High Performance, Low Emission Carburizing Furnace Atmosphere Generation

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High Performance, Low Emission Carburizing
Furnace Atmosphere Generation Control Using
Rapid Laser-Based Gas AnalysisOctober 11, 2000

• Ronald R. Rich
• Atmosphere Recovery, Inc.
• and
• Ralph W. Larson
• Dana Corporation

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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

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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 Gas Form in a Reducing Environment

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Traditional Carburizing Atmosphere
Composition CO20, N239, H239, 1 CH4,
Balance CO2, H2O, O2
Air
Exhaust Stack
Endogas
At Metal Surface 2H22CO3Fe ? Fe3C2H2OCO2
3Fe CH4 ? Fe3C 2H2
Natural Gas
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Typical Carburizing Operation
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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

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Most Industrial Furnace Atmosphere Gases Similar

• Carburizing, Carbonitriding, Nitriding
• N2, CO, H2, CO2, H2O, CH4, O2, NH3, CH3OH
• Atmosphere Tempering and Annealing
• N2, H2, CO, CO2, H2O, CH4, O2, NH3, Ar
• Copper and Aluminum Brazing
• N2, H2, CO, CO2, H2O, CH4, O2, NH3, Ar
• Powdered Metal Sintering
• N2, CO, H2, CO2, H2O, CxHy, O2

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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

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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

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Benefits of CompleteAtmosphere 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

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Additional Benefits if Complete Atmosphere
Analysis is Rapid(15 Seconds or Less)

• Real Time Process Monitoring, Control and RD
• 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

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Conventional Complete GasAnalysis 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)

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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

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Some Atmosphere Raman Shift Spectra
Source NASA
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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 (ARIs 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

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Multiple Port ARI LGA System
Valve Assembly
Furnace Gas 1 In
Filter
Furnace Gas 3 In
Filter
Generator Gas In
Furnace Gas 2 In
Filter
Filter
Individual Gas Detectors
Individual Gas Detectors
Gas Sample Tube
Laser Beam
Plasma Cell
Mirror
Prism Mirror
Polarizer
Sample Pump Pressure Control
Gas Outlet
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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

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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/Win2000 Based
• Many Local and Remote Displays and Data Storage
  Options
• Available Analog and Digital I/O Options
• Multiple Configurable Process and PLC Interface
  Options

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Interior View of Subsystems
Display, Keyboard, Serial Network Ports
Laser Gas Sensor Assembly
Optional I/O Card Slots
Gas Flow Control Assembly
Pentium PC Based Monitor/Controller
Gas Sample Pump
Win NT or DOS OS 4.3 GB Hard Disk
Multi-Port Control Options
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Exterior View NEMA 4/12 Unit
(131oF Maximum)
Model 4EN Furnace Atmosphere Analyzer
Cooling Unit
Electrical Communication
Sample, Calibration Inerting Gas Inputs
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Interior View NEMA 12 Unit
LGA Unit Sub-Assembly
Integrated Multi-port Valves
Integrated Sample Filters
Power Network Connections
Calibration Purge Gas Regulators
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Sample Software Control Screens
Main Control Screen
Atmosphere Analysis Values
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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

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Use for Rapid Generator Monitoring
Expanded View Showing Rapid Variations
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New Approaches to Carburizing Demonstrated at
Dana Corp.
Spicer Off-Highway Components Plymouth, MN
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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

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Improvements Initiated Becauseof 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)

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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

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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

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Typical Test Load 2,000 lbs. Driveshaft Crosses
Side View
Top View
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Initial Demonstration - Atmosphere Recovery
Process
IR-GC Later LGA Part of System
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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

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Inter-Cavity Raman GC Comparison on ARI Trial
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System Location in Plant
Explosion Resistant Test Area
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Later Demonstrations -Integral Atmosphere
Generation
LGA is Integral Part of System
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Example Results for Rapid Carburizing
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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)

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Case Depth and Profile of Parts

• RC50 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)

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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

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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

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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

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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