Heat Treating 420 Stainless Steel

Heat treating 420 stainless steel transforms this martensitic alloy into a high-performance material optimized for extreme wear resistance, edge retention, and load-bearing capacity. Through controlled quenching and tempering, 420 steel achieves Rockwell hardness up to HRC 55 while retaining critical corrosion tolerance in mild environments. Ideal for cutlery, surgical tools, and industrial blades, our heat treatment services comply with AMS 5508 and ASTM A276, ensuring metallurgical consistency and traceability.

Key Benefits of Heat Treatment

Maximized Hardness & Durability

Post-quench hardness: HRC 50–55 (vs. annealed HRC ≤25).

Enhanced tensile strength (1.550 MPa) for applications like valve seats and bearing races.

Tailored Toughness

Adjust tempering temperatures (200–600°C) to balance hardness (HRC 35–55) with impact resistance.

Stress Relief & Stability

Eliminate machining-induced stresses to prevent distortion in precision components.

Corrosion Optimization

Post-treatment passivation (per ASTM A967) boosts chromium oxide layer formation.

Heat Treatment Process Flow

Step	Parameters	Equipment Used
1. Austenitizing	980–1.050°C, 30–60 mins per 25 mm thickness	Electric furnace (argon atmosphere)
2. Quenching	Rapid cooling in oil/air (20–40°C/s)	High-pressure oil quench tanks
3. Tempering	200–600°C, 1–4 hours (adjust for application)	Convection tempering ovens
4. Surface Finishing	Electropolishing, TiN coating (optional)	CNC grinding & PVD coating systems

Technical Specifications

Post-Treatment Properties

Property	As-Quenched	Tempered (300°C)	Tempered (550°C)
Hardness (HRC)	50–55	48–52	35–40
Yield Strength (MPa)	1.550	1.450	1.100
Impact Toughness (J)	12	18	25
Corrosion Resistance*	Moderate	Moderate	Improved
**(ASTM G48 testing in 6% FeCl3. 22°C)

Critical Applications

Medical: Sterilizable scalpel blades, biopsy forceps, and dental burrs.

Industrial: Textile cutter bars, food processing blades, and hydraulic pump shafts.

Consumer: Luxury knives, watch gears, and firearm components requiring cyclic stress tolerance.

Automotive: Fuel injector pins, turbocharger bushings, and clutch springs.

Quality Assurance & Certifications

Metallurgical Testing:

100% microstructure inspection (ASTM E3) to verify martensitic transformation.

Hardness mapping (HRC ±2 tolerance across batch).

Certifications:

ISO 13485 (medical devices), NADCAP AC7101 (aerospace), IATF 16949 (automotive).

Traceability:

Digital heat lot tracking with QR codes for full process history (quench rates, temper curves).

FAQs

Q1: What is the ideal quench medium for thin-section 420 steel?

A1: For sections <3 mm, forced-air quenching minimizes distortion; thicker sections require fast oil (e.g., Parks 50).

Q2: Can 420 steel be re-hardened after welding?

A2: Yes-re-austenitize at 1.020°C, hold for 15 mins/mm, then quench. Use AWS ER420 filler to match composition.

Q3: How does tempering temperature affect corrosion resistance?

A3: Tempering above 500°C precipitates chromium carbides, reducing corrosion resistance. Opt for 300–400°C for balanced properties.

Q4: Maximum service temperature for heat-treated 420 steel?

A4: 450°C (842°F) continuous; avoid prolonged exposure above 300°C to prevent softening.

Q5: How to mitigate hydrogen embrittlement post-treatment?

A5: Bake at 190–220°C for 8–24 hours within 4 hours of quenching to desorb trapped hydrogen.

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