Experimental evaluation of HFMI effectiveness for weld repairs

Jakub Štěpán; Pavel Ryjáček; Miloslav Kepka; Radovan Minich

doi:10.2478/cee-2026-0027

Experimental evaluation of HFMI effectiveness for weld repairs

Civil and Environmental Engineering

Volume 22 (2026): Issue 2 (June 2026)

By: Jakub Štěpán, Pavel Ryjáček, Miloslav Kepka and Radovan Minich

Open Access

|Jun 2026

Figures & Tables

Principle of the HFMI treatment method (Campagnolo et al., 2021)

Allowed FAT category increase for HFMI treated Welds (Marquis & Barsoum, 2016)

Geometry of the specimen with butt V-weld (identical for the specimen with X-weld)

Table 1:

Number of specimens for fatigue testing

Weld type	V and X
Stress ratio R	0.1
Treatment	As Welded	HFMI	HFMI repair
S355J2+N	4	4	4
S460NL	6	5	4
S690QL	5	4	4
S960QL	4	4	4

Table 2:

Technical manufacturing parameters

S355 specimens: Technical manufacturing parameters
Welding method	135 (MAG) according to EN ISO 4063
Filler material	EN ISO 14341-A: G46 3 C1 4Si1/G50 5 M21 4Si1
Shielding gas	M21 (82% Ar + 18% CO2) – STARGON 18
Preheat temperature	-
S460 specimens: Technical manufacturing parameters
Welding method	135 (MAG) according to EN ISO 4063
Filler material	EN ISO 14341-A: G46 3 C1 4Si1/G50 5 M21 4Si1
Shielding gas	M21 (82% Ar + 18% CO2) – STARGON 18
Preheat temperature	-
S690 specimens: Technical manufacturing parameters
Welding method	135 (MAG) according to EN ISO 4063
Filler material	EN ISO 16834-A: G 69 4 M21 Mn3Ni1CrMo
Shielding gas	M21 (82% Ar + 18% CO2) – STARGON 18
Preheat temperature	100 °C
S960 specimens: Technical manufacturing parameters
Welding method	135 (MAG) according to EN ISO 4063
Filler material	EN ISO 16834-A: G 89 4 M20 Mn4Ni2CrMo
Shielding gas	M21 (82% Ar + 18% CO2) – STARGON 18
Preheat temperature	150 °C

Testing equipment with specimen during the fatigue experiment

Localization of the fatigue crack using NDT penetrant testing (PT) after completion of loading

Repair of a specimen affected by a fatigue crack

Table 3:

Number of cycles to failure for S355 steel grade specimens

Material	S355
Stress ratio R	0.1
Spec. number	Treatment	Stress range [MPa]	Number of cycles to failure
1	As Welded	100	10 000 000^*
2	As Welded	100	10 000 000^*
3	As Welded	200	1 531 011
4	As Welded	200	1 486 900
5	HFMI	200	10 000 000^*
6	HFMI	200	5 000 000^*
7	HFMI	250	5 000 000^*
8	HFMI	300	1 900 389
9	HFMI repair	300	2 728 703
10	HFMI repair	300	1 741 976
11	HFMI repair	320	474 210
12	HFMI repair	320	974 818

* No failure occurred in the specimen. The limit number of cycles was reached without the formation of a fatigue crack (runout).

Comparison of results S355 steel grade specimens

Table 4:

Number of cycles to failure for S460 steel grade specimens

Material	S460
Stress ratio R	0.1
Spec. number	Treatment	Stress range [MPa]	Number of cycles to failure
13	As Welded	200	474 157
14	As Welded	200	3 018 047
15	As Welded	300	210 929
16	As Welded	300	331 088
17	As Welded	350	129 096
18	As Welded	350	309 218
19	HFMI	200	4 393 464
20	HFMI	200	5 000 000^*
21	HFMI	300	984 402
22	HFMI	350	847 345
23	HFMI	350	947 066
24	HFMI repair	300	589 985
25	HFMI repair	300	1 175 960
26	HFMI repair	350	254 244
27	HFMI repair	350	688 634

* No failure occurred in the specimen. The limit number of cycles was reached without the formation of a fatigue crack (runout).

Comparison of results S460 steel grade specimens

Table 5:

Number of cycles to failure for S690 steel grade specimens

Material	S690
Stress ratio R	0.1
Spec. number	Treatment	Stress range [MPa]	Number of cycles to failure
28	As Welded	200	2 674 867
29	As Welded	300	501 424
30	As Welded	300	372 388
31	As Welded	500	55 796
32	As Welded	500	79 230
33	HFMI	300	5 000 000^*
34	HFMI	350	5 000 000^*
35	HFMI	500	167 150
36	HFMI	500	289 026
37	HFMI repair	400	426 198
38	HFMI repair	400	116 523
39	HFMI repair	450	309 494
40	HFMI repair	450	160 857

* No failure occurred in the specimen. The limit number of cycles was reached without the formation of a fatigue crack (runout).

Comparison of results S690 steel grade specimens

Table 6:

Number of cycles to failure for S960 steel grade specimens

Material	S960
Stress ratio R	0.1
Spec. number	Treatment	Stress range [MPa]	Number of cycles to failure
41	As Welded	300	492 569
42	As Welded	500	55 205
43	As Welded	500	60 774
44	As Welded	800	16 832
45	HFMI	300	5 000 000^*
46	HFMI	500	70 656
47	HFMI	500	293 794
48	HFMI	800	15 584
49	HFMI repair	450	110 727
50	HFMI repair	450	172 590
51	HFMI repair	500	32 423
52	HFMI repair	500	110 359

* No failure occurred in the specimen. The limit number of cycles was reached without the formation of a fatigue crack (runout).

Comparison of results S960 steel grade specimens

References

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DOI: https://doi.org/10.2478/cee-2026-0027 | Journal eISSN: 2199-6512 (formerly 1336-5835) | Journal ISSN: 1336-5835

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Language: English

Page range: 620 - 631

Submitted on: Jul 27, 2025

Accepted on: Sep 30, 2025

Published on: Jun 19, 2026

Published by: University of Žilina

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Fatigue,

Related subjects:

Business and economics,

Business management,

Industries,

Environmental management

© 2026 Jakub Štěpán, Pavel Ryjáček, Miloslav Kepka, Radovan Minich, published by University of Žilina
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 22 (2026): Issue 2 (June 2026)

Experimental evaluation of HFMI effectiveness for weld repairs

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