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Low-pressure carburizing and quenching platform

Vacuum Carburizing Furnace

A configured vacuum carburizing platform for repeatable low-pressure carburizing, carbonitriding and heat-treatment cycles, with gas-quench or double-chamber oil-quench cooling selected around your alloy, part geometry and production target.

Vacuum carburizing and high-pressure gas quenching furnace in a production workshop
High-performance thermal processingHorizontal vacuum carburizing with gas-quench cooling
1320 CMaximum operating temperature
150-1000 kgGas-quench loading capacity
6 / 10 / 12 / 16 barGas-quench pressure options
300-2000 PaLow-pressure carburizing range

Process control

Build a precise carbon case with the cooling route your parts require

Low-pressure carburizing gives manufacturers a clean, repeatable route to a hard wear surface and a tough core. With controlled boost and diffusion stages, the process supports uniform case development across complex part features, followed by the quench method best suited to the steel and geometry.

01 / CARBURIZING

Low-pressure process control

Program boost and diffusion stages to establish the surface-carbon level and effective case depth your components require.

02 / COOLING

Quench route matched to steel

Select high-pressure gas cooling or a double-chamber oil-quench configuration against hardenability, distortion target, load mass and throughput.

03 / PRODUCTION

Repeatable programmed cycles

Link vacuum, gas supply, thermal recipe, cooling and interlocks into a controlled sequence that can be reviewed with your acceptance criteria.

Application fit

Made for case-hardened parts where consistency matters

This platform is ideal for gears, shafts, transmission components, fasteners, bearing-related parts and other high-value workpieces made from carburizing, oil-hardening or air-hardening steels. It is especially effective for blind holes, narrow slots and detailed geometries that challenge conventional atmosphere processing.

  • PartsGears, shafts, bearings, driveline components, dies and other workpieces that need a hard wear surface with a tough core.
  • ProcessVacuum carburizing, carbonitriding and quenching, with optional tempering, annealing, brazing, sintering or solution-treatment capability.
  • ControlsRecipe control coordinates temperature, pressure, carburizing medium, cooling, safety interlocks and production data.
Two-chamber vacuum oil-quenching furnace in a manufacturing facility
Production-ready system designTwo-chamber oil-quench configuration

System routes

Choose the quenching route that fits your production goal

Gas quenching provides a clean, controlled cooling path for parts where dimensional stability is important. A double-chamber oil-quench system provides a powerful alternative for steels and loads that benefit from oil quenching. For gas selection criteria, read nitrogen vs argon for vacuum gas quenching.

Vacuum carburizing furnace configured for high-pressure gas quenching
Gas-quench configuration

Vacuum Carburizing & Gas Quenching

High-pressure gas cooling combines clean handling with a controlled cooling profile. Pressure options from 6 to 16 bar support a wide range of hardening duties.

FZSC2 seriesgas cooling
Vacuum carburizing furnace configured for oil quenching
Oil-quench configuration

Double-Chamber Vacuum Carburizing Oil Quenching

A dedicated oil-quench chamber delivers an efficient high-intensity cooling route for demanding steel grades, larger loads and production cycles.

FZSC2 seriestwo chamber

Process engineering

Control the case profile, surface quality and quench result as one process

SYNHTE integrates low-pressure carburizing, programmed enrichment and diffusion, automatic sequence control and the selected quench route into one production platform. The result is a repeatable process built around your alloy, geometry, load pattern and acceptance standard.

15+Years of thermal-processing and vacuum-furnace engineering experience supporting application review, process development and production equipment delivery.
01 / REPEATABILITY

Programmed boost and diffusion

Control temperature, pressure, gas dosing and diffusion time to build the required surface-carbon profile and effective case depth from load to load.

02 / CYCLE TIME

Higher-temperature process capability

Vacuum operation supports elevated carburizing temperatures that can shorten deep-case cycles when the steel grade, grain control and part requirements allow.

03 / METALLURGY

No intergranular oxidation

An oxygen-free low-pressure environment helps prevent intergranular oxidation and supports a clean surface with a consistent carburized-layer interface.

04 / GEOMETRY

Reach complex and recessed features

Acetylene-based low-pressure carburizing supports carbon transfer into narrow slots, blind holes, threaded passages and densely arranged production loads.

05 / QUENCHING

Cooling matched to the steel

High-pressure gas or double-chamber oil quenching is selected around hardenability, section size, distortion target, load mass and throughput.

06 / AUTOMATION

Automatic control and protection

Recipe execution coordinates heating, vacuum, process gas, transfer, cooling and interlocking alarms for consistent operation and equipment protection.

Representative applications

Built for demanding parts, deep features and controlled distortion

From recessed threaded components to heavy gears and precision stainless-steel parts, the process route is configured around material response, case-depth profile, dimensional limits and production loading.

Vacuum-carburized deep-hole threaded steel parts
Deep-hole threaded partsCarbon access into internal surfaces and recessed features.
Large heavy-load gear treated by vacuum carburizing
Large heavy-load gearProject example with a carburized layer of at least 8 mm.
Precision stainless-steel parts after vacuum carburizing
Precision stainless-steel partsProject example with distortion controlled to 0.01 mm or less.
Blind-hole spline parts for vacuum carburizing
Blind-hole spline partsCase development for hard-to-reach spline and bore features.

Furnace range

Choose the chamber, load capacity and quench route

The FZSC2 platform scales from compact precision batches to large industrial loads. Common furnace performance is combined with gas-quench or double-chamber oil-quench configurations selected around the steel, geometry and production target.

1320 CMaximum temperature
+/- 5 CTemperature uniformity
≤4 x 10-3 PaUltimate-vacuum option
<0.67 Pa/hPressure rising rate
Auto / ManualControl modes
Clean high-pressure cooling

Gas-Quench Route

For clean handling, programmable cooling and distortion-sensitive production.

  • FZSC2-60 to FZSC2-220150-1000 kg loads
  • 6 / 10 / 12 / 16 barGas-pressure options
High-intensity cooling

Double-Chamber Oil-Quench Route

For alloys, sections and larger loads that benefit from oil-quench severity.

  • FZSC2-60 to FZSC2-300150-5000 kg loads
  • Separate quench chamberIntegrated transfer and oil cooling
FZSC2-60Gas or oil quench
150 kg

Loading capacity

Chamber600 x 400 x 400 mm
Heating60 kW
FZSC2-80Gas or oil quench
300 kg

Loading capacity

Chamber750 x 500 x 500 mm
Heating80 kW
FZSC2-120Gas or oil quench
500 kg

Loading capacity

Chamber900 x 600 x 600 mm
Heating120 kW
FZSC2-220Gas or oil quench
1000 kg

Loading capacity

Chamber1200 x 800 x 800 mm
Heating220 kW
FZSC2-300Oil-quench route
5000 kg

Loading capacity

Chamber1500 x 1500 x 800 mm
Heating300 kW

Process performance

Higher-temperature LPC can shorten the route to the required case depth

Vacuum carburizing can operate at elevated process temperatures when the steel and acceptance requirements permit. Faster carbon diffusion can reduce carburizing time, with the final cycle engineered around material, target profile, load density and grain-control strategy.

Case depth 0.5-0.8 mm

Representative carburizing time

Vacuum 1000 C
1 h
Vacuum 920 C
1.5 h
Atmos. 920 C
2 h

Case depth 0.8-1.2 mm

Representative carburizing time

Vacuum 1000 C
1.5 h
Vacuum 920 C
3 h
Atmos. 920 C
5 h

Case depth 1.2-1.5 mm

Representative carburizing time

Vacuum 1000 C
2 h
Vacuum 920 C
5 h
Atmos. 920 C
8 h
2 h vs 8 h

In the representative 1.2-1.5 mm case-depth comparison, vacuum carburizing at 1000 C reaches the target in about one quarter of the atmospheric 920 C carburizing time.

Why low-pressure carburizing

A cleaner, more controlled route to case hardening

Low-pressure carburizing uses an oxygen-free process atmosphere and programmed enrichment-diffusion stages to support uniform case development, repeatable cycles and clean treatment of high-value components.

Process factor
Atmospheric carburizing
Vacuum carburizing
Carburizing temperature
860-920 C
860-1050 C
Carburizing pressure
Above 1 bar
300-2000 Pa
Case-layer uniformity
Typically wider variation
Tightly controlled boost-diffusion profile
Intergranular oxidation
Can occur in oxygen-bearing atmospheres
Avoided in the oxygen-free LPC environment
Carburizing medium
Methanol, kerosene or propane
Targeted acetylene dosing
Complex features
Carbon potential can vary in recessed areas
Effective access to blind holes, slots and dense loads
Surface condition
Dark surface and post-process cleaning
Clean, bright treated surface
Production flexibility
Atmosphere conditioning and continuous operation
Programmable start-stop production
Process-gas consumption
Continuous atmosphere supply
Low-volume, recipe-controlled dosing
Workshop environment
Lampblack, flame curtain, heat and exhaust
Sealed, clean and lower-emission processing

Vacuum carburizing knowledge

Answers to the process questions that shape part quality

Understand how carbon profiles are built, why quench selection matters and which variables influence case depth, distortion and surface condition.

Process basicsWhat happens during low-pressure carburizing?

The workload is heated under vacuum, then alternating enrichment and diffusion stages introduce carbon at the surface and develop the required carbon gradient. The parts are subsequently gas or oil quenched to create a hard case while retaining a tougher core.

Case engineeringHow is effective case depth controlled and verified?

Case depth is engineered through the steel grade, carburizing temperature, surface-carbon target, boost and diffusion timing, load arrangement and quench response. Production verification normally uses a hardness traverse and, where required, metallographic examination against the specified acceptance method.

Complex geometryWhy is LPC effective for blind holes and densely loaded parts?

Acetylene-based low-pressure carburizing provides strong carbon transfer and good access to recessed geometries. Proper gas distribution, pulse timing, spacing and fixturing remain important for uniform treatment of blind holes, narrow slots and dense production loads.

Quench selectionHow should gas quenching and oil quenching be selected?

High-pressure gas quenching offers clean, adjustable cooling and is often preferred where dimensional control is important. Oil quenching provides higher cooling severity for steels, section sizes or load masses that need it. The final route is selected from hardenability, geometry, hardness target, distortion limit and throughput.

Dimensional controlCan vacuum carburizing reduce distortion?

Vacuum heating, uniform loading and controllable gas-quench pressure can improve repeatability and reduce distortion compared with less controlled routes. Final movement still depends on steel condition, prior machining stress, geometry, fixturing, temperature uniformity and cooling intensity.

Surface qualityWhy does LPC avoid intergranular oxidation?

Low-pressure carburizing is performed without the oxygen-bearing atmosphere used by conventional carburizing, so intergranular oxidation is avoided during carbon enrichment. This supports a clean surface and a regular interface between the carburized layer and the base material.

Cycle developmentDoes a higher carburizing temperature always improve the process?

Higher temperature accelerates carbon diffusion and can shorten deep-case cycles, but it must be compatible with the steel, grain-growth control, dimensional requirements and acceptance standard. The optimum recipe balances cycle time with metallurgical and dimensional performance.

Furnace specificationWhat information is useful when specifying a furnace?

The most useful starting data are the steel grade, part drawing, target effective case depth and hardness, allowable distortion, batch envelope and mass, annual throughput, preferred quench route and applicable inspection standard.

Built around your process

Ready to improve the consistency of your case-hardening process?

Tell us about your parts, materials, case-depth target, batch load and production capacity. SYNHTE will recommend a vacuum carburizing furnace built for your application.

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