Application of Vacuum Gas Quenching Furnace in AISI 420 Stainless Steel
AISI 420/1.4021 belongs to martensitic stainless steel, containing 12%-14% chromium. Its core feature is the balance between hardness and basic corrosion resistance. After heat treatment, its hardness can reach HRC 50-55, allowing it to be ground into sharp and durable cutting edges. At the same time, a chromium oxide protective film can form on its surface, resisting corrosion from blood, body fluids and disinfectants. It is also easy to process into various medical device shapes such as surgical scalpels and tissue scissors, and can be polished to a mirror finish to reduce bacterial adhesion, making it a common material for conventional surgical tools. However, it is not completely rust-proof and needs to be cleaned and stored in a dry place in a timely manner. Its performance also depends on standardized heat treatment processes. Compared with the upgraded AISI 440C, it has slightly lower hardness and corrosion resistance, but lower cost and easier processing. It also avoids the problem of poor corrosion resistance of high-speed steel, accurately meeting the needs of conventional medical scenarios.
To produce AISI 420 stainless steel products with excellent performance, vacuum heat treatment is essential. The specific vacuum heat treatment process is as follows:
Vacuum Gas Quenching Stage
1.Preheating：Raise the temperature to 500°C at a rate of 5–15°C/min, and hold for 30 minutes.
2.Continue heating to 800°C, and hold for another 30 minutes.
3.Austenitizing HeatingHeat to 1050°C at the same heating rate as preheating, and hold for 30 minutes.
4.Gas Quenching Cooling：Fill the furnace with high-purity argon, controlling the gas quenching pressure at 0.2 MPa, and cool the workpiece rapidly through forced convection.
5.When the furnace temperature drops to 250°C, hold for 60 minutes for isothermal treatment to reduce thermal stress and deformation risk.
6.Continue cooling until the temperature falls below 100°C to complete the gas quenching stage.
Vacuum Tempering Stage
1.Heating for Tempering：Immediately transfer the workpiece to a vacuum tempering furnace after gas quenching. The temperature of the workpiece when entering the furnace shall not exceed 200°C.
2.Raise the temperature to 200°C at a rate of 5–10°C/min, and hold for 90–120 minutes.
3.Cooling and Furnace Removal：After the tempering holding period, cool the workpiece naturally in the vacuum furnace until the temperature drops below 100°C.
4.Slowly fill the furnace with high-purity nitrogen to atmospheric pressure to prevent workpiece deformation caused by sudden pressure changes.Finally, unload the workpiece.
Technical Parameters of Vacuum Gas Quenching Furnace for AISI 420 Stainless Steel (Quenching & Tempering)：
| Furnace type | Horizontal type,single chamber, internal recycle |
| Loading method | Front loading |
| Effective working zone | 400×400×600(W×H×L mm) |
| Max. loading weight | 200kg (including jig) |
| Power supply | 3Phase 380V(±5%) ;50Hz |
| Total power | 190kw |
| Heating power | 110kw |
| Cooling fan motor power | 160kw |
| Max.design temperature | 1400℃ |
| Working temperature | 1350℃ |
| Temperature uniformity(vacuum and empty furnace, 500-1000℃( | 9 points temp testing ( ±5℃) (standard AMS 2750F) |
| Temperature control accuracy | S-type thermocouple ±1℃ |
| Quantity of heating zone | 1-zone temperature control |
| Heating element | High-purity graphite |
| Heating rate(the room temperature of the empty furnace rises to 1200℃) | ≤ 60 min |
| Ultimate vacuum(empty furnace, cold state, after drying and degassing) | 6.7×10–3 Pa |
| Working vacuum (empty furnace, room temperature) | 1 x 10–2 Pa |
| Evacuation rate(cold empty furnace condition) | ≤ 30 min(cold and empty condition to 5 Pa) |
| Pressure rise rate (empty furnace, cold state) | ≤ 0.67 Pa/h |
| Cooling method | Air cooling/Natural cooling |
| Cooling gas | Nitrogen or Argon (purity: 99.99% or 99.999%) |
| Cooling rate ( empty furnace, 1200°C~500°C ) | ≤ 6 min |
| Max charging pressure(absolute pressure) | ≤ 15bar (adjustable) |
| Temperature control method | Intelligent programmable temperature controller for automatic temperature control |
| Control mode | PLC automatic / manual control interlock protection |
| Furnace shell color | Customized |
If you have any needs or inquiries, please feel free to contact us at furnace@vacfurnace.com. We look forward to serving you
