Volvo Profile colors WELDING STANDARDS AND … Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 3 2016-09-29 • Differentiate welds with good properties from welds

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WELDING STANDARDS AND REQUIREMENTS FOR THE FUTURE Erik Åstrand Dr, IWE Manufacturing Development Volvo CE, Braås

Introduction

3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE

•  Volvo CE 2005

•  IWE 2008

•  PhD 2016

2016-09-29 2

Erik Åstrand

Volvo CE, Braås

[email protected]

•  Give a predictable output to be used in design for weight optimization

•  Prohibit over-processing due to unnecessary requirements to avoid high welding cost

•  Support a development of welding procedures for reduced cost, reduced variation and improved strength

Requirements for a good welding standard

3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 2016-09-29 3

•  Differentiate welds with good properties from welds with bad properties

Requirements for a good welding standard


Welding standards


•  Traditional welding standards –  Based on a good workmanship weld

à DIN 8563, ISO 5817, Volvo group STD 181-0001 etc

2016-09-29 5

1. ”A Good Workmanship

Weld”

2. Welding standard

requirements

3. Development

of welding procedures

•  Discontinuities based on characteristics that easily can be evaluated with visual inspection

•  Low correlation to the fatigue properties of the weld

•  Prohibit development of improved welding procedures

Welding standards


•  Fatigue life based welding standards –  Based on the expected fatigue life

à Volvo Group STD 181-0004

1. Fatigue life req.

2. New standard

requirements

3. New welding

procedures

4. New weld types

•  Gives predictable fatigue properties with clear steps in strength between weld quality levels

•  Include important requirements such as weld penetration and weld toe radius as well as traditional requirements.

•  Development of NDT techniques

•  Development of welding procedures to improve the penetration and radius

•  This development gives a need for a new standard update

”A good Weld is any weld which do the job is intended for during the entire life of the structure”

AM Gresnight

What is a good weld?


?

What is a high quality weld?

Good welding requirements must differen7ate the high-‐quality weld from the low quality weld

Long fa(gue life Short fa(gue life

High quality Low quality

2016-09-29 3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 8

Critical requirements


Critical Requirement

Less Critical Requirement

Most standards requirements of a single weld have a low or limited influence of the fa7gue strength

à Possibili7es to remove or loosen many requirements

Welding procedures - In theory it is simple

• Welds with a cri(cal weld toe should have a low stress concentra(on without defects

• Welds with a cri(cal root should have large penetra(on that minimises the root crack.

• However, these demands are in contradic(on to each other..

10 2016-09-29


The contradic7on of high quality

•  If we want really good proper(es in one point it is essen(al to have lower requirements in other areas to get the right focus

•  It is necessary to priori(ze or use more than one weld run

Low quality

Very high quality

Very low quality

Very high quality


11 2016-09-29

Improved welding procedures - In theory it is simple

• Welds with a cri(cal weld toe should have a low stress concentra(on without defects

• Welds with a cri(cal root should have large penetra(on that minimises the root crack.

• However, these demands are in contradic(on to each other..

12 2016-09-29


Welds with a cri7cal root

A change torch posi*on makes it possible to get an improved penetra(on

Throat thickness 5 mm

i 2-‐3 mm

Leg length 5/8 mm i 3,5-‐4,5 mm

+100% in Fa7gue life


13 2016-09-29

Aim at the point you want to reach!

14

2-3 mm 3.5-4.5 mm < 2 mm

à Gives welds with leg deviations à Leg deviations gives improved increased penetration à Specify welds with leg deviations

2016-09-29 3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE

Strength comparison -199 samples

Req

uire

men

t

Type

mea

n th

roat

thic

knes

s,

a mea

n pe

netr

atio

n, i

Eq. T

hroa

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ex -B

ox

beam

s (K

.-E. O

lsso

n et

al

., 19

97; S

amue

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2008

)

Eq. t

hroa

t ind

ex -

Load

ca

rryi

ng c

ruci

form

jo

int (

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ori,

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)

Stre

ss c

once

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inde

x Lo

ad c

arry

ing

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iform

join

t (Fr

ank

and

Fish

er, 1

979)

Stre

ss c

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BS7

910

D Leg 3,8 4 131 151 39 39

F Leg 4,3 3,6 128 138 51 51

G Leg 4,4 3,5 127 136 54 54

E Leg 4,5 3,4 126 133 57 57

A Throat 5,3 2,9 123 122 67 68

B Throat 5,1 2,9 121 118 69 70

C Throat 4,8 2,9 118 113 72 72

i2a5 Throat 5 2 100 100 100 100


- Same rank with all formulas - Leg length requirements gives better properties than throat thickness requirements

x2

Grinding

Controlled undercut prescribed

High Frequency Impact Treatment, HFMI

Controlled undercut prescribed

As welded

No undercut wanted

Critical weld toe - Wanted geometry from different processes

16

Hypothesis: Welds with a smooth undercut in “as welded” condi7on will offer

enhanced fa7gue proper7es

Weld

Base plate Base plate

Weld Weld

Base plate

2016-09-29 3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE

Fatigue testing

3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 17 2016-09-29

•  The samples has similar fatigue properties as HFMI treated welds

•  Low scatter

Toolbox for lean welding

Weld toe radius

Weld speed

Weld penetra7on

Good workmanship Optimized

penetration

Optimized Weld toe

Low Cost

Focus

Potential

+100% in fatigue life

+ 33% in productivity


18 2016-09-29

Changes for the future


•  Replace throat thickness with leg length and leg deviation requirements

•  Specify smooth undercuts for welds with a critical weld toe –  Eliminate the risk of coldlaps

•  Remove or loosen non critical requirements –  Especially the ones that are hard

to fulfil or evaluate

2016-09-29 19

Future welding standards


•  Choose weld class in relation to critical root side or toe side –  It should be clear to the welder what is

critical

•  Root side class –  No radius requirement –  Penetration depth specified –  Possibilities to use leg length req. –  Also usage for low cost welds

•  Toe side class –  Radius req. specified for the critical weld

toe.

2016-09-29 20

Increased utilisation of the welding process

- Enable usage of improved welding procedures

Improved predictability enable reduced safety margins

Reduced cost by reduction of unnecessary requirements

More clear what to put efforts in production and quality assurance

à Reduced weight and reduced fabrication cost

Potential effect of new welding standard requirements


2016-09-29 3rd Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 22

THANKS FOR THE ATTENTION!

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Volvo Profile colors WELDING STANDARDS AND … Nordic Conference of lightweight structures - Erik Åstrand Volvo CE 3 2016-09-29 • Differentiate welds with good properties from welds