2Cr13 Tool Steel: A Comprehensive Overview

2Cr13 tool steel is a versatile material widely used in manufacturing plastic molds, especially those that require a balance of strength, toughness, and corrosion resistance. As a low-carbon martensitic stainless steel, it is typically employed after quenching and tempering. This heat treatment enhances its mechanical properties, making it suitable for demanding applications.

One of the key advantages of 2Cr13 steel is its good machinability, which allows for efficient processing and shaping. After heat treatment, it exhibits excellent corrosion resistance, ensuring longevity even in harsh environments. Additionally, it offers a good combination of strength and toughness, making it reliable under various loads.

While its corrosion and heat resistance are slightly inferior to those of 1Cr13 steel, 2Cr13 maintains stable oxidation resistance in air up to 700℃. This makes it suitable for applications involving moderate heat exposure. However, it’s worth noting that its weldability and plasticity in the annealed state are not as favorable as those of 1Cr13 steel. Despite this, 2Cr13 steel is known for its excellent polishing properties, which is a significant advantage in mold making where surface finish is critical.

1. Chemical Composition of 2Cr13 tool steel

The chemical composition of 2Cr13 steel is standardized according to GB/T 1220—2007. The typical mass fractions of its key elements are:

• Carbon (C): 0.16% – 0.25% (commonly around 0.16%)
• Silicon (Si): ≤1.00% (often ≤0.60%)
• Manganese (Mn): ≤1.00% (often ≤0.80%)
• Chromium (Cr): 12.00% – 14.00%
• Sulfur (S): ≤0.030%
• Phosphorus (P): ≤0.040% (sometimes specified as ≤0.035%)

These elements contribute to the steel’s unique properties, with chromium being the primary alloying element that imparts corrosion resistance.

2. 2Cr13 tool steel is equivalent to several other standards:

• German DIN: Material number 1.4021, grade X20Cr13
• British BS: Grade S62
• British EN: Grades 56B/56C
• French AFNOR: Grade Z20C13
• Unified Digital Code: S45830

This cross-referencing can be helpful for global customers who are familiar with different standardization systems.

3. Physical Properties of 2Cr13 tool steel

Understanding the physical properties of 2Cr13 steel is crucial for its application in various engineering contexts. Here are the key physical characteristics:

• Melting Point: 1450 – 1510℃
• Density: 7.75 t/m³
• Specific Heat Capacity (cₚ): 459.8 J/(kg·K)

These properties influence how the steel behaves during processing and in service.

Critical Temperatures:

• Aa₁: Approximately 820℃
• Aa₃: Approximately 950℃
• Ac₁: Approximately 780℃

These temperatures are important for heat treatment processes, as they define the steel’s phase transformations.

Elastic Modulus (E): The stiffness of 2Cr13 steel decreases with temperature:

• At 20℃: 210 – 223 GPa
• At 400℃: 193 GPa
• At 500℃: 184 GPa
• At 600℃: 172 GPa

Linear Expansion Coefficient (α): This measures how much the steel expands when heated:

• 20-100℃: 10.5 ×10⁻⁶ ℃⁻¹
• 20-200℃: 11.0 ×10⁻⁶ ℃⁻¹
• 20-300℃: 11.5 ×10⁻⁶ ℃⁻¹
• 20-400℃: 12.0 ×10⁻⁶ ℃⁻¹
• 20-500℃: 12.0 ×10⁻⁶ ℃⁻¹

Thermal Conductivity (λ): Indicates how well the steel conducts heat:

• 20-100℃: 23.0 W/(m·K)
• 20-200℃: 23.4 W/(m·K)
• 20-300℃: 24.7 W/(m·K)
• 20-400℃: 25.5 W/(m·K)
• 20-500℃: 26.3 W/(m·K)

Electrical Resistivity (ρ): Affects the steel’s behavior in electrical applications:

• At 20℃: 0.55 ×10⁻⁷ Ω·m
• At 100℃: 0.65 ×10⁻⁷ Ω·m

These properties are essential for designers and engineers to consider when selecting 2Cr13 steel for specific applications, especially those involving temperature variations or electrical components.

4. Heat Treatment of 2Cr13 tool steel

Proper heat treatment is essential to unlock the full potential of 2Cr13 steel. The following processes are commonly used:

4.1 Forging

• Heating: Slowly heat the steel before reaching 850℃, with the furnace loaded at ≤800℃.
• Forging Temperature: Start forging at 1160-1200℃ and finish at ≥850℃.
• Cooling: After forging, cool in sand or immediately anneal. Due to poor thermal conductivity, heating below 850℃ should be gradual.
• Post-Forging: Slowly cool forged parts and temper immediately.

4.2 Softening Treatment

To reduce hardness for machining:

• High-Temperature Tempering: 750-800℃
• Alternative Method: Hold at 875-900℃ for 1-2 hours, then cool at 15-20℃/h to below 600℃, followed by air cooling. This achieves a hardness of 170-200 HB.

The resulting structure is chromium-rich ferrite with (Cr, Fe)₂₃C₆ carbides.

4.3 Quenching

• Temperature: Typically around 1050℃.
• Cooling: For small molds, air cooling is possible to minimize deformation. Larger molds are usually oil-quenched.

4.4 Tempering

2Cr13 steel is often used in two tempered conditions:

• For High Hardness and Corrosion Resistance: Temper at 200-350℃.
• For Balanced Strength, Plasticity, and Toughness: Temper at 650-750℃.

Note: Avoid tempering between 400-600℃ to prevent undesirable properties.

4.5 Recommended Quenching and Tempering

• Quenching: Oil quench from 980-1000℃.
• Tempering: Varies based on desired properties.

4.6 Stress-Relieving Annealing

• Temper at 730-780℃ followed by air cooling.
• After welding, temper to relieve stress. Slow cooling at high temperatures can lead to bainite formation.

4.7 Pre-Hardening Heat Treatment

• Heat to 860-900℃ and furnace cool to achieve 160-187 HBW.

4.8 Standard Quenching and Tempering

• Quenching: Heat to 1000-1050℃, then oil or water cool to ≥45 HRC.
• Tempering: At 660-670℃ with air cooling to 20-23 HRC.

These heat treatment processes allow for tailoring the steel’s properties to specific application requirements, ensuring optimal performance in various scenarios.

5. Mechanical Properties of 2Cr13 Steel

The mechanical properties of 2Cr13 steel depend highly on the heat treatment it undergoes. Below are the typical properties achieved through different processes:

5.1 After Quenching and Tempering

For samples quenched from 980-1000℃, oil-cooled, and then tempered:

• Yield Strength (Rp0.2): ≥440 MPa
• Tensile Strength (Rm): ≥640 MPa
• Elongation (A): ≥20%
• Reduction of Area (Z): ≥50%
• Impact Energy (Ku₂): ≥63 J
• Hardness (HBW): 192-223

5.2 Annealed Condition

For annealed martensitic stainless steel cold-rolled sheets and strips:

• Yield Strength (Rp0.2): ≥225 MPa
• Tensile Strength (Rm): ≥520 MPa
• Elongation (A): ≥18%
• Cold Bending (180°): d = 2a
• Hardness (HBW): ≤223

5.3 High-Temperature Properties

After quenching at 1000-1020℃, oil cooling, and tempering at 720-750℃, the steel exhibits the following properties at elevated temperatures:

Test Temp (∘C)	Tensile (Rm​, MPa)	Yield (Rp0.2​, MPa)	Elongation (δ, %)	Red. Area (ψ, %)	Impact (αk​, J/cm2)
20	720	520	21.0	68.0	65-175
300	555	400	18.0	66.0	120
400	530	405	16.5	58.5	205
450	495	380	17.5	61.0	–
500	495	420	22.5	66.0	–
550	440	365	32.5	72.5	–

These properties demonstrate the steel’s ability to maintain strength and ductility at higher temperatures, making it suitable for heat exposure applications.

6. Applications of 2Cr13 Steel

Due to its balanced properties, 2Cr13 steel is a popular choice for various applications. It is particularly well-suited for:

• Plastic Molds: Especially those under high loads and corrosive environments, including molds for transparent plastic products.
• High-Stress Components: Such as turbine blades, hot oil pump shafts and sleeves, impellers, and hydraulic press valve plates.
• Industrial and Consumer Goods: These include applications in the paper industry, medical equipment, and household items like knives and cutlery.

Additionally, 2Cr13 steel can be used as a substitute for Cr12 type steel in manufacturing punching and drawing dies. When treated with carburizing, quenching, and tempering, it can achieve a surface hardness of 62-65 HRC and a core hardness of 38-41 HRC, potentially extending the service life of molds by 1-2 times compared to traditional Cr12 steel treatments.

7. Comparison to Other Steels

Understanding how 2Cr13 steel compares to similar materials can help in selecting the right steel for specific needs:

• Vs. 1Cr13 Steel: 2Cr13 offers higher strength and hardness after quenching and tempering, but has slightly lower corrosion and heat resistance. Its weldability and plasticity in the annealed state are also inferior.
• Vs. 30Cr13 Steel: 30Cr13 has even higher strength, hardness, and hardenability than 2Cr13 (20Cr13) and 12Cr13 steels after quenching. It provides some corrosion resistance to dilute nitric acid and weak organic acids at room temperature, though less than 12Cr13 and 20Cr13.
• Vs. 4Cr13 Steel: 4Cr13 has higher strength and hardness than 30Cr13 but lower toughness and corrosion resistance, with poorer weldability.
• Vs. 20Cr13 Steel: 20Cr13 has properties similar to 12Cr13 but with slightly higher strength, hardness, and lower toughness and corrosion resistance.

These comparisons highlight the trade-offs between different properties, allowing engineers to choose the most appropriate steel based on their application’s specific requirements.