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The best solution to maximize efficiency for the newest gas turbines.

Power Gen market is requiring more efficient and sustainable solutions. The modern power plants are increasing the use of new generation gas turbines, aiming at reducing CO2 emissions while improving the performance standard.To support Original Equipment Manufacturers in achieving higher plant efficiency, more sophisticated materials are needed to withstand higher steam temperature.Tenaris invested more than 10 MLN $ to

develop a new alloy for tubes with improved resistance to steam oxidation allowing Power Plant designers to exploit the full potentiality of newest Gas and Steam Turbines in Combined Cycle power plant.Thor®115 (Tenaris High Oxidation Resistance Steel) is characterized by:- increased steam oxidation resistance

(working above 600°C),- long term stability based on modified

microstructure,- superior creep behavior than grade 91.

HIGHER EFFICIENCYLONGER LIFE MATERIAL REDUCED CO2 EMISSIONS

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Tena

risTh

or®11

5

Thor®115 is a new creep strength-enhanced ferritic steel for service in supercritical and ultra-supercritical boiler applications. This steel is an evolution of the popular ASTM grade 91, with increased Cr content in order to

Long duration steam oxidation testing was performed at the Oak Ridge National Laboratory. Testing involved Thor®115 (materials ScA and ScB) and grade SA-213 T91. Measurement confirms that Thor

oxidation is similar from 600 to 650 °C, while T91 oxidation accelerates. This is believed to be an effect of the faster Cr diffusion at higher temperature, which, combined with greater Cr availability in Thor than T91, allows the formation of aCr-richer, more protecting oxide scale.

C Mn Si Cr Ni Cu Mo Al V Nb N

0.1 0.4 0.4 11.0 < 0.2 < 0.15 0.5 < 0.02 0.2 0.04 0.05

250

200

150

100

50

0600 °C 625 °C

-T91 THOR

650 °C

Inn

er o

x. t

hk.

(μm

)

T91

Thor

Chemical composition

Steam oxidation

allow better steam oxidation resistance at high temperature and suitable alloying balance to ensure a fully martensitic microstructure, and stability of the strengthening precipitates after long term ageing.

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35

30

25

20

15

10

5

0

0 100 200 300 400 500 600 700

T91 Thor 115

k (W

/mk)

Temperature (°C)

Thermal conductivity

9Cr-1Mo

18Cr-10Ni

12Cr

25

20

15

10

5

0

0 100 200 300 400 500 600 700

Thor 115

A (x

10-6 °

C-1)

Temperature (°C)

Thermal expansion

9Cr-1Mo

12Cr

18Cr-10Ni

PhysicalpropertiesAs a ferritic steel, Thor®115 presents smaller thermal expansion and better thermal conductivity with respect to austenitic grades.

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Tena

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or®

115

Thor® 115 enforces the same tensile strength and hardness requirements as ASME grade 91:

Thanks to the formation of stable precipitates, creep strength is guaranteed in the long term, as is demonstrated by over 1 million hours of creep testing from trial heats – plates, tubes and pipes – covering and exceeding the whole time-temperature range required for rupture strength assessment.

The allowable stresses have been independently evaluated from tensile and creep testing data, resulting in similar or superior performance with respect to ASME grade 91.

Mechanical propertiesand allowable stress

Yield strength Tensile strength Elongation Hardness

≥ 450 MPa 620-830 MPa ≥ 19% longitudinal 190-250 HBW

≥ 65 ksi 90-120 ksi 90-120 ksi 200-265 HV

100

700 675 650 650 625 600 575 550

1000 10000 100000

Load

Duration (h)

Creep-rupture

25

50

100

200

575 °C100 kh

625 °C100 kh

650 °C100 kh

550 °C100 kh

600 °C100 kh

400

22 23 24 25 26 27 28

Stre

ss (M

Pa)

Larson-Miller plot

PLM = T (C + log t) / 1000

-40

-40

60

170

160

380

260 360

590

460

800

560

1010

660

1220

0 0

5010

5

100 15

15020

200 200

25

Stre

ss (M

Pa) Stress (K

si)

Temperature (°C)

Temperature (°F)

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GTA Weld (ER90S-B9)

SMA Weld (E9015-B91)

GTA Root Pass – ID View (ER90S-B9)

Close-up of SMAW Cap (E9015-B91)

Weldability

Welding trials were performed with several third parties. Plate, tube and pipe butt welds were fabricated according to different procedures, using the gas-tungsten arc (GTA), shielded metal arc (SMA), and submerged arc processes (SA).For welding purposes, Thor®115 behaviour is nearly identical to that of ASME grade 91, because the strength of the base material is comparable, as well as the heat treatment temperatures, as the alloying is based on similar strengthening principles.No custom filler metal is therefore required for Thor; instead, the filler materials that are conventionally employed for grade 91 steel were chosen for trials, because the strength of the base material is comparable, as well as the heat treatment temperatures, as the alloying is based on similar strengthening principles.By this rationale, the qualification of a

new filler material is avoided and welding procedures that are consolidated for grade 91 components may be applied to Thor as well; for the purpose of establishing a welding procedure, Thor was then considered to be a material with P-Number 15E (i.e., in the same group as grade 91).Thor-Thor welding trials were then made using modified 9Cr-1Mo steel filler metal; Ni-based filler metal may be used for those applications were localized corrosion/oxidation are an issue. For Thor to austenitic steel welds, Ni-based consumable was chosen; for Thor to grade 22 (2¼Cr-1Mo) welds, 2¼Cr filler was chosen in order to prevent de-carburation of the lower grade HAZ.

Completed pipe welds using a procedure with combined welding processess: manual GTAW (top) and manual SMAW (bottom).

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Tena

risTh

or®

115

Dimensional range

Outer diameter Wall thickness Length

31.8 to 114.3 mm 2.9 to 20.0 mm Up to 26 meters

Outer diameter Wall thickness

73 to 711 mm 8.0 to 40.0 mm

Tubing

Pipes

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For additional information, please visit www.tenaris.com

For technical assistance, please contact Simone Baietta - sbaietta@tenaris.com Antonella Ferrara aferrara@tenaris.com

Tenaris has produced this brochure for general information only. While every effort has been made to ensure the accuracy of the information contained within this publication, Tenaris does not assume any responsibility or liability for any loss,

damage, injury resulting from the use of information and data herein. Tenaris products and services are only subject to the Company’s standard terms and Conditions or otherwise to the terms resulting from the respective contracts of sale,

services or license, as the case may be. The information in this publication is subject to change or modification without notice. For more complete information please contact a Tenaris’s representative or visit our website at www.tenaris.com.

©Tenaris 2019. All rights reserved.

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