GTAW on Stainless Steel

Question 1

How much distortion due to thermal expansion occurs during the welding of stainless steel compared to mild steel?
a) 50% more
b) the same as mild steel
c) two times less
d) two times more

Answer 1

a) 50% more

Question 2

How does the thermal conductivity rate of stainless steel compare to that of mild steel?

Answer 2

is about half that of mild steel.

Question 3

The element in stainless steel that oxidizes readily is:
a) silicon.
b) nickel.
c) chromium.
d) molybdenum.

Answer 3

c) chromium.

Question 4

Which common work site method is used to identify a 300 series stainless steel?

Answer 4

A magnet is used to aid in the identification of a 300 series stainless steel.

Question 5

What are the major considerations when selecting a stainless steel filler metal?

Answer 5

The filler metal must match the parent metal’s chemical composition, mechanical properties and physical properties.

Question 6

What is an autogenous weld?

Answer 6

An autogenous weld is formed by melting the joined ends without added filler.

Question 7

The AWS specifications related to stainless steel filler metals state the:
a) chemical composition requirements for the classification.
b) corrosion resistance requirements for the classification.
c) theoretical mechanical properties requirements.
d) welder’s required qualifications.

Answer 7

a) chemical composition requirements for the classification.

Question 8

Describe an ER347 filler metal.
a) E =
b) R =
c) 347 =

Answer 8

a) E = electrode
b) R = rod
c) 347 = grade of stainless steel

Question 9

Name an advantage of using flux covered GTAW filler rods.

Answer 9

Flux covered filler rods provide fluxing on the root side of an open gap and prevent atmospheric contamination of the weld area.

Question 10

How is a 300 series stainless steel hardened?

Answer 10

A 300 series stainless steel is hardened by cold working only.

Question 11

List three (3) ways to reduce intergranular corrosion (carbide precipitation) of a weld
on a 300 series stainless steel.
a)
b)
c)

Answer 11

Any three (3) of the following are correct.
a) Reduce welding current.
b) Increase travel speeds.
c) Shorten arc for a more concentrated arc.
d) Do not use preheat.
e) Reduce interpass temperatures.
f) Use stringer beads.
g) Use stabilized stainless base metals and filler metals.
h) Use low carbon stainless base metals and filler metals.

Question 12

Current settings for GTAW of stainless steel are generally current settings used for aluminum.
a) slightly higher than
b) lower than
c) the same as
d) two times higher than

Answer 12

b) lower than

Question 13

Which of the following metals can be welded satisfactorily with DCEN and high frequency set at start only?
a) zinc die-cast
b) stainless steel
c) aluminum
d) magnesium

Answer 13

b) stainless steel

Question 14

Which other series of stainless steel uses welding procedures similar to those for the 300 series?
a) 200
b) 300
c) 400
d) 500

Answer 14

a) 200

Question 15

Is preheat generally required for 300 series stainless steels?
a) yes
b) no

Answer 15

b) no. Austenitic stainless steels seldom require preheat unless they are very cold or have moisture on them.

Question 16

Draw a welding symbol to indicate a fillet weld to be completed using GTAW on
both sides of a lap joint.

Answer 16

Figure 21 shows the correct weld symbol.
Figure 21

Question 17

Grinding discs and files used for the preparation of stainless steels:
a) are specially designed for stainless steel only.
b) are not to be used interchangeably with other steels.
c) must meet CSA Standard W178.2 specifications.
d) should have a low carbon content.

Answer 17

b) are not to be used interchangeably with other steels.

Question 18

Wire wheels or brushes used for the preparation of stainless steel should be made of:
a) stainless steel.
b) low carbon steel.
c) high carbon steel.
d) non-ferrous metals.

Answer 18

a) stainless steel.

Question 19

Externally applied fluxes are used to weld stainless steel:
a) to replace the loss of alloying elements.
b) to prevent atmospheric contamination of the opposite side of the joint.
c) in place of CO2 shielding gas.
d) but are highly corrosive and must be removed after welding.

Answer 19

b) to prevent atmospheric contamination of the opposite side of the joint.

Question 20

Externally applied fluxes lose their effectiveness when:
a) high currents are used.
b) a back-purge gas is used.
c) more than one pass is required.
d) a high frequency start is required.

Answer 20

c) more than one pass is required

Question 21

The sugaring effect that sometimes appears on stainless steel welds indicates:
a) a stabilized base metal.
b) oxidation due to lack of shielding.
c) that carbide precipitation has occurred.
d) that an incorrect grade of filler metal was used.

Answer 21

b) oxidation due to lack of shielding.

Question 22

What technique can reduce the possibility of distortion on stainless steels?

Answer 22

Use extra tacks that are evenly spaced as little as 50 mm (2”) apart.

Question 23

What is the recommended end preparation for the electrode when welding stainless steel with GTAW?

Answer 23

conical, 2 to 6 diameters of the electrode

Question 24

For welding stainless steel, a ______________ gas nozzle is used than would be used
for aluminum.
a) larger
b) smaller
c) thinner
d) thicker

Answer 24

b) smaller

Question 25

The appearance of a satisfactory weld on stainless steel is indicated by what colour?
a) navy blue
b) salmon pink
c) charcoal grey
d) black

Answer 25

b) salmon pink