CSWIP 3.1: Question with Answer and Explanation – Part 12

 

CSWIP 3.1 QUESTION AND ANSWER SERIES

CSWIP 3.1: Question with Answer and Explanation – Part 1

CSWIP 3.1: Question with Answer and Explanation – Part 2

CSWIP 3.1: Question with Answer and Explanation – Part 3

CSWIP 3.1: Question with Answer and Explanation – Part 4

CSWIP 3.1: Question with Answer and Explanation – Part 5

CSWIP 3.1: Question with Answer and Explanation – Part 6

CSWIP 3.1: Question with Answer and Explanation – Part 7

CSWIP 3.1: Question with Answer and Explanation – Part 8

CSWIP 3.1: Question with Answer and Explanation – Part 9

CSWIP 3.1: Question with Answer and Explanation – Part 10

CSWIP 3.1: Question with Answer and Explanation – Part 11

CSWIP 3.1: Question with Answer and Explanation – Part 12

CSWIP 3.1: Question with Answer and Explanation – Part 13

CSWIP 3.1: Question with Answer and Explanation – Part 14

CSWIP 3.1: Question with Answer and Explanation – Part 15

CSWIP 3.1: Question with Answer and Explanation – Part 16

CSWIP 3.1: Question with Answer and Explanation – Part 17

CSWIP 3.1: Question with Answer and Explanation – Part 18

CSWIP 3.1: Question with Answer and Explanation – Part 19

CSWIP 3.1: Question with Answer and Explanation – Part 20

1) Cast and Helix are terms that refer to:

a. Ingredients in the flux covering
b. Bead deposition techniques for distortion control
c. ( answer ) Quality of the welding wires
d. Sources from which wires are drawn

weld 7.PNG

2) A MMA electrode which is classified as an E7024 (according to AWS) is a:

a. Basic type
b. Cellulosic type
c. Rutile type
d. ( answer ) Thick coated iron powder
We use “Exclusion principle”

weld 8.PNG

3) An electrode is classified to BS EN ISO 2560 as E 35 3 B. What does 35 signify?

a. ( answer ) 350 N/mm2 yield strength
b. 35 Joules -30oC
c. 35 N/mm2 tensile strength
d. 35ksi tensile strength

weld 9.PNG

Pls take note:

  • With BS EN ISO 2560: it is classified follow yield strength
  • With AWS A5.1 & A5.5: it is classified follow TENSILE STRENGTH

4) A large diameter pipe with a wall thickness of 10mm is to be used for a cross-country pipeline. Which electrode type could be used to combine high welding speed and deep penetration?

a. Basic covered
b. ( answer ) Cellulosic covered
c. Rutile covered
d. Iron powder loaded

weld 10.PNG

Cellulosic Electrode compositions are only available for welding low carbon non-alloyed steels although nickel additions may be made to improve notch toughness. Charpy-V values of around 27J at -20°C are possible in the unalloyed electrodes. The high hydrogen level means that any steel welded with these electrodes should be selected to have a very high resistance to hydrogen induced, cold cracking. They should not be used without giving due consideration to the steel composition, restraint and the need for preheat. The characteristics of deep penetration, high deposition rates and the ability to be used vertically down means that the main use for these electrodes is for cross country pipelining although they are used to a more limited extent for welding storage tanks.

Cellulosic electrodes contain a high proportion of cellulose in the coating and are characterised by a deeply penetrating arc and a rapid burn-off rate giving high welding speeds. Weld deposit can be coarse and with fluid slag, deslagging can be difficult. These electrodes are easy to use in any position and are noted for their use in the ‘stovepipe’ welding technique.

5) Which of the following electrode types would produce the highest levels of hydrogen?

a. Basic electrode when baked correctly
b. ( answer ) Cellulosic in a sealed tin
c. Rutile
d. Heavy rutile

weld 11.PNG

  • Cellulosic electrodes: hydrogen content is 80-90 ml/100 g of weld metal.
  • Rutile electrodes: hydrogen content is 25-30 ml/100 g of weld metal.
  • Basic covering: have the lowest level of hydrogen (less than 5 ml/100 g of weld metal).

6) Which of the following electrode types would produces the lowest levels of hydrogen?

a. Cellulose coated electrodes sealed in a tin immediately after manyfature
b.  (answer ) Basic coated electrodes when baked correctly immediately prior to use
c. Rutile coated electrodes when dried at 150oC prior to use
d. Heavy rutile coated electrodes when dried at 150oC for 2 hours prior to use
  • Cellulosic electrodes: hydrogen content is 80-90 ml/100 g of weld metal.
  • Rutile electrodes: hydrogen content is 25-30 ml/100 g of weld metal.
  • Basic covering: have the lowest level of hydrogen (less than 5 ml/100 g of weld metal).

7) Basic electrodes are often sold vacuum packed. The reason is:

a.  (answer ) They have been packed at the manufactures at a hydrogen level less than 5ml per 100g of weld metal deposited
b. They are mass produced which makes these electrodes cheap
c. They require less baking time after removal from the packet
d. They are formulated that once open they will pick up no more moisture

weld 12.PNG

8) A general terms which of the following would required the highest preheat if all other factors were the same as per ISO BS EN 1011?

a. ( answer ) MMA weld with cellulosic electrodes
b. MMA weld with rutile electrodes
c. MMA weld with basic electrodes
d. MAG weld with solid wire
  • Cellulosic electrodes: hydrogen content is 80-90 ml/100 g of weld metal.
  • Rutile electrodes: hydrogen content is 25-30 ml/100 g of weld metal.
  • Basic covering: have the lowest level of hydrogen (less than 5 ml/100 g of weld metal).

Cellulosic electrodes have highest Hydrogen content and easy lead to Cold crack. So, it to be required the highest preheat to avoid this cracking type.

Preheat: Preheat, which slows the cooling rate, allows some hydrogen to diffuse away, and generally reduces the hardness, and therefore susceptibility to cracking, of hard, crack-sensitive microstructural regions. The recommended levels of preheat for carbon and carbon manganese steel are detailed in EN 1011-2: 2001 (which incorporates nomograms derived from those in BS 5135: 1984). The preheat level may be as high as 200°C for example, when welding thick section steels with a high carbon equivalent (IIW CE) value.

Alloyed weld metal where preheat levels to avoid HAZ cracking may be insufficient to protect the weld metal. Low hydrogen processes and consumables should be used. Schemes for predicting the preheat requirements to avoid weld metal cracking generally require the weld metal diffusible hydrogen level and the weld metal tensile strength as input.

9) When welding medium carbon steel plates over 90mm in thickness would the basic electrode require any pre-treatment before use?

a.  (answer ) None if they were in a vacuum pack
b. None if they were used in a factory
c. Heat to 500oC for 2 hours if used outside
d. Baked at 150oC for 4 hours prior to use

weld 16

10) When welding medium carbon steel plates over 100mm in thickness would basic electrodes require any pre-treatment before use?

a. None if they were in a vacuum pack opened 8 hours prior to use
b.  ( answer ) None if they were in a sealed vacuum pack prior to use
c. Heat to 500oC for 2 hours if used outside
d. Baked at 150oC for 4 hours prior to use

weld 16.PNG

Pls see next part:

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