This NASA component for the space shuttle crawler transporter, produced with modified 4320 steel alloy via V-process casting, met reduced surface hardness requirements while maintaining high material strength when compared to its previous design.


in severe environments, such as saltwater. Heat-Resistant Steel—Used in


temperatures exceeding 1,200F (649C) and as high as 2,400F (1,316C), heat- resistant steel is compositionally similar to corrosion-resistant steels with higher carbon content (between 0.3% and 0.6%), which gives it higher rupture strength.


Design Considerations


By selecting the steel composition and heat treatment, a wide range of properties are available to designers. Choosing an alloy composition and heat treatment to improve one property may result in the reduction of another prop- erty. For example, higher hardness, lower toughness and lower ductility values are


Online Resource


Visit www.metalcastingdesign.com to read more articles on designing, speci- fying and purchasing steel alloys.


2013 Casting sourCe DireCtory Table 2. Fatigue Properties of Cast Carbon and Low Alloy Steels


Class and Heat Treatment


60 A 65 N 70 N


80 NT 85 NT


100 QT


65 NT 70 NT 80 NT 90 NT 105 NT 120 QT 150 QT 175 QT 200 QT


Tensile Strength (ksi)


63 68 75 82 90


105


68 74 86 95 110 128 158 179


205


Yield Strength (ksi)


Carbon Steels 35 38 42 48 55 75


Low-Alloy Steels 38 44 54 64 91


112


142 160 170


Elongation


30 28 27 23 20 19


32 28 24 20 21 16 13 11 8


%


Hardness BHN


131 131


143 163 179 212


137 143 170 192 217


262 311


352 401


A=Annealed; N=Normalized; NT=Normalized and tempered; QT=Quenched and tempered. Metal Casting Design & PurChasing 23


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