Heat Treatments

Question 1

Softens a metal by increasing its ductility, while reducing its strength and hardness. It is accomplished by raising the metals temperature to its austenitic range for a period of time, then cooling it slowly in the furnace. Usually the furnace is simply turned off, allowing it to cool over a long period of time. Produces Pearlite.

Answer 1

Annealing

Question 2

Similar to annealing, but doesn’t soften the metal as much. The method involves raising the metals temperature to austenitic range and holding it for a period of time. The difference though is that it is then taken out of the furnace and cooled at air temperature; this has a faster cooling rate than the annealing, which is why it doesn’t create metals that are as soft. Produces Bainite.

Answer 2

Normalizing

Question 3

Rather than softening the metal, it is intended to harden the metal. The metal temperature is brought to an austenitic range, then rapidly cooled, by being quenched in water, oil, or another medium. This produces a _______ structure with high strength and hardness, but low ductility. Produces Martensite.

Answer 3

Quenching

Question 4

Used in tandem with quenching. After the quenching process occurs, the steel can be tempered by reheating it to an austenitic temperature, holding it, then cooling it at a rate that produces the desirable level of ductility without sacrificing much of the strength that was induced by quenching.

Answer 4

Tempering

Question 5

Stresses that remain in the weldment immediately after welding, but aren’t strong enough to cause distortion. Relieved by either thermal stress relief, vibratory stress relief, or peening.

Answer 5

Residual stresses

Question 6

When austenite is cooled very rapidly, it produces ________, which has very high hardness but low ductility and toughness.

Answer 6

Martensite

Question 7

When austenite cools rapidly, it produces ________, which has high strength, low ductility.

Answer 7

Bainite 

Question 8

Considered a mechanical stress relief method, peening uses a hammer to pound on the weld face of different weld passes in a multi-pass weld. The hammer action the deforms and spreads out the weld face surface, allowing the residual stresses to spread and reduce. 

Answer 8

Peening

Question 9

The welded part is gradually and uniformly heated to a temperature just below its austenitic transformation temperature 1333 Fahrenheit. As the temperature increases, the metal strength decreases, which allows the residual stress to relax. 

Answer 9

Thermal stress relief

Question 10

This method sends sound waves into the welded part, either during or after welding, or both. The sound waves prevent and remove stress buildup. 

Answer 10

Vibratory stress relief

Question 11

When plain carbon steel is heated to approximately 1333°F, a coarse-grained microstructure called austenite is formed. At approximately 2770°F austenite begins to melt and become a liquid. 

Answer 11

Austenite

Question 12

Oh, when austenite cools slowly, it will produce _______, which is generally soft and ductile. 

Answer 12

Pearlite

Question 13

Specifies how much a metal will expand for a given increase in temperature.

Answer 13

Coefficient of thermal expansion

Question 14

The higher the temp, the more atoms of an element can be mixed into an alloy. The alloy is heated above its melting point, then quenched below its melting point. Used to increase yield strength of malleable materials.

Answer 14

Precipitation Hardening

Question 15

Reheating an alloy to a relatively low temperature and allowing additional atoms of carbon and nitrogen to be absorbed into its surface.

Answer 15

Case hardening