A Six-Sigma approach will be used to optimize the process pa- rameters for helium-enhanced semi-permanent mold casting. A full factorial designed experiment will be run to characterize the helium injection process. A center point (run 5) will be used to check for non-linearity in the parameter settings, and an extra run will assess the effect of argon gas mixtures on the cooling rate and properties. Replicates may be run depending on observed experimental variation. Microstructure evaluation to characterize the grain size, SDAS, and porosity and property evaluation of the castings will be conducted. Finally, the projected cost sav- ings from reduced cycle time and reduced part volume (based on strength improvements) will be calculated. The additional costs associated with setup time and gas usage will be accounted for in the total cost analysis. The 2009 study showed a projected cost reduction of ~7% for permanent mold casting.
Status Update: The project is now well underway. Updates will be given at quarterly AFS Div. 2 Aluminum 2E committee meetings. The final results will be published as an IJMC paper and presented at the AFS Casting Congress. Those wishing more information about the project or how to participate as a sponsor should contact the Steering Committee chair Brian Began at
Brian.Began@
foseco.com or Prof. Paul Sanders at
sanders@mtu.edu.
High Strength Cast Iron Castings Produced by Engineered Cooling (12-13#06)
Coordinator: Dr. Simon Lekakh and AFS Ductile Iron, CG Iron & Gray Iron Research Committee (5-R)
The majority of industrially produced cast iron castings have a microstructure consisting of graphite phase in ferrite/pearlite metal matrix which were developed directly in metal casting processing (as-cast) without needing an additional heat treat- ment. The “as-cast” cast iron structure was formed during: (i) solidification (prime structure) and (ii) eutectoid reaction (fi- nal structure). The current state-of the art cast iron industrial processes mainly control the mechanical and thermo-physical properties through the prime solidification structure by:
• •
carbon equivalent variation for controlling prime aus- tenite/graphite eutectic ratio
inoculation treatment for graphite nucleation and de- creasing chill tendency
• magnesium treatment for controlling graphite shape (flake in GI, vermicular in CGI, and spherical in SGI)
• •
melt refining from dissolved impurities (S, O, N), and melt filtration for improving casting cleanliness.
Practically speaking, only one method―an additional alloying by Cu, Mo, Ni and other elements, is used for direct control of the structure of metal matrix formed during eutectoid reac- tion. The all described above methods could be called “chemi- cal” methods because they control the microstructure through changes in the cast iron composition. However “chemical”
methods have some serious limitations: (i) high cost of alloying additions, (ii) limited increase strength in as-cast condition, and (iii) need an additional austempering heat treatment for achieve- ment a higher strength of cast iron castings.
Analysis of the performance of standard cast irons with dif- ferent graphite shape and targeted properties according to this project are shown in Figure 1. The mechanical proper- ties data are represented by, so called “Quality index”, which is a strength/hardness ratio. For example, standard SGI is sig- nificantly stronger than CGI; however SGI has lower thermal conductivity which is a limiting factor for application for cast components of intensively thermo/mechanically loaded heavy- duty engines. The targeted properties for CGI produced by a novel process in “as-cast” are shown in Figure 1. The targeted strength of GI will be near the level of current CGI, and tar- geted strength of SGI in “as-cast” condition will be matched to the strength of heat treated castings.
The objective of this project is to develop a novel metal casting process for production of high strength cast iron castings in “as- cast” condition applying engineered cooling. The goals include:
• • • •
increase “quality index” (UTS/HB ratio) increase strength without sacrificing toughness decrease casting cost by eliminating alloying elements decrease energy consumption for heat treatment
Status Update: The project is now underway with the initial results with both continuous and isothermal cooling demon- strating some very interesting microstructures that are being developed and the approach to conduct the controlled cooling in test molds are being developed. The work is being moni- tored by the AFS Ductile Iron, CG Iron & Gray Iron Research Committee (5-R). Those wishing more information about the project or how to participate as a sponsor should contact the PI Simon Lekakh at
lekakhs@mst.edu.
Development of Ultra-High Strength Light Weight Al-Si Alloys (13-14#01)
Coordinator: Dr. M. Shamsuzzoha and AFS Aluminum Divi- sion 2
This proposal deals with the development of shape castings that produce high strength hypo- and hyper-eutectic alumi- num (Al)-silicon (Si) alloys with silicon content in the range of 6-9% and that possess nano-sized fibrous silicon morphology in the microstructure. In an Al-Si binary system, hypo-eutectic is formed with a silicon composition lower than 12.2 at% (12.7 wt%) of silicon. In the microstructure of hypo-eutectic Al-Si alloys, two major components coexist, the primary and the eu- tectic phase. The primary phase consists of Al containing about 1.67% Si as solid solution that exists in the form of dendrites, while the eutectic structure consists of an aluminum-rich solid solution of silicon and virtually pure silicon and that is found in between the arms of the primary Al dendrites.
International Journal of Metalcasting/Volume 8, Issue 2, 2014
91
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97