SAE J 2515-1999 High Temperature Materials for Exhaust Manifolds《制作排气导管的高温材料》.pdf

1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro

2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT

3、 ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1999 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001STANDARDSubmitted for recognition as an American National StandardJ2515I

4、SSUEDAUG1999Issued 1999-08High Temperature Materials for Exhaust Manifolds1. ScopeA subcommittee within SAE ISTC Division 35 has written this report to provide automotive engineersand designers a basic understanding of the design considerations and high temperature material availabilityfor exhaust m

5、anifold use. It is hoped that it will constitute a concise reference of the important characteristicsof selected cast and wrought ferrous materials available for this application, as well as methods employed formanufacturing. The different types of manifolds used in current engine designs are discus

6、sed, along with theirrange of applicability. Finally, a general description of mechanical, chemical, and thermophysical properties ofcommonly-used alloys is provided, along with discussions on the importance of such properties.1.1 BackgroundFigure 1 provides a diagram of a typical fabricated exhaust

7、 manifold, in this case for one sideof an eight-cylinder engine. Cast versions are similar in geometry. In simple terms, it provides a means ofcontaining exhaust gases generated from each cylinder within the engine block, combining the volume, andpassing the gas on to the catalytic converter.FIGURE

8、1FABRICATED MANIFOLDOperating demands on exhaust manifolds, as with many other elevated temperature engine components,have increased significantly over the past decade. There are numerous reasons why this has occurred,including the usually-cited reasons of tighter emissions requirements, improved fu

9、el efficiencies, and designtoward higher specific engine power (kW/kg), with a cumulative end-effect yielding higher exhaust gastemperatures. Techniques used to meet emissions requirements, such as the addition of air injection systemsand the use of controlled variations in air-fuel ratios, have cha

10、nged overall hydrocarbon levels, and, undercertain conditions, have increased the emissivity of the exhaust gas, further raising the manifold inner walltemperature. This has led to much higher elevated temperature strength, creep, and fatigue demands onCOPYRIGHT Society of Automotive Engineers, Inc.

11、Licensed by Information Handling ServicesSAE J2515 Issued AUG1999-2-exhaust manifold alloys. Radioactive heat shields that are now used to protect underhood electronics fromhigh temperatures further exacerbate the issue by reflecting otherwise lost heat back on to the manifold.Such thermal demands l

12、ead to reduced alloy strength simply from the higher temperatures, but perhaps moreimportantly higher internal stresses can also develop from the higher thermal gradients via thermal expansionmismatch considerations in the cylinder head - manifold interface. The cumulative effect then becomes higher

13、temperatures in combination with higher cyclic stresses. Thermal fatigue, a condition in which time-dependentstress variations occur directly as a result of thermal expansion mismatch and mechanical constraint, becomesan important issue. Distortion, gas blow-by, and cracking of metal components resu

14、lt. To avoid suchproblems, designers have had to examine stronger alloys and employ alternate mechanical designs.2. References2.1 Applicable PublicationsThe following publications form a part of this specification to the extent specifiedherein.Charles F. Walton, Iron Casting Handbook, Iron Casting S

15、ociety, 1981Stephen I. Karsay, Ductile Iron I Production, QIT Fer et Titane, Inc., 1992Michael F. Burditt, Ductile Iron Handbook, American Foundrymens Society, Inc., 19923. Alloy Classes and General PropertiesBefore manifold design and use can be discussed in any detail, it isnecessary to review som

16、e of the more basic issues regarding the material classes that are used to make them.3.1 Cast IronDiscussion of cast iron metallurgy will be brief, as excellent references are readily available.1,2,3.In very basic terms, cast irons are comprised of iron and large amounts (1% by weight) of carbon (C)

17、, andcontain two primary microstructural components, a free graphite phase and the surrounding matrix. “Gray” and“Ductile” iron, two of the most common types of cast iron in general, and certainly the most typical for exhaustmanifolds, differ in the form of their free graphite. In gray cast iron, gr

18、aphite is present in the form of clusters ofthin, two-dimensional flakes, while in ductile (nodular) iron it is in the form of spheres, or nodules. A cast ironmatrix can be ferritic, pearlitic, some combination of ferrite and pearlite, or, with addition of suitable amounts ofaustenitizing elements,

19、entirely austenitic. Austenitic matrix irons are also known as Ni-Resist. The matrix of acast iron can be varied independently of the graphite form, so both gray and ductile irons can be ferritic,pearlitic, or austenitic. The different graphite forms and matrix microstructures are created by using s

20、pecialalloying additions and inoculation practices. Silicon (Si) and carbon provide the primary influence on graphitetype and amount. The combination of graphite form and matrix microstructure give each type of cast iron itscharacteristic mechanical and physical properties. For instance, flake graph

21、ite alloys (gray iron) typicallyexhibit the lowest toughness and resistance to crack growth of all the cast irons, but they are also the leastexpensive to make, and the graphite flakes very effectively dampen sound and conduct heat well. Nodular, orductile irons exhibit better toughness, will conduc

22、t heat more sluggishly, and are more expensive to produce.Tables 1 to 3 provide a summary of important properties associated with nodular cast irons used in manifoldproduction. Gray iron properties are not included since they are not of current interest.1. Charles F. Walton, Iron Castings Handbook,

23、Iron Casting Society, 19812. Stephen I. Karsay, Ductile Iron I Production, QIT - Fer et Titane Inc., 19923. Michael F. Burditt, Ductile Iron Handbook, American Foundrymens Society Inc., 1992COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J2515 Issued AUG19

24、99-3-TABLE 1COMPOSITIONAL AND MICROSTRUCTURAL CHARACTERISTICSOF DUCTILE CAST IRONFerritic DuctileSi-Mo DuctileGrade A(1)1. Difference in grades is primarily in the Molybdenum content.Si-Mo DuctileGrade B(1)Si-Mo DuctileGrade C(1)Carbon 3.80% 3.45% 3.45% 3.45%Silicon 2.70-3.00% 4.00% 4.00% 4.00%Sulfu

25、r 0.015% 0.02% 0.02% 0.02%Magnesium 0.020% min 0.020% min 0.020% min 0.020% minMolybdenum N/A 0.80-1.0% 0.50-0.70% 0.40-0.60%Copper 0.10% 0.10% 0.10% 0.10%Manganese 0.20-0.40% 0.20-0.40% 0.20-0.40% 0.20-0.40%Phosphorus 0.04% 0.04% 0.04% 0.04%Chromium 0.10% max 0.10% max 0.10% max 0.10% maxNickel 0.1

26、0% 0.10% 0.10% 0.10%Ferrite Balance Balance Balance BalancePearlite(2)(3)2. Amounts vary depending on section size and presence of heat treating (process dependent), or as required by customer.3. Area percent of matrix excluding graphite area; total matrix constituents = 100%, excluding graphite.10-

27、15% 10-15% 10-15% 10-15%Carbides 0-1% 2-3% 1-2% 0-1%Graphite Nodularity 95% + 95% + 95% + 95% +TABLE 2ELEVATED TEMPERATURE MECHANICAL PROPERTIES OF DUCTILE CAST IRONFerritic DuctileSi-Mo DuctileGrade A(0.8-1.0% Mo)Si-Mo DuctileGrade B(0.6-0.8% Mo)Si-Mo DuctileGrade C(0.4-0.6% Mo)Elongation 16-20% 10

28、-14% 12-16% 14-18%Tensile Strength22 C (72 F)316 C (600 F)427 C (800 F)538 C (1000 F)649 C (1200 F)704 C (1300 F)MPa5654903862489061MPa60153541429312383MPa59252440728211578MPa58851840427611175Yield Strength22 C (72 F)316 C (600 F)427 C (800 F)538 C (1000 F)649 C (1200 F)704 C (1300 F)MPa331-365MPa46

29、84093792639271MPa4624043702538366MPa4594013662497963Elongation22 C (72 F) 16-20% 8-12% 10-13% 11-14%CompressiveStrength (MPa)234 356 354 353Modulus Elasticity 170 GPa 145-170 GPa 145-170 GPa 145-170 GPaCOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J2515

30、Issued AUG1999-4-TABLE 3PHYSICAL PROPERTIES OF DUCTILE CAST IRONFerritic DuctileSi-Mo DuctileGrade ASi-Mo DuctileGrade BSi-Mo DuctileGrade CThermal Conductivity(W/K x cm)20 C100 C400 C1000 C0.330.400.330.24N/A0.250.270.25N/A0.250.270.25N/A0.250.270.25Coefficient of ThermalExpansionTemp (C)20-10020-2

31、0020-30020-40020-50020-60020-76020-871x106/C11.212.212.813.113.513.714.815.3Density (at 20 C) 6.9 g/cc 6.9 g/cc 6.9 g/cc 6.9 g/ccDBTT(1) CharpyImpact PropertiesNotched:10 C to 65 C astensile increasesUn-notched:60 C to 10 C astensile increases1. Ductile to Brittle Transition TemperatureAt 22 Cnotche

32、d 13.519.0 jnotched, ductilefracture: 16.3-21.7 jun-notched, ductile fracture: 94.9-135.6 jun-notched, brittlefracture: 2.7-4.0 jN/A N/A N/ACreep StrengthTemp C427538649MPa 0.0001%/h rate96.527.73.09N/A N/A N/AHardness (HB) 143-217 192 192 192Fatigue StrengthEndurance LimitUn-notchedV-notched193 MPa

33、117 MPaN/AN/AN/AN/AN/AN/APoissons ratio 0.28 0.28 0.28 0.28COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J2515 Issued AUG1999-5-3.2 Stainless SteelStainless Steels are selected for elevated temperature applications because of theirexcellent strength and

34、resistance to oxidation and corrosion. Both cast and wrought versions are available.Additions of Chromium (Cr) to iron in amounts greater than approximately 12% will result in an alloy that willnaturally form on its surface a tenacious chrome oxide passive film (chromia, Cr2O3). This film tightly ad

35、heresto the base alloy (in contrast to “red rust” on carbon steel which easily cracks and spalls) and protects theunderlying metal from further oxidation at high temperature, or corrosion from other factors such as sulfur-bearing gases or chloride containing aqueous solutions.Iron with the addition

36、of 11% to 30% Cr comprises a host of ferritic stainless steels. These alloys are primarilycharacterized as having a BCC structure, are ferromagnetic, and are less expensive than their austeniticcounterparts. High temperature oxidation resistance tends to be very good to excellent, partly because the

37、thermal expansion coefficient of the alloys and chromia are similar, limiting scaling of the chromia during cyclicthermal conditions. While considering the ferritics for welded fabrications, it is important to maintain extremelylow levels of carbon and nitrogen so that matrix chromium levels are not

38、 depleted by the formation ofchromium carbonitrides. Improved weldability, formability, and corrosion resistance will result when theseinterstitial elements are controlled to low levels. Ferritic stainless steels are preferred in fabricated exhaustsystems due to their cost advantage over the nickel

39、(Ni) containing austenitics. Another important advantageis the low coefficient of thermal expansion (40% less than austenitics) which minimizes stresses generatedfrom thermal growth at operating temperatures.Nickel, when added to stainless steels in percentages ranging from 6% to as high as 35%, wil

40、l lead to an FCCor austenitic structure at room temperature. These austenitic stainless steels typically possess much betterdeep drawability, weldability, and elevated temperature strength than the ferritic grades. The austenitic alloyswith moderate additions of other refractory elements, e.g, Molyb

41、denum (Mo), Niobium (Nb), Titanium (Ti),exhibit even better corrosion resistance and further enhanced elevated temperature properties. Austeniticstainless steels exhibit superior elevated thermal mechanical properties in comparison to ferritic, pearlitic, andmartensitic cast irons, as well as ferrit

42、ic stainless steels.Both ferritic and austenitic stainless steels are susceptible to the formation of internal chromium rich carbidesat high temperature by a reaction between the chromium and carbon/nitrogen in the alloy. This is otherwiseknown as sensitization. Sensitization can lead to severely re

43、duced corrosion resistance, because the localconcentration of chromium near these carbide particles can be reduced to well below the nominal alloy level. Iftime and temperature are insufficient to allow back diffusion (or “healing”) into the area near the carbides,chromium-depleted regions will exis

44、t adjacent to the carbide network. If the network is continuous, a path oflower corrosion resistance will exist through the material. Sensitization can also lead to reduced strength andfracture resistance, particularly with the ferritic stainless grades. A common means of mitigating sensitizationis

45、by employing “stabilization” of the base alloy. This term refers to the addition of small levels of refractoryelements, that are more reactive with carbon and nitrogen than chromium, e.g., Ti and Nb, to tie up theinterstitial carbon/nitrogen, thus preventing further reaction with Cr. Thus, the chrom

46、ium carbide formation thatcould occur during high temperature exposure is minimized. This is the primary method used to address thesensitization of ferritic stainless steels which are put into service in the as-welded condition.The temperature ranges in which austenitic alloys become susceptible to

47、sensitization are different than theferritic counterparts. In the as-welded form, corrosion resistance in austenitics can be achieved through theuse of low carbon chemistries (e.g., 304L) or by stabilization (e.g., 321 or 347). Applications in whichaustenitic stainless steels are put into service at

48、 sensitization temperatures require additional consideration.Physical, chemical, and mechanical properties of some of the more commonly-used wrought stainless steelsare shown in Tables 4 to 6. Additional elevated temperature properties are listed in Table 7.COPYRIGHT Society of Automotive Engineers,

49、 Inc.Licensed by Information Handling ServicesSAE J2515 Issued AUG1999-6-TABLE 4PHYSICAL PROPERTIES AT ROOM TEMPERATUREProductDesignationDensityg/ccYoungs Mod.GPaTherm. Cond.W/m/KCTE(1)cm/cm/C1. Coefficient of thermal expansion.Cost$/lb409 8 206 25 14 1439 8 196 24 13 1444 7 13 1.75(2)2. Indicates estimated value.441 8 206 24 12 1468 8 200 25 14 1304 8 193 16 20 2309 8 200 16 20 3321 8 193 16 20 2601 8 207 11 17 8TABLE 5CHEMISTRY OF COMMONLY-USED STAINLESS STEELSProductDesignationComposition,WeightPercentCComposition,WeightPerc