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This chapter explores the behavior of metals at high and low temperatures, including creep, stress-rupture, oxidation resistance, and impact behavior. It also discusses the role of alloying elements and the importance of temperature in determining the mechanical properties of metals.
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Chapter 30 Effect of Temperature on Metals Metals at High Temperature • Metalsat Low Temperature
The creep curve consists of three principal regions or stages.
The creep rate during secondary creep is measured and plotted against the applied stress and usually exhibits a straight line.
Stress-rupture curves are plots of the stress and rupture time at various test temperatures.
Chrome-moly steels are widely used for elevated temperature applications up to 540°C (1000°F).
All chrome-moly steels require preheating and postheatingwhen welded.
Austenitic stainless steels exhibit the best creep strength of all stainless steels.
Chromium is the most important alloying element for increasing oxidation resistance of steels and stainless steels.
Chrome-moly steels have greater resistance to hydrogen attack than carbon steels.
In high-temperature corrosion testing, coupons are sectioned and metallographically examined to determine the depth of the attack.
As the temperature is decreased below room temperature, the yield strengths of all metals and alloys increase, and with few exceptions, so does the ultimate tensile strength.
The NDT temperature is the temperature at which the impact behavior of a metal changes from ductile to brittle in the presence of a stress raiser.
Carbon content should be kept as low as possible and consistent with strength requirements.
Increases in nickel content significantly lower the NDT temperature.
Austenitic stainless steels remain tough at the boiling points of many gases.