Abstract
Precipitation-hardened, ferrite-pearlite steels are now in the focus of research to create a cost-effective alternative to the commonly use quenched and tempered steels. The main advantage of this type of steel is that they harden already during cooling by forming precipitates and therefore no subsequent heat treatment is required. However, for the use as high strength fasteners they show high stress relaxation compared to quenched and tempered steels, which is a key-property for fasteners. Thus, this work focuses on the influence of residual stresses created during the manufacturing of fasteners on the mechanical properties and relaxation behaviour as well as on the consequence of following heat treatments. To compare the results, the 27MnSiVS6 and the 17MnV7 precipitation-hardened, ferrite-pearlite steel and the 23MnB3 quenched and tempered steel were chosen and examined in different stages of manufacturing. The used methods include metallographic investigations and residual stress profiles on different positions of the investigated materials and at different stages. Additionally tensile tests and room temperature creep tests were performed as low temperature relaxation underlies creep mechanism. The key results show that the residual stresses after annealing feature a decline and that they seem to reduce themselves to a certain level. Furthermore, it shown that the yield strength in the tensile test elevates and the creep strain in the investigated conditions gets significantly lower due to annealing.
Translated title of the contribution | Influence of residual stresses due to the manufacturing process onto the strength and the relaxation behaviour of fasteners |
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Original language | German |
Qualification | Dipl.-Ing. |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 12 Apr 2019 |
Publication status | Published - 2019 |
Bibliographical note
embargoed until 02-04-2024Keywords
- residual stress
- stress Relaxation
- screws
- precipitation-hardened
- ferrite-pearlite steel
- 27MnSiVS6
- 23MnB3