H13 Hot-Work Tool Steel – Technical Material Specification
Comprehensive technical specification for H13 hot-work tool steel (AISI/SAE H13, 1.2344, X40CrMoV5-1). Covers chemical composition, mechanical properties, standard Canadian stock sizes, heat treatment, machinability, common defects, and storage guidelines for Canadian fabrication, woodworking, and machining operations.
Material Overview & Common Uses
H13 is a chromium-molybdenum-vanadium alloyed hot-work tool steel known for its excellent combination of high-temperature strength, toughness, and thermal fatigue resistance. It maintains hardness and wear resistance up to 540°C (1000°F). Common applications include aluminum and zinc die-casting dies, extrusion dies, forging dies, hot shear blades, plastic molds, and core pins. In Canadian fabrication shops, H13 is frequently used for injection molds, die-cast tooling, and hot-stamping dies. It is supplied in the annealed condition (typically 180–230 HB) for machinability, then hardened and tempered to 44–52 HRC for service.
Core Technical Properties & Sizing
| Property / Parameter | Value / Description |
|---|---|
| Chemical Composition (wt%) | C 0.32–0.45, Cr 4.75–5.50, Mo 1.10–1.75, V 0.80–1.20, Si 0.80–1.20, Mn 0.20–0.50, P max 0.030, S max 0.030, balance Fe. |
| Physical Properties | Density 7.80 g/cm³, Modulus of Elasticity 210 GPa, Thermal Conductivity ~28 W/m·K at 20°C, Coefficient of Thermal Expansion 11.5 µm/m·°C (20–200°C). |
| Mechanical Properties (Annealed) | Tensile Strength 680–830 MPa, Yield Strength 350–450 MPa, Elongation 15–20%, Hardness 180–230 HB. |
| Mechanical Properties (Hardened & Tempered to 48 HRC) | Tensile Strength ~1800 MPa, Yield Strength ~1500 MPa, Elongation ~8%, Impact Toughness (Charpy V-notch) ~20 J. |
| Standard Canadian Sizes (Annealed) | Round Bar: 1/4" to 12" diameter, lengths 12' or 20' Flat Bar: 1/8" to 6" thick, 1/2" to 12" wide, 12' or 20' Plate: 1/4" to 6" thick, 48" x 96" or 48" x 120" Square Bar: 1/2" to 6" square, 12' lengths Drill Rod: 1/16" to 1" diameter, 36" lengths (precision ground) |
| Tolerances (per ASTM A681) | Hot-rolled rounds: +0.062"/-0.000" up to 4", +0.125"/-0.000" over 4" Cold-finished rounds: +0.002"/-0.000" under 1", +0.003"/-0.000" 1"–4" Flat bar thickness: +0.030"/-0.000" under 2", +0.060"/-0.000" 2"–6" Plate thickness: +0.125"/-0.000" 1/4"–1", +0.250"/-0.000" over 1" |
| Heat Treatment | Annealing: 845–900°C, furnace cool ≤20°C/hr to 650°C, then air cool (≤230 HB) Preheating: 650–760°C Austenitizing: 995–1040°C, soak 30–60 min per inch of thickness Quenching: Forced air or oil (martempering recommended) Tempering: Double temper at 540–620°C, 2 hours each, air cool (final 44–52 HRC) |
Machinability, Tooling & Feeds
H13 in annealed condition has a machinability rating of approximately 50–60% relative to AISI 1112. Recommended tooling and parameters are shown below.
| Operation | Tooling | Speed (SFM) | Feed | Depth of Cut |
|---|---|---|---|---|
| Turning | Carbide C2/C3 | 60–90 | 0.008–0.015 IPR | 0.050–0.150" |
| Milling | Carbide | 80–120 | 0.003–0.006 IPT | Radial 0.020–0.080" |
| Drilling | HSS (M42, T15) | 30–50 | 0.003–0.006 IPR | – |
| Grinding | Al₂O₃ or CBN wheels | – | – | Light passes 0.001–0.002" |
| EDM | – | – | – | Remove recast layer by polishing or stress relief temper |
Use generous coolant (water-soluble oil 5–10% concentration). Avoid dwell or rubbing to prevent work hardening.
Common Defects & Quality Control
| Defect | Description | Mitigation / QC |
|---|---|---|
| Decarburization | Surface carbon loss during hot rolling or heat treatment. Acceptable depth per ASTM A681: ≤0.030" per side for bars under 2" thickness. | Microhardness testing or etching; ensure proper atmosphere during heat treat. |
| Carbide Segregation | Banding of carbides reduces toughness and polishability. | Control by proper homogenization anneal. |
| Thermal Fatigue Cracking (Heat Checking) | Fine surface cracks from repeated thermal cycling in service. | Mitigate by proper preheating and tempering. |
| Quench Cracking | From too rapid cooling or complex geometry. | Use martempering or interrupted quench. |
| Inclusions | Non-metallic inclusions (sulfides, oxides) can cause premature failure. | VAR or ESR improves cleanliness; perform ultrasonic testing per ASTM A388. |
| General QC | Verify hardness (Rockwell C or Brinell), spark test or PMI for alloy verification, check surface for cracks/seams/laps. | For critical dies, ultrasonic testing (UT) per ASTM A388 recommended. |
Storage, Handling & Racking Guidelines
Store H13 in a dry, indoor environment with relative humidity below 60% to prevent surface rust. Rack bars on wooden or plastic supports to avoid contact with moisture and dissimilar metals (galvanic corrosion). For long bars, use cantilever racks with padded arms spaced every 4–6 feet to prevent sagging. Plates should be stored flat on pallets or in vertical racks with edge protectors. Apply a light rust-preventive oil (e.g., LPS-3 or equivalent) if storing for more than 30 days. Avoid stacking heavy bars on top of each other without separators to prevent surface damage. For heat-treated H13, handle with clean gloves to avoid oil contamination. Mark each piece with heat number and size for traceability. In Canadian climates, allow material to acclimate to shop temperature (20°C ±5°C) before machining to avoid dimensional changes.