P20 vs H13 vs S7 vs D2: Which Tool Steel for Which Mold Part
Pick the wrong tool steel and the mold cracks at 30,000 shots instead of 300,000 — then the replacement die, the lost production and the two-week shutdown cost far more than the steel ever did. This guide is the 30-second decision tree: P20 for plastic injection, H13 for die casting and hot work, D2 for cold-work wear, S7 for shock and impact.
The Quick Answer — Four Steels, Four Jobs
Tool steel selection is an application-first decision, not a strength-first one. The four grades that cover most mold and die work:
| Grade | Family | Typical hardness (HRC) | Pick it for |
|---|
| P20 (1.2311) | Plastic mold steel, pre-hardened | 28–34 | Injection mold cores and cavities, plastic tooling |
| H13 (1.2344) | Hot-work chromium steel | 48–52 | Die casting, hot forging, extrusion dies |
| D2 (1.2379) | Cold-work, high-carbon high-chromium | 58–62 | Blanking/stamping dies, shear blades, wear parts |
| S7 (1.2355) | Shock-resistant | 52–58 | Impact-loaded punches, chisels, heavy-duty dies |
Rule of thumb Plastic at room temperature → P20. Molten metal and heat → H13. Cold cutting and wear → D2. Impact and shock → S7. When two could work, let cost and section size decide.
P20 — The Plastic Injection Workhorse (28–34 HRC)
P20 (DIN 1.2311, ~0.28–0.40 C, 1.4–2.0 Cr, 0.6–1.5 Mn, 0.2–0.55 Mo) is delivered pre-hardened at roughly 28–34 HRC, which means no heat treatment after machining — no distortion, no cracking risk, immediate delivery of a finished cavity.
- Strengths: excellent machinability, good polishability, moderate cost, nitridable for higher surface hardness.
- Limits: above ~400 mm section, through-hardness becomes inconsistent; not for high-temperature or high-wear service.
- Typical uses: injection mold cores and cavities, mold bases, compression and RIM tooling, low-volume die casting of zinc.
Pre-hardened advantage Because P20 needs no post-machining heat treatment, there is no distortion to correct and no risk of cracking a finished cavity in quench — the single biggest reason it dominates plastic mold work.
H13 — The Hot-Work Champion (48–52 HRC)
H13 (DIN 1.2344, ~0.32–0.45 C, 4.75–5.5 Cr, 1.1–1.75 Mo, 0.8–1.2 V, 0.8–1.2 Si) is the most widely used hot-work tool steel: it keeps hardness and toughness at service temperatures up to ~500°C and resists thermal shock and heat checking.
- Strengths: excellent toughness and fatigue resistance at temperature, good thermal-shock resistance, tolerant of water cooling in service, nitridable.
- Heat treatment: austenitize ~1900–2050°F (1038–1121°C), air or oil quench, double temper at 900–1100°F (482–593°C) for 48–52 HRC.
- Typical uses: aluminum die-casting dies, hot forging dies, extrusion dies and stems, hot shear blades.
Don't use H13 cold At room temperature H13's 48–52 HRC is overkill-soft for wear and it costs more than D2; it earns its premium only when the die runs hot.
D2 — The Cold-Work Wear Monster (58–62 HRC)
D2 (DIN 1.2379, ~1.40–1.60 C, 11–13 Cr, 0.7–1.2 Mo, 0.9–1.1 V) is a high-carbon, high-chromium cold-work steel that air-hardens to 58–62 HRC with minimal distortion, giving outstanding wear and abrasion resistance plus mild corrosion resistance from its chromium.
- Strengths: highest wear resistance of the four, stable in hardening (low distortion), capable of being nitrided, machinable in annealed condition.
- Trade-off: lower toughness — D2 can chip or crack under heavy impact; not for shock-loaded edges.
- Typical uses: blanking and fine-blanking dies, forming and deep-drawing dies, shear blades, punches, slitting cutters, thread-rolling dies, abrasive-mold tooling.
S7 — The Shock-Absorber (52–58 HRC)
S7 (DIN 1.2355, ~0.45–0.55 C, 3.0–3.5 Cr, 1.3–1.8 Mo) is the shock-resistant grade: it is designed to absorb impact energy without fracturing, at a hardness of roughly 52–58 HRC.
- Strengths: highest impact toughness of the four; resists chipping under sudden loading; good combination of hardness and ductility.
- Trade-off: lower wear resistance than D2 — on abrasive work it wears faster.
- Typical uses: impact punches, chisels, shear blades taking shock loads, heavy-duty and coining dies, cold chisels, tools subject to hammering.
S7 vs D2 in one line If the die edge takes impact, S7; if it takes abrasion, D2. Impact fractures D2 edges, abrasion wears S7 away.
The Cost of Getting It Wrong — A $50K Replacement
The failure mode that makes tool steel selection a financial decision: a mold spec'd for the wrong steel cracks or wears out after ~30,000 shots instead of the expected several hundred thousand. The replacement cost is not the steel — it is the new mold blank, the machining time, the trial iterations and the production line standing still, routinely in the $30,000–$50,000+ range plus 1–2 weeks of downtime for a medium-size die.
Draft note (pending Sinbo review) The 30K-shots failure and $50K replacement figures are synthesized from standard industry experience (mold-making practice) and supplier material pages, not from Sinbo's internal tooling log. Sinbo engineers should replace illustrative numbers with real shop data before translation.
The practical rule: if the application is borderline, upgrade the steel before the mold is cut — the incremental steel cost is a rounding error against a mid-life mold failure.
The Decision Tree — Application → Steel → Machining Notes
| If the part is… | Choose | Machining note |
|---|
| Injection mold core/cavity, standard plastic | P20 (28–34 HRC pre-hardened) | Machine in delivery condition; no post HT; polish then optional nitride |
| Injection mold, high wear or 400+ mm section | P20 + nitride or upgrade to H13 | Nitride after finish machining |
| Die casting / hot forging / extrusion die | H13 (48–52 HRC) | Rough, heat treat, finish; double temper; stress-relieve weld repairs |
| Blanking/stamping die, shear blade, wear part | D2 (58–62 HRC) | Machine annealed, heat treat, finish grind or wire EDM |
| Impact punch, chisel, shock-loaded die | S7 (52–58 HRC) | Machine annealed, heat treat, temper for toughness target |
| Mold sliders / small inserts under impact | S7 or D2 by loading type | Impact → S7; abrasion → D2 |
Grade equivalencesP20 = DIN 1.2311 = JIS (approx. SKT3/SKD61 family differs — verify) P20 is 1.2311 (40CrMnMo7) per DIN.
H13 = DIN 1.2344 = JIS SKD61 = GB Cr5Mo1V H13 is X40CrMoV5-1 per DIN.
D2 = DIN 1.2379 = JIS SKD11 = GB Cr12MoV D2 is X153CrMoV12 per DIN.
S7 = DIN 1.2355 (55CrMoV7-8-14 per DIN; no universal JIS equivalent — confirm against the local standard).
How to Specify the Steel on Your RFQ
- Name the grade and standard: e.g. “H13 per ASTM A681, DIN 1.2344” — never just “tool steel”.
- State the hardness target and scale: e.g. “48–52 HRC, tested per ASTM E18”.
- State the delivery condition: pre-hardened (P20), annealed (D2/S7/H13 for machining), or finished hardened.
- For hot-work and cold-work steels, require the heat-treatment certificate (quench/temper cycle, actual hardness) — the grade on paper is meaningless without the heat treatment that realizes it.
- For cast/machined cavities, add material verification (PMI or mill cert) when the die is safety- or production-critical.
Standards & Sources
Primary standardsASTM A681 Standard specification for tool steels alloy (covers P20, H13, D2, S7 chemistry).
ISO 4957 Tool steels — designation and delivery conditions (DIN/EN equivalents 1.2311, 1.2344, 1.2379, 1.2355).
ASTM E18 Rockwell hardness testing (HRC verification).
ASTM E415 / E1251 Spectrometric composition analysis (material verification).
Application referencesSanyao Forging Top 10 Types of Mold Steels — composition and hardness by grade (P20 28–32, H13 48–52, D2 60–62, S7 54–58).
Createel Tool & Die Steel grades table — P20 30–36, H13 44–52, D2 58–62, S7 54–56; DIN equivalents and heat-treatment cycles.
Panjin International What Is Die Steel — grade comparison (P20 28–34, H13 48–52, D2 58–62, S7 52–58) and selection factors.
Kens Metal Tool Steel grades — P20 composition and 400 mm section limit; H13 hot-work applications; D2 applications.
Vast-Cast Tool Steel comparison — heat-treatment steps and achievable hardness (P20 30–36, H13 48–52, D2 58–62, S7 50–56).
Frequently Asked Questions
Which tool steel should I use for an injection mold?
P20, pre-hardened at 28–34 HRC, for standard plastic injection molds. It machines well in delivery condition, needs no post-machining heat treatment (so no distortion), polishes well and can be nitrided for more surface hardness. For very high-wear resins, sections above ~400 mm, or hot-runner-heavy molds, consider P20 + nitride or upgrade to H13.
Is H13 only for die casting, or can it do other jobs?
H13 is the hot-work grade — die casting, hot forging and extrusion — and it can also serve plastic molds that run hot. Its strength is keeping hardness and toughness at service temperatures up to ~500°C with good thermal-shock resistance. At room temperature it is overkill-soft for wear and costs more than cold-work grades, so don't use it for stamping or blanking.
What's the difference between D2 and S7?
D2 is for wear, S7 is for impact. D2 (58–62 HRC) is a high-carbon, high-chromium cold-work steel with the best abrasion resistance of the four but lower toughness — it chips under heavy shock. S7 (52–58 HRC) is the shock-resistant grade: lower wear resistance but it absorbs impact without fracturing. Impact loads → S7; abrasive wear → D2.
Does P20 need heat treatment after machining?
No — that's the point of pre-hardened P20. It is supplied at 28–34 HRC, so you machine the finished cavity directly and skip quench and temper entirely, eliminating distortion and quench-cracking risk. If you need more surface hardness, nitride after finish machining.
How much does choosing the wrong mold steel actually cost?
Typically a $30,000–$50,000+ replacement plus 1–2 weeks of downtime for a medium-size die. A mold that cracks at ~30,000 shots instead of several hundred thousand fails because the steel couldn't take the temperature, wear or impact. The incremental cost of the right steel is a rounding error against that failure — upgrade before the mold is cut.
How do I specify tool steel so my supplier doesn't guess?
Name the grade and standard, the hardness target, and the delivery condition. For example: “H13 per ASTM A681 / DIN 1.2344, 48–52 HRC, machined in annealed condition then hardened and double-tempered.” Add the heat-treatment certificate requirement and material verification (mill cert or PMI) for production-critical dies.
Sources & Standards Referenced
- ASTM A681: Standard Specification for Tool Steels Alloy (P20, H13, D2, S7 chemistry requirements)
- ISO 4957: Tool steels — designation and delivery conditions (DIN/EN 1.2311, 1.2344, 1.2379, 1.2355 equivalents)
- ASTM E18: Standard test methods for Rockwell hardness of metallic materials (HRC verification)
- ASTM E415 / E1251: Spectrometric analysis of carbon and low-alloy steel (composition verification)
- Sanyao Forging: Top 10 Types of Mold Steels — composition and hardness by grade (P20 28–32, H13 48–52, D2 60–62, S7 54–58 HRC)
- Createel: Tool & Die Steel — grades table with DIN equivalents and heat-treatment cycles (P20 30–36, H13 44–52, D2 58–62, S7 54–56 HRC)
- Panjin International: What Is Die Steel? — grade comparison and selection factors (P20 28–34, H13 48–52, D2 58–62, S7 52–58 HRC)
- Kens Metal: Tool Steel grades — P20 composition and 400 mm section limit; H13 hot-work applications; D2 cold-work applications
- Vast-Cast: Tool Steel properties, grades, comparison — heat-treatment steps and achievable hardness (P20 30–36, H13 48–52, D2 58–62, S7 50–56 HRC)
Need Tool Steel Machined to Spec?
Send your mold or die drawing — we'll confirm the steel grade, heat-treatment route and machining strategy, and return a DFM review within 3 business days.
Request a Quote