K340 Steel | DC53 | ASSAB 88 | Cr8Mo2VSi

K340 steel is premium 8% chromium cold work tool steel made by electro‑slag remelting (ESR). Its nominal composition: 1.10% C, 8.20–8.30% Cr, 2.10% Mo, 0.50% V, plus minor aluminum and niobium. It combines great toughness, adhesive wear resistance and high compressive strength. Compared with conventional 12% chromium steel 1.2379 (D2), K340 features much better toughness, hardening performance and anti-adhesive wear, ideal for tough cold work applications beyond standard grades.

ESR refining creates finer, uniformly distributed carbides. This gives K340 material high grindability, stable dimensions during heat treatment and good EDM machinability with lower stress cracking risk. It supports nitriding, PVD coating and vacuum hardening. Based on regional standards, its equivalent grades are DC53 (Japan), ASSAB 88 (Sweden), Cr8Mo2VSi (China), modified A8 (USA).

Supply Range of K340 Steel

1. Round Bar

Hot Rolled / Forged: Diameter Φ10mm – Φ500mm
Forged: Diameter Φ50mm – Φ400mm (larger sizes available upon request)
Length: 2000mm – 5800mm (customizable)
Tolerances: Compliant with DIN EN ISO 4957 or ASTM A681
Surface conditions: Black skin, peeled, turned, or ground finish

Flat Bar / Plate

3. Forgings / Custom Shapes of K340 Steel

Keyspark Steel offers precision plate component machining of K340 material, specializing in steel plate milling and precision hole finishing. Custom-made to your drawings.

We also provide our overseas customers with assembly services for various CNC machined parts.

Our team does rough and fine machining for all kinds of forging ring parts. We provided rough turning service like slewing bearing rings and gear rings to many European construction machinery partners. Keyspark Steel have strong custom ability and an engineer teams. We make products from your drawings and are very flexible.

Keyspark Steel also offers importing clients custom cold drawn steel round bars, steel square bars and hexagon steel bars in different sizes with cold drawing dies as supporting items. The material have tight tolerance, smooth surface and stable material performance. And also cold drawing dies as supporting items.

K340 Equivalent

Standard System	Country/Region	Equivalent Grade	Common Search Terms
/	Europe	K340	K340 steel, K340 tool steel, K340 cold work steel
JIS	Japan	DC53	DC53 steel, DC53 material, DC53 tool steel, DC53 steel material, JIS DC53
/	Sweden	ASSAB 88	ASSAB 88 steel, 88 tool steel
GB	China	Cr8Mo2VSi	Cr8Mo2VSi steel, Cr8Mo2VSi tool steel
AISI / ASTM	USA	A8 modified	A8 modified tool steel
DIN / EN	Germany	1.2379 modified	1.2379 modified steel

K340 Composition

Element	C	Si	Mn	P	S	Cr	Mo	V
Content	1.10	0.70	0.40	≤0.030	≤0.030	8.20–8.30	2.10	0.50

The 8% chromium content combined with molybdenum and vanadium in K340 tool steel provides an optimal balance of wear resistance and toughness.

K340 Properties

MECHANICAL PROPERTY	METRIC VALUE	IMPERIAL VALUE
Hardness (Annealed)	≤ 235 HB	≤ 235 HB
Hardness (Quenched & Tempered)	58 – 62 HRC	58 – 62 HRC
Tensile Strength (σb)	≥ 2400 MPa	≥ 348 ksi
Yield Strength (σ0.2)	≥ 2000 MPa	≥ 290 ksi
Impact Toughness (KV, 20°C, Longitudinal)	≥ 24 J/cm²	≥ 114.2 ft·lb/in²

K340 offers an excellent combination of toughness, compressive strength, wear resistance, and dimensional stability. The steel is typically supplied in the annealed condition with a maximum hardness of 235 HB. After hardening at 1020–1040°C and tempering at 520–560°C, it achieves a working hardness of 58–62 HRC. The tensile strength, yield strength, and impact toughness values are typical for the hardened and tempered condition. Unit conversions: 1 MPa ≈ 0.145 ksi; 1 J/cm² ≈ 4.76 ft·lb/in².

Delivery Condition of K340 Steel

Black Surface, Bright Surface, Turned Surface, Grinded Surface, Poblished surface.

K340 Material Application

K340 steel is the go‑to cold work tool steel for applications demanding high toughness combined with excellent adhesive wear resistance. Its versatility extends across a broad range of industries:

Blanking & Stamping: Fine blanking, stamping, punching dies, pill punching dies, especially for stainless steel and coin minting.
Cold Forming: Cold forming tools, deep drawing dies, extrusion tools, bending tools.
Cutting & Shearing: Industrial knives, machine knives, shear blades, thread rolling tools.
Coining & Embossing: Coining tools, embossing dies, minting dies.
Powder Pressing: Powder pressing dies and tooling.
Screws & Barrels: Screws and barrels for plastics processing.
Rolls & Wear Parts: Rolls, wear parts, components for recycling industry.
General Mechanical Engineering: Guide rails, machine components, components for equipment below ground.
Glass Fibre Reinforced Plastics: Molds and tooling for glass fibre reinforced plastic processing.

K340 Steel Heat Treatment & Processing

Heat Treatment

Soft Annealing: Heat to 710–740°C, hold adequately, then cool slowly in furnace at 10–20°C per hour. Resulting hardness ≤235 HB, optimized for batch machining.
Stress Relieving: Heat to approximately 650°C in a neutral atmosphere, hold for 1–2 hours, then slow cool. Recommended after rough machining to minimize distortion.
Preheating: Preheat in stages: 400°C, 600°C, and 800°C for approximately 20 minutes each, to avoid thermal shock.
Austenitizing (Heating): 1040–1080°C. Soak time: 30 minutes after temperature equalization. Protect against oxidation and decarburization.
Quenching (Cooling): Oil quench or salt bath quench at 250°C. Vacuum hardening is well suited for K340 material. Quench to 50–70°C, then temper immediately.
Tempering: Triple tempering is recommended for optimal toughness and dimensional stability. Temper at 500–580°C. DC53 tool steel exhibits a secondary hardening peak, with hardness increasing up to approximately 520°C before declining.

Tempering Temp	500°C	520°C	550°C	580°C
Hardness (HRC)	62	63–64	59–60	56–58

For maximum hardness and wear resistance in blanking and stamping tools, triple temper at 520°C (63–64 HRC). For improved toughness in heavy‑duty forming tools, triple temper at 550–580°C (56–60 HRC).

Processing Guide:

Forging: Heat uniformly to 1050–1100°C. Start forging at 1050°C, finish above 850°C. After forging, cool slowly in furnace or insulating media, then anneal.
Machining: Annealed K340 tool steel (≤235 HB) offers very good machinability due to its homogeneous ESR structure. Carbide tools recommended for batch production. Hardened parts require grinding with CBN wheels.
EDM (Electrical Discharge Machining): DC53 material features outstanding EDM machinability with reduced risk of stress cracking. Remove the recast layer after EDM and perform stress relief at 500–550°C.
Nitriding: K340 material is very well suited to salt‑bath, gas, and plasma nitriding. Surface hardness of 1000+ HV achievable for enhanced wear resistance.
PVD Coating: K340 steel can be PVD coated well for further wear resistance improvement.
Polishing: This grade offers good polishability for most tooling applications.
Welding: Not recommended for highly stressed tooling components. If necessary, preheat and perform post‑weld heat treatment.

Quality Control of K340 Tool Steel

Full-process control:

Raw material and manufacturer control
Test : Chemical composition, mechanical properties, UT(ultrasonic testing), specification, surface condition, straightness, etc.
Packing: Wooden case or pallet or VCI plastic film

Why Purchase K340 Steel from Keyspark Steel?

Fully Customizable: Dimensions, heat treatment, and hardness – all adjustable per batch order.
Certified Quality: Each batch comes with MTC certificate (EN 10204 3.1/3.2) , full chemical and mechanical test report.
ESR Option: Premium quality with Electro-Slag Remelting available for critical applications.
Stable Production: Large forging and rolling capacity ensures consistent quality across orders.
Long-Term Supply: Reserved production slots for regular customers – no interruptions.
Neutral Packaging: Oiled, wrapped, and strapped.

FAQ of K340 Steel

Q1: What is K340 steel?

A: K340 steel is an 8% chromium cold work tool steel. It is superhard stamping steel refined by electro-slag remelting (ESR). Typical composition: C 1.10%, Cr 8.30%, Mo 2.10%, V 0.50%. Its hardness ≤255 HB in annealed condition, and reaches HRC 61–63 after heat treatment. Compared with 12% chromium steel such as D2, K340 steel has finer carbides with even distribution, and much better toughness and resistance to adhesive wear.

Q2: Why does K340 steel use 8% chromium instead of 12% chromium in chemical composition?

A: Lower chromium content reduces the formation of large eutectic carbides. 12% chromium steel like D2 has high wear resistance, but large carbides cause low toughness. K340 steel keeps Cr at 8.3%, with 2.1% Mo and 0.5% V. It keeps high wear resistance and gets finer carbides and higher toughness. It fits cold work molds under impact load.

Q3: How to trade off toughness and wear resistance between K340 steel and D2 (1.2379)?

A: K340 tool steel has much better fracture toughness than D2, while their wear resistance is close. When stamping 0.5 mm silicon steel sheet, the cutting edge service life of K340 steel can be 1.8 times that of D2. When D2 (1.2379) cannot work under conditions requiring adhesive wear resistance and high toughness, K340 steel can meet nearly all cold work applications.

Q4: How to pick quenching and tempering temperature for K340 steel heat treatment?

A: Quenching: austenitizing temperature 1040–1080°C. Salt bath, oil, air or vacuum cooling are available. Air cooling or high-pressure gas quenching reduces part deformation. Tempering: select temperature from tempering curve according to target hardness. Low-temperature tempering (150–200°C) gets hardness over HRC 61. High-temperature tempering near 520°C uses secondary hardening. It keeps hardness above HRC 58 and improves red hardness.

Q5: Why is cryogenic treatment good for K340 steel?

A: K340 material has much retained austenite after quenching. Cryogenic treatment at -70 to -80°C helps retained austenite change into martensite. Hardness increases by 1–3 HRC, and hardness variation is kept within ±0.5 HRC. It greatly improves dimensional stability for precision molds.

Q6: Why does K340 steel retain much austenite after quenching?

A: K340 steel has high retained austenite (RA) after quenching. This comes from the combined effect of its chemical elements and heat treatment settings. K340 steel contains about C 1.10%, Cr 8.2%, plus Mo 2.10% and V 0.50%. Carbon, chromium, molybdenum and vanadium are austenite stabilizing elements. They greatly lower martensite finish temperature (Mf). A large amount of austenite cannot turn into martensite when the steel cools to room temperature after quenching.