Proceedings of the ASME 2014 Pressure Vessels & Piping Conference

PVP2014
July 20-24, 2014, Anaheim, California, USA

PVP2014-28538

DEVELOPMENT OF A MATERIAL DATABOOK FOR API STD 530

Dr. M. Prager D. A. Osage

Welding Research Council The Equity Engineering Group, Inc.
New York, NY USA Shaker Heights, Ohio USA

Dr. C. H. Panzarella R. G. Brown

The Equity Engineering Group, Inc. The Equity Engineering Group, Inc.
Shaker Heights, Ohio USA Shaker Heights, Ohio USA

ABSTRACT Properties Council (MPC), a division of the Welding

Research Council Inc. (WRC) is now contained in materials
In 2005, the American Petroleum Institute (API) initiated
data book published as WRC Bulletin 541 Evaluation of
an effort to update existing yield, tensile and stress-rupture
Material Strength Data for Use in API Std 530 [1].
properties found in API Standard 530 Calculation of Heater
Tube Thickness in Petroleum Refineries and add properties To create WRC 541, new mechanical property data was
for alloys not yet covered. The design curves in API 530 gathered that reflects modern steel making practices for
until that time were based on data gathered 40 to 50 years alloys currently produced and used for petroleum refinery
earlier by the Materials Properties Council (MPC) and its heater applications, and to analyze this new data using
predecessor, the ASTM-ASME Joint Committee on the modern parametric data analysis methods to derive equations
Effects of Temperature on Materials. Later, MPC developed suitable for incorporation into API Std 530. The materials
proprietary statistically sound algorithms to apply lot- included in WRC 541 are shown in Table 1.
centered regression for parametric analysis of large,
The materials data presented in WRC 541 were obtained
unbalanced data sets of diverse heats tested under a variety of
from materials produced more recently than those used in
conditions. Subsequently, MPC built and maintained
preparing prior editions of API Std 530. The data for this
archives on the creep and stress-rupture data of alloys of
project were gathered by the MPC under API contract and
interest to API. For some alloys the data sets contained over
include test results for materials produced and tested at
a thousand test results on over 100 heats. To assure that
facilities outside of the United States. The data collections
future designs will reflect the properties of materials
for prior editions of API Std 530 were limited to US sources.
produced using modern practices, API requested MPC to
The new data for each alloy were evaluated using modern
deliver design properties applicable to current materials. This
parametric analysis methods and the results compared
paper presents the back ground, principles and results of the
graphically to the previously published properties. The
recent analyses performed by MPC that are now available for
coefficients for the polynomials resulting from the regression
use by the API membership. The properties furnished in
analysis of the newer materials are presented in tabular form
equation format are yield and ultimate tensile strengths for
in this document to facilitate computer implementation for
time-independent stresses and results of lot centered Larson-
design and life assessment.
Miller Parameter analyses to obtain time-dependent average
and minimum strengths. The properties and application The material data required for a design calculation in
examples of the equations are published as WRC Bulletin accordance with API Std 530 are the yield strength, ultimate
541 Evaluation of Material Strength Data for Use in API Std tensile strength, stress-rupture exponent, and minimum and
530. average stress rupture properties as described using Larson-
Miller Parameter equations. This information is used to
INTRODUCTION obtain the time-independent or elastic allowable stress and
API Std 530 Calculation of Heater Tube Thickness in the time-dependent or rupture allowable stresses used in
Petroleum Refineries is an API Standard used for the design determining the required wall thickness of a fired heater tube
of fired heater tubes in the refining and petrochemical or bend for a specified service life and temperature.
industry. In 2005, the American Petroleum Institute (API) Equations and coefficients for yield strength, ultimate tensile
undertook an effort to update existing yield, tensile and stress strength, stress-rupture exponent, and minimum and average
rupture design curves in API Std 530 and develop new curves stress rupture properties using the Larson-Miller Parameter
for certain alloys that were not yet covered. The background, are provided in WRC 541 in both US Customary and SI
principles and results of this work performed by the Materials units.

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 A series of examples is included in WRC 541 to TIME-DEPENDENT ALLOWABLE STRESS
illustrate application of the analytical equations used to
represent the properties. Comparisons are included of the Larson-Miller Parameter
new properties determined under this project with those in the The Larson Miller Parameter (LMP) provides a
prior editions of API Std 530. relationship between stress, time to failure (taken here to
YIELD STRENGTH mean test, service or design life, Ld ) and temperature. The
In WRC 541, Equation (1) is used to represent the yield basic expression for the Larson-Miller Parameter is given by
strength as a function of temperature. The coefficients for Equations (4) and (5). The term LMP (σ ) is evaluated
use in this equation for a subset of materials 530 are provided using Equation (10).
in Table 2 in SI units.
(T + 460 ) ( C + log10 [ Ld ])
LMP (σ ) = ( hours, ksi, F)

( )
o
(4)
C0 + C1T + C2T 2 + C3T 3 + C4T 4 + C5T 5 
σ= σ ⋅ 10 rt  
(1)
ys ys (T + 273) ( C + log10 [ Ld ])
LMP (σ ) = ( hours, MPa, o
C) (5)

The yield strength at temperatures above room Equations (6) thru (9) are alternate forms of the same
temperature may be calculated using this equation by equation. In Equations (6) and (7), the service or design life
multiplying the yield strength value at room temperature by a is shown as a function of applied stress and temperature. In
temperature dependent ratio term. If σ ys rt
chosen for this Equations (8) and (9), the temperature is a function of the
applied stress and service life.
equation is the specified minimum room temperature value of
 LMP (σ ) 
yield strength, then the resulting value at a higher temperature  −C 
can be taken as an estimate of the minimum value at that Ld = 10 
(T + 460 ) 
( hours, ksi, o F ) (6)
temperature. If the average room temperature value of yield
 LMP (σ ) 
strength for a data set is used in Equation (1), then the  −C 

resulting value at the higher temperature can be taken as the Ld = 10 

(T + 273) 
( hours, MPa, oC ) (7)
best estimate of the average value at that temperature. The
LMP (σ )
ratios are deemed to be applicable over the range = of T − 460 ( hours, ksi, o F ) (8)
commonly provided and heat treatments and compositions for ( C + log10 [ Ld ])
the respective materials.
LMP (σ )
= T − 273 hours, MPa, oC ( ) (9)
TENSILE STRENGTH ( C + log [ ])
L 10 d
Equation (2) is in the same form as Equation (1) and is
used to represent the ultimate tensile strength as a function of The coefficient C in Equations (4) thru (9) is the
temperature in WRC 541. The coefficients for use in this Larson-Miller Constant.
equation for a subset of materials are provided in Table 2 in In WRC 541, the Larson-Miller Parameter for each
SI units. material is presented as a polynomial in log base 10 of stress

( )
C0 + C1T + C2T 2 + C3T 3 + C4T 4 + C5T 5  in the form given by Equation (10). The coefficients of
σ=
uts σ uts
rt
⋅ 10  
(2) Equation (10) for a subset of materials are provided in Table
4. The Larson-Miller Constant, C , applicable to the average
The ultimate tensile strength at temperatures above room and minimum properties for each material is also shown in
temperature may be calculated using this equation by Table 4. As an example, a plot of the Equation (10) shows
multiplying the ultimate tensile strength value at room the Larsson-Miller Parameter and the optimized constants is
temperature by a temperature dependent ratio term presented shown in Figure 1 for 2.25Cr-1Mo. The minimum constant
in the parenthesis. If the specified minimum room entries in Table 4 are appropriate to represent the variance
temperature value of ultimate tensile strength is used in expected at a 95% confidence interval.
Equation (2), then the resulting value at temperature is an
LMP (σ ) = A0 + A1 ⋅ log10 [σ ] + A2 ⋅ ( log10 [σ ]) + A3 ⋅ ( log10 [σ ]) (10)
2 3
estimate of the minimum value at a higher temperature. If the
average room temperature value of ultimate tensile strength
of a data set is used in Equation (2), then at a higher The equations for the Larson-Miller Parameter should
temperature one obtains an estimate of the corresponding not be used for temperatures outside the limiting metal
average value. temperature ranges shown for each material in Table 3.
Note that this treatment of the Larson-Miller Parameter
TIME-INDEPENDENT ALLOWABLE STRESS is different from that in API Std 530 6th Edition. In that
document, non-optimized Larson-Miller Constants are used
In API Std 530, the time-independent or elastic allowable
stress for each alloy is proportional to the yield strength over for broad material groups, C = 15 for ferrous materials and
a specific range of temperatures, see Equation (3). The C = 20 for high alloy and nonferrous (high-nickel)
proportionality constant is dependent on the material as materials. Here, alloy specific, optimized Larson-Miller
shown in Table 3. Parameter constants are provided so that the equations
represent minimum and average behavior more precisely.
=
S e Fed ⋅ σ ys (3) Also, extrapolation of behavior with temperature is sensitive
to the constant used and the optimized constant should be
used.
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 TABLE 1 – MATERIAL DESIGNATION AND APPLICABLE TABLE 2 – MINIMUM YIELD AND TENSILE STRENGTH IN
ASTM SPECIFICATIONS MPA AS A FUNCTION OF TEMPERATURE IN °C

Material Applicable ASTM Specifications Yield Strength Tensile Strength

Material Parameter
(MPa) (MPa)
Low Carbon Steel A161, A192
σ rt 241 414
Medium Carbon A53 Grade B (seamless), A106 Grade
Steel B, A210 Grade A-1 C0 7.6855674E-03 4.5962691E-02

C-0.5Mo A161 T1, A209 T1 A335 P1 C1 -3.6171986E-04 -2.8409842E-03

Medium
1.25Cr-0.5Mo A213 T11, A335 P11, A200 T11 Carbon Steel
C2 -9.8196907E-08 3.4226184E-05

2.25Cr-1Mo A213 T22, A335 P22, A200 T22

C3 -5.8400015E-10 -1.3643478E-07

C4 0 2.2146357E-10
3Cr-1Mo A213 T21, A335 P21, A200 T21
C5 0 -1.3334542E-13
5Cr-0.5Mo A213 T5, A335 P5, A200 T5

5Cr-0.5Mo-Si A213 T5b, A335 P5b σ rt 207 414

C0 1.1378966E-02 8.1095353E-03
7Cr-0.5Mo A213 T7, A335 P7, A200 T7
C1 -5.5740661E-04 -3.8072714E-04
9Cr-1Mo A213 T9, A335 P9, A200 T9
1.25Cr-
0.5Mo
C2 8.3372179E-07 -3.6384086E-07
9Cr-1Mo-V A213 T91, A335 P91, A200 T91
C3 1.9369687E-09 1.0055235E-08
A213 Type 304L, A271 Type 304L,
Type 304L SS
A312 Type 304L, A 376 Type 304L C4 -6.5542374E-12 -2.2457714E-11

A213 Type 304, A271 Type 304, C5 2.8394538E-15 1.1198185E-14

A312 Type 304, A 376 Type 304,
Type 304/304H SS
A213 Type 304H, A271 Type 304H, σ rt 207 414
A312 Type 304H, A 376 Type 304H C0 1.1378966E-02 8.1095353E-03
A213 Type 316L, A271 Type 316L, C1 -5.5740661E-04 -3.8072714E-04
Type 316L SS
A312 Type 316L, A 376 Type 316L
2.25Cr-1Mo C2 8.3372179E-07 -3.6384086E-07
A213 Type 316, A271 Type 316,
A312 Type 316, A 376 Type 316, C3 1.9369687E-09 1.0055235E-08
Type 316/316H SS
A213 Type 316H, A271 Type 316H, C4 -6.5542374E-12 -2.2457714E-11
A312 Type 316H, A 376 Type 316H
C5 2.8394538E-15 1.1198185E-14
Type 317L SS A213 Type 317L, A312 Type 317L

A213 Type 321, A271 Type 321,

Type 321 SS
A312 Type 321, A 376 Type 321

A213 Type 321H, A271 Type 321H,

Type 321H SS
A312 Type 321H, A 376 Type 321H

A213 Type 347, A271 Type 347,

Type 347 SS
A312 Type 347, A 376 Type 347

A213 Type 347H, A271 Type 347H,

Type 347H SS
A312 Type 347H, A 376 Type 347H

Alloy 800 B407 UNS N08800

Alloy 800H B407 UNS N08810

Alloy 800HT B407 UNS N08811

HK-40 A608 Grade HK-40

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 trends even when data for individual lots are limited. Determination of the Time-Dependent Allowable
The relative rankings and projections for the individual Stress
lots studied are valuable despite the fact that the average
behavior of the entire data set may not be of any As presented in WRC 541, the time-dependent allowable
significance. stress, σ , is determined from the Larson-Miller Parameter
given by Equation (10). The solution is given by Equation
Situation 1) above is encountered when manufacturers (11).
offer data purported to represent a population of commercial
products. Typically, from 5 to 15 test results are provided for S=
t σ= 10 X (11)
each heat or lot. To make matters worse the tests may be
scattered over one to six test temperatures in a 1000°F range. The exponent X in Equation (11) is computed exactly
Simply put, the behavior of individual lots relative to one as follows based on the values of the coefficients in Equation
another or the “average behavior” will fall into one of three (10) as shown below for the cases where first, second and
categories, see Figure 3; third order polynomials were obtained for the stress
dependence of the LMP.
• Parallel,
• Convergent, and Case 1 – First order polynomial. A1 is not equal to zero
• Cross-over. and A2 and A3 are equal to zero. Rewriting Equation (10) for
Parallelism may be observed over a range of this case:
temperatures when the strengthening mechanism is stable. LMP = A0 + A1 ⋅ log10 [σ ] (12)
For example, heats of gamma prime strengthened alloys or
heats of annealed, solid solution strengthened alloys might A1 ⋅ X + ( A0=
− LMP ) 0 with X log10 [σ ]
= (13)
display parallel stress-rupture behavior. Models
The solution is given by:
incorporating single heat constants work well in this case.
LMP − A0
Convergent behavior appears when the strengthening X = (14)
mechanism diminishes with increasing time and temperature A1
and all lots approach a substantially common metallurgical
condition. Such a database may involve materials which are Case 2 – Second order (quadratic) polynomial. A2 is not
initially quenched and tempered to varying degrees. Smith equal to zero, A3 is equal to zero, and A1 can be any value
(3) demonstrated convergent behavior for 2¼Cr-1Mo steel at including zero. Rewriting Equation (10) for this case:
temperatures above 1000°F. Two heat constants are needed
LMP = A0 + A1 ⋅ log10 [σ ] + A2 ⋅ ( log10 [σ ])
2
to describe such behavior. (15)
Cross-over is expected where the strengthening
mechanism at the low temperature end of the creep range is A2 ⋅ X 2 + A1 ⋅ X + ( A0 =
− LMP ) 0 =
with X log10 [σ ] (16)
ineffective or detrimental at high temperatures. Fine grain
As long as A12 − 4 A2 ( A0 − LMP ) > 0 , there are two real
size or deformation enhances low temperature strength of
austenitic stainless steels or nickel-base alloys. However, roots to this equation:
high in the range of operating temperatures for these alloys
coarse grain, non-coldworked structures are optimal. Hence, − A1 + A12 − 4 A2 ( A0 − LMP )
X1 = (17)
those which are weaker at low temperatures become stronger 2 A2
at high temperatures and vice versa. Heats cross the
"average" behavior which may represent the behavior of no − A1 − A12 − 4 A2 ( A0 − LMP )
actual heat or lot at all. Again, two heat constants are needed X2 = (18)
to describe this behavior. 2 A2

An example of situation 2) above is as follows. When The final solution is whichever root X 1 or X 2 satisfies
one is provided with test results for heats which vary over the condition ∂ ( LMP ) ∂σ < 0 , which is equivalent to
modest ranges of compositions, but which were produced by
different companies, the challenge is to select the strongest. ∂ ( LMP ) ∂X < 0 . Taking this derivative yields the
Because of their differing origins the heats would not have expression,
been tested systematically with regard to stress, temperature
and duration. Traditional, simple, isothermal comparisons ∂ ( LMP )
= A1 + 2 A2 X (19)
would then be impossible and even misleading due to bias, ∂X
scatter and changing slopes. This is an ideal situation for
Lot-Centered Parametric Analysis. After parametric analysis, Equation (19) should be evaluated for both X 1 and X 2 ,
heats can be ranked according to lot constants or computed and the final solution X is whichever value satisfies the
strengths for the time and temperature of greatest interest. above condition. Specifically,

 X if A1 + 2 A2 X 1 < 0
X = 1 (20)
 X 2 if A1 + 2 A2 X 2 < 0

Case 3 – Third order (cubic) polynomial. A3 is not equal

to zero, and A1 and A2 can be any values including zero.
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 Figure 5 – The Average and Minimum Stress Rupture
Strengths as Functions of the Larson-Miller Parameter –
Figure 3 – The Behavior of Individual Lots Relative to One Comparison of Existing API Std 530 Data and Proposed New
Another on a Stress Verse Larson-Miller Parameter Plot Data in US Customary Units Based on the Average Larson-
Miller Constant: 2.25Cr-1Mo

Figure 4 – Yield and Ultimate Tensile Strength as a Function

of Temperature – Comparison of Existing API Std 530 Data
and Proposed New Data in US Customary Units: 2.25Cr-1Mo

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 DATA COMPARISON and ultimate tensile strengths are the stress-rupture exponent,
and the minimum and average stress-rupture properties which
For all of the materials shown in Table 1, a comparison
were obtained using optimized, statistically based, Lot-
of the new data for yield strength, tensile strength, and creep
Centered Larson-Miller Parameter equations. The equations
rupture to the data in prior versions of API Std 530 is
are provided with the necessary significant figures and are
provided.
suitable for ready implementation in computer programs for
A plot of the yield strength and tensile strength verse design and life assessment applications.
temperature for the new properties determined under this
project with those in the prior editions of API Std 530 is BIBLIOGRAPHY
shown in Figure 4 for 2.25Cr-1Mo. For this material, the 1. Prager, M., Osage, D.A. and Panzarella, C.H.,
change in the yield strength and tensile strength trend with
Evaluation Of Material Strength Data for Use in API Std
temperature from prior editions is seen to be small. This was
530, WRC 541, The Welding Research Council, New
the case for most of the materials evaluated in the project.
York, N.Y.
Most of the prior curves in API Std 530 were adapted 2. Prager, M., “Understanding Materials Behavior Through
from Smith's work and the data collections he assembled for the Application of Modern Parametric Analysis
MPC in the 1960's and 1970's. A noteworthy comparison of Techniques,” International Conference on Creep; Tokyo;
former and recent curves is the plot for 2.25Cr-1Mo stress- Japan; 14-18 Apr. 1986. pp. 39-46. 1986.
rupture data shown in Figure 5. New data for this material
3. Manson, S.S. and Muralidharen, U., “Analysis of Creep
were obtained primarily from Japan. However, the linear
Rupture Data for Five Multiheat Alloys by the Minimum
extension of the parameter curve at low stresses is justified by
commitment method using Double Heat Term Centering
data from MPC's Project Omega studies, in which the
Technique,” MPC-23, Progress in Analysis of fatigue
specimens tested were protected from the severe oxidation
and Stress Rupture, MPC, 1984.
which occurred during tests which were available to Smith.
The test results in the low stress range that were provided to 4. Sjodahl, L.H., “Extensions of the Multiple Heat
Smith were performed at temperatures at which oxidation Regression Technique Using Centered Data for
was very rapid and the tests seldom lasted more than 2,000 Individual Heats,” MPC-23, Progress in Analysis of
hours, irrespective of the applied stress. Hence, the Fatigue and Stress Rupture, MPC, 1984.
parameter curves plunged steeply with decreasing stress. The
trends now presented for API Std 530 in WRC 541 are
justified by recent, longer term exposures and are also
characterized by the Omega property equations and
coefficients found in Annex F of API 579-1/ASME FFS-1,
the joint Fitness for service document.
For many alloys, the new properties do not vary
remarkably from those shown in the curves found in the
various previous editions of API Std 530. However, the user
of WRC 541 gets is given a better appreciation of the amount
of data and the scatter as well as a clear picture of the trends
and limitations of the data.
Perhaps the most noteworthy change as compared to the
former API documents used in heater tube design is the
introduction of optimized Larson-Miller Parameter Constants
for average and minimum properties instead of a value of 20
for all low alloy steels and a value of 15 for all austenitic
alloys (stainless steels and nickel base alloys). This is a
change which has significant practical implications. The
larger the value of the Larson-Miller Constant the greater is
the calculated effect of temperature on life. Thus, in some
cases, significant differences may be found in regard to
design and remaining life calculations.

CONCLUSION
The material data presented in the WRC 541 publication
up-date those in the various editions of API Std 530 and were
specifically gathered by the Materials Properties Council
(MPC) of WRC under contract to API and prepared in
formats for ready use with API Std 530/ISO 13704t in the
design and life assessment of fired heaters. The WRC 541
publication includes a comprehensive tutorial with many
examples of the proper implementation of the equations
which are presented in both US Customary and SI units. The
properties included in equation format in addition to the yield
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 TABLE 1 – MATERIAL DESIGNATION AND APPLICABLE TABLE 2 – MINIMUM YIELD AND TENSILE STRENGTH IN
ASTM SPECIFICATIONS MPA AS A FUNCTION OF TEMPERATURE IN °C

Material Applicable ASTM Specifications Yield Strength Tensile Strength

Material Parameter
(MPa) (MPa)
Low Carbon Steel A161, A192
σ rt 241 414
Medium Carbon A53 Grade B (seamless), A106 Grade
Steel B, A210 Grade A-1 C0 7.6855674E-03 4.5962691E-02

C-0.5Mo A161 T1, A209 T1 A335 P1 C1 -3.6171986E-04 -2.8409842E-03

Medium
1.25Cr-0.5Mo A213 T11, A335 P11, A200 T11 Carbon Steel
C2 -9.8196907E-08 3.4226184E-05

2.25Cr-1Mo A213 T22, A335 P22, A200 T22

C3 -5.8400015E-10 -1.3643478E-07

C4 0 2.2146357E-10
3Cr-1Mo A213 T21, A335 P21, A200 T21
C5 0 -1.3334542E-13
5Cr-0.5Mo A213 T5, A335 P5, A200 T5

5Cr-0.5Mo-Si A213 T5b, A335 P5b σ rt 207 414

C0 1.1378966E-02 8.1095353E-03
7Cr-0.5Mo A213 T7, A335 P7, A200 T7
C1 -5.5740661E-04 -3.8072714E-04
9Cr-1Mo A213 T9, A335 P9, A200 T9
1.25Cr-
0.5Mo
C2 8.3372179E-07 -3.6384086E-07
9Cr-1Mo-V A213 T91, A335 P91, A200 T91
C3 1.9369687E-09 1.0055235E-08
A213 Type 304L, A271 Type 304L,
Type 304L SS
A312 Type 304L, A 376 Type 304L C4 -6.5542374E-12 -2.2457714E-11

A213 Type 304, A271 Type 304, C5 2.8394538E-15 1.1198185E-14

A312 Type 304, A 376 Type 304,
Type 304/304H SS
A213 Type 304H, A271 Type 304H, σ rt 207 414
A312 Type 304H, A 376 Type 304H C0 1.1378966E-02 8.1095353E-03
A213 Type 316L, A271 Type 316L, C1 -5.5740661E-04 -3.8072714E-04
Type 316L SS
A312 Type 316L, A 376 Type 316L
2.25Cr-1Mo C2 8.3372179E-07 -3.6384086E-07
A213 Type 316, A271 Type 316,
A312 Type 316, A 376 Type 316, C3 1.9369687E-09 1.0055235E-08
Type 316/316H SS
A213 Type 316H, A271 Type 316H, C4 -6.5542374E-12 -2.2457714E-11
A312 Type 316H, A 376 Type 316H
C5 2.8394538E-15 1.1198185E-14
Type 317L SS A213 Type 317L, A312 Type 317L

A213 Type 321, A271 Type 321,

Type 321 SS
A312 Type 321, A 376 Type 321

A213 Type 321H, A271 Type 321H,

Type 321H SS
A312 Type 321H, A 376 Type 321H

A213 Type 347, A271 Type 347,

Type 347 SS
A312 Type 347, A 376 Type 347

A213 Type 347H, A271 Type 347H,

Type 347H SS
A312 Type 347H, A 376 Type 347H

Alloy 800 B407 UNS N08800

Alloy 800H B407 UNS N08810

Alloy 800HT B407 UNS N08811

HK-40 A608 Grade HK-40

7 Copyright © 2014 by ASME

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 TABLE 3 – ELASTIC ALLOWABLE STRESS FACTOR AND TABLE 4 – MINIMUM AND AVERAGE LARSON-MILLER
APPLICABLE TEMPERATURE RANGE PARAMETERS AS A FUNCTION OF STRESS IN MPA
Elastic Applicable Applicable Larson-Miller
Allowable Temperature Temperature Larson-Miller
Constant and
Material Stress Design Range (°F) Range (°C) Constant and
Parameter vs.
Factor Material Parameter Parameter vs.
Min. Max. Min. Max. Stress:
Fed Stress: Average
Minimum
Properties
Low Carbon Properties
2/3 70 1000 21 538
Steel
Temperature
Medium 371-538
2/3 70 1000 21 538 Range (˚C)
Carbon Steel
C 15.6 15.15
C-0.5Mo 2/3 70 1050 21 566
Medium A0 1.8864096E+04
1.25Cr-0.5Mo 2/3 70 1200 21 649 Carbon
Steel A1 -7.4232249E+02
2.25Cr-1Mo 2/3 70 1200 21 649
A2 -4.6595773E+02
3Cr-1Mo 2/3 70 1200 21 649
A3 -1.6666667E+02
5Cr-0.5Mo 2/3 70 1200 21 649 Temperature
427-649
Range (˚C)
5Cr-0.5Mo-Si 2/3 70 1200 21 649
C 22.05480 21.55
7Cr-0.5Mo 2/3 70 1200 21 649 A0 2.8854220E+04
1.25Cr-
9Cr-1Mo 2/3 70 1300 21 704 0.5Mo) A1 -3.5390260E+03

9Cr-1Mo-V 2/3 70 1300 21 704 A2 -1.9093061E+02

Type 304L SS 0.9 70 1500 21 816 A3 0

Type
0.9 70 1500 21 816
Temperature
427-649
304/304H SS Range (˚C)
Type 316L SS 0.9 70 1500 21 816 C 19.565607 18.9181
Type
0.9 70 1500 21 816
A0 2.8323097E+04
316/316H SS 2.25Cr-1Mo
Type 317L SS 0.9 70 1500 21 816
A1 -4.6611111E+03

A2 0
Type 321 SS 0.9 70 1500 21 816
Type 321H A3 0
0.9 70 1500 21 816
SS
Type 347 SS 0.9 70 1500 21 816
Type 347H
0.9 70 1500 21 816
SS
Alloy 800 0.9 70 1500 21 816

Alloy 800H 0.9 70 1650 21 899

Alloy 800HT 0.9 70 1650 21 899

HK-40 0.9 70 1750 21 954

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 TABLE 5 – RUPTURE EXPONENTS AS A FUNCTION OF
TEMPERATURE IN ºC

Material Parameter Rupture Exponent – n

Temperature
371-538
Range (˚C)
C0 2.8301495E+01

C1 -8.4274566E-02
Medium
Carbon Steel C2 1.0417814E-04

C3 -5.9090296E-08

C4 0

C5 0
Temperature
427-649
Range (˚C)
C0 1.7118412E+01 Figure 1 – Design Curve Showing the Larson-Miller
Parameter as a Function of Stress in US Customary Units.
C1 -4.4918106E-02 The Minimum Larson-Miller Constant (Cmin) is used to
Calculate Minimum Time-Dependent Properties and the
1.25Cr-0.5Mo C2 6.9267521E-05 Average Larson-Miller Constant (Cavg) is used to Calculate
Average Time-Dependent Properties: 2.25Cr-1Mo
C3 -6.6105728E-08

C4 3.4755747E-11

C5 -7.7605291E-15
Temperature
427-649
Range (˚C)
C0 1.5402535E+01

C1 -3.8933761E-02
2.25Cr-1Mo C2 6.6839103E-05

C3 -7.1745005E-08

C4 4.3121606E-11

C5 -1.1044439E-14

Figure 2 – Rupture Exponent as a Function of Temperature:

2.25Cr-1Mo

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 Figure 5 – The Average and Minimum Stress Rupture
Strengths as Functions of the Larson-Miller Parameter –
Figure 3 – The Behavior of Individual Lots Relative to One Comparison of Existing API Std 530 Data and Proposed New
Another on a Stress Verse Larson-Miller Parameter Plot Data in US Customary Units Based on the Average Larson-
Miller Constant: 2.25Cr-1Mo

Figure 4 – Yield and Ultimate Tensile Strength as a Function

of Temperature – Comparison of Existing API Std 530 Data
and Proposed New Data in US Customary Units: 2.25Cr-1Mo

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