Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel
The cold roll bonding process of a laminar metal composite consists of three steps, i.e., surface treatment, cold roll bonding, and heat treatment. The surface pretreatment is the precondition of obtaining a metal composite with a superior bonding level. The influence of the steel plate surface cond...
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Tang, C. Liu, Z. Zhou, D. Wu, S. 2020-11-28T15:34:27Z 2020-11-28T15:34:27Z 2015 Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel / C. Tang, Z. Liu, D. Zhou, S. Wu // Проблемы прочности. — 2015. — № 1. — С. 172-178. — Бібліогр.: 6 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/173278 539.4 The cold roll bonding process of a laminar metal composite consists of three steps, i.e., surface treatment, cold roll bonding, and heat treatment. The surface pretreatment is the precondition of obtaining a metal composite with a superior bonding level. The influence of the steel plate surface condition on the bonding strength is studied, based on the bonding mechanism of a laminar metal composite by cold roll bonding. Flap disc grinding is a better surface treatment than wire brushing for obtaining high bonding strength. Within a certain range, the larger the surface roughness, the higher the bonding strength. Comparing different grinding textures, viz longitudinal, transverse, and 45° with respect to the rolling direction, it was revealed that the longitudinal surface texture was more advantageous for bonding. Процесс связывания холодной прокаткой для слоистого металлического композиционного материала состоит из трех этапов: поверхностная обработка, связывание холодной прокаткой и термообработка. Предварительная обработка поверхности является непременным условием получения металлического композиционного материала с высокой прочностью сцепления. Изучено влияние состояния поверхности стальной пластины на прочность сцепления с учетом механизма связывания слоистого металлического композиционного материала холодной прокаткой. Установлено, что шлифовальный диск обеспечивает лучшую обработку поверхности, чем проволочная щетка, для создания высокой прочности сцепления. В определенном диапазоне при большой шероховатости поверхности прочность сцепления лучше. Сравнение различных рельефов поверхности после шлифования, а именно: продольный, поперечный и 45-градусный по отношению к направлению прокатки, показывает, что продольный рельеф поверхности способствует повышению прочности сцепления. The present study was financed by the National High-Tech Research and Development Program (2013AA031301) and Chinese National-International Scientific and Technological Cooperation Project (2013DFB50170). The authors would like to thank the University of Science & Technology Beijing (USTB) for providing rolling mill and materials used in this work. en Інститут проблем міцності ім. Г.С. Писаренко НАН України Проблемы прочности Научно-технический раздел Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel Поверхностная обработка при процессе связывания холодной прокаткой для алюминиевого сплава и малоуглеродистой стали Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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DSpace DC |
| title |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel |
| spellingShingle |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel Tang, C. Liu, Z. Zhou, D. Wu, S. Научно-технический раздел |
| title_short |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel |
| title_full |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel |
| title_fullStr |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel |
| title_full_unstemmed |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel |
| title_sort |
surface treatment with the cold roll bonding process for an aluminum alloy and mild steel |
| author |
Tang, C. Liu, Z. Zhou, D. Wu, S. |
| author_facet |
Tang, C. Liu, Z. Zhou, D. Wu, S. |
| topic |
Научно-технический раздел |
| topic_facet |
Научно-технический раздел |
| publishDate |
2015 |
| language |
English |
| container_title |
Проблемы прочности |
| publisher |
Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| format |
Article |
| title_alt |
Поверхностная обработка при процессе связывания холодной прокаткой для алюминиевого сплава и малоуглеродистой стали |
| description |
The cold roll bonding process of a laminar metal composite consists of three steps, i.e., surface treatment, cold roll bonding, and heat treatment. The surface pretreatment is the precondition of obtaining a metal composite with a superior bonding level. The influence of the steel plate surface condition on the bonding strength is studied, based on the bonding mechanism of a laminar metal composite by cold roll bonding. Flap disc grinding is a better surface treatment than wire brushing for obtaining high bonding strength. Within a certain range, the larger the surface roughness, the higher the bonding strength. Comparing different grinding textures, viz longitudinal, transverse, and 45° with respect to the rolling direction, it was revealed that the longitudinal surface texture was more advantageous for bonding.
Процесс связывания холодной прокаткой для слоистого металлического композиционного материала состоит из трех этапов: поверхностная обработка, связывание холодной прокаткой и термообработка. Предварительная обработка поверхности является непременным условием получения металлического композиционного материала с высокой прочностью сцепления. Изучено влияние состояния поверхности стальной пластины на прочность сцепления с учетом механизма связывания слоистого металлического композиционного материала холодной прокаткой. Установлено, что шлифовальный диск обеспечивает лучшую обработку поверхности, чем проволочная щетка, для создания высокой прочности сцепления. В определенном диапазоне при большой шероховатости поверхности прочность сцепления лучше. Сравнение различных рельефов поверхности после шлифования, а именно: продольный, поперечный и 45-градусный по отношению к направлению прокатки, показывает, что продольный рельеф поверхности способствует повышению прочности сцепления.
|
| issn |
0556-171X |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/173278 |
| citation_txt |
Surface Treatment with the Cold Roll Bonding Process for an Aluminum Alloy and Mild Steel / C. Tang, Z. Liu, D. Zhou, S. Wu // Проблемы прочности. — 2015. — № 1. — С. 172-178. — Бібліогр.: 6 назв. — англ. |
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| fulltext |
UDC 539.4
Surface Treatment with the Cold Roll Bonding Process for an Aluminum
Alloy and Mild Steel
C. Tang,
a,1
Z. Liu,
a
D. Zhou,
b
and S. Wu
a
a School of Electro-Mechanical Engineering, Guangdong University of Technology, Guangzhou,
China
b Scientific Research Institute, Yinbang Metal Clad Material Co. Ltd, Wuxi, China
1 tangchl@gdut.edu.cn
The cold roll bonding process of a laminar metal composite consists of three steps, i.e., surface
treatment, cold roll bonding, and heat treatment. The surface pretreatment is the precondition of
obtaining a metal composite with a superior bonding level. The influence of the steel plate surface
condition on the bonding strength is studied, based on the bonding mechanism of a laminar metal
composite by cold roll bonding. Flap disc grinding is a better surface treatment than wire brushing
for obtaining high bonding strength. Within a certain range, the larger the surface roughness, the
higher the bonding strength. Comparing different grinding textures, viz longitudinal, transverse, and
45� with respect to the rolling direction, it was revealed that the longitudinal surface texture was
more advantageous for bonding.
Keywords: cold roll bonding, surface treatment, bonding strength, surface topography,
surface texture, surface roughness.
Introduction. The air cooling system units of power stations are composed of finned
tubes consisting of aluminum alloy fins welded together with the parent tube made of mild
steel. However, brittle intermetallic compounds, which are formed at the weld interface
during the process of brazing the aluminum alloy fins directly to the steel parent tube,
deteriorate the joint quality. As a solution to this problem, a transition layer of aluminum is
cladded over the steel surface by cold roll bonding: when this transition layer of aluminum
is welded with the aluminum alloy fins instead of steel, a higher quality of the resulting
joint is guaranteed.
The cold roll bonding process of Al/St composites consisting of three steps (surface
treatment, cold roll bonding and heat treatment), is bonding together the aluminum alloy
and steel under high pressure by rolling at room temperature.
The bonding mechanism of cold roll bonding (CRB) is very complicated. Many
experimental and theoretical studies imply that several bonding mechanisms are realized at
the different stages of CRB process, such as: thin film formation [1–5], joint recrystallisation
[6], dislocation, diffusion bonding, overcoming energy barriers, the three-stage mechanism,
etc. The lack of persuasive experimental data and the complexiity of the CRB mechanisms
give rise to numerous diversified yet insufficiently substantiated theories, which have the
following common feature: the surface treatment is treated as the precondition to get high
bonding strength of composites. In this study, the effect of surface treatment parameters, such
as roughness, topography and texture directions of the metal surface, on the bonding strength
of composite sheets are investigated.
At present, many studies had been performed on the factors affecting the bonding
strength, such as reduction in thickness, rolling speed, annealing treatment, initial thickness,
presence of particles between strips, etc. [6]. However, studies on the surface pretreatment
are quite scarce. The surface condition of the metal to be bonded has a strong effect on the
bonding strength. In the general case, metal surface is covered with a thin film composed of
oxides, adsorbed ions, grease, moisture and dust particles. A surface treatment can provide
© C. TANG, Z. LIU, D. ZHOU, S. WU, 2015
172 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 1
not only the effective removal of the contamination layer covering the metal surface and
uncover the bulk meta, but also favorable surface conditions for mechanical occlusion. It is
well-known that currently available surface treatment methods have different effects on the
surface state and bonding strength, while chemical treatment and mechanical grinding are
considered to make the optimal combination of surface treatments, in case of cold roll
bonding of metal composite sheets.
1. Experimental Procedures.
1.1. Materials. The materials under study are 08AL mild steel in the as-rolled state
and 4A60 aluminum alloy in as-received state, chemical composition and mechanical
properties of which are listed in Tables 1 and 2, respectively. As-received material blanks are
cut along the original rolling direction to produce specimens of 4A60 aluminum alloy with
dimensions 300�75�0.25 mm and 08AL mild steel with dimensions 300�95�3.75 mm.
1.2. Surface Pretreatment. Many studies have shown that the best method of surface
treatment is chemical degreasing before mechanical grinding. Therefore, in this study,
chemical degreasing in 10% hydrochloric acid bath and cleansing with acetone was used
with the following mechanical grinding of specimen surfaces with an angle grinder (850 W
power, 72 m/s rotating speed).
Comparision of the two bonded metals shows that the mild steel is much harder and
less prone to plastic deformation than the aluminum alloy. Since the surface state of a mild
steel is the key factor affecting the bonding strength, only the mild steel surface treatment
parameters are investigated in this study.
1.3. Surface Roughness Measurement. The surface roughness of seven random areas
on each specimen is measured with an OSL4000 confocal laser scanning microscope of
Olympus according to ISO 25178 standard. The measurement area is 640�640 �m;
Gaussian filter is used to measure the arithmetic average deviation of surface roughness
(Sa). The maximum and minimum of the measurements are disregarded; the average value
of the remaining five is taken as the surface roughness value.
1.4. Cold Roll Bonding. The CRB experiment is conducted via a reversible four-roller
laboratory rolling mill with a loading capacity of 200 ton, a backup roll diameter of 400 mm,
and a work roll diameter of 170 mm. The roll speed is 3 m/min and reduction rate is 55%.
Specimens are stacked with rivets to avoid running deviations during the rolling process.
1.5. Tensile Shear Strength Test. According to the GB/T 6396-2008 standard, the
bonding strength is evaluated via the tensile shear test, where the thickness of composite
sheet is less than 10 mm. The tensile shear test is carried out with an WDW-100 micro-
computer-controlled servo-hydraulic universal tensile machine with the load cell of 50 N
T a b l e 1
Chemical Composition of Aluminum Alloy and Mild Steel Sheet (wt.%)
08AL C Mn Si S Ni Cr Cu Al Fe
0.03 0.212 0.014 0.004 0.007 0.015 0.026 0.004 99.68
4A60 Si Fe Mn Mg Zn Ti Cu Al Other
0.80 0.40 0.05 0.05 0.05 0.03 0.05 99.50 �0.05
T a b l e 2
Mechanical Properties of Aluminum Alloy and Mild Steel Sheet
Material Tensile strength
(MPa)
Yield strength
(MPa)
Elongation
(%)
Hardness
(Hv)
08AL 470 460 11.0 130
4A60 85 45 19.4 37
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Surface Treatment with the Cold Roll Bonding Process ...
and displacement rate of 2 mm/min. However, in the conducted tensile shear tests, fracture
often occurs in the aluminum layer, instead of the expected interface, because the aluminum
layer is too thin. To increase its thickness, a 2 mm-thick layer of 4343/3003 aluminum alloy
was brazed over the aluminum layer. The tensile shear strength is calculated by the
following formula:
T F A� max , (1)
where T is the tensile shear strength, Fmax is the maximum shear force (N), and A is the
shear area (mm2).
2. Results and Discussion.
2.1. Surface Topography of Different Grinding Methods. Surface topographies of a
steel sheet subjected to flap disc grinding and wire brushing are shown in Figs. 1a and b,
respectively. It is easy to see that the flap disc grinding produces very deep grooves and
cracks at the steel surface, which makes it easier for the soft aluminum to squeeze into this
surface and form a mechanical occlusion with steel. Moreover, the flap disc grinding
produces a hard and brittle grind-hardened layer at the steel surface. According to the film
theory, the governing mechanism in the cold roll bonding process is as follows: the brittle
and hard layers break up along with the extension of the surfaces during rolling, while the
internal fresh metal layers are extruded out through the cracks and exposed to contact with
each other. Stable molecular bonds will be formed at the interface when the newly exposed
surfaces of the two metals reach the interatomic distance under high enough pressure. On
the other hand, the analysis of Fig. 1b implies that wire brushing process fails to provide
the complete removal of the original surface defects, while the resulting surface is less
susceptable to bonding than the one produced via flap disc grinding. This is confirmed by
the micrographs of the bonded steel surfaces after rolling presented in Figs. 2a and b for
pretreatment by flap disc grinding and wire brushing, respectively. Cracks filled with the
soft aluminum alloy at the steel surface pretreated by flap disc grinding are wider than
those after wire brushing. This explains why the bonding strength of the laminar metal
composite produced by flap disc grinding is higher than that pretreated by wire brushing,
which is confirmed by the experimental results listed in Table 3.
Fig. 1. Surface topography of a steel sheet before rolling �1000: (a) flap disc grinding; (b) wire
brushing.
174 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 1
C. Tang, Z. Liu, D. Zhou, and S. Wu
T a b l e 3
Tensile Shear Strength of Grinding Methods
Grinding methods Tensile shear strength (N/mm2) Sa (�m)
Flap disc 72 1.89
Wire brush 64 1.78
The mechanical grinding can produce some peak-shaped structures protruding from
the steel surface, which enhance the steel piercing into the adjoining aluminum alloy
surface, as well as the mechanical occlusion contributing to the bonding process. 3D
surface topographies depicted in Fig. 3 indicate that the above peaks and their amplitudes
are significantly higher and their distribution along the surface is more uniform, in case of
flap disc grinding, as compared to wire brushing. This trend is also corroborated by the
SEM micrographs of the bonded steel surfaces, which are shown in Fig. 4.
2.2. Effect of Surface Roughness on Bonding Strength. Five flap discs of different
specifications (P40, P60, P80, P100, and P120) were chosen to grind the steel surface. The
relationship between the bonding strength and roughness is shown in Fig. 5. The bonding
strength is found to increase with the surface roughness within a certain roughness range.
Fig. 3. 3D surface topography of a steel sheet �1000: (a) flap disc grinding; (b) wire brushing.
Fig. 4. SEM of the bonding surface of steel sheet (R � 55%) �500: (a) flap disc grinding; (b) wire
brushing.
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Surface Treatment with the Cold Roll Bonding Process ...
Fig. 2. Fracture surface of a steel sheet after rolling with 55% reduction �1000: (a) flap disc
grinding; (b) wire brushing.
As shown in Fig. 6, long ridge-shaped grooves (about 32–45 �m deep) are produced
at the steel surface by flap disc grinding, while more coarse flap discs produce deeper
grooves at the ground steel surfaces.
In the CRB process, the contact area of the bonded metals is critical for the bonding
strength. A rough surface can increase the contact area, while deep grooves can contribute
to mechanical occlusion of the bonded metals, insofar as the localized shear deformation
during the rolling process ensures the exposure of the bulk metals and their close contact.
Thus, higher surface roughness, groove depth, and mechanical occlusion imply higher
shear deformations, which, in turn, increase the bonding strength.
2.3. Surface Texture Direction Effect on the Bonding Strength. The surface texture
direction effect on the bonding strength is quite topical [6]. Therefore, three surface texture
directions were investigated in this study: longitudinal, 45�-inclined, and transverse to the
Fig. 5. Variation in average tensile strength vs surface roughness (flap disc grinding).
Fig. 6. Surface topography for flap disc grinding �400: (a) P40; (b) P60; (c) P80; (d) P100; (e) P120.
176 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 1
C. Tang, Z. Liu, D. Zhou, and S. Wu
rolling direction (Fig. 7). The experimental results on the tensile shear strength and surface
roughness, which are listed in Table 4, indicate that respective surface roughness values are
quite close, while the shear strength values can be arranged in the decreasing order as
follows: longitudinal, 45�-inclined, and transverse texture directions.
According to the rule of the minimum roll bonding resistance, metal flow during the
rolling process always occurs along the least-resistance direction. Since the resistance along
the rolling direction is the least one, the texture direction of the metal surface coinciding
with the rolling direction is the most lucrative for metal bonding, and, therefore, the
longitudinal grinding surface texture is the most advantageous.
Conclusions. Based of the performed study of the effect of steel plate surface
conditions on the bonding strength, the following conclusions can be drawn:
1. The comparative analysis of two surface treatment methods: flap disc grinding and
wire brushing – was performed. The flap disc grinding process is found to be more
advantageous for the subsequent cold roll bonding than wire brushing.
2. The relationship between the bonding strength and the surface roughness is
investigated. It is shown that a certain surface roughness is necessary for cold roll bonding,
and, within a certain range, a higher surface roughness results in a higher interface bonding
strength.
3. Three surface texture directions were investigated: longitudinal, 45�-inclined, and
transverse to the rolling direction. The tensile shear strength values can be arranged in the
decreasing order as follows: longitudinal, 45�-inclined, and transverse texture direction.
The longitudinal grinding surface texture is found to be the most advantageous for
bonding.
Acknowledgments. The present study was financed by the National High-Tech
Research and Development Program (2013AA031301) and Chinese National-International
Scientific and Technological Cooperation Project (2013DFB50170). The authors would
like to thank the University of Science & Technology Beijing (USTB) for providing rolling
mill and materials used in this work.
T a b l e 4
Tensile Shear Strength of Different Texture
Texture direction Tensile shear strength (N/mm2) Roughness Sa (�m)
Longitudinal 74 1.17
45�-inclined 40 1.43
Transverse 32 1.18
Fig. 7. Surface topography observed with a confocal laser scanning microscope �400: (a) longitudinal
texture; (b) transverse texture; (c) 45�-inclined texture.
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Surface Treatment with the Cold Roll Bonding Process ...
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3. V. Y. Mehr, M. R. Toroghinejad, and A. Rezaeian, “The effects of oxide film and
annealing treatment on the bond strength of Al–Cu strips in cold roll bonding
process,” Mater. Design, 53, 174–181 (2014).
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Mater. Sci. Technol., 27, 1101–1108 (2011).
Received 20. 10. 2014
178 ISSN 0556-171X. Ïðîáëåìû ïðî÷íîñòè, 2015, ¹ 1
C. Tang, Z. Liu, D. Zhou, and S. Wu
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