heat treating — choosing & using polymer quenchants
TRANSCRIPT
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Quenching – Mastering the Process
D. Scott MacKenzie, PhD, FASM
December m 2011
Choosing and Using Polymer Quenchants
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Quenching – Mastering the Process
• Real loads are complex– Important to meet properties
and reduce distortion– No quantitative method to
understand interaction of fluid flow and part
– Often understanding is “Trial and Error”
– Experience trims the Heuristic tree
– Heat transfer mechanism is complex
• Multiple heat transfer regimes
• Time and Temperature dependent phase transformations
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Quenching – Mastering the Process
• Mechanism of Quenching– Quenching occurs in three stages
• Vapor Phase– Formation of vapor film around the part– Heat transfer is slow– Heat transfer occurs primarily through radiation and conduction through
vapor• Nucleate Boiling Phase
– High heat extraction rates– Heat removal by bubble formation and contact of cool quenchant on
part surface• Convection Phase
– Starts at below boiling temperature of quenchant– Slow heat transfer
– Governs Properties and Distortion
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Quenching – Mastering the Process
• Factors Affecting Cooling Rates– Two factors
• Ability to diffuse heat out of the part (thermal diffusivity)• Ability of the quenching medium to remove heat.
– Thermal Diffusivity• Ability of steel to transfer heat• Changes as a function of temperature• Very little change as a function of composition
– Quenchant• Most important control over cooling rate• Complex process
– Depends on radiation, boiling and forced and unforced convection– Agitation, quenchant temperature and concentration (if polymer quenchant)
primary factors• Important practical considerations
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Quenching – Mastering the Process
• Quenching Mediums– Many different types
• Water
• Brine
• Caustic
• Polymer (Aqueous)
• Oils
• Molten Salts
• Gases
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Quenching – Mastering the Process
• Different types of Polymer (Aqueous) Quenchants
– Polyalkylene Glycol (PAG)– Sodium Polyacrylate (ACR)– Polyvinyl Pyrrolidone (PVP)– Polyethyl Oxazoline (PEO)– Hybrid Polymer Quenchants
• Ability to tailor quench rates to specific applications
• Quench rate affected by:– Temperature– Agitation– Concentration– Contamination and Degradation
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Quenching – Mastering the Process
• Polymer Quenchants– Various types of polymer quenchant have widely
differing properties.– Flexibility of quenching characteristics is possible
through selection of polymer type, concentration, temperature, agitation.
– Success Factors• Hardenability of steel• Section thickness of component• Type of furnace• Quench tank• Required physical properties
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Quenching – Mastering the Process
• Advantages of Polymer Quenchants• Environmental
– Elimination of fire hazard and the need for protection equipment
• Reduced fire suppression equipment required
• Lower fire insurance premiums– Cleaner, safer working environment
• Technical– Flexibility of quenching speed
• Controlled by Concentration, Agitation and Temperature
– Component entry into quenchant is less critical
– Reductions of stresses and distortion
• Production– Reduced cost because diluted polymer
quenchants have lower viscosities• Lower drag-out and replenishment
– Easier cleaning – Reduced temperature rise during
quenching• Polymer quenchant solutions have
almost twice the specific heat capacity of quenching oils
– Reduced distortion• Less straightening• Improvement in fatigue and service life
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Quenching – Mastering the Process
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Quenching – Mastering the Process
• Polyalkylene Glycol (PAG)• PAG Applications
– Immersion quenching of steel components
• Applicable to low, medium and high alloy steels, including carburizing grades
• Martensitic stainless steels– Induction hardening and spray
quenching• Replaces water, soluble oil, or
mineral oil.• Used at 5-15% to eliminate
spotty hardening, control distortion, and provide corrosion protection
• Applicable to all types of components– Fasteners– Bolts– Bearings– Crankshafts– Miscellaneous agricultural
parts– Springs– Steel bars– Steel coils– Forgings– Miscellaneous automotive
parts
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Quenching – Mastering the Process
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Quenching – Mastering the Process
Concentration Temperature
AgitationPolyalkylene Glycol (PAG)
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Quenching – Mastering the Process
• Sodium Polyacrylate (ACR)• Characteristics
– Oil-like quenching characteristics similar to normal speed quenching oils.– Generally used at concentrations of 15-25%– Do not exhibit inverse solubility
• Produce high viscosity, polymer-rich layer around part• Reduces cooling rate during convection phase, reducing distortion
• Applications– Seamless tube - oil industry– Forgings and castings– Thin-section alloy steel crankshafts– High carbon-chromium grinding balls
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Quenching – Mastering the Process
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Quenching – Mastering the Process
TemperatureConcentration
AgitationSodium Polyacrylate (ACR)
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Quenching – Mastering the Process
• Polyethyl Oxazoline (PEO)• Characteristics
– Developed by Houghton International– Oil-like quenching characteristics– Wide application range
• Induction hardening of steel and cast iron• Immersion of high hardenability steel castings and forgings
• Applications– Induction and flame hardening at 5-10% concentration– Generally used at 5-25% concentration for immersion– Typical applications include camshafts, crankshafts and gears in
the automotive industry.– Drill pipe for the oil industry
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Quenching – Mastering the Process
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Quenching – Mastering the Process
Concentration Temperature
Agitation Polyethyl Oxazoline (PEO)
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Quenching – Mastering the Process
• Polyvinyl Pyrrolidone (PVP)
• Oil-like quenching characteristics
• Used at concentrations of 15-25%
• Typical applications include heat treatment of high hardenability materials and alloys.
• Used widely in the steel industry for quenching of bars, rolled sections, and forgings.
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Quenching – Mastering the Process
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Quenching – Mastering the Process
Agitation
Concentration Temperature
Polyvinyl Pyrrolidone (PVP)
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Quenching – Mastering the Process
• Hybrid Polymer Quenchants• Third Generation of Polymer
Quenchants– Applicable to wide variety of
steels and hardenabilities– Low residue, low
concentration and slow quench rates compared to earlier quenchants
– Stable and easy to control– 10-12% equal to medium
speed quenchant– Used for forgings, gears,
cannon barrels, large crankshafts, camshafts
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Quenching Products from Houghton
Cold Quenching OilsHoughto-Quench KHoughto-Quench GHoughto-Quench 3440Houghto-Quench 3430Dasco Quench LPA 15Dasco Quench LBA 15
Polymer (Aqueous) QuenchantsAqua-Quench 140Aqua-Quench 145Aqua-Quench 245Aqua-Quench 251Aqua-Quench 260Aqua-Quench 3699Aqua-Quench C
Email [email protected] [email protected] for more information.
Hot Quenching OilsMar-Temp 355Dasco Quench MPA 60
Below is a sampling of Houghton quenchants. However, you should consult a Houghton expert for the right product for your application.
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