TITLE: SHIELDED METAL ARC WELDING (SMAW)

OBJECTIVE:

1. To identify the parameter for SMAW process

2. To analyse the relationship between welding parameter and the welded part.

3. To determine the strength of welded joint by varying the welding parameter

4. To observe the defect caused by welding parameter.

INTRODUCTION:

Arc welding is one of alternative for joining process in manufacturing. Arc welding process

had done by create an electric arc between electrode and the base material to melt the

metal at the welding point using welding power supply. The welding region is sometimes

protected by some type of inert or semi-inert gas, known as a shielding gas and sometime

adds by an evaporating filler material.

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

informally as stick welding, is a manual arc welding process that uses a consumable

electrode coated in flux to lay the weld. They can use either direct current (DC) or alternating

current (AC) from a welding power supply, 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.

Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG)

welding or metal active gas (MAG) welding, is a semi-automatic or automatic arc welding

process in which a continuous and consumable wire electrode and a shielding gas are fed

through a welding gun. A constant voltage, direct current power source is most commonly

used with GMAW, but constant current systems, as well as alternating current, can be used.

There are four primary methods of metal transfer in GMAW, called globular, short-circuiting,

spray, and pulsed-spray, each of which has distinct properties and corresponding

advantages and limitations.

APPARATUS:

Welding Machine (90 A) Welding Hand Tool

Welding Plate Chalk Plate

Welding Machine (95 A) Welding Rod

INDUSTRIAL APPARATUS:

Scan Laser Welding Machine

The laser welding machine also the industrial apparatus for welding. The laser welding machines no need other process after welding, as the thermal deformation is minimal, no backing roll mark on the workpiece. Besides that, it’s adopt scan head with welding system, it’s suitable for spot welding on various small thin-wall parts. The welding speed also fast, the big spot welding speed can reach to 20 spots per seconds.

BX1C AC ARC Welding Machine (BX1-250C)

This machine come with complete accessories such as electrode holder and earth clamp. It has 470×265×315mm in dimension. This machine also has single-phase fan-cooled, movable cable, thermostatic protection

EXPERIMENTAL PROCEDURE:

1. Students are needed to wear safety equipment such as gloves, apron, safety boots

and eye shielded before conduct or do the SMAW process.

2. Technician was explained the SMAW process before student start to conduct the

experiment.

3. Metal scrap was given as a tested specimen for student to train their skill on the

welding process.

4. Then, the current was setup 90A and 95A before the real SMAW process begin.

5. The two plates of mild steel were being arranged and clamped. The distance

between 2 plates was being specified as 2.6mm and the type of joint was butt joint.

6. The welding plate was connected to the welding machine where the one clamp is

attached to electrode and the other one is attached to ground.

7. The operation of welding was operating by remove the coated rode at the ends of the

rode that called as scratch process to avoid the rode stick to the plates during

operation.

8. The SMAW process was begun with the two plates of the mild steel with the angle of

the electrode to the plate is around 60o-70o.

9. The welded part was being removed using hammer and cleaning process using the

brush.

10. Then, the plate was marked with the chalk to be cut into 20mm or 30mm and the

remaining of the plate was removed and become scrap.

11. Step 5 – 10 was repeated using 95A on the SMAW machine.

12. The needed plate was being tested on the tensile test machine and all the

parameters is being setup on the computer.

13. The tensile test machine was turned on and the plates was being clamped to the

tensile test machine.

14. Lastly, the plates were stretch until the welded part broken and split into two.

15. The data of the tensile strength and the graph have been recorded.

RESULT AND DATA ANALYSIS:

The Welding Plate that used 90 amp and 95 amp

Welding Plate ( 90 Amp) Welding Plate ( 95 Amp)

DISCUSSION

Based on the experiment, we are able to identify the parameter for SMAW process. SMAW

is a manual arc welding process that uses a consumable electrode covered with a 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. The work piece and the electrode melts forming the weld pool that

cools to form a joint. 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. General parameters of SMAW are current,

length of arc, angle, manipulation and speed.

Based on the discussion, we are also able to analyse the relationship between welding

parameter and welded part. One of the parameter that was be analyse is about to consider

the value of current that used. For example, on our experiment the current was be set for the

90 Amp and 95 Amp. In SMAW, amperage generally will affect the size and penetration of a

weld bead when we moving our torch at the right speed. The conclusion that can be is the

higher the current used, the fastest of the speed movement. Besides that, the length of the

arc also can affect the welded part. When the welder holds the welding electrode is too close

to the work plates, the amount of current and the heat going into the joint were affected. As

an example, if the held further away, the electrode produce less heat and more spatter. It will

give the result of the welded part has low quality on joining or bad result. To get the best

result, we need to control the length of arc between on 2mm or 3mm during the process.

Next, we can analyse about the angle during the weld process. On the theory, there are two

torch angles when welding which is 90 degrees or an angle between 30 to 50 degrees.

The different result will show for each angle such as when we used angle of 90 degrees, the

process allowing maximum heat and current focused down into the open groove butt joint.

For the angle between 30 and 50 degrees, it gives the welder a better view. When we drag

the torch, the tilt is directed towards the puddle, which helps with penetration and achieving

a thick bead. Other relationship is about the speed of the welder process. Based on our

analysis, if we move too fast, the size of the weld will be small and achieve insufficient

penetration. When we move too slow and the result will a fat weld bead and likely too much

heat going into the work plates.

We are also able to determine the strength of welded joint that was tested in the strength

laboratory. Based on the result, we can says that current at 95 amp is higher strength and

good quality than the current at 90 amp. It can be proved when we compare the value of

tensile strength at 95 A and 90 A which is 216.33 N/mm2 and 140 N/mm2 respectively.

While, when compared it based on the graph, it also give the same result. For the 95 A, the

specimen will brake when force at the 24 kN and the 90 A at the 18 kN.

Lastly, we able to observe the defect caused by welding parameter. One of the defect is

incomplete fusion and penetration. This defect will produces poor weld beads and to prevent

it, we need to raising the temperature of the based metal and cleaning the weld area before

welding process. Other defect that occur is weld profile, its effects on the strength and

appearance of the weld.our result can be classified on underfilling because when the joint is

not filled with the proper amount of weld metal.

CONCLUSION

As conclusion, the objective can achievable to do the practical welding. the student must

have skill to do welding, used the knowledge and understanding of the theories, and also

welding techniques are apllied in the practical welding. the practical task have been

complete and the report will accomplished to prove the student can be do the practical task

of Shielded metal arc-welding (SMAW).

RECOMMENDATION

There are many welding troubleshooting occur in this process. We recommend for:

Lack of fusion (failure of weld metal to fuse completely with base metal or a

preceding weld bead):

Use proper welding techniques:

Must be eliminated for a sound weld

Place stringer bead in proper location at joint during welding.

Adjust work angle or widen groove to access bottom during welding.

Momentarily hold arc on groove side walls when using weaving

technique.

Keep arc on leading edge of weld puddle.

Shallow penetration (shallow fusion between weld metal and base metal):

Use proper welding techniques:

Keep arc on leading edge of weld puddle.

Fast travel speed.

Allow some gap at the bottom of the joint.

Excessive penetration:

Use proper welding technique:

Decreasing travel speed.

Porosity (small cavities or holes resulting from gas pockets in weld metal):

Possible Cause – arc length too long, workpiece dirty and damp electrode

Reduce arc length

Remove grease, oil, moisture, rust, paint, coatings, slag and dirt

from work surface before welding

Use dry electrode

REFERENCES

Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). Manufacturing processes

reference guide. New York: I Cary, Howard B.; Helzer, Scott C. (2005). Modern

Welding Technology. Upper Saddle River, New Jersey: Pearson Education, Pages

700.

Cary, Howard B.; Helzer, Scott C. (2005). Modern Welding Technology. Upper

Saddle River, New Jersey: Pearson Education, Pages 500. 

N.A, “Welding parameters”, Welders universe, retrived on 1 November, from

http://www.weldersuniverse.com/welding_parameters.html

Fiza, “Welding (SMAW)”, welding flux, retrived on 1 November, from

http://docslide.us/documents/lab-report-welding-smaw-fiza.html

Steven R.S, Serope K (2014), “Manufacturing engineering and technology”, fusion

welding process, 7th ed, Pearson, Singapore, Pages 877

American Welding Society (2004). Welding Handbook, Welding Processes, Part 1.

Miami: American Welding Society, USA, Pages 445.