Vacuum Carburizing

Low Pressure Carburizing or LPC

Fast Carbon Transfer

No Surface Oxidation

Good Case Depth Uniformity

Integration into Manufacturing

Little Consumption of Carburizing Gas

No Formation of Furnace Atmosphere

High Carburizing Temperatures possible

Advantages of Vacuum Carburizing

Material Temperature ECD Treatment Treatment (0.35 % C) time* time* vacuum gas carburize carburize

16 MnCr 5 930°C 0.6 mm 2.00 hours 2.75 hours

~ SAE 5115 (1700°F)

17 CrNiMo 6 960°C 1.6 mm 7.50 hours 9.50 hours

~ SAE 9310 (1760°F)

* treatment time = carburizing + diffusion + lowering to quenching temperature

Cycle Time Comparison LPC vs. Batch Atmosphere

Time

Convective Heating

Carburizing Diffusioning

Quenching

1

10-1

10-3

10-5

20

940

850

20

Pressure (bar)

Temperature (°C)

Time

LPC Cycle

Process - LPC Exhaust Contents

100%

5 %

90 %*) Approx. 5% other

Hydrocarbons

part of it

< 0.03 Vol.-% Benzene

10 %

45 %

40%

10 %*)

End of

pause

Average over

boost cycle

End of

boost cycle

N2

N2

HC

H2 No thermal off gas

incinerator necessary 5 %

N2

C2Hx

*) depends on Gas ballast flow rate

H2

24/7, 50 weeks per year, 6 hour cycles, 2250 net pounds per load, 3050 gross pounds per load, 4,100,625 pounds per year.

Electrically heated atmosphere furnace process gas figures:

2,810,813 ft3 of CH4 = 2,810,813 ft3 of CO2 x 0.117 lbs per ft3 = 328,865 lbs CO2 or

149.5 Metric tons of CO2 per year per furnace

Vacuum Carburizing (ModulTherm LPC):

95,886 ft3 C2H2 x .05 C2H2 up the stack <5% C2H2 in Exhaust 4794.3 ft3 C2H2 will oxidize to 9,588.6 ft3 CO2 = 1121.9 lbs CO2 or

0.51 metric tons CO2 per year

Naturally, all of these calculations are theoretical and assume properly adjusted systems. The LPC system assumes C2H2 disassociation

>95%. >75% C absorbed by the steel. A known stack discharge of 0-5% C2H2 during boost. The majority of carbon not absorbed by the

load is recovered as particulates in the pump oil filtering system.

Process – Greenhouse Gas Exhaust Volume LPC vs. Batch Atmosphere

A very

“green”

process

Bright and shiny parts after heat treatment

due to

Clean, vacuum process with inert gases.

Highest repeatability / reproducibility

due to

precision of the process.

(ECD uniformity of +/- 0.05 mm or 0.002”

@ CD 0.5 – 0.9 mm or 0.02 – 0.035”)

Significant Characteristics Product Quality

Clean Parts

Significant Characteristics Product Quality

Higher fatigue strength and wear resistance

due to

NO intergranular oxidation at the surface,

higher consistency of case depth between tooth root

and tooth flank,

ECD @ tooth root/tooth flank*

VC + Gas Quench: 80 – 90 %

VC + Oil Quench: 70 – 75 %

Gas Carb. + Oil Quench: < 70 %

*depending on the part size.

greater depth of hardness > 58 HRC in tooth root and

tooth flank (SAE 8620).

Significant Characteristics Product Quality

• No surface or subsurface (intergranular) oxidation (No IGO)

– Atmosphere carburizing typically produces both surface oxidation (dealloying)

and an intergranular oxidation (IGO) layer of 7.5 – 12.5 micron.

Gas-Carburized Vacuum-Carburized

Significant Characteristics Product Quality

Significant Characteristics Product Quality

• Case Depth Consistency

• Carbon Profile Uniformity

Atmosphere Carburize (Oil Quench):

Pitch Line & Root Comparison

180

220

240

260

280

.010

300

200

.020 .030 .040 .050 .060 .070 .080.000

58 HRC

AC @ pitch line

AC @ root50 HRC

50 HRC

58 HRC

Depth (inches)

Hard

nes

s (m

icro

ns)

Root case depth is

significantly lower than Pitch-line case depth

Significant Characteristics Product Quality

Vacuum Carburize (HPGQ):

Pitch Line & Root Comparison

180

220

240

260

280

.010

300

200

.020 .030 .040 .050 .060 .070 .080.000

58 HRC

VC @ pitch lineVC @ root

50 HRC

50 HRC

58 HRC

Depth (inches)

Hard

nes

s (m

icro

ns)

Root case depth is in

the same level as Pitch-line case depth

Significant Characteristics Product Quality

Less distortion and Less variation

due to

Optimal controllability of the quenching process by

• Single-phase “uniform” heat transfer during quenching

• Controllable quenching intensity:

- Free choice of gas pressure (from 1 to 20 bar).

- Free choice of gas speed (2 speeds of the quenching fan).

- Using different gases (Helium, Nitrogen).

(Optimized quenching achieves desirable hardness & minimal distortion)

Significant Characteristics Product Quality

Operational cost advantages:

Environmentally and workplace friendly.

Flexible in operation

Potential to eliminate post HT press quenching or straightening

Significant Characteristics Operation

For more information contact us at:

ALD Vacuum Systems, Inc.

50477 Pontiac Trail

Wixom MI 48393

(248) 956-7610

www.ALDVac.com