Forging Industry Technical Conference Columbus, OH Cooling Rates
Forging Industry Technical Conference Columbus, OH Cooling Rates of Microalloy Steels MPG: Nick Lindeke, Markus Knoerr, Zach Shea, Jose Gibaja, Chris Hudson, Freddy Villaverde, Ben Ritchey, Vince Angone; SFTC: John Walters, Brandon Templin September 19 & 20, 2016 Presentation Overview 1. Who is MPG and what happened to HHI? 2. Project Introduction and Background 3. Current Industrial Practice 4. Complete Project Overview
5. Report on Phase 2 work 6. Report on Phase 3 work 7. Conclusions HHI Forging is now MGP Forming Technologies MPG Forming Technologies Manufacturing Plants: HHI Forging Since August 2014 HHI has been part of MPG and this July all MPG companies have been branded under the MPG logo. Casting
Driveline Technologies Sintered Technologies Vibration Control Systems Introduction and Background In 2012 Professor Chet Van Tyne from the Colorado School of Mines presented FIERF with a proposal to perform research on determining optimal cooling rates for microalloyed forging steels. In reviewing this proposal John Walters from SFTC and Markus Knoerr from HHI (now part of MPG) discussed how the data developed by this project could be used to enhance the current industrial practice. It was decided that besides providing optimal cooling rates for the shop floor development of new parts, the data could also be used for advanced process simulation work that may allow for a faster development cycle in the future. This idea triggered additional work by the SFTC and MPG teams after the FIERF funded CSM project was completed on which we want to report today. Current Industrial Practice
Microalloy steels are Managanese steels alloyed with small amounts of Vanadium, Titanium and Niobium, which allows for the creation of a ferriticpearlitic microstructures with high strength and hardness through controlled cooling from the forging temperature. Examples of frequently used microalloys are: 38MnVS6, 15V30 and 15V40 Controlled cooling of microalloyed steels is now used frequently to eliminate post forge heat treating, such as quench and temper, to reduce cost and process time. Typical automotive parts made from microalloys are: Wheel End forgings Suspension forgings Balance shaft Automatic transmission output shaft Complete Project Overview Phase 1 funded by FIERF
Phase 2: determine HTC work performed by MPG & SFTC Phase 3 work performed by SFTC & MPG MPG & SFTC MPG & SFTC Colorado School of Mines SFTC Select production part Determine CC conveyor input data for simulation Run forging and CC simulation Hardness study of production parts Simulate forging and controlled cooling of production part Test cooling rate HTC
Hardness Cooling Rate Develop initial Heat Transfer Coefficient (HTC) from test data thru iterative simulations FIERF Project Develop target cooling rate Simulated cooling rate Hardness vs. cooling rate data for 38MnVS6, 15V30 & 15V41 Correlate cooling rate with mechanical properties using CSM data Phase2: Experimental Work to collect cooling data for HTC calibration Experimental data obtained by MPG and SFTC.
Characterize fans used in production Instrument of a sample part with thermocouples Heat in gas oven and cool using a stationary fan Collect temperature data during cooling Phase 2: Data Flow to Calibrate HTC Experimental data cooling temperature vs. time Simulate cooling with assumed heat transfer coefficient Use optimization engine to update HTC data Extract temperature vs. time at measured points and compare with experimental data N Does data match?
Y Export HTC data for use in production models Phase 2: Calibration of HTC Curves Original fit assumed lumped mass. Improved fit using zoned cooling: Fastest to cool (Zone 1) Slowest to cool (Zone 2) Intermediate (Zone 3) Separated radiation from convection. Phase 3: Production Run Data
MPG and SFTC selected a control cooled production part as a first candidate to evaluate the simulation potential. MPG recorded data during a production run: Atmosphere temperature Surface temperature vs time at 5 locations Videos of forging and cooling process Conveyor speed Wind speed at conveyor locations Average wind speed at conveyor 2 and the tunnel were comparable to the experimental wind speed used in Phase 2. Phase 3: Cooling Conveyor Set-up and
Cooling Conveyor Set-up used in production T1 Forge Press T2 Conveyor 1 T3 T4 Conveyor 2 T5 T6 T7 Conveyor 3 T8 Tunnel
Forge Box Cooling Fan T1-T8 DEFORM multiple operations Conveyor 1 = still air Conveyor 2 = zoned cooling Conveyor 3 = still air Conveyor 3 tunnel = modified zoned cooling Leave conveyors = final air cool Temperature Readings Phase 3: Cooling Simulation Zone 1
Zoned cooling for high velocity areas DEFORM default for low velocity areas Used average time at each conveyor HTC curves were not time dependent Fastest to cool Zone 2 Slowest to cool Zone 3 Intermediate Phase 3: Cooling Simulations A cooling simulation using the HTC curves developed in Phase 2 was compared to the production run data. Using the as-fit HTC curves produced:
Good agreement in the initial cooling rate. Too aggressive of a cooling rate inside the tunnel. The enclosed tunnel is a different environment than the open air test fixture. The HTC developed in Phase 2 had to be adjusted Phase 3: Cooling Simulations A good fit to the temperature profiles was obtained through a well tuned forging and cooling simulation.
HTC curves were scaled down in the tunnel Improved thermal contact in the forging simulation Phase 3: Verification of Simulation Results Visual comparison of heat patterns at various conveyor locations Enter Conveyor 2 Exit Fan 2 Start Conveyor 3 Phase 3: Hardness Correlation Colorado School of Mines identified a critical cooling rate for peak hardness. related to final microstructure 930 1290 F 0.7 1.6 F/sec MPG Data
SFTC Simulation The hardness at 2 locations was determined for 10 production parts. The cooling rate predicted by DEFORM was used to compare the hardness values to the CSM data. Conclusions The team has developed a basic technique that enables prediction of hardness obtained by control cooling of microalloy steels through process simulation. The prediction is based on data
generated by CSM in a FIERF funded research project and published in 2013. Heat transfer coefficients were developed for cooling parts on different types of conveyors The results of the simulation performed for an MPG production part show good correlation with the hardness data collected from two locations on the actual parts. MPG production hardness data for center area MPG Production Data MPG production hardness data for stem area SFTC cooling rate from simulation
Next Steps Continue analysis of current production part to confirm quality of correlation at additional locations on the part. Additional work is needed to understand and establish heat transfer coefficients for still air and forced air conveyor cooling both for open and closed conveyor systems. Currently cooling rate vs. hardness data from CSM study is only available for 38MnVS6, 15V30M and 15V41. Data for additional Microalloy steels would be needed. More research to better understand the effects of material composition on the cooling rate vs. hardness curve for microalloys would desirable.
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