Tugas 2 Welding

MUHAMMAD ANDRI ALKAUTSAR R.1106070073METALURGI DAN MATERIAL

Tugas 2 Welding

1. Comparing to riveting, welding has various advantages and disadvantages. Pick out

three (3) advantages and three (3) disadvantages of welding respectively.

Kelebihan:

Bisa mendapatkan kekuatan tarik yang baik karena adanya distribusi aliran

tegang yang seragam

efisiensi material yang digunakan lebih tinggi, karena tidak dibutuhkan

sejumlah luas material sebagai tempat direkatkannya material tersebut.

welding dapat diaplikasikan pada banyak logam

Kekurangan:

Rentan terkena korosi.

Material yang dilas mengalami perubahan mikrostruktur karena pengaruh

panas yang diberikan.

Selain itu, proses yang dilakukan lebih sulit dan lebih mahal, serta

membutuhkan temperatur tinggi

2. Welding processes are able to be classified into the category of (a) fusion welding,

(b)

pressure welding or (c) soldering. What the following welding processes should be

classified

into the category of (a), (b) or (c). Put a category mark (a), (b) or (c) for each welding

process.

• Friction welding (b)

• Electron beam welding (a)

• Electro slag welding (a)


• Thermit (Almino-thermic) welding (a)

• CO2 gas shielded metal arc welding (a)

• Soft soldering (c)

• Submerged arc welding (a)

• Resistance spot welding (a)

• TIG welding (a)

• Ultrasonic welding (b)

3. Welding processes may be classified according to the type of energy source used

directly

for welding. Choose the welding processes from Group B that belong to the energy

sources

in Group A, and put the corresponding marks in the parentheses

Electric Energy Submerged Arc Welding, SMAW,

MAG, Electro Slag

Welding, Resistance Welding,

Plasma Arc Welding

Mechanical Energy Explosion Welding, Friction Welding

Chemical Energy Oxy-flame Welding

Light Energy Laser Welding

4. Welding processes may be classified according to the types of energy source utilized

directly

or welding. Choose the energy source in [Word group] that is applied in each welding

process, and put its alphabet into each


Energy sources :

Electric energy = a

Mechanical energy = b

Chemical energy = c

Light energy = d

Welding Processes

MAG welding (Electical Energy) (a)

Aluminothermic welding (c)

Electron beam welding (a)

Oxy-fuel gas welding (c)

Friction stir welding (b)

Laser welding (d)

Manual metal arc welding (SMAW) (a)

Explosion welding (b)

TIG welding (GTAW) (a)

Electroslag welding (a)

5. Regarding the features of the following welding and cutting processes, choose the

relevant one from among the words in the word group given below and enter its

alphabetic symbol into each parenthesis.

MAG Welding (a)

Laser Welding and Cutting (d)

Submerged Arc Welding (a)

Friction Welding (b)

Gas Welding (c)

Word group


(a) Electrical energy

(b) Mechanical energy

(c) Chemical energy

(d) Light energy

6. Regarding the classification of welding processes, choose five (5) gas-shielded arc

welding processes and encircle their alphabets.

(a) stud welding

(b) TIG welding

(c) laser welding

(d) submerged arc welding

(e) self-shielded arc welding

(f) MAG welding

(g) shielded metal arc welding

(h) electro-slag welding

(i) brazing

(j) electro-gas arc welding

(k) resistance spot welding

(l) MIG welding

(m) electron beam welding

(n) plasma arc welding.

Submerged Arc Welding

Electro Gas Arc Welding

Shielded Metal Arc Welding

TIG Welding

MIG Welding

7. In case of using 100% CO2 gas as shielding, droplet size is becoming larger than that

in


case of using CO2 – Argon gas mixture. Explain the reasons.

Gas CO2 adalah gas yang paling umum digunakan pada MIG welding. Gas ini dapat

digunakan dalam kondisi murni, dimana tidak membutuhkan gas inert lainya dalam

proses. CO2 juga terbilang murah dibanding gas – gas lainya, ini juga merupakan

salah satu faktor mengapa co2 sering digunakan. Gas CO2 murni dapat menghasilkan

penetrasi yang bisa tergolong sangat dalam, dimana sangat berguna untuk mengelas

material yang tebal. Tetapi jika kita menggunakan CO2 murni, gas ini akan

menghasilkan arc yang kurang stabil jika dibandingkan dengan kita memakai gas

campuran CO2 dengan gas lain.

8. The following sentences describe the metal transfer modes. Choose the relevant one

and put its alphabet into each parenthesis.

The molten metal droplet, which is detached from the tip of the electrode by

the arc force,transfers along the cavity wall in the flux covering around the

electrode. This metal transfer mode can be observed in submerged arc

welding. (Flux-wall-guided transfer)

The molten metal droplet is punctured by rapid expansion of the internal

gases generated in the droplet. This metal transfer mode can be observed in

shielded metal arc welding.(explosive transfer)

The molten metal droplet grows in size as large as the electrode diameter or

larger to transfer. This metal transfer mode can be observed in shielded

metal arc welding with low-hydrogen type electrodes and CO2-shielded arc

welding with high currents. The both amount and size of the spatter

increases in general. (Globular transfer)

The molten metal droplet whose diameter is as small as the electrode

diameter or smaller transfers in free flight in the arc column. This metal

transfer mode can be observed in MAG welding with high currents and Ar-


rich shielding gas (Ar: 80% or larger) and MIG welding. In general, spatter

decreases, and the arc is likely to become stable. (Spray transfer)

The molten metal droplet, which is developed on the tip of the electrode,

makes a contact to the weld pool and is transferred with the aids of the

electromagnetic pinching effect and the surface tension of the droplet. This

metal transfer mode can be observed in MIG and MAG welding with low

current, low arc voltage, and short arc length. This transfer mode is suitable

for sheet metal welding and welding. (short-circuiting transfer)

9. Regarding the metal transfer modes, choose the relevant one in the word group and

enter its alphabet into each parenthesis.

CO2-shielded arc welding with low currents. (a)

Pulsed MAG welding with low average currents (c)

CO2-shielded arc welding with medium currents. (b)

MAG welding with high currents and a mixed shielding gas of

80%Ar+20%CO2. (c)

MIG welding with high currents. (d)

Word Group

(a) short-circuiting transfer (b) globular transfer

(c) spray transfer (d) explosive transfer

10. The following sentences are describing electrode wire melting and metal transfer

modes in MAG welding with solid wire. Choose the relevant one and circle its

alphabet.

Wire melting rate is given mainly by the heat from the arc and also the

following due to the current flow in the wire. (resistance heat)


When the wire melting rate (or wire feeding speed) is kept constant, welding

current may change if the following parameter is changed. (welding speed)

In MAG welding using 100% CO2 gas for shielding gas, when higher arc

voltage is applied, the arc is becoming unstable. In that case at lower welding

current, usually the following metal transfer mode is adopted at lower arc

voltage. (short-circuiting transfer)

In MAG welding with Argon base mixture shielding gas (Ar + CO2) spray

transfer mode may be obtained by increasing the following parameter more

than a certain critical value. (welding current)

In spray transfer mode, the force which acts to detach the droplet from the

wire tip is mainly the following. (plasma stream)

11. Pick out a non consumable electrode gas-shielded arc welding process using DC

power

source with constant current characteristics. And then give the kind of shielding gas,

the

material of electrode and the polarity of electrode, when the process is applied on

welding

of stainless steel.

Welding Process (Gas Metal Arc Welding)

Shielding Gas (Agon - Helium)

Material of Electrode (E310-15 or E310-16)

Polarity of Electrode (Straight Polarity)

12. Pick out at least three (3) advantages and three (3) disadvantages of TIG arc welding

process.

Kelebihan :

Kualitas hasil lasan yang bagus


Dapat digunakan di berbagai posisi pengelasan

Tidak memakai filler material

Kekurangan :

Diperlukan kemampuan mengelas yang tinggi

Diperlukan peralatan yang rumit

Poduktivitasnya rendah.

13. Give four (4) advantages and four (4) disadvantages of SAW, comparing with the

SMAW (Manual metal arc welding).

Advantages :

Arc is not visible

Deep penetration allowing in the use of small welding grooves

Little smoke are developed

Disadvantages :

High cost needed

Can be used between flat and horizontal position

Limited for carbon, low alloy, creep resisting, stainless steel, and nickel

carbon

14. Pick out five (5) features of submerged arc welding process, comparing to manual

metal arc welding (shielded metal arc welding) process.

single pass welding process for thick plate

Economic process for thick plate

Used for flat position

Arc is not visible

Deep penetration


15. The sentences below, describing MAG welding, have error(s) in the parentheses.

Correct

them.

In the case of shielding gas containing argon mixed with 20% of CO2 gas, the

metal transfer mode become spray transfer (when the welding speed is

higher than a certain critical value). The correct one is current

Comparing with 100% CO2 gas shielded arc welding under the same welding

parameters, MAG welding with using mixed gas of 80% argon and 20% of

CO2 has (wider bead, but easily gets more spatter). The correct one is less.

16. Pick out at least three (3) features of TIG welding (GTAW), comparing with MMA

welding (SMAW).

Elektrodanya tidak meleleh karena terbuat dari tungsten.

Kawat pengisi dapat diumpan secara manual atau otomatis.

Menggunakan gas sebagai pelindung dan tidak menggunakan tekanan.

Arc terbentuk diantara elektorda dan kawah las

17. Pick out three (3) advantages and three (3) disadvantages of MAG welding

comparing to SAW (submerged arc welding) respectively.

Advantages :

Higher welding speed

Greater deposition

Less Post-weld cleaning of slag

Disadvantages :

higher initial set up cost

Atmosphere of welding environment must be stable (need of shielding gas)

Radiation effects are more sever


18. Pick out three (3) advantages and three (3) disadvantages of FCAW welding

comparing to MAG (metal active gas) welding respectively.

Advantages :

Higher welding speed compared to SMAW

Possible to any welding position

More efficient compared to MIG

Disadvantages :

Slag must be cleaned on the pass

Existence of smoke and UV radiation

High possibility of formation of slag inclusion

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Tugas 2 Welding