The composite material led to a significant decrease in the corrosion 36 current density in soil solution, compared with that of hot dip galvanized steel and bare carbon steel.. 74 In th
Trang 15
6
7 Wenning Shena,⇑, Lajun Fenga, Hui Fengb, Ying Caoa, Lei Liua, Mo Caoa, Yanfeng Gea
School of Materials Science and Engineering, Xi’an University of Technology, No 5 South Jinhua Road, Xi’an 710048, China
Shaanxi Institute of Zoology, Xi’an 710032, China
10
1 4 a r t i c l e i n f o
15 Article history:
16 Received 4 October 2016
17 Accepted 28 December 2016
18 Available online xxxx
19 Keywords:
20 Stainless steel
21 Carbon steel
22 Anti-corrosion
23 Conductivity
24 Electrochemical
25 EIS
26
2 7
a b s t r a c t
28 The composite material of 304 stainless steel reinforced Q235 carbon steel has been prepared by
modi-29 fied hot-rolling process The resulted material was characterized by scanning electron microscope,
three-30 electrode method, fault current impact method, electrochemical potentiodynamic polarization curve
31 measurement and electrochemical impedance spectroscopy The results showed that metallurgical bond
32 between the stainless steel layer and carbon steel substrate has been formed The composite material
33 exhibited good electrical conductivity and thermal stability The average grounding resistance of the
34 composite material was about 13/20 of dip galvanized steel There has no surface crack and bubbling
35 formed after fault current impact The composite material led to a significant decrease in the corrosion
36 current density in soil solution, compared with that of hot dip galvanized steel and bare carbon steel
37
On the basis polarization curve and EIS analyses, it can be concluded that the composite material showed
38 improved anti-corrosion property than hot-dip galvanized steel
39
Ó 2016 Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://
40 creativecommons.org/licenses/by-nc-nd/4.0/)
41 42
43 Introduction
44 Using grounding materials in substation is the important
mea-45 sure to guarantee safe running of power system and electrical
46 equipment, and to ensure personal safety[1–4] However, power
47 system fault occurs frequently in China, due to the corrosion of
48 grounding materials As a result, it has to excavate the substation
49 grounding grids again and lay new grounding materials, resulting
50 in increased cost [5] In order to prevent the corrosion of the
51 grounding materials, copper material is usually used as grounding
52 materials internationally Nevertheless, China is facing the
prob-53 lem of copper scarcity, which has lead to high cost Moreover,
54 the released copper ions easily pollute groundwater These
disad-55 vantages have restricted the application of copper materials as
56 grounding materials in our country[6,7] Several researches have
57 shown that hot dip galvanized steel materials exhibited high
corro-58 sion resistance, good conductive ability and lower price Therefore,
59 they are often used as grounding materials in our country[8–10]
60 Since the grade of transmission line voltage has increased, it
61 needs to improve the anti-corrosion property of the grounding
62 materials As a result, hot dip galvanized steel materials for extra
63 high voltage grounding grid are hard to meet the design
require-64 ment[11,12] It has been found that stainless steel exhibits
supe-65 rior anti-corrosion property and heat resistance [13–15]
66 Moreover, it has the same material with other devices connected
67 with grounding grid such as drop line, which can’t produce
micro-68 cell corrosion Thus, stainless steel material can be used as effective
69 substitution of hot dip galvanized steel However, the resistance of
70 stainless steel is very high When used as grounding material, it
71 can’t conduct current in time In addition, its cost is higher
There-72 fore, they are disadvantages for the application of stainless steel
73 grounding material
74
In this work, we prepared stainless steel/carbon steel composite
75 materials by modified hot-rolling process, using 304 stainless steel
76
as the cladding material and Q235 carbon steel as the substrate
77 Thus, the prepared composite materials can not only exhibit the
78 excellent corrosion resistance of stainless steel, but also present
79 good conductive ability of carbon steel, which can be used as
80 potential grounding materials And their bonding interface,
corro-81 sion resistance, and electrical conductivity were estimated
82 Experimental
83 Materials
84 Stainless steel type 304 (in wt%: C 0.039, Si 0.44, Mn 1.21, P
85 0.018, S 0.002, Ni 8.09, Cr 18.23, Ti 0.042 and N 0.039) and carbon
http://dx.doi.org/10.1016/j.rinp.2016.12.050
2211-3797/Ó 2016 Published by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ).
⇑ Corresponding author.
E-mail address: shenwenning@qq.com (W Shen).
Contents lists available atScienceDirect
Results in Physics
j o u r n a l h o m e p a g e : w w w j o u r n a l s e l s e v i e r c o m / r e s u l t s - i n - p h y s i c s
Please cite this article in press as: Shen W et al Preparation and characterization of 304 stainless steel/Q235 carbon steel composite material Results Phys
Trang 286 steel type Q235 (in wt%: C 0.22, Si 0.05 max, Mn 0.48, P 0.012 and S
87 0.022) were used as the clad layer material and substrate
respec-88 tiviely for the preparation of stainless steel/carbon steel composite
89 material Hot dip galvanized steel bar and bare Q235 carbon steel
90 were used as control
91 Preparation of stainless steel/ carbon steel composite material
92 In order to ensure the discharging efficiency of grounding
mate-93 rials, their cross sectional area has to be larger than 300 mm2based
94 on grounding grid design Thus, Q235 carbon steel rods
95 (U100 mm 1000 mm) were used as substrate, and 304 stainless
96 steel tubes (U100 mm 6 mm 1010 mm) were used as clad
97 layer material in this work The stainless steel/carbon steel
com-98 posite material was prepared by modified hot rolling process
99 Specifically, the carbon steel bar was put into stainless steel tube
100 Our preliminary experiment results suggested that the length of
101 the tube should be longer than the bar, so as to avoid the cracking
102 of cladding layer in the rolling process As a result, the two ends of
103 the tube have an allowance of 5 mm Subsequently, the two ends
104 were closed by welding Thus, cracks would not appear in the ends
105 It was then heated up to 1200°C and hot rolled for six times After
106 that, the composite material with a diameter around 22 mm was
107 obtained
108 Interface characterization
109 The composite material rod was cut into a cylinder with a
110 height of 1 cm and its cross surface was polished by waterproof
111 abrasive paper Its macroscopic feature was recorded by digital
112 camera The treated sample was then etched by nitric acid alcohol
113 solution (4 wt%) Subsequently, GX71 metallography microscope
114 was used to study the microstructure of the interface, and
JSM-115 6700F scanning electron microscope (SEM) was used to observe
116 the interfacial morphology The components of the interfacial
tran-117 sition zone were analyzed by line scan
118 Grounding resistance testing
119 MS2302 grounded resistance measuring instrument was used
120 to test the grounding resistance of the samples The test objects
121 were those underground in 10–55 cm
122 Thermal stability measurement
123 The grounding materials must have high anti-thermal shock
124 resistance, since large quantity of heat can be produced when large
125 short circuit current flowing through the grounded conductor In
126 this work, fault current impact method was used to study the
127 anti-thermal shock resistance of the grounding material based on
128 GB3048.7 Specifically, two composite material rods
129 (U22 mm 1000 mm, marked with sample 1 and sample 2
130 respectively) were selected They were then impacted by fault
cur-131 rent of 24.8 KA for three times Subsequently, the changes of the
132 sample surface were observed After that, the resistance in per unit
133 length of the samples was measured using direct current bridge
134 method when cooling to room temperature The impact time was
135 4 s
136 Corrosion resistance analysis
137 The soli solution from a substation in Shaanxi Province was
138 used as corrosion medium The basic preparation procedures were
139 as follows, the soil retrieved from the soil layer of 80 cm was mixed
140 with deionized water in a ratio of 1:5 Subsequently, the
super-141 natant used as testing medium was obtained after 24 h standing
142 Its contents are shown inTable 1
143 The three-electrode system was applied to study the electrical
144 potential and the corrosion current of the composite material
145 Hot dip galvanized steel and Q235 carbon steel were used as
con-146 trol The sample was working electrode, platinum electrode was
147 auxiliary electrode, and saturated calomel electrode (SCE) was
148 the reference electrode The test area was 1 cm2and the soak
med-149 ium was the soil solution The polarization curve was measured by
150 CS350 electrochemical workstation with a scanning speed of 1 Mv/
151 S
152 Electrochemical impedance spectroscopy (EIS) was used to
153 study the anticorrosion performance of the composite material
154 Hot dip galvanized steel and Q235 carbon steel were used as
con-155 trol In the test, samples were immersed in the soil solution for
156
30 min The alternating current (AC) impedance spectra were
mea-157 sured by CS350 electrochemical workstation Acquisition
parame-158 ters including: the AC excitation signal, sine wave with the
159 amplitude of 10 mV and frequency, 0.01–100 kHz
160 Results and discussion
161 Interface analysis of the composite material
162
Fig 1shows the macro morphology and clad layer thickness of
163 the stainless steel/carbon steel composite material As shown in
164
Fig 1, the composite material exhibited an obvious clad layer
165 There was no gap between the interface and the layer combined
166 closely with the carbon steel substrate The clad layer was uneven
167 and the thickness was in the range of 0.8–1.9 mm
168 The metallographic microstructure of the composite material
169 interface is shown inFig 2 It can be observed fromFig 2that
170 the interface along rolling direction showed approximately linear
171 shape The interface was composed of the substrate, transition
172 zone and clad layer The substrate microstructure was ferrite and
173 pearlite The carbon potential of the substrate in heating is higher,
174 due to its larger carbon content than that of stainless steel As a
175 result, the smaller carbon atoms can diffuse to stainless steel by
176 the interstitial diffusion mode Thus, it was found that the
decar-177 bonized phenomenon existed in the near vicinity of the interface
178 (carbon steel side) in the composite material, and ferritic transition
179 zone with a thickness of about 90lm has been formed In cladding
180 material zone, there was no microstructure observed, because it
181 can’t be corroded by nitric acid alcohol solution
182 SEM micrograph and line scanning result of the composite
183 material interface after nitric acid alcohol solution erosion are
184 shown inFig 3 The SEM morphology also indicated that the
inter-185 face of the composite material contained matrix microstructure,
186 transition tissue and cladding tissue Microzone composition
anal-187 ysis showed that the elements both in stainless steel and carbon
188 steel diffused on different degree, so the diffusion layer formed
189
It can be seen from the changes of component curve that the
diffu-190 sion was continuous The diffusion ranges of element Cr, Ni, Mn
191 near interface led to little difference, which were around 5lm
192 When the sample was high temperature rolled, the element
con-193 centration gradient existed in both sides of the interface So, it
194 made these alloy elements diffuse under heat and force The results
195
of interface microstructure and microzone composition analysis
196 suggested that a metallurgical bonding was formatted between
197 the cladding and the substrates, resulting in strong bonding force
198
in the composite material Therefore, the prepared composite
199 material can meet the requirement of grounding material
2 W Shen et al / Results in Physics xxx (2017) xxx–xxx
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Trang 3200 Grounding resistance of the composite material
201
In order to confirm the prepared composite material can be
202 used as grounding material, the grounding resistances of the
com-203 posite material and hot dip galvanized steel in the soil around a
204 substation in Shaanxi Province were measured, and the results
205 are shown inFig 4 It can be seen fromFig 4that the grounding
206 resistance of the composite material was much less than that of
207 hot dip galvanized steel The grounding resistance of the two
sam-208 ples decreased with increasing depth of burial and then became
209 stable It might be caused by the increased touch area and close
210 contact between the sample and soil with the increase of the
211 depth The average grounding resistance of the composite material
212 was 89.64X, which was about 13/20 of hot dip galvanized steel
213 These results proved that the conductive property of the composite
214 material was much better than that of hot dip galvanized steel,
215 which can fulfill the requirement of conductivity for grounding
216 material The good conductive ability of the composite material
217 mainly arose from the large amount of conductive carbon steel
218 Thermal stability of the composite material
219 After the impact by fault current of 24.8 KA for 4 s, the tested
220 surface temperature of the stainless steel/carbon steel composite
Table 1
Contents of the prepared soil solution.
K +
Mg 2+
Ca 2+
Fe 2+
Al 3+
Fig 1 Macro morphology (a) and the clad layer thickness (b) of the stainless steel/carbon steel composite material.
Fig 2 The microstructure of the interface of the composite material.
Fig 3 SEM micrograph (a) and line scanning results (b) of the interface in the composite material.
Please cite this article in press as: Shen W et al Preparation and characterization of 304 stainless steel/Q235 carbon steel composite material Results Phys
Trang 4221 material was 1100°C After cooling to 800 °C, the macroscopic
222 detection results showed that there was no crack, pit, and bubble
223 appeared in the surface of the composite material, and no change
224 in interface could be observed It indicated the prepared composite
225 material exhibited good thermal stability, which can resist high
226 current impulse
mate-228 rial before and after fault current impulse As shown inTable 2,
229 the resistivity of sample 1 decreased after the fault current impact,
230 while that of sample 2 increased by 11.5% According to Q/GDW
231 465-2010 standard, the increase of the resistivity of grounding
232 material can’t exceed 15% after the impact of fault current
There-233 fore, the composite material can meet the demands for grounding
234 material
235 The good thermal stability in the composite material might be
236 caused by the metallurgical bonding formed in the hot rolling
pro-237 cess The formed transition region made the stainless steel layer
238 closely combined with the substrate Thus, the composite material
239 could not be damaged during the impact of fault current
240 Corrosion resistance analysis
241 The corrosion protection efficiency of the composite material in
242 soil solution was confirmed by the comparison of the
potentiody-243 namic polarization curves of bare Q235 carbon steel and hot dip
244 galvanized steel with that of the composite material and the values
245 of potentiodynamic polarization curves after Tafel fit, displayed in
246 Fig 5andTable 3 The corrosion potential of the composite
mate-247 rial in soil solution was higher than that of bare carbon steel, while
248 its current density was 2 order of magnitude lower than that of
249 bare carbon steel It means that the composite material had higher
250 corrosion resistance than bare carbon steel, which can provide
pro-251 tection for bare steel According to the electrochemical tests, the
252 protection performance against corrosion in soil solution can be
253 established in the following order: the composite material > hot
254 dip galvanized steel > Q235 carbon steel It suggests that the
com-255 posite material exhibited much improved anticorrosion property
256 than hot dip galvanized steel
257 The galvanized coating has provided cathodic protection for
258 carbon steel substrate by acting as sacrifice anode Galvanized
259 coating was corroded through anodic dissolution in the solution
260 containing Na+ and Cl However, 304 stainless steel showed
261 self-passivation in salt solution, due to the addition of passive alloy
262 elements such as Cr and Ni[16] In the measured curves, the anodic
263 polarization curve of galvanized steel hasn’t presented an obvious
264 passivation region, proving that galvanized coating was corroded
265
in the active state of anodic dissolution Nevertheless, the anodic
266 polarization curve of the composite material existed evident
passi-267 vated region It can limit corrosion ions to the carbon steel
sub-268 strate Thus, the passivative property of stainless steel could
269 effectively improved corrosion resistance than galvanized coating
Fig 4 The grounding resistance of the composite material and hot dip galvanized
steel.
Table 2
The grounding resistance of the composite materials at 21 °Cbefore and after the
impact of fault current.
length/cm
Average resistance/mX
Average resistivity/
mXm Sample 1 before
impact
Sample 1 after
impact
Sample 2 before
impact
Sample 2 after
impact
Fig 5 Potentiodynamic polarization curves of the composite material, hot dip galvanized steel, and Q235 carbon steel recorded in soil solution.
Table 3 The values of electrochemical potentiodynamic polarization curves after Tafel fit.
Samples Q235 carbon
steel
Hot dip galvanized steel
Composite material Corrosion rate/
(mm/a)
Corr i /(A/cm 2
) 1.14 10 5
7.653 10 6
8.452 10 7
Fig 6 Equivalent circuit used for impedance data modeling.
4 W Shen et al / Results in Physics xxx (2017) xxx–xxx
Please cite this article in press as: Shen W et al Preparation and characterization of 304 stainless steel/Q235 carbon steel composite material Results Phys
Trang 5270 The two time constant equivalent electric circuit[17]shown in
272 data and is adequate for interpreting the spectra for bare Q235
car-273 bon steel, hot dip galvanized steel and the composite material
dur-274 ing 0.5 h immersion in soil solution Rsol is the electrolyte
275 resistance R1and C correspond respectively to the coating
resis-276 tance and capacitance, both linked to the barrier properties
pro-277 vided by the coating R2 and CPE are the charge transfer
278 resistance and the double layer capacitance, related to the
corro-279 sion process
280 The electrochemical characteristics of the composite material
281 were studied using EIS, recorded after 0.5 h of immersion in soil
282 solution.Fig 7shows the complex plane impedance and the Bode
283 plots (log Z andh vs logf) for bare carbon steel, hot dip galvanized
284 steel and the composite material Compared with bare Q235
car-285 bon steel and hot dip galvanized steel, the composite material
286 showed at least 2 order of magnitude higher impedance, reaching
287 about 3 kXin soil solution (Fig 7b) For the composite and hot dip
288 galvanized steel, the phase angle dependence (Fig 7c) showed two
289 time constants, which correspond to the corrosion activity due to
290 the metal Fe dissolution and oxygen reduction or metal Zn
dissolu-291 tion The time constant appearing at high frequency is associated
292 with the responses of the electrolyte/layer interface, which has
293 described the dielectric and barrier properties of the layers The
294 time constant at lower frequencies relates to the corrosion process
295 at the electrolyte/substrate interface[18,19] The appearance of
296 second time constant indicated the outer layer of the composite
297 material and hot dip galvanized steel has been damaged by the
298 electrolyte
299 The values of EIS circuit parameters fitted according to the
elec-300 trical equivalent circuit are displayed inTable 4 The data clearly
301 revealed that the composite material had higher anti-corrosion
302 property than bare carbon steel and hot dip galvanized steel The
303 corrosion resistance can be established in the following order:
304 the composite > galvanized steel > carbon steel The higher
corro-305 sion resistance of the composite material than galvanized steel
306 may be caused by the following facts The zinc plating layer
pro-307 tected carbon steel substrate through the dissolution of metal Zn
308 After that, carbon steel experienced active corrosion And the
dis-309 solution of metal Fe into Fe2+was the main anodic reaction
How-310 ever, the stainless steel layer protected carbon steel substrate by its
311 self-passivation in soil solution The diffusion of oxygen across the
312 solution boundary layer played an important role in the cathodic
313 process
314 Conclusions
315 The stainless steel/carbon steel composite material was
pre-316 pared by modified hot-rolling process The 304 stainless steel
clo-317 sely combined with Q235 carbon steel through metallurgical
318 bonding, leading to the formation of transition region in the
com-319 posite material The composite material showed superior electrical
320 conductivity to hot dip galvanized steel underground Moreover,
Fig 7 Complex plane impedance (a), modulus impedance (b) and phase (c) plots of the composite material, hot dip galvanized steel and bare Q235 carbon steel after 0.5 h exposure to soil solution.
Please cite this article in press as: Shen W et al Preparation and characterization of 304 stainless steel/Q235 carbon steel composite material Results Phys
Trang 6321 the composite material had good thermal stability without any
322 surface crack and bubbling after fault current impact From the
323 electrochemical measurements, it was found that the corrosion
324 resistance of carbon steel was significantly improved by the
stain-325 less steel layer in soil solution The composite material had an
326 average grounding resistance of 89.64X, an impedance value of
327 about 3.09 104Xand a corrosion rate of 9.78 10 3mm/a, 2
328 order of magnitude lower than that of hot dip galvanized steel
329 Thus, stainless steel/carbon steel composite material could be used
330 as grounding materials, to potentially substitute hot dip galvanized
331 steel
332 Acknowledgments
333 This work was supported financially by Dr Start-up funds of
334 Xi’an University of Technology, Science Research Project of Xi’an
335 University of Technology (2015TS001), Key Laboratory Project of
336 Education Department of Shaanxi Province (15JS080), and Science
337 and Technology Co-ordination & Innovation Key Laboratory Project
338 of Shaanxi Province (2014SZS09-Z02)
339 References
340 [1] Khan Y, Pazheri FR, Malik NH, Al-Arainy AA, Qureshi MI Novel approach of
341 estimating grounding pit optimum dimensions in high resistivity soils Electr
342 Power Sys Res 2012;92:145–54.
343 [2] He JL, Zeng R Grounding technology of electric power system Beijing: Science
344 Press; 2007.
345 [3] Lim SC, Gomes C, Kadir MZAA Electr Power Energy Sys 2013;47:117–28.
346 [4] Kostic VI, Raicevic NB A study on high-voltage substation ground grid integrity
347 measurement Electr Power Sys Res 2016;131:31–40.
348 [5] Yan FJ, Li XG Corrosion and protection of grounding net in electric power
349 system, Shandong Electric Power Shandong Electr Power 2007;11:9–13 (in
350 Chinese).
351 [6] Tian H Anti-corrosion technology to earthing network system Dalian: Dalian
352 Jiaotong University; 2008.
353 [7] Kirkpatrick EL Conflict between copper grounding and CP in oil & gas
354 production facilities Mater Perform 2002;8:22–35.
355 [8] Zheng MC, Li JH, Nie XH, Li BW, Tai C Corrosion behavior of galvanized Q235
356 steel for grounding in acid soils J Chin Soc Corros Prot 2015;35:27–32 (in
357 Chinese).
358 [9] Park JH, Kim WS, Jo DH, Kim JS, Park JM Effect of Ce conversion underlayer
359 coating on the photo-catalytic activity of TiO 2 sol-gel film deposited on hot-dip
360
GI J Ind Eng Chem 2014;20:1965–72.
361 [10] Le Manchet S, Landoulsi J, Richard C, Verchere D Study of a chromium-free
362 treatment on hot-dip galvanized steel: electrochemical behavior and
363 performance in a saline medium Surf Coat Technol 2010;205:475–82.
364 [11] Maruya T, Takeda H, Horiguchi K, Koyama S, Hsu KL Simulation of steel
365 corrosion in concrete based on the model of macro-cell corrosion circuit J Adv
366 Concr Technol 2007;5:343–62.
367 [12] Lindscy T National electrical grounding research project Technical report The
368 Fire Protection Research Foundation; 2007.
369 [13] Hermas AA, Morad MS A comparative study on the corrosion behavior of 304
370 austenitic stainless steel in sulfamic and sulfuric acid solutions Corros Sci
371 2008;50:2710–7.
372 [14] Molchan IS, Thompson GE, Walton J, Skeldon P, Tempez A, Legendre S.
373 Passivation behavior of 304 stainless steel in an ionic liquid with a fluorinated
374 anion Appl Surf Sci 2015;357:37–44.
375 [15] Zhou PP, Wang S, Li ZZ, Zhang B, Zeng R Review of corrosion resistant metals
376 for grounding Electr Power Cons 2010;31:50–4 (in Chinese).
377 [16] Zheng ZB, Zheng YG Erosion-enhanced corrosion of stainless steel and carbon
378 steel measured electrochemically under liquid and slurry impingement.
379 Corros Sci 2016;102:259–68.
380 [17] Li GZ, Feng LJ, Tong PR, Zhai Z The properties of MWCNT/polyurethane
381 conductive composite coating prepared by electrostatic spraying Prog Org.
382 Coat 2016;90:284–90.
383 [18] Shen WN, Feng LJ, Liu X, Luo H, Liu Z, Tong PR, Zhang WH Multiwall carbon
384 nanotubes-reinforced epoxy hybrid coatings with high electrical conductivity
385 and corrosion resistance prepared via electrostatic spraying Prog Org Coat
386 2013;90:139–46.
387 [19] Hang TTX, Nam TA, Oanh VK, Jorcin JB, Pebere N Corrosion preparation of
388 carbon steel by an epoxy containing organically modified clay Surf Coat
389 Technol 2007;201:7408–15.
390
Table 4
Parameters of the electrical equivalent circuit for bare carbon steel, hot dip galvanized
steel and the composite material.
Samples Q235 carbon
steel
Hot dip galvanized steel
Composite material
C 5.099 10 9
57.307 10 9
1.273 10 8
CPE 3.113 10 4
9.173 10 5
4.831 10 5
6 W Shen et al / Results in Physics xxx (2017) xxx–xxx
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