Chapter Seven Quiz Flashcards
In the selection of stainless steels, which type would be preferable for use in applications needing good corrosion resistance together with wear resistance?
Martensitic with high carbon.
Which of the following groups of alloying elements drive the formation of the austenite
phase in stainless steels?
Nickel, manganese, and nitrogen.
When joining a carbon steel plate (ferritic BCC) to an austenitic stainless steel (FCC), what is the accepted practice (Select all that apply)?
Butter the carbon steel side with a 309 filler using a welding process that gives acceptable dilution and then complete the joint with conventional stainless steel electrodes.
When comparing a duplex stainless steel to a ferritic stainless steel, in what areas would the duplex have improved overall properties?
Superior toughness and corrosion resistance.
Which element in a stainless steel alloy is mostly responsible for the materials resistance to high temperature oxidation?
Chromium
Once pitting corrosion is initiated what is the relationship between the pit and its growth rate in the stainless steel in question?
Majority of gases the growth rate of the pit increases as the depth increases.
Which two regions of a PH stainless steel weld zone can exhibit a reduction in strength after completion of welding?
Base metal side of the fusion boundary(weld interface) and the overaged region in the HAZ where precipitates coarsen.
Austenitic stainless steels can be stabilized by adding amounts of certain elements to the steel chemistry, what are these elements?
Add small amounts of strong carbide formers.
When austenitic stainless steels are used in equipment that will operate in the range 600-750°C, what type of stainless steel should be selected?
Stabilized 321 or 347 types.
Martensitic stainless steels are very hard which is why they find use in situations that require wear and erosion properties. What drives the hardness of these stainless steels?
Relatively high carbon content.
Match the type of steel to its common uses or properties.
Non magnetic steels and hinders welding of alloy steels by casing arc blow - Austenitic SS
Steels suffer excessive grain growth during welding and result have lower toughness - Ferrite SS
Steels are used for cutlery, hydraulics, where good corrosion and wear resistance is needed - martensitic SS
Steels developed to aim of combining mechanical corrosion resistance properties of austenite and delta ferrite phases - Duplex SS
What are the main factors that can cause the onset of stress corrosion cracking (SCC) in austenitic stainless steels?
Tensile stress and the presence of chlorine or other halogen ions.
Creep strength is the ability of materials to resist distortion during long-term exposure to loads at high temperature. Which of the following stainless steels has the best “creep strength”?
Austenitic 304H grade
When using the gas metal arc welding processes to weld stainless steels, small percentages of carbon dioxide in the shielding gas can lead to:
Carbon pick up in the weld deposit.
The higher electrical resistivity of austenitic stainless steels can result in what advantage over carbon steels when using the GMAW process?
Higher wire feed speeds leading to better deposition rates.
When selecting a welding consumable for joining a martensitic stainless steel, what type of consumable would be best if matching strength and hardness is not a factor?
Austenitic stainless steel electrode.
Match the type of diagram to its common uses
This diagram is for predicting ferrite content (ferrite number) from composition.
Delong diagram
1
This diagram is considered to be the most accurate constitution diagram for the prediction of ferrite content of austenitic and duplex stainless steel weld metals from chemical composition.
WRC diagram
3
This diagram is for predicting weld metal structure based on weld metal composition
Schaeffler Diagram
In order to reduce the probability of solidification cracking in FCC austenitic stainless steels there are a number of approaches. Which of the following is correct?
Arrange the weld zone to be put in compression and use carbon steel filler that solidifies as BCC ferrite first.
When welding austenitic stainless steels, which method is typically recommended to avoid solidification cracking in the weld metal?
Austenitic consumables that produce a small but controlled quantity of delta ferrite in the solidified weld metal.
If martensitic stainless steels are joined using FCC austenitic electrodes, certain
precautions may still need to be taken. Which of the following would be a correct approach?
Use the prescribed pre heat so as to reduce the probability of cracking in the HAZ.
There is a phase in certain stainless steels that can cause serious embrittlement. What is this phase and how does it form?
Formation of sigma phase after prolonged heating can cause embrittlement.
What elements can be added to precipitation hardening (PH) stainless steel in order to produce the small precipitates necessary for hardening?
Aluminum, copper, and niobium.
When joining ferritic stainless steels with matching electrodes, the welding procedure must be carefully controlled to avoid the following (Select all that apply):
Entrapment of small interstitials such as oxygen and nitrogen which can cause severe embrittlement. Entrapment of slag when using the FCAW process can cause severe corrosion in specific environments.
What property does an FCC austenitic stainless steel have that will make the size of the weld pool larger for the same heat input when compared with welding a BCC carbon steel?
The melting temperature and thermal conductivity of the FCC austenitic stainless is less than that of the BCC carbon steel.
