Class Test No 2 Material

Question 1

Explain the term t8/5

Answer 1

*It is the temperature / time cycle of an individual weld run and the time taken during cooling for a weld run and its heat affected zone to pass through the temperature from 800°C to 500°C

Question 2

Explain why TMCP steels have improved weld ability than traditional hot rolled steels? (2)

Answer 2

TMCP steels have a lower carbon equivalent than hot rolled steels.

Question 3

List three applications for TMCP steel (3)

Answer 3

a.) Truck chassis
b.) Cranes
c.) Earth moving equipment

Question 4

what effect does carbon have on the strength and weld ability of a material?

Answer 4

Carbon increases the strength but reduces the weldability of a material

Question 5

List the types of PWHT that are normally applied to low alloy steels

Answer 5

Tempering
Annealing
Normalising

Question 6

explain why austenitic weld metals may not be suitable for welding low alloy steels (6)

Answer 6

*Austenitic weld metals are not satisfactory when welds will be subjected to cyclic temp. in service,
*or to temp. that will result in carbon migration in the base metal or sigma formation within the weld metal.
* The difference in coefficient of thermal expansion between the austenitic weld metal and Ferritic chromium-molybdenum base materials should not be overlooked.

Question 7

Name two weldability problems when welding low alloy steels.

Answer 7

a.) Cold cracking
b.) Carbide precipitation

Question 8

High strength low alloy steels require welding to the highest possible standards, explain in detail the steps that should be employed (followed) in order to ensure that the highest quality has been attained for this material, The welding process is SMAW (20)

Answer 8

a) before welding commences proper documentation will have to be in place such as welding procedures etc, also qualified personnel is an important issue such as
qualified welders, ndt technicians etc.
B) preheat is beneficial in controlling the cooling rate of the weld, which in turn controls the hardness of the haz. Preheat also tends to reduce stresses and diffuses hydrogen from the weld metal and haz.
C) low hydrogen electrodes should be used for welding these materials to avoid hydrogen cracking and the correct procedures should be employed such as the use of hot boxes etc to ensure that these electrodes contain no moisture.
D) attention to the guidelines in the welding procedure must be followed to ensure quality is being maintained during welding.
E) pwht is seldom used for the welding of these materials, however if pwht is required the guidelines in the wps must be followed.

Question 9

list 3 commonly used cladding materials?

Answer 9

1. stainless steel alloy
2. nickel or nickel alloy
3. copper or copper alloy

Question 10

What precautions should be taken when using austenitic weld metal as the cladding material?

Answer 10

Austenitic weld metal is subjected to 500 – 850°C, sensitizations when heated stress relieving temperatures ranges should also be considered.