Designing with Cold Rolled Stainless.pdf

Embed Size (px)

Citation preview

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    1/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 1 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    Designing with Cold Rolled Stainless Steel

    INTRODUCTION

    The high strengths which can be achieved by cold rolling Type 301 and Type 201 stainless steel, combined with their goodductility, weldability and inherent corrosion-resistance, are causing increased interest in these steels for corrosion-resistantstructures. As maintenance and associated labor costs continue to increase, expanded use of these stainless grades forlight-weight, corrosion-resistant structures is anticipated.

    The typical analyses of these grades are as follows (per ASTM A 240 requirements):

    Element Type 301 Type 201

    Chromium 16.00 - 18.00 16.00 - 18.00

    Nickel 6.00 - 8.00 3.50 - 5.50

    Manganese 2.00 Max. 5.50 - 7.50

    Carbon 0.15 Max. 0.15 Max.

    Silicon 0.75 Max. 1.00 Max.

    Nitrogen 0.10 Max. 0.25 Max.

    Through cold rolling of these metastable compositions, it is possible to increase the yield strength of the steel from about35,000 pounds per square inch to over 200,000 pounds per square inch. This hardening, produced by cold working, iscaused by the combined effects of (a) strain hardening and (b) the partial transformation of austenite to low carbonmartensite. During cold rolling, the metal is acted upon in a different direction by tensile and compressive stresses; as a

    result, the stress-strain curves in tension and compression, transverse or parallel to rolling, differ in their slopes andmagnitude. This anisotropic behavior causes some difficulty in evaluating the material for structural applications. Thesecharacteristics will be shown and discussed.

    Minimizing these directional properties, by stress relieving these materials after cold working, is of particular importance inevaluating these materials for structural applications. The effect of stress relief on the properties of cold rolled stainless willbe the major area of discussion in this blue sheet.

    The following data, column curves, and discussion define some of the basic properties of these steels and theirrelationship to design concepts. The basic discussion will be limited to Type 301 to reduce duplication of data. The relationbetween mechanical properties and strength of structural members is also applicable to Type 201, which can be cold rolledto similar strength levels and exhibits similar stress-strain curves.

    COLD ROLLED VERSUS STRESS RELIEVED PROPERTIES

    Table I shows typical properties of Type 301 in the various cold rolled tempers, and the effect of stress relieving treatments onthese properties. Figure I shows the stress-strain relationships for the half hard material in both the as-rolled and stress-relievedconditions.

    The as-rolled curve is typical of the anisotropic behavior which Type 301 also exhibits in the other tempers. The obviousdepression of the longitudinal compression curve is, at times, considered a limiting factor in the use of this material for structuralapplications. This low directional strength is compounded by the depressed slope or modulus of elasticity. The effect in structuraldesign is predictable due to the direct relationship of the modulus to buckling theory. Column test curves show this effect; notenough, however, to justify some of the perennial objections to this material that are based on this single direction

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    2/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 2 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    property. In any event, this problem is easily overcome by a low-temperature stress-relief treatment of the material.

    Reference to Table I shows the improvement in properties achieved by stress relieving. The right hand portion of Figure I showsthis effect even more

    Table I

    As-Rolled and Stress-Relieved Propert ies o f Type 301

    TemperCondition(As-rolledor 2 hrs.

    stress-relief)

    LONGITUDINAL

    Tension Compression

    TensileStrength,

    Ksi.2% Y.S.

    Ksi

    ElongationPercent

    in 2 inchesE0

    106

    psi.2% Y.S.

    KsiE0

    106

    psi

    Annealed

    1/4 Hard

    As-rolled 97 36 57 31.0 38 30.2

    As-rolled 139 80 42 28.0 50 28.2

    800 F 132 77 47 28.7 73 28.8

    1000 F 134 73 47 29.7 74 30.5

    1/2 Hard As-rolled 157 122 23 26.8 90 27.5

    800 F 155 128 24 27.9 111 29.2

    1000 F 152 120 29 28.0 113 28.8

    3/4 Hard As-rolled 176 142 17 25.8 100 26.5

    800 F 181 155 11 27.3 133 27.5

    900 F 176 151 11 27.5 133 27.9

    Full Hard As-rolled 186 160 15 25.2 115 24.6

    850 F 199 175 7 28.4 169 27.7

    1000 F 168 148 8 27.5 145 29.0

    Temper

    Condition

    (As-rolledor 2 hrs.

    stress-relief)

    TRANSVERSE

    Tension Compression

    TensileStrength,

    Ksi.2% Y.S.

    Ksi

    ElongationPercent

    in 2 inchesE0

    106

    psi.2% Y.S.

    KsiE0

    106

    psi

    Annealed

    1/4 Hard

    As-rolled 93 36 62 30.6 38 30.3

    As-rolled 139 84 40 28.6 91 28.2

    800 F 133 79 48 27.0 84 30.6

    1000 F 136 76 47 27.8 79 31.2

    1/2 Hard As-rolled 160 123 19 28.1 142 27.5

    800 F 157 130 18 28.6 144 29.8

    1000 F 151 122 26 27.9 132 29.0

    3/4 Hard As-rolled 180 145 13 27.5 170 27.9

    800 F 188 155 10 28.8 176 29.5

    900 F 184 154 10 28.3 175 28.5

    Full Hard As-rolled 204 163 11 28.4 191 29.4

    850 F 213 181 5 30.5 209 29.6

    1000 F 170 151 11 28.9 179 29.4

    dramatically. A comparison of these curves with the as-rolled curves shows the minimizing of the directional properties and, inparticular, the increase in longitudinal compressive strength. The slope or modulus of elasticity in this direction is also increased.

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    3/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 3 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    MODULUS OF ELASTICITY

    We have seen the effect of stress relieving on the strength properties of Type 301. The effect on modulus of elasticity is alsoof considerable importance, particularly in the compressive direction. The advantage in design becomes apparent, in view of

    the direct effect that initial modulus has on basic design considerations and particularly the effect of tangent modulus in sheetor plate buckling theory and column behavior. Figures II through V show the tangent modulus, plotted for the various tempersin both the as-cold-rolled condition and the stress-relieved condition. These curves are plotted for the longitudinal directiononly, since transverse properties are not adversely affected by cold working or a subsequent stress-relief.

    Stress-relief raises the tangent modulus values in tension, to some extent, but the effect on the compressive tangent modulusis considerable, raising it to values equivalent to that in tension. Since buckling behavior is related to these compressivevalues, the increased load-carrying ability of light gage members becomes significant. It will also be noted that the flat portionof the curves is extended, providing a greater range of nonanisotropic behavior.

    The combined modulus, which was suggested originally by Considere, Engesser and von Karmen to be used in the Eulerequation for columns stressed above the proportional limit, is easily arrived at in the following manner:

    The use of this modulus, which is somewhat higher than the tangent modulus, in the Euler equation agrees better, in mostcases, with actual column test results. This was shown by Lincoln and Watter (1). Subsequent work by Hammer andPeterson (2) at the Franklin Institute has verified the use of the combined modulus, particularly in the longitudinal direction.

    The work referred to was performed on as-cold-rolled material, employing the combined modulus derived from the tangentmodulus in this condition. The improvement in compressive tangent modulus, as shown in Figures II to V, and resultingimprovement in the combined modulus, as indicated by the above equation is of obvious advantage in designing columnsand other members subject to failure by buckling.

    COLUMN DESIGN

    The Euler column equation, in a form employing the combined modulus for a material with no definite elastic limit, takes thefollowing form:

    The curves shown in Figures VI through XI represent a compilation of data on column test work that has been performed oncolumns fabricated from the various tempers of cold rolled Type 301. The data is presented as a guide in predicting theallowable column loads for this material.

    Available test data on the effect of stress-relieved material in a column is limited to full hard material. These results areshown in Figure VI, along with the test results on columns fabricated from the same material in the as-rolled condition. Theanticipated increase in load-carrying capacity based on the increased modulus of the stress-relieved material is observed.

    Additional test curves are shown in Figures VII through IX for columns fabricated from 1/4 hard, 1/2 hard and full hardmaterial in the as-rolled condition. These curves are included to provide data on all tempers, indicating the excellent load-carrying ability of stainless in this condition. Theoretical curves based on the tangent modulus and combined modulus are

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    4/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 4 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    shown in each graph, along with the actual test data. Since it is expected that the increased modulus due to stress relievingwill result in increased load-carrying capacity, theoretical curves are also plotted, based on the moduli for the tempers in thestress-relieved condition.

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    5/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 5 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    No attempt will be made here to analyze the use of the combined modulus versus the tangent modulus for the variousdirections of testing, or their use for annealed versus rolled tempers. Although it is felt that the combined modulus provides,in general, a more accurate prediction of actual column behavior, there still exists a school of thought favoring the use ofthe tangent modulus in the Euler equation. The point that is of particular importance is that a low temperature stress reliefhas the effect of increasing the initial modulus and the tangent modulus which, as shown, increases the combined modulus.With these moduli increased as shown, the load-bearing capacity of a stainless column increases.

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    6/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 6 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    The column curves shown are from tests using a knife edge fixture, which results in an end fixity constant of one.

  • 7/29/2019 Designing with Cold Rolled Stainless.pdf

    7/7

    Data are typical, are provided for informational purposes, and should not be construed as maximum or minimum values for specificationor for final design, or for a particular use or application. The data may be revised anytime without notice. We make no representation orwarranty as to its accuracy and assume no duty to update. Actual data on any particular product or material may vary from those shownherein. TM is trademark of and is registered trademark of ATI Properties, Inc. or its affiliated companies. The starburst logo is aregistered trademark of ATI Properties, Inc. 2013 ATI. All rights reserved.

    VERSION 1 (5/10/2013): PAGE 7 of 7

    Allegheny Technologies Incorporated1000 Six PPG PlacePittsburgh, PA 15222-5479 U.S.A.www.ATImetals.com

    Technical Data Sheet

    Designing with Cold Rolled Stainless Stee

    SUMMARY

    The data and discussion presented show the advantages of the high strengths available in cold rolled stainless grades forstructural applications. The use of stress-relieved material, with the minimizing of directional properties and effect onmodulus, make this an even more attractive material for such applications.

    The data presented are for typical heats of Type 301 and are not guaranteed values. It is suggested, for critical designswhere a minimum factor of safety is to be employed, that the strengths, moduli, etc., be developed from the stress-straincurves for the material to be used. This procedure is very simple and, in some instances, reveals that higher design limits

    may be used compared to the typical values presented.

    An attempt has been made in this article to point out to engineers what appears to be a relatively new market for stainlesssteels, namely, their use for structural applications. Based on the data and discussion presented, it is obvious that stainlesssteel can be considered in many instances as an economical selection of material for structural components.

    REFERENCES

    1. WATTER, Michael and LINCOLN, Rush A., Strength of Stainless Steel Structural Members as a Function of Design,

    Allegheny Ludlum Steel Corporation, 1950.

    2. HAMMER, E. Walter and PETERSON, Robert E., Column Curves for Type 301 Stainless Steel, AERONAUTICALENGINEERING REVIEW, Vol. 14, No. 12, December, 1955.