 mm,

(060XLK)

0,06 0,01 0,60 0,009 0,006 0,006 0,048 0,050 - 0,005 0,17 Domex 700 MC, 6 mm,

(100XF)

0,07 0,27 1,63 0,010 0,002 0,007 0,034 0,061 0,113 0,015 0,37

Steel grade Yield strength Re (MPa)

Tensile strength R m

(MPa)

Elongation A 5

(%)

Charpy V-notch toughness Joule/cm

2

/ °C Domex 280 YP, 8 mm,

(040XLK)

280 389 40 -

Domex 420 YP, 8 mm, (060XLK)

455 536 28 348 / -20

Domex 700 MC, 6 mm, (100XF) 721

1)

799

1)

25

1)

127 / -40

Carbon equivalent CE(%) = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15

(6)

Materials

High Strength Cold Forming Steel - Domex High Strength Structural Steel - Weldox

Wear Resistant Steel - Hardox

(7)

Materials cont.

Material t mm

C Si Mn P S Cr Ni Mo V Ti Cu Al Nb B CE

I

W 1

WELDOX 500 (A678D)

6 ,087 0,24 1,49 ,008 ,002 ,028 ,057 ,015 ,083 ,009 ,030 ,030 ,038 0 0,37

HARDOX 400 10 ,127 0,46 1,37 ,008 ,002 ,029 ,038 ,008 ,009 ,032 ,010 ,044 ,023 ,002 0,37 HARDOX 400 15 ,135 0,44 1,39 ,009 ,001 ,022 ,043 ,011 ,008 ,031 ,019 ,028 ,024 ,002 0,38

Material t

(mm)

Delivery condition

Re (MPa)

Rm (MPa)

A5 (%)

CVL Hardness (HB)

WELDOX 500 6 M 536 600 24 174J/-50°C

1

-

HARDOX 400 10 Q - - - 30J/-40°C

1,2

408

HARDOX 400 15 Q - - - 50J/-40°C

2

400

1

(8)

Welding Parameters

Material t (mm) P (kW) v (m/min) Q (kJ/mm)

1

∆t8/5 (s)

2

WELDOX 500 6 5,0 2,4 0,12 1

WELDOX 500 6 5,0 1,2 0,25 2

WELDOX 500 6 3,0 0,4 0,45 5

HARDOX 400 10 10,5 2,4 0,26 1

HARDOX 400 10 10,5 1,7 0,37 2

HARDOX 400 10 10,5 1,0 0,63 5

HARDOX 400 15 17,0 1,1 0,93 5

(9)

Joint Preparation

Laser cut edge

Oxide free surface 8 mm

Laser beam

• Butt joints (laser cut, machined, V-shaped machined edges)

• Corner joints

(10)

Gap width Plate thickness 8 mm z z

z z z z

z z

0 1 2 3 4 5 6 7 8 9 10

0 0,1 0,2 0,3 0,4 0,5

Joint t h ickness[mm] [mm]

Joint width before welding [mm]

Gap width (mm) 0.0 0.1 0.2 0.3 0.4 0.5

(11)

Weld geometry

Domex 280 YP 8 mm

Domex 420 YP 8 mm

Domex 700 MC

6 mm

(12)

Domex 420 YP

0 100 200 300 400

3 4 5 6 7 8 9 10 11 Distance, mm

HV5 Domex 700 MC

0 100 200 300 400

3 4 5 6 7 8 9 10 11 Distance, mm

HV5

Domex 280 YP

0 100 200 300 400

2 3 4 5 6 7 8 9 10 Distance, mm

HV5

Hardness

(13)

Domex

Strength, ductility

Steel grade Welding speed (m/min)

Yield strength

R

e

(Mpa)

Tensile strength

R

m

(MPa)

Elongation A

5

(%)

Fracture position

Charpy V toughness, L

2)

Joule/cm

2

/ °C Domex 280YP,

8mm, (040XLK)

0,90 295 403 29 BM

1)

Domex 420YP, 8mm, (060XLK)

0,60 0,80

448 448

544 539

24 23

BM

BM 117(A

3)

),302(C

3)

) /-40 Domex700MC,

6mm, (100XF)

1,20 738 813 19 BM 223(A

3)

),105(C

3)

) /-40

1) BM = Base material

2) Longitudinal to welding direction

(14)

WELDOX 500

Weld Geometry, Hardness

∆t8/5=1 s ∆t8/5=2s ∆t8/5=5s

t=6 mm

(15)

WELDOX 500

Structure constituents in weld joint and HAZ

∆t8/5 (s) % Ferrite % Perlite % Martensite % Bainite HAZ

1 - - 81 19 Martensite/

Bainite

2 - - 65 35 Martensite/

Bainite 5 15 Polygonal ferrite

75 Acicular ferrite

- - 10 Bainite

Base Material

85 Polygonal ferrite 15 - -

∆t8/5= 1s ∆t8/5=2s ∆t8/5=5s

(16)

WELDOX 500/HARDOX 400 Strength/Impact toughness

Material t (mm)

∆t8/5 (s)

Re (MPa)

Rm (MPa)

A50 (%)

Fracture position

Impact toughness at –40 °C (J) Specimen size: 5x10 mm

WM/HAZ

WELDOX 500 6 1 - 585 36 BM 54/48

WELDOX 500 6 2 - 590 36 BM 68/37

WELDOX 500 6 5 - 581 28

1

BM 63/64

HARDOX 400 10 1 1114 1230 7 HAZ 23/8

HARDOX 400 10 2 1108 1213 6 HAZ 30/15

HARDOX 400 10 5 1032 1058 4 HAZ 20/22

HARDOX 400 15 5 1011 1108 8 HAZ 30/27

2

(17)

HARDOX 400 Weld Geometry

∆t8/5=1s ∆t8/5=2s ∆t8/5=5s

∆t8/5=5s

t=10 mm

(18)

HARDOX 400

Hardness

(19)

Box Beam of Traditional Design

(20)

Box Beam of New Design

Domex 355

t= 8,10 mm

(21)

Fatiguebending for B1-beams.

10 100 1 000

B e n d ingst ress [ M pa]

Domex, tvärskarvar, R= -1 Domex, R= 0

Weldox, R= 0 Domex, R= -1 (1995) 180; 2E6; k1=3 120; 2E6; k1=3 Laserbalkar

Fatigue bending strength

(22)

Conclusions

• Excellent welding results for high strength cold forming, structural and wear resistant steels

– high strength – high toughness – good formability

• Fatigue bending properties equal or better

than MAG welded beams

References

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