What is the difference between 17-4 PH and 304 stainless steel?
Stainless steel comes in many different grades, each with unique properties that make them ideal for specific applications. Two common grades are 17-4 PH and 304 stainless steel. While both offer excellent corrosion resistance, they have key differences in strength, hardness, and best uses. Here at Dynamic Metals, we dig deeper below using our expertise into the key differences between 17-4ph and 304.
What is 304 stainless steel?
304 is the most widely used austenitic stainless steel. It has a minimum of 18% chromium and 8% nickel, combined with a max of 0.08% carbon. This mix makes it:
- Very corrosion resistant
- Highly formable and ductile
- Easy to weld
- Non-magnetic
You'll find 304 used in a huge range of applications like food processing equipment, kitchen benchtops, sinks, architectural facades, medical devices, and more. It provides great all-round performance at a reasonable cost.
What about 17-4 PH stainless steel?
17-4 PH is a precipitation hardening martensitic stainless steel. The chemical composition includes:
- 15-17.5% chromium
- 3-5% copper
- 3-5% nickel
- Up to 1% manganese
- Under 0.07% carbon
The big advantage of 17-4 PH is that it can be heat treated after machining to drastically increase its strength and hardness. The "PH" refers to the precipitation hardening process. In its strongest "condition H900" heat treatment, 17-4 PH provides:
- Tensile strength up to 190,000 psi (1,310 MPa)
- Hardness up to 44 HRC
- Great corrosion resistance
- Useful magnetic properties
17-4 PH is ideal for high-strength, corrosion-resistant applications like aerospace components, chemical and petrochemical processing, food processing blades and wear surfaces, oil and gas parts, and injection moulding.
304 vs 17-4 PH: Key differences
Therefore, how do you choose between 304 and 17 4 PH based on your requirements? Here are some key differences we've outlined for you below: -
Strength and hardness: The largest difference is that 17-4 PH can be heat treated to 44 HRC / 190 KSI tensile strength, whereas 304 is about 88 HRB (much softer than 17-4) and 75 KSI tensile in an annealed condition. 17-4 PH is the clear choice for high strength parts.
Corrosion resistance: 304 supplies good corrosion resistance, however 17-4 PH has the edge slightly – particularly in acidic and salty environments, 17-4 PH is vulnerable to stress corrosion cracking in chloride environments when hardened.
Machinability: Due to increased ductility, 304 is easier to machine than 17-4 PH which tends to harden quickly.
Weldability: 17-4 PH is readily weldable by common methods in annealed condition but requires post weld heat treatment to maintain strength.
Cost: Generally, 304 tends to be less expensive than 17-4 PH.
In conclusion, both 304 and 17-4 PH stainless steels have their strengths. 304 has excellent corrosion resistance and formability at a good price, so it’s very versatile for most applications. 17-4 PH has the highest hardness and strength in the heat-treated condition - it’s about 3 times stronger on tensile strength than 304 – which is why it’s perfect for high performance parts. To put it simply, the best for you depends upon your own needs.
We are stainless steel experts with over 15 years’ experience supplying 304 and 17-4ph here at Dynamic Metals. Contact us to talk to our knowledgeable team about your requirements if you need assistance in choosing the right grade for your next project.