Fatigue strength of TIG-dressed ultra-high-strength steel fillet weld joints at high stress ratio

Skriko, Tuomas; Ghafouri, Mehran; Björk, Timo

doi:10.1016/j.ijfatigue.2016.09.018

Cited by 44 publications

(34 citation statements)

References 13 publications

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“…FSP can be used as a new technique to increase fatigue strength of the fusion-welded joints, and provide advantages different from grinding [14] [15] [16] and remelting [17] [18] [19] for the weld geometry modification or peening [20] [21] [22] and post-weld heat treatment [23] for decreasing tensile residual stress. However, use of the FSP technique has been limited to a few light metal alloy welds so far.…”

Section: Introductionmentioning

confidence: 99%

Effects of Microstructural Modification Using Friction Stir Processing on Fatigue Strength of Butt-Welded Joints for High-Strength Steels

Yamamoto¹,

Ito²

2018

MSA

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Friction stir processing (FSP) is an effective surface-microstructure modification technique using a rotational tool to refine and homogenize microstructure of metallic materials. In this study, FSP was conducted on the surface of the heat-affected zone (HAZ), which is a region exhibiting degraded mechanical properties and shown to have microstructural changes, of butt-welded joints for two high-strength steels with tensile strength grades of 490 MPa and 780 MPa (hereafter HT490 and HT780, respectively). Inhomogeneous mixing of materials derived from weld metals and base metals (BMs) in a stir zone (SZ) produced inhomogeneous distribution of elements and microstructure depending on the set of the advancing side and retreating side in the SZs. The welded joints with FSP for HT490 exhibited higher hardness than that of the BM through whole of the SZ surface (fine polygonal ferrite grains and bainite structure with laths at the Mn-rich and Mn-poor regions, respectively). On the other hand, those for HT780 exhibited the minimum hardness value similar to that of the BM at the SZ surface (a few polygonal ferrite grains in the matrix of martensite laths). Fatigue strength increased by about 35 MPa and 15 MPa in stress amplitude at 10 7 cycles as fatigue limit due to FSP. Fatigue failure occurred at the BM and the SZ, respectively, in the welded joints modified by FSP for HT490 and HT780, in comparison with the HAZs in the as-welded joints for both grade steels. The difference in fatigue strength increase due to FSP and failure location between the welded joints for HT490 and HT780 can be attributed to the topmost SZ microstructures and their distribution.

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Section: Introductionmentioning

confidence: 99%

Effects of Microstructural Modification Using Friction Stir Processing on Fatigue Strength of Butt-Welded Joints for High-Strength Steels

Yamamoto¹,

Ito²

2018

MSA

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“…Fatigue strength of arc-welded joints is commonly said to be lower than that of the base metal, because of stress concentration, tensile residual stress, and deterioration of the mechanical properties due to microstructural change at the weld toe. Various post-weld treatments have been proposed to increase fatigue strength of the welds, and are generally divided into two groups of residual stress modi cation, those of peening [1][2][3][4] and post-weld heat treatment [5,6], and weld geometry modi cation such as grinding [7][8][9] and remelting [10][11][12]. Residual stress modi cation is more effective than weld geometry modi cation under low applied stress amplitude, but seems not effective under high applied stress amplitude, because of residual stress relaxation during fatigue [13].…”

Section: Introductionmentioning

confidence: 99%

Fatigue Strength Improvement Due to Alloying Steel Weld Toes With WC-Tool Constituent Elements Through Friction Stir Processing

Yamamoto¹,

Koga²,

Ito³

et al. 2021

Preprint

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Friction stir processing (FSP) enables surface modifications using a rotational tool and can likely be applied as a new post-weld treatment for improving fatigue strength. When applying FSP to high strength materials, tool wear occurring at the interface between the tool tip and the topmost steel layer has been regarded as an unavoidable issue and is related to the tool rotational speed. The present study investigated the relationship between the tool rotational speed and fatigue strength of arc-welded high-strength low-alloy (HSLA) steel joints with weld toes subjected to FSP using a spherical-tip WC tool. FSP was conducted on the weld toe of HSLA steel joints with various tool rotational speeds. Tool wear increased with increase in tool rotational speed, and consequently contents of constituent elements of the WC tool increased in the topmost steel layer of weld toes, leading to large increase of fatigue strength. One reason for the increase with tool rotational speed is significant increase of solid solution hardening due to supersaturated W and C in the topmost steel layer consisting of martensite laths. The hardened topmost steel layer prevented fatigue crack initiation, and the increased fatigue strength depended on the contents of supersaturated W and C.

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“…Most authors studying the HSLA steel welds' fatigue life usually focus on the butt welds from the high-strength steels. If they deal with the fillet welds, there are performed fatigue tests at selected stress amplitudes within the loading cycles from 10 5 up to 2 × 10 6 [17], and for the remaining stress amplitudes are just used an approximation of the fatigue curves or there are used cruciform welds at testing [18,19]. These welds are due to their symmetry of four fillet welds more suitable in light of our own testing.…”

Section: Introductionmentioning

confidence: 99%

Heat Input Influence on the Fatigue Life of Welds from Steel S460MC

Moravec

Sobotka

Solfronk

et al. 2020

Metals

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Fine-grained steels belong to the progressive materials, which are increasingly used in the production of welded structures subjected to both static and dynamic loads. These are unalloyed or microalloyed steels hardened mainly by the grain-boundary strengthening mechanism. Such steels require specific welding procedures, especially in terms of the heat input value. At present, there are studies of the welding influence on the change of thermomechanically processed steels’ mechanical properties, however mainly under static loading. The paper is therefore focused on the assessment of the welding effect under dynamic loading of welded joints. In the experimental part was determined the influence of five different heat input values on the change of weld fatigue life. As a result, there is both determination of five S-N curves for the double-sided fillet welds from the thermomechanically processed fine-grained steel S460MC and the quantification of the main influences reducing the fatigue life of the joint.

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Fatigue strength of TIG-dressed ultra-high-strength steel fillet weld joints at high stress ratio

Cited by 44 publications

References 13 publications

Effects of Microstructural Modification Using Friction Stir Processing on Fatigue Strength of Butt-Welded Joints for High-Strength Steels

Effects of Microstructural Modification Using Friction Stir Processing on Fatigue Strength of Butt-Welded Joints for High-Strength Steels

Fatigue Strength Improvement Due to Alloying Steel Weld Toes With WC-Tool Constituent Elements Through Friction Stir Processing

Heat Input Influence on the Fatigue Life of Welds from Steel S460MC

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