Forging and Heat Treatment Technology of ISO 41Cr4 Cold Work Tool Steel

International Equivalent Standards for 41Cr4 Steel

ISO 41Cr4 cold work tool steel is equivalent to:

• China (GB): 40Cr

• Germany (DIN): 1.17035 / 1.7045, 41Cr4 / 42Gr4

• UK (EN & BS): 18, 41Cr4

• France (AFNOR & NF): 42C4, 38Cr4 / 41Cr4

• Italy (UNI): 41Cr4

• Belgium (NBN): 42Cr4

• Sweden (SS): 2245

• USA (AISI/SAE/ASTM): 5140

• Japan (JIS): SCr440(H) / SCr440

Importance of Forging and Heat Treatment in Cold Work Tool Steel

To meet the performance requirements of cold work molds, the ideal microstructure should consist of a high-hardness, high-toughness matrix with uniformly dispersed fine carbide particles. This requires optimized forging and heat treatment processes.

Forging Process for Cold Work Tool Steel

1. Forging High-Carbon, High-Alloy Steels

High-carbon, high-alloy steels have low thermal conductivity, low plasticity, and high deformation resistance. The narrow forging temperature range (~200°C) makes them prone to internal stress and cracking. Key forging guidelines include:

1. Slow and uniform heating & cooling – Large billets require preheating, frequent flipping during heating, and cooling in dry sand after forging.

2. Strict temperature control – If the temperature falls below the forging limit, immediately reheat before further hammering. Final forging temperature should not exceed 1000°C to prevent coarse grain formation.

3. Preheating forging tools – Tools should have large fillet radii, smooth surfaces, and be preheated to 200~300°C.

4. Controlled hammering technique – Use the "light-heavy-light" method with uniform temperature and deformation to reduce internal stress.

5. Avoid unnecessary punching – If punching is required, use a punch with a small taper and heat the center before penetrating from the opposite side.

To ensure high-quality forging, different forging techniques should be used depending on the mold type:

• Axial upsetting – For small molds like punches, rolling dies, and circular shears.

• Radial upsetting – For molds with working sections in the center, such as cold heading dies.

• Cross or three-directional upsetting – For molds with high internal and external quality demands, like blanking and deep drawing dies.

Forging Ratio Guidelines

• A total forging ratio of 8~10 is recommended, with each upsetting step having a forging ratio of ~2.

• If the forging ratio is 2~5, a fibrous structure is formed, leading to anisotropic mechanical properties.

• When the ratio exceeds 5, mechanical properties do not improve, but anisotropy increases.

• Proper hammer tonnage selection is essential to ensure deep penetration forging without cracking.

2. Forging Cemented Carbide Tool Steel

Cemented carbide tool steel is difficult to forge and requires spheroidizing annealing before forging to eliminate residual stress and obtain spherical pearlite. Key forging considerations:

1. Preheat tools and dies before use.

2. Slow heating and uniform soaking – Flip billets frequently in the furnace to ensure even heating.

3. Pre-cooling before forging – Let the billet cool ~50°C before forging to reduce cracking risk. Final forging temperature should be around 900°C.

4. Gradual shape changes – Initial forging involves upsetting and drawing-out in V-shaped anvils or dies, followed by gradual shape adjustments.

Heat Treatment Technology for Cold Work Tool Steel

1. Quenching Process

1. Optimized quenching temperature – Ensures sufficient dissolution of carbon and alloy elements, guaranteeing hardenability, strength, and wear resistance.

2. Controlled soaking time – Heating time should be based on the formula t = αD (where α is the heating coefficient).

3. Proper cooling medium selection:

• High-alloy tool steel – Air cooling, oil quenching, or salt bath quenching.

• Carbon & low-alloy tool steel – Dual-medium quenching (e.g., water-to-oil, brine-to-oil) to reduce deformation and cracking.

• Advanced quenching media – Zinc chloride-alkali solution, calcium chloride solution, and ternary nitrate solutions for precise control.

4. Protective quenching methods:

• Packing method (sealing in a container)

• Coating protection (anti-oxidation coatings)

• Vacuum & salt bath heating to prevent decarburization

2. Strengthening & Toughening Treatments

Cold work tool steel undergoes low quenching, high quenching, microstructure refinement, isothermal & graded quenching, including:

(1) Low-Temperature Quenching

• Quenching below the traditional temperature can improve toughness and fatigue resistance, reducing brittle fracture risks.

• Effective for carbon tool steel, alloy tool steel, and high-speed steel.

(2) High-Temperature Quenching

• Enhances hardened layer depth for low-hardenability steels.

• Example: T7-T10A steel (Ø25~50mm) quenching temperature increases to 830~860°C, improving service life.

• GCr15 (Cr2) steel: Quenching temp 860 → 900~920°C, doubling service life.

• Impact-resistant tool steels (e.g., 60Si2Mn at 920~950°C, Cr-W steels at 950~980°C) show higher fracture toughness & wear resistance.

(3) Microstructure Refinement

• Refined matrix structure → Improved strength & toughness.

• Refined carbides → Enhances wear resistance & toughness simultaneously.

Why Choose 41Cr4 Steel for Cold Work Tooling?

1. Excellent wear resistance – Ensures long-lasting tool performance.

2. Superior toughness – Reduces risk of cracking and premature failure.

3. Good machinability – Facilitates precise cutting & shaping.

4. Versatile heat treatment properties – Allows customization for different applications.

5. Wide international availability – Complies with global standards like ISO, DIN, ASTM, JIS, GB.

Common Applications

Cold work dies & molds
Shearing & cutting tools
Punching & stamping dies
Rolling & drawing dies
High-strength wear-resistant components

EATHU – Recommended High-Quality Forging Factory

If you are looking for a reliable supplier of 41Cr4 tool steel forging and processing, EATHU is your ideal choice!