Abstract
High-strength low-alloy steels (HSLA) are gaining popularity in structural applications in which weight reduction is of interest, such as heavy duty machinery, bridges, and offshore structures. Since the fatigue behavior of welds appears to be almost independent of the base material and displays little improvement when more resistant steel grades are employed, the use of bolted joints is an alternative joining technique which can lead to an increased fatigue performance of HSLA connections. Manufacturing a hole to allocate the fastener elements is an unavoidable step in bolted elements and it might induce defects and tensile residual stresses that could affect its fatigue behavior. This paper studies and compares several mechanical (punching, drilling, and waterjet-cut) and thermal (plasma and laser-cut) hole-making procedures in HSLA structural plates. A series of 63 uniaxial fatigue tests was completed, covering three HSLA grades produced by thermomechanically controlled process (TMCP) with yield strength ranging from 500 to 960 MPa. Samples were tested at single load level, which was considered representative in HSLA typical applications, according to the input received from end users. The manufactured holes were examined by means of optical and electron microscopy, 3D point measurement, micro hardness tests, X-ray diffraction, and electron backscatter diffraction (EBSD). The results give insight on cutting processes in HSLA and indicate how the fatigue failure is dominated by macro defects rather than by the steel grade. It was shown that the higher yield strength of the HSLA grades did not lead to a higher fatigue life. Best fatigue results were achieved with laser-cut specimens while punched samples withstood the lowest amount of cycles.
Highlights
The field of application for high-strength low-alloy (HSLA) steels ranges from heavy duty equipment to offshore and civil engineering applications [1,2,3,4,5,6]
It was observed that the microstructural differences between HSLA grades produced variations in the hole morphology, such as different differencesdistributions, between HSLA
The higher yield strength of the HSLA grades did not lead to a higher fatigue life
Summary
The field of application for high-strength low-alloy (HSLA) steels ranges from heavy duty equipment to offshore and civil engineering applications [1,2,3,4,5,6]. Metals 2020, 10, 318 they are traditionally produced by quenching and tempering (QT) [7] These HSLA grades have a high hardenability, which may lead to potential brittle fracture and, when used in welds, hydrogen-induced fracture [8]. TMCP allows us to produce a wide range of HSLA grades with diverse microstructures and material properties which are often adopted in civil and mechanical structures. The leaner steel composition results in improved weldability compared to QT HSLA grades. The fatigue performance of welded HSLA, seems to be practically independent from the base material and it displays little improvement when more resistant steel grades are employed compared with milder steel grades [10]. In order to tackle this issue, special post-weld treatments are to be carried out [11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
