1.2344 vs 1.2343 – Composition, Heat Treatment, Properties, and Applications

Introduction

Engineers, procurement managers, and manufacturing planners frequently face a choice between closely related hot-work tool steels when designing dies and tooling that must survive thermal cycling, mechanical wear, and high contact stresses. Two commonly compared German-designation grades are 1.2344 and 1.2343. The selection dilemma typically centers on hardenability and hot strength versus notch toughness and cost—i.e., when to prioritize resistance to thermal fatigue and deformation (often requiring higher alloy content and hardenability) and when to prioritize impact resistance and ease of fabrication.

The principal practical difference is that 1.2344 generally corresponds to the H13-type hot-work tool steel (slightly higher carbon, molybdenum and vanadium) and is specified when elevated hardenability and hot strength are required, whereas 1.2343 corresponds to an H11-type composition (marginally lower alloy content) and is chosen when somewhat higher toughness, easier machining, and lower cost are priorities. Because their basic metallurgical family and applications overlap, designers compare them for die casting, forging, extrusion, and hot stamping work.

1. Standards and Designations

• EN/DIN: 1.2344 (X40CrMoV5-1, commonly equated to H13); 1.2343 (X37CrMoV5-1, commonly equated to H11).
• ASTM/ASME: Often referenced by AISI/UNS tool-steel equivalents (H11/H13 family); direct one-to-one ASTM numbers do not replace EN identifiers.
• JIS/GB: Local equivalents exist in JIS/GB catalogs but nomenclature differs; check cross-reference tables for exact matches.
• Classification: Both are hot-work tool steels (tool steel family), not stainless steels or HSLA steels.

2. Chemical Composition and Alloying Strategy

Table — typical composition ranges (wt%, per EN-type specifications and common industrial practice). Values shown are typical ranges; consult material certificates for exact batch chemistry.

Element	1.2344 (H13-type) typical	1.2343 (H11-type) typical
C	0.32 – 0.45	0.32 – 0.40
Mn	0.30 – 0.80	0.30 – 0.60
Si	0.80 – 1.20	0.80 – 1.20
P	≤ 0.03	≤ 0.03
S	≤ 0.03	≤ 0.03
Cr	4.8 – 5.5	4.8 – 5.5
Ni	≤ 0.30	≤ 0.30
Mo	1.10 – 1.75	0.80 – 1.20
V	0.80 – 1.20	0.30 – 0.60
Nb/Ti/B/N	≤ trace (typically nil)	≤ trace (typically nil)
N	typically very low	typically very low

How alloying affects behavior: - Carbon establishes baseline hardenability and hardness potential; higher carbon supports higher tempering hardness but can reduce toughness when combined with high hardenability. - Chromium contributes to hardenability, hot strength and oxidation resistance at elevated temperatures. - Molybdenum increases high-temperature strength, hardenability, and resistance to softening during service. - Vanadium forms very hard carbides that enhance wear resistance and secondary hardening; higher V (as in 1.2344) improves hot wear resistance. - Silicon and manganese are deoxidizers and influence toughness and strength.

Overall strategy: 1.2344’s marginally higher Mo and V give improved hot strength and wear resistance (better for aggressive thermal cycling), while 1.2343’s slightly lower alloying favors toughness and machinability.

3. Microstructure and Heat Treatment Response

Typical microstructure (both grades): tempered martensite matrix with a dispersion of alloy carbides (mainly chromium-rich M7C3/M23C6-type and vanadium-rich MC-type carbides).

• 1.2344: Because of its higher Mo and V, microstructure will include a higher volume fraction of fine vanadium carbides and stronger secondary hardening effects during tempering. This promotes retention of hardness at elevated temperatures and improves resistance to softening during service.
• 1.2343: Exhibits similar tempered martensite but with fewer vanadium carbides; carbide distribution tends to be coarser, which can improve notch toughness.

Heat treatment response: - Typical route: normalize/anneal to refine prior austenite grain size → austenitize (commonly near 1000–1050 °C for H11/H13 family; exact temperature depends on section size and chemistry) → quench (air/oil depending on section and required cooling rate) → multi-stage tempering to stabilize secondary hardening. - 1.2344 responds strongly to secondary hardening during tempering because of Mo and V; careful tempering produces durable hot hardness. However, because of higher hardenability, it is more prone to hard microstructures in thicker sections unless proper preheating and controlled cooling are used. - 1.2343 will generally be easier to avoid quench cracking and to achieve good through-hardening balance in moderate section sizes.

4. Mechanical Properties

Table — comparative description (typical, heat-treatment dependent).

Property	1.2344 (H13-type)	1.2343 (H11-type)
Tensile Strength	High (depends on temper/hardness)	Moderate–High
Yield Strength	High	Moderate–High
Elongation	Moderate (lower at higher hardness)	Slightly higher (more ductile)
Impact Toughness	Good, but lower than 1.2343 at equivalent hardness	Better toughness at equivalent hardness
Hardness (typical quenched & tempered)	44–52 HRC (service-dependent)	42–50 HRC (service-dependent)

Interpretation: After similar quench-and-temper cycles, 1.2344 typically attains comparable or slightly higher hardenability and high-temperature strength than 1.2343 owing to increased Mo and V; however, 1.2343 can be slightly tougher and more forgiving to thermal/mechanical shocks, especially in applications with sharp notches or heavy impact.

5. Weldability

Weldability must be treated cautiously for both grades because alloy content and carbon level promote hard, brittle heat-affected zones (HAZ) if welding procedures are not controlled.

Useful indices: - Carbon equivalent (IIW):
$$CE_{IIW} = C + \frac{Mn}{6} + \frac{Cr+Mo+V}{5} + \frac{Ni+Cu}{15}$$ - Pcm (Welding Preheating Estimate):
$$P_{cm} = C + \frac{Si}{30} + \frac{Mn+Cu}{20} + \frac{Cr+Mo+V}{10} + \frac{Ni}{40} + \frac{Nb}{50} + \frac{Ti}{30} + \frac{B}{1000}$$

Interpretation (qualitative): - Both 1.2344 and 1.2343 have moderate-to-high $CE_{IIW}$ and $P_{cm}$ relative to mild steels; calculated values often indicate a requirement for preheat, controlled interpass temperatures, and post-weld heat treatment (PWHT) to avoid cracking. - 1.2344 usually results in a slightly higher CE/Pcm due to higher Mo/V, lowering weldability marginally compared to 1.2343. - Recommendations: use low-hydrogen procedures, preheat and maintain interpass temps to reduce HAZ hardness, and perform PWHT or tempering of welds to restore toughness.

6. Corrosion and Surface Protection

• Neither 1.2344 nor 1.2343 is stainless; corrosion resistance is moderate due to chromium content (~5%). For most hot-work tooling, surface oxidation and scaling at elevated temperatures are concerns.
• Typical protection: controlled atmospheres (during heat treatment and service where possible), surface hardfacing for localized wear areas, coatings (PVD/CVD for wear resistance), plating (nickel, when appropriate), paint or oxide-suppression coatings for storage, and regular maintenance.
• PREN (pitting resistance equivalent number) is not appropriate for these non-stainless tool steels. For stainless alloys PREN is:
  $$\text{PREN} = \text{Cr} + 3.3 \times \text{Mo} + 16 \times \text{N}$$ — this index does not apply to 1.2344/1.2343 tool steels.

7. Fabrication, Machinability, and Formability

• Machining: Both grades are best machined in the annealed condition. 1.2344, with higher vanadium content, typically shows slightly lower machinability because hard vanadium carbides accelerate tool wear; carbide tooling and rigid setups recommended.
• Grinding and finishing: Both can be ground effectively; 1.2344 may require more frequent dressing due to hard carbides.
• Forming/bending: These are tool steels—cold forming of hardened material is limited. Wherever forming is required, perform operations in annealed condition and plan heat treatment after forming.
• EDM & surface treatments: EDM is commonly used for complex shapes; post-EDM heat treatment or surface grinding may be needed to remove recast layer and restore desired properties.

8. Typical Applications

Table — representative applications and selection rationale.

1.2344 (H13-type) uses	1.2343 (H11-type) uses
Hot-work dies for die casting (aluminum, zinc)	Hot forging dies where toughness is key
Hot extrusion tooling	Hot stamping dies with emphasis on shock resistance
Forging and hot-shear blades	Components where machining and cost are prioritized
Tools exposed to intense thermal cycling and hot wear	Die blocks and tooling in less severe thermal cycles

Selection rationale: - Choose 1.2344 when elevated hot strength, resistance to softening at high service temperature, and wear resistance under thermal cycling are critical. - Choose 1.2343 when slightly greater toughness, ease of machining, and lower alloying cost are beneficial for the application.

9. Cost and Availability

• Both grades are standard European tool steels and readily available in bars, blocks, plate, and forged blanks from major suppliers.
• Relative cost: 1.2344 typically commands a slight premium over 1.2343 because of higher Mo/V content and associated production cost. Availability by product form is usually good for both, but custom sizes and premium cleanliness (vacuum treatment, ESR) will increase lead time and price.
• Procurement tip: request mill certificates for chemistry and hardness, and specify required heat treatment or delivery condition (annealed, normalized, hardened & tempered) to align vendor offers with application needs.

10. Summary and Recommendation

Summary table — relative attributes (High / Medium / Low).

Attribute	1.2344 (H13-type)	1.2343 (H11-type)
Weldability	Medium (requires preheat/PWHT)	Slightly better (but still requires care)
Strength–Toughness balance	Higher hot strength and wear resistance; moderate toughness	Better notch toughness and ductility at similar hardness
Cost	Medium–High	Medium

Conclude with actionable recommendations: - Choose 1.2344 (H13-type) if: your tooling faces severe thermal cycling, elevated service temperatures, or abrasive hot wear and you need higher hardenability and hot hardness retention. Typical: die-casting dies, extrusion tooling, high-temperature forging dies. - Choose 1.2343 (H11-type) if: your primary needs are improved impact toughness, easier machining/processing, and a lower-cost alternative for hot-work tooling used in less severe thermal conditions or where component geometry presents high notch sensitivity.

Final note: Both grades are proven hot-work tool steels. The best choice depends on the combination of section size, expected service temperature, load type (static vs. cyclic, abrasive vs. impact), and the manufacturing route (forging vs. machining vs. additive). Specify required heat treatment windows, preheat/weld procedures, and desired toughness/hardness targets in procurement documents to ensure material and processing deliver the intended in-service performance.