4120 Alloy Steel
Pennsylvania Steel Corporation offers an alternative to AISI 4120 alloy steel.
We produce FLEXOR® steel to provide similar, if not superior, chemical and mechanical properties to 4120 alloy steel. These properties allow FLEXOR® steel to be used effectively for applications that require an excellent strength to weight ratio coupled with high strength, hardness and wear resistance as an alternative to 4120 steel. These include Structural Tubing, Frames, Gears, Piston Pins, Crankshafts, Clutch and Flywheel Components used as Aircraft, Aerospace and Automotive Components.
Being a proprietary grade, Pennsylvania Steel ensures that all FLEXOR® heats meet a high quality vacuum degas electric arc furnace melt process in order to ensure cleanliness, grain refinement and maximum reduction ratios.

SAE 4120 Steel Chemistry Composition vs. FLEXOR®
Alloys | 4120 | FLEXOR® |
---|---|---|
Carbon (C) | .18 - .23 | .32 - .36 |
Manganese (Mn) | .40 - .60 | .60 - .80 |
Phosphorous (P) | .035 (max) | .025 (max) |
Sulfur (S) | .04 (max) | .025 (max) |
Silicon (Si) | .15 - .35 | .15 - .30 |
Chromium (Cr) | .80 - 1.10 | .75 - 1.00 |
Molybdenum (Mo) | .15 - .25 | .40 - .60 |
Tungsten (W) | - | .40 - .70 |
Typical FLEXOR® Mechanical Properties (Based upon 1.00" dia.)
Mechanical Properties | UTS (ksi) Per ASTM E8-04 | YS 0.2% offset Per ASTM E8-04 | V-Notch Charpy Impact Per ASTM E23-06 | RA% Per ASTM E8-04 | Elongation Per ASTM E8-04 | Poisson's Ratio per ASTM E111-04 | Young Modulus per ASTM E111 |
---|---|---|---|---|---|---|---|
30 HRC | 147 | 147 | 80 | 64 | 21 | N/A | N/A |
40 HRC | 183 | 183 | 45 | 60 | 18 | .282 | 30900 (ksi) |
45 HRC | 225 | 225 | 21 | 50 | 12 | N/A | N/A |
Contact Pennsylvania Steel Corporation today to learn more about FLEXOR® and its advantages over 4120 alloy steel.
FLEXOR® Properties
FLEXOR®'s dependable quality and adaptability in heat treatment allows for a wide range of physical properties that are more appealing than those of typical ASTM, AISI or SAE 4120 alloy steel.
FLEXOR® has a higher core hardness, resulting in a more uniform hardness through any cross section. The more uniform hardness and a fine grain microstructure produce a steel that is low weight with high fatigue and tensile strength and is an excellent material for applications that require a lighter weight component with the strength of steel.
FLEXOR® Sizes & Conditions
FLEXOR® steel is available in a variety of sizes and conditions. These include, but are not limited to:
- Decarb free alloys
- Hot rolled rounds
- Peeled steel bars
- Ground and polished rounds
- Hot rolled flats
- Hot rolled plates
- Turned forged round and billet
Testimonials
"At Powerhold we use FLEXOR® exclusively on all our special design work-holding Diaphragms. The performance and machining quality of FLEXOR® is superior to anything we have utilized in the past.
Today’s customer demands a quality product that performs consistently...FLEXOR® enables us to meet that goal every day."
Testimonials
"Just wanted to take a minute to say thanks. I always receive my orders on time and without any complications. I appreciate you keeping me so up to date on the order process through email, and the way the steel is cut and packaged so carefully. Using your Product (FLEXOR®) has increased standard tool life by as much as 25%-30%. Thank you again for all you hard work. I look forward to business with you again and again, it's always a pleasure!"
Testimonials
"Pennyslvania Steel Corporation has been a valued supplier for our company going on two decades. FLEXOR®'S versatility and reliability have been extremely helpful to the products we manufacture. Due to to FLEXOR®'S versatility at various hardness' we are able to use it at 28-32 HRC, 28-32 HRC and nitrided, or through hardened anywhere between 42 and 50 HRC. In our experience FLEXOR® has superior machinability to other comparable steel grades especially in higher hardness'. We machine FLEXOR® at 40 HRC and find this to be a key benefit to our manufacturing process."