Module 2 Flashcards
Steel,f 2 primary chemicals
Iron + Carbon
as carbon content increase so does (3)____decrease (1)
- strength
- hardness
- brittleness
- decrease weldability
> 2% carbon =
cast iron
Carbon Equivalence (CE) of a steel alloy refers to method of measuring the
weldability of the alloy, based on the chemical composition of the alloy.
Higher concentrations of CARBON and other alloying elements such as manganese, chromium, silicon, molybdenum, vanadium, copper, and nickel tend to increase the ________________and decrease_____________
hardness of the heat affected zone (HAZ) / the weldability of the material.
steel generally contain what range of carbon content?
0.03% to 0.35%
carbon steel generally contain what range of carbon content?
0.15% to 0.35%
Cast iron contain what range of carbon content?
2.1-4%
Pros of killed steel? (3)
- Greater uniformity,
- Minimal voids and inclusions, and
- More corrosive resistant
how to make killed steel
deoxidizing agent is added to remove gases as it is being poured in the mold
what are deoxidizing agent? (2)
1, Aluminum
2. Silicon -larger grain
Aluminum (Al) is a better grain refining element than Silicon (Si) (it makes tighter/smaller grains)
SS contains atleast ___Cr?
11.5%
4 categories of SS? and example of metals?
- Austenitic - 300 SS / Not Magnetic
- Ferritic - found in carbon and low alloy steels and many 400SS
- Martensitic - structure found in some 400 SS. (heat treatment and/or welding followed by rapid cooling can product this structure in CS and low alloy steel.
- duplex - mixed austenitic - ferritic structure.
what happen when steel is produce?
carbon dissolves in the iron.
cast iron flakes pros and cons?
The Good – The flakes provide a cushioning effect for iron when it receives high compression loads
The Bad – The flakes make the material more brittle than steel, and has very poor strength when stretched in tension.
PWHT process?
This is a time and temperature dependent operation, which is followed by slow cooling to avoid
creation of new stresses.
DOES NOT CHANGE grain size
Quenching (6)
➢ Rapid cooling process. ➢ Hardens and strengthens metal. ➢ Causes brittleness. ➢ Causes internal stresses. ➢ Increases chances of cracking and distortion ➢Small grain size
Annealing / Normalizing
➢ Slow cooling process. ➢ Softens and weakens metal. ➢ Causes ductility. ➢ Reduces internal stresses. ➢ Helps prevent cracking and distortion. Annealing --> Large Grain Size Normalizing --> Medium Grain Size
What kind of grain sizes exist
in and around the HAZ?
small size because it is quenching by the base metal and HAZ = harder
What does that do to hardness?
becomes more brittle
Dehydrogenation (2)
applied to steels prior to repair welding of refinery
equipment exposed to services that can cause Hydrogen-Induced Cracking (HIC).
bake-out any residual atomic hydrogen in the steel by heating it to 600°F (316°C) and holding for 1.5 – 2 hours. The procedure is intended
to help avoid delayed hydrogen cracking during or after repair welding
What does the “L” mean in material grades such as 304L and 316L?
low carbon content
what is ionic species
positive charge are called cations.
CE (Carbon Equivalent) equation, what element will have more impact on weldability?
carbon (reduce weldability)
