Table 1. Composition (weight %) and mechanical properties of Eglin steel and other ultra-high strength steel alloys Alloy
C Mn Si
Wrought Eglin 0.26 0.65 Cast Eglin AF1410
AerMet100 0.23 HP 9-4-30
0.3 0.3 1
0.24 0.64 0.91 0.15 0.1 0.1 0.01 0.03 0.1
Cr Ni Mo Co W Yield Strength (ksi)
2.6
2.76 2
3.1 1
1 0.42 - 1.04 0.37 10
1
11.1 7.5
1 14
1.2 13.4 1
4.5
- 0.91 - - -
183 184 220 250 188
Table 2. Composition (weight %) of PH13-8+Mo, PH17-4 and PH17-4+Co used in the study Alloy
Al C
PH13-8+Mo 17-4PH
PH17-4+Co
1.14 - -
0.03 0.03
Co
- -
Cr Cu 12.7 Fe 16.24 3 Bal
0.05 Bal 0.16 2.23 0.49 0.11
0.013 3.05 16.35 2.96 Bal 0.42 -
ling the microstructure and properties, but one has not been developed for Eglin steel. Additionally, Eglin steel weld properties have not been mea- sured and optimized, which can limit the use of this new alloy. A continuous cooling transforma-
tion diagram provides valuable infor- mation on the phases that will form during general processing proce- dures, such as heat treatment, fusion welding and casting, which is useful for optimizing microstructure and properties. Understanding the varia- tion in weld properties in the fusion zone and the heat aff ected zone will allow proper selection and manipula- tion of welding parameters to ensure sound welds with optimal properties. T e researchers set out to develop a continuous cooling transformation diagram for Eglin steel and develop preliminary processing guidelines for welding to retain the mechanical properties of the weld. PH maraging stainless steel alloys
have a martensitic matrix. T e com- position of the three PH alloys used in the study can be found in Table 2. T ese alloys undergo an aging heat treatment to increase strength. T e aging forms precipitates in the matrix. PH17-4 and PH17-4+Co undergo copper precipitation, and PH13- 8+Mo undergoes β-NiAl precipita- tion to increase strength levels in the material. It is not yet known in detail
- -
- 0.2 0.056 0.2
how fusion welding processes aff ect the properties of these cast alloys, so researchers also set out to establish potential hardness variations within
Ultimate Tensile Strength (ksi)
237 238 240 285 230
Charpy (ft.-lbs.) @ -40C
20-30 -
55 35 20
Mn Mo N Nb Ni P S Si
7.87 0.008 0.008 0.21 3.96
0.02 0.005 0.75
Ta
- -
3.88 0.006 0.006 1.01 <0.01
fusion welds made on these PH alloys and develop post-weld heat treatment schedules that can be used to eliminate any soft zones within the welds.
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Jan/Feb 2014 | METAL CASTING DESIGN & PURCHASING | 43
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