303 Stainless Steel Plate – High Machinability Corrosion-Resistant Alloy
Sandmeyer Steel offers Alloy 303 in thicknesses from 3/16″ (4.8mm) through 2” (50.8mm).
Available thicknesses for Alloy 303:
| 3/16'' | 1/4'' | 3/8'' | 7/16'' | 1/2'' | 9/16'' | 5/8'' | 3/4'' |
| 4.8mm | 6.3mm | 9.5mm | 11.1mm | 12.7mm | 14.3mm | 15.9mm | 19mm |
| 7/8" | 1" | 1 1/8" | 1 1/4" | 1 1/2" | 1 3/4" | 2" | |
| 22.2mm | 25.4mm | 28.6mm | 31.8mm | 38.1mm | 44.5mm | 50.8mm |
Alloy 303 (UNS S30300) is a non-magnetic, austenitic, free-machining stainless steel that is a modification of the basic 10% chromium -8% nickel stainless steel specially designed to exhibit improved machinability while maintaining good mechanical and corrosion-resistant properties.
Specification Sheet Overview
for Alloy 303 (UNS S30300)
W. Nr. 1.4305:
General Properties
Alloy 303 (UNS S30300) is an austenitic stainless steel developed for applications requiring extensive machining operations. The alloy has a sulfur addition which assists in breaking up turnings while reducing drag on the cutting tool when compared to the machining characteristics of the conventional 18-8 stainless steels.
The alloy is nonmagnetic in the annealed condition , but may become slightly magnetic as a result of cold working. The addition of sulfur negatively impacts the corrosion resistance of 303 making it less resistant than 304 to mildly corrosive environments.
Corrosion Resistance
Alloy 303 is resistant to mildly corrosive environments. However, the alloy’s corrosion resistance is inferior to 304 in most applications. Its corrosion resistance is superior to 416, another free-machining grade, but is somewhat inferior to other 400 series stainless steels which do not contain higher sulfur levels. In order to obtain optimal corrosion resistance, it is recommended that Alloy 303 be chemically treated to remove sulfides from the final surfaces.
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise indicated)
| Chromium | 17.0 min.-19.0 max. | Sulfer | 0.15-0.35 |
| Nickel | 8.0 min.-10.0 max. | Silicon | 1.00 |
| Carbon | 0.10 | Copper | 1.00 |
| Manganese | 2.00 | Nickel | 0.110 |
| Phosphorus | 0.20 | Iron | Balance |
Density
0.285 lbs/in3
7.89 g/cm3
Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)
Modulus of Elasticity
28.0 x 106 psi
193 GPa
Thermal Conductivity 212°F (100°C)
112 BTU/hr/ft2/ft/°F
16.2 W/m-°K
Melting Range
2500 – 2590°F
1480 – 1530°C
Electrical Resistivity
28.3 Microhm-in at 68°C
72.0 Microhm-cm at 20°C
Fabrication Data
Heat Treatment
Annealing – Heat to a minimum temperature of 1900°F (1038°C) and water quench or rapid cool by other means.
Hardening – Alloy 303 cannot be hardened by thermal treatment, it can only be hardened by cold working.
Cold Forming
The cold formability of Alloy 303 is adversely impacted by the high sulfur content. The alloy may be bent with a generous bend radius, however, when cold forming is required, 304 should be utilized.
Hot Forming
The high sulfur content of Alloy 303 also has a detrimental impact on hot workability. If hot forming is required, once again, 304 should be considered as an alternate selection.
Machining
Alloy 303 was developed specifically for ease of machining. The sulfur addition assists in breaking up turnings which reduces drag on the cutting tool. It produces small brittle chips and may be machined at high speeds with deep cuts and heavy feeds.
The table below suggests speeds and feeds for various machining operations for 303.
Diameter of Tool |
|||||
|---|---|---|---|---|---|
(sfm) | (in./rev.) | (sfm) | (in./rev.) | (dia./in.) |
|
| 115 135 | 0.0150 0.0050 | 375 600 | 0.025 0.007 | 0.005-0.200 0.002-0.004 |
|
| 90 100 | 0.0015 0.0025 | 275 325 | 0.002 0.004 | 1/16 1/4 |
|
| 100 100 | 0.0020 0.0015 | 375 350 | 0.003 0.002 | 1 2 |
|
| 70 85 100 | 0.0060 0.0100 0.0200 | — 700 800 | — 0.005 0.007 | 1/4 1/2 1-2 |
|
| 90 90 | 0.0050 0.0150 | — — | — — | 1/4 1-2 |
|
| 130 130 | 0.0030 0.0060 | 300 350 | 0.004 0.009 | 1/2 1-2 |
|
| 10 40 | — — | — — | — — | 7 threads/in. 25 theads/in. |
|
Welding
Alloy 303 is not recommended for applications requiring welding. If it is necessary to weld the alloy, AWS E312 filler metal may be considered.
Alloy 303 Stainless Steel – Frequently Asked Questions
1. What is Alloy 303 stainless steel?
Alloy 303 (UNS S30300) is a free-machining austenitic stainless steel specifically designed for improved machinability. The alloy is nonmagnetic in the annealed condition, but may become slightly magnetic as a result of cold working.
2. What are common applications for Alloy 303 stainless steel plate?
Alloy 303 is commonly used for parts requiring extensive machining, including:
• Valve components
• Shafts and gears
• Fasteners
• Bushings
• Instrumentation fittings
• High-speed machined parts
3. How does Alloy 303 compare to Alloy 304 in corrosion resistance?
While Alloy 303 offers similar general corrosion resistance to 304, the addition of sulfur slightly reduces its performance in highly corrosive environments. It is best used in applications where machinability is the top priority and where exposure to aggressive chemicals is limited.
4. Can Alloy 303 be welded?
Welding is not recommended for Alloy 303 due to its sulfur content, which can cause hot cracking and decreased weld quality. If welding is required, post-weld cleaning and heat treatment are critical. For better weldability, consider using Alloy 304 or 304L.
5. Is Alloy 303 magnetic?
No. Alloy 303 is non-magnetic in the annealed condition. However, it may become slightly magnetic after cold working or machining.
6. What are the mechanical properties of Alloy 303 stainless steel?
Typical values at 68°F (20°C):
• Yield Strength (0.2% offset): 45,000 psi (310 MPa)
• Ultimate Tensile Strength: 85,000 psi (586 MPa)
• Elongation in 2″: 50%
• Hardness: 202 (HBN)
7. What are the physical properties of Alloy 303?
• Density: 0.285 lbs/in³ (7.90 g/cm³)
• Modulus of Elasticity: 28.0 × 10⁶ psi (193 GPa)
• Thermal Conductivity: 112 BTU/hr/ft²/ft/°F 16.2 W/m-°K
• Specific Heat: 0.12 BTU/lb-°F 502 J/kg-°K (0 – 100°C)
• Electrical Resistivity: 28.3 Microhm-in at 68°C 72.0 Microhm-cm at 20°C
8. What standards apply to Alloy 303 stainless steel?
• ASTM A895
9. What thicknesses of Alloy 303 stainless steel plate does Sandmeyer Steel stock?
Sandmeyer Steel stocks Alloy 303 stainless steel plate in thicknesses ranging from 3/16″ (4.8 mm) through 2″ (50.8 mm). Additional sizes and custom-cut shapes are available upon request.