D2 Tool Steel: Kalt vinnutæki stál

1. INNGANGUR

D2 tool steel has long been recognized for its exceptional wear resistance and dimensional stability, making it a staple in cold-working applications.

Originating from the early 20th century’s advancements in alloying technology, D2 is a high-carbon, high-chromium steel that sets the benchmark for tools operating under severe wear conditions.

This article delves into the properties, Vinnsla, and applications of D2 tool steel, answering key questions about its suitability for various industries.

By exploring its chemical composition, physical and mechanical attributes, heat treatment protocols, and machining challenges,

We aim to provide a comprehensive understanding of why D2 remains a preferred choice for demanding tooling requirements.

2. Efnasamsetning

D2 verkfærastál owes its exceptional wear resistance and dimensional stability to a carefully engineered alloy chemistry.

By combining high carbon content with strategic additions of chromium, Molybden, og vanadíum, metallurgists create a matrix rich in hard carbides that resist abrasion and retain cutting edges under heavy load.

Key Alloying Elements and Their Roles

Element	Dæmigert efni (%)	Metallurgical Role
Kolefni (C.)	1.40 - 1.60	Forms cementite and complex chromium carbides; directly correlates with hardness and wear resistance
Króm (Cr)	11.00 - 13.00	Promotes formation of hard M₇C₃ and M₂₃C₆ carbides; adds corrosion resistance; eykur herðleika
Molybden (Mo.)	0.70 - 1.40	Refines prior carbides; enhances toughness and red-hardness; retards grain growth during austenitizing
Vanadíum (V)	0.30 - 1.10	Creates extremely hard MC-type carbides that improve edge retention and resist micro-cracking
Mangan (Mn)	≤ 1.00	Virkar sem afoxunarefni; assists in hardenability but can reduce toughness if over-added
Kísil (Og)	≤ 1.00	Afoxunarefni; contributes modestly to strength and contributes to carbide morphology

Characteristic Carbide Phases

D2’s wear resistance stems from a dual-carbide system:

Chromium-Rich Carbides (M₇C₃, M₂₃C6)

• These chromium carbides appear as blocky or angular precipitates within the tempered martensite matrix.
• They account for roughly 30–40% of the microstructure by volume, providing bulk resistance to abrasive wear.

Vanadium-Rich MC Carbides

• Nanoscale MC particles (rich in vanadium and carbon) distribute uniformly throughout the steel.
• Jafnvel a 5–10% volume fraction of MC carbides dramatically boosts edge retention by impeding crack initiation.

3. Equivalent Brands and Standards

D2 tool steel aligns with several international specifications. Below are the primary equivalents up to the ASTM designation:

Standard/Brand	Tilnefning	Jafngildi	Svæði
AISI/SAE	D2 (UNS T30402)	-	Bandaríkin
Frá	1.2379	D-2	Germany/Europe
Hann er	SKD11	D-2	Japan/Asia
BS	BS 1407M40	D-2	Bretlandi
AFNOR	X210Cr12	D-2	Frakklandi
ASTM	A681	D-2	Alþjóðlegt

4. Vélrænni eiginleika

D2 tool steel balances extreme hardness with sufficient toughness, enabling it to withstand high wear while resisting brittle failure.

The table below summarizes its key mechanical metrics in the quenched-and-tempered condition (Venjulega 60 HRC), followed by a brief discussion of their implications.

Eign	Dæmigert gildi	Einingar	Athugasemdir
Togstyrkur (σₜ)	2 000 - 2 200	MPA	High ultimate strength supports heavy loads in cold-working operations.
Ávöxtunarstyrkur (σᵧ 0.2%)	1 850 - 2 000	MPA	Minimal plastic deformation under high compressive forces preserves dimensional accuracy.
Rockwell C Hardness	58 - 62	HRC	Óvenjuleg yfirborðshörka tryggir frábæra slitþol.
Brinell hörku (HBW)	700 - 750	HBW	Samsvarar HRC fyrir krosstilvísanir í alþjóðlegum stöðlum.
Charpy V-hak	10 - 15	Joules	Fullnægjandi orkuupptaka kemur í veg fyrir skelfilegar sprungur við klippingu og klippingu.
Lenging í hléi	2 - 3	%	Takmörkuð sveigjanleiki; hönnun verður að taka tillit til lítillar aflögunargetu í hertum hlutum.
Toughness Modulus	20 - 25	MJ/m³	Flatarmál undir streitu-þynnukúrfu mælir heildarorkuupptöku fyrir brot.

5. Líkamlegir eiginleikar

Fyrir utan vélrænan árangur, D2 verkfærastál sýnir safn líkamlegra eiginleika sem hafa áhrif á hitaflæði, víddarstöðugleiki, og rafsegulhegðun í þjónustu.

Hér að neðan er yfirlit yfir helstu eðliseiginleika þess í hertu (60 HRC) ástand:

Eign	Dæmigert gildi	Einingar	Athugasemdir & Afleiðingar
Þéttleiki	7.75 g/cm³		Þyngri en vatn, hefur áhrif á massa massa og meðhöndlun.
Stuðull Young (Teygjanlegt stuðull)	205 GPA		Mikil stífleiki tryggir lágmarks teygjanlega sveigju undir álagi.
Hlutfall Poissons	0.28		Gefur til kynna hóflegan hliðarsamdrátt þegar teygt er.
Hitaleiðni	20 W/m · k		Relatively low thermal conductivity aids in heat retention in tooling faces.
Sérstök hitastig	460 J/kg · k		Energy required to raise temperature, relevant for tempering and quench design.
Stuðull hitauppstreymis	11.5 µm/m · k		Thermal expansion effects are moderate, facilitating tight die clearances over temperature cycles.
Rafmagnsþol	0.70 µω · m		Higher resistivity than low-alloy steels, impacting EDM parameters and electrical heating behavior.
Segulgegndræpi (Relative μᵣ)	1.002		Nearly identical to free space; confirms D-2’s non-magnetic (Diamagnetic) character in most applications.
Rockwell C Hardness (Dæmigert, quenched/tempered)	60 HRC		Although a mechanical property, hardness influences surface contact, núningur, and heat generation in use.

6. Hitameðferð & Vinnsla

Optimizing D2 tool steel’s performance hinges on precise heat treatment and careful processing.

By controlling annealing, austenitizing, slökkt, Temping, and optional cryogenic steps,

manufacturers tailor the steel’s hardness, hörku, and dimensional stability to demanding cold-working tasks.

Hreinsun og streitulosun

Tilgangur: Soften D2 for machining, létta afgangsálagi, and spheroidize carbides.

• Málsmeðferð: Heat slowly to 800–820 °C, hold for 2–4 klukkustundir, then cool in the furnace at 20 °C/klst til 650 ° C., fylgt eftir með loftkælingu.
• Niðurstaða: Afrekar ~240 HBW, with uniformly spheroidized carbides that minimize tool wear on cutting edges and prevent chipping.

Before any hardening cycle, nota a pre-stress relief at 650 ° C. fyrir 1 hour to remove machining-induced stresses.

Herða (Austenitizing and Quenching)

Markmið: Transform to martensite and dissolve sufficient carbides for maximum wear resistance.

Austenitizing:

• Hitastig: 1 020–1 040 ° C.
• Soak Time: 15-30 mínútur (fer eftir þykkt hluta)
• Andrúmsloft: Controlled-atmosphere furnace or salt bath to prevent decarburization and oxidation.

Slökkt:

• Fjölmiðlar: Warm oil (50–70°C) or air for minimal distortion; salt bath quench (400–500 °C) for faster cooling and reduced stress.
• Röskun stjórn: Use fixtures or interrupted quench techniques, sérstaklega fyrir flóknar rúmfræði.

Niðurstaða: Yields ~62 HRC maximum and a martensitic matrix with fine, dispersed carbides.

Tempering Cycles

Markmið: Balance hardness and toughness, draga úr brothættu, and relieve quench stresses.

• Lághitatemprun (150–200 ° C.):

• • Niðurstaða: Hardness remains 60–62 HRC, with modest toughness. Ideal for applications demanding extreme wear resistance and edge retention.

• Miðlungshitahitun (500–550 °C):

• • Niðurstaða: Hardness drops to 55–58 HRC while toughness increases by 20–30%. Best for tools exposed to impact or moderate shocks.

• Málsmeðferð: Framkvæma two consecutive tempering cycles, halda 2 klukkustundir hver, fylgt eftir með loftkælingu.

Cryogenic meðferð

Tilgangur: Convert retained austenite to martensite and refine carbide distribution.

• Ferli: Eftir slökun, cool to –80°C (dry ice/ethanol) fyrir 2 klukkustundir, then return to room temperature.
• Gagn: Increases hardness by 2–3 HRC and marginally improves wear resistance without notable loss in toughness.

Final Stress Relief and Straightening

Following tempering (and cryogenic treatment, ef það er notað), conduct a final stress relief at 150–200 ° C. fyrir 1 klukkustund. This step stabilizes dimensions and minimizes the risk of warping during service.

7. Vélhæfni & Framleiðsla

D2 tool steel’s high carbide content and pre-hardened microstructure pose unique challenges during machining and fabrication.

By selecting appropriate tooling, optimizing cutting parameters, and following specialized welding and finishing practices,

manufacturers can produce accurate, high-quality parts while preserving D2’s wear-resistant properties.

Machining Hardened D2

Although annealed D2 (∼240 HBW) machines readily, many applications start with pre-hardened stock (50 ± 2 HRC). In this condition:

• Verkfæri:

• • Karbít innlegg with TiC or TiCN coatings resist abrasion from hard chromium and vanadium carbides.
  • Polycrystalline cubic boron nitride (PCBN) excels for high-volume roughing of hardened surfaces.

• Skurður breytur:

• • Hraði: 60–90 m/min for carbide; 100–150 m/min for PCBN.
  • Feed: 0.05–0.15 mm/rev to balance tool life and surface finish.
  • Depth of cut: 0.5-2 mm; shallow passes reduce cutting forces and heat generation.

• Kælivökvi: Flood coolant or through-tool delivery minimizes built-up edge and keeps cutting zones below 200 ° C., preventing carbide pull-out.

Transitionally, adopting these recommendations enhances surface integrity and dimensional accuracy, critical for tight-tolerance tooling.

Welding and Repair

Welding D2 demands careful control to avoid cracking and preserve the martensitic matrix:

1. Pre-heat: Bring parts to 200–300 ° C. to reduce thermal gradients.
2. InterPass hitastig: Viðhalda 200–250 °C between passes to alleviate residual stresses.
3. Filler Metals: Use low-alloy, high-hardness rod (T.d., AWS A5.28 ER410NiMo) compatible with D2’s chemistry.
4. Hitameðferð eftir suðu: Stress-relieve at 500 ° C. fyrir 2 klukkustundir, then temper according to Section 5 to restore toughness and hardness.

These steps minimize hydrogen-induced cracking and ensure weld zones match base-metal performance.

Grinding and Electrical Discharge Machining (EDM)

For intricate geometries and fine finishes, non-conventional methods excel:

• Mala:

• • Wheel Selection: Use aluminum-oxide or cubic boron nitride wheels (46A60H–54A80H) with soft bonds to prevent glazing.
  • Færibreytur: Light infeed (0.01–0.05 mm) and high wheel speed (30 m/s) yield Ra ≤ 0.4 µm.

• EDM:

• • Die Sinking eða Wire EDM skapar flókin holrúm án þess að valda vélrænni álagi.
  • Dielectric vökvi: Kolvetnisolía með stýrðri skolun kemur í veg fyrir endurútfellingu karbíða.
  • Vinnsluverð: Venjulega 0,1–0,5 mm³/mín, fer eftir rúmfræði rafskauta og aflstillingum.

Með því að taka inn EDM og nákvæmnisslípun getur D2 íhlutum náð næstum nettóformum og speglaáferð en viðhalda fullri hörku verkfærastálsins.

Surface Finishing and Coating

Til að lengja endingu verkfæra enn frekar, íhuga þessa frágangsmöguleika:

• Fægja: Lokabót á Ra ≤ 0.2 µm dregur úr núningi og viðloðun rusl.
• PVD húðun: Títanítríð (Tin) eða áltítanítríði (Gull) lög bæta við harða, yfirborð með litlum núningi, eykur slitþol um allt að 50%.
• Nitriding: Lághita gasnítrun (500 ° C.) dreifir köfnunarefni til að mynda harðnað hylki, eykur yfirborðshörku fyrir HRC 70+ án þess að skekja kjarnavíddir.

8. Key Applications of D2 Cold Working Tool Steel

D2’s balance of wear resistance and toughness suits:

• Cold-work dies: Eyða, myndast, and trimming operations exceeding 1 milljón lotur.
• Cutting blades: High-speed shear knives maintaining sharp edges under abrasive slurries.
• Punch and die sets: Reliable performance in stamped components for automotive and appliance industries.
• Wear parts: Rúllur, útkastapinnar, and bushings in high-abrasion environments.
• Additive-assisted tooling inserts: Hybrid mold inserts combining D2 with conformal cooling channels.

9. Performance Comparison: D2 vs. Other Tool Steels

D2 cold working tool steel is widely recognized for its exceptional wear resistance and moderate toughness.

Samt, in selecting tool steel for manufacturing applications, it’s critical to compare D2 with other popular tool steels to assess trade-offs in performance, Varanleiki, og kostnaður.

This section provides a detailed comparison of D2 with A-2, M-2, and S-7, supported by data and real-world case insights.

Tool Steel Comparison Table

10. Niðurstaða

D2 kaldvinnslustál áberandi fyrir óviðjafnanlega samsetningu slitþols, víddarstöðugleiki, og hitauppstreymi.

Fjölhæfni þess í margs konar notkunarmöguleikum - allt frá hefðbundnum köldu vinnudeyjum til nýrrar aukefnaframleiðslutækni - gerir það að ómissandi efni í nútíma framleiðslu.

Að skilja blæbrigði efnasamsetningar D2, vélrænni eiginleika, og vinnslutækni eflir

verkfræðinga og hönnuði til að nýta alla möguleika sína, tryggja hámarksafköst og skilvirkni í verkefnum sínum.