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Sulfuric Acid and Hydrochloric AcidDew-point Corrosion-resistant Steel

Technical Document

http://www.nssmc.com/

A012en_01_201210f

2-6-1 Marunouchi, Chiyoda-ku,Tokyo 100-8071 JapanTel: +81-3-6867-4111

2007,2012 NIPPON STEEL & SUMITOMO METAL CORPORATION

Sulfuric Acid and Hydrochloric Acid Dew-point Corrosion-resistant SteelS-TEN

TM

TM


2/8

1

Flue-gas temperature130150

S-TEN is a sulfuric acid and hydrochloric acid dew-point corrosion-resistant steel developed by NSSMCusing proprietary technology.

1. Characteristics of S-TEN

Recently, environmental issues are becoming pressing concerns. In parallel with

this, construction of tall smokestacks, air preheaters, electrostatic precipitators

and flue-gas desulfurizers and other treatment equipment has shown great

strides.

Meanwhile, the mainstay industrial fuel has shifted from conventional coal to

heavy oil, which poses a large problem of corrosion at the low-temperature

section of flue-gas treatment equipment (in particular, air preheaters, flues and

smokestacks) due to sulfur oxides.

The low-temperature section corrosion is the corrosion caused by high-

temperature, highly-concentrated sulfuric acid, called sulfuric acid dew-point

corrosion. This kind of corrosion differs from general atmospheric corrosion and

causes heavy corrosion of not only ordinary steel but even stainless steel.

Further, because of the remarkable technological developments recently

seen in dioxin countermeasures, flue-gas temperatures are increasingly being

reduced from previous levels.

In conventional facilities where, formerly, only sulfuric acid dew-point corro-

sion occurred, there are now cases of hydrochloric acid dew-point corrosion

that is caused by lower flue-gas temperatures resulting from remodeling with

countermeasures against dioxins.

Developed to solve these problems is S-TEN steel for welded structures,highly resistant to sulfuric acid and hydrochloric acid dew-point corrosion.

Hydrochloric acidSulfuric acid

Chlorides

Heavy-oil firing Hydrochloric acid

Coal firing

Waste incineration

Excellent

Flue-gas temperature180

136

72

Rapid cooling and loweringof temperature of flue gasfor reducing dioxins

Sulfuric Acid and Hydro-chloric Acid Dew-pointCorrosion

Fig. 1.1 Waste Incineration Facility: Mechanism of SulfuricAcid and Hydrochloric Acid Dew-point CorrosionOccurring in Flue-gas Treatment System

Photo 1.1 Example of Hydrochloric Acid Dew-pointCorrosion in Internal Cylinder of Stack

High

Low

Steelplatesurfacetemperatu

re

Conventionalflue-gas

treatmentequipment

Condensation

ofsulfuricacid

Occurrence ofhydrochloric acid

dew-point corrosion!

Sulfuric Acid and Hydrochloric AcidDew-point Corrosion-resistant Steel

Technical Document

Features

S-TEN exhibits the best resistance to sulfuric acid and hydrochloric

acid dew-point corrosion found in the flue-gas treatment equipmentused with coal-fired boilers, waste incineration plants, etc. (Thissteel has the finest application record in the field of thermal power

generation and waste incineration plants, according to surveysconducted by NSSMC)

S-TEN exhibits the best resistance to sulfuric acid and hydro-chloric acid dew-point corrosion found in hydrochloric acid pick-ling, industrial sulfuric acid and other tanks.

S-TEN was awarded the Ichimura Industrial Award AchivementAward in 2007

S-TEN has strength, workability and weldabilitythat are comparable to ordinary steel.

S-TEN is more economical than stainless steel.

rolled sheets (plates), cold-rolled sheets and pipe andtubes to welding materials.

Hot-rolled sheets (plates) conform to JIS G 3106 SM400A (S-TEN 1)and SM490A (S-TEN 2).

S-TEN products are easily available because they areconstantly stocked by retailers.

CONTENTS

1. Characteristics of S-TEN

Sulfuric Acid and Hydrochloric Acid Dew-point Corrosion

Sulfuric Acid Dew-point Corrosion

Advantages of S-TEN

Examinations in Applying S-TEN

Application Examples for S-TENPrecautions in the Use of S-TEN

Field Test Results of S-TEN

2. Specifications and Available Sizes of S-TEN

Specifications of S-TENAvailable Sizes for S-TEN

3. Characteristic Properties of S-TEN (Examples)

Chemical Composition and Mechanical Properties

High-Temperature Characteristics

Physical Properties

Corrosion Resistance4. Welding of S-TEN

Welding Materials

Welding Characteristics

Sulfuric Acid and Hydrochloric Acid Resistance ofWelded JointsGalvanic Corrosion in Corrosive Atmosphere

Property Qualification Test Results

5. Application Examples

1

2

3

4

7

8

8

12

13

14

14

15

15

17

18

19

20

20

21

In the case of flue-gas composition (SO3 : 6 ppm, HC: 300 ppm, H2O: 30%)

NSSMC:Nippon Steel & Sumitomo Metal Corporation

Notice:While every effort has been made to ensure the accuracy of the information contained within this publication, the use of the information is at the readers risk and no warranty is

implied or expressed by Nippon SteelSumitomo Metal Corporation with respect to the use of the information contained herein. The information in this publication is subject to change or

modification without notice. Please contact the NipponSteelSumitomo Metal Corporation office for the latest information.

Please refrain from unauthorized reproduction or copying of the contents of this publication.

The names of our products and services shown in this publication are trademarks or registered trademarks of Nippo n SteelSumitomo Metal Corporation,affiliated companies,or third parties

granting rights to NipponSteelSumitomo Metal Corporation or affiliated companies.Other product or service names shown may be trademarks or registered trademarks of their respective owners.

S-TEN offers a rich product line ranging from hot-

Recentflue-gastreat-

mentequipment

Occurrence ofsulfuric acid dew-point corrosion!

Condensa-

tion

ofhydro-

chloricacid

TM


3/8

Fig. 1.2 Relation between Sulfur Content and SO2Content inCombustion Gas

Fig. 1.4 Relation between SO3Content in Combustion Gasand Dew Point

Fig. 1.5 Relation between Wall Surface Temperature andSulfuric Acid Concentration

Fig. 1.3 Relation between Sulfur Content in Fuel and SO2toSO3Conversion Rate

Sulfuric Acid Dew-point Corrosion

Because sulfur is contained in heavy oil used as fuel, com-

bustion of heavy oil generates sulfur oxides (SO x), an

extremely small portion of which becomes SO 3.

Fig.1.2 shows the relation between the sulfur content of

fuel and the amount of SO2generated, and Fig.1.3 the con-

version rate from SO2to SO3. When high-sulfur heavy oil

containing about 3% sulfur is burnt, about 0.15% SO 2is

generated (Fig.1.2), about 2% or about 30 ppm of which

becomes SO3(Fig.1.3).

When the flue gas temperature reaches the dew point

or lower or the gas contacts the lower-temperature wall

surface, SO3and H2O in the gas combine to produce

highly-concentrated sulfuric acid.

Fig.1.4 shows the relation between the SO3inclusion

and the dew point in the case of 10% of H 2O concentration

in the gas (normal heavy-oil combustion gas).

In the case of about 30 ppm of SO 3 inclusion, the dew

point reaches 130150, and at a temperature below this

level sulfuric acid dew-point corrosion occurs.

Fig.1.5 shows the relation between the gas or wall sur-

face temperature at the time of dew condensation and the

sulfuric acid concentration. Sulfuric acid with a maximum

concentration of 80% is produced.

Advantages of S-TEN

Ordinary or stainless steel cannot be used in applications in

which sulfuric acid dew-point corrosion is a governing

factor. Neither can weathering steels such as COR-TEN

provide satisfactory performance in these applications.

The material appropriate for these applications is S-TEN.

Fig.1.6 shows the results of sulfuric acid immersion

tests conducted under the conditions of temperature and

concentration obtained from Fig.1.5.

Extremely severe corrosion occurs under the conditions

of 70and 50% H2SO4. However, under such conditions,

S-TEN exhibits corrosion resistance about five times

greater than both ordinary steel and COR-TEN and about

10 times that of stainless steel. It is in such severe applica-

tion environments that S-TEN shows the best performance.

In this way, corrosion caused by high-temperature,

highly concentrated sulfuric acid differs from common atmo-

spheric corrosion. Not only ordinary steel but stainless steel,

as well, is heavily corroded in environments of high-

temperature, highly concentrated sulfuric acid (in some

cases, exceeding a corrosion rate of 5 mm/year).

Fig.1.7 shows the clear differences in corrosionresistance demonstrated by ordinary steel, COR-TEN, and

S-TEN during long-term tests conducted in actual 60%

H2SO4or higher environments at 80with sufficient oxygen

to produce sulfuric acid dew-point corrosion.

Fig. 1.6 Sulfuric Acid Immersion Test Results under theAtmosphere-solution Equilibrium State of SulfuricAcid and Hydrogen Fig. 1.7 Corrosion Mass of Steel in H2SO4

Chemical composition(%)

1800.01 0.10 1.0 10 100 1,000

200

220

240

260

280

300

320

340360

380

400

420

Dewpoint(F)

SO3content(ppm)

S content (vol%)

SO2+S

O3

(%)

SO3

0 1 2 3 4 50

2

4

6

0

20

40 60 80 100 120 140 160

60

80

100

40

Wall surface temperature()

Sulfuricacidconcentration

(%)

00 1 2 3 4 5

0.1

0.2

0.3

SO2

(%)

S content (vol%)

0

2

4

6

8

O2

(%)

020 40 60 80 100

200

400

600

SUS 430

SUS 410

SUS 304SUS 316

S-TEN 1

S-TEN 2

Corrosionmas

s(mg/cm)

Test hours (hrs)

SS 400

COR-TEN O

0

10

20

30

40

50

60

70

80

90

100

150

200

250

Corrosionrate

(mg/cm

2/hrs

)

20

10

40

20

60

40

70

50

80

60

100

70

120

75

140

80

Temperature(C)

H2SO4concentration(%)

Rotating immersion tests

Test specimen speed32.8 m/min.

Testing conditions Temperature125 Concentration75%

H2O10%

(150)

(100)

(200)

SUS 430

SUS 410

SUS 304

SS 400

SUS 316

COR-TEN O

(6 hours)

S-TEN 1

S-TEN 2

0

10

20

30

40

50

60

70

80

90

100

150

200

250

Corrosionrate

(mg/cm/hrs

)

20

10

40

20

60

40

70

50

80

60

100

70

120

75

140

80

Temperature ()

H2SO4concentration(%)

SUS 430

SUS 410

SUS 304

SS 400

SUS 316

COR-TEN O

(6 hours)

S-TEN 1

S-TEN 2

1. Characteristics of S-TEN 1. Characteristics of S-TEN

0.10

0.07

0.08

0.08

0.16

0.030.10

0.09

0.38

0.51

0.58

0.68

0.03

0.280.21

0.46

0.012

0.006

0.008

0.008

0.013

0.0090.012

0.017

0.46

0.34

1.42

1.62

0.23

0.910.75

0.38

0.019

0.040

0.029

0.030

0.008

0.0110.014

0.110

0.12

0.11

0.20

0.24

0.08

0.270.36

0.32

0.19

0.27

9.21

11.72

0.30

12.53

17.29

18.56

17.05

0.63

0.52

0.10

Mo2.20

Ti0.04

C Si Mn P S Cu Ni Cr Sb Others

Table 1.1 Chemical Composition of Test Specimens

Grade(equivalent)

SUS 410 (13%Cr) (equivalent)

SUS 430 (18%Cr) (equivalent)

SUS 304 (18Cr-8Ni) (equivalent)

SUS 316 (18Cr-12Ni-2Mo)(equivalent)

SS 400

S-TEN 1

S-TEN 2

COR-TEN O

2 3


4/8


Table 2.1

Table 2.2

Table 2.3 Cold-rolled Sheets and Bars


Specifications of S-TEN


Notes 1) Bars: No. 2 for the diameters 25 mm or less; No. 14A for the diameters more than 25 mm

Table 2.5 ERW Pipes and Tubes

Available Sizes for S-TEN

Cold-rolled Sheets(S-TEN 1, S-TEN 2)

Notes 1) Hot-rolled sheets and plates (all plates; specification required for sheet) conform to JIS G 3106 (S-TEN 1:SM400A; S-TEN 2: SM490A). JIS is inscribed on the steel product inspection sheet when specified.

2) ERW pipe and tubes are registered in the technical standards for thermal power generation facilities (METIKA-STB380J2) and ASME Code Case 2494.

Note) For this size range, please consult us in advance.

Table 2.4 Hot-rolled Sheets and Plates, and Spiral Welded Pipe

Notes 1) Figures in the table show the maximum length.2) Minimum length: 3 m for the thicknesses 6 mm or more; 1.5 m for the thicknesses less than 6 mm3) For this size range and the plate thicknesses up to 50 mm, please consult us in advance.

Note)The following sizes are subject to negotiation. Available products are SAW pipe (BR or SP). Outside diameter (nominal diameter A):138.9125, 165.2150, 216.3200, 267.4250, 318.5300, 355.6350, 406.4400; maximum outside diameter: 2,500 mm

0.6, 0.7

0.8, 0.9, 1.0, 1.2, 1.6

2.0, 2.3

400

290 530 1,470 1,845

600 800 1,000 1,200 1,400 1,600 1,800 2,000

Length0.794.92m 0.8

1,540

16

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

600 2,400 4,000 4,5003,200 3,400 3,6003,0001,2501,350 1,550

3.6

6.0

9.7 16

20

23

16

PlateThickness (mm)

Width (mm)

PlateThickness (mm)

Width (mm)

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 25.4

19.0

21.7

25.4

27.2

31.8

34.0

38.1

42.7

45.0

48.6

50.8

54.0

57.0

60.5

76.2

88.9

101.6

114.3

15

20

25

32

40

50

65

80

90

100

4.5

5.56.8

7.9

8.5

8.9

Wall thickness(mm)Outsidediameter (mm)

Nominaldiameter A

ERW pipes and tubes(cold-finished)

ERW pipes and tubes(as-rolled)

Hot-rolled Sheets and Plates(S-TEN 1, S-TEN 2)

Pipes and Tubes (S-TEN 1)

Grade Designation

Thicknessdiameter(mm)Product

Cold-rolled sheet

Hot-rolled sheet and plate1)

ERW pipe and tube2)Large-diameter pipe

Cold-rolled sheet

Hot-rolled sheet and plate1)

Bar and bar-in-coil

Grade

S-TEN 1

S-TEN 2

Chemical Composition

Notes 1) 2.5CMn

2)Alloying elements other than those shown in the table may added as occasion demands

Grade

S-TEN 1

S-TEN 2

Mechanical Properties

Notes 1)Applied in the case of production as JIS G 3106 (applied in all production of plates)

Grade

Grade

Grade

S-TEN 1

S-TEN 1

S-TEN 1

Thickness(mm)

Yield point(N/mm)

230

Tensile strength(N/mm)

Thickness(mm)

Yield point(N/mm)


380

Elongation(%)

35

Test specimen(JIS)

Elongation(%)

Test specimen(JIS)

Thickness(mm)

Yield point(N/mm)


Elongation(%)

Test specimen(JIS)

No. 11 or 12

S-TEN 2

S-TEN 2

245

400510

490610

23

23

18

23

22

22

22

17

22

21

No. 5

No. 5

No. 1A1)

No. 5

No. 1A1)

No. 5

No. 5

No. 1A1)

No. 5

No. 1A1)

5

16

20.2

5

16

20.2

235

325

315

23

22

No. 5

No. 5 1)400

440

235

325

Outside dia.: 19.0114.3

Outside dia.: 4002,500

Wall thickness: 2.08.9

Wall thickness: 6.020

C

0.14

0.14

Si

0.55

0.150.55

Mn

1.601)

1.60

P

0.025

0.035

S

0.025

0.035

Cu

0.250.50

0.250.50

Cr

0.501.00

Ti

0.15

Sb

0.15

0.6

1.6

0.6

2.0

t 2.0

t 2.5

t 3.0

t 4.5

t 5.0

t 6.0

t 7

t 8

t 9

t 12

t 20

1.6

2.0

2.5

3.0

4.5

5.0

6

7

8

9

12

t2.3

t20

t2.3

t20

t38

1312


5/8

15

3. Characteristic Properties of S-TEN(Examples)

High-temperature Short-timeStrengthResults of high-temperature tensile

tests are shown in Fig. 3.1.

Fig. 3.1 High-temperature Tensile Test Results


Table 3.3 Cold-rolled Sheets

Tensile test

Table 3.4 ERW Pipe s and Tubes

Tensile test

3. Characteristic Properties of S-TEN(Examples)

Physical Properties Physical properties are shown in Table 3.5. Specific heat, thermal conductivity andthermal expansion coefficient of S-TEN are similar to those of SS400, SM400A,

SM490C, etc.

Table 3.5 Physical Properties

High-temperatureCharacteristics

Table 3.1 Chemical Composition (Example)

Measurement method Youngs modulus: Resonance method; Specific heat and thermal conductivity: Laser flash method; Thermal expansion coefficient:Measurement of thermal expansion

Table 3.6 Chemical Composition of Test Specimens for Hydrochloric Acid Resistant and High-temperature Oxidation Tests(Figs. 3.23.5)

Corrosion Resistance

Hydrochloric Acid ResistanceCorrosion caused by hydrochloric acid gas contained in the exhaust gas of garbage

disposal incinerators has recently become a social problem. S-TEN 1 has greater

resistance to hydrochloric acid corrosion than ordinary steel, and thus permits effec-

tive application in this field (for example, hydrochloric acid tanks for galvanizing). Figs.3.23.5 show the results of tests pertaining to hydrochloric acid corrosion.

1)S-TEN 1 exhibits corrosion resistance 510 times that of ordinary steel.2)In dilute hydrochloric acid (about 3% or less), the corrosion rate of S-TEN is higher

than that of SUS, and thus the use of S-TEN in such environments is not recom-

mended.

3)In hydrochloric acid with a concentration of 10% or more, S-TEN 1 exhibits highcorrosion resistance.

4)As the temperature and concentration of hydrochloric acid increases, S-TEN 1exhibits higher corrosion resistance.

5)Please pay attention to the fact that when alien substances are mixed in the acid,characteristic properties may vary in some cases.

Grade

S-TEN 1

S-TEN 2

SS 400

Chemical composition (%)

Table 3.2 Hot-rolled Sheets and Plates

Tensile test

Test specimen: JIS No. 5

Strength(N/mm

2)

0100 200 300 400 500 600

100

200

300

400

500

Test temperature ()

S-TEN 1

S-TEN 2

Tensile strength

Yield strength

Chemical Compositionand Mechanical Properties

Product

Platethickness

(mm)

Platethickness

(mm)

Outside

diameter

Wall thickness

(mm)

Youngs modulus

(GPa)

Specific heat

(J/kgK)

Thermal

conductivity

(W/mK)

Thermal expansion

coefficient 20T(10-6/)

---

-

Chemical Composition

Mechanical Properties

C

0.040.04

0.04

0.04

0.09

0.12

0.14

Si

0.300.30

0.28

0.20

0.24

0.26

0.22

Mn

0.910.91

1.00

1.00

0.76

0.76

0.75

P

0.0150.015

0.012

0.011

0.017

0.016

0.018

S

0.0100.010

0.012

0.010

0.013

0.007

0.012

Cu

0.300.30

0.28

0.27

0.32

0.28

0.34

Cr

0.68

0.70

0.65

Others

Sb: 0.10Sb: 0.10

Sb: 0.09

Sb: 0.10

Ti: 0.03

Ti: 0.03

Ti: 0.03

Grade

S-TEN 1

S-TEN 2

Grade

S-TEN 1

S-TEN 2

Grade Grade

Grade

S-TEN 1

S-TEN 1

S-TEN 1

S-TEN 2

S-TEN 2

Cold-rolled sheetHot-rolled medium plate

Plate

ERW pipe and tube

Cold-rolled sheet

Hot-rolled medium plate

Plate

2.3

6.012.0

16.0

2.3

6.0

9.0

13.0

345

383382

368

440

440

420

410

470

458452

441

540

530

520

510

36

3842

47

33

35

39

41

Yield point(N/mm)

Yield point(N/mm)



Elongation(%)

Elongation(%)

Yield point(N/mm)


Elongation(%)

1.2

1.60.8

1.2

295

305380

380

410

440490

490

36

3632

32

48.63.5

89.15.0

298

293

403

418

61

41

25100

200

300

400

500

25

100

200

300

400

500

Temperture

()

207.4203.7

198.3

192.0

184.0

211.0

207.0

202.0

196.0

188.0

179.0

0.450

0.491

0.532

0.456

0.486

0.520

0.553

0.590

0.644

44.2

45.5

36.8

45.1

41.2

40.8

40.2

37.7

34.1

12.8

13.2

13.6

14.0

12.8

13.1

13.5

13.8

14.2

Weather ResistanceS-TEN surpasses ordinary steel in weather resistance:S-TEN 1: About 2 times (similar to Cu-containing steel)

S-TEN 2: 46 times (similar to COR-TEN 490)

C

0.02

0.09

0.15

Si

0.26

0.24

0.14

Mn

0.90

0.69

0.70

P

0.011

0.009

0.014

S

0.010

0.014

0.005

Cu

0.27

0.29

0.01

Cr

0.54

Sb

0.09

Ti

0.03

1514


6/8

The carbon and mangan ese contents of S-TEN are kept low to

secure high corrosion resistance. Therefore, S-TEN offers

excellent weldability and can be welded under the same condi-

tions as those for ordinary steel of the same strength level.

However, because sulfuric acid and hydrochloric acid

dew-point corrosion resistance similar to that of the base

metal is required for welds, it is necessary to use welding

materials for exclusive use for S-TEN.

Welding Materials

Welding Materials As the welding material for exclusive use for S-TEN, Nippon Steel & Sumikin WeldingCo., Ltd.* supplies the following products.

Chemical Composition and Mechanical Properties of Various Welding Materials (Example)

Welding Materials for Dissimilar Welding with Stainless Steels(Example)

4. Welding of S-TEN3. Characteristic Properties of S-TEN(Examples)

Aftertest

Beforetest

S-TEN 1

S-TEN 1 STB 340 SUS 316L SUS 304

SUS 304SS 400

Appearance of Various Steel Products afterAccelerated Corrosion Tests

Photo 3.1 10.5% Hydrochloric Acid, 60, 72 Hrs

Photo 3.2 10.5% Hydrochloric Acid, 80, 144 Hrs

( Initial size of test specimen: 4t2525 mm)

Table 4.3

Table 4.4

Fig 3.6 Sulfuric Acid Resistance of Various Steel Products (50%, 70, H2SO4)

Corrosionrate(g/m2/hrs)

0

S-TEN 1 S-TEN 2 SUS 304 SUS 316L SS 400

100

200

300

400

500

700

600

800

00 5 10 15 20

(Temperature: 80, 6 hrs)

Corrosionrate(mg/cm

2/hrs)

HCconcentration(%)

10

5

20

15

00

30

15

60

45

5 10 15 20


Corrosionrate(mg/cm

2/hrs)

HCconcentration(%)

00

4

3

2

1

5 10 15 20


Corrosio

nrate(mg/cm

2/hrs)

HCconcentration(%)

SS 400

S-TEN 1

SS 400

S-TEN 1

00

0.4

0.6

0.2

5 10 15 20


Corrosio

nrate(mg/cm

2/hrs)

HCconcentration(%)

SUS 316L

SUS 304S-TEN 1

SUS 316L

SUS 304

S-TEN 1

Table 4.1

*Inquiry: Nippon Steel & Sumikin Welding Co., Ltd.Shingu Bldg.,2-4-2 Toyo, Koto-ku,Tokyo 135-0016

Tel: +81-3-6388-9065 Fax: +81-3-6388-9088

Fig. 3.5 Relation between Hydrochloric Acid Concentrationand Corrosion Rate

Fig. 3.3 Relation between Hydrochloric Acid Concentration and Corrosion Rate

Sulfuric Acid Resistance



Notes 1) Low-hydrogen type 2) Lime titania type 3) Cord arc weldeing wire (Flux) 4) Cord arc weldeing wire (Metal)

Brand

Welding

method

Welding

method

Brand C Si Mn P S

C Si Mn P S

Cr Ni YS(N/mm)

TS(N/mm)

EL(%)

vE0(J)

YS(N/mm)

TS(N/mm)

EL(%)

vE0(J)

Cu Cr Sb

0.04

0.05

0.06

0.05

0.04

0.02

0.02

0.62

0.50

0.15

0.60

0.38

0.28

0.31

0.50

0.48

0.56

1.41

0.81

0.84

1.12

0.009

0.012

0.014

0.012

0.016

0.008

0.013

0.004

0.006

0.011

0.013

0.013

0.011

0.016

0.42

0.20

0.23

0.39

0.35

0.29

0.28

0.73

0.79

0.74

0.08

0.10

0.10

0.10

471

481

463

581

512

386

389

568

550

532

640

585

465

486

31

29

28

27

27

36

30

165

203

112

71

52

303

73

*20

SMAW

SAW

FCAW

GMAW

GTAW

0.06

0.06

0.03

0.05

0.05

0.33

0.45

0.65

0.35

0.40

1.51

1.64

1.54

1.74

1.65

0.020

0.020

0.023

0.021

0.020

0.006

0.010

0.009

0.007

0.006

24.2

24.0

24.4

23.6

23.8

13.2

13.5

12.7

13.3

12.4

460

375

429

447

517

582

558

566

618

620

37

38

37

33

34

64

89

36

92

166

SMAW

GMAW

GTAW

SAW

S-TEN 2

S-TEN 1

Grade

Kind of shielding material

Gas shielded metal arc welding

ST-16Cr1)

(JIS Z 3212 E5716)

MAG welding(GMAW)

Shielded metal arc welding

(SMAW)

Submerged arc welding

(SAW)

ST-16M1)

(JIS Z 3211 E4916U)

ST-03Cr2)

(JIS Z 3212-E4940-G)

SF-1ST 3)

(JIS Z 3313 T49J0T1-1CA-UH5)

FC-23ST3)(JIS Z 3313 T49J0T1-1CA-U)

FCT-1ST4)(JIS Z 3313 T49J0TG-1GA-U)

TIG welding(GTAW)

YFC-1ST

YF-15B(JIS Z 3183 S502-H)

ST-16M

ST-16Cr

ST-03Cr

SF-1ST

FC-23ST

FCT-1ST

YFC-1ST

YF-15B

309R

Y-309BF-300M

SF-309L

YM-309

YT-309

*

1716


7/8

4. Welding of S-TEN 4. Welding of S-TEN

Photo 4.1 Corrosion Conditions of S-TEN 1 Weld Joint

SS 400(S-16)

S-TEN 1(*ST-16)

S-TEN 1(ST-16M)

Corrosion rate (mm/yr/side)

20 4 6 8

BM

WM

BM

WM

BM

WM

Sulfuric acid and hydrochloric acid immersion test of welded joints was

conducted to determine the sulfuric acid resistance of welded joints, the results

of which are shown below.

The test results indicate that the welded joints made using welding rods f or

exclusive use for S-TEN exhibit corrosion resistance similar to that of the base

metal. But in the case of using welding rods for use for mild steel, the results

clearly indicate that the welded joints only are severely corroded.

Welding Characteristics Maximum hardness tests and y-groove weld cracking tests prescribed by JISwere performed to confirm the weldability of S-TEN. S-TEN 1 and 2 having the

characteristics shown in Tables 4.5 and 4.6 were used as the test specimens.

Table 4.5 Chemical Composition of Test Specimens

Table 4.7 Maximum Hardness Test Results

Table 4.6 Mechanical Properties of Test Specimens

Tensile test specimen: JIS No. 5

Welding conditions: Welding Electrodes 4 mm in dia.; current 170 A; voltage 24 V; speed 150 mm/min

Welding conditions: Welding Electrodes 4 mm in dia.; current 170 A; voltage 24 V; speed 150 mm/min

Surface crack rate (%)

Fig. 4.1 Configuration of y-groove Weld Cracking Test Specimen

BM BMWM

BM BMWM

BM BMWM

SS 400S-16

Base metalWeld metal

S-TEN 1*ST-16

S-TEN 1ST-16M

crevice corrosion

(unit: mm)

25

4

60

10

A-A B-B

20.2

60 60

200

150

8

8

Restraint welding

Test welding

23 23

60 80 60

A B

A B

ST-16M (Welding rod for exclusive use for S-TEN)Basemetal (S-TEN 1)

16 (Low hydrogen-type welding rod for mild steel)Basemetal (SS 400)

16 (Low hydrogen-type welding rod for mild steel)Basemetal (SS 400)

ST-16M (Welding rod for exclusive use for S-TEN)Basemetal (S-TEN 1)

Fig. 4.2 Configuration of Sulfuric Acid Immersion Test Specimen

Sulfuric acid: 50% sulfuric acid70Immersion for 24 hrsHydrochloric acid : 10.5% hydrochloric acid

80Immersion for 24 hrs

Field Test ResultsImmersion condition: 17.5% hydrochloric acid, 32, fully immersed

Immersion period: 4 months

Fig. 4.3 Test Results for Weld Joint Test Specimens Immersed in Hydrochloric Acid Pickling TankPhoto 4.2 Cross Sections of Joint Specimens Immersed in Hydrochloric Acid Pickling Tank for 4 Months

BM: Base metal: WM: Weld metal *ST-16: Brand name of conventionalweld material for S-TEN (production discontinuation)

BM: Base metal: WM: Weld metal *ST-16: Brand name ofconventional weld material for S-TEN (production discontinuation)

Sulfuric Acid andHydrochloric AcidResistance of WeldedJoints

Example of S-TEN 1Immersion tests were conducted using the test specimen,consisting of both base metal and weld metal, shown in

Fig. 4.2 and under the conditions shown in Photo 4.1.

Cross sections of the corroded specimen are shown in

Photo 4.1.

y-groove Cracking TestTo determine the crack sensitivity of welds, the test was conducted using the

test specimens, shown in Fig. 4.1, in accordance with JIS Z 3158 (Method of

y-Groove Cracking Test). The test results are shown in Table 4.8.

Maximum Hardness TestTable 4.7 shows the results of HAZ maximum hardness tests in accordance

with JIS Z 3101 (Testing Method of Maximum Hardness in Weld Heat-

Affected Zone).

Grade

Grade

S-TEN 1

S-TEN 2

S-TEN 1

S-TEN 2

Grade

S-TEN 1

S-TEN 2

Grade

S-TEN 1

S-TEN 2

Thickness(mm)

16

16

Thickness(mm)

16

16

Chemical composition (%)

C

0.04

0.09

Si

0.28

0.21

Mn

1.00

0.74

P

0.012

0.023

S

0.012

0.010

Cu

0.28

0.35

Cr

0.70

Ti

0.02

Sb

0.09

Tensile test

Yield point (N/mm)

368

380

Tensile strength (N/mm)

441

500

Elongation (%)

47

43

Maximum hardness (Hv)

189242

Initial temperature of specimen

Room temperatureRoom temperature

Thickness (mm)

1616

Section crack rate (%) Root crack rate (%)Initial temperatureof specimen ()

Table 4.8 y-groove Weld Cracking Test Results

Thickness(mm)

16

16

0

25

0

25

1

0

0

0

0

2

0

0

0

0

3

0

0

0

0

Average

0

0

0

0

1

0

0

0

0

2

0

0

0

0

3

0

0

0

0

Average

0

0

0

0

1

0

0

0

0

2

0

0

0

0

3

0

0

0

0

Average

0

0

0

0

1918


8/8

5. Application Examples

Waste melting furnace

Economizer and air preheater of thermal power plant

Tubes for air fin cooler

Fin tubes

4. Welding of S-TEN

(SS 400)Distance from weld (mm)

(S-TEN 1)Distance from weld (mm)

0

0.1

0.2

0.3

0.4

400 300 200 100 0 0 100 200 300 400

Corrosionm

ass(mm)

400

SS 400

400

S-TEN 1

Test specimenconfiguration

(S-TEN 1)Distance from weld (mm)

0

0.1

0.2

0.3

0.4

100 0 0 100 200 300 400 500 600 700 800

Corrosionm

ass(mm)

SS 400 S-TEN 1

Test specimenconfiguration

80080

(SS 400)Distance from weld (mm)

(Dotted line: Average corrosion mass of base metal)

Area ratio 1:1

(Dotted line: Average corrosion mass of base metal)

Area ratio 1:10

Example: Corrosion massof SS 400 in fillet welding Example: Corrosion mass

of SS 400 in fillet welding

Weld

Weld

Weld

Weld

Example: Corrosion massof S-TEN 1 in fillet welding

Example: Corrosion massof S-TEN 1 in fillet welding

S-TEN 1The following property qualification tests were conducted in

the laboratory. In preparing test specimens, it was thought

that corrosion of SS 400 would be accelerated when the

area of SS 400 was less than that of S-TEN 1. Taking this

into account, the test specimens were prepared so that the

ratio of the area of SS 400 to S-TEN 1 became 1:1 and 1:10

for butt-welded joints.

The tests were conducted by immersing the specimens

in 40%-concentrated sulfuric acid at 55for 5 hours. As a

result, as shown in Figs. 4.5 and 4.6, it was found that the

corrosion of specimens was nearly the same as that of

S-TEN itself and that, in such sulfuric-acid corrosive

environment, contact of different metals with an electrical

potential difference of approximately 20 mV can be disre-

garded.

Naturalelectrodepotential

(mV,

Vs,

S.C.E

)

0 1 2 3 4

-390

-380

-370

-360

-350

Immersion time (hrs)

S-TEN 1

SS 400

Galvanic corrosion is caused by the difference in electrical

potential between different metals.

S-TEN 1 and SS 400 show the trend of natural electrode

potential in a 40% sulfuric acid solution at 60, as shown in

Fig. 4.4. In other words, S-TEN 1 shows 20 mV higher

potential than SS 400. Therefore, joining of SS 400 with

S-TEN 1 would make SS 400 a cathode and the corrosion of

S-TEN 1 (anodic dissolution) would be accelerated. It has

been confirmed, however, that such slight difference in

potential is practically insignificant, as introduced below.

Fig. 4.4 Natural Electrode Potentials of S-TEN 1 and SS 400

in 40% Sulfuric Acid (60)

Property Qualification Test Results

Galvanic Corrosion in CorrosiveAtmosphere

Fig. 4.6 Corrosion Mass of S-TEN 1 / Different Material Weld JointFig. 4.5 Corrosion Mass of S-TEN 1 / Different Material Weld Joint

2120

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