Transcript Heat Treating Processes
Supplementary Information Heat Treating Industry, Processes and Equipment
A seminar Presented for Southern California Gas Company Sales Staff
February 20 th , 2002
Presented By Arvind C. Thekdi - E 3 M, Inc.
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Specific Effects of Steel Heat Treating
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• Improve the Toughness • Increase the Hardness • Increase the Ductility • Improve the Machineability • Refine the Grain Structure • Remove the Residual Stresses • Improve the Wear Resistance
Heat Treating Processing Equipment
Gas Fired Furnaces
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Heat Treating Furnace
Process Atmosphere Exhaust Gases Heat Containment Energy Source (fuel, electricity, etc.) Heat Generation Heat Transfer Air Material Handling Heat Recovery Material Handling Arvind Thekdi - E3M, Inc.
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Heat Distribution in a Gas Fired Furnace (Typical)
Wall losses 10% to 20% Flue gas losses 35% to 65% Heat to work 20% to 40% Heat Storage 5% to 20% Atmosphere Losses 5% to 10% Fixtures, Baskets etc 15% to 40% Arvind Thekdi - E3M, Inc.
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Type of Heating Equipment
By Material Handling
Continuous Batch
• Belt Conveyor (Mesh or
Cast)
• Pusher Tray • Roller Hearth • Rotary Hearth • Rotary Retort (Kiln) • Shaker Hearth • Overhead Conveyor • Walking Beam • Box Furnaces • In & Out (Integral Quench)
Furnaces
• Bogy or Car-bottom • Gantry Furnaces • Bell Type • Pit Furnace • Fluidized Bed • Salt Bath
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Type of Heating Equipment
By Material Handling
Continuous
• Belt Conveyor (Mesh or Cast) • Pusher Tray • Roller Hearth • Rotary Hearth • Rotary Retort (Kiln) • Shaker Hearth • Overhead Conveyor • Walking Beam
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Type of Heating Equipment
By Material Handling
Batch
• Box Furnaces • In & Out (Integral Quench) Furnaces • Bogy or Car-bottom • Gantry Furnaces • Bell Type • Pit Furnace • Fluidized Bed • Salt Bath
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Radiant Tube Arvind Thekdi - E3M, Inc.
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Bell Type Furnaces
Muffle or Cover Burner Outside a Muffle
• Batch Furnace With High (2
to 100 Tons) Capacity Used in Mills and Heat Treat Shops.
• Primarily Used for Annealing
of Ferrous and Non-ferrous Strip or Wire Coils.
• Can Be Operated With a
Variety of Atmospheres Including 100% Hydrogen.
• Integral Cooling Coils to
Provide Accelerated Load Cooling.
• Includes High Capacity Fan
to Provide Convective Heating.
Radiant Tube Heated Vacuum Furnaces
• The load is heated in vacuum in absence of any type of gases.
• Usually batch type furnaces.
• Used for special heat treating processes .
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Fluidized Bed Furnace
• Consists of a Heat Resisting
Retort Heated by Gas Fired Burners or Electric Heating Elements.
• Contains “Sand” Bed That Is
Fluidized With Proper Velocity of the Required Atmosphere.
• Used for Small Parts. • Can Be Used for a Variety of
Heat Treating Processes.
• Gives Excellent Heat Transfer
and Temperature Uniformity.
• Can Be Designed to Give High
Efficiency and Low NOx Emissions.
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Pit Furnace
• Batch Type Furnace • Underground • Radiant Tube or Electric Heating • Relatively Low Heat Losses Due to Good Insulation • Used for Large or Large & Long Loads • Typical Loads Include Turbine Shafts, Gears, Pipes, Oil-field Components
Other Commonly Used Furnaces
• Retort Furnace (revolving) • Shaker Hearth Furnace • Car Bottom Furnace • Tip-up furnace • “Gantry” Furnace • Muffle Furnace • Box Furnace • Slot Furnace • Salt Bath Furnace
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Radiant Tube Heated Continuous Furnace
• A Continuous Carburizer for Heat Treating Large Volume Small Parts.
• Uses a Variety of Material Handling Methods (Belt, Rollers, Rails, Etc) and Trays, Baskets or Fixtures to Hold Parts.
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Process Atmospheres for Heat Treating
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Natural Gas or Ammonia Based Heat Treating Atmospheres
Use Natural Gas – Air Reactions or “Cracking” of Ammonia To produce the required gas composition
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Lean or Inert Exothermic (Exo) Gas
How are they made?
• Combustion of natural gas and air at near sub-stoichiometric * conditions • Water vapor removed from the products of combustion (flue gases)
Where are they used?
• Purging and Blanketing of Furnace Vestibules, Chemical Tanks, etc. • Annealing of Non-ferrous Alloys • Tempering & Bluing of Medium Carbon Steel (0.2% to 0.5% C) • Bluing of Silicon Steel Laminations, Electrical and Tool Steel
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* Sub-stoichiometric means that air flow to the burner is less than what is required to complete combustion
Rich Exothermic (Exo) Atmosphere
How are they made?
• Combustion of natural gas and air at sub-stoichiometric – rich * conditions • Water vapor removed from the products of combustion (flue gases)
Where are they used?
• Annealing of Forged Blanks • Annealing and Normalizing of Low to Medium Carbon Steels • • • • Bright Annealing, of Low Carbon (up to 0.2% C) Steels Motor Lamination Annealing Copper Brazing Sintering of Low Carbon Powdered Metals
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* Sub-stoichiometric means that air flow to the burner is less than what is required to complete combustion
Purified Lean and Rich Exothermic Gas
How are they made?
• Combustion of natural gas and air at or near sub-stoichiometric * or at rich conditions • Water vapor and carbon dioxide removed from the products of combustion (flue gases)
Where are they used?
•
Lean: Substitute for Commercial Nitrogen
– Annealing of Malleable Iron – Purging of Furnaces, Tanks With Flammable Liquids – Food Storage •
Rich: Substitute for Low Dew-point N2-H2 Mixtures in Heat Treating
– Powder Metal Sintering – Bright Annealing of Non-ferrous Metals – Annealing of Medium and High Carbon Steels
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* Sub-stoichiometric means that air flow to the burner is less than what is required to complete combustion
Endothermic (Endo) Atmosphere
(High Dew point)
How are they made?
• Products of reaction of natural gas and air at rich (highly sub stoichiometric) conditions in presence of a catalyst in an externally heated reactor or tube.
• External heat supply is required for production of endothermic atmosphere
Where are they used?
• Carburizing, Brazing and Sintering of Low to Medium Carbon Steel • • Bright Annealing, Carbon Restoration and Brazing of Medium and High Carbon Steels Annealing, Clean Hardening of Tool Steels and High Alloy Steels • Sintering of Powder Metal Parts
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* Sub-stoichiometric means that air flow to the burner is less than what is required to complete combustion
Dissociated Ammonia Atmosphere
How are they made?
• Dissociation (cracking) of ammonia (NH3) into nitrogen(N2) and hydrogen(H2) in presence of a catalyst in an externally heated reactor or tubes.
• External heat supply is required for production of dissociated ammonia atmosphere atmosphere • • •
Where are they used?
• Brazing and Sintering of Low Carbon Steels • Rapid De-oxidation of Metal Surfaces Purification of By-product Nitrogen for Annealing Bright Annealing of Stainless Steel, Silicone Steel Sintering of Stainless Steel
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Concerns About Generated Process Atmospheres
• Fixed composition – Lack of flexibility in gas composition – Variations in composition with turn-down – Difficulty in control – Dependent on natural gas composition that may vary seasonally • High capital investment • Resources required for operation and supervision. • Lack of reliable automation • Periodic maintenance (soot burnout etc.) requirements • Cost of repairs and maintenance for internal parts
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Industrial Gas Based Atmospheres
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Industrial Gas Based Process Atmospheres
• • • • • • “Sold” as: • • • “Engineered” Atmosphere Deliver Optimum Atmosphere to Meet Specific Application Flexibility in Delivery Options: PSA or Membrane Systems, Storage of Liquid Gases, Pre-scheduled Delivery, Service Etc.
Extremely Low (< - 90 F) Dew Point and Low (<5 ppm) Oxygen Precise Control of Dew-point and ppm Oxygen Levels at All Flows Lower Overall Cost Per Application (is Claimed!) Little or No Capital Investment Automated Operation Total Responsibility for Delivery - No Need for an Operator or Maintenance Personnel for Generators
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Comments and Considerations
Industrial Gas Based Process Atmospheres vs. Natural gas Based Atmospheres
In most heat treating operations cost of natural gas based atmosphere is lower than total cost of industrial gas based atmosphere
The total cost calculations must include factors such as: – Cost of gases as delivered and price changes – Cost of equipment rental and maintenance – Costs related to minimum gas usage and payment – Use of utilities related to production and/or distribution of the gases – Surcharges such as electricity cost – Cost of commitment for minimum contract period
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Cost Comparison
Endothermic Atmosphere vs. Nitrogen-Methanol
Basis
Natural gas for reaction Vaporized N2 Liquid Methanol N.G. to vaporize and dissociate methanol in furnace N.G. to supply heat in the generator N.G. to heat endo gas in furnace Electrical power Other - maintenance
Total Costs
Natural gas Nitrogen Methanol Electricity Maintenance
Fuel Fired Generator Amount
1000
200
cu.ft./hr.
cu.ft.
Cost
$0.90
Liquid Nitrogen Methanol Amount Cost
400 2.55
120 cu.ft. Gallons cu.ft. $1.20
$2.04
$0.54
125 64 1.5
cu.ft. cu.ft. Kw $0.56
$0.29
$0.11
$0.14
$2.00
$0.64
$4.42
$4.50 $3.00 $0.80 $0.07 $30.00 1000 c.f.
1000 c.f.
per gallon per Kwh per hour
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Electrical Heating Systems for Heat Treating
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Resistance Electrical Heating Systems
Shapes:
Rods, wire, shaped strips, etc.
Directly exposed or inside in an enclosure (tube) Size Range: Available in a wide variety of diameters, lengths and width
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Who are Vacuum Furnace Customers?
• 30% of All Heat Treaters Use at Least One Vacuum Furnace.
• 25% of Customers Plan to Add Vacuum Equipment During the Next 5 Years.
• Approximately 3,000 to 4,000 Vacuum Furnaces Are Used in U.S. and Canada.
• Approximately 100 to 300 Vacuum Furnaces Are Installed in U.S. • Primary Users: Aircraft and Aerospace.
• Growth Area: Tool and Die Makers and Automotive.
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Other Vacuum Applications
• Plasma Nitriding • Plasma Carburizing • CVD Coatings
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Induction Heating Major Advantages
• Low Scale and Scrap (Decarb, Distortion, etc.) Losses • • • • • • • • Lower Life-cycle Cost “Precise” or Better Control and Automation “Cool” Less Space - Smaller Foot Print Simpler Material Handling Ease of Start-up and Shutdown “Safe” Better Metallurgical Results
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Induction Heating
• • • • • • Major Disadvantages High Capital Cost High Energy Cost Lack of Flexibility for Production Parts Shape and Size Not Recommended for Progressive Heating, and Large and Complex Parts Requires “Specialized” Maintenance Skills & Personnel Not Recommended With Special Atmospheres
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Induction Equipment for Metal Heating
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Selected Sources for Information
Burner companies
Eclipse, Inc.
Kromschroder, Inc.
Maxon, Inc.
North American Mfg. Co.
Pyronics, Inc.
WS Thermal Process Technology Inc.
Address
1665 Elmwood Road, Rockford, IL 61103 1691 H Georgetown Road, Hudson, OH 44236 201 East 18th St. Muncie, IN 47302 4455 E. 71st. Street Cleveland, OH 44105 17700 Miles Avenue Cleveland, OH 44126 719 Sugar Lane Elyria, OH 44036
Phone
815.637.7217
216.342.0595
765.284.3304
216.271.6000
Fax
815.877.3443
216.342.0595
765.286.8394
contact
Mr. Jim Roberts Mr. George Paulonis Mr. Andy Jones 216.641.7852
Mr. David Gray
Web address
www.eclipse-inc.com
www.kromschroder.com
www.maxoncorp.com
216.662.8800
440.365.8029
216.663.8954
Mr. Tom Jarvis www.pyronics.com
440.365.9452
Mr. Joachim Wunning www.FLOX.com
Furnace Companies
Abar Ipsen Industries AFC-Holcroft Lindberg, A General Signal company Surface Combustion, Inc.
Address Phone
P.O. Box 6266 Rockford, IL 815.727.7625
61125 12068 Market Street 313.591.1000
Livonia, MI 48150 304 Hart Street 920.262.3993
Watertown, WI 53094 1700 Indian Wood Circle Maumee, OH 43537 419.891.7150
Seco Warwick Meadville, PA 16335-3618 814.332.8400
Wellman Furnace
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1 Progress Road Shelbyville, IN 46176 317.392.5268
Fax
815.332.4995
contact
Mr. Bill Kirchner
Web address
www.ipsen-international.com
313.591.6443
Mr. Jack Titus www.holcroft.com
920.262.3815
Mr. Patrick Weymer www.lindberg-bluem.com
419.891.7151
Mr. Max Hoetzl www.surfacecombustion.com
814.724.1407
Mr. Paul Huber www.secowarwick.com
317.392.5461
Mr. Bob Walton www.wellmanfurnaces.com
Batch furnace Captive heat treater Carburizing Commercial heat treater Continuous furnace Induction heaitng Integral quench furnace Limiting orifice Metering orifice Nitriding Protective Atmosphere Recuperator Vacuum furnaces Arvind Thekdi - E3M, Inc.
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Glossary
A type of furnace in which tha parts are kept at one place during heaitng process A company that performas heat treating operation on parts used for its own use A heat treating procsses that forms a hard iron-carbide layer on surface of a part to reduce wear of the part surface. A heat treating services company that provides services to a number of customer companies A type of furnace in which tha parts are continuously moving from one end to another end during heaitng process Heating of metal parts with magnetic fields generated in the part by using electric current A heat treating furnace that is used for heating and cooling (quenching) of parts A type of orifice or a valve used in gas supply line to limit maximum flow of gas that cen be supplied to a burner A type of orifice or a valve used in gas supply line to measure (meter) flow of gas supplied to a burner A company that performas heat treating operation on parts used for its own use A heat treating procsses that forms a hard iron-nitride layer on surface of a part to reduce wear of the part surface. A heat exchanger that is used to transfer heat from furnace flue gases to combustion air used in the burners A type of furnace in which vacuum is maintained during heating and cooling operation