Six materials, copper and copper alloys, have been subjected to long-term creep tests (30 000 h) per DIN 50 118 at a range of 100 to 250°C, except for aluminum bronze which was tested from 150 to 300°C. The following annealed materials were tested: SF-Cu (DIN 1787)—equivalent to C 12200, Phosphorus Deoxidized Copper, high residual Phosphorus (Cu-DHP); CuZn39Pb0.5 (DIN 17 660)—equivalent to C 33500, low-leaded brass; CuZn20Al2 (DIN 17 660)—equivalent to C 68700, aluminum-brass, arsenical; CuZn28Sn1 (DIN 17 660)—equivalent to C 44300, Admiralty brass, arsenical; CuZn38SnAl (DIN 17 660), improved Muntz-metal, 60%, not standardized in the United States; and CuAl10Ni5Fe4 (DIN 17 665)—similar to C 62730 or C 63000, nickel-aluminum-bronze. The test conditions and the metallurgical history of the materials are described. The minimum value of the 1% creep strain and the average value of creep strength, both temperature and duration dependent, as well as the stress for minimum creep rates of 1% for a given time are also shown. The design criteria for pressure vessels are discussed.
Die Härte von kupferlegiertem Walzblei für den Chemie‐Apparatebau wird durch weitere Legierungszusätze erhöht. Der im Hinblick auf Verarbeitbarkeit, Feinkörnigkeit, Gefügestabilität und Korrosionsbeständigkeit optimale Blei‐Feinkornwerkstoff PbCu0,042Sn0,05Pd0,03Se0,02 liegt in seiner Härte zwischen derjenigen von Kupferfeinblei DIN 1719 und Hartblei mit 4% Sb. Streckgrenze (0,2%‐Dehngrenze) und Zugfestigkeit der untersuchten Walzblei‐Werkstoffe nehmen innerhalb einer gewissen Streubreite linear mit der Härte zu. Das gilt auch für die Wechselfestigkeit. Die Kriechfestigkeit (1% Zeitdehngrenze und Zeitstandfestigkeit) nimmt gleichfalls mit der Härte zu, wobei sich diese Abhängigkeit aber mit zunehmender Prüftemperatur abschwächt und bei 110deg;C nur noch gering ist. Die durch geringe Zusätze von Silber (bis 0,01%) erzielbaren Verbesserungen der mechanischen Eigenschaften von kupferlegiertem Blei werden ausführlich diskutiert.
Five essential requirements for gas turbine materials exposed to high temperatures are discussed:
- High resistance to oxidation and high temperature corrosion
- High creep strength especially under condition of thermal stress
- High fatigue strength under conditions of vibrational and thermal stress
- Good workability since complicated deformation and machining processes are often necessary
- Good weldability
It is not always possible to make all these requirements totally compatible. This is because certain requirements have to be emphasized for reasons of application. In most cases compromises will have to be made in regard to workability.
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