High Performance Low Emission Carburizing Furnace Atmosphere Generation
High Performance, Low Emission Carburizing Furnace Atmosphere Generation & Control Using Rapid Laser-Based Gas Analysis October 11, 2000 Ronald R. Rich Atmosphere Recovery, Inc. and Ralph W. Larson Dana Corporation 1
Topics Presented • • • Carburizing Atmosphere Technology & Issues Atmosphere Gas Monitoring Needs & Methods ARI Laser Gas Analyzer (LGA)/Controller System Improved Process Development History New Approaches to Gas Carburizing with LGA Metallurgical Findings & Technology Status 2
Carburizing Use & Purpose Typical Parts (Gears) • • Typical Furnace (Batch) Improves Steel Wear Resistance on Part Surfaces (Adds Carbon) Maintains Steel “Toughness” at Part Depth (Lower Carbon) Parts to Heated to High Temperatures in a Gas “Atmosphere” Atmosphere Provides Reactive Chemistry Containing Carbon in 3 Gas Form in a Reducing Environment
Traditional Carburizing Atmosphere Air Endogas Natural Gas Composition: CO~20%, N 2~39%, H 2~39%, 1% CH 4, Balance: CO 2, H 2 O, O 2 Exhaust Stack At Metal Surface: 2 H 2+2 CO+3 Fe Fe 3 C+2 H 2 O+CO 2 3 Fe + CH 4 Fe 3 C + 2 H 2 4
Typical Carburizing Operation 5
Major Concerns Related to Atmosphere Carburizing • Process Control Problems with Existing Technologies – – Variable Production Part Parameters (Case Depth, %Carbon) Many Atmosphere Constituents Inferred Inefficient Control Algorithms to Employed to Reduce Sooting Limited Warning of Equipment Maintenance • Process Improvement Potential (Over 60 Years Old) – – • • Improved Part Quality & Performance Reduced Atmosphere Consumption Furnace Cycle Time Reductions Higher Performing Surface Treatment Options High Levels of Carbon Monoxide Air Emissions Inefficient Use of Atmosphere Gas and Energy 6
Most Industrial Furnace Atmosphere Gases Similar • Carburizing, Carbonitriding, & Nitriding – N 2, CO, H 2, CO 2, H 2 O, CH 4, O 2, NH 3, CH 3 OH • Atmosphere Tempering and Annealing – N 2, H 2, CO 2, H 2 O, CH 4, O 2, NH 3, Ar • Copper and Aluminum Brazing – N 2, H 2, CO 2, H 2 O, CH 4, O 2, NH 3, Ar • Powdered Metal Sintering – N 2, CO, H 2, CO 2, H 2 O, Cx. Hy, O 2 7
Typical Atmosphere Control Measures Only One Gas Species • Types – Zirconia Oxygen Probe – Measures Oxygen – Dew Point Meters – Measures Water Vapor – Electrochemical Cells – Low Range Single Gases • Benefits – Lower Capital Cost – Limited Calibration Requirements • Disadvantages – – – All Other Gas Constituents Not Measured or Controlled Many Assumptions About Other Gas Constituents Needed Requires High Atmosphere Flows for Adequate Control Inaccurate Correction for Most Atmosphere Variances Limited Process Control Variation & Improvement Options 8
Carburizing Atmosphere Monitoring Improved With Infrared Analyzers • Usually Measures Only Three More Gases – Carbon Monoxide – Carbon Dioxide – Methane • Does Not Measure Other Significant Gases – – Oxygen (Additional Sensor Required) Water Vapor (Theoretically Could) Hydrogen Nitrogen and Inert Gases • Non-Linear Response – Accurate Only Within Limited Concentration Range – High/Low Constituent Concentration Interference – Reference Cell Requires Frequent Calibration 9
Benefits of Complete Atmosphere Gas Analysis • • • Improved Carbon & Nitriding Potential Control Improved Oxidation/Reduction Potential Control Reduction in Atmosphere Consumption Allows Use of “Non-Standard” Atmosphere Gases Control of “Cleaner” Furnace Atmospheres – – Hydrogen/Nitrogen/Inert Combinations Carbon Dioxide/Hydrocarbon Mixtures Novel Mixtures for Improved Performance Sooting Reduced or Eliminated • Early Warning of Some Furnace Maintenance Issues • Potential for Reduced Furnace Cycle Times 10
Additional Benefits if Complete Atmosphere Analysis is Rapid (15 Seconds or Less) • • • “Real Time” Process Monitoring, Control and R&D Correlation with Existing Furnace Sensors “Non-Equilibrium” Atmosphere Operation Accurate Carburizing Rate Assessment Greater Potential for Reduced Furnace Cycle Times Drastic Reduction in Atmosphere Consumption Efficient Use of “Non-Standard” Atmosphere Gases Early Warning of Many Furnace Maintenance Issues Improved Furnace Performance and Safety Monitoring 11
Conventional Complete Gas Analysis Technologies • Gas Chromatography (GC) – – Moderate Price ($15, 000 - $60, 000) Slow (2 Minutes+) Frequent Calibration and Service Carrier Gas Needed • Mass Spectroscopy (MS) – – Higher Price ($50, 000 - $120, 000) Fast if Vacuum Already Present (Can be Slow if Not) Expensive to Maintain Equal Mass Gases Require Additional Analysis (GC) 12
Raman Gas Analysis Principals • • • Unique Frequency “Shift” for Each Type of Chemical Bond Measures Gases of All Types (Except Single Atoms) Rapid “Real Time” Response Rates Possible Signal Directly Proportional to Number of Gas Atoms 0 -100% Gas Concentrations Measured with One Detector Resolution and Accuracy Depends On: – – – Laser Power and Optics Variation (Including Cleanliness) Gas Concentration and Pressure Molecular Bond Type Background and Scattered Radiation Optical and Electronic Detector Circuitry 13
Some Atmosphere Raman Shift Spectra Source: NASA 14
Laser Raman Analysis Technologies • External Cavity Raman Lasers (Under Development) – – – Remote Fiber Optic Sensor Heads Higher Price Because of High Laser Power ($75, 000 - $300, 000) Fast Only if Laser Power High Expensive to Operate (Power, Cooling, Probe Tip? ) Laser Beam Dangerous Less Accurate • Internal Cavity Raman Laser (ARI’s “LGA” Design) – – – Gas Sample Flows Through Instrument Moderate Price ($25, 000 - $60, 000) Fast if Detectors Selective Low Cost Operation Safe Low Power Laser Beam 15
Multiple Port ARI LGA System Filter Furnace Gas 2 In Filter Individual Gas Detectors Valve Assembly Furnace Gas 1 In Filter Furnace Gas 3 In Filter Generator Gas In Individual Gas Detectors Gas Sample Tube Mirror Plasma Cell Polarizer Laser Beam Prism & Mirror Sample Pump & Pressure Control Gas Outlet 16
ARI LGA Detector Features • Gas Analysis Capabilities – 8 Gas Species Detected Simultaneously – Fast Detector Response (50 milliseconds) – 50 Parts per Million to 100% Concentration Range – More Accurate than NIST Calibration Gas Mixtures – No Zero and Span Gas Requirement (Optional) – Design Allows Customized Selection of Gas Species • Lifetime and Servicing – Two to Five Year Component Lifetimes – Ten Minute Detector Exchange – Individual Components Can Be Serviced and Cleaned 17
Additional LGA System Features • Integrated Sample Flow Control & Monitoring – Specialized Long Life Sample Filters (One Year +) – Internal Sample Pump and Calibration Valves – Low Volume Sample Gas Flows (200 ml/minute) – Electronic Flow and Pressure Monitoring – Optics and Enclosure Inerting (Standard for Atmosphere Analysis) – Multiple Sample Ports (16 + Optional) – Sample Line Purge and Back-flush (Optional) – High Dew Point Atmosphere Operation (Optional) • Integrated Electronics & Software – – – “Open Hardware” Pentium/Pentium III PC “Open Software” Windows NT 4. 0/Win 2000 Based Many Local and Remote Displays and Data Storage Options Available Analog and Digital I/O Options Multiple Configurable Process and PLC Interface Options 18
Interior View of Subsystems Laser & Gas Sensor Assembly Gas Flow Control Assembly Display, Keyboard, Serial & Network Ports Optional I/O Card Slots Pentium PC Based Monitor/Controller Gas Sample Pump Multi-Port Control Options Win NT or DOS OS & 4. 3 GB Hard Disk 19
Exterior View NEMA 4/12 Unit (131 o. F Maximum) Model 4 EN Furnace Atmosphere Analyzer Cooling Unit Electrical & Communication Sample, Calibration & Inerting Gas Inputs 20
Interior View NEMA 12 Unit LGA Unit Sub-Assembly Integrated Multi-port Valves Power & Network Connections Integrated Sample Filters Calibration & Purge Gas Regulators 21
Sample Software Control Screens Main Control Screen Atmosphere Analysis Values 22
LGA Carburizing Applications • External Atmosphere Generator Monitoring & Control • Complete Furnace Atmosphere Control Including: – – – Communications with PLC-Based Furnace Controller Real-Time Carbon Potential Correction of Oxygen Sensor Reduced Atmosphere Gas Usage & In-Situ Generation • Stand-Alone PC Based Control System Integrating: – – – Complete Furnace Atmosphere Control Improved Safety Monitoring Burner & Over Temperature Modules Oxygen Probes & Quench Tank Monitoring Part Load and Tray Tracking Interface with Plant SCADA and SPC Systems 23
Use for Rapid Generator Monitoring Expanded View Showing Rapid Variations 24
New Approaches to Carburizing Demonstrated at Dana Corp. Spicer Off-Highway Components Plymouth, MN 25
Plant Products and Processes • Products – Primarily Large Off-Road Axles and Gearsets – Some Interdivisional Component Carburizing • Atmosphere Heat Treat Processes – Five “Carburizing” Furnaces – Three “Endothermic” Generators 26
Improvements Initiated Because of New Air Emission Concerns • Previously Recognized Air Emissions – Smoke from Quenching – Burner Combustion Gases • Unrecognized Air Emissions Issues – Carbon Monoxide (CO) from Atmosphere Use – Comes from Atmosphere Generation, Leakage and Flaring - 10, 000 to 200, 000 ppm – Original “Potential to Emit” Estimate - 231 Tons Per Year (TPY) 27
Rapid Gas Analysis Process Development • 1993 -1994 Environmental & Air Quality Monitoring – Furnace Gas and Emission Testing – Options for Industrial Furnace Process Modification Identified • 1994 - Atmosphere Recovery, Inc. Founded – – – Carburizing Heat Treat Furnace Atmosphere Recovery Research Dana & USDOE Sponsored Research Program Intent to Produce Systems • 1995 -1999 - Constructed and Tested Prototype Systems – Numerous Papers and Presentations – Plant and Process Energy and Environmental Awards • 1999 -2000 – Laser Gas Analyzer Product Demonstrations – Endothermic and Exothermic Applications – Tests with “Non-Standard” Atmospheres 28
Batch Furnace Modifications • • • Side Pipe Waste Gas Exit with Cap Backup Safety Pressure Control Box and Dials Electronic Endothermic Gas Control Communication with Existing Controls Finding - Minimal Modifications Needed 29
Typical Test Load 2, 000 lbs. Driveshaft “Crosses” Side View Top View 30
Initial Demonstration Atmosphere Recovery Process IR-GC Later LGA Part of System 31
Prototype System IR-GC (Later Replaced by LGA) • • • Prototype Development, Assembly and Testing First Full Scale Operation - Aug. 6, 1997 Finding - Process Worked and Increased Furnace Productivity 32
Inter-Cavity Raman & GC Comparison on ARI Trial 33
System Location in Plant “Explosion Resistant” Test Area 34
Later Demonstrations Integral Atmosphere Generation LGA is Integral Part of System 35
Example Results for Rapid Carburizing 36
Parts Testing – Typical Load • Two Test Pins – One by Plant – One by Heavy Axle Division (HAD) • 3 or 6 “Standard Heat Code” 8620 Planet Gears Per Load – – Tested by Plant Standard Load Locations Three As Tempered Sometimes Three as Quenched • Three 8620/25/30 Test Pinions (Production Parts) – – Standard Load Locations All As Tempered One Tested by Plant Two Tested by HAD • Two Carbon Profiles (Bar by HAD, Rod by Plant) 37
Case Depth and Profile of Parts • RC 50 Value Case Depth Always Obtained Faster • Improvement Percentages Depends Primarily on Desired Final Case Depth (Shallower is Faster) • Less Case Depth Variation in Load • Hardness and Carbon Profile Consistent • Profiles Consistent with Higher Surface Carbon Potentials • Surface Hardness Also Acceptable • Surface Cleanliness not Significant (8620/8625/8630) 38
Retained Austenite/Carbides in Parts Baseline • • • ARI Accelerated “ARI Process Better (Lower Levels)” Levels Can Be Adjusted to Suit Desired Result Controllable Even with Wide Atmosphere Fluctuations 39
Grain Boundary Oxidation in Parts Baseline • • • ARI Accelerated “ARI Process Better (Lower Levels)” Levels Can Be Adjusted to Suit Desired Result Controllable Even with Wide Atmosphere Fluctuations 40
Metallurgical Findings Summary • Batch Cycle Times Faster (Load to Unload) – Same Process Temperature (Typically 1750 Deg. F. ) – Case Depth of. 040” – 35% to 50% Faster – Case Depth of. 065 – 20 -30% Faster • • Less Case Depth Variation Though the Load Controllable Carbon Content/Hardness Profile Controllable Retained Austenite Levels Controllable Iron Carbide Levels Wide Variation in Atmosphere Constituents Tolerated Advanced Soot Control Algorithms Do Not Affect Parts All Parts Released for Production 41
ARI Technology Status • Laser Gas Analyzer/Controller Systems Sales & Service – – – • • • Carburizing (Current Sales) Annealing (Current Sales) Nitriding (Future Sales) Brazing (Future Sales) Powdered Metal Sintering (Future Sales) Casting/Drawing (Future Sales) Integral Atmosphere Production Units Ready for Order Improved Atmosphere Recovery Prototype Ready for Trial Corporate Demonstration Sites Wanted 42
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