As a Sales and Marketing Manager at Wisense Factory, I often get questions from customers about 303 stainless steel—its properties, applications, and why it’s such a popular choice for machining. Whether you’re an engineer, a manufacturer, or a procurement specialist, understanding the key characteristics of 303 stainless steel can help you make better material decisions.
In this blog, I’ll break down everything you need to know about 303 stainless steel, including its composition, density, hardness, yield strength, price, available bar diameters, magnetic properties, and machining advantages. Let’s dive in!
- 1. 303 Stainless Steel Composition
- 2. 303 Stainless Steel Density
- 3. 303 Stainless Steel Hardness
- 4. 303 Stainless Steel Yield Strength
- 5. 303 Stainless Steel Price
- 6. 303 Stainless Steel Bar Diameter Availability
- 7. Is 303 Stainless Steel Magnetic?
- 8. 303 Stainless Steel Machining: Why It’s the Best Choice
- 9. Final Thoughts
1. 303 Stainless Steel Composition
303 stainless steel is a free-machining variant of 304 stainless steel, modified with sulfur (and sometimes selenium) to improve machinability. Here’s a typical chemical composition:
| Element | Percentage (%) |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 17.00 – 19.00 |
| Nickel (Ni) | 8.00 – 10.00 |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.20 |
| Sulfur (S) | ≥ 0.15 |
| Carbon (C) | ≤ 0.15 |
The added sulfur reduces tool wear during machining, making 303 stainless steel ideal for high-speed operations. However, this also slightly reduces corrosion resistance compared to 304.
2. 303 Stainless Steel Density
Density is a crucial factor when calculating weight for fabrication or shipping. The density of 303 stainless steel is 7.9 g/cm³ (0.285 lb/in³), the same as most austenitic stainless steels like 304 and 316.
This means:
- A 1-meter round bar with a 50mm diameter weighs approximately 15.5 kg.
- A 1-foot round bar with a 2-inch diameter weighs roughly 4.3 lbs.
If you need precise weight calculations for your project, feel free to reach out—we can provide exact numbers based on your dimensions.
3. 303 Stainless Steel Hardness
Hardness determines wear resistance and machinability. 303 stainless steel typically has:
- Brinell Hardness (HB): 190 – 220
- Rockwell Hardness (B Scale): 85 – 95
This moderate hardness makes it easier to machine than harder stainless grades while still maintaining good mechanical strength.
4. 303 Stainless Steel Yield Strength
Yield strength is the stress at which a material begins to deform permanently. For 303 stainless steel:
- Yield Strength (0.2% offset): 240 MPa (35,000 psi)
- Tensile Strength: 550 MPa (80,000 psi)
- Elongation at Break: 40-50%
While not as strong as some martensitic or precipitation-hardening grades, 303 stainless steel offers excellent machinability and good corrosion resistance, making it a top choice for fasteners, fittings, and shafts.
5. 303 Stainless Steel Price
The price of 303 stainless steel fluctuates based on:
- Raw material costs (nickel & chromium markets)
- Order quantity (bulk discounts available)
- Form (round bars, hex bars, etc.)
As of 2025, expect prices in the range of:
- $3.50 – $5.50 per kg for standard round bars
- Higher for precision-ground or special diameters
At Wisense Factory, we have stable material suppliers and flexible MOQs—contact us for a quote tailored to your machining needs.
6. 303 Stainless Steel Bar Diameter Availability
We stock 303 stainless steel bars in various diameters to meet different machining needs:
| Diameter (mm) | Diameter (inches) | Common Applications |
|---|---|---|
| 5 – 20 mm | 0.2″ – 0.8″ | Small shafts, pins, fasteners |
| 20 – 50 mm | 0.8″ – 2″ | Valve components, bushings |
| 50 – 100 mm | 2″ – 4″ | Larger machined parts, gears |
| 100+ mm | 4″+ | Industrial fittings, custom machining |
For diameters 5 – 20 mm round bar, it is the most often used materials in our machining shop.We have 60 units Swiss type CNC lathes, it is best for machining the SS bar material at diameter less than 20 mm.
7. Is 303 Stainless Steel Magnetic?
Unlike ferritic or martensitic stainless steels (like 430 or 410), 303 stainless steel is generally non-magnetic in its annealed state. However:
- Cold working (machining, bending) can induce slight magnetism.
- It will not attract a magnet as strongly as 400-series stainless steels.
If magnetism is a concern for your application, let’s discuss alternative grades.
8. 303 Stainless Steel Machining: Why It’s the Best Choice
303 stainless steel is the go-to grade for machining because:
✔ Excellent Chip Breaking – Sulfur content promotes short chips, reducing tool clogging.
✔ High Cutting Speeds – Allows faster machining than 304 or 316.
✔ Good Surface Finish – Ideal for precision parts like screws, nuts, and fittings.
Best Machining Practices:
- Use sharp carbide tools for best results.
- Apply coolant to prevent work hardening.
- Avoid excessive feed rates to minimize burring.
At Wisense Factory, we have more than 200 units different type CNC machines—ensuring smooth production runs and minimal tool wear. If you need 303 stainless steel CNC machining services, Wisense is a good choice.
9. Final Thoughts
303 stainless steel is a versatile, machinable, and corrosion-resistant material perfect for CNC machining, automatic screw machines, and precision components. While it sacrifices a bit of corrosion resistance compared to 304, its ease of machining makes it a favorite in industries like:
- Automotive (fittings, shafts)
- Aerospace (fasteners, bushings)
- Medical (surgical instruments)
- General machining (nuts, bolts, gears)
If you’re looking for reliable 303 stainless steel machining suppliers, Wisense Factory offers high-quality parts at competitive prices. Contact us today for a quote or technical support!
