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Fusion Welding

Welding Glossary

If you are unfamiliar with welding, the following site is an excellent glossary of welding terms.

http://www.hobartwelders.com/elearning/glossary.php

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Definition

• Fusion welding is a group of processes that bond metal together by heating a portion of each piece above the melting point and causing them to flow together.• Usually includes the uses a filler

material to insure the joint is filled.

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Fusion Welding Process

1. “Welding and cutting requires good eye-mind-hand coordination.”

2. Must be able to concentrate.3. Must see and understand the

activity in the molten metal as the process is occurring.

4. Thorough understanding of the operation of the equipment.

5. Must have good depth perception.

6. Must be able to determine the time and place to apply heat and/or filler metal.

7. Maintain a good body position so it is possible to look left and right, and ahead and behind the puddle.

8. Must know the quality standards.

9. Must understand the procedures for inspecting work.

10.Must learn safe work habits.

Learning the basics

Fusion Welding Requirements

All fusion welding processes have four requirements. Heat Shielding Filler material Critical distance

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Fusion Welding--Heat

Sufficient heat must be applied to the weld zone to raise the temperature above the melting point.

Melting point is different for each material.

Material Melting Point (oF)

Tin 450

Lead 620

Zinc 786

Aluminum 1,220

Silver 1,760

Copper 1,980

Cast Iron 2,300

Material Melting Point (oF)

Steel (HC) 2,500

Stainless Steel 2,550

Steel (MC) 2,600

Steel (LC) 2,700

Iron 2,800

Chromium 3,000

Titanium 3,260

Fusion Welding—Heat—cont.

1 A metal with higher melting temperature will require more heat to fusion weld than a metal with a lower melting temperature.

2 The larger the mass of metal, the greater the amount of heat that will be required to raise the temperature above the melting point.

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Two important principles

Conclusion: you must be able to adjust the heat produced to match the needs of the weld.

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Fusion Welding—Heat--cont.

To be able to adjust the heat, you must know the source of the heat.The source of the heat is one of the distinguishing characteristics between the welding process.

SMAW

GMAW

FCAW

GTAW

OFW

Electric arc

Electric arc

Gas Flame

How is the heat produced adjusted for each fusion welding process?

Electric arc

Electric arc

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Fusion Welding--Shielding

Steel is produced in an environment devoid of atmospheric air.

If atmospheric air is allowed to mix with the molten metal during the fusion welding process the quality of the weld is reduced.

The method used for shielding is another difference between the common welding processes.

SMAW

GMAW

FCAW

GTAW

OFW

Inert gas from flux

Inert gas from cylinder

Gas Flame

Inert gas from cylinder

Inert gas from flux

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Fusion Welding--Filler Material

If filler material is not added during a fusion welding process the joint will be starved.

Starved joints have reduced strength.

For this reason, joints are usually slightly over filled (reinforced) to insure the strength is not reduced.

Reinforcement does not increase the strength of the weld, just insures the joint is not starved.

Excessive reinforcement is wasted resources. Excessive reinforcement may need to be removed = additional cost..

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Fusion Welding--Filler Material--cont.

The source of the filler material is also one of the differences between the different welding processes.

SMAW

GMAW

FCAW

GTAW

OFW

Consumable electrode

Continuous wire electrode

Manual rod

Manual rod

Continuous wire electrode

How is the rate of filler material delivery changed for each process?

Fusion Welding—Critical Distance

Each fusion welding process has a critical distance that must be maintained.

Failure to maintain the critical distance can reduce the quality of the weld and/or damage equipment.

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Critical distances:

SMAW

GMAW

FCAW

GTAW

OFW

Arc length

Stick out

Stick out

Arc length

Tip clearance

Four Requirements Summary

To be able to fusion weld you must be able to set the machine for the correct heat, insure the weld pool is adequately shielded, control the rate of delivery of the filler material and maintain the critical distance.

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Fusion Welding’s Five (5) Factors Which Determine The Quality Of The Weld

Angle

Heat

Manipulation

DistanceSpeed

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Heat

What units are used to measure heat?

In fusion welding processes, the amount of heat must be sufficient to raise the temperature of the metal above the

melting point.

Are temperature and heat the same?

What units are used to measure temperature?

What determines the amount of heat that will be required to complete a weld?

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Heat—cont.

Six (6) ways of controlling welding heat

1. Equipment size

6. The travel speed

4. The Manipulation of the heat source

2. Equipment settings

3. Distance from heat source to work

5. Heat source angle

Heat—Equipment Size

In all fusion welding processes the effective heat at the weld is influenced by the size of the components being used.

SMAW

GMAW

FCAW

GTAW

OFW

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Electrode diameter

Wire diameter

Filler rod diameter, tungsten electrode diameter

Filler rod diameter, tip size

Wire diameter

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Heat—Equipment Setting

In all fusion welding processes the effective heat at the weld is influenced by the settings on the equipment.

SMAW

GMAW

FCAW

GTAW

OFW

Amperage

Voltage, wire speed

Amperage, polarity

Torch, regulators

Voltage, wire speed

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Heat--Distance

All welding and cutting processes have a critical distance.

The critical distance varies with each welding process.

The quality of fusion welds will be reduced if the critical distance is varied beyond the recommended limits.

OFW

SMAW

GMAW

FCAW

GTAW

Process Distance Identification

inner cone to work

electrode end to work

contact tube to work

end of tungsten to work Arc length

Arc length

Torch gap

Stick out

contact tube to work Stick out

What are the results of insufficient or excessive distance for each process?

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Heat--Manipulation

You must insure manipulation is necessary to produce the desired weld.

Manipulation (movement) is used to:

1. Control puddle in vertical, horizontal and overhead welds.

2. Fill joint

3. Produce desired appearance

Two points to remember

1. Make sure there is a sound reason for the manipulation.

2. Select a manipulation pattern that will produce the desired results.

Some outcomes of improper manipulation

1. Reduced depth of fusion.

2. Undercutting

3. Porosity

4. Slag inclusions

5. Unnecessary wear on joins of fingers and wrist.

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Heat--Angle

• Two angles are important in fusion welding

work

travel

The ideal angle is different for each type of weld, welding position and welding process.

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Heat--Speed

The ideal travel speed is different for each weld, weld position and welding process.

Operator must watch the welding process and adjust speed as needed.

Speed indicators are:

A. Size of bead

B. Shape of ripples

C. Depth of penetration

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Types of Welds

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Five Types of Welds

Surface

Groove

Fillet

Plug

Slot

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Surface Welds

Surface welds are welds were material has been applied too and/or blended with the surface of the work piece.

Two common applications are for hard surfacing and padding.

Surface weld nomenclature

A: Electrode wire

B: Electrode flux

C: Arc

D: Weld puddle

E: Bead

F: Slag

G: Gas shield

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Groove Welds

Groove welds are used to fuse the sides or ends of two pieces of metal.The primary use of groove welds is to complete butt joints.

Groove weld nomenclature

A: ToeB: WidthC: Face reinforcementD: ToeE: Joint preparationF: Joint gapG: Root reinforcementH: Joint faceI: Base metal

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Fillet Welds

Fillet welds have a triangular cross section and are used to fuse two faces of metal that are at a 90 degree angle to each other.

Three common types are:

T Lap Corner

Fillet weld nomenclature

A: ReinforcementB: ToeC: FaceD: ThroatE: ToeF: LegG: RootH: Base metalI: Leg

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Plug Welds

Plug welds are used to attach two surfaces together when a complete joint is not required and the design does not allow for any weld bead outside the dimensions of the metal.The holes can be made with a drill bit.

The weld is completed by establishing the arc on the bottom plate and then continuing to weld until the hole is full.

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Slot Welds

Slot welds are identical to plug welds except for the shape of the holes. For slot welds, slots are machined or stamped in the upper plate.

They are completed the same as plug welds.

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Five Types of Joints

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Five Types of Joints

Butt

Lap

T

Corner

Edge

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Butt Joints

Used to attach two metal faces together. Joint can be completed with the faces square or beveled.

What type of weld is used to complete a butt joint?

How do you determine if you need to bevel a butt joint?

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Butt Joint--Multipass

Three examples for 1/8 inch SMAW electrode:

1/4 inch and less; single pass, single side.

3/8’s inch to 3/4 inch; joint prep and multiple pass.

1/4 inch to 3/8’s inch; single pass, two sides or joint prep and one side.

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Corner Joints

Three common types:Joint Weld

Closed Groove weld

Partially open Fillet weld

Fully open Fillet weld

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Lap Joints

Lap joints are use to attach metal that overlaps.

A lap of three times metal thickness provides maximum strength.

Welding both sides increases strength in both directions.

What type of weld is used to complete a lap joint?

When would a multiple pass lap joint be made?

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Edge Joints

Used to weld two surfaces at 180 degrees.

What type of weld is used to complete an edge joint?

When would a multipass weld be used to complete an edge joint?

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Five Welding Positions

Flat

Vertical up Vertical down

Horizontal

Overhead

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Questions