Nástrojová ocel D2 a Nerezová ocel 440C are often regarded as highly esteemed yet controversial representatives within the industry. D2’s exceptional wear resistance and high hardness in cold work applications set the benchmark, while 440C remains a common choice for corrosion-resistant cutlery and bearings. This article aims to provide a detailed and objective comparison of these two materials, offering readers the insights needed to make informed decisions. Although both D2 and 440C fall within the category of high-carbon steels, they exhibit significant differences in corrosion resistance, toughness, and superior edge retention properties.
At a Glance: D2 vs. 440C Comparison Table
| Funkce | Nástrojová ocel D2 | Nerezová ocel 440C |
| Type of Steel | High-carbon, High-chromium cold-work tool steel | High-carbon, High-chromium martensitic stainless steel |
| Klíčové legující prvky | Carbon (~1.5%), Chromium (~12%), Molybdenum (~0.8%), Vanadium (~0.9%) | Carbon (~1.0%), Chromium (~17%), Molybdenum (~0.5%) |
| Typická tvrdost (HRC) | 58-62 HRC (can reach 64 HRC as-quenched) | 59-60 HRC (can reach up to 64 HRC) |
| Odolnost proti opotřebení | Extremely high; a benchmark for abrasion resistance | Good abrasion resistance; suitable for wear-resistant applications |
| Houževnatost | Low to moderate | Low; poor toughness due to high carbon content and hardness |
| Odolnost proti korozi | Moderate (for a tool steel); generally inferior to true stainless steels due to carbide precipitation | Good (for a martensitic stainless steel); widely used where corrosion resistance is a primary concern. However, martensitic grades generally have the lowest corrosion resistance among stainless steels. |
| Obrobitelnost | Poor; difficult to machine and grind due to high alloy content | Moderate; generally better than D2 |
D2 Tool Steel Overview
D2 steel is an air-hardening, high-carbon, high-chromium tool steel. It has high wear and abrasion-resistant properties.
Složení
| uhlík (C) | Chrom (Cr) | molybden (Mo) | Vanad (V) | mangan (Mn) | křemík (Si) | fosfor (P) | síra (S) |
| 1,40 – 1,60% | 11.00 – 13.00% | 0,70 – 1,20% | 0,50 – 1,10% | 0,10 – 0,60% | 0,10 – 0,60% | ≤ 0,030% | ≤ 0,030% |
Key Properties of D2 Steel
- Tvrdost. Typically 57-62 HRC (Rockwell Hardness Scale).
- Odolnost proti opotřebení. Excellent.
- Zachování hran. Excellent, holds edge longer than 440C.
- Houževnatost. Good, generally lower than 440C.
- Odolnost proti korozi. Good, but less corrosion-resistant than 440C.
- Obrobitelnost. Difficult to machine.
Aplikace
- Industrial cutting tools: punches, dies, shear blades, milling cutters, reamers.
- Heavy-duty knife blades require prolonged edge retention.
- Forming tools: stamping dies, extrusion tooling, and forging tools.
- Wear parts and machine components (e.g., bearings, injection screws, gears, shafts).
- Plastic molds.
440C Stainless Steel Overview
440C steel is a high-carbon, high-chromium martensitic stainless steel. It has high hardness, wear resistance, and corrosion resistance.
Složení
| uhlík (C) | Chrom (Cr) | mangan (Mn) | křemík (Si) | molybden (Mo) | fosfor (P) | síra (S) |
| 0.95 – 1.20% | 16.0 – 18.0% | 1.00% max | 1.00% max | 0,751 TP3T max | 0.040% max | 0,0301 TP3T max |
Key Properties of 440C Stainless Steel
- Tvrdost. High, typically 58-60 HRC.
- Odolnost proti opotřebení. Good, but slightly less than D2.
- Zachování hran. Good, but slightly less than D2.
- Houževnatost. Fair to good, generally better than D2.
- Odolnost proti korozi: Excellent.
- Obrobitelnost. Relatively easy machinability.
Aplikace
- Cutlery and knives: professional chef knives, hunting knives, everyday kitchen cutlery, and high-performance knives.
- Surgical instruments: scalpels, dental tools, and medical scissors.
- Bearings and bushings (ball bearings, roller bearings).
- Industrial valves: control valves, gate valves, check valves.
- Marine hardware: boat fittings, fasteners, underwater equipment.
D2 vs. 440C Property by Property
- Tvrdost: Tvrdost oceli D2 is 64 HRC, while 440C achieves a maximum hardness value of 60 HRC. However, in practice, the specific hardness value varies depending on the material composition and tepelné zpracování proces a také souvisí se specifickým použitím materiálu.
- Odolnost proti opotřebení: Both steels exhibit excellent nosit resistance due to the formation of hard carbides resulting from their high carbon and chromium content. D2 steel has the best wear resistance of all tool steels. The wear resistance of 440C steel is crucial in its application as cutting tools.
- Houževnatost: Compared to shock-resisting tool steels (S series), neither D2 nor 440C has particularly high toughnessD2 má střední houževnatost, zatímco 440C má nízkou houževnatost.
- Odolnost proti korozi: 440C has excellent corrosion resistance, which is also its original design purpose. 440C is suitable for use in corrosive environments. Although D2 has good oxidation resistance and stain resistance, its overall corrosion resistance cannot compare with that of 440C.
- Obrobitelnost a brousitelnostOba typy oceli se v kaleném stavu obtížně obrábějí a brousí.
- SvařitelnostOceli D2 a 440C se při použití tradičních svařovacích metod obtížně svařují kvůli velkému množství karbidů v jejich vnitřní struktuře. Údajně však existují specializované svařovací metody, které jsme dosud neměli možnost prozkoumat.
- Maintenance Requirements. 440C stainless steel has excellent corrosion resistance, so it does not require frequent cleaning and drying, resulting in low maintenance costs. D2 steel has higher maintenance costs and requires regular oiling and drying to prevent rust, especially in humid environments.
- Náklady. D2 is generally more affordable than 440C.
Výběr správné oceli
- Pokud je primárním účelem aplikace prodloužit životnost nástroje při tváření za studena a neexistují silné korozivní podmínky, jako je velkoobjemové stříhání, tváření nebo ražení, pak je D2 materiálem volby. D2 může dosáhnout maximální odolnosti proti opotřebení po vhodném dvojitém popouštění, což je extrémně ekonomické pro dlouhodobou výrobu.
- Pokud aplikace vyžaduje odolnost proti korozi, vysokou tvrdost a odolnost proti skvrnám, například u řezných nástrojů ve vlhkém prostředí nebo mechanických součástí potravinářské kvality, pak je 440C jasnou volbou. 440C má odolnost proti vlivům prostředí, které se D2 nemůže rovnat.
- Pokud je houževnatost v pracovních podmínkách vysokou prioritou, nejsou ani D2, ani 440C dobrou volbou. Velké množství karbidů uvnitř je činí méně houževnatými.
- If the working conditions require high toughness, neither D2 nor 440C is a good choice. The large amount of carbides inside them reduces their toughness. Similarly, these carbides also make them difficult to weld. These two materials are not suitable for applications that require welding.
Fundamentally, the most prominent feature of D2 is its excellent wear resistance, rather than corrosion resistance. 440C is high-hardened, high-wear-resistant, and corrosion-resistant.
