161025-ak-thermak 17 pdb final 2 pages · 2018. 1. 23. · thermal mechanical fatigue cycle testing...

THERMAK® 17STAINLESS STEEL

P R O D U C T D A T A B U L L E T I N

T H E R M A K ® 1 7 S TA I N L E S S S T E E L

High Temperature Strength

Superior Oxidation Resistance

Excellent Thermal Fatigue Resistance

Equiaxed Microstructure

Applications PotentialTHERMAK® 17 Stainless Steel has excellent high temperature strength, thermal fatigue and oxidation resistance. It’s improved high strength will facilitate vehicle lightweighting efforts. It is designed for demanding hot-end automotive exhaust applications where intermediate Chrome (Cr) and other high Cr ferritic grades may not be sufficient or where down gauging for light weighting is desired. It also may be appropriate for applications where Type 444 is currently supplied.Product uses in hot-end exhaust system components: manifolds, converters, maniverters and stamped flanges.

Product Description ....................................................................... 1

Physical Properties ........................................................................ 1

Mechanical Properties ................................................................... 2

Elevated Temperature Properties .................................................... 2

Formability ..................................................................................... 4

Corrosion Resistance ..................................................................... 5

Oxidation Resistance ..................................................................... 6

Weldability ..................................................................................... 7

THERMAK® 17 STAINLESS STEEL

TABLE OF CONTENTS

1

THERMAK® 17 Stainless Steel is a ferritic stainless steel that is stabilized with both titanium and niobium (columbium). When given a high temperature final solution anneal, the alloy exhibits dramatic creep resistance. The dual stabilization prevents carbide sensitization exposure and makes the alloy thermally non-hardenable.

COMPOSITION (wt %)

Carbon (C) 0.02 max.

Manganese (Mn) 1.2 max.

Phosphorus (P) 0.05 max.

Sulfur (S) 0.01 max.

Silicon (Si) 1.0 – 1.5

Chromium (Cr) 16.0 – 18.0

Nickel (Ni) 0.5 max.

Nitrogen (N) 0.02 max.

Copper (Cu) 1.0 – 1.5

Titanium (Ti) 0.5 max.

Niobium (Nb) 0.5 max.

AVAILABLE FORMSAK Steel produces THERMAK 17 Stainless Steel coiled, in thicknesses from 0.5 – 2.5 mm (0.02 – 0.10 in.) and widths up to and including 1175 mm (48 in.).

PHYSICAL PROPERTIES

Density, g/cm3 (lbs./in.3) 7.69 (0.278)

Specific Heat, kJ/kg•K (BTU/lbs./°F)0 – 100 °C (32 – 212 °F) 0.454 (0.108)

PRODUCT DESCRIPTION


COEFFICIENT OF THERMAL EXPANSION

14.00

12.00

10.00

8.00

Aver

age

CET

(10-6

/ °C)

0 200 400 600 800 1000

Temperature, °C

2

MECHANICAL PROPERTIES

ELEVATED TEMPERATURE PROPERTIES

TYPICAL ROOM TEMPERATURE MECHANICAL PROPERTIES

0.2%YSMPa (ksi.)

UTSMPa (ksi.)

Elongation % in 50.8 mm (2")

RockwellHardness

469 (68) 586 (85) 30 B86


SHORT TIME ELEVATED TEMPERATURE MECHANICAL PROPERITES

300

250

200

150

100

50

0

0.2%

Offs

et Y

ield

Stre

ngth

, MPa THERMAK 17 SS

18 Cr-CbTM

Type 444

Temperature, °C

Temperature, °C

400

350

300

250

200

150

100

50

0

Ultim

ate

Tens

ile S

treng

th, M

Pa THERMAK 17 SS

18 Cr-Cb

Type 444

600 650 700 750 800 850 900 950

600 650 700 750 800 850 900 950

3

ELEVATED TEMPERATURE PROPERTIES


HIGH TEMPERATURE CREEP RESISTANCE

Sag resistance testing is a simple, common measure of a materials resistance to creep. In testing, the sag resistance of THERMAK 17 Stainless Steel was found to be superior to 18 Cr-Cb and Type 444 in the temperature range of 700 – 930 °C. It was equivalent to 15 Cr-Cb® over the same temperature range.

DEFLECTION AFTER 144 HOUR TEST DURATION

Test Temperature°C

Condition* THERMAK 17 SS (mm)

15 Cr-Cb(mm)

18 Cr-Cb(mm)

Type 444(mm)

700As-annealed 0.15 0.20 0.20 0.38

704 °C/96 hr. 0.05 0.05 0.13 0.15

800As-annealed 0.36 0.36 0.51 0.61

704 °C/96 hr. 0.25 0.30 0.46 0.48

930As-annealed 2.18 2.54 3.61 4.65

704 °C/96 hr. 2.74 2.82 3.12 4.32

*As-annealed tested in duplicate, 704 °C aged single samples.

THERMAL FATIGUE RESISTANCE

Preliminary testing shows THERMAK 17 Stainless Steel to have 20 – 30% improved fatigue resistance over intermediate Chrome (Cr) products currently used in automotive, hot end exhaust applications.

Thermal fatigue life was determined by the cycle number when the tensile stress at 200 °C reaches to 70% of the tensile stress at the first thermal fatigue cycle at 200 °C.

THERMAL MECHANICAL FATIGUE CYCLE TESTING1.2

1.0

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1.0

-1.2

875

815

755

695

635

575

515

455

395

335

275

215

155

Rela

tive

Stra

in

Tem

pera

ture

, °C

0 120 240 360 480 600 720 840 960 1080Time, sec.

x

v

-x

-vStress Free

ThermalExpansion

Strain Cycle

Thermal Cycles of200 – 830 °C

FirstThermalFatigue Cycle

Controlled Strainwith Restraint

Ration of(x-y)/x=0.4

THERMAL FATIGUE LIFE

THERMAK 17 SS 15 Cr-Cb

1800

1600

1400

1200

1000

800

600

400

200

0

Ther

mal

Fat

igue

Life

, Cyc

les 30%

Better Life

Reduce gauge, save weight while maintaining the same durability

4

FORMABILITY

THERMAK 17 Stainless Steel is readily drawn and formed. The ULTRA FORM® technology enhances formability and improves the consistency from one coil to another.

Mas

s En

gine

erin

g St

rain

(%)


Property

Orientation to Sheet R.D.

L D T

Tensile/Hardness Test (ASTM E8, E694, E18, A370)

0.2%YS (MPa) 440 465 457

UTS (MPa) 563 584 545

% El. in 50.8 mm (man’l) 31 29 30

n-Value (10%-Ult.) 0.152 0.139 0.143

Strength Coeff. (MPa) 876 889 883

HRB (HRA) 90 (55.5)

ASTM Grain Size 5.0

Stretch r (plastic strain ratio) at 18% (ASTM E517)

r-Value 1.01 0.92 1.49

rm 1.09

delta r 0.34

delta r (Max – Min) 0.62

Ridging No. 1.00

Olsen Cup Height (mm) 11.40

LDR 2.10

FORMING LIMIT CURVE

THERMAK 17 STAINLESS STEEL COIL, 2 mm THICKDetermined Using CamSys Localized Nodal Strain Measurement Method

2.54 mm Square Grid Pattern.

-40 -30 -20 -10 0 10 20 30 40

Minor Engineering Strain (%)

80

70

60

50

40

30

20

10

0

50

40

302010-10-20

0

0

Longitudinal to Sheet R.D.

Transverse to Sheet R.D.

Thinning

5

CORROSION RESISTANCE

THERMAK 17 Stainless Steel shows improved oxidation resistance and oxide adherence when compared to other 17% chromium ferritics. The high silicon and manganese, copper added alloy reduces spalling when exposed to cyclic high temperature salt conditions creating a barrier of oxide that provides protection to the steel substrate. The dual stabilized alloy resists intergranular corrosion when welded and provides comparable corrosion resistance to equivalent alloys in acidic, high sulfate and lower temperature, cyclic salt environments commonly found in automotive exhaust applications.

SALT CYCLESolution Concentration: 5% Sodium Chloride

Heat Treatment: 343 °C (650 °F)

CORROSION RESISTANCE

MUFFLER CONDENSATEHeat Treatment: 500 °C (932 °F)

Test Solution: • 5000 ppm SO4

2-

• 100 ppm Cl• 100 ppm NO3

• 100 ppm Formic Acid


MUFFLER CONDENSATE TEST

SALT CYCLE TEST

Solution pH is adjusted to 3.3 – 3.5 using sulfuric acid by adding approximately 300 – 400 ppm SO4

2- to the test solution

0 10 20 30 40 50

Days

THERMAK 17 SS 15 Cr-Cb Type 439

600

400

200

0

150

100

50

0

Pit D

epth

s (u

m)

Mas

s Lo

ss (m

g/cm

2 /yr.)

THERMAK 17 SS

15 Cr-Cb

Heat treat 1 hr. at 343 °C (650 °F)(Day 1)

Heat treat 1 hr. at 500 °C (932 °F)

Cycl

e Re

peat

s ev

ery

7 da

ysCy

cle

Repe

ats

ever

y 5

days

Ambient Dry1 hour 45 minutes

(Day 1 – Day 5)

16 hrs. exposed to boiling testsolution (boil solution to dryness)

15 minute5% sodium chloride immersion

(Day 1 – Day 5)

Humidity exposure for 6 hrs. at60 °C (140 °F)/85% RH

Place in humidity chamber60 °C (140 °F)/85% RH

Balance of the 24 hour periodand Day 6 & Day 7

Balance of week:Continuous exposure to humidity at

60 °C (140 °F)/85% RH

Samples are removed at 2, 4 and 6 week intervals

6

SPALLING RESISTANCE – HOT SALTHeat Treatment: 677 °C (1250 °F)

THERMAK 17 SS 15 Cr-Cb

6

4

2

0

Mas

s Lo

ss (m

g/cm

2 )


HOT SALT TEST

CORROSION RESISTANCE (cont.)

OXIDATION RESISTANCE

Heat treat 90 min. at 677 °C (1250 °F)

Five minute soak in 5% sodium chloride

One minute cold water quench

Measurements collectedafter ten cycles

16 hours in humidity chamber60 °C/(140 °F)/85% RH

TOTAL MASS LOSS – HOT SALTHeat Treatment: 677 °C (1250 °F)

THERMAK 17 SS 15 Cr-Cb Type 439

26

24

22

20

Mas

s Lo

ss (m

g/cm

2 )

Cycl

e Re

peat

s 4

times

in 8

hou

rs

THERMAK 17 Stainless Steel provides an improved oxidation resistance compared to other ferritic alloys such as Type 439. In addition to 17% Cr content, high Si and high Mn contents improve high temperature oxidation resistance in air and exhaust gas atmospheres.

In continutous service, 200 hours at 930 °C, THERMAK 17 Stainless Steel exhibited a uniform scale pattern and no spalling.

Before Cleaning

After CleaningLess mass loss due to spalling

8

THERMAK 17 is generally considered to be weldable by the common fusion and resistance welding processes. Grain growth in the weld heat affected zone, with reduced weld toughness, is a common occurrence in ferritic stainless steel weldments. Low weld heat input and elimination of weld discontinuities will provide maximum toughness in welded sections. Warming of welded parts prior to forming may also improve weld toughness. When a weld filler is required, 18 Cr-Cb is recommended for applications where high temperature thermal cycling is expected. Filler wires 308L or 309L will provide improved weld ductility for lower temperature applications. Additional information concerning the welding of ferritic stainless steels may be obtained from the following publications:

1. ANSI/AWS A5.9, A5.22 and A5.4 (stainless welding electrode specifications).

2. “Welding of Stainless Steels and Other Joining Methods,” SSINA, (www.ssina.com).

WELDABILITY


7

AK Steel Corporation9227 Centre Pointe DriveWest Chester, OH 45069844.STEEL99 | [email protected]

AK Steel is a leading producer of flat-rolled carbon, stainless and electrical steel products, and carbon and stainless tubular products, primarily for automotive, infrastructure and manufacturing, construction and electrical power generation and distribution markets. Headquartered in West Chester, Ohio (Greater Cincinnati), the company employs approximately 8,500 men and women at eight steel plants, two coke plants and two tube manufacturing plants across six states (Indiana, Kentucky, Michigan, Ohio, Pennsylvania and West Virginia) and one tube plant in Mexico. Additional information about AK Steel is available at www.aksteel.com.

The information and data in this document are accurate to the best of our knowledge and belief, but are intended for general information only. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees nor to be construed as express or implied warranties of suitability for these or other applications.

Data referring to material properties are the result of tests performed on specimens obtained from specific locations of the products in accordance with prescribed sampling procedures; any warranty thereof is limited to the values obtained at such locations and by such procedures. There is no warranty with respect to values of the materials at other locations.

AK and the AK Steel logo are registered trademarks of the AK Steel Corporation.

05.04.17

161025-ak-thermak 17 pdb final 2 pages · 2018. 1. 23. · thermal mechanical fatigue cycle testing...

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