Chapter 6 Introduction to Welding Metallurgy of Steel Flashcards Preview

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Flashcards in Chapter 6 Introduction to Welding Metallurgy of Steel Deck (31)
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1
Q
  1. What are the critical parameters required to calculate the energy input to a weld?

a. Volts, amps and travel speed
b. Volts, amps, preheat and efficiency
c. Volts, amps, travel speed and efficiency.
d. Amps, travel speed, weave width, preheat and efficiency

A

c. Volts, amps, travel speed and efficiency.

2
Q
  1. The energy input is a very important parameter. What significant parts of the weld operation and weld does it relate to?

a. The size and length of the weld and the cooling rate.
b. The size of the weld, the width of the heat affected zone (HAZ) and the steel alloy
c. The width of the heat affected zone (HAZ), the alloy type and the cooling rate.
d. The size of the weld, the width of the heat affected zone (HAZ) and the cooling rate.

A

d. The size of the weld, the width of the heat affected zone (HAZ) and the cooling rate.

3
Q
  1. The cooling rate is very important in welding and the rate of cooling in a given material will depend on a number of factors: which are?

a. The heat input, the electrical conductivity of the material, the material thickness and the temperature of the plates (preheat and interpass)
b. The heat input, the thermal conductivity of the material and the temperature of the plates (preheat and interpass)
c. The heat input, the thermal conductivity of the material, the material thickness and the temperature of the plates (preheat and interpass)
d. The thermal conductivity of the material, the material thickness and the temperature of the plates (preheat and interpass)

A

c. The heat input, the thermal conductivity of the material, the material thickness and the temperature of the plates (preheat and interpass)

4
Q
  1. For a given heat input, there is a point, as a plate gets thicker, where the cooling rate becomes virtually independent of the thickness. Any plate in this range may be considered as?

a. The plate may be considered as “thick”.
b. The plate may be considered as “thin”
c. A plate that requires increased and very high pre-heats
d. The plate may be considered as requiring increased and extensive preheats, elevated interpass temperatures and post weld normalizing.

A

a. The plate may be considered as “thick”.

5
Q
  1. In some steels, a very slow cooling rate may produce a coarse grain structure in the heat affected zone. What may be the effects of such a structure?

a. Such structures can have relatively low toughness
b. Such structures can have relatively high toughness
c. Coarse grain structures in the heat affected zone will significantly reduce the risk of corrosion attack.
d. Such coarse grain Structures will be very resistant to cracking

A

a. Such structures can have relatively low toughness

6
Q
  1. Hydrogen Induced Cold Cracking (HICC) has a peculiar property that is different from other cracking mechanisms. What is this?

a. The cracking is limited to the weld metal
b. The cracking may be delayed
c. The cracking is limited to the HAZ
d. The cracking only occurs above 200 degrees C

A

b. The cracking may be delayed

7
Q
  1. Which of the following situations may assist in the initiation of hydrogen induced cold cracking in susceptible materials?

a. A region of joint misalignment or high/low at the root of a pipe
b. A region of high toughness at the weld fusion line
c. An interpass temperature in excess of 200 deg C
d. Using SMAW electrodes of less than H8 designation

A

a. A region of joint misalignment or high/low at the root of a pipe

8
Q
  1. Which of the following can increase the probability of hydrogen-related cracking in the weld zone of a susceptible material?

a. The use of an interpass temperature above that given in the welding procedure specification or data sheet
b. The use of a preheat above that given in the welding procedure specification or data sheet
c. Preheat below that given in the welding procedure which increases the cooling rate
d. The use of a lower strength electrode than that defined in the weld procedure document

A

c. Preheat below that given in the welding procedure which increases the cooling rate

9
Q
  1. The G-BOP test is a weldability test designed to study:

a. weld metal cracking
b. cracking in the HAZ
c. solidification cracking in the HAZ
d. base metal cracking

A

a. weld metal cracking

10
Q
  1. There are some peculiar features of the cracking mechanism known as hydrogen embrittlement. One of which is?

a. It occurs above a temperature of around 150 °C
b. It occurs only in slow cooling from austenite
c. It is unaffected by local stresses
d. it occurs below the temperature of around 150 °C

A

d. it occurs below the temperature of around 150 °C

11
Q
  1. Some electrode coatings are described as “basic” and these kinds of electrodes will:

a. release nitrous oxide into the arc atmosphere and this lowers the amount of hydrogen gas present
b. contain low amounts of hydrogen and do not need to be kept in holding ovens at
temperature
c. contain high amounts of hydrogen and need to be kept in holding ovens at temperature
d. release carbon dioxide into the arc atmosphere and thus, lower the amount of hydrogen gas present

A

d. release carbon dioxide into the arc atmosphere and thus, lower the amount of hydrogen gas present

12
Q
  1. In a susceptible steel, what steps can be taken to prevent the production of martensite in the weld zone?

a. Ensure the cooling rate is sufficiently fast
b. Ensure the cooling rate is sufficiently slow
c. Use smaller electrode diameters in the fill passes
d. Ensure that heat input is kept to a minimum

A

b. Ensure the cooling rate is sufficiently slow

13
Q
  1. What is the Carbon Equivalent (CE) of a steel?

a. The CE is a summation of the carbon content of the steel and the electrode used to weld it
b. The carbon equivalent is the amount of carbon that is needed in a Steel to prOduce cracking at high temperatures
c. The carbon equivalent is a measure of the steels hardenability
d. The carbon equivalent is a measure of the steels weldability

A

c. The carbon equivalent is a measure of the steels hardenability

14
Q
  1. Lamellar tearing is an infrequent defect due to improvement in steel cleanliness, however it still occurs in steel. What is the most likely place for this to occur?

a. Most likely to occur in thin materials welds where the strains are normal to the plate surface.
b. The most susceptible joints are thick T-Butt and corner joints. Where strains are normal to the plate surface.
c. The most susceptible joints are thick flare groove joints in thin members. Where strains are normal to the plate surface.
d. Most likely to occur in thinner welds where the strains are normal to the plate surface.

A

b. The most susceptible joints are thick T-Butt and corner joints. Where strains are normal to the plate surface.

15
Q
  1. The dilution of a joint will vary according to the welding process, the welding procedure and the joint preparation. Of the following, which would be considered as having the greatest dilution potential?

a. A multipass weld made with SMAW electrodes
b. A low heat input SAW weld
c. An electroslag weld
d. A 10mm single pass fillet weld made by using large diameter FCAW electrodes in the 2F position

A

c. An electroslag weld

16
Q
  1. Local stresses may assist the onset of cracking associated with hydrogen. Where can these local stresses be generated?

a. From quenched and tempered steels only
b. From restraint and stress risers
c. From cooling forces after normalizing heat treatments
d. From using high hydrogen electrodes with preheats above 150 deg C

A

b. From restraint and stress risers

17
Q
  1. There are techniques that can be used to control HICC from a welding procedural viewpoint. One of these approaches can be?

a. Controlling the width of the HAZ to a certain critical number dependent on the number of weld passes
b. Controlling the hardness of the weld metal to a certain critical number e.g. 500 HV
c. Decreasing the heat input to the weld zone to less than 2.0KJ/mm on susceptible materials
d. Controlling the hardness of the weld zone to a certain critical number e.g. 350 HV

A

d. Controlling the hardness of the weld zone to a certain critical number e.g. 350 HV

18
Q
  1. The potential for lamellar tearing in a steel should be recognized at the design stage and susceptible joints avoided. How can this be done?

a. Consideration should be given to the use of premium steel with enhanced properties in the transverse direction
b. Steels with increased sulphur content should be considered
c. Steels that will give a higher total Carbon Equivalent (CE) would be preferable.
d. Consideration should be given to the use of premium steel with enhanced through-thickness properties

A

d. Consideration should be given to the use of premium steel with enhanced through-thickness properties

19
Q
  1. The proportion of total heat energy that enters the plate is known as the efficiency and it varies with the welding process used. Which of the following arc welding processes is the least efficient?

a. Gas tungsten arc welding
b. Submerged arc welding
c. Shielded metal arc welding
d. Self-shielded flux-cored arc welding

A

a. Gas tungsten arc welding

20
Q
  1. Creep strength in the wrought ferritic steels can be achieved by the following kind of metallurgical engineering?

a. By heat treatments that effectively reduce the grain size
b. By alloying with elements that will provide enhanced strength at high temperatures such as chromium and molybdenum
c. By alloying with elements that will produce microvoids at the grain boundaries, such as nitrogen
d. By solid solution hardening and over aging

A

b. By alloying with elements that will provide enhanced strength at high temperatures such as chromium and molybdenum

21
Q
  1. Chrome-moly steels are used for high-temperature service. As the alloy content increases in these materials what can become a problem?

a. Increasing alloy content can lead to low toughness which is a problem for high-temperature alloys
b. The ductility generally increases thus decreasing strength
c. Hardenability will increase and HICC can be a factor
d. Hardenability will increase and hot cracking can be a factor

A

c. Hardenability will increase and HICC can be a factor

22
Q
  1. What is a possible source of hydrogen that could be present in a weld zone?

a. The breakdown of water and organic material in the weld area
b. From carbon-bearing shielding gases
c. The only possible source is the non-low hydrogen electrode
d. The only possible source is hydrogen from shielding gases

A

a. The breakdown of water and organic material in the weld area

23
Q
  1. Structural steels may be split into zones that indicate the techniques that may be used to resist the onset of HICC. What is a Zone III steel?

a. A steel where hydrogen control must be used to prevent the onset of HICC
b. A steel where hardness control must be used to prevent the onset of HICC
c. A steel where HICC is not expected to occur
d. A steel where HICC will always occur and, therefore, joining must be by achieved by bolting.

A

a. A steel where hydrogen control must be used to prevent the onset of HICC

24
Q
  1. One test to evaluate cracking is the Tekken test. In this test how do researchers promote cracking in the materials HAZ?

a. By using a sloping Y groove preparation
b. By using a straight Y groove preparation
C. By using several tack welds loaded with hydrogen to seed the cracks
d. By using a jig that contains refrigerated water.

A

a. By using a sloping Y groove preparation

25
Q
  1. What can be said about the data derived from experimental cracking tests of weld zones?

a. Cracking tests are very Specific and model most, if not all, production conditions.
b. Results from a cracking test is mainly for use by researchers trying to predict the microstructures that will occur in HAZ’s
c. Results from a cracking test are mainly comparative and should not be used directly as they only simulate laboratory conditions.
d. Some tests, such as the G-BOP test, have been known to give erroneous results for HAZ studies.

A

c. Results from a cracking test are mainly comparative and should not be used directly as they only simulate laboratory conditions.

26
Q
  1. Where high toughness is required in submerged arc welds, fluxes that provide a certain property must be selected. What is this property?

a. Basic fluxes that provide low oxygen should be specified.
b. Basic fluxes that provide high oxygen should be specified.
c. Acidic fluxes hat provide low oxygen should be specified.
d. Fluxes hat provide high Silicon should be specified.

A

a. Basic fluxes that provide low oxygen should be specified.

27
Q
  1. On thicker plates, where non-hydrogen controlled processes are being used for joining, what do codes such as CSA W 59 advise?

a. That any preheat must be applied 35mm either side of the weld
b. Preheat must be raised above that which would be used for hydrogen-controlled processes
c. Any preheat must be applied by soaking in an oven to ensure reduced temperature gradients
d. Only non-fluxed welding processes can be used

A

b. Preheat must be raised above that which would be used for hydrogen-controlled processes

28
Q
  1. For stress relieved applications it is sometimes necessary to use an option to maintain the same yield and tensile strength as that in the original weldment. What is this option?

a. Use alloyed chromium bearing electrodes
b. Use alloyed molybdenum-bearing electrodes
C. Use additional hold times during the heat treatment
d. Use both an increased temperature and increased hold time for heat treatment

A

b. Use alloyed molybdenum-bearing electrodes

29
Q
  1. In the heat-affected zone, regions that are close to the fusion boundary can experience temperatures sufficiently high that growth of the austenite grains occurs. What governs this growth?

a. The extent to which they grow depends on the welding process,
b. The extent to which they grow depends on the energy input.
c. Their growth depends on the steel alloy content and the welding process.
d. Their growth depends on the thickness of the steel, the welding process, and the alloy content

A

b. The extent to which they grow depends on the energy input.

30
Q
  1. What is dilution?

a. Melting of the welding rod
b. Change in the chemical composition of the weld metal due to admixture of filler metal and base metal
c. How fast the filler metal melt
d. Melting of the base metal only

A

b. Change in the chemical composition of the weld metal due to admixture of filler metal and base metal

31
Q

What is the amount of carbon in reg steel

A

.15%-.30% = structural steel forging

Low temp is .03%