Deep Cryogenic Treatment - Detailed Technical Questions and Explanations 

Xinfengli Cryogenic Treatment - Deep Cryogenic Treatment

Cryogenic Treatment
Cryogenic treatment refers to the process of cooling quenched steel to below room temperature. After quenching, steel components are rapidly cooled to a sub-zero temperature, converting residual austenite into martensite to enhance hardness and dimensional stability. This process is an extension of quenching, also termed low-temperature treatment or deep cryogenic treatment. Terms like "ice treatment" and "subzero treatment" are imprecise and should be discontinued. Even when treated at -190°C, a small fraction (typically a few percent) of austenite remains. Thus, temperatures of -100°C to -80°C generally suffice, with treatment times of 30–90 minutes.

Cryogenic treatment effectively prevents cracking. When quenched steel is rapidly cooled to room temperature and left at ambient conditions, residual austenite slowly transforms into martensite, increasing internal stresses and potentially causing cracks. Key process parameters include:

Room-temperature dwell time after quenching
Cryogenic treatment temperature
Deep-cold dwell time
The allowable room-temperature dwell time depends on the steel's Mc point (martensite finish temperature). For steels with Mc points above room temperature, prolonged exposure stabilizes residual austenite, reducing treatment efficacy. Steels are categorized based on stabilization sensitivity:

Non-sensitive materials (e.g., 18CrNiW, 12Cr2Ni4WA): Allow up to 24 hours at room temperature.
Moderately sensitive materials (e.g., W18Cr4V, CrMn): Restrict dwell time to 2–3 hours.
Highly sensitive materials (e.g., T8, T9): Require immediate cryogenic treatment post-quenching.
Treatment efficacy depends on temperature and room-temperature dwell time. Lower temperatures and shorter dwell times yield better results, with a maximum allowable dwell time of 30 minutes post-quenching.

Cryogenic temperatures are selected based on the steel's Mf point (martensite finish). For tool steels, -60°C to -80°C is typical, while high-alloy steels require -120°C to -180°C. Treatment duration ensures full penetration, typically 0.5–1 hour, depending on geometry.

Critical Notes:

Complex or large components should be cooled gradually to avoid thermal stress and cracking.
Post-treatment tempering or aging (4–10 hours) is essential to stabilize the martensitic structure and further transform residual austenite.
Quenched components with retained austenite exhibit reduced hardness and dimensional instability. Deep cryogenic treatment promotes austenite-to-martensite conversion but risks subzero cracking if performed immediately post-quenching or on decarburized layers.

Best Practices:

Pre-treat with mild tempering (100–130°C) to stabilize austenite and reduce quenching stresses before cryogenic treatment, minimizing crack risk (though ~5% stabilized austenite remains to absorb impact energy).
For complex geometries, 100°C water quenching post-treatment is mandatory.
Rapid reheating from cryogenic temperatures (e.g., immersing in water) offsets residual stresses, preventing cracks.
Xinfengli Deep Cryogenic Treatment Technology
Xinfengli’s deep cryogenic treatment (DCT) uses liquid nitrogen (-196°C) to cool quenched metals below room temperature, further converting residual austenite into martensite to enhance hardness, toughness, and dimensional stability. This process doubles tool service life and improves wear resistance.

Technical Specifications:

Operating Range: +200°C to -196°C (adjustable)
Minimum Chamber Temperature: ≤ -196°C
Cooling Rate: ≥50°C/min
Temperature Control Accuracy: ±1°C (heating, cooling, holding)
Temperature Uniformity: ±1°C
Advantages:

Bulk Material Modification: Improves core properties, not just surface hardness.
Dimensional Stability: Reduces quenching stresses and stabilizes dimensions.
Process Simplicity: Suitable for all shapes/sizes; eco-friendly and energy-efficient.
Applications:
DCT is widely adopted in cutting tools, gauges, molds, precision components (e.g., fuel injectors, turbine shafts, gears), and non-ferrous materials (aluminum, copper alloys). Industries like aerospace, automotive, and defense leverage DCT for superior performance and longevity.

This technology has gained global recognition, with rapid adoption in the U.S., Russia, and Japan for enhancing materials across sectors.