S7 Tool steel:  Properties, Applications, Heat Treatment

S7 tool steel is a top-quality material recognized for its outstanding strength and resistance to shocks and abrasion. Ideal for tools exposed to high stress and extreme conditions, it’s widely used in industries like die casting, plastic molding, and mining equipment. This article covers everything you need to know about S7 steel—from its chemical composition and physical properties to its heat treatment processes and applications. If you’re looking for a reliable steel solution that stands up to the toughest demands, S7 might be just what you need.

What is S7 Steel?

S7 steel is a high-strength, shock-resistant, air-hardening tool steel, containing 0.50% carbon, 1.00% manganese, 5.25% chromium, and 1.10% molybdenum. It has excellent toughness and impact resistance, commonly used for tools and dies that face heavy wear and shock. After heat treatment, S7 reaches a hardness of 55-60 HRC. This steel is easy to process through forging and air-hardening, making it a great choice for automotive, aerospace, and manufacturing industries.

Is S7 a Good Steel?

Yes, S7 is an excellent steel for high-impact and heavy-duty applications due to its strong toughness, shock resistance, and ability to retain hardness after heat treatment.

S7 Tool Steel Properties

S7 tool steel is tough, wear-resistant, and easy to machine, making it perfect for high-performance tools. Knowing its properties helps you pick the right material for tough jobs.

Chemical Composition of S7 Tool Steel

Here’s the chemical composition of S7 tool steel:

Physical Properties of S7 Tool Steel

Here are the physical properties of S7 tool steel:

Mechanical Properties of S7 Tool Steel

Here are the mechanical properties of S7 tool steel:

S7 Steel Equivalent Grades

The following are approximate equivalent grades for S7 tool steel, which may vary depending on regional standards. These grades provide comparable characteristics and are frequently used as substitutes in different uses.

What Is the Difference Between S7 and D2 Steel?

S7 offers better shock resistance and is ideal for impact-prone tools, while D2 excels in wear resistance and hardness, making it better for cutting and forming tools.

Fabrication of S7 Cold Work Steel

The right fabrication steps are key to get the best performance out of S7 steel. Forging, heat treatment, and machining all play a role in unlocking its full potential for toughness, hardness, and wear resistance. Let’s dive into each process and see how they make a difference.

Forging/Rolling

For forging or rolling S7 steel, heat it to temperatures between 1000°C to 1100°C (1832°F to 2012°F). Maintaining a consistent temperature during the process ensures a fine, uniform grain structure and prevents cracking. Cooling the steel gradually after the process is critical to relieve internal stresses.

Heat Treatment

The heat treatment of S7 steel is essential for optimizing its performance, especially in high-impact applications.

• Annealing: Heat S7 steel to 800°C to 850°C (1472°F to 1562°F), then cool slowly in still air or in a furnace. This procedure relaxes the steel, minimizes internal tensions, and makes it simpler to process.
• Preheating: Preheat S7 steel in two stages: first to around 500°C to 600°C (932°F to 1112°F), followed by 800°C to 850°C (1472°F to 1562°F) before quenching. This helps prevent cracking during the hardening process.
• Austenitizing: Heat S7 steel to 1000°C to 1050°C (1832°F to 1922°F) and hold for 30-60 minutes. This ensures a uniform austenitic structure, which is crucial for effective hardening.
• Hardening: Quench the steel rapidly in air or oil to reach a 55-60 HRC hardness. The rapid cooling locks the structure and enhances wear resistance, but care must be taken to avoid warping.
• Tempering: After hardening, temper the steel at 500°C to 600°C (932°F to 1112°F) for 2-3 hours to relieve residual stresses and balance hardness with toughness. This ensures the steel retains its strength while preventing brittleness.

Machining

S7 steel is relatively easy to machine due to its excellent hardness and toughness after heat treatment. However, special attention is required during cutting operations:

• Cutting: Utilize high-speed steel (HSS) or carbide tools to process S7. A consistent cutting speed should be maintained to avoid overheating, which can cause surface defects.
• Surface Treatment: To improve wear resistance, apply treatments like nitriding or PVD coating. Nitriding improves the surface hardness without affecting the core’s toughness, while PVD coatings offer additional protection against wear and corrosion.
• Cooling & Stress Relief: S7 steel may require stress relief cooling after machining or tempering. This is typically done in still air to minimize thermal stresses, ensuring the final part remains dimensionally stable and free from cracks.

This process ensures that S7 cold work steel retains its exceptional hardness, toughness, and performance characteristics for demanding applications.

Product We Provide for S7 Cold Work Steel

SteelPRO Group is a leading supplier of S7 tool steel materials. We provide a range of forms, including S7 round bars, flat bars, plates, rods, and custom sizes. Don’t hesitate to reach out for more details or a fast quote.

Available S7 Steel Forms & Specifications:

• S7 Steel Round Bar: Diameter from 10mm – 900mm
• S7 Steel Plate: Thickness from 5mm – 500mm, Width from 150mm – 2000mm
• S7 Steel Flat Bar: Thickness from 3mm – 150mm, Width from 50mm – 1500mm
• S7 Steel Rod:  Diameter from 10mm – 800mm, (custom lengths available upon request)
• S7 Steel Custom Sizes: Tailored to specific customer requirements

Additional Services:

• Surface Finish: Available in black, rough-machined, turned, or customized finishes
• Processing: We offer hot-rolling, forging, cold drawing, and other tailored processes to meet your specific needs

Applications of ASTM S7 Cold Work Tool Steel

S7 steel is designed for high-performance tools where durability and resistance to shock and wear are critical. It is commonly used in industries that demand durable, dependable tools capable of enduring high-stress conditions. Common applications include:

• Cutting Tools: Keyway cutting tools, slitting saws, broaches
• Molds: Injection molds for plastic, extrusion dies, cold forming dies
• Die Casting: Die casting dies for aluminum and zinc, forming dies
• Press Tools: Blanking dies, forming tools, trimming dies
• Mining Tools: Drill bits, drill rods, mining chisels
• Automotive: Wheel hub manufacturing tools, punching dies, camshaft dies
• Aerospace: Aerospace forging dies, turbine blade forming tools
• Construction: Rock crushing tools, concrete compaction tools

S7 is ideal for demanding environments where both toughness and wear resistance are essential for long tool life.

S7 Tool Steel Suppliers

SteelPRO Group offers S7 tool steel with a unique advantage—our ability to supply custom shapes and sizes with outstanding precision. We can also provide large-diameter S7 round bars and heavy-duty plates, up to 1000mm in diameter and 600mm in thickness, tailored to your specific needs. 

In addition, we offer a range of surface finishes, from rough-machined to polished, and value-added services like heat treatment and stress relief to improve the steel’s performance. With our dedication to quality and versatility, we guarantee you receive the precise material for your toughest applications.