Physical Metallurgy 20 th Lecture MS&E 410 D.Ast [email protected] 255 4140.
Physical Metallurgy 21 th Lecture MS&E 410 D.Ast [email protected] 255 4140.
-
Upload
armani-holaday -
Category
Documents
-
view
223 -
download
2
Transcript of Physical Metallurgy 21 th Lecture MS&E 410 D.Ast [email protected] 255 4140.
![Page 2: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/2.jpg)
Content
Review: Plain Carbon Steel
Alloy steels
Influence of alloying elements
Influence of hydrogen (unwanted alloy element)
HSLA Steel specification
Steel properties
Appendix: Read for 4/17
![Page 3: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/3.jpg)
1. Overview
a) Exceeds minimum alloy contents
b) Reasons for alloying elements
c) Nomenclature (AISI designation system)
d) Virtually always heat treated
![Page 4: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/4.jpg)
2) Alloying Elements and their Effects in Steel
Common classifications
a) High Strength Low Alloy Steels
b) Low Alloy Steels
c) Chromium-Molybdenum Steels (Tool Steels)
![Page 5: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/5.jpg)
Review : Carbon Steels
Only element > 1% is Mn.
P, S (except in electrical steels, Lect 20) are generally unwanted. Sulfur is sometimes added in controlled amounts to enhance machinability (embrittles) and P to increase hardening in particular during deep drawing (a cold working process where it can not move to GBs).
![Page 6: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/6.jpg)
Cu increases the corrosion resistance and has some solid solution hardening
Mn, in plain Carbon steels, works mostly to keep sulfur bound up so the it can not form FeS particles
Manganese increases the field (Hadfield steel is austenitic thanks to 13 % Mn) and is a potent carbide stabilizer. A stabilizer is an element that stabilizes the presence of an other compound.
Role of Si: General impurity in Fe (from sand) used intentionally to deoxidize steel or to increase electrical resistivity (transformer steel)
![Page 7: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/7.jpg)
Review: Classification
![Page 8: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/8.jpg)
Alloy steels
• Alloy steels have compositions that exceed the limitations of C, Mn, Ni, Mo, Cr, Va, Si, and B set for carbon steels.
• Exception: steels containing more than 3.99% chromium are classified differently as stainless and tool steels.
Alloy steels are always killed, but can use unique deoxidization or melting processes for specific applications.
Alloy steels are generally more responsive to heat and mechanical treatments than carbon steels (you may recall that heat treating 1020 is generally not worth the cost).
![Page 9: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/9.jpg)
Killed steels are steel that have been deoxidized by the addition of silicon or aluminium, before casting. (If you do not remember go back and revisit steel making, US and Europe, and continuing casting)
In this case there is no (significant) evolution of gas during solidification.
More generally, have a higher degree of chemical homogeneity and freedom from porosity
![Page 10: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/10.jpg)
If a “B” shows up it means Boron containing.
If “H” shows up means fits particular specs for hardenability
Designation AISI
![Page 11: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/11.jpg)
Alloy elements:
Added to make steel “better”. Can be
• Higher yield stress
• Higher ductility
• Higher hardness
• Better machinability
• Higher service temperature
• Better corrosion resistance
• etc….. application specific
![Page 12: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/12.jpg)
Change in lower yield stress point, low alloy steels
Solid Solution Strengthener
P is effective but when it gets into the GB it embrittles.
See lecture 20.
N is introduced by nitriding steel
![Page 13: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/13.jpg)
Elements that promote austenite, I.e. a larger field
• Ni
• Mn
![Page 14: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/14.jpg)
Ferrite forming elements
• Cr, Si, Mo, W and Al. • Fe-Cr alloys containing more than 13% Cr are ferritic at all temperatures up to incipient melting.
![Page 15: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/15.jpg)
Elements that lower Ms
Practically all ! If fully dissolved in phase
Ms = 561 - 474C - 33Mn - 17Ni - 17Cr - 21Mo
![Page 16: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/16.jpg)
Carbide-forming elements
• Cr, W, Mo, V, Ti, Nb, Ta, Zr. Affinity for Carobon increases from left to right
Some overlap with ferrite promoters (no accident think Fe3C )
• Non Fe containing carbidesCr7C3 W2C, VC, Mo2C.
• Double carbides contain both Fe and Carbide former e.g Fe4W2C.
• High-speed tool steels usually three types of carbides, which are usually designated M6C, M23C6 and MC. M represents sum of metal atoms. I.e M6C can represent Fe4W2C or Fe4Mo2C; M23C6 represents Cr23C6 etc. For how to stabilize these carbides at high T see Lect. 20
![Page 17: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/17.jpg)
Carbide stabilizers
The stability of the carbides depends on the presence of other elements in the steel. Chemical equilibrium between different carbids is measure by K . K is weight ratio of C in cementite vs C contained in the matrix. K values are
I.e. Mn will promote C to exist as Fe3C rather than being dissolved in the matrix. Thermo language would be that the activity of C is f(xi). Cr even more effective For that reason mallable cast iron (where you want the graphite to come out as globular C) can not contain any Cr.
![Page 18: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/18.jpg)
Nitrides
Nitride former are similar C former
TiN is a well known ultrahard compound. AlN precips distorts lattice and generates high dislocation density
Nitrided surfaces are extremely hard
![Page 19: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/19.jpg)
Nitrogen:
•Nitrogen can form a solid solution with ferrite at nitrogen contents up to about 6%.
• Above ~ 6% N, gamma prime ’ with a composition of Fe4N.
• Above ~ 8%, the equilibrium product is compound, Fe3N.
Nitrogen hardening is a “case hardening” process, producing a very hard thin layer at the surface. Ammonia, nitrogen plasma, or fluidized bed reactors are used
![Page 20: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/20.jpg)
Hydrogen
An unwanted element that generates, in high strength steels, hydrogen embrittlement. Hydrogen diffuses in metals, in trap limited diffusion process.
The effect is due, depending on the situation
a) weakening of the Fe-Fe bonds at the tip of a (growing) crack. The decohesion model can be explained with the effective d electron concentration (reviewed in prelim)
b) reformation of H into H2 molecules generating interior pressure (do the thermo, pressure is tremendous)
c) Hydrogen combining with C to form CH4 again forming high pressure bubbles.
d) hydrogen atmosphere around dislocation
![Page 21: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/21.jpg)
![Page 22: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/22.jpg)
Source of hydrogen
• cathodic protection,
• phosphating, pickling, and electroplating (notorious in high strength fasteners that also need to be corrosion resistant.
• welding with electrodes covered with coating containing moisture
• hydrogen used to cool (electric generators), reducing “air” friction (fly wheels), fuel (hydrogen economy)
Low strength not susceptible
High strength steel very susceptible.
![Page 23: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/23.jpg)
Destination of hydrogen Solubility of hydrogen is enhanced in triaxial tensile fields
![Page 24: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/24.jpg)
Diffusion is trap limited as first discovered by H. Johnson (look into the MS&E lounge)
![Page 25: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/25.jpg)
![Page 26: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/26.jpg)
The classic example is failure of retaining rings in hydrogen cooled electric generators
![Page 27: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/27.jpg)
Why megawatt electric generators use hydrogen cooling
• The specific heat capacity of hydrogen in constant volume is 10.25 J/(kg/°C)
• 14 times that of nitrogen
• 32.5 times more than one of argon.
• Additional Benefit: Low friction loss
![Page 28: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/28.jpg)
The problem is now much better understood, but led to some spectacular failures in the 70’s
Note that crack growth rate increases by an order of magnitude when hydrogen is present
![Page 29: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/29.jpg)
S-N (Woehler) curves
Note that fatigue limit falls to 1/5 of the value in air
![Page 30: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/30.jpg)
![Page 31: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/31.jpg)
Back to our alloy elements….
![Page 32: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/32.jpg)
More than 3 elements.
General approach is to lump all the austenite formers together as “effective Nickel” and all the ferrite formers as “effective Chromium”. Below is UK (Cambridge U)• Ni equivalent = (Ni) + (Co) + 0.5(Mn) + 0.3(Cu) + 25(N) + 30(C)
• Cr equivalent = (Cr) + 2(Si) + 1.5(Mo) + 5(V) + 5.5(Al) + 1.75(Nb) + 1.5(Ti) + 0.75(W)
Different authors have different weighting factors The approach is popular in the welding industry to predict the phase in a weld. Schaeffler diagram.
NOT an EQUILIBRIUM DIAGRAM. But neither is the Fe-C phase diagram… as we discussed
![Page 33: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/33.jpg)
Schaeffler Diagram (US)
![Page 34: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/34.jpg)
HW 21-1
Indicate in the diagram the position occupied by a weld made in
a) 316 Stainless
b) 440 C Stainless
![Page 35: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/35.jpg)
HSLA Steels
Total alloy content < 8 wt%Good combination of strength, formability, and weldability.
From the USS website
![Page 36: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/36.jpg)
![Page 37: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/37.jpg)
![Page 38: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/38.jpg)
I could not find the composition of these steels !
THE END
Next: Auxiliary Material (read for 4/17)
![Page 39: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/39.jpg)
Slides from ku.edu
![Page 40: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/40.jpg)
![Page 41: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/41.jpg)
![Page 42: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/42.jpg)
![Page 43: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/43.jpg)
![Page 44: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/44.jpg)
Reading Material on effect of alloying
Source
![Page 45: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/45.jpg)
![Page 46: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/46.jpg)
![Page 47: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/47.jpg)
![Page 48: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/48.jpg)
![Page 49: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/49.jpg)
![Page 50: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/50.jpg)
![Page 51: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/51.jpg)
![Page 52: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/52.jpg)
They mean embrittlement !!! MS correction took over
![Page 53: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/53.jpg)
![Page 54: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/54.jpg)
Ac and Ar are the eutectoid temperature in the Fe-C phase diagram, as they appear during cooling and reheating.
![Page 55: Physical Metallurgy 21 th Lecture MS&E 410 D.Ast dast@ccmr.cornell.edu 255 4140.](https://reader035.fdocuments.net/reader035/viewer/2022081516/551828e85503469d318b4d2f/html5/thumbnails/55.jpg)