Among various steel materials for CNC machining, S45C is a widely used carbon steel with good properties and machinability. This guide explores everything you should know about S45C steel, including its equivalent grades, chemical composition, mechanical and physical properties, corrosion resistance, and heat resistance. Additionally, we delve into its weldability, machinability, and heat treatment processes. We also provide detailed comparisons between S45C steel and other grades like SS400 and S50C
What Is S45C Material?
S45C is a medium-carbon steel grade under the JIS G4051 standard, designed for machine structural applications. It is known for its excellent balance of strength, toughness, and wear resistance. With a typical carbon content of 0.45%, S45C offers good machinability and heat treatability, making it a versatile material for a wide range of engineering and industrial applications. It is commonly used in the production of mechanical components like gears, shafts, and structural parts, as well as in industries such as automotive and aerospace.
S45C steel exhibits excellent mechanical properties, including a tensile strength of ≥600 MPa, yield strength of ≥355 MPa, and impact energy of ≥39 J. Its wear resistance can be further enhanced through heat treatment, such as quenching and tempering, making it suitable for applications that demand durability under high stress. Despite its moderate corrosion resistance, S45C remains a cost-effective and widely used material in manufacturing thanks to its favorable characteristics.
S45C Material Equivalent Chart
| Country/Region | Standard | Designation/Grade |
|---|---|---|
| USA | AISI/SAE | 1045 |
| Europe | EN | C45E |
| Germany | DIN | Ck45 |
| Japan | JIS | S45C |
| China | GB | 45# |
| International | ISO | 1045 |
S45C Steel Chemical Composition
| Element | Percentage Range (%) |
|---|---|
| Carbon (C) | 0.42 – 0.50 |
| Silicon (Si) | 0.15 – 0.40 |
| Manganese (Mn) | 0.60 – 0.90 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.030 |
S45C Steel Material Properties
| Category | Property | Condition | Value (Metric) | Value (Imperial) | Notes |
|---|---|---|---|---|---|
| Mechanical Properties | Tensile Strength | Annealed | 570 – 700 MPa | 83 – 102 ksi | – |
| Yield Strength | Annealed | 350 – 450 MPa | 51 – 65 ksi | – | |
| Elongation | Annealed | 16 – 20% | 16 – 20% | – | |
| Hardness (Brinell) | Annealed | 170 – 210 HB | 170 – 210 HB | – | |
| Impact Strength | Annealed | 27 J | 20 ft-lbf | – | |
| Physical Properties | Density | – | 7.85 g/cm³ | 0.284 lb/in³ | – |
| Melting Point | – | 1425 – 1540 °C | 2600 – 2800 °F | – | |
| Thermal Conductivity | – | 50 W/m·K | 34.5 BTU·in/h·ft²·°F | – | |
| Specific Heat Capacity | – | 0.49 kJ/kg·K | 0.12 BTU/lb·°F | – | |
| Electrical Resistivity | – | 0.0000017 Ω·m | 0.0000017 Ω·in | – | |
| Corrosion Resistance | Atmospheric | – | Fair | – | Susceptible to rust |
| Chlorides (3-5%) | – | Poor | – | Risk of pitting corrosion | |
| Acids | – | Poor | – | Not recommended for acidic environments | |
| Alkalis | – | Fair | – | Limited resistance | |
| Heat Resistance | Max Continuous Temp | – | 400°C | 752°F | Moderate temperature exposure |
| Max Intermittent Temp | – | 500°C | 932°F | Short-term exposure only | |
| Scaling Temperature | – | 600°C | 1112°F | Risk of oxidation beyond this limit |
Is S45C Weldable?
Yes, S45C steel is weldable, but it requires certain precautions. Due to its medium-carbon content, preheating is recommended to reduce the risk of cracking during welding, especially for thicker sections. Post-weld heat treatment may also be necessary to relieve stresses and improve toughness. Common welding techniques such as MIG, TIG, and stick welding can be used, with appropriate filler metals like ER70S-6 or E7018.
S45C Steel Machinability
S45C steel offers good machinability, with a relative machinability index of around 60% compared to AISI 1212 (100%). It can be easily machined using conventional techniques, though optimal cutting speeds and tooling are essential for achieving the best results. While it is not as easily machinable as free-machining steels, S45C remains a popular choice for manufacturing components with intricate designs.
S45C Steel Heat Treatment Process
S45C steel is highly responsive to heat treatment, which allows for significant improvement in its mechanical properties. Common heat treatment processes include:
- Annealing: Heating the steel to 600–700°C (1112–1292°F), followed by slow cooling, softens the material and improves ductility.
- Quenching: Heating to 800–850°C (1472–1562°F), soaking, and then rapidly cooling in oil or water increases hardness and strength.
- Tempering: Reheating the quenched steel to 200–600°C (392–1112°F) and cooling in air reduces brittleness while improving toughness and ductility.
S45C vs SS400 vs S50C Steel Differences
| Property | S45C | SS400 | S50C |
|---|---|---|---|
| Classification | Medium-carbon steel for machine structural use | Low-carbon structural steel | Medium-carbon steel for machine structural use |
| Applications | Gears, shafts, mechanical parts | Building frames, bridges, general construction | Shafts, gears, rollers, pins, machinery parts |
| Weldability | Good with preheating | Excellent | Good with preheating |
| Machinability | Good | Excellent | Good |
| Corrosion Resistance | Fair (requires coating) | Fair (requires coating) | Fair (requires coating) |
| Element | S45C | SS400 | S50C |
|---|---|---|---|
| Carbon (C) | 0.42 – 0.50 | ≤ 0.17 (≤16mm), ≤ 0.20 (>16mm) | 0.47 – 0.55 |
| Silicon (Si) | 0.15 – 0.40 | – | 0.15 – 0.35 |
| Manganese (Mn) | 0.60 – 0.90 | ≤ 1.60 | 0.60 – 0.90 |
| Phosphorus (P) | ≤ 0.030 | ≤ 0.050 | ≤ 0.030 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.050 | ≤ 0.035 |
| Property | S45C | SS400 | S50C |
|---|---|---|---|
| Tensile Strength (MPa) | 600 – 700 | 400 – 510 | 630 – 700 |
| Yield Strength (MPa) | 350 – 450 | 245 – 235 (depending on thickness) | 375 – 450 |
| Elongation (%) | 16 – 20 | 17 – 23 (depending on thickness) | 14 – 20 |
| Hardness (HB) | 170 – 210 | 179 – 235 | 170 – 235 |
| Impact Energy (J) | ≥ 39 | NA | ≥ 39 |
| Property | S45C | SS400 | S50C |
|---|---|---|---|
| Annealing Temperature (°C) | 600 – 700 | Not Applicable | 700 – 800 |
| Quenching Temperature (°C) | 800 – 850 | Not Applicable | 810 – 860 |
| Tempering Temperature (°C) | 200 – 600 | Not Applicable | 400 – 600 |
| Hardness after Quenching (HRC) | 54 – 60 | Not Applicable | 16 – 29 |