Vendor handoff: what goes on the print to the heat treater, nitride house, and polisher

A complete heat-treat callout for an H13 forge die has eleven elements.

Substrate: AISI H13 per ASTM A681, electroslag remelted (ESR), supplied annealed at ≤ 235 HB, NADCA #207 Premium Grade or equivalent. Mill certificate required with shipment.

Process: Vacuum harden and double temper per AMS 2759/3, or per NADCA #207 acceptance criteria where more restrictive.

Pre-heat: Two-stage preheat, 650°C and 850°C, equalize at each stage; thick sections (≥ 150 mm) require a third stage at 1020°C.

Austenitize: 1020°C ± 10°C, soak 30 minutes per 25 mm of cross-section once at temperature. Time at temperature logged on the cycle trace.

Quench: High-pressure gas quench, nitrogen, 5 bar minimum pressure. Cool from austenitize temperature through 540°C in ≤ 25 minutes. Quench rate trace required.

Snap temper: 150°C for 1 hour minimum after quench and before first temper.

Temper sequence: Three tempers, 2 hours minimum at temperature each, air cool between tempers. First and second tempers above the secondary hardening peak, third temper 10-20°C above the second. Final temper temperature selected to land in the hardness band below.

Hardness: 48-50 HRC core, measured per ASTM E18, minimum three readings averaged, locations called out on drawing zone B3. Witness coupon hardness reading included on certificate.

Retained austenite: ≤ 5 percent by X-ray diffraction or quantitative metallography on the witness coupon.

Distortion: Flatness deviation ≤ 0.05 mm across 500 mm on datum A post heat treat. Linear distortion on critical dimensions ≤ 0.003 inch per inch.

Certification: Furnace cycle trace (time, temperature, pressure) and witness coupon results shipped with the parts. NADCA #207 Acceptance Class B microstructure confirmation by photomicrograph of the coupon at 500x.

The substrate line carries the grade, the melting practice, the starting hardness, and the acceptance grade. ESR matters when the failure mode is thermal fatigue rather than wear. Calling it out by name on the print stops a substitution to a VAR or air-melt block. The austenitize and quench parameters define what microstructure the cycle produces. The quench rate through 540°C is the single most important number, because that is where the carbide precipitation nose sits on the time-temperature curve. The three-temper sequence is mandatory on 5 percent chromium steels because two tempers do not fully transform retained austenite, and retained austenite transforms slowly in service and grows the die dimensionally over months. The retained austenite limit on the witness coupon is the only way to verify the temper actually finished the job. The distortion line ties the spec to a datum the print actually carries. An open "minimize distortion" call commits the vendor to nothing.