CSWIP 3.1 QUESTION AND ANSWER SERIES
1) During post weld heat treatment what is the sequence for the PWHT chart?
|a.||Restricted heating rate, soak time, unrestricted cooling rate|
|b. ( answer )||Unrestricted heating rate, restricted heating rate, soak time, restricted cooling rate, unrestricted cooling rate|
|c.||Unrestricted heating rate, soak time, restricted cooling rate|
|d.||Restricted heating rate, unrestricted heating rate, soak time, unrestricted cooling rate, restricted cooling rate|
Variables for heat treatment process must be carefully controlled
- Provide adequate support (low YS at high temperature!)
- Control heating rate to avoid uneven thermal expansions
- Control soak time to equalise temperatures
- Control temperature gradients – NO direct flame impingement!
- Control furnace atmosphere to reduce scaling
- Control cooling rate to avoid brittle structure formation
Below 427 degree, it is no need restricted heating.
2) After PWHT, it has been noticed that a repair must be carried out. How should this be done?
|a.||With the minimum amount of heat input|
|b. ( answer )||Welded, checked and PWHT again|
|c.||Defect removed via non-thermal process then checked|
|d.||Welded and allowed to cool in air|
The PWHT depends on the thickness of the repair. If the thickness of the repair welding is equal to or higher of the minimum base metal thickness which requires PWHT then you shall perform PWHT after completion of the repair.
3) Preheating may not be necessary during welding in which of the following material?
|a.||Welding of cast iron|
|b.||Welding of low alloy steels|
|c.||Welding of martensitic stainless steels|
|d. (answer)||Welding of austenitic stainless steels|
4) The main problem with solution treatment of stainless steels is that:
|a.||Controlling the rate of the temperature use|
|b.||Controlling the cooling rate|
|c.||The length of the soak period|
|d. ( answer )||High risk of distortion|
- High coefficient of expansion – more distortion during welding
5) When would you measure the interpass temperature?
|a. ( answer )||The highest temperature recorded in the weld joint immediately prior to depositing the next runs|
|b.||Immediately prior to commencing the first pass|
|c.||When the welding is complete|
|d.||Only required if the heat input is lower than that specified in WPS|
6) If pre heating is decreased, which of the following would be most greatly affected?
|b. ( answer )||Hardness|
Pre-heat treatments: are used to increase weldability, by reducing sudden reduction of temperature, and control expansion and contraction forces during welding
- Preheat controls the formation of un-desirable microstructures that are produced from rapid cooling of certain types of steels. Martensite is an undesirable grain structure very hard and brittle it is produced by rapid cooling form the austenite region.
7) Assuming the same materials and welding procedure were used, which of the following is the highest preheat?
|a.||Butt weld in 35mm plate|
|b.||Cruciform joint in 25mm plate|
|c.||Tee joint butt welded in 30mm plate|
|d.||Tee joint fillet welded in 20mm plate|
8) Why is it sometimes necessary to preheat the base material before welding?
|a.||Remove oil and grease|
|b.||Remove moisture from the inside of the material|
|c. ( answer )||Prevent the possible risk of cracking|
|d.||Not required if using cellulosic electrodes, as these will provide enough heat|
9) Ultraviolet and infrared radiation, produced during arc welding, may:
|a.||Make arc striking easier|
|b.||Be used for weld testing|
|c.||Increase the welding speed|
|d. (answer)||Cause skin burns|
10) Who is responsible for site safety?
|c.||An approved inspector|
11) Is it permissible to allow welding to be carried out in bad weather?
|b. ( answer )||Yes as long as there is adequare protection from the poor weather conditions|
|c.||Yes as long as basic low hydrogen welding electrodes are used|
|d.||Yes as long as the welder is prepared to work in the rain|
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