Nickel Alloys and Clad Steels

Question 1

1. What are the two (2) main advantages of using nickel and its alloys?
   a)
   b)

Answer 1

1. a) excellent corrosion resistance, especially at elevated temperatures
   b) a significant increase in equipment service life (a reduction in maintenance costs
   justifies the extra cost of these alloys)

Question 2

2. One reason the use of nickel and nickel alloys is increasing is their:
   a) corrosion and impact resistance.
   b) oxidation and impact resistance.
   c) hardness and impact resistance.
   d) oxidation and corrosion resistance.

Answer 2

2. d) oxidation and corrosion resistance.

Question 3

3. What is the advantage of low carbon nickel?

Answer 3

3. Low carbon nickel is more ductile than straight nickel.

Question 4

4. When alloyed with steel in amounts up to 4%, what effect does nickel have on the mechanical properties of steel?

Answer 4

4. Nickel increases the tensile strength of steel by approximately 41.4 MPa (6000 psi) per percent,

-and it improves low temperature impact properties.

Question 5

5. Which is not considered a nickel-based alloy?
   a) low carbon nickel
   b) Incoloy
   c) Monel
   d) Inconel

Answer 5

5. b) Incoloy

Question 6

6. Nickel, Monel and Inconel can be hardened by heat treatment.
   a) true
   b) false

Answer 6

6. b) false They are solid solution alloys and not heat-treatable.

Question 7

7. List five (5) types of metals that may be used for cryogenic applications.
   a)
   b)
   c)
   d)
   e)

Answer 7

7. a) copper
   b) aluminum
   c) Monel
   d) 300 series (austenitic) stainless steel
   e) 9% nickel steel

Question 8

8. List three (3) factors to consider when selecting filler rods for welding nickel and nickel alloys.
   a)
   b)
   c)

Answer 8

a) Filler metals should match the parent metal composition.
b) Hardenable filler metal is required if welding age-hardenable alloys.
c) Welding of dissimilar metals requires the filler metal to match the more noble metal.

Question 9

9. For welding dissimilar nickel alloys, the filler metal should have:
   a) a lower nickel content than either alloy.
   b) a similar chemical composition to the less noble alloy.
   c) a similar chemical composition to the more noble alloy.
   d) a higher nickel content than either alloy.

Answer 9

9. c) similar chemical composition to the more noble alloy.

Question 10

10. The recommended arc length when using SMAW on most nickel alloys is:
    a) extra long.
    b) long.
    c) normal.
    d) short.

Answer 10

10. d) short.

Question 11

11. What is the most common type of joint used to join nickel and nickel alloys?

Answer 11

11. the butt joint

Question 12

12. When is preheat required for the welding of nickel or nickel alloys?
    a) in all cases prior to welding
    b) to maintain interpass temperatures when specified
    c) when ambient temperatures fall to freezing or below
    d) when ambient temperatures fall below 21o C (70oF)

Answer 12

12. c) when ambient temperatures fall to freezing or below

Question 13

13. What polarity is normally used with SMAW for the welding of nickel and nickel
    alloys?

Answer 13

13. DCEP

Question 14

14. List three (3) causes of excessive spatter when using SMAW on nickel alloys.
    a)
    b)
    c)

Answer 14

14. Any three (3) of the following are correct.
    a) The arc length is too long.
    b) Amperage is excessive.
    c) Polarity is wrong.
    d) Electrodes are damp.
    e) Slag is running under the arc.
    f) Arc blow conditions exist.

Question 15

15. What three (3) elements cause porosity when welding nickel or nickel alloys?
    a)
    b)
    c)

Answer 15

15. a) nitrogen
    b) oxygen
    c) carbon monoxide

Question 16

16. Describe clad materials.

Answer 16

16. A clad steel is a composite material that has been bonded on one or both sides with a
    thin layer of a more expensive high alloy material.

Question 17

17. What are the advantages of using a clad steel instead of a full alloy material?

Answer 17

17. Clad material provides the benefits of the more expensive alloy at a reduced cost.

Question 18

18. The thickness of cladding may range from ______________ % of the total material
    thickness.
    a) 5 to 50
    b) 5 to 60
    c) 10 to 70
    d) 10 to 80

Answer 18

18. a) 5 to 50

Question 19

19. In Table 4, list the types of backing materials that may have cladding applied and
    state the type of service application.
    Types of Materials Service Application
    Table 4

Answer 19

19. Table 5 shows the correct answers.
    Types of Materials Service Application
    Plain carbon steels All-purpose
    Nickel steels Low temperature properties
    Carbon molybdenum steels Elevated temperature service
    Chromium molybdenum steels Elevated temperatures
    Manganese molybdenum steels High tensile
    Table 5

Question 20

20. Why should punching and shearing be done from the clad side?

Answer 20

20. This is to throw the burr on to the steel side.
    -this way, the thickness of the clad side is not compromised.

Question 21

21. List three (3) factors to consider when flame cutting clad steels.
    a)
    b)
    c)

Answer 21

21. Any three (3) of the following are correct.
    a) Many clad steels up to 30% thickness of cladding can be successfully cut
    from the steel side without special equipment.
    b) Greater than 30% may require a flux or powder injection torch.
    c) Flux or powder injection torches allow cutting from the clad or steel side.
    d) Use lower than normal oxygen pressures.
    e) Use a three hose torch to get better control of oxygen pressure.
    f) Use a larger size tip, preferably a six preheat hole tip.
    g) Straight chrome and chromium nickel cladding may require grinding after
    cutting to remove brittle areas that have been affected by carbide
    precipitation.

Question 22

22. Why should low carbon steel filler metals not come in contact with the clad materials
    during welding?

Answer 22

22. Carbon steel contamination results in a hard brittle area with a loss of ductility.

Question 23

23. The recommended sequence for welding a 25.4 mm (1”) thick clad material is to
    weld:
    a) the backing material side first.
    b) the clad material side first.
    c) alternatively between the clad and backing materials.
    d) from the most accessible side.

Answer 23

23. a) the backing material side first.

Question 24

24. What is meant by the term dilution?
    a) increasing the corrosion resistance properties
    b) the mixing of filler metal with the parent metal
    c) the use of shallow penetrating electrodes
    d) the reduction of ductility in the heat-affected zone

Answer 24

24. b) the mixing of filler metal with the parental metal

Question 25

25. What are two (2) advantages of a full alloy weld when joining clad steels?

a)
b)

Answer 25

25.
a) Fit up is simplified.
b) Reduced joint preparation and fit up labour compensates for higher weld metal costs.

Question 26

26. What thickness range is most often welded with the clad alloy filler metal?

Answer 26

26. 1/2” thickness or less