D2 steel, also known as SKD11 or Hitachi SLD, is a widely used high-carbon, high-chromium tool steel known for its exceptional cutting performance and toughness. Whether you’re a hobbyist or considering outsourcing the heat treating process, understanding the fundamentals of heat treating D2 steel is crucial.
In this blog post, we will provide you with a comprehensive overview of heat treating D2 steel, including its properties, composition, common applications, and step-by-step heat treating processes. Let’s dive in!
What is D2 Steel?
D2 steel is a versatile tool steel primarily used for cutting tools, molds, and dies. It contains 12% chromium, which gives it some corrosion resistance. With its high hardness, good wear resistance, toughness, and excellent dimensional stability, D2 steel has become a popular choice in various industries.
Properties and Composition
D2 steel exhibits several key properties that make it highly desirable for cutting applications. It boasts high hardness, reaching up to 62 HRC, making it suitable for high-wear environments. Additionally, D2 steel offers good wear resistance, corrosion resistance, toughness, and dimensional stability. Its composition typically includes carbon, manganese, chromium, molybdenum, silicon, and vanadium, each contributing to its unique set of properties.
D2 Tool Steel Chemical compositions
Chemical composition of D2 tool steel typically includes the following elements:
- Carbon (C): 1.40-1.60%
- Chromium (Cr): 11.00-13.00%
- Manganese (Mn): 0.60-0.90%
- Silicon (Si): 0.10-0.60%
- Vanadium (V): 0.50-1.10%
- Molybdenum (Mo): 0.70-1.20%
- Phosphorus (P): Maximum 0.030%
- Sulfur (S): Maximum 0.030%
D2 Tool Steel Mecahnical Properties
The typical mechanical properties of D2 tool steel are:
| Mechanical Property | Value |
|---|---|
| Hardness (HRC) | 58-62 |
| Tensile Strength | 1850 MPa |
| Yield Strength | 0.2% offset: 1350 MPa |
| Elongation at Break | 4-8% |
| Modulus of Elasticity | 210 GPa |
| Impact Strength (Charpy V-notch) | 20-30 J/cm² |
| Compressive Strength | 0.2% offset: 2600 MPa |
| Fatigue Strength (Rotating Bending) | 800-1000 MPa |
| Wear Resistance | Excellent |
| Dimensional Stability | Excellent |
Hardness of D2 tool steel
D2 tool steel is renowned for its exceptional hardness, making it a popular choice for various cutting and tooling applications.
When properly heat treated, D2 tool steel typically achieves a hardness of around 58-62 HRC (Rockwell C scale). In terms of the Brinell Hardness Number (BHN), D2 tool steel typically falls within the range of 255-275 BHN. Additionally, on the Vickers Hardness (HV) scale, D2 tool steel typically exhibits a hardness of approximately 710-740 HV.
These high hardness values demonstrate the steel’s ability to withstand wear, retain sharp cutting edges, and resist deformation, making it suitable for demanding applications in industries such as manufacturing, tooling, and metalworking.
D2 Tool Steel Applications
D2 steel finds its applications across a wide range of industries. It is commonly used in the manufacturing of dies for blanking, forming, stamping, thread rolling, and bending. Furthermore, D2 steel is ideal for wear parts, machine parts such as injection screws, and various cutting tools like knives, slitting cutters, shear blades, and tire shredders.
Heat Treating Processes
To optimize the hardness and toughness of D2 steel, a proper heat treating process is essential. Here, we outline the key steps involved in heat treating D2 steel:
- Annealing: Soften the steel for improved workability.
- Heat the steel slowly to 1550°F and ensure even heating.
- Cool the steel slowly in a furnace until it reaches around 1000ºF.
- Allow the steel to cool in the ambient air.
- Stress Relieving: Reduce internal stresses after machining processes.
- Heat the steel slowly to a temperature between 1050°-1250°F.
- Hold the steel at that temperature for 1 hour per inch of thickness.
- Cool the steel either in the furnace or in the ambient air.
- Hardening: Achieve maximum hardness and wear resistance.
- Preheat the steel gradually, either in one step or two steps for complex tools.
- Raise the furnace temperature to 1800°-1850°F and hold the steel at that temperature.
- Remove the workpiece from the furnace and allow it to cool in still air or a vacuum heat treatment furnace.
- Tempering: Reduce internal stresses and achieve desired hardness and toughness.
- Reheat the steel to the desired temperature for two hours, with additional time for thicker sections.
- Cooling should be done in the air to room temperature.
Tips and Best Practices
To ensure successful heat treating of D2 steel, consider the following tips and best practices:
- Follow the recommended preheating guidelines to prevent cracking and distortion.
- Avoid overheating the steel above 1850°F to prevent grain growth.
- If necessary, use an oil quenching method for thick sections to ensure proper cooling.