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Wrap-up

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Lesson 02·Substrate selection

Steel selection by application — hot-work, warm-work, and the special cases

Pick H13, H11, premium hot-work grades (DIEVAR, QRO 90 Supreme, W360 ISOBLOC), PM hot-form grades (CPM 1V), or Nitralloy 135M for the right job. Read a Uddeholm or Bohler datasheet without getting sold.

10 min readLesson 2 of 13

Tying it together

What this means on the shop floor

Hot-trim die for steel forgings, edge-wear failure: standard H13 at 50-52 HRC, or step up to CPM 1V at 58-60 HRC, with plasma nitride and AlTiN PVD on the cutting edge. Premium H13 does not address edge wear and is the wrong line item to upgrade.

Hot-forge cavity for steel parts, heat-check failure on standard H13: move to DIEVAR or W302 SUPERIOR at the same 46-48 HRC core. The cleanliness and toughness shift attacks the failure mode directly. PVD adds nothing at the die-face temperatures involved.

Aluminum hot-forge die, adhesive wear and pickup: standard H13 or QRO 90 Supreme at 48-50 HRC, plasma nitride with a thin compound layer, AlTiN PVD on top. The PVD is the key feature against aluminum pickup. Premium ESR is overspec.

Heavy drop-forge hammer die, gross cracking through corners: H11 at 44-46 HRC, gas nitride with a γ' compound layer to support impact, or Nitralloy 135M for a deeper softer-core build. H13 is the wrong reflex; the application is toughness-limited.

Hot extrusion die for aluminum, sliding wear and erosion: QRO 90 Supreme or H13 at 48-50 HRC, deep gas nitride with ε-phase compound layer for sliding contact, optional CrN PVD on the bearing surface. Hot-hardness retention is doing the work.

Warm-forging punch below 350°C, wear-dominant: CPM 1V at 58-62 HRC, light nitride or none, no PVD. The PM substrate carries the load on its own.

Pushback questions for the steel supplier

  1. What failure mode does the recommended grade target on my application, and what data supports that recommendation against my current grade?
  2. Is the steel ESR or VAR remelted, what microcleanliness rating per ASTM E45 will appear on the certificate, and what NADCA #207 grade will the carbide segregation be reported against?
  3. What temper resistance does the grade show at 600°C and 100 hours hold, starting from the hardness I will run the die at, and is the data measured per ASTM E92 hot hardness or estimated from temper curves?
  4. If a premium grade is being recommended, what is the side-by-side life extension you have measured on a comparable forge application, and is that data from your lab or from a customer?

A supplier who can answer all four is engineering the application. A supplier who answers none is moving inventory, and the grade they recommend is a function of what they have in stock.

Common confusions

Premium H13 is not a different chemistry from standard H13. ESR and VAR remelting changes cleanliness and carbide banding inside the same nominal composition. Treating premium as "better steel" without checking the failure mode is how the wrong upgrade gets specified.

Caldie is a cold-work grade. It belongs in AHSS blanking and cold forging tooling, not in a hot-forge die specification. The hot-work premium tier is DIEVAR, QRO 90 Supreme, W360 ISOBLOC, and W302 SUPERIOR.

Erasteel ASP 2030 is PM high-speed steel for cutting and cold-work tools. The PM hot-form analog for forge dies is Crucible CPM 1V, and CPM 3V where toughness over wear is the priority.

AISI grade designations are not standalone documents. H11 and H13 specs live inside ASTM A681, and the carbide segregation and cleanliness criteria the industry actually acceptance-tests against live inside NADCA #207.

Hardness rating in HRC does not specify a hot-work steel. A 48 HRC H13 die and a 48 HRC DIEVAR die have different temper resistance and different K_IC at the same nominal hardness, and the service life numbers separate accordingly. The grade and the heat-treat path are what the spec actually pins down.

Up next: cavity design and stress concentration.

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