Question 1

In the Iron-Carbon phase diagram, the temperature at which liquid steel begins to solidify upon cooling is called the:

Accepted Answer

The Liquidus line represents the temperature above which the alloy is completely liquid. Below this line, solidification begins.

Question 2

The region of the base metal that has not been melted but whose mechanical properties or microstructure have been altered by the heat of welding is called the:

Accepted Answer

The Heat Affected Zone (HAZ) is the area of base metal adjacent to the weld that was not melted but was heated high enough to cause microstructural changes.

Question 3

Hydrogen-induced cracking (cold cracking) in carbon steels is most likely to occur in the:

Accepted Answer

Hydrogen cracking typically occurs in the coarse-grained region of the HAZ where the microstructure is hardest and most brittle (martensite).

Question 4

Which of the following elements is the primary hardening agent in steel?

Accepted Answer

Carbon is the most significant alloying element controlling the hardness and strength of steel. Higher carbon content increases hardness but decreases weldability.

Question 5

Preheating is primarily used to:

Accepted Answer

Preheating slows down the cooling rate of the weld and HAZ, allowing hydrogen to diffuse out and preventing the formation of brittle martensite.

Question 6

A steel with a Carbon Equivalent (CE) greater than ___ is generally considered difficult to weld without special precautions.

Accepted Answer

A CE of 0.40 or higher generally indicates a higher risk of cracking and requires preheat and low-hydrogen practices.

Question 7

The crystalline structure of austenite is:

Accepted Answer

Austenite (Gamma iron) has a Face Centered Cubic (FCC) crystal structure, which can hold more carbon in solution than Ferrite.

Question 8

Which type of stainless steel is non-magnetic and cannot be hardened by heat treatment?

Accepted Answer

Austenitic stainless steels (e.g., 300 series) are non-magnetic and hardenable only by cold working, not by heat treatment.

Question 9

The rapid cooling of austenite in carbon steel results in the formation of:

Accepted Answer

Rapid quenching prevents the diffusion of carbon needed to form pearlite, instead shearing the lattice into a hard, brittle structure called Martensite.

Question 10

Sensitization in austenitic stainless steels (carbide precipitation) leads to:

Accepted Answer

Heating stainless steel in the 800°F-1600°F range causes chromium carbides to form at grain boundaries, depleting chromium and reducing corrosion resistance (intergranular corrosion).

Question 11

Low hydrogen electrodes are used to prevent:

Accepted Answer

The primary purpose of low hydrogen electrodes is to minimize hydrogen introduction, reducing the risk of underbead or cold cracking.

Question 12

Lamellar tearing typically occurs in:

Accepted Answer

Lamellar tearing is a separation in the base metal caused by through-thickness strains (shrinkage) pulling apart non-metallic inclusions flattened by rolling.

Question 13

Which element is considered an impurity in steel that can cause 'hot cracking' or shortness?

Accepted Answer

Sulfur forms iron sulfide films at grain boundaries which have a low melting point, causing cracking during solidification (hot cracking). Manganese is added to combine with sulfur (MnS) to prevent this.

Question 14

Stress relief heat treatment is performed:

Accepted Answer

Stress relief is done below the transformation temperature (typically 1100-1200°F for steel) to relieve residual stresses without altering the metallurgical structure.

Question 15

In the designation '6061-T6' aluminum, the 'T6' indicates:

Accepted Answer

T6 indicates the aluminum has been solution heat treated and artificially aged to achieve specific mechanical properties.

Question 16

What effect does a high heat input have on the grain size of the HAZ in carbon steel?

Accepted Answer

High heat input keeps the metal at high temperature longer, promoting grain growth. Coarse grains generally result in lower toughness.

Question 17

The term 'pass' in welding refers to:

Accepted Answer

A pass is a single progression of the welding operation along a joint. A layer may consist of one or more passes.

Question 18

Which test is used to determine the notch toughness of a material?

Accepted Answer

The Charpy V-Notch test measures the energy absorbed by a specimen during fracture, indicating its toughness and transition temperature.

Question 19

Which of the following is NOT a form of heat treatment?

Accepted Answer

Peening is a mechanical working process used to induce compressive stresses, not a thermal heat treatment process.

Question 20

When welding Quenched and Tempered (Q&T) steels (e.g., A514), heat input must be:

Accepted Answer

Q&T steels derive strength from heat treatment. Excessive heat input acts like an over-tempering or annealing cycle, reducing the strength (softening) of the HAZ.

Question 21

The property of a metal that allows it to deform plastically without breaking is:

Accepted Answer

Ductility is the ability of a material to deform plastically (stretch/elongate) under tensile stress before rupture.

Question 22

What is the primary alloying element in '300 Series' stainless steel?

Accepted Answer

300 series stainless (Austenitic) contains Iron, Chromium (typically 18%), and Nickel (typically 8%).

Question 23

Calculate the Carbon Equivalent (CE) for a steel with: C=0.18%, Mn=0.60%, Cr=0.10%, Mo=0.15%, V=0.05%, Ni=0.15%, Cu=0.15%. Using IIW Formula.

Accepted Answer

Formula: CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. CE = 0.18 + (0.60/6) + (0.10+0.15+0.05)/5 + (0.15+0.15)/15. CE = 0.18 + 0.10 + 0.06 + 0.02 = 0.36.

Question 24

During the solidification of a weld, impurities tend to collect:

Accepted Answer

Impurities with lower melting points are pushed ahead of the solidifying front and concentrate at the center of the weld or grain boundaries, causing centerline cracking.

Question 25

The lowest temperature at which a steel exhibits ductile fracture behavior is the:

Accepted Answer

DBTT is the temperature below which the material fracture mode changes from ductile to brittle. Operating below this temp increases risk of catastrophic failure.

Question 26

When welding gray cast iron, the primary difficulty is:

Accepted Answer

Gray cast iron has high carbon. Rapid cooling during welding forms hard, brittle white iron (cementite) and martensite, leading to cracking.

Question 27

A 'Schaeffler Diagram' is used to predict:

Accepted Answer

The Schaeffler diagram uses Nickel and Chromium equivalents to predict the phases (Austenite, Ferrite, Martensite) present in stainless steel welds.

Question 28

Which of the following reduces the cooling rate of a weld?

Accepted Answer

Increasing preheat reduces the temperature gradient between the weld and the base metal, thereby slowing down the cooling rate.

Question 29

Sigma phase embrittlement can occur in stainless steels when held for long periods at:

Accepted Answer

Sigma phase is a hard, brittle intermetallic phase that forms in high-chromium steels exposed to temperatures between 1000°F and 1700°F.

Question 30

The 'Yield Strength' of a material is defined as:

Accepted Answer

Yield strength is the stress level where the material transitions from elastic (recoverable) deformation to plastic (permanent) deformation.

Question 31

Which gas is soluble in molten aluminum but precipitates upon freezing to cause porosity?

Accepted Answer

Hydrogen has high solubility in molten aluminum but very low solubility in solid aluminum. Upon freezing, trapped hydrogen forms gas pores.

Question 32

Ferrite number (FN) is a measurement used to quantify:

Accepted Answer

A small amount of Delta Ferrite (FN 3-10) is desired in austenitic welds to prevent hot cracking. FN is measured magnetically.

Question 33

Weld decay (intergranular corrosion) can be prevented by using:

Accepted Answer

Stabilized grades contain Titanium or Niobium to bind carbon, preventing chromium carbide formation. L-grades have <0.03% carbon.

Question 34

Which property is determined by the 'Percent Elongation' in a tensile test?

Accepted Answer

Percent Elongation measures how much the specimen stretched before breaking, which is a direct measure of ductility.

Question 35

Heat input (J/in) is calculated by:

Accepted Answer

Heat Input formula: H = (Voltage × Amperage × 60) / Travel Speed. This formula calculates the energy per unit length of weld, measured in joules per inch (J/in).

Question 36

The term 'Passivation' regarding stainless steel refers to:

Accepted Answer

Passivation (usually with nitric or citric acid) removes free iron from the surface and enhances the formation of the chromium-oxide layer that resists corrosion.

Question 37

When welding titanium, shielding is required:

Accepted Answer

Titanium is extremely reactive to atmospheric gases at high temperatures. It requires inert gas shielding on the face, root, and a trailing shield for the cooling metal.

Question 38

Martensite is best described as:

Accepted Answer

Martensite is a supersaturated solid solution of carbon in iron, formed by rapid quenching. It is extremely hard but very brittle.

Question 39

Dilution is defined as:

Accepted Answer

Dilution is the percentage of base metal that melts and mixes with the filler metal to form the final weld metal composition.

Question 40

Which factor promotes hydrogen cracking?

Accepted Answer

Hydrogen cracking requires three conditions: Hydrogen, susceptible microstructure, and stress (plus temperature < 400°F).

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