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Nuclear power a circuit with duplex stainless steel pipes and Properties

Author: XueZuoZuo
Tutor: WangZhengPin
School: Xi'an University of Technology
Course: Materials Processing Engineering
Keywords: Cast duplex stainless steel Thermal aging Organization Mechanical properties Ductile-brittle transition temperature Fracture mechanism
CLC: TG142.71
Type: Master's thesis
Year: 2010
Downloads: 251
Quote: 3
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Abstract


Cast Duplex (austenitic - ferritic) stainless steel and austenitic due and has the advantages of ferritic steels are widely used to make a nuclear pressurized water reactor primary coolant loop piping, valve and pressure of the cooling pump boundary components. However, the reactor coolant operating temperature (generally ranging from 288-327 ℃) long-term work, cast duplex stainless steel may generate heat aging embrittlement, and with the degree of thermal aging embrittlement increases pressure boundary member will cause critical crack size will decrease, thereby threaten a primary pressure boundary integrity and safe operation of nuclear power plants. Therefore, in order to clearly understand the thermal aging of cast duplex stainless steel mechanism, and in accordance with the normal operation of nuclear power plants aging mechanism to provide guidance to extend the life of nuclear power plants and to improve economic efficiency, it is necessary to cast duplex stainless steel for a long time after thermal aging mechanism research. In this paper, optical microscopy, transmission electron microscopy, scanning electron microscopy, tensile test, Charpy impact test and the ductile-brittle transition temperature measuring methods such as, respectively, of 400 ℃ accelerated thermal aging is not the same length of domestic and French-made Z3CN20-09M Cast Duplex stainless steel structure, room and high temperature mechanical properties, ductile-brittle transition temperature and fracture mechanism was studied, the main results are as follows: two steels are original state austenitic matrix microstructure on the distribution of discontinuous islands ferritic body, the main form of ferrite and banded as lacy and thermal aging duration of ferrite morphology is not significantly affected. Initial heat aging, the austenite matrix and a large number of dislocations, and high-density layer tangles fault, but with the thermal aging time, the dislocations in the matrix significantly reduced degree of entanglement reduced, greatly reduced the number of stacking fault, and dislocations, and grain boundary phase boundary precipitates appeared. Sampling location cast duplex stainless steel on the domestic and high temperature tensile properties at room temperature had no significant effect, while the French-made cast duplex stainless steel and high-temperature tensile strength at room temperature has a significant effect. Thermal aging time on the domestic steel ductility at room temperature and high temperature tensile strength and ductility of significant effects, prolonged thermal aging of the French steel strength at room temperature and high temperature strength and plasticity have a significant effect. Two steels at room temperature and high temperature tensile strain hardening can be divided into three stages, the yield strain hardening stage n1, uniform strain hardening stage before n2, even after strain hardening stage n3, and the strain hardening exponent n1 lt; n2 lt; n3. In the same thermal aging state, impact properties of the steel made in France is slightly better than the domestic steel, and the impact energy of the two steels indicators are as thermal aging time prolonged decline. Sampling location to impact property values ​​not significantly influence; thermal aging time on the domestic and French-made steel Wm, Wi and Wa, and Wt have a significant effect. The same length of time thermal aging dismount domestic steel brittle transition temperature is lower than the domestic steel, and both steel ductile-brittle transition temperature increased with the extension of thermal aging time increased. Two steels at room temperature and high temperature tensile fracture mechanism of porous aggregates, with the thermal aging time, the dimple from large to small, from dark. Original state and after heat aging 100h and 300h after the two steel micro fracture mechanism of shock aggregated porous ductile fracture; fracture after thermal aging 1000h torn edges and visible part of the region along the austenite - ferrite phase boundary fracture characteristics; thermal aging 3000h latter part of the region along the ferrite cleavage river patterns; 10000h after thermal aging cleavage fracture characteristics become more pronounced. This two steels mechanical properties after heat aging and ductile-brittle transition temperature of the test results. After a comprehensive comparison, although domestic steel tensile properties, impact resistance, and are associated with ductile-brittle transition temperature method of steel production there are still some differences, but the performance indicators of domestic steel working conditions are met steel production requirements for France , domestic steel production steel alternative method to use, however, the domestic steel need to be improved in composition.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Special performance of steels > Stainless steel, acid-resistant steel
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