Our Blog

AISI D2 Steel - Annealed vs Heat treatment Properties

D2 material is one of the most widely‑used high‑carbon high‑chromium cold‑work tool steels worldwide. Its good machinability in the annealed state and high hardness plus great wear resistance in the quenched‑tempered state are achieved by heat treatment. Its hardness jumps from ≤255 HB to 60‑62 HRC, and tensile strength rises from about 700 MPa to 1764 MPa. This article systematically compares the property differences of AISI D2 steel between annealed and quenched‑tempered states.

Table of Content

Hot product

AISI D2 Steel
D2 vs 154CM
AISI D2
D2 Steel
D2 Material
D2 Tool Steel
D2 Metal
AUS 8 vs D2
Nitro V vs D2
D2 vs 14C28N

AISI D2 Steel Composition

Element

Content Range (wt%)

Function

C

1.40‑1.60

Basis for hardness and wear resistance

Si

≤ 0.60

Deoxidizer, improves strength

Mn

≤ 0.60

Improves hardenability

P

≤ 0.030

Harmful impurity, strictly controlled; high content reduces toughness

S

≤ 0.030

 Harmful impurity, strictly controlled; high content damages transverse properties

Cr

11.00‑13.00

Forms carbides, provides wear resistance

Mo

0.70‑1.20

Boosts hardenability and temper resistance

V

0.50-1.10

Refines grain size, improves toughness

AISI D2 steel is a high‑carbon high‑chromium cold‑work tool steel under US AISI standard. It contains C: 1.40‑1.60%, Cr: 11.00‑13.00%, Mo: 0.70‑1.20%, V: 0.50‑1.10%. Large amounts of carbon and chromium form hard chromium carbides during heat treatment, giving D2 legendary wear resistance. As a ledeburitic steel, it delivers high hardenability, high hardening capacity and excellent wear resistance.

Properties of Annealed AISI D2 Steel

D2 cold work steel you buy is usually supplied in the annealed condition.
 
  • Hardness: 230 HB
  • Tensile strength: 760 MPa
  • Yield strength: 470 MPa
  • Elongation: 16%
  • Machinability rating: 50% (100% baseline for 1% carbon steel). It supports turning, milling, drilling and tapping.
  • Elastic modulus: 190 GPa
  • Shear strength: 460 MPa

Comprehensive Properties of Quenched‑Tempered D2 Material

  • Hardness: 59‑62 HRC, increased by around 40 HRC compared with the annealed condition.
  • Tensile strength: 2000 MPa, increased by around 163% compared with the annealed condition.
  • Yield strength: 1510 MPa, increased by around 221% compared with the annealed condition.
  • Elongation: 5%, decreased by around 69% compared with the annealed condition. Higher hardness brings lower ductility.
  • Elastic modulus: 190 GPa, nearly unchanged between quenched‑tempered and annealed conditions.
  • Shear strength: 1160 MPa, increased by around 152% compared with the annealed condition.
  • Compressive strength: approx 2100 MPa.
  • Fatigue strength: 860 MPa.

Heat Treatment Process of AISI D2 Steel

Quenching Process of AISI D2 Steel

Quenching of AISI D2 steel requires multi‑step preheating.
  • First preheat: Heat to 820°C, hold for 15‑30 minutes.
  • Second preheat: Heat to 850°C, hold for 30 minutes.
  • Final heating: 1000‑1010°C for salt‑bath furnace or 1010‑1040°C for controlled‑atmosphere furnace, hold for 25‑40 minutes.
  • Cooling method: Air cooling (D2 Steel is an air‑hardening steel).
  • Hardness after quenching for AISI D2: ≥59 HRC.

 

Tempering Process

AISI D2 Steel must be tempered immediately after quenching to avoid cracking.
  • Tempering cycles: Minimum two cycles. Three tempering cycles can improve impact toughness by 25%.
  • Low‑temperature tempering (180‑230°C): AISI D2 steel reaches 60‑62 HRC.
  • High‑temperature tempering (500‑560°C): D2 material reaches approx 54 HRC.
  • Secondary hardening tempering (482‑516°C / 900‑960°F): Highly recommended. Tempering within this range triggers secondary hardening effect and delivers optimal hardness for D2 tool steel.

Principles Behind Property Changes of D2 Tool Steel

The dramatic property leap of D2 from annealed condition to quenched‑tempered condition comes from profound changes in its microstructure:
  • Dissolution and precipitation of carbides: During quenching heating (1020‑1040°C, large amounts of carbon and chromium dissolve into the austenite matrix. Subsequent rapid air cooling forms martensite structure. Numerous fine alloy carbides precipitate during tempering.
  • Source of hardness: Final hardness comes from the combined contribution of martensite matrix hardness plus hardness of dispersed carbides. D2 mainly features M₇C₃‑type carbides with extremely high hardness.
  • Trade‑off for toughness: Sharp hardness increase is accompanied by obvious drop in ductility — elongation falls from around 16% to roughly 5.1%. D2 has relatively low toughness and is not suitable for heavy‑impact or thick‑plate shearing service conditions.

FAQ of AISI D2 Steel:

Q1: Why can AISI D2 steel reach 60 HRC after quenching while its annealed hardness is ≤255 HB?

A: The microstructure of annealed AISI D2 steel consists of ferrite plus spherical carbides, leading to low hardness. Quenching heats AISI D2 into the austenite region, where carbon and alloying elements dissolve into austenite. Rapid cooling produces martensite, a hard and brittle structure. The hardness jumps from 230 HB to 60‑62 HRC as a result of microstructural transformation.

A: Quenched D2 die steel contains extremely high internal stress. Volume expansion occurs when austenite transforms into martensite, generating massive microstructural stress. Without timely tempering, AISI D2 Steel may crack spontaneously during cooling or handling.

A: No. D2 steel requires at least two tempering cycles. Retained austenite partially transforms into fresh martensite during the first tempering. The second tempering relieves stress induced by this newly‑formed martensite. Three tempering cycles can improve the impact toughness of D2 material by 25%.

A: No. Optimal performance of D2 mold steel is obtained within 1000‑1040°C. Below 1000°C, alloying elements cannot dissolve sufficiently and hardness cannot reach target values. Above 1040°C, grain growth takes place and toughness decreases. Higher quenching temperature does not equal better performance for AISI D2 steel.

A: No. D2 tool steel is an air‑hardening steel and hardens under air cooling with low thermal stress. Its distortion level during heat treatment ranks among the lowest for tool steels. Nevertheless, multi‑step preheating and controlled heating rate are still required for complex‑shaped parts.

Conclusion

In the annealed condition, AISI D2 steel features hardness ≤255 HB, tensile strength of 760 MPa and 16% elongation, and it can be machined normally. In the quenched‑tempered condition, D2 tool steel reaches 60‑62 HRC hardness, 2000 MPa tensile strength, 1510 MPa yield strength and 5% elongation.

The same material of AISI D2 shows such huge performance differences before and after heat treatment. Normally Keyspark Steel deliver Annealed D2 round bar and plate to clients. When purchasing D2 material, you must clarify whether you need “annealed‑state blanks for machining” or “finished QT steel”. These two options have totally different machining methods and costs.

More AISI D2 Resources

📩 Contact Keyspark Steel now if you need →

📧 Email: Sales@keysparksteel.com

📱 Mobile/WhatsApp: +86 150 2405 6480

These are our related articles if you want to learn more tool steel comparison:

  1. DC53 Steel vs D2 – Source: Keyspark Steel
  2. The Full Manufacturing Processes of D2 Steel – Source: Keyspark Steel
  3. What is D2 Steel – Source: Keyspark Steel
  4. D2 vs 14C28N – Source: Keyspark Steel
  5. Nitro V vs D2 – Source: Keyspark Steel
  6. AUS 8 vs D2​ – Source: Keyspark Steel
  7. How to improve D2 Metal Properties? – Source: Keyspark Steel
  8. 440C vs D2 – Source: Keyspark Steel
  9. Why Must D2 Material Be Tempered Immediately After Quenching? – Source: Keyspark Steel
  10. AISI D2 – Applications for Cold Work Tool Steel & Industrial Tooling
  11. D2 vs 154CM: Full Steel Comparison Guide

Related Posts