Steel 1.2738 · hardness band
Steel 1.2738 Prehard HH
Properties of the Prehard HH condition, compared with the other 1.2738 tempers.
Pick the 36–40 HRC (340–380 HB) pre-hardened delivery for long-life tools and filled-resin molds; wear resistance and polishability improve while machinability drops.
What is 1.2738 Prehard HH?
1.2738 Prehard HH is 1.2738 heat treated to Prehard HH — pick the 36–40 HRC (340–380 HB) pre-hardened delivery for long-life tools and filled-resin molds; wear resistance and polishability improve while machinability drops. 1.2738 Prehard HH has a yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). 1.2738 Prehard HH has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). Annealed is the default condition FabDigit quotes; Prehard HH is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 82/100, better than 98% of steel grades
- High strength — 1,030 MPa (149 ksi), better than 93% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
1.2738 Prehard HH properties
Typical room-temperature values for 1.2738 Prehard HH — 12 properties are specific to this condition; the rest are grade-level values shared by every 1.2738 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
1.2738 Prehard HH has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
1.2738 Prehard HH has a yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
1.2738 Prehard HH is rated for continuous service to 400°C (752 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 12.4 µm/m·K (6.89 µin/in·°F).
Electrical3
1.2738 Prehard HH conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 1.2738 Prehard HH takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
1.2738 Prehard HH's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (50/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 1.2738 tempers and conditions
1.2738 is also supplied in 6 other conditions. The full side-by-side table is on the 1.2738 overview.
- AnnealedDefaultPick soft annealed stock at =235 HB for blanks needing heavy roughing, cold work or deep-hole drilling before through hardening and tempering; as-delivered strength and wear resistance are low.470 MPa yield · 19 HRC
- Hardened 50HRCChoose the as-quenched plus low-temper 50–52 HRC state, the maximum hardness attainable, only for small wear inserts; toughness is low and distortion and cracking risk are significant.1,450 MPa yield · 51 HRC
- Q&TChoose re-austenitizing at 850–880 °C with oil or air quench and temper to 40–46 HRC for small or high-wear inserts; accept quench distortion and the finish machining it forces.1,200 MPa yield · 43 HRC
- Prehard HHPick the 36–40 HRC (340–380 HB) pre-hardened delivery for long-life tools and filled-resin molds; wear resistance and polishability improve while machinability drops.1,030 MPa yield · 38 HRC
- ESR PrehardUse the electroslag-remelted, 30–34 HRC pre-hardened grade for optical parts, high-gloss surfaces and deep-etched textures, where low inclusion content gives consistent polishing and texturing.880 MPa yield · 32 HRC
- PrehardUse the standard 28–34 HRC (290–330 HB) pre-hardened delivery to cut cavities and go straight into production with no further heat treatment and no quench distortion risk.860 MPa yield · 31 HRC
Working with 1.2738 Prehard HH
Is 1.2738 easy to machine?
In the prehardened 28–34 HRC condition it mills and drills predictably with coated carbide, moderate cutting speeds and ample coolant. On deep cavity roughing leave 0.3–0.5 mm finishing stock so stress-relief movement can be machined away.
Can 1.2738 be welded?
Preheat to 250–325 °C before repair welding, use matching mould-steel filler at low current with multiple small passes, then temper immediately just below the original tempering temperature to restore hardness and prevent cracking.
Can 1.2738 be formed, bent or molded?
Not cold formed; stock is supplied hot-rolled or forged and quenched and tempered. If re-hardening is needed, austenitise at 850–880 °C, oil quench or pressurised gas quench, then temper twice at 550–620 °C.
What surface finishes work on 1.2738?
Polishes to a mirror finish and suits chemical texturing/photo-etching. It rusts in service, so hard chrome, electroless nickel, nitriding or PVD is common, and idle tools should be coated with rust-preventive oil.
1.2738 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.35 – 0.45 | 0.4 |
| Si | 0.2 – 0.4 | 0.3 |
| Mn | 1.3 – 1.6 | 1.45 |
| Cr | 1.8 – 2.1 | 1.95 |
| Mo | 0.15 – 0.25 | 0.2 |
| Niadded versus 1.2311; increases hardenability | 0.9 – 1.2 | 1.05 |
| Pimpurity upper limit | ≤ 0.03 | — |
| Simpurity limit; mirror-finish grade usually ≤ 0.005 | ≤ 0.03 | — |
| Fe | balance | — |
1.2738 Prehard HH — frequently asked
What is 1.2738 Prehard HH used for?
1.2738 Prehard HH is typically used for injection mould cavity and core plates, mould inserts, large mould bases and bolsters, photo-etched (textured) cosmetic tooling, polished housing and lens cavities and blow mould bodies. In short: workhorse cavity mold plate.
What is the yield strength of 1.2738 Prehard HH?
1.2738 Prehard HH has a typical yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,200 MPa (174 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 1.2738 Prehard HH easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). In the prehardened 28–34 HRC condition it mills and drills predictably with coated carbide, moderate cutting speeds and ample coolant. On deep cavity roughing leave 0.3–0.5 mm finishing stock so stress-relief movement can be machined away.
Can 1.2738 Prehard HH be welded?
With care — weldability is rated fair (50/100). Preheat to 250–325 °C before repair welding, use matching mould-steel filler at low current with multiple small passes, then temper immediately just below the original tempering temperature to restore hardness and prevent cracking.
What surface finishes work on 1.2738 Prehard HH?
Polishes to a mirror finish and suits chemical texturing/photo-etching. It rusts in service, so hard chrome, electroless nickel, nitriding or PVD is common, and idle tools should be coated with rust-preventive oil.
Can 1.2738 Prehard HH be formed, bent or molded?
Not cold formed; stock is supplied hot-rolled or forged and quenched and tempered. If re-hardening is needed, austenitise at 850–880 °C, oil quench or pressurised gas quench, then temper twice at 550–620 °C.
What is the maximum service temperature of 1.2738 Prehard HH?
1.2738 Prehard HH is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 1.2738 Annealed and 1.2738 Prehard?
Annealed is the default condition — pick soft annealed stock at =235 HB for blanks needing heavy roughing, cold work or deep-hole drilling before through hardening and tempering; as-delivered strength and wear resistance are low. Prehard: use the standard 28–34 HRC (290–330 HB) pre-hardened delivery to cut cavities and go straight into production with no further heat treatment and no quench distortion risk. Yield strength is 470 MPa in Annealed versus 860 MPa in Prehard.
Can FabDigit make parts in 1.2738 Prehard HH?
Yes — 1.2738 Prehard HH is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- EN ISO 4957 Tool steels — ISO/CEN (2018)
- GB/T 1299 / 3Cr2MnNiMo (718) — SAC (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.