Overview
S7 Tool Steel is a shock-resistant air-hardening tool steel specifically designed for applications requiring exceptional toughness, impact resistance, fatigue strength, and moderate wear resistance. As one of the most popular steels in the AISI S-series, S7 excels in tooling applications exposed to repeated impact, shock loading, and cyclic stresses.
Unlike D2 or D3 tool steels that prioritize wear resistance, S7 focuses on toughness and durability under impact conditions. It is widely used in punches, chisels, shear blades, plastic molds, and heavy-duty tooling.
S7 is widely used in:
- Pneumatic Tools
- Jackhammer Bits
- Cold Chisels
- Punches
- Shear Blades
- Plastic Mold Components
- Die Casting Tooling
- Impact Tools
Because of its outstanding toughness and reliability, S7 is one of the most commonly used shock-resistant tool steels worldwide.
Material Specification
| Property | Value |
|---|---|
| Material Designation | S7 Tool Steel |
| Standard | ASTM A681 |
| UNS Number | T41907 |
| Material Family | Shock-Resisting Tool Steel |
| Density | 7.85 g/cm³ |
| Magnetic Property | Magnetic |
| Typical Supply Condition | Annealed |
| Standard Forms | Round Bar, Flat Bar, Plate, Block, Tooling Stock |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Carbon (C) | 0.45–0.55 |
| Chromium (Cr) | 3.00–3.50 |
| Molybdenum (Mo) | 1.30–1.80 |
| Silicon (Si) | 0.20–1.00 |
| Manganese (Mn) | 0.20–0.80 |
| Vanadium (V) | 0.20–0.35 |
| Phosphorus (P) | ≤0.030 |
| Sulfur (S) | ≤0.030 |
The chromium and molybdenum content enhance hardenability and toughness, while vanadium improves grain refinement and fatigue resistance.
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 800–1000 MPa |
| Yield Strength | 550–750 MPa |
| Hardness | 200–240 HB |
| Elastic Modulus | 210 GPa |
Hardened & Tempered Condition
| Property | Value |
|---|---|
| Hardness | 54–58 HRC |
| Impact Resistance | Outstanding |
| Toughness | Exceptional |
| Fatigue Strength | Excellent |
Shock-Resistant Condition
| Property | Value |
|---|---|
| Hardness | 56–58 HRC |
| Chipping Resistance | Excellent |
| Crack Resistance | Excellent |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1400–1450°C |
| Thermal Conductivity | 28 W/m·K |
| Electrical Resistivity | 0.55 μΩ·m |
| Thermal Expansion Coefficient | 11.5 × 10⁻⁶/K |
| Specific Heat Capacity | 460 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Indoor Environment | Moderate |
| Dry Atmosphere | Good |
| Humid Environment | Moderate |
| Outdoor Environment | Moderate |
| Marine Environment | Poor |
| Chemical Environment | Poor |
S7 is not a stainless steel and should be protected in corrosive environments.
Recommended surface treatments:
- Black Oxide
- QPQ Treatment
- Nitriding
- Hard Chrome Plating
- PVD Coating
- Nickel Plating
Weldability
| Welding Process | Rating |
|---|---|
| TIG Welding | Good |
| MIG Welding | Good |
| Arc Welding | Good |
| Laser Repair Welding | Excellent |
| Tool Steel Repair Welding | Excellent |
Compared with most tool steels, S7 offers relatively good weldability.
Recommended:
- Preheating
- Controlled Cooling
- Post-Weld Tempering
Machinability
| Process | Rating |
|---|---|
| CNC Turning | Good |
| CNC Milling | Good |
| Drilling | Good |
| Grinding | Excellent |
| EDM Machining | Excellent |
| Wire EDM | Excellent |
Machinability Comparison
| Material | Machinability |
|---|---|
| O1 Tool Steel | Excellent |
| A2 Tool Steel | Good |
| S7 Tool Steel | Good |
| D2 Tool Steel | Fair |
| D3 Tool Steel | Fair |
S7 offers better machinability than many high-alloy tool steels.
Heat Treatment
Annealing
| Parameter | Value |
|---|---|
| Temperature | 840–870°C |
| Cooling Method | Furnace Cool |
Preheating
| Parameter | Value |
|---|---|
| Temperature | 650–760°C |
Hardening
| Parameter | Value |
|---|---|
| Temperature | 925–955°C |
| Cooling Medium | Air |
Tempering
| Parameter | Value |
|---|---|
| Temperature | 200–540°C |
| Cycles | Double Temper Recommended |
Hardness After Heat Treatment
| Condition | Hardness |
|---|---|
| Annealed | 200–240 HB |
| Hardened | 58–60 HRC |
| Hardened & Tempered | 54–58 HRC |
Nitriding
| Property | Value |
|---|---|
| Surface Hardness | 65–72 HRC |
| Wear Resistance | Excellent |
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | S7 |
| UNS | T41907 |
| GB/T (China) | 5Cr3Mn1SiMo1V |
| EN (Europe) | 50CrMoV13-1 |
| DIN (Germany) | 1.2355 |
| JIS (Japan) | Similar Performance Grade |
| ISO | 50CrMoV13-1 |
Available Forms
| Product Type | Availability |
|---|---|
| Round Bar | Yes |
| Flat Bar | Yes |
| Tool Steel Plate | Yes |
| Precision Ground Plate | Yes |
| Mold Blocks | Yes |
| Tooling Stock | Yes |
| Forgings | Yes |
Typical Applications
Impact Tool Industry
- Pneumatic Chisels
- Jackhammer Bits
- Impact Punches
- Riveting Tools
Tool & Die Industry
- Heavy-Duty Punches
- Shear Blades
- Trimming Dies
- Forming Dies
Plastic Mold Industry
- Mold Cavities
- Core Inserts
- Large Mold Components
Die Casting Industry
- Trim Dies
- Ejector Components
- Impact-Loaded Tooling
Forging Industry
- Forging Dies
- Hammer Tooling
- Impact Tools
General Engineering
- High-Impact Wear Parts
- Structural Tooling Components
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| CNC Machining | Excellent |
| Precision Grinding | Outstanding |
| EDM Machining | Excellent |
| Wire EDM | Excellent |
| Heat Treatment | Outstanding |
| Nitriding | Excellent |
| Welding Repair | Excellent |
Advantages
Exceptional Toughness
One of the toughest tool steels available.
Outstanding Shock Resistance
Designed specifically for impact loading.
Excellent Fatigue Strength
Suitable for repeated cyclic loading.
Good Wear Resistance
Provides a balance between toughness and wear performance.
Good Weldability
Easier to repair than D-series tool steels.
Air Hardening
Reduces distortion during heat treatment.
Limitations
Lower Wear Resistance Than D2 or D3
Not ideal for severe abrasive wear applications.
Moderate Corrosion Resistance
Requires protective coatings.
Lower Hardness Than High-Chromium Tool Steels
Prioritizes toughness over maximum hardness.
Higher Cost Than Carbon Tool Steels
Due to alloy content.
Comparison with Other Tool Steels
| Property | S7 | A2 | D2 | D3 | O1 |
|---|---|---|---|---|---|
| Toughness | Exceptional | Excellent | Moderate | Lower | Good |
| Wear Resistance | Good | Excellent | Outstanding | Exceptional | Good |
| Hardness | 58 HRC | 62 HRC | 62 HRC | 64 HRC | 62 HRC |
| Shock Resistance | Outstanding | Good | Moderate | Low | Good |
| Weldability | Good | Fair | Poor | Poor | Poor |
Comparison with Engineering Materials
| Material | Hardness Potential | Toughness | Shock Resistance |
|---|---|---|---|
| S7 Tool Steel | 58 HRC | Exceptional | Outstanding |
| A2 Tool Steel | 62 HRC | Excellent | Good |
| D2 Tool Steel | 62 HRC | Moderate | Moderate |
| D3 Tool Steel | 64 HRC | Lower | Low |
| O1 Tool Steel | 62 HRC | Good | Good |
| 4140 Steel | 58 HRC | Excellent | Excellent |
Available Surface Finishes
Raw Finishes
- Annealed Finish
- Ground Finish
- Precision Machined Finish
Functional Finishes
- Hardened Finish
- Nitrided Finish
- Precision Ground Finish
- EDM Finish
Protective Finishes
- Black Oxide
- QPQ Treatment
- Nickel Plating
- Hard Chrome Plating
- PVD Coating
Frequently Asked Questions (FAQ)
What is S7 tool steel?
S7 is a shock-resistant air-hardening tool steel designed for applications requiring exceptional toughness and impact resistance.
What is S7 steel used for?
Typical applications include:
- Pneumatic Tools
- Punches
- Chisels
- Shear Blades
- Plastic Molds
- Die Casting Tooling
What is the equivalent material to S7?
Common equivalents include:
- DIN 1.2355
- 50CrMoV13-1
- 5Cr3Mn1SiMo1V
What is the difference between S7 and D2?
| Property | S7 | D2 |
|---|---|---|
| Toughness | Much Higher | Lower |
| Wear Resistance | Lower | Higher |
| Shock Resistance | Outstanding | Moderate |
| Chipping Resistance | Better | Lower |
What hardness can S7 achieve?
Typically:
- Hardened: 58–60 HRC
- Hardened & Tempered: 54–58 HRC
Is S7 suitable for punches?
Yes. S7 is one of the most commonly used materials for impact punches and heavy-duty tooling.
Can S7 be welded?
Yes. S7 has better weldability than most tool steels and is often repaired by welding.
Why is S7 used for impact tools?
Because it combines:
- Exceptional Toughness
- High Shock Resistance
- Good Fatigue Strength
- Good Wear Resistance
- Reliable Heat Treatment Performance
Is S7 suitable for plastic molds?
Yes. S7 is widely used for large plastic molds requiring toughness and durability.
Does GCNOV provide custom manufacturing services for S7 steel?
Yes. GCNOV provides:
- CNC Machining
- Tool & Die Manufacturing
- EDM Processing
- Precision Grinding
- Heat Treatment
- Nitriding
- QPQ Treatment
- Prototype Development
- Low-Volume Production
- Mass Production