Fillet Welding

7/14/2019 Fillet Welding

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FILLET WELDING

Rhishikesh Kulkarni

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OBJECTIVES

• Understanding Importance of Fillet , Its

Aesthetics and Cost.

• To Create consumable wastage awareness due to

excessive fillet sizes.

• Understanding & Control of fillet size variations

in various positions.






CONTENTS

A. INTRODUCTION TO FILLET

B.FILLET NOMENCLATURE

C.FILLET WELD DESIGN - BASICS

D.FILLETS USED TO MAKE FIVE BASIC JOINTS

E. FAULTY WELD FILLET SIZES & PROFILES

F. FILLET WELDING TECHNIQUES

G. VARIOUS FILLET PROFILES & WELDING SYMBLOLS

H. TEST PAPER






A. INTRODUCTION TO FILLET

Symbol Of Fillet weld

Definition : “ Weld of Approximately triangular cross

section joining two surfaces nearly at right angles to

each other.”

• Fillet welds are used to join corner, T and Lap joints .

• Fillet Joints are economical and requires no edge

preparation.






B. FILLET WELD NOMENCLATURE






B. FILLET WELD NOMENCLATURE ( Contd..)

• Base Metal : Metal to be welded.

• Bond L ine : Junction of Weld Metal and Base Metal.

• Depth o f Fusion : Distance that fusion extends into base metal.

• Face of Weld : Exposed surface of weld on the side from which the

welding was done.• Leg o f a Fil let weld : Distance from a root of a joint to the toe of

the fillet weld.

• Root o f Weld : Point at which the bottom of the weld intersects the

base metal surface.

• Throat of Fi l let weld : Shortest distance from the root of the filletweld to its face.

• Toe of a weld : Junction between the face of the weld and the base

metal.






C. FILLET WELD DESIGN - BASICS

• Fillet welds are least expensive than groove weld as edgepreparation cost is less.

• Fillet welds are expected to have equal leg lengths i.e

ideally face of the fillet should be at 45 degrees angle.

• In normal type of fillets , strength of fillet depends on

throat Size.

•Throat Size = 0.707 x leg length.






C. FILLET WELD DESIGN - BASICS

• Doubling the Fillet Size ( Leg length ) doubles the throatdimensions also doubles the strength of the fillet . But itincreases the cross sectional area weight by four times .

• Single fillet welds are extremely prone to cracking , root of weld is subjected to cracking specifically for T, corner &

Lap joints.

•Remedy for this is to make double fillets which prohibitsthe tensile load from being applied to the root of the fillet.

•Please refer the F ( FORCE) arrowhead in Figure 19.25.(Fillet used to make five basic joints)






C. FILLET WELD DESIGN - BASICS ( contd…)

Diagram A Shows Leg Length = 10 mm

Diagram B shows leg length = 20 mm.

Area of Fillet A = 50 mm2

Area of Fillet B = 200 mm2

Suppose welding to be carried out on 1 meter Length.

I.e Welding Length ( L) = 1000 mm

10

10

20

20

A B






C. FILLET WELD DESIGN - BASICS ( contd…)

Welding Volume =

Fillet A = 50 Cm3

Fillet B = 200 Cm3

Weld Deposit =

Fillet A = 390 gms.

Fillet B = 1560 gms.

Thus,

Doubling the Fillet Size ( Leg length ) doubles the throat dimensionsBut increases the cross sectional area weight and electrode

Consumption by four times .






D. FILLETS USED TO MAKE FIVE BASIC JOINTS






E. FAULTY FILLET WELD SIZES & PROFILE

• Faulty weld sizes refers to undersize weld or variable leg lengths thanrequired. Faulty profiles refers to excessive concavity, excessive

convexity, unequal leg lengths & irregular weld face.






E.FAULTY FILLET WELD SIZES & PROFILE ( Contd…)

1. Excessive Convexity







1. Excessive Convexity :

It is the weld metal lying outside the plane joining the weld toes.

Normally Called as ”Reinforcement.”

Causes:

A.Deposition of excess volume

of a cold metal.

B.Use of Incorrect ( Low)welding current.

C.Improper welding technique.

NOTE : Excessive Convexi ty is

also asso ciated with o ver lappin g

toes of the weld giv in g r ise to

notc h ef fect & s tress

Concentrat ion af fect ing fat igue

l i fe of a component ser iously .







1. Excessive Convexity ( Contd..):Acceptance:

As per AWS D 1.1 limits for this imperfection relate the height of the

excess metal to the width of bead with maximum values ranging from

3 mm for a stringent quality and 5 mm for a moderate quality levels.

5 mmW>= 25 mm

3 mmW < 8 to W <25 mm

2 mmW <= 8 mm

Maximum ConvexityWidth of weld Face







2. Excessive Concavity







2. Excessive Concavity ( Contd…)

“ It’s the failure to achieve the size requirements Upto the plane joining

weld toes.”

Causes:

A. Use of incorrect ( High) welding current.

B. Improper welding Technique.

NOTE : Excessive conc avi ty reduce the throat thickness o f f i l let weld

and also reduce the ul t imate st rength of the welded joint .

Excessive conc avi ty in f i l let welds can be rect i f ied b y adding

fur ther weld m etal .







3. Oversize Fillet Welds(Welds with throat larger than required by design)

Causes :A.High welding currents.

B.Slow travel speed.

C.Improper welding technique.

D.Improper supervision.







3. Oversize Fillet Welds ( Contd…)(Welds with throat larger than required by design)

Acceptance:

Throat thickness greater than the required one may notbe a reason for rejection.

Generally for stringent quality levels the actual throat (a) may

exceed the nominal design throat (h) by 1+0.15a ( refer previous Dig.).

With this rule maximum 3 mm for stringent levels & 5 mm for moderate

Quality levels is recommended.

Avoidance : Adhere to specified welding parameters.

Do not add welding to specified weld size.







4. Undersize Fillet Welds ( Contd…)(Welds with throat smaller than required by design)

Causes:

A. Low welding currents.

B. High welding speeds.







4. Undersize Fillet Welds ( Contd…)

(Welds with throat smaller than required by design)Acceptance:

Fillet weld with throat thickness smaller than prescribed should not

be treated imperfect if actual throat thickness is having greater depth

of penetration which complies with nominal throat value.

( Please refer pervious diagram).But penetration is weld characteristic which is difficult to measure ,

Hence this should be discussed with the designer.

Stringent control over both welding process and welder are required.

Avoidance:

A. Adhere to specified welding procedure and parameters.

B. Use sufficient current & appropriate travel speed.







5. Asymmetric Fillet Welds(Fillet Welds with unequal leg lengths)

Causes:A. Due to incorrect electrode

Positioning or due to gravity

pulling the molten pool

towards one face of the joint.

B. Problem specially lies with

fillet welds in Horizontal andVertical position.







5. Asymmetric Fillet Welds ( Contd..)(Fillet Welds with unequal leg lengths)

Acceptance:

Acceptance is related to throat thickness.

E.g. For a 10 mm leg length fillet( 7.1 mm Throat) allows a difference inleg lengths of about 2.5 mm at stringent quality levels & 3.4 mm at

moderate quality levels.

But these imperfections give significant increase in weld volume and

consumable deposition.

Unequal leg lengths reduces the throat thickness & thus

ultimate strength of weld also reduces.







1. Flat Position ( 1F)







1. Flat Position ( 1F) (Contd..)

Procedure:

A.First pass to be deposited with minimum weaving.

B.The arc should be concentrated at the root as Shown in the figure

to ensure good fusion.

C.Optimum travel speed to be established. Too low speed causes

overlapping & Too high speed causes undercut.

D. Subsequent passes can be Carried out with weaving.






F. FILLET WELDING TECHNIQUES ( Contd..)

2. Horizontal Position ( 2F)







2. Horizontal Position ( 2F) ( Contd..)

Procedure:

A.First pass to be deposited with minimum weaving.

B.The arc should be concentrated at the root as Shown in the figure to

ensure good fusion.C.subsequent passes are also carried out with minimum weaving and

in the sequence shown in the figure.







3. Vertical Position ( 3F)

Weaving technique

for First pass

Weaving technique

for 2nd & 3rd Pass







3. Vertical Position ( 3F) ( Contd..)

Procedure:

A.Carry out welding from bottom to top to achieve high efficiency

joints.

B. Weaving to be carried out for all the passes including first pass.C. Technique of weaving for all passes is shown in the figure.






G. VARIOUS FILLET PROFILES & WELDING SYMBOLS

Desirable fillet Profiles

Unacceptable fillet Profiles






SUMMARY

• Fillet is a Triangular Cross sectional Area joining twosurfaces at right angles to each other. Used for joining T,Lap and corner Joint.

• Throat is the shortest distance from root of the fillet to weldface. Strength of the fillet depends upon Throat dimensions.

• Leg length of fillet is the shortest distance from root of the joint to the toe of the fillet weld. Also referred as Fillet size.

• Throat size = 0.707 x Leg Length ( Fillet size).

• Doubling the leg length doubles the throat dimensions ,increases the weld cross sectional area and electrodeconsumption by approximately four times.

• Main reasons for Excessive Convexity are too low welding

current & improper welding technique.Excessive Convexitygives a notch effect & acts as a stress raiser adverselyaffecting fatigue life of a component.






SUMMARY ( Contd…)

• Excessive Concavity occurs because of too high welding

current & improper welding technique.Excessive Concavityreduces the throat size & also causes reduction in Ultimate

Strength of the component.

• Main reasons for oversize fillet welds are :

a. High welding currents.

b. Slow travel Speed.c. Improper welding technique.

Remedies to avoid oversize fillet welding are :

a. Adhere to specified welding procedures and parameters.

b. welding Upto specified weld size as per requirements.c. Close supervision is required.






SUMMARY ( Contd…)

• Main reasons for undersize fillet welds are:

a. Low Welding Current.b. High welding Speed.

c. Improper Electrode Positioning.

Remedial measures are:

a. Adhere to specified welding procedures and parameters.

b. Use of sufficient current and appropriate travel speed.






THANK YOU

Fillet Welding

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