Use of Modeling in Production of Titanium Alloys. Titanium 2006 San Diego Dr Stephen Fox Dr. Vasisht Venkatesh TIMET

Transcription

1 Use of Modeling in Production of Titanium Alloys Titanium 2006 San Diego Dr Stephen Fox Dr. Vasisht Venkatesh TIMET

2 Why use computer modeling? Vacuum Arc Remelting Rolling, forging etc Thermodynamic modeling and microstructure prediction What does the future hold

3 Why Use Modeling? Process Development Margin $ and Competitive Position One failed full scale trial costs - $XXX,XXX Finite Element Modeling allows the engineer to test ideas that would not otherwise be tried. Bigger changes mean bigger impact

4 Why Use Modeling? Models don t work, take too long, easier to do the trial, we will end up doing the trial anyway Need to have predictions we trust to be of value

5 Months to run triple melt simulation on $25K Work station Fortran programming required for each simulation Research toy Hours to run triple melt simulation on $2.5K PC Interface automates intial set up from primaries through final melt Pool depths, chemistries all validated Implemented for all VAR development. VAR Melting Progress in 10 years Temperatures in ingot Chemistry in Ingot Closer Look at molten metal flow Solar Code Developed by Ecole Des Mines De Nancy and SOLAR Users Group

6 Open Die Forging Open Die Cogging is a key process for premium quality billet. Number of steps (up to 500 blows) presented challenges Cogging modeling in infancy. Months to complete few passes on $25K workstations Predicting temperatures, stresses and strains. Limited value 2002 First microstructure predictions implemented in DEFORM Alpha volume fractions, Alpha particle shape Volume Fraction of Spherodized alpha. Template to program multiple forging and reheat steps without intervention. Small Die Advance/Increment Large Die Advance/Increment

7 Open Die Multiple passes complete in days on $2.5K PC Routine use to support process improvement for Microstructure Ultrasonic noise Yield and productivity Optimized solutions often go against conventional thinking.

8 Bar Rolling Predicting Cracking in rolling and forging Seams and cracking is a common problem in bar/bloom rolling. Strain induced porosity is an occasional issue for some alloys Robust empirical solutions had proved elusive Combining prediction of cracking led to redesigned pass sequence to eliminate cracking Design processes with balance of experience and science. Eliminate the black art

9 Plate Rolling Challenges for simulating plate rolling. Shape - Flatness and residual stresses Texture Additional key microstructure features Ultrasonic Properties

10 Predicting Structure and Properties Multiple linear regression approach link process details and tensile properties in CP Titanium strip Some empirical relationships between microstructure and fatigue for limited products Phase diagram predictions for transformations demonstrated R&D tools 2002 Neural Network approach MAI/USAF Standardized approaches to microstructure measurements Relate individual microstructure features to tensile properties. Key features identified. Not all are obvious 2006 Progress Testing thermodynamic software for use in product release Predicting structures after final heat treatment to avoid measurement Integration putting it all together Incorporating texture prediction in commercial codes

11 Predicting Beta Transus and Approach Curves 1 Ti-Al-V-Fe-O-C Measured Optically PANDAT 0.7 Alpha Fraction Temperature, F

12 PANDAT Data Flow for Production Use Approach Curves on Certificates QA SYSTEM Text Files chemistries BATCH PROCESSED Batch Processor Program PANDAT.EXE Text Files Approach curves

13 Predicting Microstructures Courtesy of OSU Grain Growth Slower Cooling Faster Cooling

14 Benefits of Process Modeling Predict Effect of Processing (including melting) Temperature Use modeling to focus experiments and increase confidence Strain - How the metal moves How quickly things change (Strain rates, cooling rates) Predict How processing changes microstructure Predict how microstructure changes properties Talk to Designers Reverse the process and shorten development cycle Implement Change

15 Summary Why Simulate processing? Integrate into Design Quality Process control Development From raw materials to finished products to deliver reduced development time and costs. Biggest Payoff comes when we integrate manufacturing with product and component performance.