type of welding
What do you mean by following type of welding?
A. SMAW B. TIG
A. SMAW :- Shielded Metal Arc Welding.
B. TIG :- Tungsten Inert Gas Welding.
TIG welding set
Mention the contents of the TIG welding set?
A. Torch : Consist of hose for argon gas / welding lead / ceramic nozzle / collet / tungsten rod as cathode to create arc.
B. Regulator with pressure gauge (HP & LP) & flow meter.
C. Argon cylinder – Gr.2 / Gr.1 depending upon requirements of the job.
D. Transformer / rectifier.
E. Filler wire
Rule to calculate Welding
While welding the pipe trunnion to the pipe / reinforcement pad you have to put a hole or leave some portion of welding why?
For venting of hot gas which may get generated due to welding.
What is the thumb rule to calculate current required for Welding?
Current (Amp) = [Diameter of Electrode (mm) X 40]20
What is the minimum thickness of cs pipe that requires stress relieving to be done as per B31.3?
19.05 mm thk.
Which is the electrode & filler wire used for welding
Which is the electrode & filler wire used for welding of following materials?
A. Alloy steel
I. ASTM A335PI
II. ASTM A335P2
III. ASTM A335P11
IV. ASTM A335P5
V. ASTM A335P9
B. Stainless steel
I. ASTM A312TP304
II. ASTM A312TP304L
III. ASTM A312TP304H
IV. ASTM A312TP308
V. ASTM A312TP310
VI. ASTM A312TP316
VII. ASTM A312TP316L
VIII. ASTM A312TP316H
IX. ASTM A312TP321
X. ASTM A312TP321H
Answer:-
Covered electrode bare electrode
A.Alloy Steel
I. ASTM A335PI E7018 E70 S- 1B
II. ASTM A335P2 E8018 - B1 ---
III. ASTM A335P11 E8018 - B2 ER515
IV. ASTM A335P5 E502 ER502
V. ASTM A335P9 E505 ER505
B.Stainless Steel
I. ASTM A312TP304 E308 ER308
II. ASTM A312TP304L E308L ER308L
III. ASTM A312TP304H E16- 6-2 ER16-8-2
IV. ASTM A312TP308 E309 ER309
V. ASTM A312TP310 E310 ER310
VI. ASTM A312TP316 E316 ER316
VII. ASTM A312TP316L E316L ER316L
VIII. ASTM A312TP316H E16- 8-2 ER16-18- 2
IX. ASTM A312TP321 E347 ER347
X. ASTM A312TP321H E16- 6-2 ER16-8-2
What is mean by ‘PWHT’
What is mean by ‘PWHT’? Why it is required?
“POST WELD HEAT TREATMENT” This is done to remove residual stress left in the joint which may cause brittle fracture.
Why pre- heating is done on some pipe before starting welding?
To slow down the cooling rate.
Why post-heating is done on some pipe after the welding is over?
To maintain uniform homogeneous structure.
pre-heat temperature for carbon steel, post heating required for carbon, pre-heat temperature during stress reliving
What is the pre-heat temperature for carbon steel above 19.05MM thk?
Pre – heat temperature for carbon steel above 19.05 mm is 80C.
Is post heating required for carbon steel material above 19.05MM thk?
No, post heating is not required for carbon steel material of any thickness.
What is the soaking temperature during stress analysis for carbon steel material?
Soaking temperature for carbon steel material during stress relieving is 620C. (20C)
What is the soaking period during stress relieving for carbon steel material?
Soaking period for carbon steel material during stress relieving is 1hr.
What is the rate of heating & cooling during stress relieving for carbon steel material?
The rate of heating & cooling for carbon steel material during stress relieving is 150c/hr.
What is the pre-heat temperature during stress relieving for alloy steel materials?
Pre - heat temperature for AS materials is 180C.
What is the soaking temperature during stress relieving for alloy steel material?
Soaking temperature for alloy steel material is 720C(20C).
What is the soaking period during stress relieving for alloy steel material?
Soaking period for alloy steel material is 2hrs.
What is the rate of heating & cooling during stress relieving for alloy steel material?
The rate of heating & cooling for alloy steel material is 100C/hr.
What is the post heat temperature for alloy steel material?
Post heat temperature for alloy steel material is 300C.
Where the use of electrode, hydrotest for CS & SS pipes
Where the use of electrode E7018 is recommended?
The use of electrode E7018 is recommended for welding the following:-
A. For high strength steel.
B. For high thickness carbon steel plates.
C. Higher carbon equivalent material.
Why is the electrode E7018 called a low hydrogen electrode?
The low hydrogen electrodes have in their coating ingredient, which produces carbon di-oxide during melting. This CO2 gives a gaseous shielding for the metal and prevents atmospheric hydrogen from entering the arc atmosphere. By this way the weld metal has a low level of hydrogen.
What should be the content of chlorine in water while conducting hydrotest for CS & SS pipes?
For CS – 250 PPM.
For SS – 30 PPM.
What is the effect if the quantity of hydrogen induced in weld metal is more?
When hydrogen is more in weld metal, it tends to make the material brittle & subsequently leads to cracking. These cracks are called hydrogen induced cracking or delayed crack. To avoid this the electrode before using is baked at 250C to 300C for one hour in the mother oven & then cooled down to 100C in the same oven & finally transferred to a portable oven for use where temperature is maintained at 60 to 70.