manual metal arc welding ( mmaw )

7/29/2019 Manual Metal Arc Welding ( MMAW )

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Arc welding with coated electrodes is a manual process where the heat source consists of

the electric arc. When the arc strikes between the coated electrode (by means of an electrode

holder) and the piece to be welded (base material), it generates heat which causes rapid

melting of both the base material and electrode. The welding circuit consists essentially of the

following elements:

Power source

Electrode holder

Coated electrodes

Earth clamp and earth cables.

As illustrated in figure 1 below.


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Shielded metal arc welding (SMAW), also known as manual metal arc welding

(MMAW), flux shielded arc welding or informally as stick welding, is a manual arc welding

process that uses a consumable electrode coated in flux to lay the weld. An electric current, in

the form of either alternating current or direct current from a welding power supply, is used

to form an electric arc between the electrode and the metals to be joined. As the weld is laid,

the flux coating of the electrode disintegrates, giving off vapours that serve as a shielding gas

and providing a layer of slag, both of which protect the weld area from atmospheric

contamination.

Welding is a fabrication or sculptural process that joins materials, usually metals or

thermoplastics, by causing coalescence. This is often done by melting the work pieces and

adding a filler material to form a pool of molten material (the weld pool) that cools to become

a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce

the weld. This is in contrast with soldering and brazing, which involve melting a lower-

melting-point material between the work pieces to form a bond between them, without

melting the work pieces.


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1) To improve the skill of welding especially Manual Metal Arc Welding.2) To understand the process, the true way of welding and become professional in the

welding process.

3) Understand the risk of the welding process and learn the way to weld in the safer way.4) To born a many professional skill in welding.5) To obtain good welding results.6) Applying the project as the Manual Metal Arc Metal Welding subject requirement.7) Practice and know the machine and tools that use in Manual Metal Arc Welding.


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PRINCIPAL OPERATIONS OF PROCESS

Manual metal arc welding is performed by striking an arc between a coated-metal

electrode and the base metal. Once the arc has been established, the molten metal from the tip

of the electrode flows together with the molten metal from the edges of the base metal to

form a sound joint. This process is known as fusion. The coating from the electrode forms a

covering over the weld deposit, shielding it from contamination.

The process allows only short lengths of weld to be produced before a new electrode

needs to be inserted in the holder. Weld penetration is low and the quality of the weld deposit

is highly dependent on the skill of the welder.Therefore the process is called shield metal arc

welding or (SMAW). The main advantages of manual metal arc welding are that high-quality

welds are made rapidly at a low cost.

THE ARC CAUSE

i. The base metal to melt, forming a weld poolii. The tip the electrode metal core to melt and metal droplets to project into the weld

pool

iii. The flux coating to melt providing a gaseous shield around the arciv. The flux coating to deposit a protective slag covering on the molten weld pool

The melting rate of the electrode metal depends on the amount of electric current used.


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PROCEDURE

Below are the stage and the procedure to welding.

First Stage

1. Switched on the main switch

Figure 2: Main Switch


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2. Switch on the welding machine and setup it for the right electric current and the right

setting.

Figure 3: Welding Machine

3. Takes two pieces of Low Carbon Steel (LCS)

Figure 4: Low Carbon Steel (LCS)


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4. Take electrode with 3.2mm size. It depends on the thickness of the plate.

Figure 5: Electrode

5. Adjusted the Air Vacuum for it absorb the poisonous gas when we start welding.

Figure 6: Air Vacuum


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Second Stage

1. Make the plate form the shape ofT. The angles are 90 degree.

Figures 8: The shape of T

2.Weld a bit at the end of the plate as a tag to make sure the plate stay in the form ofT

shape.

Figures 9: Weld at the end of the plate

3. Start the welding process.

Figures 10: Start welding


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Third Stage

1. Remove the slag by using chisel shipping hammer.

2. Make sure the project look nice and smart without slag.

Figure 11: Cleaning Process

Last Stage

1. Do the housekeeping to make sure it can be easily use when anyone want to use it for weld

next time.

Figure 12: Clean and Tidy after Housekeeping


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2. Fill up the WPS form and give it to the lecturer.

1. Gloves

Figure 13: Hand Gloves

* To protect our hand from electric, sharp tools, heat and etc. It does also can prevent

accident when we weld.

2. Chipping Hammer

Figure 14: Chipping Hammer

* Use to remove slag.


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3. Welding Shield

Figures 15: Welding Helmet/Shield

* Mask used to protect the eye sand sprinkle face contact with welder.

* It also protects the welder from the rays ultra violet that can harm the eyes.

4. Hammer

Figures 16: The hammer

* Use with chisel to clean slag.


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5. Chisel

Figures 17: Chisel that use with hammer

* Use to remove wax and slag of welding.

6. Wire Brush

Figures 18: Wire Brush

* To clean the surface of the arc from the iron dust


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7. Pliers

Figures 19: The Big Pliers

*To lift or move the hot metal

8. Table vies

Figures 20: Vies Tables

9. Electrodes

Figures 21: Electrodes

* Used as a terminal or conductor arc welding.

* It works as filled rod.


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10. Welding Machine

Figures 22: High Technology Welding Machine

* Serves as a key figure in the welding process.

11. Safety Shoes

Figures 23: Safety Shoes

* To protect feet from dangerous things and hazard.


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12. Overall

Figures 24: Overall Clothes

* To protect body from any harm and hazards.


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There are three things that can be control when we welding use MMAW process. It is;

1. The Arc LengthThe length over which the electric are travel in the distance between the tip of the

electrode and the parent metal.

The short of arc length will cause;

i. The electrode is stick to the metal when we do the weld process.ii. Irregular pilling of the weld metal.

The long of arc length will cause;

i. The deposit to be coarse, rippled and flatter than normal with an increase inspatter.

ii. Penetration is to be reduced.

2. Travel SpeedThe operator of the welding control the speed at which the electrode pass over the

joint.

A slow rate travel will cause;

i. A wider, thicker deposit or shorter than normal length.ii. The slag to flood the weld pool.

iii. The weld pool to flood under the arc reducing its penetrating effect.


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A fast rate travel will cause;

i. Gives narrower, thinner deposit and longer than normal length may prevent adequatefusion and penetration.

3. Welding CurrentThe welding machine has variable current control. The required setting is depending

on the parent metal and the electrode used.

A low welding current can cause;

i. Cause the metal to pile up without adequate penetration into the parent metal.ii. Make the slag difficult to control.

A high welding current can cause;

i. Considerable spatter.ii. A deposit that is flatter and wider than normal with deeper penetration into the parent

metal.


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All students must share the welding bay because welding bays cannot accommodate

all students.

Dont waste the electrode when do the process because electrode is expensive things

and should be concerned about other students that want to use those things also.

Have to give enough time to student to do practice and task.


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Result


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For the conclusion the tasks that give to me have done successfully by working hard by

me. For me first, I thought this process was easy but when I do this task I completely wrong.

MMAW needs a stable hands skill, hardworking, confident and patience. But thank you to

my lecturer En Hazrul Nizam Bin Mohd Taha I can learn the technique and the right way to

welding with this process.

manual metal arc welding ( mmaw )

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