John R. Paules, William P. Edwards, W. H. Clay Beringer The Effect of Forging Practice and Sulfide Inclusions on the Mechanical Properties and Fatigue Performance of Large Steel Crankshafts John R. Paules, William P. Edwards, W. H. Clay Beringer

Background The effects of forging practice, sulfur content, and sulfide inclusion morphology on the mechanical properties and fatigue performance of large, heat treated alloy steel crankshafts were evaluated. Crankshafts of similar size were produced using both a closed die, continuous grain flow procedure and an open die, “slab forged” technique. For each type of forging practice, the effects of sulfide non-metallic inclusions on anisotropy of mechanical properties and fatigue performance were studied. A non-calcium treated steel containing 0.008% sulfur was compared to a steel with lower sulfur content (0.001%) that was treated with calcium for inclusion shape control. Ellwood Crankshaft Group produces closed die, grain flow crankshafts with journal diameters up to about 300 mm. Above 300mm, and open die forging process is used. At the 2008 IFM Conference in Santander, we presented a study of the properties of large, open die forged crankshafts with hot-twisted bearings. Remains some question: Do the benefits of grain-flow forging decrease with cleaner steel? Purpose: compare open die vs. closed die forging practices for large, locomotive size crankshafts (240 mm journals)

Forging Methods Continuous Grain Flow Open Die

Open Die Forging, Twisting, and Machining of a Typical Large Crankshaft Open Die Forged Machined with “Necks” prior to Twisting 3. After Twisting 4. Finish Machined

Table 1. Compositions of the two experimental heats (weight %) Mn P S Si Ni Cr Mo V Cu Al Higher S, no Ca 0.45 1.09 0.008 0.28 0.18 1.12 0.32 0.053 0.15 0.019 Low S, Ca- treated 0.43 1.07 0.001 0.27 0.12 0.33 0.055 0.17 0.025 Two 45 MT heats Ladle refined, vacuum degassed Bottom Poured into 1,750 mm BEU ingots From each Ingot: 254mm round bars forged for CGF forging Large Slab shape forged in open die process

Photographs of Forged and Heat Treated Crankshafts Open Die Continuous Grain Flow

Macroetches of Throw Sections Open Die Continuous Grain Flow

Microcleanliness Ratings in Accordance with ASTM E45, Method A (Worst Field) Type A: Sulfides Type B: Alumina Type C: Silicates Type D: Globular Oxides Thin Heavy High S 0.5 -- Low S, Ca-treated 1.0

Typical Non-metallic Inclusions Observed at 100X, unetched: Left: MnS stringers in high Sulfur, non-Calcium treated steel Right: Globular oxide in low Sulfur, Calcium treated steel

Microstructures at the Pin/Web Fillet Location (200X, Nital Etch) Left: Closed Die Forging, Low Sulfur Right: Open Die Forging, High Sulfur Evidence of some banding in Open die Forged sample

Location of Macrotech Disks, Mechanical Tests, and Fatigue Tests Testing Main Journal Long. and Trans Tensile and CVN at Surf Mid-Rad Center Web Trans. Tensile and CVN Pin Long. Tensild and CVN Surface Mid-Rad 45 Deg. Web/Pin Tens and CVN Fatigue Test Bars oriented 45 degrees in Web

Low Magnification SEM Images of Charpy V-Notch Fracture Surfaces, Transverse Web “BB” Locations. Closed Die Forging, Low Sulfur Open Die Forging, Low Sulfur Left: Closed Die, Low S - 100 Joules Right: Open Die, Low Sulfur, 70 Joules - banding

Mixed Mode Fracture in the Segregation Banded Region of the Open Die, Low Sulfur Forging, Transverse Web “BB” Location Banded area – some cleavage fracture.

Good fatigue results for all conditions About 6% over fatigue limit for Closed Die, Low Sulfur

Conclusions Experiments with large, heat treated 4145-Modified crankshafts showed that:   Forging practice (open die, slab forging vs. closed die, continuous grain flow forging) and sulfur content do not have significant effects on tensile and yield strength levels at test locations throughout the interior of the crankshaft. Tensile ductility and notch toughness in the longitudinal orientation were not significantly affected by forging practice or sulfur content.

Conclusions (continued) When transverse specimens and specimens which were oriented 45° to the longitudinal direction were tested: the open die forged, high sulfur steel had the lowest ductility and toughness, the closed die forged, high sulfur and open die forged low sulfur samples displayed similar results, and the closed die forged, low sulfur sample had the best results. Similar fatigue limits were observed in the closed die, higher sulfur, open die, higher sulfur and open die, low sulfur samples. The closed die, low sulfur steel exhibited a fatigue limit that was slightly (~6%) higher than the other three samples.