Hot Stamping Research Scenarios from the Last Decade

Abstract

Hot stamping technology has shown a significant scientific yield in the last decade. The research activity in that field has spread across several disciplines such as materials science, mechanics, process engineering, instrumentation, physics, or part-tool design engineering. Some recent publications have gathered this richness in the format of scientific reviews. This work is aimed to draw a picture of this scientific production in bibliometric terms, which are complementary to the existing reviews. The literature is, in this case, approached from different angles: geographical, collaborative, disseminative, and keyword-based. The first one leads to mapping the share of each region worldwide in advance of the hot stamping technology in terms of scientific production volume. The second angle allows identifying the most productive networks that have been established between institutions and the most influential agents in the field. The third one ranks the most influential journals and events based on citation rates, which indicates where to publish in order to achieve the highest impact. Finally, the fourth approach targets to infer research trends from assessing the keywords employed in the published scientific literature. Altogether, the results show a scenario with Asia as the major player both in volume and networking success, CHS2 as the most relevant event, and exploring alternatives to the conventional AlSi coated 22MnB5 hot stamping as a subject rising of interest.

Full text

Mater. Proc. 2021, 3, 26. https://doi.org/10.3390/IEC2M-09245 www.mdpi.com/journal/materproc
Proceedings
Hot Stamping Research Scenarios from the Last Decade
†
Luis Miguel Arias
1,2,
*, Garikoitz Artola
1
and Igone Porto
3
1
Fundación AZTERLAN, Basque Research and Technology Alliance (BRTA), 48200 Durango, Spain;
gartola@azterlan.es
2
Faculty of Engineering, University of Deusto, 48007 Bilbao, Spain
3
Deusto Business School, University of Deusto, 48007 Bilbao, Spain; igone.porto@deusto.es
* Correspondence: lmarias@azterlan.es; Tel.: +34-94-6215470
† Presented at the 1st International Electronic Conference on Metallurgy and Metals,
22 February–7 March 2021; Available online: https://iec2m.sciforum.net/.
Abstract: Hot stamping technology has shown a significant scientific yield in the last decade. The
research activity in that field has spread across several disciplines such as materials science, me-
chanics, process engineering, instrumentation, physics, or part-tool design engineering. Some recent
publications have gathered this richness in the format of scientific reviews. This work is aimed to
draw a picture of this scientific production in bibliometric terms, which are complementary to the
existing reviews. The literature is, in this case, approached from different angles: geographical, col-
laborative, disseminative, and keyword-based. The first one leads to mapping the share of each re-
gion worldwide in advance of the hot stamping technology in terms of scientific production volume.
The second angle allows identifying the most productive networks that have been established be-
tween institutions and the most influential agents in the field. The third one ranks the most influen-
tial journals and events based on citation rates, which indicates where to publish in order to achieve
the highest impact. Finally, the fourth approach targets to infer research trends from assessing the
keywords employed in the published scientific literature. Altogether, the results show a scenario
with Asia as the major player both in volume and networking success, CHS2 as the most relevant
event, and exploring alternatives to the conventional AlSi coated 22MnB5 hot stamping as a subject
rising of interest.
Keywords: bibliometric analysis; hot stamping; press hardening; die quenching
1. Introduction
For three decades, lightweighting has been one of the vectors of development and
innovation for the major automotive manufacturers. In this context, the Swedish
steelmaker SSAB (Svenskt Stål AB) located in Lulea introduced boron steels in automo-
biles in the 1980s together with the Swedish car manufacturer Saab [1]. The first vehicle
in which these materials were introduced was the Saab 9000, see Figure 1, namely the four
door reinforcements (side impact beam).
Citation: Arias, L.M.; Artola, G.;
Porto, I. Hot Stamping Research
Scenarios from the Last Decade.
M
ater. Proc. 2021, 3, 26. https://
doi.org/10.3390/IEC2M-09245
Published: 18 February 2021
Publisher’s Note: MDPI stays neu-
tral with regard to jurisdictional
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Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
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/by/4.0/).

Mater. Proc. 2021, 3, 26 2 of 14
Figure 1. First use of hot stamping on a production car. Saab 9000. Side impact beam [2].
Boron steels have been known for 50 years and used for their suitable wear resistance.
The genius of the steelmaker SSAB, together with the car manufacturer Saab in 1986, was
to propose its use in the resistant structure of the vehicles. The major difficulty was to
introduce it into the competitive automotive production world, extremely demanding be-
cause of the high production speeds and reliability required [3].
The presence of boron in these steels ensures high hardenability [4]. This character-
istic allowed the development of an industrial process that (a) starting from a hot sheet in
an austenitic state is (b) deformed and (c) tempered to obtain a 1500 MPa piece. The high
strength thus obtained is unique; in fact, no cold stamped material can be obtained for
typical automotive geometries.
Thanks to the increased strength of the material, car designers can design parts with
lower thickness and therefore lower weight for the same strength. In the Golf 5,
Volkswagen introduced 22MnB5 parts for the first time in the B-pillar subassembly, re-
ducing the weight by 1.5 kg compared to the previous model. The car contains three pil-
lars to support the roof and, therefore, the key to safety in a rollover, with the B pillar
being the intermediate one between doors. VW introduced the technology on a massive
scale in the Passat B6 model.
The weight reduction achieved at VW in the Passat B6 catapulted the development
of hot stamping to the rest of the car manufacturers.
The target for 2020 is for all models to have at least 50% of the body in white made up
of hot-stamped parts. This situation is reflected in growth forecasts for this technology, in-
cluding from Dr. Ralf Hund at the German hot stamping die company Braum Cartec [5],
and from J. Schimit, T. Lung (2018) [6], T. Taylor (2018) [7], and J. Fekete, R. Hall (2017) [8].
They all indicate that the number of parts obtained by hot stamping will increase from
about 100 million in 2020 to more than 600 million pieces in 2022. Volvo’s forecasts indi-
cate that up to 50% of the body-in-white mass may consist of parts obtained by hot stamp-
ing of boron steels.
Considering the above facts and, taking into account the interest shown by the auto-
motive industry in this area, the host stamping technology has not only a great but bril-
liant future.
2. Research Methodology
2.1. General Background
As part of a doctoral thesis research project, some sets of data about the hot stamping
study area have been obtained. The use of scientific indexed databases such as Web of
Science (WoS), Scopus, or Dimensions is really useful to carry out an analysis by means
of bibliometric indicators. Using these types of indicators, it is possible to analyze the
number of papers per year, per author, by source, and so on. The analysis of the results

Mater. Proc. 2021, 3, 26 3 of 14
shows concepts such as the relevance of the hot stamping subject over time, the most rel-
evant authors, the most influential journals, the most active countries working in that area,
etc. The entire period covers from the hot stamping origins to the present, but this article
shows the results of the period 2009–2019 that include two important reviews, [4,9].
2.2. Instrument and Procedures
This research was carried out using Scopus, a scientific database developed by
Elsevier. Scopus was inaugurated at the end of 2004, in November, with the content of
12,850 different journals. The language of reference was English, but it covered more than
30 other languages at the beginning. The database was focused on physical sciences,
health sciences, life sciences, social sciences, etc. [10].
Nowadays, Scopus includes, apart from articles, more than 3,700 indexed gold open
access journals, more than 210,000 books, and more than 8 million conference proceedings,
more than 8 million documents in open access; it also includes articles in press of more
than 5500 titles and covers 40 languages.
It covers areas of science, technology, medicine, and social sciences (including arts
and humanities). It covers more than 35,000 titles from all areas. Apart from magazines, it
has monographic series, conference proceedings, books (emptied at the book and chapter
level), or patents (more than 39 million, emptied from five official offices: WIPO, EPO, the
United States, Japan, and the United Kingdom). Its temporary coverage is from 1996, alt-
hough sometimes it reaches 1970. It is updated daily [11].
The research strategy began with the selection of the key terms. In that case, “die
quenching”, “hot stamping”, “press hardening”, and “press quenching” were selected.
The query shows 2316 documents. After that, only documents in English were selected,
1837 documents. Then, only journal type was filtered, 965 documents. The year 2020 was
also excluded, and the result showed 854 documents. Finally, the areas of interest were
also selected, choosing engineering, material science, physics and astronomy, computer
science, chemistry, environmental science, mathematics, chemical engineering, energy,
business, management and accounting, decision sciences, and multidisciplinary. That
showed 851 documents.
The search equation is shown below. It was used in July 2020 to achieve the used set
of data. For this article only, the results between 2009–2019 have been considered.
(TITLE-ABS-KEY (“Die quenching”) OR TITLE-ABS-KEY (“Hot stamping”) OR TI-
TLE-ABS-KEY (“Press hardening”) OR TITLE-ABS-KEY (“Press quenching”)) AND
(LIMIT-TO (LANGUAGE, “English”)) AND (LIMIT-TO (SRCTYPE, “j”)) AND (LIMIT-
TO (PUBYEAR, 2020)) AND (LIMIT-TO (SUBJAREA, “MATE”) OR LIMIT-TO (SUB-
JAREA, “ENGI”) OR LIMIT-TO (SUBJAREA, “PHYS”) OR LIMIT-TO (SUBJAREA,
“COMP”) OR LIMIT-TO (SUBJAREA, “CHEM”) OR LIMIT-TO (SUBJAREA, “CENG”)
OR LIMIT-TO (SUBJAREA, “BUSI”) OR LIMIT-TO (SUBJAREA, “DECI”) OR LIMIT-TO
(SUBJAREA, “ENVI”) OR LIMIT-TO (SUBJAREA, “ENER”) OR LIMIT-TO (SUBJAREA,
“MATH”) OR LIMIT-TO (SUBJAREA, “MULT”))
2.3. Data Analysis
The main bibliometric indicators included in this research show information about
the articles, the authors, their affiliation, country, the journal where the papers have been
published, citations, etc.
Considering this information, aspects such as scientific production in the hot stamp-
ing area have been analyzed, establishing the most relevant authors and journals. Cita-
tions have also been taken into account to show the most important investigators.
Finally, a descriptive analysis has been carried out using VosViewer [12], a software
tool provided by Leiden University, to show, using a textual map, the relationships be-
tween authors.

Mater. Proc. 2021, 3, 26 4 of 14
3. Research Results
Figure 2 shows exponential growth in the interest aroused by hot stamping technol-
ogy during the last decade.
Figure 2. Number of publications per year.
Figure 3 shows the top 10 productive journals regarding hot stamping technology.
Analyzing these results with those related to number of citations per author, it can be
concluded that the Journal of Materials Processing Technology is, obviously, the reference
journal for hot stamping technology with 57 articles in the last decade that have been cited
3095 times. It is also remarkable the contribution of CIRP Annals—Manufacturing Tech-
nology with only 13 publications but 1359 citations. This fact also makes this journal a
reference in this field.
Figure 3. Number of publications per journal.
16
24 29
49 44
75
68
96 102
92
136
0
20
40
60
80
100
120
140
160
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Publications
Year

Mater. Proc. 2021, 3, 26 5 of 14
Figure 4 shows the number of publications per year just for the top five journals. It is
remarkable the evolution of the International Journal of Advanced Manufacturing Tech-
nology, one of the latest to join.
Figure 4. Evolution of the number of publications per year and journal.
Figure 5 shows the top 10 authors with publications related to the hot stamping area.
The most productive researcher is J. Lin, with 31 publications. This data coincides with
the Figure 11 statistic, scientific production per country, where China is the most produc-
tive country. Top production researchers, such as Merklein, Bruschi, and Ghiotti, are also
the authors of the most relevant reviews in the field [2], which indicates that, in hot stamp-
ing, most productive authors are also the scientific references.
Figure 5. Evolution of the number of publications per author.
Figure 6 shows the top 10 institutions with the largest number of published works in
the field. The Chinese institutions are, of course, the most productive organizations con-
sidering that China is the most productive country as shown below.
0
10
20
30
40
50
60
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Publications
Year
Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
Journal of Materials Engineering and Performance
Steel Research International
International Journal of Advanced Manufacturing Technology
Journal of Materials Processing Technology
14
14
14
16
16
18
19
20
20
31
0 5 10 15 20 25 30 35
Oldenburg, M.
Maeno, T.
Dean, T.A.
Zhang, Y.
Ghiotti, A.
Merklein, M.
Hu, P.
De Cooman, B.C.
Bruschi, S.
Lin, J.
Publications
Author

Mater. Proc. 2021, 3, 26 6 of 14
Figure 6. Evolution of the number of publications per affiliation.
Top institutions in hot stamping are mostly universities. It is noticeable that the Uni-
versity of Lulea, the city where hot stamping was born, has kept its bonds to this technol-
ogy for more than 40 years. Another relevant aspect is the presence of Arcelor Mittal, an
industrial agent, in the top publishing entity list. This underlines the applied nature of the
research in hot stamping.
Figure 7 shows the citation evolution per year. This graph confirms the results shown
in Figure 1 regarding the interest shown in hot stamping technology. Nevertheless, this
absolute value does not reflect the actual relevance of citation, such as other factors as the
h-index.
Figure 7. Evolution of the number of citations per year.
20
23
23
24
24
24
28
29
36
52
0 102030405060
Shanghai Jiao Tong University
Pusan National University
Dalian University of Technology
ArcelorMittal
University of Waterloo
Luleå tekniska Universitet
Pohang University of Science and Technology
Huazhong University of Science and Technology
University of Science and Technology Beijing
Imperial College London
Documents
Affiliation
130
237
343 436
625
1027
887
1353
1736
1915
2063
0
500
1000
1500
2000
2500
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Citations
Years

Mater. Proc. 2021, 3, 26 7 of 14
Figure 8 shows the h-index value established in 53. This means that, between 2009
and 2019, 53 publications have been cited at least 53 times. When compared to a reference
technology, such as cold stamping, whose h-index is 30 for the same period, it is evident
that hot stamping presents a high interest in the scientific community.
Figure 8. H-index.
Figure 9 shows the 10 most influential authors who have had the most impact on this
topic. H. Karbasian and A.E. Tekkaya [4] are the most cited authors with their review in
2010, followed by M. Merklein and J. Lechler [9] with another review in 2016. Other rele-
vant authors, such as A. Ghiotti and S. Bruschi, were also among the highest production
authors.
Figure 9. Number of citations per author.
0
200
400
600
800
1000
1200
1
33
65
97
129
161
193
225
257
289
321
353
385
417
449
481
513
545
577
609
641
673
705
737
769
801
833
Citations
Documents
h-index
132
140
149
169
190
212
217
252
307
1034
0 200 400 600 800 1000 1200
Hoffmann H., So H., Steinbeiss H.
Merklein M., Wieland M., Lechner M., Bruschi S.,
Ghiotti A.
Bardelcik A., Salisbury C.P., Winkler S., Wells
M.A., Worswick M.J.
Merklein M., Lechler J., Geiger M.
Mohamed M.S., Foster A.D., Lin J., Balint D.S.,
Dean T.A.
Bouaziz O., Zurob H., Huang M.
Turetta A., Bruschi S., Ghiotti A.
Mori K., Maki S., Tanaka Y.
Merklein M., Lechler J.
Karbasian H., Tekkaya A.E.
Citations
Author
53

Mater. Proc. 2021, 3, 26 8 of 14
Figure 10 shows the number of citations per journal, the Journal of Materials Pro-
cessing Technology and CIRP Annals—Manufacturing Technology being the most influ-
ential in terms of the scientific dissemination of this topic. This observation fits with the
list of most prolific journals, meaning that productivity and quality, measured as citations,
are related in hot stamping literature.
Figure 10. Number of citations per journal.
Figure 11 shows the number of publications per country. The majority of the publi-
cations come from China, followed far behind by Germany and South Korea. The USA,
together with Canada, constitute a note of research activity too.
Figure 11. Number of publications per country.
Figure 12 shows a network visualization of the author keywords to establish the most
relevant of them. There is a total of 207 items grouped in six different clusters. The most
relevant keywords can be found in the green cluster with keywords such as hot stamping,
stamping, forging machines, etc. It is also relevant to the red cluster with terms such as
microstructure, mechanical properties, high strength steel, hardening, etc.
262
294
347
422
426
448
810
831
1359
3095
0 500 1000 1500 2000 2500 3000 3500
Applied Thermal Engine ering
International Journal of Impact Engineering
International Journal of Machine Tools and
Manufacture
International Journal of Adva nced Manufacturing
Technology
Materials and Design
Metallurgical and Materials Transa ctions A:
Physical Metallurgy and M aterials Science
Materials Science and En gineering A
Steel Research International
CIRP Annals - Manufac turing Technology
Journal of Materials Processin g Technology
Citations
Journal

Mater. Proc. 2021, 3, 26 9 of 14
Figure 12. Author keywords network.
Figure 13 shows a network map visualization of the authors related to the hot stamp-
ing technology that have at least two publications. There is a total of 316 authors grouped
in 23 clusters. J. Lin, the researcher with most publications in this decade, appears in the
pink cluster. S. Brushi, the second relevant researcher, appears in the yellow cluster.
Figure 13. Authors related to the hot stamping technology network.

Mater. Proc. 2021, 3, 26 10 of 14
4. Conclusions
Taking into account the analyses above, the following conclusions are stated:
• Hot stamping is a strongly evolving technology with an increasing scientific yield
and an impact level measured in terms of h-index above its technological competi-
tors, such as cold stamping.
• There is an established set of scientific sources that concentrates most of the produc-
tion and the citations. The most prolific journals also have the highest number of
citations, but regarding the number of citations per number of the total published
manuscripts, CIRP Annals—Manufacturing Technology outstands as a high-rele-
vance source.
• The most relevant authors, both measured in terms of their production and their
citation volume, are also the references in terms of the key reviews in the field.
• It is noticeable that industrial research in hot stamping appears in the top 10 institu-
tions in terms of scientific production, which points out that it is a relevant industrial
driving force for generating new knowledge in the field.
• Geographically, scientific production is concentrated in China, with two further fo-
cal points in Europe (led by Germany) and North America (led by the USA).
• Relation graphs show that there are six different thematic clusters in hot stamping
research, related to process parameters, material properties, assembling technolo-
gies, the quenching process itself, alternatives to steel hot stamping and die cooling.
• In terms of networking, several stable research groups are identified, with a big clus-
ter around the Chinese researchers and several satellites in Sweden, Italy, Germany,
the U.K. and Canada.
Thus, hot stamping is a promising and growing technology with a very intense ac-
tivity powered by industrial interest. It is expected that the already established research
teams will keep publishing their results in a reduced number of sources.
Author Contributions: For research articles with several authors, a short paragraph specifying their
individual contributions must be provided. The following statements should be used “Conceptual-
ization, L.M.A. and G.A.; methodology, I.P.; software, L.M.A.; validation, L.M.A., G.A. and I.P.; for-
mal analysis, L.M.A. and G.A.; investigation, L.M.A., G.A. and I.P.; resources, L.M.A.; data curation,
L.M.A.; writing—original draft preparation, L.M.A., G.A. and I.P.; writing—review and editing,
L.M.A., G.A. and I.P.; supervision, G.A. and I.P. All authors have read and agreed to the published
version of the manuscript.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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