A comparison between ultra-high-strength and conventional high-strength fastener steels

Mechanical properties at elevated temperature and microstructural mechanisms

Journal article (2016)

Authors

C.E.I.C. Ohlund OLD Metals Processing, Microstructures and Properties , Nedschroef Techno Center
M. Lukovic Steel & Composite Structures - CEG
J Weidow Chalmers University of Technology
M Thuvander Chalmers University of Technology
S.E. Offerman (OLD) MSE-1
Research Group
OLD Metals Processing, Microstructures and Properties
Copyright: © 2016 C.E.I.C. Ohlund, M. Lukovic, J Weidow, M Thuvander, S.E. Offerman
DOI: https://doi.org/10.2355/isijinternational.ISIJINT-2016-120
More Info
expand_more

Published Date

2016

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Research Group

OLD Metals Processing, Microstructures and Properties

Abstract

A comparison is made between the mechanical properties of the ultra-high-strength steel KNDS4 of fastener grade 14.9 and of conventional, high-strength steels 34Cr4 of fastener grade 12.9 and 33B2 of grade 10.9. The results show that the ratio of the yield strength at elevated temperatures to the yield strength at room temperature is higher for the ultra-high-strength steel than for both conventional highstrength steels, especially at 500°C. Moreover, the results show a trend in which the nano-indentation creep rate is lower as the strength of the steels is higher. The improved mechanical properties of the KNDS4 steel compared to the conventional high-strength steels are related to the smaller size of the alloy carbides in the KNDS4 steel. Furthermore, the effect of an alternative (industrial) heat-treatment on the evolution of the microstructure and hardness of the KNDS4 steel was investigated. Changing the industrial heat treatment can increase the hardness of KNDS4 by about 8%, since more alloy carbides can nucleate and grow. However, the standard industrial heat treatment results in a refinement of the martensite microstructure (grain size), which might be more beneficial for the toughness of the steel. Independent of the heat treatment, the mechanical performance of KNDS4 fasteners at elevated temperature and the low nano-indentation creep rates are two strong indicators that fasteners made from KNDS4 steel might be used at higher service temperatures than traditional high strength fasteners.

Files

Article_4_ISIJ_Final_version.p... (pdf)
(pdf | 1.55 Mb)
Unknown license

Download not available

8_Ohlund_2016_ISIJINT_.pdf
(pdf | 0.795 Mb)
Unknown license