High pressure gas quenching (HPGQ) offers advantages like reduced hardening distortion and adjustable quenching intensity through gas pressure and velocity. This clean and non-toxic process integrates well into manufacturing lines, producing reproducible and high-quality results without the need for washing. Key parameters influencing HPGQ include gas type, pressure, velocity, and chamber design, which collectively impact the material's microstructure, hardness, and overall distortion.

1. High Pressure Gas Quench
High Pressure
Gas Quenching
Advantages of Gas Quenching

2. High Pressure Gas Quench
 Reduction of hardening distortion and/or variation of distortion
 Quenching intensity adjustable by of gas pressure and
gas velocity
 Process flexibility
 Clean, non-toxic working conditions
 Integration into manufacturing lines
 Reproducible quenching result
 Clean and dry parts, no washing
 Simple process control
Advantages of Gas Quenching

3. High Pressure Gas Quench
High Pressure Gas Quench
Quench Media vs. Heat Transfer Coefficient α
Data taken from:
George E. Totten, PhD, FASM
Portland State University
Department of Mechanical and Materials Engineering
Heat Transfer rate, W M-2
K-1

4. High Pressure Gas Quench
0
100
200
300
400
500
600
700
800
900
0 10 20 30 40 50 60
10 bar N2
10 bar He
20 bar He
40 bar He
Fast quenching oil
Bellini FS (70ƒC)
Hot quenching oil
Quench Behavior – 3D Loads
Oil vs. HPGQ
Time
Temperature

5. High Pressure Gas Quench
Bubble Boiling
Film Boiling
Convection
t = 10 s
750°C
700°C
700°C
600°C
500°C
400°C
300°C
200°C
Temperature distribution
t = 10 s
Heat transfer coefficient α
5000 10000 15000 20000
Öl
oil Wasser
water
[W/m K]
2
ref.: Stick, Tensi, HTM 50, 1995
Heat Transfer & Temperature Distribution
Immersion Quenching

6. High Pressure Gas Quench
Heat transfer coefficient α
1000 2000 3000 4000 [W/m K]
2
Temperature distribution
750°C
650°C
550°C
450°C
350°C
250°C
Gas direction
Only convection
Heat Transfer & Temperature Distribution
High Pressure Gas Quenching

7. High Pressure Gas Quench
- Gas (N2, He, H2)
- Gas pressure
- Gas velocity
HPGQ Parameters
Quenching Gas

8. High Pressure Gas Quench
Chemical symbol
Density at 15 o
C
and 1 bar
Density relative to air
Molar mass
(kg / kmol)
Specific heat capacity
Cp (kJ / kg K)
Dynamic viscosity
η (N s / m 2
)
Thermal conductivity
λ (W / m K)
Argon Nitrogen Helium Hydrogen
Ar
1,6687
1,3797
39,948
0,5024
177x10- 4
22,6x10- 6
N 2
1,170
0,967
28,0
1,041
259x10- 4
17,74x10- 6
He
0,167
0,138
4,0026
5,1931
1500x10- 4
19,68x10- 6
H 2
0,0841
0,0695
2,0158
14,3
1869x10- 4
8,92x10- 6
(at 25o
C und 1 bar)
Quench Gas Properties

9. High Pressure Gas Quench
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16 18 20
N2
He
H2
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16 18 20
Relative Motorpower for
cooling gas fans
Relative
Heat Transfer Coefficient
Gas pressure (bar) Gas pressure (bar)
N2
He
H2
HPGQ Parameters
Influencing Factors

10. High Pressure Gas Quench
Helium with Recycling,
Consumption per Quench 0.3 m³ = 10.6 cft
Nitrogen without Recycling,
Consumption per Quench 55 m³ = 1942 cft
HPGQ Cost
Helium vs. Nitrogen

11. High Pressure Gas Quench
- Gas Paths
- Gas Fan(s)
- Heat Exchanger(s)
- Loading
- Process flow
- Kind of Flow
- Gas ( N2, He, H2 )
- Gas pressure
- Gas velocity
HPGQ Parameters
Quenching Chamber

12. High Pressure Gas Quench
HPGQ Parameters
Quenching Chamber
Multi Chamber Furnace
(Cold Chamber)
Backfill time to
final pressure >> 10 sec
Backfill time to
final pressure << 10 sec
Gas flows
through the
charge and inpart
around the charge
Hot wall
and hot
graphite elements
Gas must
flow through
the charge
Cold Wall
Single Chamber Furnace
(Hot Chamber)

13. High Pressure Gas Quench
Reversing Gas Flow Increased Quenching Uniformity
Modular Design Flexible and Expandable
Compact Chamber Design Short Gas Recycling Cycles
HPGQ Quenching Chamber

14. High Pressure Gas Quench
ModulTherm – Options
Reverse Quenching
Top to bottom gas flow Reversing gas flow

15. High Pressure Gas Quench
ModulTherm
Quench Flow Advantage
• Use of 2 radial fans
• homogeneous gas inlet flow above the
load by using a guide system in the gas
duct
• 100% load density
• no wake behind the hub
• no swirling of the gas flow
• high gas flow uniformity
⇒ homogeneous hardness
distribution ⇒ lower distortion
• 2 axial fans
• In homogeneous gas inlet flow above the load
• wake behind the hub:
• shortfall of hardness at parts positioned in the
wake
• possible spreading of hardness
• 100% load density not achievable (loading map)
Wärme-
tauscher
Wake behind the hub
ALD-Holcroft Quenching Concept Concept using Axial Fans

16. High Pressure Gas Quench
Cooling curves in the tooth root of Truck- Gear Wheels (GW)
0
100
200
300
400
500
600
700
800
900
-50 0 50 100 150 200 250
Time /sec.
Temp./°C
GW bottom, no rev.
GW, top, no rev.
gas-temp. bottom, no rev.
GW bottom, with rev.
GW, top, with rev.
gas-temp. bottom, with rev.
HPGQ Quenching Chamber
Reverse Gas Flow Quenching
Quench behavior in the tooth root of heavy truck gears

17. High Pressure Gas Quench
300
320
340
360
380
400
420
440
460
No reversing With reversing
CorehardnessatMid-tooth/HV30
Bottom min
Bottom average
Bottom max
Top min
Top average
Top max
Gas flow Gas flow
300
310
320
330
340
350
360
370
380
390
400
No reversing With reversing
CorehardnessatToothroot/HV30
Bottom min
Bottom average
Bottom max
Top min
Top average
Top max
Gas flow Gas flow
300
310
320
330
340
350
360
370
380
390
400
No reversing With reversing
CorehardnessatBulk/HV30
Bottom min
Bottom average
Bottom max
Top min
Top average
Top max
Gas flow Gas flow
BulkBulk
ToothTooth
rootroot
Mid-Mid-
toothtooth
ModulTherm – Options
Reverse Quenching
Core hardness with and without reversing the gas flow
Modified SAE 5120

18. High Pressure Gas Quench
HPGQ Quenching Chamber
Cold Chamber, 20 Bar with Reverse Gas Flow Quenching

19. High Pressure Gas Quench
- Material
- Chem. Composition
- Delivery Condition
- Part Geometry
- Dimension, Form
- Manufacturing
- Load Weight
- Gas paths
- Gas Fan(s)
- Heat Exchanger(s)
- Loading
- Process flow
- Kind of Flow
- Gas (N2, He, H2)
- Gas pressure
- Gas velocity
HPGQ Parameters
Materials

20. High Pressure Gas Quench
Nitrogen Helium
GasQuenchingPressure
10bar20bar
- Hot-/Cold working Steels
X155CrMo12 1(D2)
X38CrMoV5 1(H13)
- High Speed Steels
(1.3343)
- Ni-Alloyed Case Hardening Steels
(18CrNi8, 17CrNiMo6)
- Ball Bearing Steels (Small Sizes)
100Cr6 (SAE 52100) 100CrMn6
- Heat Treatable Steels
42CrMo4 HH (4140 HH)
- Low Alloyed Case Hardening Steels
(16MnCr5, 20MoCr4, SAE 8620)
- Ball Bearing Steels (Medium Sizes)
100 Cr6 (SAE 52100)
- Al-, Ti-Alloys
ALD-Patented
Material, Part Dimension and Hardness Specif.
determine Quenching Process Parameters
HPGQ Process Matrix

21. High Pressure Gas Quench
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35 40 45
Hardness(HRC)
Jominy Distance (mm)
20NiCrMo2 (SAE 8620)
20MoCr4 (SAE 4118)
16MnCr5 (SAE 5115)
20MnCr5 (SAE 5120)
20NiCrMoS6-4
18CrNiMo7-6
20
bar
He
20
bar
N2
Jominy Curves of steel grades with
high hardenability acc. to EN 10084
Core Hardness Influences
Case Hardened Steel

22. High Pressure Gas Quench
∆ Ovality of Outer Diameter (mm)
Oil A : Houghton
Quench A
Oil B : Bellini FN
10 bar He
20 bar He
Cold Chamber
0
0.01
0.02
0.03
0.04
0.05
0.06
10 bar
He
20 bar
He
Oil A Oil B
Average and
Standard Deviation
n=12
7
12
6
Material: SAE 52100
(D=70 mm, H=15 mm, S=5 mm)
Dimensional Changes
Bearing Rings

23. High Pressure Gas Quench
Process Comparison
Drive Shafts
Shaft Length up to 750 mm (29.5 inches)
Material 17CrNiMo6 (similar SAE 9310)
Past H. T. Process
Gas Carburizing
Quench in Salt Bath
Distortion over Length of Shaft
Average 3 mm (0.12 inches)
Straightening Scrap 20 %
New H. T. Process
Vacuum Carburizing with
High Pressure Gas Quench with 8 bar
Helium
No Washing – Clean and Dry Parts
Distortion over Length of Shaft Average
1.0 mm (0.039 inches)
Less Straightening Work
No Scrap
Significant Characteristics
Product Quality

24. High Pressure Gas Quench
500 kg gross Load of Pinions, 20 bar Helium, SAE 8620
High Pressure Gas Quenching
Product Quality

25. High Pressure Gas Quench
0
2
4
6
8
10
12
14
16
18
20
1 2 3 4 5 6
Roundness (1/1000 inch)
NumberofParts
Gas Carburizing
with Oil Quench
Vacuum Carburizing with
High Pressure Gas Quench
Material: SAE 8620
Part Weight: 1.5 kg (3.3 lbs)
Drive Shafts
Significant Characteristics
Distortion Comparison

26. High Pressure Gas Quench
0
10
20
30
40
50
60
µ
m
left flank
right flank
Ölabschreckung
Gasabschreckung dyna-
misch (20 sec.- Ventila-
torstopp)
Gasabschreckung
ohne Dynamik
spread of helix slope
deviation after heat
treatment
f Hβ,max - f Hβ,min
0
100
200
300
400
500
600
700
800
900
30 60 90 120 150
Zeit / s
Temp./°C
dynamisch
konventionell
Ventilatorstopp Wiederstarten des
Ventilators
Material: SAE 5115
(16MnCr5)
Quality Control – Gas Quenching
Dynamic Quenching

27. High Pressure Gas Quench
• High Pressure Gas Quenching can significantly reduce distortion
and/or variation of distortion
• Microstructure, Hardness and Distortion are strongly
influenced by
- Part
- Quenching Parameters
- Cold Chamber Design
• 20 bar Helium Quenching Technology is capable of successfully
hardening low alloyed case hardening steels if material hardenability
can be controlled
• Alloy modification offers the chance to reduce gas pressure/velocity
thereby reducing distortion and/or investment costs
Summary