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

Introduction

Engineers, procurement managers, and manufacturing planners frequently face the choice between two closely related German hot‑work tool steels when specifying dies and tooling: 1.2343 and 1.2344. The decision commonly balances hot‑strength and wear resistance against toughness, weldability, and cost. Typical decision contexts include selecting a steel for high‑temperature forming dies (where hot hardness and temper resistance matter) or for tooling exposed to thermal shock (where toughness and resistance to cracking are critical).

The primary practical distinction is that 1.2344 is formulated to provide somewhat higher hardenability, hot strength, and wear resistance, while 1.2343 trades a little of that peak hot hardness for improved toughness and slightly easier heat‑treat and repair characteristics. Because both are German designation hot‑work grades, they are often directly compared for die casting, forging, extrusion, and other hot‑work applications.

1. Standards and Designations

• EN (European): 1.2343 and 1.2344 (commonly used EN numeric designations for hot‑work tool steels)
• Common trade/AISI names: These steels correspond to the family of hot‑work H‑series tool steels; 1.2344 is widely referenced as the H13 equivalent in many international catalogs; 1.2343 maps to a closely related hot‑work grade (often compared to H11 in discussions).
• Other standards: JIS, GB, and ASTM provide their own equivalents or near‑equivalents; product forms (bar, plate, forgings, prehardened blocks) follow supplier specifications.
• Classification: Both are hot‑work tool steels (air‑hardening/hardenable alloy tool steels), not stainless steels, not HSLA, and used where elevated temperature strength and resistance to tempering are required.

2. Chemical Composition and Alloying Strategy

The following table shows typical composition ranges quoted by material standards and major suppliers. Actual chemistries vary by mill heat and specification; treat values as representative ranges used for selecting alloying strategy rather than absolute guaranteed minima/maxima.

Element	1.2343 (typical wt%)	1.2344 (typical wt%)
C	0.32 – 0.40	0.32 – 0.45
Mn	0.30 – 0.60	0.30 – 0.60
Si	0.80 – 1.20	0.80 – 1.20
P	≤ 0.03	≤ 0.03
S	≤ 0.03	≤ 0.03
Cr	4.00 – 5.00	4.75 – 5.50
Ni	≤ 0.30	≤ 0.30
Mo	0.80 – 1.25	1.10 – 1.75
V	0.70 – 1.00	0.80 – 1.20
Nb	trace	trace
Ti	trace	trace
B	trace	trace
N	trace	trace

How the alloying strategy affects properties: - Carbon: sets martensite hardness potential and contributes to wear resistance; higher carbon aids hardness but reduces weldability and toughness. - Chromium: improves hardenability, red hardness (hot hardness), and oxidation resistance at elevated temperatures. - Molybdenum and Vanadium: form stable carbides that increase secondary hardening, temper resistance, and wear resistance at hot‑work temperatures; they also enhance hardenability. - Silicon and Manganese: deoxidation and strength adjustments; impact tempering behavior. - Minor microalloying (Nb, Ti, B): when present in trace amounts can refine grain, influence hardenability, or aid toughness; often not present in significant quantities for these classic hot‑work steels.

3. Microstructure and Heat Treatment Response

Typical microstructure and response: - Both grades are martensitic tool steels with dispersed alloy carbides (Cr‑, Mo‑, V‑rich carbides). In the as‑quenched condition they present a tempered martensitic matrix with carbide network. - 1.2344, with its generally higher Cr and Mo (and sometimes slightly higher C), displays greater hardenability and a higher fraction of alloy carbides capable of delivering stronger secondary hardening upon tempering. That yields superior hot hardness and resistance to softening at elevated temperatures. - 1.2343 tends toward a slightly tougher tempered martensitic matrix with fewer hard alloy carbides relative to 1.2344, which can translate to improved resistance to crack initiation under thermal fatigue.

Heat treatment routes and effects: - Normalizing: both steels are commonly normalized to refine grain and homogenize prior to hardening; this reduces segregation and improves toughness. - Quenching: air or oil quenching from austenitizing temperature is typical; the higher alloy content of 1.2344 supports air hardening with good hardenability. Quench media and cooling rate influence retained austenite and distortion. - Tempering: multiple tempering cycles are used to reach stable tempered martensite and secondary hardening. 1.2344 benefits more from secondary hardening peaks due to Mo and V carbides, providing superior temper resistance at higher tempering temperatures. - Thermo‑mechanical processing: forging or controlled rolling followed by appropriate heat treatment can improve toughness via grain refinement for both grades.

4. Mechanical Properties

The following table gives typical property ranges for quenched and tempered conditions (actual values depend strongly on specific heat treatment and tempering temperature). Use these as design guidance rather than guaranteed supplier data.

Property	1.2343 (typical)	1.2344 (typical)
Tensile strength (MPa)	900 – 1,200	1,000 – 1,300
Yield strength (MPa)	700 – 950	800 – 1,050
Elongation (%)	8 – 14	7 – 12
Impact toughness (J, Charpy)	relatively higher	moderate to high
Hardness (HRC, quenched & tempered)	42 – 52	44 – 54

Interpretation: - 1.2344 typically achieves higher tensile and yield strengths and peak hardness after appropriate heat treatment because of its higher alloy content and stronger carbide population. - 1.2343 commonly offers marginally better ductility and impact toughness at equivalent hardness levels, making it slightly less prone to brittle fracture under cyclic thermal loading or shock. - Designers choose 1.2344 for applications demanding higher hot hardness and wear resistance; they choose 1.2343 where toughness and resistance to crack propagation are the priority.

5. Weldability

Weldability depends on carbon equivalent and microalloying. For qualitative assessment engineers use indices such as the IIW Carbon Equivalent and Pcm. Representative formulas:

$$CE_{IIW} = C + \frac{Mn}{6} + \frac{Cr+Mo+V}{5} + \frac{Ni+Cu}{15}$$

$$P_{cm} = C + \frac{Si}{30} + \frac{Mn+Cu}{20} + \frac{Cr+Mo+V}{10} + \frac{Ni}{40} + \frac{Nb}{50} + \frac{Ti}{30} + \frac{B}{1000}$$

Qualitative interpretation: - Both 1.2343 and 1.2344 have moderate carbon and significant alloying, giving moderate‑to‑elevated carbon equivalents. This requires controlled preheat, interpass temperature control, and post‑weld heat treatment (PWHT) to avoid hydrogen‑assisted cracking and to re‑temper hardened zones. - 1.2344 generally exhibits slightly higher CE/PCM values owing to higher Cr/Mo/V; therefore it is marginally more challenging to weld and repair than 1.2343. Preheating and slow cooling are especially important for 1.2344 to avoid cracking. - Recommended practice: use low hydrogen consumables, adequate preheat (supplier and weld procedure dependent), and perform PWHT to restore temper and relieve residual stresses.

6. Corrosion and Surface Protection

• Neither 1.2343 nor 1.2344 are stainless steels; they lack the chromium content (>10.5–11%) required for corrosion resistance in service. Corrosion protection strategies are therefore required for environments where oxidation or chemical attack is relevant.
• Typical protections: coating (electroplating, hard chrome where compatible with temperature), paint systems, oil/grease, or physical barriers; for high‑temperature oxidation control, surface treatments such as nitriding (where applicable) or thermal barrier coatings may be considered.
• PREN (Pitting Resistance Equivalent Number) is not applicable to these low‑Cr hot‑work steels because they are not stainless grades; therefore the PREN formula is not relevant:

$$\text{PREN} = \text{Cr} + 3.3 \times \text{Mo} + 16 \times \text{N}$$

Use such indices only for austenitic stainless alloys.

7. Fabrication, Machinability, and Formability

• Machinability: Both grades machine similarly in annealed condition; machinability decreases significantly after hardening. 1.2344, with slightly higher alloy and hardness potential, can be more abrasive on tooling and may require carbide tooling or coated inserts.
• Formability and bending: These are not sheet forming steels; for any cold forming the steel should be supplied in appropriate soft/annealed condition. After hardening, forming is not feasible.
• Surface finishing: Both accept grinding, EDM and conventional finishing operations. EDM is common for complex cavities; attention to cracking and local heat input is essential.
• Repair: 1.2343 is typically easier to grind and weld repair than 1.2344; however, both require preheat and PWHT when welding.

8. Typical Applications

Application type	1.2343 (typical uses)	1.2344 (typical uses)
Hot forging dies	Lower to medium duty hot forging dies where higher toughness is valued	Heavy‑duty forging dies requiring higher hot hardness and wear resistance
Die casting tooling	Inserts subject to thermal cycling but where crack resistance is important	Core pins, die inserts with high thermal and abrasive wear
Extrusion tooling	Tools for extrusion where moderate hot strength and toughness needed	Extrusion dies operating at higher temperatures/pressures
Hot work tooling (general)	Press tools, trim dies subject to shock	High temperature plungers, ejector pins, dies needing temper resistance
Repairable tooling	Preferred where weldability and in‑field repairs are frequent	Used where wear performance justifies more careful repair procedures

Selection rationale: - Choose 1.2344 for higher service temperatures, applications with severe abrasive wear, or when maintaining hardness at elevated tempering temperatures is critical. - Choose 1.2343 when thermal fatigue, crack resistance, and ease of repair are higher priorities.

9. Cost and Availability

• Cost: 1.2344 (H13‑type) is one of the most ubiquitous hot‑work tool steels globally; it is often available at comparable or slightly higher cost than 1.2343 because of demand and processing. Higher alloy content in 1.2344 can marginally increase material cost.
• Availability: 1.2344 has excellent availability in many product forms (round bar, plate, prehardened blocks, forgings). 1.2343 is also widely available but sometimes more common in specific applications or regional supply chains.
• Product forms: Both are sold in annealed and pre‑hardened conditions; lead times depend on size, finish, and supplier inventory.

10. Summary and Recommendation

Criterion	1.2343	1.2344
Weldability (qualitative)	Better (easier repairs)	Slightly more challenging
Strength–Toughness balance	Tougher, slightly more ductile	Higher strength and hot hardness
Cost (typical)	Competitive	Comparable to slightly higher
Availability	Good	Excellent, widely stocked

Choose 1.2343 if: - Your tooling is exposed to frequent thermal cycling or shock and crack resistance and easier field repairability are priorities. - You need a balanced combination of toughness and hot‑work performance with somewhat simpler welding/repair requirements. - Slightly lower peak hot hardness is acceptable in return for improved fracture resistance.

Choose 1.2344 if: - The application demands higher hardenability, sustained hot hardness, and superior wear resistance at elevated tempering temperatures. - You are designing for high thermal and abrasive stresses (heavy forging dies, demanding die casting cores, high‑temperature extrusion). - You can accommodate stricter welding procedures, preheating, and PWHT for repair and joinery.

Final note: Both 1.2343 and 1.2344 are proven hot‑work tool steels; selection should be confirmed with supplier datasheets, specific heat‑treat schedules, and prototype testing under representative service conditions to validate hardness, toughness, and life for the intended application.